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Pelvic inlet
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<h2 id="boundaries">Boundaries</h2> <p>The edge of the pelvic inlet (pelvic brim) is formed as follows: </p> <table><tbody><tr><td></td><td><i>Anteriorly</i>by the <a href="/facts/Pubic_crest/11MQpadK">pubic crest</a> (or <a href="/facts/Pubic_symphysis/voKAVNqB">pubic symphysis</a>)</td><td></td></tr><tr><td><i>Laterally</i>by the <a href="/facts/Iliopectineal_line/ln5vzRMP">iliopectineal line</a></td><td></td><td>(same as other side)</td></tr><tr><td></td><td><i>Posteriorly</i>by the anterior margin of the <a href="/facts/Base_of_the_sacrum/CTFnjSm0">base of the sacrum</a> (or the <a href="/facts/Ala_of_sacrum/CTFnjSm0">ala of sacrum</a>) and <a href="/facts/Sacrovertebral_angle/afQtHYnx">sacrovertebral angle</a> (or <a href="/facts/Sacral_promontory/CTFnjSm0">sacral promontory</a>)</td><td></td></tr></tbody></table> <h2 id="diameters">Diameters</h2> <p>The diameters or conjugates of the pelvis are measured at the pelvic inlet and outlet and as oblique diameters. </p> <table><tbody><tr><th>Name</th><th>Description</th><th>Average measurement in female</th></tr><tr><td><i>Anteroposterior</i> or <i>conjugate</i> diameter or <i>conjugata vera</i></td><td>Extends from the upper margin of the <a href="/facts/Pubic_symphysis/voKAVNqB">pubic symphysis</a> to the sacrococcygeal joint;</td><td>about 110 mm.</td></tr><tr><td><i>Transverse diameter</i></td><td>Extends across the greatest width of the superior aperture, from the middle of the brim on one side to the same point on the opposite;</td><td>about 135 mm.</td></tr><tr><td><i>Oblique diameter</i></td><td>Extends from the iliopectineal eminence of one side to the <a href="/facts/Sacroiliac/XgpSo3YP">sacroiliac</a> articulation of the opposite side;</td><td>about 125 mm.</td></tr><tr><td><i>Anatomical conjugate</i></td><td>Extends from the <a href="/facts/Pubic_symphysis/voKAVNqB">pubic symphysis</a> to the promontory;</td><td>about 120 mm.</td></tr><tr><td><i>Diagonal conjugate</i></td><td>Extends from lower margin of the pubic symphysis to the sacral promontory;</td><td>about 130 mm.</td></tr><tr><td><i>Straight conjugate</i></td><td>Extends from the lower border of the <a href="/facts/Pubic_symphysis/voKAVNqB">pubic symphysis</a> to the tip of <a href="/facts/Coccyx/BQ2qjXwg">coccyx</a>. The <a href="/facts/Coccyx/BQ2qjXwg">coccyx</a> can bend posteriorly and expand the diameter with 25 mm;</td><td>about 95 mm (+ 25 mm).</td></tr><tr><td><i>Median conjugate</i></td><td>Extends from the lower border of the <a href="/facts/Pubic_symphysis/voKAVNqB">pubic symphysis</a> to the lower border of the <a href="/facts/Sacrum/CTFnjSm0">sacrum</a>;</td><td>about 115 mm.</td></tr></tbody></table> <p>Two diameters may be measured from the outside of the body using a <a href="/facts/Pelvimetry/ttumDjYC">pelvimeter</a> </p> <table><tbody><tr><th>Name</th><th>Description</th><th>Average measurement in female</th></tr><tr><td><i>Interspinous distance</i></td><td>Extends between the anterior superior iliac spines;</td><td>about 260 mm.</td></tr><tr><td><i>Intercristal distance</i></td><td>Extends between the furthest later points of the two iliac crests;</td><td>about 290 mm.</td></tr></tbody></table> <h2 id="additional-images">Additional images</h2> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Pelvic_outlet/f3t1wUYM">Pelvic outlet</a></li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="http://www.wesnorman.com/pelvis.htm">pelvis</a> at The Anatomy Lesson by Wesley Norman (Georgetown University) (<i><a href="http://www.wesnorman.com/Images/medialpelvissmall.jpg">medialpelvissmall</a></i>, <i><a href="http://www.wesnorman.com/Images/malepelvissagittalinlet&outletsml.jpg">malepelvissagittalinlet&outletsml</a></i>)</li></ul>