The Appendicular Skeleton

The Appendicular Skeleton

Introduction to the Appendicular Skeleton

  • The human body contains a total of 206 bones in adults.

  • The skeletal system is divided into two major parts: Axial Skeleton and Appendicular Skeleton.

Components of the Skeleton

Appendicular Skeleton Components:

  • Human Skeleton Structures:

  • Clavicle (Collarbone)

  • Scapula (Shoulder blade)

  • Sternum (Breastbone)

  • Ribs

  • Humerus (Upper arm bone)

  • Vertebrae (Spinal column)

  • Coxal Bone (Hip bone)

  • Sacrum

  • Femur (Thigh bone)

  • Patella (Kneecap)

  • Tibia (Shin bone)

  • Fibula (Calf bone)

Appendicular Skeleton

  • Purpose: Supports limbs involved in locomotion.

  • Comprises two girdles: Pectoral Girdle and Pelvic Girdle, which articulate limbs with the axial skeleton.

  • Contains varying degrees of hemopoietic tissue compared to the axial skeleton.

Pectoral Girdle

  • Made up of 2 bones on each side: Clavicle and Scapula.

  • Attachment:

    • One attachment to the axial skeleton (at the sternum).

  • Articulation:

    • Provides a shallow articulation with the humerus.

  • Motion:

    • Allows for a wide range of motion for the arms.

Pelvic Girdle

  • Composed of one single bone (the coxal bone).

  • Attachment:

    • One stronger attachment to the axial skeleton (at the sacrum).

  • Motion:

    • Provides a narrower range of motion in the hips than the pectoral girdle.

Humerus

  • Fossa: Indents that accept projections from other bones.

    • Types of Fossa in Humerus:

    • Coronoid Fossa

    • Radial Fossa

    • Olecranon Fossa

Proximal Radioulnar Joint

  • Joints between the radius and ulna at both the proximal and distal ends.

Elbow Joint

  • The processes of the ulna (e.g., olecranon process) fit into the corresponding fossa (olecranon fossa) when the arm is extended.

Radius and Ulna

  • Orientation: Ulna is located medially (associated with the pinky), while the radius is lateral (associated with the thumb).

  • Articulation at two points: proximal and distal.

  • Joints allow for rotation of the forearm from supination (palm up) to pronation (palm down).

Wrist Joint

  • The radius articulates with the scaphoid and lunate carpal bones.

  • The ulna articulates only with the lunate carpal bone.

  • Total number of carpals: 8 bones.

Pelvis Structure

  • Composed of 4 bones:

    • Os coxa (hip bones)

    • Sacrum

    • Coccyx

  • Pelvic Outlet:

    • Outlined by the coccyx tip, ischial spines, and pubic symphysis; significant in childbirth.

  • Pelvic Inlet:

    • Ranges from the top of the sacrum to the top of the pubic symphysis.

Pelvic Cavity

  • Defined as the area:

    • True Pelvis: Situated deep to the pelvic inlet.

    • False Pelvis: Part of the abdominal cavity located superior to the pelvic inlet.

Determining Sex by the Pelvis

  • Differences in structure:

    • Sciatic Notch:

    • Males: Narrower sciatic notch.

    • Females: Wider greater sciatic notch.

    • Subpubic Angle:

    • Males: Narrower (approximately 90°).

    • Females: Wider (approximately 100°).

    • Ilium Orientation:

    • Males: Upright ilium.

    • Females: Flared ilium.

Bones of the Knee

  • Femur articulates with the patella (patellar surface) and tibia.

  • Note: The fibula does not articulate at the knee joint.

Tibia and Fibula

  • Key question regarding weight-bearing:

    • Which bone bears most of the weight? (The tibia bears most weight).

  • Ability to pronate and supinate at the distal and proximal joints.

Tarsals

  • Phalanges (toe bones):

    • Distal phalanx, Proximal phalanx, Middle phalanx of the hallux (great toe).

  • The tarsals include:

    • Talus: Articulates with tibia and fibula.

    • Other bones include:

    • Medial cuneiform

    • Intermediate cuneiform

    • Lateral cuneiform

    • Cuboid

    • Navicular

    • Calcaneus (heel bone).

Arches of the Foot

  1. Medial Longitudinal Arch: Extends from the hallux to the calcaneus.

  2. Lateral Longitudinal Arch: Extends from the pinky to the calcaneus.

  3. Transverse Arch: Spans the distal tarsals and metatarsals.

  • Support: The arches are maintained by bones as well as supporting ligaments and tendons.