Anatomy study note · Pelvis

Sacrum

Five fused sacral vertebrae forming a wedge-shaped bone, concave in front, that carries the weight of the trunk to the hip bones at the sacroiliac joints.

Key points

• 5 fused vertebrae; promontory = back of the pelvic inlet.
• 4 pairs of anterior + posterior sacral foramina.
• Subarachnoid space ends at S2.
• Sacral hiatus → caudal anaesthesia.
• Female sacrum: shorter, wider, flatter.
• Lumbarization of S1.
• Vertebra = caudal half of one sclerotome + cranial half of the next.
• Bone: type I collagen + hydroxyapatite.
• Osteoblast builds, osteocyte maintains, osteoclast resorbs.

The full note in the atlas also covers

Features · Articulations · Histology · Development · Clinical notes

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Written from

• Snell’s Clinical Anatomy by Regions, 10th ed., ch. 8, PDF pp. 1018–1020, 1030–1032, 1049–1050
• Inderbir Singh’s Human Embryology, ch. 10, PDF pp. 134–137, 137–138
• BRS Cell Biology & Histology, 7th ed., ch. 7, PDF pp. 121–125, 130

More from the pelvis

• Seminal vesicle
• Sigmoid colon
• Urinary bladder
• Uterine artery
• Uterine tube
• Uterus
• Vagina
• Coccygeus
• Coccyx
• Hip bone
• Internal iliac artery
• Internal iliac vein

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