Study Guide: Tissues, Cellular Structure, and Membrane Transport in Anatomy & Physiology

Body's Extracellular Environment

Composition of the Extracellular Environment

The extracellular environment consists of all body fluids and substances outside the cells. It plays a crucial role in supporting cell function and communication.

• Extracellular fluid (ECF): Includes interstitial fluid, plasma, and transcellular fluids.

• Extracellular matrix (ECM): A network of proteins (e.g., collagen, elastin) and polysaccharides that provide structural and biochemical support to surrounding cells.

• Functions: Provides nutrients, removes waste, and facilitates cell signaling.

Cellular Mechanisms for Adherence and Communication

• Cell adhesion molecules (CAMs): Proteins on the cell surface that help cells stick to each other and to the ECM.

• Junctions: Tight junctions, desmosomes, and gap junctions enable physical connection and communication between cells.

• Signaling: Cells use contact signaling, chemical signaling (e.g., hormones, neurotransmitters), and electrical signaling to communicate.

Tissues: Types, Structure, and Function

Definition and Classification of Tissues

Tissue is a group of similar cells that perform a common function. Histology is the study of tissues. The four main tissue types are:

• Epithelial tissue

• Connective tissue

• Muscle tissue

• Nervous tissue

Epithelial Tissue

• Structure: Sheets of tightly packed cells covering body surfaces and lining cavities.

• Functions: Protection, absorption, filtration, excretion, secretion, and sensory reception.

• Specializations: Microvilli (increase surface area), cilia (movement of substances).

• Properties: Polarity, avascularity, high regenerative capacity.

Types of Epithelial Tissue (by cell layers and shape)

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
Simple columnar	Single layer, tall cells	Absorption, secretion	Digestive tract
Pseudostratified columnar	Single layer, appears stratified	Secretion, movement	Respiratory tract
Stratified squamous	Multiple layers, flat cells	Protection	Skin, mouth
Stratified cuboidal	2+ layers, cube-shaped	Protection	Glands
Stratified columnar	2+ layers, tall cells	Protection, secretion	Male urethra
Transitional	Multiple layers, variable shape	Stretching	Urinary bladder

Lab linked objective: Differentiate between epithelial tissues by structure and function.

Glands: Exocrine vs. Endocrine

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

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

• Structural difference: Exocrine glands have ducts; endocrine glands are ductless.

Multicellular Exocrine Glands

• Structural classification: Simple (unbranched duct) vs. compound (branched duct).

• Functional classification: Merocrine (exocytosis), apocrine (part of cell pinched off), holocrine (cell ruptures).

Connective Tissue

• Structure: Cells scattered within an abundant extracellular matrix.

• Functions: Support, protection, insulation, storage, transport.

• Specializations: Vary by type (e.g., bone is mineralized, blood is fluid).

Types of Connective Tissue

Type	Structure	Function	Location
Loose connective (areolar, adipose, reticular)	Loose fibers, many cells	Cushioning, support	Under epithelia, lymphoid organs
Dense connective (regular, irregular, elastic)	Dense fibers, few cells	Strength, flexibility	Tendons, ligaments, dermis
Cartilage (hyaline, elastic, fibrocartilage)	Firm matrix, chondrocytes	Support, flexibility	Joints, ear, intervertebral discs
Bone	Hard, calcified matrix	Support, protection	Skeletal system
Blood	Fluid matrix (plasma)	Transport	Blood vessels

Lab linked objective: Identify dense regular, dense irregular, elastic, and cartilage tissues.

Membranes: Serous vs. Mucous

• Serous membranes: Line body cavities not open to the exterior; secrete serous fluid (e.g., pleura, pericardium).

• Mucous membranes: Line cavities open to the exterior; secrete mucus (e.g., respiratory, digestive tracts).

• Differences: Structure (epithelial type), location, and secretion type.

Tissue Repair

• Phases: Inflammation, organization (granulation tissue formation), regeneration, and fibrosis (scar formation).

• Growth factors: Proteins that stimulate cell division and tissue repair.

• Variables affecting repair: Nutrition, blood supply, age, type of tissue damaged.

Cellular Structure and Membrane Transport

Plasma Membrane Structure

• Phospholipid bilayer: Hydrophilic heads face outward, hydrophobic tails inward.

• Proteins: Integral (span membrane) and peripheral (surface-bound) proteins serve as channels, receptors, enzymes.

• Carbohydrates: Attached to proteins/lipids, function in cell recognition.

Membrane Transport Mechanisms

Type	Process	Energy Required?	Examples
Passive	Simple diffusion, osmosis, facilitated diffusion, filtration	No	O2/CO2 exchange, water movement
Active	Active transport, bulk transport (exocytosis, endocytosis, receptor-mediated endocytosis)	Yes (ATP)	Na+/K+ pump, phagocytosis

Cellular Structures: Structure and Function

• Nucleus: Contains genetic material (DNA), controls cell activities.

• Nucleolus: Site of ribosome synthesis.

• Ribosome: Protein synthesis.

• Golgi apparatus: Modifies, sorts, and packages proteins/lipids.

• Smooth endoplasmic reticulum (ER): Lipid synthesis, detoxification.

• Rough ER: Protein synthesis (with ribosomes attached).

• Lysosome: Digestion of cellular waste.

• Peroxisome: Breakdown of fatty acids, detoxification.

• Mitochondria: ATP production (cellular respiration).

• Microtubules, microfilaments, intermediate filaments: Cytoskeleton, cell shape, movement.

• Cilia and flagella: Movement of cell or substances across cell surface.

Cell Cycle Events

• Interphase: Cell grows, DNA replicates.

• Prophase: Chromosomes condense, spindle forms.

• Metaphase: Chromosomes align at cell equator.

• Anaphase: Sister chromatids separate.

• Telophase: Nuclear envelope reforms, chromosomes decondense.

• Mitosis: Division of nucleus.

• Cytokinesis: Division of cytoplasm, two daughter cells form.

Example: During tissue repair, cells undergo mitosis to replace damaged cells, and the process is regulated by growth factors and the cell cycle.

Additional info: The above content is expanded and organized based on the provided study guide objectives, with academic context added for clarity and completeness.