Anatomy & Physiology Study Guide: Skin, Bones, Joints, and Muscles

Chapter 5: The Integumentary System

Cell Types and Layers of the Epidermis

The epidermis is the outermost layer of the skin, composed of several cell types and layers, each with distinct functions.

• Keratinocytes: Main cells producing keratin, a protein that provides strength and waterproofing.

• Melanocytes: Cells that produce melanin, the pigment responsible for skin color.

• Langerhans cells: Immune cells involved in defense against pathogens.

• Merkel cells: Sensory cells associated with touch.

The layers of the epidermis (from deep to superficial):

• Stratum basale: Deepest layer, site of cell division.

• Stratum spinosum: Provides strength and flexibility.

• Stratum granulosum: Cells begin to die and keratinize.

• Stratum lucidum: Present only in thick skin (palms, soles).

• Stratum corneum: Outermost layer, composed of dead, keratinized cells.

Dermis Structure and Functions

The dermis lies beneath the epidermis and contains connective tissue, blood vessels, nerves, and accessory structures.

• Papillary layer: Superficial, contains capillaries and sensory receptors.

• Reticular layer: Deep, contains collagen and elastin fibers for strength and elasticity.

Hair and Growth

Hair is produced by follicles in the dermis and grows in cycles.

• Anagen phase: Active growth.

• Catagen phase: Transitional phase.

• Telogen phase: Resting phase.

Skin Color and Glands

Skin color is determined by melanin, hemoglobin, and carotene. Glands in the skin include:

• Sebaceous glands: Produce sebum (oil).

• Sudoriferous glands: Produce sweat; include eccrine and apocrine types.

Functions of Skin

• Protection against pathogens and injury

• Regulation of body temperature

• Sensation

• Excretion of wastes

• Synthesis of vitamin D

Skin Cancer and Aging

• Types of skin cancer: Basal cell carcinoma, squamous cell carcinoma, melanoma.

• Classification: Based on cell type and behavior.

• Aging: Skin becomes thinner, less elastic, and more prone to damage.

Chapter 6: The Skeletal System

Skeletal Cartilages and Bone Structure

Cartilage is a flexible connective tissue found in joints, ear, nose, and respiratory tract.

• Types: Hyaline, elastic, and fibrocartilage.

• Features: Chondrocytes in lacunae, avascular, surrounded by perichondrium.

Bones are classified by shape: long, short, flat, irregular, and sesamoid.

Functions of Bone

• Support and protection

• Movement (leverage for muscles)

• Mineral storage (calcium, phosphate)

• Blood cell formation (hematopoiesis)

• Triglyceride storage

Bone Formation and Growth

• Intramembranous ossification: Formation of flat bones from mesenchymal tissue.

• Endochondral ossification: Formation of long bones from cartilage models.

Bone Remodeling and Repair

• Bone is constantly remodeled by osteoblasts (build bone) and osteoclasts (break down bone).

• Hormones such as growth hormone, parathyroid hormone, and calcitonin regulate bone growth and remodeling.

• Fracture healing involves hematoma formation, fibrocartilaginous callus, bony callus, and bone remodeling.

Bone Disorders

• Osteomalacia/rickets: Softening of bones due to vitamin D deficiency.

• Osteoporosis: Decreased bone mass and increased fracture risk.

Chapter 7: Joints

Classification and Types of Joints

Joints (articulations) are classified by structure and function.

• Fibrous joints: Bones joined by dense connective tissue; little or no movement (e.g., sutures).

• Cartilaginous joints: Bones joined by cartilage; limited movement (e.g., intervertebral discs).

• Synovial joints: Bones separated by a fluid-filled cavity; freely movable (e.g., knee, shoulder).

Features and Movements of Synovial Joints

• Articular cartilage, joint cavity, synovial fluid, ligaments, nerves, and blood vessels.

• Movements: flexion, extension, abduction, adduction, rotation, circumduction.

Joint Injuries and Disorders

• Common injuries: Sprains, dislocations, torn cartilage.

• Joint disorders: Bursitis (inflammation of bursae), tendinitis (inflammation of tendons), arthritis.

Chapter 9: Muscular System

Types and Characteristics of Muscle

Muscle tissue is classified into three types:

• Skeletal muscle: Voluntary, striated, attached to bones.

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

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

Muscle Structure and Function

• Muscle fibers are surrounded by connective tissues: endomysium, perimysium, epimysium.

• Gross anatomy includes fascicles, muscle fibers, myofibrils, and myofilaments (actin and myosin).

• Sarcoplasmic reticulum stores calcium; transverse tubules transmit action potentials.

Muscle Contraction

• Contraction is initiated at the neuromuscular junction by neurotransmitter release.

• Action potential leads to calcium release and interaction of actin and myosin (sliding filament theory).

• ATP is required for contraction and relaxation.

Muscle Fiber Types and Exercise

• Slow oxidative fibers: Fatigue-resistant, used for endurance.

• Fast oxidative fibers: Intermediate properties.

• Fast glycolytic fibers: Fatigue quickly, used for rapid, powerful movements.

• Muscle adapts to exercise by increasing size, strength, and endurance.

Key Equations

• Muscle force: $F = m \cdot a$

• ATP hydrolysis: $ATP \rightarrow ADP + P_i + \text{energy}$

Example Table: Comparison of Muscle Fiber Types

Fiber Type	Contraction Speed	Fatigue Resistance	Main Energy Source
Slow Oxidative	Slow	High	Aerobic respiration
Fast Oxidative	Fast	Intermediate	Aerobic respiration
Fast Glycolytic	Fast	Low	Anaerobic glycolysis