Anatomy & Physiology: Cell Membrane Transport and Integumentary System Study Notes

Cell Membrane Transport

Introduction to Cell Membrane Transport

Cell membrane transport refers to the movement of substances across the plasma membrane, which is essential for maintaining cellular homeostasis and function. The plasma membrane is selectively permeable, allowing certain molecules to pass while restricting others.

• Cell Membrane: A biological barrier composed primarily of a phospholipid bilayer with embedded proteins.

• Transport Mechanisms: Include passive and active processes.

Types of Cell Membrane Transport

• Passive Transport: Movement of substances without energy input.

  • Diffusion: Movement of molecules from high to low concentration.

  • Osmosis: Diffusion of water across a selectively permeable membrane.

  • Facilitated Diffusion: Movement of molecules via membrane proteins.

• Active Transport: Movement of substances against their concentration gradient, requiring energy (ATP).

  • Pumps: e.g., Sodium-potassium pump ($Na^+/K^+$ ATPase).

  • Endocytosis: Uptake of materials via vesicle formation.

  • Exocytosis: Release of substances from the cell via vesicles.

Key Terms and Concepts

• Concentration Gradient: Difference in concentration of a substance across a space.

• Transport Proteins: Proteins that assist in moving substances across the membrane.

• Polarity: Hydrophilic (water-loving) and hydrophobic (water-fearing) regions of the membrane.

Examples and Applications

• Osmosis: Water movement in red blood cells.

• Active Transport: Uptake of glucose in intestinal cells.

Plasma Membrane Structure and Function

Components of the Plasma Membrane

The plasma membrane is primarily composed of phospholipids, proteins, cholesterol, and carbohydrates.

• Phospholipid Bilayer: Provides fluidity and barrier function.

• Proteins: Serve as channels, carriers, receptors, and enzymes.

• Cholesterol: Stabilizes membrane fluidity.

• Carbohydrates: Involved in cell recognition and signaling.

Functional Characteristics of Phospholipids

• Hydrophilic Head: Attracted to water.

• Hydrophobic Tails: Repel water.

Cell Junctions

Cell junctions are specialized structures that connect adjacent cells.

• Tight Junctions: Prevent leakage between cells.

• Desmosomes: Provide mechanical strength.

• Gap Junctions: Allow communication via ions and small molecules.

Endocytosis vs. Exocytosis

• Endocytosis: Process by which cells take in substances by engulfing them in vesicles.

• Exocytosis: Process by which cells expel substances using vesicles.

Osmosis and Tonicity

Osmosis

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

• Tonicity: Refers to the ability of a solution to change the shape of cells by altering their internal water volume.

• Isotonic Solution: No net water movement; cell shape remains unchanged.

• Hypertonic Solution: Water moves out; cell shrinks (crenation).

• Hypotonic Solution: Water moves in; cell swells and may burst (lysis).

Integumentary System

Introduction to the Integumentary System

The integumentary system consists of the skin and its accessory structures, serving as the body's first line of defense and playing roles in protection, sensation, and regulation.

• Skin: Largest organ of the body.

• Accessory Structures: Hair, nails, sweat glands, sebaceous glands.

Skin Structure

The skin is composed of three main layers: epidermis, dermis, and hypodermis.

• Epidermis: Outermost layer; consists of stratified squamous epithelium.

• Dermis: Middle layer; contains connective tissue, blood vessels, nerves, and glands.

• Hypodermis (Subcutaneous Layer): Deepest layer; composed of adipose tissue.

Functions of the Skin

• Protection: Against pathogens, chemicals, and physical injury.

• Regulation: Body temperature and water loss.

• Sensation: Touch, pain, temperature.

• Excretion: Removal of waste via sweat.

• Synthesis: Vitamin D production.

Skin Cross Section Structures

• Epidermis

• Dermis

• Hair Follicle

• Sweat Gland

• Sudoriferous Gland

• Arrector Pili Muscle

Epidermis and Dermis

• Epidermis: Contains several layers (strata), including the stratum corneum and stratum basale.

• Dermis: Contains papillary and reticular layers; provides strength and elasticity.

Keratinization

Keratinization is the process by which keratinocytes produce keratin, a protective protein, as they move from the basal layer to the surface.

Sweat and Sebaceous Glands

• Sudoriferous (Sweat) Glands: Produce sweat for thermoregulation.

• Types: Eccrine (all over body) and apocrine (axillary and genital areas).

• Sebaceous Glands: Secrete sebum to lubricate skin and hair.

Hair and Nails

• Hair: Composed of keratin; functions in protection and sensation.

• Nails: Protect distal phalanges; composed of hard keratin.

Skin Pigments

• Melanin: Brown-black pigment produced by melanocytes.

• Carotene: Yellow-orange pigment.

• Hemoglobin: Red pigment from blood.

Types of Skin Cancer

• Basal Cell Carcinoma: Most common, least dangerous.

• Squamous Cell Carcinoma: May metastasize.

• Melanoma: Most dangerous; arises from melanocytes.

HTML Table: Comparison of Cell Junctions

Type	Structure	Function	Location
Tight Junction	Interlocking proteins	Prevents leakage	Intestinal lining
Desmosome	Protein plaques, intermediate filaments	Mechanical strength	Skin, heart
Gap Junction	Connexons (protein channels)	Cell communication	Cardiac muscle

Key Equations

• Osmotic Pressure: $\Pi = iMRT$

• Rate of Diffusion (Fick's Law): $J = -D \frac{dC}{dx}$

Additional info: Academic context and definitions have been expanded for clarity and completeness.