Anatomy & Physiology Study Guide: Integumentary, Skeletal, and Muscular Systems

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

Cell Types: Includes keratinocytes (produce keratin), melanocytes (produce melanin), Langerhans cells (immune defense), and Merkel cells (sensory receptors).
Layers of the Epidermis: From deep to superficial: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum (only in thick skin), and stratum corneum.
Functions: Protection, sensation, thermoregulation, and synthesis of vitamin D.

The dermis lies beneath the epidermis and provides structural support and nourishment to the skin.

Layers: Papillary layer (loose connective tissue, contains capillaries and sensory neurons) and reticular layer (dense irregular connective tissue, provides strength and elasticity).
Structures: Blood vessels, nerves, hair follicles, sebaceous (oil) glands, and sweat glands.
Functions: Supports epidermis, thermoregulation, sensation, and immune defense.

Hair growth and skin color are determined by genetic and environmental factors.

Hair Growth: Occurs in cycles: anagen (growth), catagen (regression), and telogen (resting).
Factors Affecting Skin Color: Amount and type of melanin, carotene, and hemoglobin in the skin.

The skin contains several types of glands, each with unique roles.

Types of Sweat Glands: Eccrine (thermoregulation), apocrine (associated with hair follicles, active after puberty).
Sebaceous Glands: Secrete sebum (oil) to lubricate skin and hair.
Functions of Skin: Protection, sensation, excretion, thermoregulation, and vitamin D synthesis.

Types of Skin Cancer: Basal cell carcinoma, squamous cell carcinoma, and melanoma.
Cell Types Affected: Basal cells, squamous cells, melanocytes.
Classification: Based on cell of origin and malignancy.
Skin Changes with Age: Thinning, decreased elasticity, slower healing, and reduced gland activity.

The skeletal system includes various types of cartilage and bones, each with specific locations and functions.

Types of Cartilage: Hyaline (most common, found in joints), elastic (ear, epiglottis), fibrocartilage (intervertebral discs, menisci).
Functions of Bone: Support, protection, movement, mineral storage, blood cell formation (hematopoiesis), and energy storage.
Long Bone Anatomy: Diaphysis (shaft), epiphyses (ends), metaphysis, medullary cavity, periosteum, endosteum.

Organic Components: Collagen fibers and ground substance (provide flexibility).
Inorganic Components: Hydroxyapatite (calcium phosphate crystals, provide hardness).
Bone Classification: Long, short, flat, irregular, and sesamoid bones.

Intramembranous Ossification: Bone develops from fibrous membranes (e.g., flat bones of skull).
Endochondral Ossification: Bone forms by replacing hyaline cartilage (e.g., long bones).
Growth in Childhood/Adolescence: Occurs at epiphyseal plates via interstitial growth.
Hormonal Regulation: Growth hormone, thyroid hormone, and sex hormones regulate bone growth.

Bone Remodeling: Continuous process involving osteoblasts (build bone) and osteoclasts (break down bone).
Fracture Healing: Hematoma formation, fibrocartilaginous callus, bony callus, bone remodeling.
Osteomalacia/Rickets: Softening of bones due to vitamin D deficiency (rickets in children).
Osteoporosis: Decreased bone mass and increased fracture risk.

Joints, or articulations, are classified by structure and function.

Structural Classification: Fibrous (no joint cavity, e.g., sutures), cartilaginous (joined by cartilage, e.g., intervertebral discs), synovial (joint cavity, freely movable).
Functional Classification: Synarthroses (immovable), amphiarthroses (slightly movable), diarthroses (freely movable).

Features of Synovial Joints: Articular cartilage, joint cavity, synovial fluid, articular capsule, ligaments, nerves, and blood vessels.
Movements: Flexion, extension, abduction, adduction, rotation, circumduction.
Examples: Shoulder (ball-and-socket), elbow (hinge), knee (modified hinge).

Common Injuries: Sprains, dislocations, cartilage tears.
Joint Disorders: Bursitis (inflammation of bursae), tendinitis (inflammation of tendons), arthritis (joint inflammation).

Muscle tissue is classified into three types, each with distinct structure and function.

Skeletal Muscle: Voluntary, striated, attached to bones, responsible for movement.
Cardiac Muscle: Involuntary, striated, found in heart, responsible for pumping blood.
Smooth Muscle: Involuntary, non-striated, found in walls of hollow organs.

Connective Tissue Components: Epimysium (surrounds whole muscle), perimysium (surrounds fascicles), endomysium (surrounds muscle fibers).
Microscopic Anatomy: Muscle fibers contain myofibrils, which are composed of myofilaments (actin and myosin).
Sarcomere: Functional unit of muscle contraction, defined by Z-discs.
Sarcoplasmic Reticulum and T-tubules: Involved in calcium storage and transmission of action potentials.

Excitation-Contraction Coupling: Sequence of events from action potential to muscle contraction.
Neuromuscular Junction: Site where motor neuron stimulates muscle fiber.
Sliding Filament Theory: Myosin heads bind to actin, pulling filaments to shorten sarcomere.
ATP Role: Provides energy for contraction and relaxation.
Motor Unit: A motor neuron and all muscle fibers it innervates.
Muscle Twitch and Summation: Single contraction vs. increased force with rapid stimulation.
Muscle Fiber Types: Slow oxidative (endurance), fast oxidative (intermediate), fast glycolytic (power, fatigue quickly).
Response to Exercise: Hypertrophy, increased endurance, improved metabolic efficiency.

Fiber Type	Contraction Speed	Fatigue Resistance	Primary ATP Source	Example Activity
Slow Oxidative	Slow	High	Aerobic respiration	Marathon running
Fast Oxidative	Fast	Intermediate	Aerobic respiration	Middle-distance running
Fast Glycolytic	Fast	Low	Anaerobic glycolysis	Sprinting