Skeletal System: Structure, Features, and Movements – Study Guide

Skeletal System: Structure, Features, and Movements

Part 1: Bone Structure and Skull

This section introduces the fundamental structures of bones and the skull, focusing on both macroscopic and microscopic anatomy.

• Major Structures of a Long Bone: Long bones (e.g., femur, humerus) have distinct regions: the diaphysis (shaft), epiphyses (ends), metaphysis (growth plate region), medullary cavity (marrow cavity), and periosteum (outer covering).

• Microscopic Bone Structure: Compact bone is organized into osteons (Haversian systems), with concentric lamellae surrounding a central canal. Spongy bone contains trabeculae and houses red bone marrow.

• Cranial Bones: The skull is composed of several bones including the frontal, parietal, temporal, occipital, sphenoid, and ethmoid bones.

Example: The femur is a classic example of a long bone, with a thick diaphysis and expanded epiphyses for articulation.

Part 2: Vertebral Column and Thoracic Cage

This section covers the anatomy of the vertebral column and thoracic cage, including the identification and comparison of different vertebrae and associated structures.

• Bones and Features of the Vertebral Column: The vertebral column consists of cervical (7), thoracic (12), lumbar (5), sacral (5, fused), and coccygeal (4, fused) vertebrae.

• Atlas and Axis: The first cervical vertebra (atlas) supports the skull; the second (axis) allows head rotation via the dens (odontoid process).

• Comparing Vertebrae: Cervical vertebrae have transverse foramina; thoracic vertebrae have costal facets for rib articulation; lumbar vertebrae are larger and more robust.

• Coccyx and Sacrum: The sacrum is a triangular bone formed by fused sacral vertebrae; the coccyx (tailbone) is formed by fused coccygeal vertebrae.

• Thoracic Cage Features: Includes the sternum, ribs (true, false, floating), and clavicle.

Example: The atlas (C1) lacks a vertebral body and allows the nodding motion of the head.

Part 3: Pectoral Girdle and Upper Limb

This section details the bones and features of the shoulder and upper limb, including the pectoral girdle, arm, forearm, and hand.

• Shoulder and Upper Limb: The pectoral girdle consists of the clavicle and scapula.

• Scapula: Features include the spine, acromion, coracoid process, and glenoid cavity.

• Humerus: The upper arm bone, with features such as the head, greater and lesser tubercles, and olecranon fossa.

• Radius and Ulna: Forearm bones; the radius is lateral (thumb side), the ulna is medial (pinky side).

• Hand: Composed of carpals (wrist), metacarpals (palm), and phalanges (fingers).

Example: The glenoid cavity of the scapula articulates with the head of the humerus to form the shoulder joint.

Part 4: Pelvic Girdle and Lower Limb

This section explores the bones of the pelvis and lower limb, including the hip, thigh, leg, and foot.

• Pelvis: Formed by the fusion of the ilium, ischium, and pubis.

• Hip Bone and Pelvis: The acetabulum is the socket for the femoral head; the pelvic brim separates the true and false pelvis.

• Femur: The longest bone in the body, with features such as the head, neck, greater and lesser trochanters, and condyles.

• Lower Leg and Knee: The tibia (medial, weight-bearing) and fibula (lateral, slender) form the lower leg; the patella (kneecap) protects the knee joint.

• Foot: Composed of tarsals (ankle), metatarsals (foot), and phalanges (toes).

Example: The femoral head articulates with the acetabulum to form the hip joint.

Part 5: Movements

This section (not detailed in the file) likely covers the types of movements possible at synovial joints, such as flexion, extension, abduction, adduction, rotation, and circumduction.

• Flexion and Extension: Decreasing or increasing the angle between two bones.

• Abduction and Adduction: Movement away from or toward the midline.

• Rotation: Movement around a longitudinal axis.

• Circumduction: Circular movement combining flexion, extension, abduction, and adduction.

Example: The shoulder joint allows circumduction, enabling the arm to move in a circular motion.

Additional info:

• Where specific figures or images are referenced (e.g., Fig 12.1), students should consult their textbook or course materials for detailed diagrams.

• Comparative tables of vertebrae and bone features are commonly used for identification and should be reviewed in the relevant textbook chapters.