Chapter 4.1 (Human Anatomy) Epithelial Tissue Chapter 4.1 (Human Anatomy)

Histology is the branch of anatomy that studies the structure of animal tissue on a microscopic level.

What is a tissue? A group of cells that all perform the same specific function Example: cardiac, muscle, or nerves

4 Types of Tissues 1) Epithelial Tissue – covers body surfaces and organs, lines body cavities 2) Connective Tissue – binds and supports body parts

3) Muscular Tissue – contracts producing movement 4) Nervous Tissue – responds to stimuli and transmits nerve impulses

Epithelial Tissue Tightly packed cells Readily divides (mitosis) producing new cells to replace old or damaged cells Lacks blood vessels Exists on the skin and on the surface of organs, blood vessels, and body cavities

Function: - Externally – protects body from drying out, injury, and bacterial invasion - Internally – protects, sweeps up impurities, secretes mucus, absorbs

Covers surfaces and lines cavities Has a free surface Other surface attached to underlying tissue by the basement membrane Free Surface Nucleus Basement membrane Cytoplasm Free Surface Nucleus Basement membrane

Simple Epithelial Tissue – composed of a single layer of cells Stratified Epithelial Tissue – composed of 2 or more layers of cell

Types of Epithelial Tissues 1] Squamous Epithelium: simple and stratified 2] Cuboidal Epithelium 3] Columnar Epithelium 4] Pseudostratified Epithelium 5] Transitional Epithelium

Squamous Epithelium 2 types of squamous epithelium: * Simple Squamous Epithelium * Stratified Squamous Epithelium

SIMPLE SQUAMOUS EPITHELIUM: – Single layer of flattened cells – Function: secretion, absorption, and filtration – Location: lines the lungs, blood vessels and heart

Simple Squamous Epithelium Cytoplasm Nucleus Simple Squamous Epithelium

STRATIFIED SQUAMOUS EPITHELIUM – Many layers of flattened cells – Function: protection – Location: outer layer of skin, lining the various orifices of the body

Stratified Squamous Epitlelium

Cuboidal Epithelium Location Function Glands secretion Kidney tubules Simple Cuboidal Epithelium: - single layer of cube-shaped cells attached to a basement membrane Stratified Cubiodal Epithelum: two or more layers of cube-shaped cells Location Function Glands secretion Kidney tubules Secretion & absorption

Simple Cuboidal Epithelium Basement membrane Nucleus Free Surface Simple Cuboidal Epithelium

Simple Columnar Epithelium Composed of cells that are longer than wider Nucleus found in the lower half of the cell Location Function Digestive organ Absorption Uterine tubes Propel egg to uterus

Free Surface Nucleus Basement membrane

Pseudostratified Epithelium Cells appear to be layered due to irregularly placed nuclei but each cell touches the basement membrane May contain cilia – aids in movement of particles Function: protection, secretion, movement of mucus and sex cells Location: respiratory tract, reproductive tract

Pseudostratified Epithelium Cilia Nucleus Basement membrane Pseudostratified Epithelium

Transitional Epithelium Tissue that changes in response to tension Found in organs that need to stretch Location: urinary bladder, ureters, urethra

Transitional Epithelium Basement membrane Nucleus Free Surface Transitional Epithelium