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

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Chapter 4: The Integumentary System

Overview of Epithelial Membranes

The body is covered and lined by various epithelial membranes, each with distinct structures and functions. Understanding these membranes is essential for recognizing how the body protects itself and maintains homeostasis.

Cutaneous membrane: Commonly known as the skin, it covers the body surface and consists of epidermis and dermis.
Mucous membranes: Line body cavities open to the exterior (e.g., digestive, respiratory tracts); secrete mucus for protection and lubrication.
Serous membranes: Line closed internal body cavities (e.g., thoracic, abdominal); secrete serous fluid to reduce friction.

Key structures:

Location: Skin (external), mucous (internal passages), serous (internal cavities).
Synovial membranes: Line joint cavities; produce synovial fluid for lubrication.

Functions and Structure of the Skin

The skin is the largest organ of the body and forms the integumentary system, which includes skin and its appendages (hair, nails, glands).

Protection: Acts as a barrier against pathogens, chemicals, and physical injury.
Regulation: Maintains body temperature and water balance.
Sensation: Contains sensory receptors for touch, pain, and temperature.
Excretion: Removes waste products via sweat.

Layers and Composition of the Skin

The skin consists of three main layers, each with unique functions and cell types.

Epidermis: Outermost layer; composed of stratified squamous epithelium. Contains keratinocytes (produce keratin), melanocytes (produce melanin), and dendritic cells (immune function).
Dermis: Middle layer; contains connective tissue, blood vessels, nerves, hair follicles, and glands.
Hypodermis (subcutaneous tissue): Deepest layer; composed mainly of adipose tissue for insulation and energy storage.

Organization of the Epidermis

The epidermis is organized into several layers:

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; dead, keratinized cells.

Skin Appendages and Glands

Skin appendages include hair, nails, and glands. Glands are classified as:

Sebaceous glands: Produce sebum (oil) for lubrication and waterproofing.
Sudoriferous (sweat) glands: Eccrine glands (produce watery sweat for cooling) and apocrine glands (produce thicker secretion in axillary/genital areas).

Gland Type	Secretion	Function
Sebaceous	Sebum	Lubricates skin/hair
Eccrine	Watery sweat	Thermoregulation
Apocrine	Thicker sweat	Odor, emotional sweating

Homeostatic Imbalances of the Skin

Acne: Caused by blocked sebaceous glands and bacterial infection.
Burns: Classified by degree (first, second, third); severity depends on depth and area affected.
Skin cancer: Includes basal cell carcinoma, squamous cell carcinoma, and melanoma. The ABCDE rule (Asymmetry, Border, Color, Diameter, Evolving) helps recognize melanoma.

Chapter 5: The Skeletal System

Classification and Structure of Bones

The skeletal system provides support, protection, and movement. Bones are classified by shape and structure.

Axial skeleton: Skull, vertebral column, thoracic cage.
Appendicular skeleton: Limbs and girdles.
Compact bone: Dense, strong outer layer.
Spongy bone: Porous, contains red marrow.

Long Bone Anatomy

Long bones have a central shaft (diaphysis) and two ends (epiphyses). Key structures include:

Periosteum: Outer covering.
Endosteum: Lines the medullary cavity.
Epiphyseal plate: Site of bone growth in children.
Medullary cavity: Contains yellow marrow (fat storage).

Microscopic Structure of Bone

Osteocytes: Mature bone cells.
Osteoblasts: Build new bone.
Osteoclasts: Break down bone.
Lacunae: Small cavities housing osteocytes.
Lamellae: Layers of bone matrix.
Canaliculi: Tiny channels for nutrient/waste exchange.

Bone Formation and Remodeling

Ossification: Process of bone formation.
Remodeling: Ongoing replacement of old bone with new bone, influenced by stress and hormones.
Critical minerals: Calcium and phosphorus are essential for bone strength.

Types of Bones and Fractures

Bone shapes: Long, short, flat, irregular.
Fracture types: Comminuted, impacted, spiral, greenstick.
Bone repair stages: Hematoma formation, fibrocartilaginous callus, bony callus, bone remodeling.

Axial and Appendicular Skeleton

Major bones to identify:

Axial: Skull (frontal, parietal, temporal, occipital), facial bones, hyoid, vertebrae (cervical, thoracic, lumbar, sacrum, coccyx), sternum, ribs.
Appendicular: Pectoral girdle (clavicle, scapula), upper limb (humerus, radius, ulna, carpals, metacarpals, phalanges), pelvic girdle (ilium, pubis, ischium), lower limb (femur, patella, tibia, fibula, tarsals, metatarsals, phalanges).

Joints and Movement

Joint types: Synarthroses (immovable), amphiarthroses (slightly movable), diarthroses (freely movable).
Structural classifications: Fibrous, cartilaginous, synovial.
Synovial joints: Plane, hinge, condyloid, ball-and-socket.

Joint Type	Movement	Example
Synarthrosis	Immovable	Sutures of skull
Amphiarthrosis	Slightly movable	Intervertebral discs
Diarthrosis	Freely movable	Shoulder, hip

Homeostatic Imbalances of Bones and Joints

Scoliosis: Abnormal lateral curvature of the spine.
Kyphosis: Excessive outward curvature (hunchback).
Lordosis: Excessive inward curvature (swayback).
Dislocation: Bone forced out of joint.
Muscular dystrophy: Progressive muscle weakness and degeneration.

Chapter 6: The Muscular System

Muscle Types and Functions

Muscles are responsible for movement, posture, and heat production. There are three main 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 organs.

Microscopic Anatomy of Muscle Fibers

Muscle fibers contain myofibrils, which are composed of repeating units called sarcomeres. The sarcomere is the functional unit of muscle contraction.

Myofibril: Contains actin (thin) and myosin (thick) filaments.
Sarcomere: Defined by Z lines; contains A band, I band, H zone, M line.
Sliding filament theory: Muscle contraction occurs when actin and myosin filaments slide past each other.

Muscle Contraction Physiology

Neuromuscular junction: Site where a motor neuron stimulates a muscle fiber.
Role of calcium ions: Calcium released from the sarcoplasmic reticulum enables actin-myosin interaction.
Role of acetylcholine (ACh): Neurotransmitter that initiates muscle contraction.

Key equation:

Muscle Movements and Actions

Origin: Attachment to stationary bone.
Insertion: Attachment to movable bone.
Prime mover (agonist): Main muscle responsible for movement.
Antagonist: Opposes the prime mover.
Synergist: Assists the prime mover.

Types of Muscle Movements

Flexion: Decreases angle between bones.
Extension: Increases angle between bones.
Rotation: Movement around an axis.
Abduction: Moves limb away from midline.
Adduction: Moves limb toward midline.
Dorsiflexion/Plantar flexion: Upward/downward movement of foot.

Major Muscles and Their Actions

Head and neck: Frontalis, occipitalis, orbicularis oculi, orbicularis oris, buccinator, masseter, temporalis, platysma, sternocleidomastoid.
Trunk: Pectoralis major, intercostals, rectus abdominis, trapezius, latissimus dorsi, deltoid.
Upper limb: Biceps brachii, triceps brachii, brachialis, brachioradialis.
Lower limb: Gluteus maximus, hamstrings, quadriceps femoris, gastrocnemius.

Homeostatic Imbalances of Muscles

Muscular dystrophy: Genetic disorder causing progressive muscle weakness.

Summary Table: Muscle Types

Muscle Type	Striated?	Voluntary?	Location
Skeletal	Yes	Yes	Attached to bones
Cardiac	Yes	No	Heart
Smooth	No	No	Walls of organs

Additional info: Some explanations and tables have been expanded for clarity and completeness based on standard Anatomy & Physiology curriculum.