Functions of pelvis

1. Protects pelvic viscera
2. Supports weight of body
3. Provides attachment foir muscles
4. Supports birth canal in female 

Components

• All 3 bones fuse at acetabulum "vinegar cup" which forms socket for femoral head
• Pelvis tiled in erect position so that plane of inlet is at an angle of 60' to the horizontal

1. Os innominatum
   • Ilium
   • Ischium
   • Pubis
2. Sacrum
3. Coccyx

Ligaments and Joints of the Pelvis

1. Symphysis pubis -
   • cartilaginous joint between pubic bones
   • Pubic bone covered by layer of hyaline cartilage
2. Sacroiliac joints
   • Articulations between auricular surfaces of sacrum and ilium on each side
   • Synovial joints
   • Held together by anterior + posterior sacroiliac ligaments (the strongest ligaments in the body)
3. Sacrotuberous / sacrospinal ligaments
   • Form lesser and greater sciatic foramen

Sacrum

• Made up of 5 fused vertebrae, roughly triangular
• Anterior border = sacral promotry
• Anterior aspect: central mass + 4 anterior sacral foramina (transmits 4 upper sacral anterior primary rami)
• Lateral masses of sacrum forms fan-shaped "ala"
• Posteriorly: sacral canal (continuation of vertebral canal) terminates at sacral hiatus + 4 posterior sacral foramina

Coccyx

• Made up of 3-5 fused vertebrae
• Represents tail of primitive animals