Anatomy & Physiology Study Guide: Epithelial Tissue, Integumentary System, Muscular System, and Nervous System

EPITHELIAL TISSUE

General Functions, Organization, and Characteristics

Epithelial tissue covers body surfaces, lines cavities, and forms glands. It is specialized for protection, absorption, secretion, and sensation.

• Cellularity: Composed almost entirely of tightly packed cells with minimal extracellular matrix.

• Polarity: Has an apical (free) surface and a basal surface attached to a basement membrane.

• Basement Membrane: Thin, fibrous layer anchoring epithelium to underlying connective tissue.

• Avascularity: Lacks blood vessels; nutrients diffuse from underlying tissues.

• Regeneration Capability: High rate of cell division for repair and renewal.

• Cell Junctions: Specialized connections (tight junctions, desmosomes, gap junctions) for adhesion and communication.

Example: The skin's outer layer (epidermis) is a stratified squamous epithelium, providing protection against abrasion and pathogens.

Intercellular Attachments

• Desmosome/Anchoring Junction: Provides strong adhesion between cells.

• Tight Junction: Seals adjacent cells to prevent passage of molecules between them.

• Gap Junction: Allows direct communication between cells via small channels.

Classification of Epithelial Tissue

• Number of Layers: Simple (one layer) vs. stratified (multiple layers).

• Cell Shape: Squamous (flat), cuboidal (cube-shaped), columnar (tall).

• Specializations: Cilia, microvilli, keratinization.

Terms: 'Simple' means a single cell layer; 'stratified' means multiple layers.

Types of Epithelial Tissue

Type	Structure	Function	Location
Simple squamous	Single layer, flat cells	Diffusion, filtration	Alveoli, blood vessels
Simple cuboidal	Single layer, cube-shaped	Secretion, absorption	Kidney tubules, glands
Simple columnar	Single layer, tall cells	Absorption, secretion	Digestive tract lining
Pseudostratified ciliated columnar	Appears layered, all cells touch basement membrane	Secretion, movement of mucus	Trachea, upper respiratory tract
Stratified squamous (keratinized)	Multiple layers, surface cells dead and filled with keratin	Protection	Epidermis of skin
Stratified squamous (non-keratinized)	Multiple layers, surface cells alive	Protection	Oral cavity, esophagus
Stratified cuboidal	2+ layers, cube-shaped	Protection, secretion	Some ducts of glands
Stratified columnar	2+ layers, tall cells	Protection, secretion	Male urethra, some glands
Transitional	Multiple layers, shape varies	Stretching	Urinary bladder

Cell Modifications

• Microvilli: Increase surface area for absorption (e.g., small intestine).

• Cilia: Move substances across surface (e.g., respiratory tract).

• Keratinized: Surface cells filled with keratin for waterproofing and protection (e.g., skin).

Exchange and Transporting Epithelium

• Exchange Epithelium: Simple squamous; allows rapid movement of substances (e.g., alveoli).

• Transporting Epithelium: Simple cuboidal/columnar; specialized for absorption/secretion (e.g., kidney tubules, intestines).

• Lumen: The internal space of a tubular structure (e.g., intestine, blood vessel).

Glandular Epithelium

• Glands: Epithelial structures specialized for secretion.

• Exocrine Glands: Secrete products into ducts (e.g., sweat, salivary glands).

• Endocrine Glands: Secrete hormones into blood (e.g., thyroid gland).

• Types of Secretion: Mucous, serous, mixed.

• Methods of Secretion: Merocrine (exocytosis), holocrine (cell rupture), apocrine (apical portion pinched off).

INTEGUMENTARY SYSTEM

Functions and Structure

The integumentary system includes the skin and its derivatives (hair, nails, glands). It protects the body, regulates temperature, and provides sensory information.

• Major Functions: Protection, sensation, thermoregulation, excretion, vitamin D synthesis.

Layers of the Epidermis

• Stratum basale: Deepest layer; mitotically active stem cells.

• Stratum spinosum: Several layers of keratinocytes.

• Stratum granulosum: Cells begin to die, keratinization starts.

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

• Stratum corneum: Outermost, dead keratinized cells.

Desquamation and Cell Replacement

• Desquamation: Shedding of dead keratinized cells from the surface.

• Cell Replacement: New cells produced in stratum basale migrate outward.

Keratinocytes vs. Melanocytes

• Keratinocytes: Produce keratin, most abundant in epidermis.

• Melanocytes: Produce melanin pigment, protect against UV radiation.

Dermis Structure

• Papillary Layer: Superficial, areolar connective tissue, forms dermal papillae.

• Reticular Layer: Deep, dense irregular connective tissue, provides strength and elasticity.

Accessory Structures

• Hair: Protection, sensation.

• Nails: Protection, aid in grasping.

• Glands: Sweat (eccrine, apocrine), sebaceous (oil).

• Sensory Receptors: Touch, pressure, pain, temperature.

MUSCULAR SYSTEM

Types and Functions of Muscle Tissue

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

• Cardiac Muscle: Involuntary, striated, heart wall.

• Smooth Muscle: Involuntary, non-striated, walls of hollow organs.

Muscle Organization

• Gross Anatomy: Muscle → fascicle → muscle fiber (cell) → myofibril → myofilament.

• Connective Tissue Layers: Epimysium (surrounds muscle), perimysium (fascicle), endomysium (fiber).

• Sharpey's Fibers: Collagen fibers anchoring tendon to bone.

Microscopic Structure

• Myofibril: Bundles of myofilaments (actin, myosin) within muscle fiber.

• Sarcomere: Functional contractile unit; Z-line to Z-line.

• Banding: A-band (dark, myosin), I-band (light, actin), H-zone (myosin only).

Muscle Contraction

• Sliding Filament Theory: Actin and myosin filaments slide past each other, shortening the sarcomere.

• Events: Action potential → calcium release → cross-bridge formation → power stroke → detachment → relaxation.

Equation:

$\text{Force} = \text{Cross-sectional area} \times \text{Tension per unit area}$

Muscle Growth and Repair

• Satellite Cells: Aid in muscle repair and growth.

• Hypertrophy: Increase in muscle fiber size.

• Atrophy: Decrease in muscle fiber size.

NERVOUS SYSTEM

Neuron Structure and Function

• Neuron: Functional unit of the nervous system; transmits electrical impulses.

• Parts: Cell body (soma), dendrites (receive signals), axon (sends signals), axon hillock, myelin sheath, axon terminals.

• Myelination: Increases speed of impulse conduction.

Gray Matter vs. White Matter

• Gray Matter: Neuron cell bodies, dendrites, unmyelinated axons.

• White Matter: Myelinated axons.

Types of Neurons

• Sensory (Afferent): Transmit impulses from receptors to CNS.

• Motor (Efferent): Transmit impulses from CNS to effectors.

• Interneurons: Connect sensory and motor neurons within CNS.

Organization of the Nervous System

• CNS: Brain and spinal cord.

• PNS: Cranial and spinal nerves.

• Functional Divisions: Somatic (voluntary), autonomic (involuntary: sympathetic, parasympathetic).

Synapses and Neuroglia

• Synapse: Junction between neurons; includes presynaptic terminal, synaptic cleft, postsynaptic membrane.

• Neuroglia: Support cells; types in CNS (astrocytes, oligodendrocytes, microglia, ependymal cells), in PNS (Schwann cells, satellite cells).

Additional info: This guide is based on a set of structured review questions and learning objectives for a college-level Anatomy & Physiology course, covering key tissues, organ systems, and their cellular and functional organization.