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.