Editing Acetabulum (section)

==Structure==
There are three bones of the ''os coxae'' (hip bone) that come together to form the ''acetabulum''. Contributing a little more than two-fifths of the structure is the [[ischium]], which provides lower and side boundaries to the acetabulum. The [[Ilium (bone)|ilium]] forms the upper boundary, providing a little less than two-fifths of the structure of the acetabulum. The rest is formed by the [[Pubis (bone)|pubis]], near the midline.

It is bounded by a prominent uneven rim, thick and strong on top, which serves as the point of attachment for the [[acetabular labrum]]. The acetabular labrum reduces the size of the opening of the acetabulum and deepens the surface of the hip joint. At the lower part of the acetabulum is the [[acetabular notch]], which is continuous with a circular depression, the acetabular [[Fossa (anatomy)|fossa]], at the bottom of the cavity of the acetabulum. The rest of the acetabulum is formed by a curved, crescent-moon shaped surface, the [[lunate]] surface, where the joint is made with the [[femur head|head of the femur]]. Its counterpart in the pectoral girdle is the [[glenoid cavity|glenoid fossa]].<ref>{{cite journal |author= Petersilge C |title= Imaging of the acetabular labrum |year = 2005| journal= Magn Reson Imaging Clin N Am |volume=13 |issue=4 |pages = 641–52 |pmid= 16275573 |doi=10.1016/j.mric.2005.08.015 }}</ref>

The acetabulum is also home to the acetabular fossa, an attachment site for the ''ligamentum teres'', a triangular, somewhat flattened band implanted by its apex into the antero-superior part of the [[Femoral head|fovea capitis femoris]].  The notch is converted into a foramen by the transverse acetabular ligament; through the foramen nutrient vessels and nerves enter the joint. This is what holds the head of the femur securely in the acetabulum.<ref name=fie/>

The well-fitting surfaces of the femoral head and acetabulum, which face each other, are lined with a layer of slippery tissue called [[articular cartilage]], which is lubricated by a thin film of [[synovial fluid]]. Friction inside a normal hip is less than one-tenth that of ice gliding on ice.<ref>{{cite web |author=Balakumar J |title=Hip Dysplasia in the Child, Adolescent and Adult |url=http://www.jitbalakumar.com.au/hip-conditions/?Name=Value |work=jitbalakumar.com.au |access-date=2013-06-08 |url-status=dead |archive-url=https://web.archive.org/web/20130425155346/http://www.jitbalakumar.com.au/hip-conditions/?Name=Value |archive-date=2013-04-25 }}</ref><ref>{{cite web |author= OrthoInfo |title= Femoroacetabular Impingement (FAI) |url= http://orthoinfo.aaos.org/topic.cfm?topic=A00571|date=September 2010 |work= orthoinfo.aaos.org |publisher= the American Academy of Orthopaedic Surgeons |access-date=2013-06-08}}</ref>

===Blood supply===
The acetabular branch of the obturator artery supplies the ''acetabulum'' through the acetabular notch. The pubic branches supply the pelvic surface of the ''acetabulum''. Deep branches of the superior gluteal artery supply the superior region and the inferior gluteal artery supplies the postero-inferior region.<ref>{{cite journal |vauthors=Itokazu M, Takahashi K, Matsunaga T, Hayakawa D, Emura S, Isono H, Shoumura S |title= A study of the arterial supply of the human acetabulum using a corrosion casting method |year = 1997 |journal= Clin Anat |volume= 10 |issue= 2 |pages = 77–81 |pmid= 9058012 |doi= 10.1002/(SICI)1098-2353(1997)10:2<77::AID-CA1>3.0.CO;2-Q}}</ref>

===Reptiles and birds===
[[File:Ornithischia pelvis structure.svg|thumb|200px|right|An example of a perforated ''acetabulum'' on an [[ornithischian|ornithischian dinosaur]]]]
In [[reptiles]] and [[birds]], the ''acetabula'' are deep sockets. Organisms in the [[dinosauria]] clade are defined by a perforate ''acetabulum'', which can be thought of as a "hip-socket". The perforate ''acetabulum'' is a cup-shaped opening on each side of the pelvic girdle formed where the [[Ischium#In dinosaurs|ischium]], [[Ilium bone#In dinosaurs|ilium]], and [[pubis (bone)#Dinosaurs|pubis]] all meet, and into which the head of the femur inserts.<ref>Martin, A.J. (2006). Introduction to the Study of Dinosaurs. Second Edition. Oxford, Blackwell Publishing. pp. 299–300. {{ISBN|1-4051-3413-5}}.</ref><ref name="UC Berkeley Journal of Earth Sciences">{{cite web |last=Smith |first=Dave |title=Dinosauria: Morphology |url=http://www.ucmp.berkeley.edu/diapsids/audinosaur.html |publisher=UC Berkeley |access-date=21 January 2013 |archive-url=https://web.archive.org/web/20121022145110/http://www.ucmp.berkeley.edu/diapsids/audinosaur.html |archive-date=22 October 2012 |url-status=dead}}</ref> 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. In a relatively small number of dinosaurs, particularly [[ankylosaurian]]s (e.g. ''[[Texasetes]] pleurohalio''), an imperforate ''acetabulum'' is present, which is not an opening, but instead resembles a shallow concave depression on each side of the pelvic girdle.