Chapter 6: Skeletal Tissues

Overview of Skeletal Tissues

The skeletal system is composed of specialized tissues that provide structure, protection, and support for the body. The two main types of tissues are bone and cartilage, each with distinct functions and properties.

• Bones: Rigid organs that form the skeleton, support movement, protect organs, and store minerals.

• Cartilage: Flexible connective tissue found in joints, ear, nose, and respiratory tract; provides cushioning and support.

Functions of the Skeletal System:

• Support and protection of vital organs

• Facilitation of movement

• Mineral storage (e.g., calcium, phosphorus)

• Blood cell production (hematopoiesis)

• Energy storage (yellow marrow)

Cartilage Types and Structure

Cartilage is classified into three types based on structure and location:

• Hyaline cartilage: Most common; found in nose, trachea, larynx, and at the ends of long bones.

• Elastic cartilage: Contains elastic fibers; found in ear and epiglottis.

• Fibrocartilage: Dense with collagen fibers; found in intervertebral discs and pubic symphysis.

Structure of Cartilage: Composed of chondrocytes embedded in a matrix of collagen and proteoglycans.

Bone Classification and Structure

Bones are classified by shape and composition:

• Shape: Long, short, flat, irregular, sesamoid

• Composition: Compact (dense) and spongy (cancellous)

Structure of a Long Bone:

• Diaphysis: Shaft

• Epiphysis: Ends

• Metaphysis: Region between diaphysis and epiphysis

• Medullary cavity: Central cavity containing marrow

• Periosteum: Outer membrane

• Endosteum: Inner membrane lining the medullary cavity

Bone Markings and Ossification

Bones have various markings (e.g., foramen, fossa, process) that serve as attachment points for muscles and passageways for nerves and blood vessels.

• Ossification: The process of bone formation, occurring via intramembranous or endochondral pathways.

• Intramembranous ossification: Direct formation from mesenchymal tissue (e.g., flat bones of skull).

• Endochondral ossification: Bone develops by replacing hyaline cartilage (e.g., long bones).

Bone Remodeling and Homeostasis

Bone tissue is constantly remodeled through the actions of osteoblasts (bone formation) and osteoclasts (bone resorption).

• Hormonal regulation: Parathyroid hormone (PTH) increases blood calcium by stimulating osteoclasts; calcitonin lowers blood calcium by inhibiting osteoclasts.

• Vitamin D: Essential for calcium absorption and bone health.

Fractures and Bone Repair

Fractures are breaks in bone continuity and are classified by their pattern and severity.

• Types of fractures: Open, closed, comminuted, greenstick, spiral, depressed, impacted.

• Bone repair: Involves hematoma formation, fibrocartilaginous callus formation, bony callus formation, and bone remodeling.

Table: Types of Bone Fractures

Chapter 8: Joints

Overview of Joints

Joints, or articulations, are sites where two or more bones meet, allowing for movement and flexibility in the skeleton.

• Classification by structure: Fibrous, cartilaginous, synovial

• Classification by function: Synarthrosis (immovable), amphiarthrosis (slightly movable), diarthrosis (freely movable)

Synovial Joints

Synovial joints are the most movable type of joint and are characterized by a fluid-filled joint cavity.

• Components: Articular cartilage, joint capsule, synovial fluid, ligaments, bursae

• Types: Ball-and-socket, hinge, pivot, saddle, plane, condyloid

Joint Movements

Joints allow for various types of movement, classified as follows:

• Gliding

• Flexion/Extension

• Abduction/Adduction

• Rotation

• Supination/Pronation

• Dorsiflexion/Plantar flexion

• Eversion/Inversion

Table: Types of Synovial Joints and Movements

Chapter 10: Muscle Tissue

Types and Characteristics of Muscle Tissue

Muscle tissue is specialized for contraction and is classified into three types:

• Skeletal muscle: Voluntary, striated, attached to bones for movement

• Cardiac muscle: Involuntary, striated, found in the heart

• Smooth muscle: Involuntary, non-striated, found in walls of hollow organs

Functions of Muscle Tissue:

• Movement

• Posture maintenance

• Joint stabilization

• Heat generation

Muscle Structure and Contraction

Muscle fibers are composed of myofibrils, which contain sarcomeres—the basic contractile units.

• Sarcomere: Segment between two Z lines; contains actin (thin) and myosin (thick) filaments.

• Sliding filament model: Muscle contraction occurs as actin and myosin filaments slide past each other.

Equation for Muscle Contraction:

Muscle Excitation and Action Potentials

Muscle contraction is initiated by an action potential, which triggers the release of calcium ions and the interaction of actin and myosin.

• Resting membrane potential: Difference in charge across the muscle cell membrane.

• Action potential: Rapid change in membrane potential that leads to contraction.

Steps of Excitation-Contraction Coupling:

1. Action potential arrives at neuromuscular junction.

2. Release of acetylcholine.

3. Depolarization of muscle fiber membrane.

4. Release of calcium from sarcoplasmic reticulum.

5. Calcium binds to troponin, exposing binding sites on actin.

6. Myosin binds to actin, initiating contraction.

Muscle Metabolism and Fatigue

Muscle cells generate ATP through aerobic and anaerobic pathways. Fatigue occurs when ATP supply cannot meet demand.

• Aerobic respiration: Uses oxygen, produces more ATP, slower process.

• Anaerobic respiration: Does not require oxygen, produces less ATP, faster process.

• Creatine phosphate: Provides rapid ATP regeneration.

Equation for ATP Production:

Table: Types of Muscle Fibers

Muscle Growth and Repair

Muscle growth occurs via hypertrophy (increase in fiber size) and, to a limited extent, hyperplasia (increase in fiber number). Repair involves satellite cells and is limited in adults.

• Satellite cells: Stem cells involved in muscle repair.

• Hormonal regulation: Growth hormone and testosterone promote muscle growth.

Additional info:

• Some questions in the original file refer to clinical applications, such as osteoporosis, muscle dystrophy, and rehabilitation, which are important for understanding pathology and treatment in anatomy and physiology.