Skeletal System: Bones, Cartilage, Joints, and Vertebral Column Study Guide

Unit 6

Structure and Function of Bones and Cartilage

Tissue Types Forming Bone

The skeletal system is primarily composed of specialized connective tissues: bone and cartilage. Each plays a crucial role in support, movement, and protection.

• Bone Tissue: A rigid connective tissue containing cells (osteocytes) embedded in a mineralized matrix of collagen and hydroxyapatite.

• Cartilage Tissue: A flexible connective tissue with chondrocytes in a gel-like matrix, providing cushioning and structural support.

Six Types of Bones with Examples

Bones are classified by shape and function:

• Long Bones: Longer than they are wide (e.g., femur, humerus).

• Short Bones: Nearly equal in length and width (e.g., carpals, tarsals).

• Flat Bones: Thin and broad (e.g., sternum, scapula).

• Irregular Bones: Complex shapes (e.g., vertebrae, mandible).

• Sesamoid Bones: Embedded in tendons (e.g., patella).

• Sutural (Wormian) Bones: Small bones within cranial sutures.

Structure and Function of Long Bones

Long bones are essential for movement and support. Their structure includes:

• Diaphysis: Shaft providing strength and leverage.

• Epiphyses: Ends of the bone, involved in joint formation.

• Medullary Cavity: Central cavity containing bone marrow.

• Periosteum: Outer fibrous covering for protection and attachment.

• Endosteum: Lining of the medullary cavity.

Function: Long bones act as levers for movement, store minerals, and house marrow for blood cell production.

Major Divisions of the Skeleton

The human skeleton is divided into two main parts:

• Axial Skeleton: Includes the skull, vertebral column, and thoracic cage. Provides central support and protection.

• Appendicular Skeleton: Includes the limbs and girdles (pectoral and pelvic). Facilitates movement.

Types of Joints and Their Structure and Function

Three Major Types of Joints

• Fibrous Joints: Bones joined by dense connective tissue; immovable (e.g., sutures in the skull).

• Cartilaginous Joints: Bones connected by cartilage; slightly movable (e.g., intervertebral discs).

• Synovial Joints: Freely movable joints with a synovial cavity (e.g., shoulder, knee).

Degree of Movement of Synovial Joints

Synovial joints allow various movements:

• Gliding (e.g., wrist)

• Angular (flexion, extension, abduction, adduction)

• Rotation (e.g., atlas and axis)

• Special Movements (e.g., opposition of thumb)

Tendons vs. Ligaments

Tendons and ligaments are connective tissues with distinct roles:

• Tendon: Connects muscle to bone; transmits force for movement.

• Ligament: Connects bone to bone; stabilizes joints.

Vertebral Column: Structure and Differences

Sections of the Vertebral Column

The vertebral column consists of five regions:

• Cervical (7 vertebrae): Small, flexible, supports the head.

• Thoracic (12 vertebrae): Larger, articulate with ribs.

• Lumbar (5 vertebrae): Largest, support body weight.

• Sacral (5 fused vertebrae): Forms the sacrum.

• Coccygeal (4 fused vertebrae): Forms the coccyx.

Region	Number of Vertebrae	Key Features
Cervical	7	Small, transverse foramina
Thoracic	12	Articulate with ribs
Lumbar	5	Large, robust bodies
Sacral	5 (fused)	Forms sacrum
Coccygeal	4 (fused)	Forms coccyx

Intervertebral Disks: Characteristics and Functions

Intervertebral disks are fibrocartilaginous pads between vertebrae. They:

• Absorb shock and reduce impact during movement.

• Allow flexibility and slight movement of the spine.

• Consist of an outer annulus fibrosus and inner nucleus pulposus.

Shoulder Joint: Key Structures

The shoulder joint (glenohumeral joint) is a synovial ball-and-socket joint. Key structures include:

• Humeral head and glenoid cavity of scapula

• Articular cartilage

• Joint capsule and synovial membrane

• Ligaments (e.g., coracohumeral, glenohumeral)

• Rotator cuff muscles (supraspinatus, infraspinatus, teres minor, subscapularis)

Function: Provides a wide range of motion for the upper limb.