![Pelvis RG MR CT3d front 01](https://upload.wikimedia.org/wikipedia/commons/b/b7/Pelvis_RG_MR_CT3d_front_01.jpg)
The pelvis (plural pelves or pelvises) is the lower part of the
trunk
Trunk may refer to:
Biology
* Trunk (anatomy), synonym for torso
* Trunk (botany), a tree's central superstructure
* Trunk of corpus callosum, in neuroanatomy
* Elephant trunk, the proboscis of an elephant
Computing
* Trunk (software), in rev ...
, between the
abdomen
The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...
and the
thigh
In human anatomy, the thigh is the area between the hip (pelvis) and the knee. Anatomically, it is part of the lower limb.
The single bone in the thigh is called the femur. This bone is very thick and strong (due to the high proportion of bone ...
s (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton).
The pelvic region of the trunk includes the bony pelvis, the
pelvic cavity (the space enclosed by the bony pelvis), the
pelvic floor
The pelvic floor or pelvic diaphragm is composed of muscle fibers of the levator ani, the coccygeus muscle, and associated connective tissue which span the area underneath the pelvis. The pelvic diaphragm is a muscular partition formed by the lev ...
, below the pelvic cavity, and the
perineum, below the pelvic floor. The pelvic skeleton is formed in the area of the back, by the
sacrum
The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30.
The sacrum situates at the upper, back part ...
and the
coccyx and anteriorly and to the left and right sides, by a pair of
hip bones.
The two hip bones connect the spine with the lower limbs. They are attached to the sacrum posteriorly, connected to each other anteriorly, and joined with the two femurs at the
hip joints. The gap enclosed by the bony pelvis, called the pelvic cavity, is the section of the body underneath the abdomen and mainly consists of the
reproductive organs (sex organs) and the
rectum
The rectum is the final straight portion of the large intestine in humans and some other mammals, and the Gastrointestinal tract, gut in others. The adult human rectum is about long, and begins at the rectosigmoid junction (the end of the s ...
, while the pelvic floor at the base of the cavity assists in supporting the organs of the abdomen.
In mammals, the bony pelvis has a gap in the middle, significantly larger in females than in males. Their
young pass through this gap when they are born.
Structure
The pelvic region of the trunk is the lower part of the
trunk
Trunk may refer to:
Biology
* Trunk (anatomy), synonym for torso
* Trunk (botany), a tree's central superstructure
* Trunk of corpus callosum, in neuroanatomy
* Elephant trunk, the proboscis of an elephant
Computing
* Trunk (software), in rev ...
, between the
abdomen
The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...
and the
thigh
In human anatomy, the thigh is the area between the hip (pelvis) and the knee. Anatomically, it is part of the lower limb.
The single bone in the thigh is called the femur. This bone is very thick and strong (due to the high proportion of bone ...
s. It includes several structures: the bony pelvis, the pelvic cavity, the pelvic floor, and the perineum. The bony pelvis (pelvic skeleton) is the part of the skeleton embedded in the pelvic region of the trunk. It is subdivided into the pelvic girdle and the pelvic spine. The pelvic girdle is composed of the
appendicular hip bones (
ilium,
, and
pubis) oriented in a ring, and connects the pelvic region of the spine to the lower limbs. The pelvic spine consists of the
sacrum
The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30.
The sacrum situates at the upper, back part ...
and
coccyx.
* the
pelvic cavity, typically defined as a small part of the space enclosed by the bony pelvis, delimited by the
pelvic brim
The pelvic brim is the edge of the pelvic inlet. It is an approximately Mickey Mouse head-shaped line passing through the prominence of the sacrum, the arcuate and pectineal lines, and the upper margin of the pubic symphysis.
Structure
The pel ...
above and the
pelvic floor
The pelvic floor or pelvic diaphragm is composed of muscle fibers of the levator ani, the coccygeus muscle, and associated connective tissue which span the area underneath the pelvis. The pelvic diaphragm is a muscular partition formed by the lev ...
below; alternatively, the pelvic cavity is sometimes also defined as the whole space enclosed by the pelvic skeleton, subdivided into:
** the
greater (or false) pelvis, above the
pelvic brim
The pelvic brim is the edge of the pelvic inlet. It is an approximately Mickey Mouse head-shaped line passing through the prominence of the sacrum, the arcuate and pectineal lines, and the upper margin of the pubic symphysis.
Structure
The pel ...
** the
lesser (or true) pelvis, below the pelvic brim
* the
pelvic floor
The pelvic floor or pelvic diaphragm is composed of muscle fibers of the levator ani, the coccygeus muscle, and associated connective tissue which span the area underneath the pelvis. The pelvic diaphragm is a muscular partition formed by the lev ...
(or pelvic diaphragm), below the pelvic cavity
* the
perineum, below the pelvic floor
Pelvic bone
The pelvic skeleton is formed posteriorly (in the area of the back), by the
sacrum
The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30.
The sacrum situates at the upper, back part ...
and the
coccyx and laterally and anteriorly (forward and to the sides), by a pair of
hip bones.
Each hip bone consists of 3 sections,
ilium,
, and
pubis. During childhood, these sections are separate bones, joined by the
triradiate cartilage
The triradiate cartilage (in Latin cartilago ypsiloformis) is the 'Y'-shaped epiphyseal plate between the ilium, ischium and pubis to form the acetabulum of the os coxae.
Human development
In children, the triradiate cartilage closes at an app ...
. During puberty, they fuse together to form a single bone.
Pelvic cavity
The pelvic cavity is a
body cavity
A body cavity is any space or compartment, or potential space, in an animal body. Cavities accommodate organs and other structures; cavities as potential spaces contain fluid.
The two largest human body cavities are the ventral body cavity, and ...
that is bounded by the bones of the pelvis and which primarily contains
reproductive organs and the
rectum
The rectum is the final straight portion of the large intestine in humans and some other mammals, and the Gastrointestinal tract, gut in others. The adult human rectum is about long, and begins at the rectosigmoid junction (the end of the s ...
.
A distinction is made between the
lesser Lesser, from Eliezer (, "Help/Court of my God"), is a surname. Notable people with the surname include:
* Adolf Lesser (1851–1926), German physician
* Aleksander Lesser (1814–1884), Polish painter and art critic
* Anton Lesser (born 1952), Bri ...
or
true pelvis
The pelvic cavity is a body cavity that is bounded by the bones of the pelvis. Its oblique roof is the pelvic inlet (the superior opening of the pelvis). Its lower boundary is the pelvic floor.
The pelvic cavity primarily contains the reproducti ...
inferior to the
terminal line, and the
greater or
false pelvis
The pelvic cavity is a body cavity that is bounded by the bones of the pelvis. Its oblique roof is the pelvic inlet (the superior opening of the pelvis). Its lower boundary is the pelvic floor.
The pelvic cavity primarily contains the reproducti ...
above it. The
pelvic inlet
The pelvic inlet or superior aperture of the pelvis is a planar surface which defines the boundary between the pelvic cavity and the abdominal cavity (or, according to some authors, between two parts of the pelvic cavity, called lesser pelvis and ...
or superior pelvic aperture, which leads into the lesser pelvis, is bordered by the
promontory
A promontory is a raised mass of land that projects into a lowland or a body of water (in which case it is a peninsula). Most promontories either are formed from a hard ridge of rock that has resisted the erosive forces that have removed the so ...
, the
arcuate line of ilium, the
iliopubic eminence
Medial to the anterior inferior iliac spine is a broad, shallow groove, over which the iliacus and psoas major muscles pass. This groove is bounded medially by an eminence, the iliopubic eminence (or iliopectineal eminence), which marks the point ...
, the
pecten of the pubis, and the upper part of the
pubic symphysis. The
pelvic outlet
The lower circumference of the lesser pelvis is very irregular; the space enclosed by it is named the inferior aperture or pelvic outlet. It is an important component of pelvimetry.
Boundaries
It has the following boundaries:
* anteriorly: the pub ...
or inferior pelvic aperture is the region between the
subpubic angle
The pubic arch, also referred to as the ''ischiopubic arch'', is part of the pelvis. It is formed by the convergence of the inferior rami of the ischium and pubis on either side, below the pubic symphysis. The angle at which they converge is kno ...
or
pubic arch, the
ischial tuberosities
The ischial tuberosity (or tuberosity of the ischium, tuber ischiadicum), also known colloquially as the sit bones or sitz bones, or as a pair the sitting bones, is a large swelling posteriorly on the superior ramus of the ischium. It marks t ...
and the
coccyx.
* Ligaments:
obturator membrane
The obturator membrane is a thin fibrous sheet, which almost completely closes the obturator foramen.
Its fibers are arranged in interlacing bundles mainly transverse in direction; the uppermost bundle is attached to the obturator tubercles and co ...
,
inguinal ligament
The inguinal ligament (), also known as Poupart's ligament or groin ligament, is a band running from the pubic tubercle to the anterior superior iliac spine. It forms the base of the inguinal canal through which an indirect inguinal hernia may dev ...
(
lacunar ligament
The lacunar ligament, also named Gimbernat’s ligament, is a ligament in the inguinal region. It connects the inguinal ligament to the pectineal ligament, near the point where they both insert on the pubic tubercle.
Structure
The lacunar ligam ...
,
iliopectineal arch)
Alternatively, the pelvis is divided into three planes: the inlet, midplane, and outlet.
Pelvic floor
![1116 Muscle of the Female Perineum](https://upload.wikimedia.org/wikipedia/commons/f/f9/1116_Muscle_of_the_Female_Perineum.png)
The
pelvic floor
The pelvic floor or pelvic diaphragm is composed of muscle fibers of the levator ani, the coccygeus muscle, and associated connective tissue which span the area underneath the pelvis. The pelvic diaphragm is a muscular partition formed by the lev ...
has two inherently conflicting functions: One is to close the pelvic and abdominal cavities and bear the load of the visceral organs; the other is to control the openings of the
rectum
The rectum is the final straight portion of the large intestine in humans and some other mammals, and the Gastrointestinal tract, gut in others. The adult human rectum is about long, and begins at the rectosigmoid junction (the end of the s ...
and
urogenital
The genitourinary system, or urogenital system, are the organs of the reproductive system and the urinary system. These are grouped together because of their proximity to each other, their common embryological origin and the use of common pathwa ...
organs that pierce the pelvic floor and make it weaker. To achieve both these tasks, the pelvic floor is composed of several overlapping sheets of muscles and connective tissues.
[''Thieme Atlas of Anatomy'' (2006), p. 137]
The pelvic diaphragm is composed of the
levator ani and the
coccygeus muscle. These arise between the
symphysis and the
ischial spine and converge on the coccyx and the
anococcygeal ligament
The anococcygeal body (anococcygeal ligament, or anococcygeal raphe) is a fibrous median raphe in the floor of the pelvis, which extends between the coccyx and the margin of the anus. It is composed of fibers of the levator ani muscle that unite w ...
which spans between the tip of the
coccyx and the
anal hiatus
Anal may refer to:
Related to the anus
*Related to the anus of animals:
** Anal fin, in fish anatomy
** Anal vein, in insect anatomy
** Anal scale, in reptile anatomy
*Related to the human anus:
** Anal sex, a type of sexual activity involving s ...
. This leaves a slit for the anal and urogenital openings. Because of the width of the genital aperture, which is wider in females, a second closing mechanism is required. The
urogenital diaphragm consists mainly of the
deep transverse perineal which arises from the
inferior ischial and
pubic rami and extends to the urogenital hiatus. The urogenital diaphragm is reinforced posteriorly by the
superficial transverse perineal.
[Platzer (2004), p. 106]
The
external anal and
urethral sphincters close the anus and the urethra. The former is surrounded by the
bulbospongiosus
The bulbospongiosus muscle (bulbocavernosus in older texts) is one of the superficial muscles of the perineum. It has a slightly different origin, insertion and function in males and females. In males, it covers the bulb of the penis. In femal ...
which narrows the
vaginal introitus
In mammals, the vagina is the elastic, muscular part of the female genital tract. In humans, it extends from the vestibule to the cervix. The outer vaginal opening is normally partly covered by a thin layer of mucosal tissue called the hymen. ...
in females and surrounds the
corpus spongiosum in males.
Ischiocavernosus
The ischiocavernosus muscle (erectores penis ''or'' erector clitoridis in older texts) is a muscle just below the surface of the perineum, present in both men and women.
Structure
It arises by tendinous and fleshy fibers from the inner surface of ...
squeezes blood into the
corpus cavernosum penis and
clitoridis.
[''Thieme Atlas of Anatomy'' (2006), p. 136]
Variation
Modern humans are to a large extent characterized by
bipedal locomotion
Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' 'double' a ...
and large
brains
A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...
. Because the pelvis is vital to both locomotion and childbirth,
natural selection
Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Charle ...
has been confronted by two conflicting demands: a wide birth canal and locomotion efficiency, a conflict referred to as the "
obstetrical dilemma The obstetrical dilemma is a hypothesis to explain why humans often require assistance from other humans during childbirth to avoid complications, whereas most non-human primates give birth unassisted with relatively little difficulty. This occurs ...
". The female pelvis, or gynecoid pelvis, has evolved to its maximum width for childbirth—a wider pelvis would make women unable to walk. In contrast, human male pelvises are not constrained by the need to give birth and therefore are more optimized for bipedal locomotion.
The principal differences between male and female true and false pelvis include:
* The female pelvis is larger and broader than the male pelvis which is taller, narrower, and more compact.
[''Thieme Atlas of Anatomy'', (2006), p. 113]
* The female inlet is larger and oval in shape, while the male
sacral promontory projects further (i.e. the male inlet is more heart-shaped).
* The sides of the male pelvis converge from the inlet to the outlet, whereas the sides of the female pelvis are wider apart.
* The angle between the
inferior pubic rami is acute (70 degrees) in men, but obtuse (90–100 degrees) in women. Accordingly, the angle is called
subpubic angle
The pubic arch, also referred to as the ''ischiopubic arch'', is part of the pelvis. It is formed by the convergence of the inferior rami of the ischium and pubis on either side, below the pubic symphysis. The angle at which they converge is kno ...
in men and
pubic arch in women.
Additionally, the bones forming the angle/arch are more concave in females but straight in males.
* The distance between the ischia bones is small in males, making the outlet narrow, but large in females, who have a relatively large outlet. The ischial spines and tuberosities are heavier and project farther into the pelvic cavity in males. The greater sciatic notch is wider in females.
* The iliac crests are higher and more pronounced in males, making the male false pelvis deeper and more narrow than in females.
* The male sacrum is long, narrow, more straight, and has a pronounced sacral promontory. The female sacrum is shorter, wider, more curved posteriorly, and has a less pronounced promontory.
* The
acetabula
The acetabulum (), also called the cotyloid cavity, is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint.
Structure
There are three bones of the ''os coxae'' (hip bone) that ...
are wider apart in females than in males. In males, the acetabulum faces more laterally, while it faces more anteriorly in females. Consequently, when males walk the leg can move forwards and backwards in a single plane. In females, the leg must swing forward and inward, from where the pivoting head of the femur moves the leg back in another plane. This change in the angle of the femoral head gives the female gait its characteristic (i.e. swinging of hips).
Development
Each side of the pelvis is formed as cartilage, which ossifies as three main bones which stay separate through childhood:
ilium,
,
pubis. At birth the whole of the hip joint (the acetabulum area and the top of the femur) is still made of cartilage (but there may be a small piece of bone in the
great trochanter
The greater trochanter of the femur is a large, irregular, quadrilateral eminence and a part of the skeletal system.
It is directed lateral and medially and slightly posterior. In the adult it is about 2–4 cm lower than the femoral head.Stan ...
of the femur); this makes it difficult to detect
congenital hip dislocation
Hip dysplasia is an abnormality of the hip joint where the socket portion does not fully cover the ball portion, resulting in an increased risk for joint dislocation. Hip dysplasia may occur at birth or develop in early life. Regardless, it doe ...
by
X-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...
ing.
There is preliminary evidence that the pelvis continues to widen over the course of a lifetime.
Functions
The skeleton of the pelvis is a basin-shaped ring of bones connecting the vertebral column to the femora. It is then connected to two hip bones.
Its primary functions are to bear the weight of the upper body when sitting and standing, transferring that weight from the axial skeleton to the lower appendicular skeleton when standing and walking, and providing attachments for and withstanding the forces of the powerful muscles of locomotion and posture. Compared to the shoulder girdle, the pelvic girdle is thus strong and rigid.
Its secondary functions are to contain and protect the pelvic and abdominopelvic viscera (inferior parts of the urinary tracts, internal reproductive organs), providing attachment for external reproductive organs and associated muscles and membranes.
As a mechanical structure
![Female pelvis](https://upload.wikimedia.org/wikipedia/commons/1/1f/Female_pelvis.png)
The
pelvic girdle consists of the two hip bones. The hip bones are connected to each other anteriorly at the
pubic symphysis, and posteriorly to the
sacrum
The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30.
The sacrum situates at the upper, back part ...
at the
sacroiliac joint
The sacroiliac joint or SI joint (SIJ) is the joint between the sacrum and the ilium bones of the pelvis, which are connected by strong ligaments. In humans, the sacrum supports the spine and is supported in turn by an ilium on each side. The ...
s to form the pelvic ring. The ring is very stable and allows very little mobility, a prerequisite for transmitting loads from the trunk to the lower limbs.
[''Thieme Atlas of Anatomy'' (2006), p. 112]
As a mechanical structure the pelvis may be thought of as four roughly triangular and twisted rings. Each superior ring is formed by the iliac bone; the anterior side stretches from the acetabulum up to the
anterior superior iliac spine
The anterior superior iliac spine (abbreviated: ASIS) is a bony projection of the iliac bone, and an important landmark of surface anatomy. It refers to the anterior extremity of the iliac crest of the pelvis. It provides attachment for the ingui ...
; the posterior side reaches from the top of the acetabulum to the
sacroiliac joint
The sacroiliac joint or SI joint (SIJ) is the joint between the sacrum and the ilium bones of the pelvis, which are connected by strong ligaments. In humans, the sacrum supports the spine and is supported in turn by an ilium on each side. The ...
; and the third side is formed by the
palpable
Palpation is the process of using one's hands to check the body, especially while perceiving/diagnosing a disease or illness. Usually performed by a health care practitioner, it is the process of feeling an object in or on the body to determine ...
iliac crest. The lower ring, formed by the rami of the
pubic
In vertebrates, the pubic region ( la, pubis) is the most forward-facing (ventral and anterior) of the three main regions making up the coxal bone. The left and right pubic regions are each made up of three sections, a superior ramus, inferior ra ...
and
ischial bones, supports the acetabulum and is twisted 80–90 degrees in relation to the superior ring.
[Holm (1980), pp. 425–6]
An alternative approach is to consider the pelvis part of an integrated mechanical system based on the
tensegrity icosahedron
In geometry, an icosahedron ( or ) is a polyhedron with 20 faces. The name comes and . The plural can be either "icosahedra" () or "icosahedrons".
There are infinitely many non- similar shapes of icosahedra, some of them being more symmetrica ...
as an infinite element. Such a system is able to withstand omnidirectional forces—ranging from weight-bearing to childbearing—and, as a low energy requiring system, is favoured by
natural selection
Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Charle ...
.
[Levin (2003), ''A Different Approach to the Mechanics of the Human Pelvis: Tensegrity'' (See conclusions.)]
The pelvic inclination angle is the single most important element of the human body posture and is adjusted at the hips. It is also one of the rare things that can be measured at the assessment of the posture. A simple method of measurement was described by the British orthopedist
Philip Willes
Philip, also Phillip, is a male given name, derived from the Greek language, Greek (''Philippos'', lit. "horse-loving" or "fond of horses"), from a compound of (''philos'', "dear", "loved", "loving") and (''hippos'', "horse"). Prominent Philip ...
and is performed by using an
inclinometer
An inclinometer or clinometer is an measuring instrument, instrument used for measuring angles of slope, elevation, or depression (geology), depression of an object with respect to gravity's direction. It is also known as a ''tilt indicator'', ' ...
.
As an anchor for muscles
The
lumbosacral joint
The lumbosacral joint is a joint of the body, between the last lumbar vertebra and the first sacral segment of the vertebral column. In some ways, calling it a "joint" (singular) is a misnomer, since the lumbosacral junction includes a disc between ...
, between the sacrum and the last
lumbar vertebra
The lumbar vertebrae are, in human anatomy, the five vertebrae between the rib cage and the pelvis. They are the largest segments of the vertebral column and are characterized by the absence of the foramen transversarium within the transverse p ...
, has, like all vertebral joints, an
intervertebral disc
An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column. Each disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold t ...
,
anterior
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
and
posterior ligaments,
ligamenta flava,
interspinous and
supraspinous ligament
The supraspinous ligament, also known as the supraspinal ligament, is a ligament found along the vertebral column.
Structure
The supraspinous ligament connects the tips of the spinous processes from the seventh cervical vertebra to the sacrum. Abo ...
s, and synovial joints between the articular processes of the two bones. In addition to these ligaments the joint is strengthened by the
iliolumbar and lateral lumbosacral ligaments. The iliolumbar ligament passes between the tip of the transverse process of the fifth lumbar vertebra and the posterior part of the iliac crest. The lateral lumbosacral ligament, partly continuous with the iliolumbar ligament, passes down from the lower border of the transverse process of the fifth vertebra to the ala of the sacrum. The movements possible in the lumbosacral joint are flexion and extension, a small amount of lateral flexion (from 7 degrees in childhood to 1 degree in adults), but no axial rotation. Between ages 2–13 the joint is responsible for as much as 75% (about 18 degrees) of flexion and extension in the lumbar spine. From age 35 the ligaments considerably limit the range of motions.
[Palastanga (2006), pp. 331–2]
The three extracapsular ligaments of the
hip joint—the
iliofemoral
The iliofemoral ligament is a ligament of the hip joint which extends from the ilium to the femur in front of the joint. It is also referred to as the Y-ligament (see below). the ligament of Bigelow, the ligament of Bertin and any combinations ...
,
ischiofemoral, and
pubofemoral ligament
The pubofemoral ligament (pubocapsular ligament) is a ligament on the inferior side of the hip joint.
This ligament is attached, above, to the obturator crest and the superior ramus of the pubis; below, it blends with the capsule and with the d ...
s—form a twisting mechanism encircling the neck of the
femur
The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...
. When sitting, with the hip joint flexed, these ligaments become lax permitting a high degree of mobility in the joint. When standing, with the hip joint extended, the ligaments get twisted around the femoral neck, pushing the head of the femur firmly into the
Acetabulum
The acetabulum (), also called the cotyloid cavity, is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint.
Structure
There are three bones of the ''os coxae'' (hip bone) that c ...
, thus stabilizing the joint.
[''Thieme Atlas of Anatomy'' (2006), p. 381] The
zona orbicularis
The zona orbicularis or annular ligament is a ligament on the Femur neck, neck of the femur formed by the circular fibers of the Capsule of hip joint, articular capsule of the Hip, hip joint. It is also known as the orbicular zone, ring ligament, ...
assists in maintaining the contact in the joint by acting like a buttonhole on the femoral head.
[Platzer (2004), p. 198] The intracapsular ligament, the
ligamentum teres, transmits blood vessels that nourish the femoral head.
[''Thieme Atlas of Anatomy'' (2006), p. 383]
Junctions
![Gray321](https://upload.wikimedia.org/wikipedia/commons/5/51/Gray321.png)
The two hip bones are joined anteriorly at the
pubic symphysis by a
fibrous cartilage covered by a
hyaline cartilage
Hyaline cartilage is the glass-like (hyaline) and translucent cartilage found on many joint surfaces. It is also most commonly found in the ribs, nose, larynx, and trachea. Hyaline cartilage is pearl-gray in color, with a firm consistency and has ...
, the interpubic disk, within which a non-synovial cavity might be present. Two ligaments, the
superior
Superior may refer to:
*Superior (hierarchy), something which is higher in a hierarchical structure of any kind
Places
*Superior (proposed U.S. state), an unsuccessful proposal for the Upper Peninsula of Michigan to form a separate state
*Lake ...
and
inferior pubic ligament
The pubic symphysis is a secondary cartilaginous joint between the left and right superior rami of the pubis of the hip bones. It is in front of and below the urinary bladder. In males, the suspensory ligament of the penis attaches to the pubic ...
s, reinforce the symphysis.
[Platzer (2004), p. 188]
Both
sacroiliac joint
The sacroiliac joint or SI joint (SIJ) is the joint between the sacrum and the ilium bones of the pelvis, which are connected by strong ligaments. In humans, the sacrum supports the spine and is supported in turn by an ilium on each side. The ...
s, formed between the auricular surfaces of the sacrum and the two hip bones. are
amphiarthroses, almost immobile joints enclosed by very taut joint capsules. This capsule is strengthened by the
ventral,
interosseous, and
dorsal sacroiliac ligaments.
The most important accessory ligaments of the sacroiliac joint are the
sacrospinous and
sacrotuberous ligament
The sacrotuberous ligament (great or posterior sacrosciatic ligament) is situated at the lower and back part of the pelvis. It is flat, and triangular in form; narrower in the middle than at the ends.
Structure
It runs from the sacrum (the lower ...
s which stabilize the hip bone on the sacrum and prevent the promonotory from tilting forward. Additionally, these two ligaments transform the
greater and
lesser sciatic notch
Below the ischial spine is a small notch, the lesser sciatic notch; it is smooth, coated in the recent state with cartilage, the surface of which presents two or three ridges corresponding to the subdivisions of the tendon of the Obturator internus ...
es into the
greater and
lesser foramina, a pair of important pelvic openings.
[Palastanga (2006), pp. 326–7] The
iliolumbar ligament
The iliolumbar ligament is a strong ligament passing from the tip of the transverse process of the fifth lumbar vertebra to the posterior part of the inner lip of the iliac crest (upper margin of ilium).
Course
It forms the thickened lower bord ...
is a strong ligament which connects the tip of the transverse process of the fifth lumbar vertebra to the posterior part of the inner lip of the iliac crest. It can be thought of as the lower border of the
thoracolumbar fascia
The thoracolumbar fascia (lumbodorsal fascia or thoracodorsal fascia) is a deep investing membrane throughout most of the posterior thorax and abdomen although it is a thin fibrous lamina in the thoracic region. Above, it is continuous with a simil ...
and is occasionally accompanied by a smaller ligamentous band passing between the fourth lumbar vertebra and the iliac crest. The
lateral lumbosacral ligament
Lateral is a geometric term of location which may refer to:
Healthcare
*Lateral (anatomy), an anatomical direction
*Lateral cricoarytenoid muscle
*Lateral release (surgery), a surgical procedure on the side of a kneecap
Phonetics
*Lateral cons ...
is partly continuous with the iliolumbar ligament. It passes between the transverse process of the fifth vertebra to the
ala of the sacrum where it intermingle with the anterior sacroiliac ligament.
[Palastanga (2006), pp. 332–3]
The joint between the sacrum and the coccyx, the
sacrococcygeal symphysis, is strengthened by a series of ligaments. The
anterior sacrococcygeal ligament is an extension of the
anterior longitudinal ligament
The anterior longitudinal ligament is a ligament that runs down the anterior surface of the spine. It traverses all of the vertebral bodies and intervertebral discs on their ventral side. It may be partially cut to treat certain abnormal curvatur ...
(ALL) that run down the anterior side of the
vertebral bodies
The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...
. Its irregular fibers blend with the
periosteum. The
posterior sacrococcygeal ligament
The posterior sacrococcygeal ligament or dorsal sacrococcygeal ligamentOMD: Definition is a ligament which stretches from the sacrum to the coccyx and thus dorsally across the sacrococcygeal symphysis shared by these two bones.
This ligament is di ...
has a deep and a superficial part, the former is a flat band corresponding to the
posterior longitudinal ligament
The posterior longitudinal ligament is a ligament connecting the posterior surfaces of the vertebral bodies of all of the vertebrae. It weakly prevents hyperflexion of the vertebral column. It also prevents posterior spinal disc herniation, althou ...
(PLL) and the latter corresponds to the
ligamenta flava. Several other ligaments complete the
of the
last sacral nerve.
[Morris (2005), p. 59]
Shoulder and intrinsic back
![Gray389](https://upload.wikimedia.org/wikipedia/commons/9/90/Gray389.png)
The inferior parts of
latissimus dorsi
The latissimus dorsi () is a large, flat muscle on the back that stretches to the sides, behind the arm, and is partly covered by the trapezius on the back near the midline. The word latissimus dorsi (plural: ''latissimi dorsorum'') comes from L ...
, one of the muscles of the upper limb, arises from the posterior third of the iliac crest.
[Platzer (2004), p. 140] Its action on the shoulder joint are internal rotation, adduction, and retroversion. It also contributes to respiration (i.e. coughing).
[''Thieme Atlas of Anatomy'' (2006), p. 266] When the arm is adducted, latissimus dorsi can pull it backward and medially until the back of the hand covers the buttocks.
In a longitudinal osteofibrous canal on either side of the spine there is a group of muscles called the
erector spinae
The erector spinae ( ) or spinal erectors is a set of muscles that straighten and rotate the back. The spinal erectors work together with the glutes (gluteus maximus, gluteus medius and gluteus minimus) to maintain stable posture standing or sittin ...
which is subdivided into a lateral superficial and a medial deep tract. In the lateral tract, the
iliocostalis lumborum and
longissimus thoracis originates on the back of the sacrum and the posterior part of the iliac crest. Contracting these muscles bilaterally extends the spine and unilaterally contraction bends the spine to the same side. The medial tract has a "straight" (
interspinales,
intertransversarii
The intertransversarii are small muscles placed between the transverse processes of the vertebrae.
Structure Cervical
In the cervical region they are best developed, consisting of rounded muscular and tendinous fasciculi, and are placed in pairs, ...
, and
spinalis
The spinalis is a portion of the erector spinae, a bundle of muscles and tendons, located nearest to the spine. It is divided into three parts: Spinalis dorsi, spinalis cervicis, and spinalis capitis.
Spinalis dorsi
Spinalis dorsi, the medial co ...
) and an "oblique" (
multifidus and
semispinalis) component, both of which stretch between vertebral processes; the former acts similar to the muscles of the lateral tract, while the latter function unilaterally as spine extensors and bilaterally as spine rotators. In the medial tract, the multifidi originates on the
sacrum
The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30.
The sacrum situates at the upper, back part ...
.
[Platzer (2004), pp. 72, 74]
Abdomen
The muscles of the
abdominal wall are subdivided into a superficial and a deep group.
The superficial group is subdivided into a lateral and a medial group. In the medial superficial group, on both sides of the centre of the abdominal wall (the
''linea alba''), the
rectus abdominis stretches from the cartilages of ribs V-VII and the
sternum down to the
pubic crest. At the lower end of the rectus abdominis, the
pyramidalis tenses the ''linea alba''. The lateral superficial muscles, the
transversus
The transverse abdominal muscle (TVA), also known as the transverse abdominis, transversalis muscle and transversus abdominis muscle, is a muscle layer of the anterior and lateral (front and side) abdominal wall which is deep to (layered below) th ...
and
external and
internal oblique muscles, originate on the rib cage and on the pelvis (iliac crest and
inguinal ligament
The inguinal ligament (), also known as Poupart's ligament or groin ligament, is a band running from the pubic tubercle to the anterior superior iliac spine. It forms the base of the inguinal canal through which an indirect inguinal hernia may dev ...
) and are attached to the anterior and posterior layers of the
sheath
Sheath pronounced as , may refer to:
* Scabbard, a sheath for holding a sword, knife, or other large blade, as well as guns, such as rifles.
* The outer covering of a cable
* Condom, a kind of contraception
* Debye sheath, a layer of a plasma in ...
of the rectus.
[Platzer (2004), pp. 84–91]
Flexing the trunk (bending forward) is essentially a movement of the rectus muscles, while lateral flexion (bending sideways) is achieved by contracting the obliques together with the quadratus lumborum and intrinsic back muscles. Lateral rotation (rotating either the trunk or the pelvis sideways) is achieved by contracting the internal oblique on one side and the external oblique on the other. The transversus' main function is to produce abdominal pressure in order to constrict the abdominal cavity and pull the diaphragm upward.
There are two muscles in the deep or posterior group.
Quadratus lumborum
The quadratus lumborum muscle, informally called the ''QL'', is a paired muscle of the left and right posterior abdominal wall. It is the deepest abdominal muscle, and commonly referred to as a back muscle. Each is irregular and quadrilateral in sh ...
arises from the posterior part of the iliac crest and extends to the rib XII and lumbar vertebrae I–IV. It unilaterally bends the trunk to the side and bilaterally pulls the 12th rib down and assists in expiration. The
iliopsoas consists of
psoas major
The psoas major ( or ; from grc, ψόᾱ, psóā, muscles of the loins) is a long fusiform muscle located in the lateral lumbar region between the vertebral column and the brim of the lesser pelvis. It joins the iliacus muscle to form the iliop ...
(and occasionally
psoas minor
The psoas minor muscle ( or ; from grc, ψόᾱ, psóā, muscles of the loins) is a long, slender skeletal muscle. When present, it is located anterior to the psoas major muscle.Tank (2005), p 93Gray (2008), p 1372
Structure
The psoas minor mus ...
) and
iliacus, muscles with separate origins but a common insertion on the
lesser trochanter of the femur. Of these, only iliacus is attached to the pelvis (the
iliac fossa). However, psoas passes through the pelvis and because it acts on two joints, it is topographically classified as a posterior abdominal muscle but functionally as a hip muscle. Iliopsoas flexes and externally rotates the hip joints, while unilateral contraction bends the trunk laterally and bilateral contraction raises the trunk from the
supine position.
[''Thieme Atlas of Anatomy'' (2006), p. 128]
Hip and thigh
The muscles of the
hip
In vertebrate anatomy, hip (or "coxa"Latin ''coxa'' was used by Celsus in the sense "hip", but by Pliny the Elder in the sense "hip bone" (Diab, p 77) in medical terminology) refers to either an anatomical region or a joint.
The hip region is ...
are divided into a dorsal and a ventral group.
The dorsal hip muscles are either inserted into the region of the
lesser trochanter (anterior or inner group) or the
greater trochanter (posterior or outer group). Anteriorly, the
psoas major
The psoas major ( or ; from grc, ψόᾱ, psóā, muscles of the loins) is a long fusiform muscle located in the lateral lumbar region between the vertebral column and the brim of the lesser pelvis. It joins the iliacus muscle to form the iliop ...
(and occasionally
psoas minor
The psoas minor muscle ( or ; from grc, ψόᾱ, psóā, muscles of the loins) is a long, slender skeletal muscle. When present, it is located anterior to the psoas major muscle.Tank (2005), p 93Gray (2008), p 1372
Structure
The psoas minor mus ...
) originates along the spine between the rib cage and pelvis. The
iliacus originates on the
iliac fossa to join psoas at the
iliopubic eminence
Medial to the anterior inferior iliac spine is a broad, shallow groove, over which the iliacus and psoas major muscles pass. This groove is bounded medially by an eminence, the iliopubic eminence (or iliopectineal eminence), which marks the point ...
to form the
iliopsoas which is inserted into the lesser trochanter.
[Platzer (2004), p. 234] The iliopsoas is the most powerful hip flexor.
[''Thieme Atlas of Anatomy'' (2006), p. 422.]
The posterior group includes the
gluteus maximus
The gluteus maximus is the main extensor muscle of the hip. It is the largest and outermost of the three gluteal muscles and makes up a large part of the shape and appearance of each side of the hips. It is the single largest muscle in the human ...
,
gluteus medius
The gluteus medius, one of the three gluteal muscles, is a broad, thick, radiating muscle. It is situated on the outer surface of the pelvis.
Its posterior third is covered by the gluteus maximus, its anterior two-thirds by the gluteal aponeu ...
, and
gluteus minimus
The gluteus minimus, or glutæus minimus, the smallest of the three gluteal muscles, is situated immediately beneath the gluteus medius.
Structure
It is fan-shaped, arising from the outer surface of the ilium, between the anterior and infer ...
. Maximus has a wide origin stretching from the posterior part of the iliac crest and along the sacrum and coccyx, and has two separate insertions: a proximal which radiates into the
iliotibial tract
The iliotibial tract or iliotibial band (ITB; also known as Maissiat's band or the IT band) is a longitudinal fibrous reinforcement of the fascia lata. The action of the muscles associated with the ITB (tensor fasciae latae and some fibers of glu ...
and a distal which inserts into the
gluteal tuberosity
The gluteal tuberosity is the lateral one of the three upward prolongations of the linea aspera of the femur, extending to the base of the greater trochanter. It serves as the principal insertion site for the gluteus maximus muscle.
Structure
T ...
on the posterior side of the femoral shaft. It is primarily an extensor and lateral rotator of the hip joint, but, because of its bipartite insertion, it can both adduct and abduct the hip. Medius and minimus arise on the external surface of the ilium and are both inserted into the greater trochanter. Their anterior fibers are medial rotators and flexors while the posterior fibers are lateral rotators and extensors. The
piriformis has its origin on the ventral side of the sacrum and is inserted on the greater trochanter. It abducts and laterally rotates the hip in the upright posture and assists in extension of the thigh.
The
tensor fasciae latae
The tensor fasciae latae (or tensor fasciæ latæ or, formerly, tensor vaginae femoris) is a muscle of the thigh. Together with the gluteus maximus, it acts on the iliotibial band and is continuous with the iliotibial tract, which attaches to the ...
arises on the anterior superior iliac spine and inserts into the iliotibial tract.
[''Thieme Atlas of Anatomy'' (2006), p. 424] It presses the
head of the femur into the
acetabulum
The acetabulum (), also called the cotyloid cavity, is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint.
Structure
There are three bones of the ''os coxae'' (hip bone) that c ...
and flexes, medially rotates, and abducts the hip.
The ventral hip muscles are important in the control of the body's balance. The
internal and
external obturator muscles together with the
quadratus femoris are lateral rotators of the hip. Together they are stronger than the medial rotators and therefore the feet point outward in the normal position to achieve a better support. The obturators have their origins on either sides of the
obturator foramen
The obturator foramen (Latin foramen obturatum) is the large opening created by the ischium and pubis (bone), pubis bones of the pelvis through which nerves and blood vessels pass.
Structure
It is bounded by a thin, uneven margin, to which a str ...
and are inserted into the
trochanteric fossa on the femur. Quadratus arises on the
ischial tuberosity
The ischial tuberosity (or tuberosity of the ischium, tuber ischiadicum), also known colloquially as the sit bones or sitz bones, or as a pair the sitting bones, is a large swelling posteriorly on the superior ramus of the ischium. It marks th ...
and is inserted into the
intertrochanteric crest. The
superior
Superior may refer to:
*Superior (hierarchy), something which is higher in a hierarchical structure of any kind
Places
*Superior (proposed U.S. state), an unsuccessful proposal for the Upper Peninsula of Michigan to form a separate state
*Lake ...
and
inferior gemelli, arising from the ischial spine and ischial tuberosity respectively, can be thought of as marginal heads of the obturator internus, and their main function is to assist this muscle.
The muscles of the
thigh
In human anatomy, the thigh is the area between the hip (pelvis) and the knee. Anatomically, it is part of the lower limb.
The single bone in the thigh is called the femur. This bone is very thick and strong (due to the high proportion of bone ...
can be subdivided into adductors (medial group), extensors (anterior group), and flexors (posterior group). The extensors and flexors act on the knee joint, while the adductors mainly act on the hip joint.
The thigh adductors have their origins on the
inferior ramus of the pubic bone and are, with the exception of
gracilis, inserted along the femoral shaft. Together with
sartorius and
semitendinosus, gracilis reaches beyond the knee to their common insertion on the
tibia
The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...
.
[Platzer (2004), pp. 240–3]
The anterior thigh muscles form the
quadriceps which is inserted on the
patella
The patella, also known as the kneecap, is a flat, rounded triangular bone which articulates with the femur (thigh bone) and covers and protects the anterior articular surface of the knee joint. The patella is found in many tetrapods, such as m ...
with a common tendon. Three of the four muscles have their origins on the femur, while
rectus femoris arises from the anterior inferior iliac spine and is thus the only of the four acting on two joints.
[Platzer (2004), p. 248]
The posterior thigh muscles have their origins on the
inferior ischial ramus, with the exception of the short head of the
biceps femoris
The biceps femoris () is a muscle of the thigh located to the posterior, or back. As its name implies, it has two parts, one of which (the long head) forms part of the hamstrings muscle group.
Structure
It has two heads of origin:
*the ''long h ...
. The
semitendinosus and
semimembranosus are inserted on the tibia on the medial side of the knee, while biceps femoris is inserted on the
fibula
The fibula or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. Its upper extremity is ...
, on the knee's lateral side.
[Platzer (2004), p. 250]
In pregnancy and childbirth
In later stages of
pregnancy
Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins.
Pregnancy usually occurs by sexual intercourse, but ca ...
the
fetus
A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo. Following embryonic development the fetal stage of development takes place. In human prenatal development, fetal deve ...
's head aligns inside the pelvis. Also joints of bones soften due to the effect of pregnancy hormones. These factors may cause ''pelvic joint pain'' (
symphysis pubis dysfunction
Symphysis pubis dysfunction (SPD), commonly known as pubic symphysis dysfunction or lightning crotch, is a condition that causes excessive movement of the pubic symphysis, either anterior or lateral, as well as associated pain, possibly because of ...
or SPD). As the end of pregnancy approaches, the ligaments of the sacroiliac joint loosen, letting the pelvis outlet widen somewhat; this is easily noticeable in the
cow
Cattle (''Bos taurus'') are large, domesticated, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus ''Bos''. Adult females are referred to as cows and adult ma ...
.
During
childbirth
Childbirth, also known as labour and delivery, is the ending of pregnancy where one or more babies exits the internal environment of the mother via vaginal delivery or caesarean section. In 2019, there were about 140.11 million births globall ...
(unless by
Cesarean section) the fetus passes through the maternal ''pelvic opening''.
Clinical significance
Hip fractures often affect the elderly and occur more often in females, and this is frequently due to
osteoporosis
Osteoporosis is a systemic skeletal disorder characterized by low bone mass, micro-architectural deterioration of bone tissue leading to bone fragility, and consequent increase in fracture risk. It is the most common reason for a broken bone ...
. There are also different types of
pelvic fracture
A pelvic fracture is a break of the bony structure of the pelvis. This includes any break of the sacrum, hip bones (ischium, pubis, ilium), or tailbone. Symptoms include pain, particularly with movement. Complications may include internal ble ...
often resulting from traffic accidents.
Pelvic pain
Pelvic pain is pain in the area of the pelvis. Acute pain is more common than chronic pain. If the pain lasts for more than six months, it is deemed to be chronic pelvic pain. It can affect both the male and female pelvis.
Common causes in include ...
generally, can affect anybody and has a variety of causes;
bowel adhesion
Adhesions are fibrous bands that form between tissues and organs, often as a result of injury during surgery. They may be thought of as internal scar tissue that connects tissues not normally connected.
Pathophysiology
Adhesions form as a natural ...
s,
irritable bowel syndrome,
interstitial cystitis,
endometriosis
Endometriosis is a disease of the female reproductive system in which cells similar to those in the endometrium, the layer of tissue that normally covers the inside of the uterus, grow outside the uterus. Most often this is on the ovaries, f ...
in women.
There are many
anatomical variation
An anatomical variation, anatomical variant, or anatomical variability is a presentation of body structure with morphological features different from those that are typically described in the majority of individuals. Anatomical variations are categ ...
s of the pelvis. In the female the pelvis can be of a much larger size than normal, known as a ''giant pelvis'' or
pelvis justo major
''Pelvis justo major'' (also called "Giant Pelvis") is a rare condition of the adult female pelvis where the pelvis flairs above the Iliopectineal line. It is 1.5 or more times larger than an average pelvis in every direction and is at least 42&nb ...
, or it can be much smaller, known as a ''reduced pelvis'' or ''pelvis justo minor''.
Other variations include an ''android pelvis'' the normal shape of the male pelvis, in women this shape can prove problematic in
childbirth
Childbirth, also known as labour and delivery, is the ending of pregnancy where one or more babies exits the internal environment of the mother via vaginal delivery or caesarean section. In 2019, there were about 140.11 million births globall ...
.
History
Caldwell–Moloy classification
Throughout the 20th century
pelvimetric measurements were made on pregnant women to determine whether a natural birth would be possible, a practice today limited to cases where a specific problem is suspected or following a caesarean delivery.
William Edgar Caldwell
William is a male given name of Germanic languages, Germanic origin.Hanks, Hardcastle and Hodges, ''Oxford Dictionary of First Names'', Oxford University Press, 2nd edition, , p. 276. It became very popular in the English language after the Norm ...
and
Howard Carmen Moloy
Howard is an English language, English-language given name originating from Old French Huard (disambiguation), Huard (or Houard) from a Germanic source similar to Old High German ''*Hugihard'' "heart-brave", or ''*Hoh-ward'', literally "high defe ...
studied collections of skeletal pelves and thousands of stereoscopic radiograms and finally recognized three types of female pelves plus the masculine type. In 1933 and 1934 they published their typology, including the Greek names since then frequently quoted in various handbooks: Gynaecoid (''gyne'', woman), anthropoid (''anthropos'', human being), platypelloid (''platys'', flat), and android (''aner'', man).
* The gynaecoid pelvis is the so-called normal female pelvis. Its inlet is either slightly oval, with a greater transverse diameter, or round. The interior walls are straight, the subpubic arch wide, the sacrum shows an average to backward inclination, and the greater sciatic notch is well rounded. Because this type is spacious and well proportioned there is little or no difficulty in the birth process. Caldwell and his co-workers found gynaecoid pelves in about 50 per cent of specimens.
* The platypelloid pelvis has a transversally wide, flattened shape, is wide anteriorly, greater sciatic notches of male type, and has a short sacrum that curves inwards reducing the diameters of the lower pelvis. This is similar to the
rachitic pelvis where the softened bones widen laterally because of the weight from the upper body resulting in a reduced anteroposterior diameter. Giving birth with this type of pelvis is associated with problems, such as transverse arrest. Less than 3 per cent of women have this pelvis type.
* The android pelvis is a female pelvis with masculine features, including a wedge or heart shaped inlet caused by a prominent sacrum and a triangular anterior segment. The reduced pelvis outlet often causes problems during child birth. In 1939 Caldwell found this type in one third of white women and in one sixth of non-white women.
* The anthropoid pelvis is characterized by an oval shape with a greater anteroposterior diameter. It has straight walls, a small subpubic arch, and large sacrosciatic notches. The sciatic spines are placed widely apart and the sacrum is usually straight resulting in deep non-obstructed pelvis. Caldwell found this type in one quarter of white women and almost half of non-white women.
However, Caldwell and Moloy then complicated this simple fourfold scheme by dividing the pelvic inlet into posterior and anterior segments. They named a pelvis according to the anterior segment and affixed another type according to the character of the posterior segment (i.e. anthropoid-android) and ended up with no less than 14 morphologies. Notwithstanding the popularity of this simple classification, the pelvis is much more complicated than this as the pelvis can have different dimensions at various levels of the birth canal.
Caldwell and Moloy also classified the
physique of women according to their types of pelves: the gynaecoid type has small shoulders, a small waist and wide hips; the android type looks square-shaped from behind; and the anthropoid type has wide shoulders and narrow hips. Lastly, in their article they described all non-gynaecoid or "mixed" types of pelves as "abnormal", a word which has stuck in the medical world even though at least 50 per cent of women have these "abnormal" pelves.
The classification of Caldwell and Moloy was influenced by earlier classifications attempting to define the ideal female pelvis, treating any deviations from this ideal as dysfunctions and the cause of obstructed labour. In the 19th century anthropologists and others saw an evolutionary scheme in these pelvic typologies, a scheme since then refuted by archaeology. Since the 1950s
malnutrition
Malnutrition occurs when an organism gets too few or too many nutrients, resulting in health problems. Specifically, it is "a deficiency, excess, or imbalance of energy, protein and other nutrients" which adversely affects the body's tissues a ...
is thought to be one of the chief factors affecting pelvic shape in the
Third World
The term "Third World" arose during the Cold War to define countries that remained non-aligned with either NATO or the Warsaw Pact. The United States, Canada, Japan, South Korea, Western European nations and their allies represented the " First ...
even though there are at least some genetic component to variation in pelvic morphology.
Nowadays obstetric suitability of the female pelvis is assessed by
ultrasound
Ultrasound is sound waves with frequency, frequencies higher than the upper audible limit of human hearing range, hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hea ...
. The dimensions of the head of the fetus and of the birth canal are accurately measured and compared, and the feasibility of labor can be predicted.
Other animals
![Falcarius pelvis](https://upload.wikimedia.org/wikipedia/commons/f/fb/Falcarius_pelvis.jpg)
The pelvic girdle was present in early
vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...
s, and can be tracked back to the paired fins of fish that were some of the earliest
chordate
A chordate () is an animal of the phylum Chordata (). All chordates possess, at some point during their larval or adult stages, five synapomorphies, or primary physical characteristics, that distinguish them from all the other taxa. These fiv ...
s.
The shape of the pelvis, most notably the orientation of the iliac crests and shape and depth of the
acetabula
The acetabulum (), also called the cotyloid cavity, is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint.
Structure
There are three bones of the ''os coxae'' (hip bone) that ...
, reflects the style of locomotion and body mass of an animal. In bipedal mammals, the iliac crests are parallel to the vertically oriented sacroiliac joints, where in quadrupedal mammals they are parallel to the horizontally oriented sacroiliac joints. In heavy mammals, especially in quadrupeds, the pelvis tend to be more vertically oriented because this allows the pelvis to support greater weight without dislocating the sacroiliac joints or adding torsion to the vertebral column.
In ambulatory mammals the acetabula are shallow and open to allow a wider range of hip movements, including significant abduction, than in cursorial mammals. The lengths of the ilium and ischium and their angles relative to the acetabulum are functionally important as they determine the moment arms for the hip extensor muscles that provide momentum during locomotion.
[Hall (2007), pp. 254–5]
In addition to this, the relatively wide shape (front to back) of the pelvis provides greater leverage for the gluteus medius and minimus. These muscles are responsible for hip abduction which plays an integral role in upright balance.
Primates
In
primate
Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter including huma ...
s, the pelvis consists of four parts - the left and the right
hip bones which meet in the mid-line ventrally and are fixed to the sacrum dorsally and the coccyx. Each hip bone consists of three components, the ilium, the
, and the pubis, and at the time of sexual maturity these bones become fused together, though there is never any movement between them. In
human
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
s, the ventral joint of the pubic bones is closed.
Larger
ape
Apes (collectively Hominoidea ) are a clade of Old World simians native to sub-Saharan Africa and Southeast Asia (though they were more widespread in Africa, most of Asia, and as well as Europe in prehistory), which together with its siste ...
s, such as ''Pongo'' (
orangutan
Orangutans are great apes native to the rainforests of Indonesia and Malaysia. They are now found only in parts of Borneo and Sumatra, but during the Pleistocene they ranged throughout Southeast Asia and South China. Classified in the genus ...
s), ''Gorillas'' (
gorilla
Gorillas are herbivorous, predominantly ground-dwelling great apes that inhabit the tropical forests of equatorial Africa. The genus ''Gorilla'' is divided into two species: the eastern gorilla and the western gorilla, and either four or fi ...
s), ''Australopithecus afarensis'', and ''Pan troglodytes'' (
chimpanzee
The chimpanzee (''Pan troglodytes''), also known as simply the chimp, is a species of great ape native to the forest and savannah of tropical Africa. It has four confirmed subspecies and a fifth proposed subspecies. When its close relative th ...
s), have longer three-pelvic planes with a maximum diameter in the sagittal plane.
Evolution
The present-day morphology of the pelvis is inherited from the pelvis of our quadrupedal ancestors. The most striking feature of evolution of the pelvis in primates is the widening and the shortening of the blade called the ilium. Because of the stresses involved in bipedal locomotion, the muscles of the thigh move the thigh forward and backward, providing the power for bi-pedal and quadrupedal locomotion.
The drying of the environment of East Africa in the period since the creation of the Red Sea and the African Rift Valley saw open woodlands replace the previous closed canopy forest. The apes in this environment were compelled to travel from one clump of trees to another across open country. This led to a number of complementary changes to the human pelvis. It is suggested that bipedalism was the result.
Additional images
File:Slide1ADAA.JPG, Diameters of pelvic inlet
The pelvic inlet or superior aperture of the pelvis is a planar surface which defines the boundary between the pelvic cavity and the abdominal cavity (or, according to some authors, between two parts of the pelvic cavity, called lesser pelvis and ...
.
File:Gray235.png, Right hip bone. External surface.
File:Pelvic Girdle Anatomy by Jason Christian.webm, Pelvic Girdle Anatomy
See also
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Coccygeal plexus
The coccygeal plexus is a nerve plexus near the coccyx bone.
Structure
This plexus is formed by the ventral rami of the fourth and fifth sacral nerves, S4 & S5, and the ventral ramus of the coccygeal nerve, Co. The relative contributions of S4 an ...
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Coccyx (tailbone)
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Pelvimetry
Pelvimetry is the measurement of the female pelvis. It can theoretically identify cephalo-pelvic disproportion, which is when the capacity of the pelvis is inadequate to allow the fetus to negotiate the birth canal. However, clinical evidence ind ...
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Pelvis justo major
''Pelvis justo major'' (also called "Giant Pelvis") is a rare condition of the adult female pelvis where the pelvis flairs above the Iliopectineal line. It is 1.5 or more times larger than an average pelvis in every direction and is at least 42&nb ...
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Pubic symphysis
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Sacroiliac joint
The sacroiliac joint or SI joint (SIJ) is the joint between the sacrum and the ilium bones of the pelvis, which are connected by strong ligaments. In humans, the sacrum supports the spine and is supported in turn by an ilium on each side. The ...
Notes
References
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External links
{{DEFAULTSORT:Pelvis, human
Flat bones