ch08 Appendicular Skeleton

Chapter Overview

  • Title: The Skeletal System: The Appendicular Skeleton

  • Edition: Principles of Anatomy and Physiology, 14th Edition

  • Copyright: © 2014 John Wiley & Sons, Inc.

The Appendicular Skeleton

  • Composed of 126 bones concerned primarily with movement.

  • These include:

    • Upper limbs

    • Lower limbs

    • Girdles attaching limbs to axial skeleton

Pectoral (Shoulder) Girdle

  • Composed of two girdles:

    • Clavicle (Collar Bone):

      • S-shaped, articulates medially with the manubrium of the sternum and laterally with the acromion of the scapula.

    • Scapula (Shoulder Blade):

      • Flat bone located in the upper part of the back, between the second and seventh ribs.

      • Glenoid cavity serves as the attachment point for the humerus (upper arm bone).

Upper Limb (Extremity)

  • Humerus:

    • Articulates with the scapula at the proximal end and with the radius and ulna at the distal end.

    • Key features: anatomical neck, greater/lesser tubercles, trochlea, capitulum.

  • Ulna and Radius:

    • Ulna:

      • Forms elbow joint with humerus (trochlear notch wraps around trochlea).

    • Radius:

      • Located on the thumb side, allows forearm rotation.

  • Carpals:

    • Eight small bones arranged in two rows (proximal and distal) articulate with the metacarpals (hand bones).

  • Metacarpals and Phalanges:

    • Five metacarpals form the palm, numbered I to V.

    • Fourteen phalanges (2 in thumb, 3 in each other finger).

Pelvic (Hip) Girdle

  • Comprised of two hip bones (os coxa) articulating with the sacrum.

  • Each hip bone consists of three fused components: ilium, ischium, and pubis.

  • Anteriorly articulates at pubic symphysis, a fibrocartilage disc joins them.

Differences Between Male and Female Pelvises

  • Male pelvis: usually larger and heavier, narrower, and designed for strength.

  • Female pelvis: wider and shallower to accommodate childbirth; differences include the pelvic inlet shape and pubic arch angles.

Lower Limb (Extremity)

  • Femur (Thighbone):

    • Longest and strongest bone, articulates with hip at acetabulum and tibia at knee joint.

  • Patella (Kneecap):

    • Triangular bone in anterior thigh, develops in the quadriceps tendon.

  • Tibia and Fibula:

    • Tibia articulates with femur and talus at the ankle; fibula supports the ankle laterally.

Tarsus (Ankle)

  • Contains 7 tarsal bones including talus and calcaneus; metatarsals make up the midfoot.

  • Phalanges structure similar to fingers.

Foot Mechanics

  • The foot features two arches:

    • Longitudinal arch: Composed of medial and lateral parts.

    • Transverse arch: Provides additional support.

Development of the Skeletal System

  • Derived from mesoderm with contributions from ectoderm for skull bones.

  • Distinct development paths:

    • Neurocranium: Cartilaginous and membranous components.

    • Viscerocranium: Forms facial bones via pharyngeal arches.

Role of the Skeletal System in Homeostasis

  • Supports and protects organ systems.

  • Aids in calcium storage and release critical for various body functions.

  • Protects internal organs and contributes to the movement and leverage of muscles.

  • Involved in blood cell production (hemopoiesis) via red bone marrow.