In vertebrates, the pubic region ( la, pubis) is the most forward-facing ( ventral and

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 ...

) 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 ramus, and a body.

Structure

The pubic region is made up of a ''body'', ''superior ramus'', and ''inferior ramus'' (). The left and right coxal bones join at the pubic symphysis. It is covered by a layer of fat, which is covered by the mons pubis. The pubis is the lower limit of the suprapubic region. In the female, the pubic region is anterior to the urethral sponge.

Body

The body forms the wide, strong, middle and flat part of the pubic region. The bodies of the left and right pubic regions join at the pubic symphysis. The rough upper edge is the pubic crest, ending laterally in the pubic tubercle. This tubercle, found roughly 3 cm from the pubic symphysis, is a distinctive feature on the lower part of the abdominal wall; important when localizing the

superficial inguinal ring The inguinal canals are the two passages in the anterior abdominal wall of humans and animals which in males convey the spermatic cords and in females the round ligament of the uterus. The inguinal canals are larger and more prominent in males. Th ...

and the femoral canal of the inguinal canal. The inner surface of the body forms part of the wall of the lesser pelvis and joints to the origin of a part of the

obturator internus The internal obturator muscle or obturator internus muscle originates on the medial surface of the obturator membrane, the ischium near the membrane, and the rim of the pubis. It exits the pelvic cavity through the lesser sciatic foramen. The i ...

muscle.

Superior pubic ramus

The superior pubic ramus is the upper of the two rami. It forms the upper edge of the obturator foramen. It extends from the body to the median plane where it joins with the ramus of the opposite side. It consists of an inner flattened part and a narrow outer prismoid portion. Medial surface Surfaces * The ''anterior surface'' is rough, directed downward and outward, and serves for the origin of various muscles. The adductor longus arises from the upper and medial angle, immediately below the crest; lower down, the obturator externus, the adductor brevis, and the upper part of the gracilis take origin. * The ''posterior surface'', convex from above downward, concave from side to side, is smooth, and forms part of the anterior wall of the pelvis. It gives origin to the levator ani and

, and attachment to the puboprostatic ligaments and to a few muscular fibers prolonged from the bladder. Borders * The ''upper border'' presents a prominent tubercle, the pubic tubercle ( pubic spine), which projects forward; the inferior crus of the subcutaneous inguinal ring (external abdominal ring), and the

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 ...

(Poupart's ligament) are attached to it. Passing upward and laterally from the pubic tubercle is a well-defined ridge, forming a part of the pectineal line which marks the brim of the lesser pelvis: to it are attached a portion of the inguinal falx (conjoined tendon of obliquus internus and transversus), the

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 ...

(Gimbernat's ligament), and the

reflected inguinal ligament The reflected inguinal ligament (triangular fascia) is a layer of tendinous fibers of a triangular shape, formed by an expansion from the lacunar ligament and the inferior crus of the subcutaneous inguinal ring. It passes medialward behind the spe ...

(triangular fascia). Medial to the pubic tubercle is the crest, which extends from this process to the medial end of the bone. It affords attachment to the inguinal falx, and to the rectus abdominis and pyramidalis. The point of junction of the crest with the medial border of the bone is called the angle; to it, as well as to the symphysis, the

superior crus The superficial inguinal ring is bounded below by the crest of the pubis; on either side by the margins of the opening in the aponeurosis, which are called the crura of the ring; and above, by a series of curved intercrural fibers. * The infe ...

of the subcutaneous inguinal ring is attached. The ''medial border'' is articular; it is oval, and is marked by eight or nine transverse ridges, or a series of nipple-like processes arranged in rows, separated by grooves; they serve for the attachment of a thin layer of cartilage, which intervenes between it and the interpubic fibrocartilaginous lamina. The ''lateral border'' presents a sharp margin, the obturator crest, which forms part of the circumference of the obturator foramen and affords attachment to the obturator membrane. Lateral portion Surfaces * The ''superior surface'' presents a continuation of the pectineal line, already mentioned as commencing at the pubic tubercle. In front of this line, the surface of bone is triangular in form, wider laterally than medially, and is covered by the

pectineus The pectineus muscle (, from the Latin word ''pecten'', meaning comb) is a flat, quadrangular muscle, situated at the anterior (front) part of the upper and medial (inner) aspect of the thigh. The pectineus muscle is the most anterior adductor o ...

. The surface is bounded, laterally, by a rough eminence, the iliopectineal eminence, which serves to indicate the point of junction of the

ilium Ilium or Ileum may refer to: Places and jurisdictions * Ilion (Asia Minor), former name of Troy * Ilium (Epirus), an ancient city in Epirus, Greece * Ilium, ancient name of Cestria (Epirus), an ancient city in Epirus, Greece * Ilium Building, a ...

and pubis, and below by a prominent ridge which extends from the acetabular notch to the pubic tubercle. * The ''inferior surface'' forms the upper boundary of the obturator foramen, and presents, laterally, a broad and deep, oblique groove, for the passage of the obturator vessels and nerve; and medially, a sharp margin, the

obturator crest The anterior border of the superior pubic ramus presents a sharp margin, the obturator crest, which forms part of the circumference of the obturator foramen superiorly and affords attachment to the obturator membrane. The obturator crest extends f ...

, forming part of the circumference of the obturator foramen, and giving attachment to the obturator membrane. * The ''posterior surface'' constitutes part of the anterior boundary of the lesser pelvis. It is smooth, convex from above downward, and affords origin to some fibers of the

Inferior pubic ramus

The inferior pubic ramus is a part of the pelvis and is thin and flat. It passes laterally and downward from the medial end of the superior ramus; it becomes narrower as it descends and joins with the inferior ramus of the ischium below the obturator foramen. Surfaces * Its ''anterior surface'' is rough, for the origin of muscles—the gracilis along its medial border, a portion of the Obturator externus where it enters into the formation of the obturator foramen, and between these two, the

adductores brevis The adductor brevis is a muscle in the thigh situated immediately deep to the pectineus and adductor longus. It belongs to the adductor muscle group. The main function of the adductor brevis is to pull the thigh medially. The adductor brevis ...

and magnus, the former being the more medial. * The ''posterior surface'' is smooth, and gives origin to the

, and, close to the medial margin, to the

Constrictor urethrae The urethral sphincters are two muscles used to control the exit of urine in the urinary bladder through the urethra. The two muscles are either the male or female external urethral sphincter and the internal urethral sphincter. When either of th ...

. Borders * In the female pelvis, the ''medial border'' is thick, rough, and everted, and presents two ridges, separated by an intervening space. The ridges extend downwards, and are continuous with similar ridges on the inferior ramus of the ischium; ** to the external ridge is attached the fascia of Colles ** to the internal ridge is attached the inferior fascia of the urogenital diaphragm * The ''lateral border'' is thin and sharp, forms part of the circumference of the obturator foramen, and gives attachment to the obturator membrane.

Other animals

Mammals

Non- placental mammals possess osteological projections of the pubis known as epipubic bones. These evolved first among derived

cynodonts The cynodonts () (clade Cynodontia) are a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 mya), and extensively diversified after the Permian–Triassic extinction event. Cynodonts had a wide variety ...

, and evolved as a means of support for muscles flexing the thigh, facilitating the development of an erect gait. However, these prevent the expansion of the torso, preventing pregnancy and forcing the animal to give birth to larval young (the modern marsupial "joeys" and

monotreme Monotremes () are prototherian mammals of the order Monotremata. They are one of the three groups of living mammals, along with placentals (Eutheria), and marsupials (Metatheria). Monotremes are typified by structural differences in their brain ...

"puggles"). Placentals are unique among all mammals, including other eutherians, in having lost epipubic bones and having been able to develop proper pregnancy. In some groups, remnants of these pre-pubic bones can be found as os penises.

Dinosaurs

The

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

Dinosauria is divided into the Saurischia and

Ornithischia Ornithischia () is an extinct order of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek s ...

based on hip structure, including importantly that of the pubis. An opisthopubic pelvis is a condition where the pubic bone extends back towards the tail of the animal, a trait that is also present in birds. In a propubic pelvis, however, the pubic bone extends forward towards the head of the animal, as can be seen in the typical saurischian pelvic structure pictured below. 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 ...

, which can be thought of as a "hip-socket", is an opening on each side of the pelvic girdle formed where the

ischium The ischium () form ...

, and pubis all meet, and into which the head of the femur inserts. The orientation and position of the acetabulum is one of the main morphological traits that caused dinosaurs to walk in an upright posture with their legs directly underneath their bodies.Martin, A.J. (2006). Introduction to the Study of Dinosaurs. Second Edition. Oxford, Blackwell Publishing. pg. 299-300. . The ''prepubic process'' is a bony extension of the pubis that extends forward from the hip socket and toward the front of the animal. This adaptation is thought to have played a role in supporting the abdominal muscles. Ornithischia pelvis structure.svg, Ornithischian pelvic structure (left side) Saurischia pelvis structure.svg, Saurischian pelvic structure (left side).

Additional images

File:Skeletal pelvis-pubis.svg, 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 pelvic bone, with parts labelled. The pubic bone consists of the body and superior pubic ramus (4), and the inferior pubic ramus (3), which join at the pubic symphysis. The gap between them is the obturator foramen. File:Gray235.png, Right hip bone. External surface. File:Gray236.png, Right hip bone. Internal surface. File:Gray237.png, Plan of ossification of the hip bone. File:Gray321.png, Symphysis pubis exposed by a coronal section. File:Gray404.png, Left levator ani from within. File:Gray436.png, The obturator externus. File:Gray341.png, Left hip-joint, opened by removing the floor of the acetabulum from within the pelvis. File:Slide16A.JPG, Pubis

References

External links

* - "The Male Pelvis: Hip Bone" {{Authority control Bones of the pelvis