Epithelial Tissues and function

Epithelial Tissue

Covers body surfaces, lines cavities and organs, and forms glands. Functions include protection, secretion, absorption, filtration, and sensation. Cells are tightly packed with little extracellular matrix, sit on a basement membrane, and are avascular (no blood supply).

Connective Tissue

Supports, binds, and protects other tissues; stores energy (fat); provides structural framework (bone, cartilage); and transports substances (blood). Characterized by cells scattered within an extracellular matrix that varies from fluid to solid.

Nervous Tissue

Detects stimuli and transmits electrical/chemical signals for rapid communication and coordination throughout the body. Composed of neurons (signal-conducting cells) and neuroglia (supporting cells).

Muscle Tissue

 Generates force and produces movement through contraction. Found in three forms that move the skeleton, organs, and heart.

 Simple Squamous Epithelium

A single layer of thin, flattened cells. Suited for rapid diffusion and filtration. Found lining blood vessels (endothelium), alveoli of the lungs, and body cavities (mesothelium).

Simple Cuboidal Epithelium

A single layer of cube-shaped cells with round, central nuclei. Functions in secretion and absorption. Found in kidney tubules and gland ducts.

 Simple Columnar Epithelium

 A single layer of tall, column-shaped cells with elongated nuclei near the base. Specialized for absorption and secretion; often includes goblet cells (mucus-secreting) and microvilli. Found lining the digestive tract.

Stratified Squamous Epithelium

Multiple layers of cells, with flattened squamous cells at the surface. Provides protection against abrasion. Basal cells are cuboidal/columnar and divide to replace surface cells that are shed.

Keratinized Stratified Squamous

Surface cells are dead, forming a tough, waterproof barrier. Found in the epidermis of the skin.

Non-Keratinized Stratified Squamous

Surface cells remain alive and moist (no keratin buildup). Found lining the mouth, esophagus, and vagina.

Transitional Epithelium (Urothelium)

Stratified epithelium with dome-shaped surface cells that flatten and stretch when the organ fills, allowing the tissue to expand without tearing. Found lining the bladder, ureters, and part of the urethra.

Pseudostratified Columnar Epithelium

A single layer of cells that appear layered because nuclei sit at varying heights, though all cells touch the basement membrane. Found lining the trachea and much of the respiratory tract.

Cilia

Hair-like projections on the apical surface that beat in a coordinated motion to move mucus and trapped particles (e.g., along the respiratory tract).