SG

BIO 233 Lab 1: Inferior Appendicular Skeleton

  • Pelvic Girdle & Pelvis: Composed of ossa coxae (hip bones) and sacrum, forming a structure that transfers weight from the spine to lower limbs via the pubic symphysis and sacroiliac joints. It is divided into the greater (false) and lesser (true) pelvis. Notable sex differences exist, with females exhibiting a wider pubic angle and a rounder pelvic outlet for childbirth, contrasting with the narrower pubic angle in males. The pubic angle is a quick indicator for sex differentiation.

  • Os Coxae (Hip Bone): Each os coxae is formed by the fusion of three bones: the ilium, ischium, and pubis. The acetabulum is the hip socket for femoral articulation.

    • Ilium: Features include the iliac crest, anterior/posterior superior and inferior iliac spines (ASIS, AIIS, PSIS, PIIS), greater sciatic notch, iliac fossa, and auricular surface.

    • Ischium: Key landmarks are the ischial spine, lesser sciatic notch, ischial tuberosity (weight-bearing when sitting), and the obturator foramen.

    • Pubis: Comprises superior and inferior rami, and the pubic symphysis at its medial aspect.

  • Femur: The proximal end includes the head (articulates with the acetabulum) with a fovea capitis, neck, and greater/lesser trochanters. The shaft features the prominent linea aspera posteriorly. Distally, it presents medial/lateral condyles (for the knee joint), epicondyles, an intercondylar fossa, and a patellar surface.

  • Patella (Kneecap): Consists of a base, apex, and articular facets on its posterior aspect.

  • Tibia (Shin Bone): The primary weight-bearing bone of the lower leg. It has proximal medial/lateral condyles (tibial plateau) and a tibial tuberosity. Distally, it forms the medial malleolus (inner ankle) and an inferior articular surface for the talus.

  • Fibula: Non-weight-bearing, located laterally. Features include a head proximally and the lateral malleolus distally (outer ankle bulge).

  • Foot Bones: Divided into tarsals, metatarsals, and phalanges.

    • Tarsals (ankle bones): Include the talus, calcaneus (heel bone), navicular, cuboid, and three cuneiform bones.

    • Metatarsals: Five bones (I to V).

    • Phalanges (toes): There are 14 phalanges per foot. The hallux (big toe, digit I) has two phalanges (proximal and distal), while digits II-V each have three (proximal, intermediate, and distal).