Anatomy & Physiology: Cell Structure, Tissues, and Integumentary System Study Guide

Chapter 3: Cell Structure and Function

Plasma Membrane Structure and Function

The plasma membrane is a selectively permeable barrier that surrounds the cell, controlling the movement of substances in and out. It is primarily composed of a phospholipid bilayer with embedded proteins.

• Phospholipid bilayer: Consists of two layers of phospholipids with hydrophilic (water-attracting) heads facing outward and hydrophobic (water-repelling) tails facing inward.

• Can pass: Small, nonpolar molecules (e.g., O2, CO2), and some small uncharged polar molecules.

• Cannot pass: Large molecules, ions, and polar molecules without assistance.

• Importance: Maintains homeostasis by regulating the internal environment of the cell.

Membrane Transport: Channel-Mediated Diffusion vs. Facilitated Diffusion

Cells use different mechanisms to transport substances across the plasma membrane.

• Channel-mediated diffusion: Movement of ions or small molecules through protein channels; typically specific for certain ions (e.g., Na+, K+).

• Facilitated diffusion: Movement of larger or polar molecules via carrier proteins; does not require energy.

• Substances: Channel-mediated: ions, water; Facilitated: glucose, amino acids.

Osmosis and Tonicity

Osmosis is the diffusion of water across a selectively permeable membrane from an area of low solute concentration to high solute concentration.

• Isotonic solution: Equal solute concentration inside and outside the cell; no net water movement.

• Hypotonic solution: Lower solute concentration outside the cell; water enters the cell, causing it to swell.

• Hypertonic solution: Higher solute concentration outside the cell; water leaves the cell, causing it to shrink.

Chromosome Behavior During Mitosis

During mitosis, chromosomes undergo a series of changes to ensure equal distribution to daughter cells.

• Prophase: Chromosomes condense and become visible.

• Metaphase: Chromosomes align at the cell's equator.

• Anaphase: Sister chromatids separate and move to opposite poles.

• Telophase: Chromosomes decondense, and nuclear envelopes reform.

Transcription vs. Translation

These are two key processes in gene expression.

• Transcription: DNA is used as a template to synthesize messenger RNA (mRNA) in the nucleus.

• Translation: mRNA is decoded by ribosomes in the cytoplasm to assemble amino acids into a protein.

• End result: Transcription produces mRNA; translation produces a polypeptide (protein).

Chapter 4: Tissues

Exocrine vs. Endocrine Glands

Glands are specialized epithelial structures that secrete substances.

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

• Endocrine glands: Release hormones directly into the bloodstream (e.g., thyroid, pituitary glands).

• Examples: Exocrine: sweat glands; Endocrine: adrenal glands.

Connective Tissue Types and Functions

Connective tissues provide support, protection, and binding for other tissues.

• Areolar tissue: Loose connective tissue; contains fibroblasts, collagen, and elastic fibers; found under epithelia.

• Dense tissue: Contains densely packed collagen fibers; found in tendons and ligaments.

• Cells: Fibroblasts (produce fibers), adipocytes (store fat), immune cells.

• Ground substance: Gel-like material that fills spaces between cells and fibers.

Epithelial Membranes

Epithelial membranes are sheets of epithelial tissue combined with underlying connective tissue.

• Mucous membranes: Line body cavities open to the exterior (e.g., digestive tract).

• Serous membranes: Line closed body cavities (e.g., peritoneum, pleura).

• Cutaneous membrane: The skin; covers the body surface.

Regenerative Capacity of Tissues

Tissues vary in their ability to regenerate after injury.

• Epithelial tissue: High regenerative capacity due to rapid cell division.

• Skeletal muscle: Limited regeneration; satellite cells assist repair.

• Cardiac muscle: Very limited regeneration; most damage results in scar tissue.

Chapter 5: Integumentary System

Functions of the Integumentary System

The Integumentary System includes the skin, hair, nails, and glands, serving multiple vital functions.

• Protection: Acts as a barrier against pathogens, chemicals, and physical injury.

• Regulation: Helps control body temperature via sweat and blood flow.

• Sensation: Contains sensory receptors for touch, pain, and temperature.

• Excretion: Removes waste products through sweat.

• Synthesis: Produces vitamin D when exposed to sunlight.

Epidermis Structure

The epidermis is the outermost layer of the skin, composed of keratinized stratified squamous epithelium.

• Keratinized: Contains the protein keratin, making it tough and water-resistant.

• Stratified squamous: Multiple layers of flat cells provide protection.

Layers of the Epidermis

The epidermis consists of several layers, each with distinct functions.

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

• Stratum spinosum: Provides strength and flexibility.

• Stratum granulosum: Cells begin to die and accumulate keratin.

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

• Stratum corneum: Outermost layer; dead, keratinized cells.

Dermis Structure and Components

The dermis is the thick layer beneath the epidermis, providing strength and elasticity.

• Connective tissues: Dense irregular connective tissue, areolar tissue.

• Structures: Blood vessels, nerves, hair follicles, sweat glands, sebaceous glands.

• Other components: Collagen and elastic fibers, immune cells.

Tissue Type	Location	Regenerative Capacity
Epithelial	Skin, lining of organs	High
Skeletal Muscle	Muscles attached to bones	Moderate
Cardiac Muscle	Heart	Low

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