Human Tissue Types, Epithelial Classification, and Gland Functions

Epithelial Tissue

Covers body surfaces, lines cavities, and forms glands.

Connective Tissue

Provides support, protection, and binds other tissues together.

Muscle Tissue

Responsible for movement.

Nervous Tissue

Controls and coordinates body functions.

Squamous

Thin, flat, and scaly cells specialized for rapid diffusion and filtration.

Cuboidal

Square or cube-shaped cells often involved in secretion and absorption.

Columnar

Taller than they are wide cells resembling columns, involved in absorption and secretion.

Simple Epithelium

A single layer of cells where all cells touch the basement membrane, found in areas of absorption, secretion, and filtration.

Stratified Epithelium

Two or more layers of cells, with only the bottom layer resting on the basement membrane, ideal for protection.

Pseudostratified Epithelium

Appears to have multiple layers due to nuclei at different levels, but is a single layer, often with cilia, found in the respiratory tract.

Stratified Columnar Epithelium

The rarest stratified epithelium, found in limited locations such as parts of the male urethra and some large gland ducts.

Glands

Organs or cells that secrete substances, classified based on where their secretions are released.

Exocrine Glands

Glands that secrete their products into a duct leading to an epithelial surface (e.g., sweat glands, salivary glands).

Endocrine Glands

Ductless glands that secrete hormones directly into the bloodstream or interstitial fluid.

Stroma

The supportive connective tissue framework of a gland.

Parenchyma

The functional glandular tissue, typically made of epithelial tissue, performing the gland's main function.

Cellular Junctions

Protein structures that bind cells together and allow for communication between them.

Tight Junctions

Form a watertight seal between cells, crucial in the digestive tract to prevent leakage.

Desmosomes

Act like 'rivets' or spot welds, holding cells together and preventing them from being pulled apart.

Gap Junctions

Channels that allow for the direct passage of small molecules, ions, and electrical signals between adjacent cells.