The wing (ala) of ilium is the large expanded portion of the ilium, the bone which bounds the

greater 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 ...

laterally. It presents for examination two surfaces—an external and an internal—a crest, and two borders—an anterior and a posterior.

External surface

The external surface, known as the dorsum ossis ilium, is directed backward and lateralward behind, and downward and lateralward in front. It is smooth, convex in front, deeply concave behind; bounded above by the crest, below by the upper border of 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 ...

, in front and behind by the anterior and posterior borders. This surface is crossed in an arched direction by three lines—the posterior,

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

inferior gluteal line The gluteal lines are three curved lines outlined from three bony ridges on the exterior surface of the ilium in the gluteal region. They are the anterior gluteal line; the inferior gluteal line, and the posterior gluteal line. The gluteus mini ...

s. The ''posterior gluteal line'' (superior curved line), the shortest of the three, begins at the crest, about 5 cm in front of its posterior extremity; it is at first distinctly marked, but as it passes downward to the upper part of the

greater sciatic notch The greater sciatic notch is a notch in the ilium (bone), ilium, one of the bones that make up the human pelvis. It lies between the posterior inferior iliac spine (above), and the ischial spine (below). The sacrospinous ligament changes this notch ...

, where it ends, it becomes less distinct, and is often altogether lost. Behind this line is a narrow semilunar surface, the upper part of which is rough and gives origin to a portion of 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 ...

; the lower part is smooth and has no muscular fibers attached to it. The ''anterior gluteal line'' (middle curved line), the longest of the three, begins at the crest, about 4 cm behind its anterior extremity, and, taking a curved direction downward and backward, ends at the upper part of the greater sciatic notch. The space between the anterior and posterior gluteal lines and the crest is concave, and gives origin to the

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 ...

. Near the middle of this line a nutrient

foramen In anatomy and osteology, a foramen (;Entry "foramen"
in

is often seen. The ''inferior gluteal line'' (inferior curved line), the least distinct of the three, begins in front at the notch on the anterior border, and, curving backward and downward, ends near the middle of the greater sciatic notch. The surface of bone included between the anterior and inferior gluteal lines is concave from above downward, convex from before backward, and gives origin to the

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 ...

. Between the inferior gluteal line and the upper part of the acetabulum is a rough, shallow groove, from which the reflected tendon of the

rectus femoris The rectus femoris muscle is one of the four quadriceps muscles of the human body. The others are the vastus medialis, the vastus intermedius (deep to the rectus femoris), and the vastus lateralis. All four parts of the quadriceps muscle attach to ...

arises.

Internal surface of the ala

The internal surface of the ala is bounded above by the crest, below, by the arcuate line; in front and behind, by the anterior and posterior borders. It presents a large, smooth, concave surface, called the iliac fossa, which gives origin to the

Iliacus The iliacus is a flat, triangular muscle which fills the iliac fossa. It forms the lateral portion of iliopsoas, providing flexion of the thigh and lower limb at the acetabulofemoral joint. Structure The iliacus arises from the iliac fossa on ...

and is perforated at its inner part by a nutrient canal; and below this a smooth, rounded border, the arcuate line, which runs downward, forward, and medialward. Behind the iliac fossa is a rough surface, divided into two portions, an anterior and a posterior. The anterior surface (auricular surface), so called from its resemblance in shape to the ear, is coated with cartilage in the fresh state, and articulates with a similar surface on the side of the sacrum. The posterior portion, known as the iliac tuberosity, is elevated and rough, for the attachment of the

posterior sacroiliac ligaments The posterior sacroiliac ligament is situated in a deep depression between the sacrum and ilium behind; it is strong and forms the chief bond of union between the bones. It consists of numerous fasciculi, which pass between the bones in various d ...

and for the origins of the

Sacrospinalis 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 ...

and

Multifidus The multifidus (multifidus spinae : ''pl. multifidi'' ) muscle consists of a number of fleshy and tendinous fasciculi, which fill up the groove on either side of the spinous processes of the vertebrae, from the sacrum to the axis. While very thin ...

. Below and in front of the auricular surface is the preauricular sulcus, more commonly present and better marked in the female than in the male; to it is attached the pelvic portion of the

anterior sacroiliac ligament The anterior sacroiliac ligament consists of numerous thin bands, which connect the anterior surface of the lateral part of the sacrum to the margin of the auricular surface of the ilium and to the preauricular sulcus. See also *Posterior sacroi ...

Crest of the ilium

The crest of the ilium is convex in its general outline but is sinuously curved, being concave inward in front, concave outward behind. It is thinner at the center than at the extremities, and ends in the anterior and posterior superior iliac spines. The surface of the crest is broad, and divided into external and internal lips, and an intermediate line. About 5 cm behind 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 ...

there is a prominent

tubercle In anatomy, a tubercle (literally 'small tuber', Latin for 'lump') is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal. In plants A tubercle is generally a wart-like projection ...

on the outer lip. To the external lip are attached the Tensor fasciæ latæ, Obliquus externus abdominis, and

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 ...

, and along its whole length the

fascia lata The fascia lata is the deep fascia of the thigh. It encloses the thigh muscles and forms the outer limit of the fascial compartments of thigh, which are internally separated by the medial intermuscular septum and the lateral intermuscular septu ...

; to the intermediate line the Obliquus internus abdominis; to the internal lip, the fascia iliaca, the

Transversus abdominis 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 ...

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 ...

, and

Anterior border of the ala

The anterior border of the ala is concave. It presents two projections, separated by a notch. Of these, the uppermost, situated at the junction of the crest and anterior border, is called the

; its outer border gives attachment to the

, and the Tensor fasciæ latæ, its inner border, to the Iliacus; while its extremity affords attachment to 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 ...

and gives origin to the sartorius Beneath this eminence is a notch from which the Sartorius takes origin and across which the lateral femoral cutaneous nerve passes. Below the notch is the

anterior inferior iliac spine 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 ...

, which ends in the upper lip of the acetabulum; it gives attachment to the straight tendon of the

Rectus femoris The rectus femoris muscle is one of the four quadriceps muscles of the human body. The others are the vastus medialis, the vastus intermedius (deep to the rectus femoris), and the vastus lateralis. All four parts of the quadriceps muscle attach to ...

and to the

iliofemoral ligament 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 ...

of the

hip-joint 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 ...

. Medial to the anterior inferior spine is a broad, shallow groove, over which the

and

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 ...

pass. This groove is bounded medially by an eminence, the iliopectineal eminence, which marks the point of union of the ilium and pubis.

Posterior border of the ala

The posterior border of the ala, shorter than the anterior, also presents two projections separated by a notch, the

posterior superior iliac spine The posterior border of the ala, shorter than the anterior, also presents two projections separated by a notch, the posterior superior iliac spine and the posterior inferior iliac spine. The posterior superior iliac spine serves for the attachment ...

and the

posterior inferior iliac spine The posterior inferior iliac spine (Sweeney's Tubercle) is an anatomical landmark that describes a bony "spine", or projection, at the posterior and inferior surface of the iliac bone. It is one of two such spines on the posterior surface, the o ...

. The former serves for the attachment of the oblique portion of the

and the

; the latter corresponds with the posterior extremity of the auricular surface. Below the posterior inferior spine is a deep notch, the greater sciatic notch.

References

External links

photo at nih.gov
{{Authority control Skeletal system Bones of the pelvis Ilium (bone)