Tissue Types

Key Terms

• Differentiation = produces specialized cells during embryonic development

• Tissues = groups of cells which are similar in structure and which perform common or related functions

• Histology = the study of tissues

Four Basic Kinds of Tissues

• Epithelial Tissue

• Connective Tissue

• Muscle Tissue

• Nervous Tissue

Epithelial Tissue• Locations:

– Covers the body– Lines organs, body cavities, and ducts– Forms glands

• Functions:– Protection from injury and microbial invasion– Regulates permeability– Secretes fluids to lubricate structures

Characteristics:

• Avascular (no blood vessels)

• Cells may show polarity (apical & basal surface, they are chemically and structurally different from one another)

• A basement membrane attaches epithelia to underlying connective tissues

• High rate of cell division (allows repair by sloughing off dead or injured cells, important because epithelium is exposed to physical stress)

Epithelial Tissue

The Polarity of Epithelial Cells

• Number of cell layers pg 113– Simple (single layer)– Stratified (several layers)– Pseudostratified (nuclei are at different levels & not

all cells reach the apical surface)

• Shape of cells (draw, location, function)– Squamous (thin, flat, irregular cells) pg 115– Cuboidal (cube shaped cells) pg 116– Columnar, ciliated and nonciliated (tall & slender

cells) pg 116, 117– Transitional (change shape from flat to cuboidal and

back) pg 119

Classification of Epithelia

Squamous Epithelia

Cuboidal Epithelia

Cuboidal Epithelia Cont.

Special Cuboidal Epithelia:Transitional Epithelia

cells can stretch

Columnar Epithelia

Columnar Epithelia

Columnar Epithelia

Many epithelia contain gland cells that produce secretions

Exocrine glands:– Produce secretions such as mucus and/or watery

solution through ducts onto the epithelial surface

Endocrine glands:– Ductless, release secretions directly into bloodstream

Glandular epithelia

Exocrine vs. Endocrine

Glands

Examples of Exocrine Glands

Time to Review

Simple squamous epithelium (lining of body cavities)

Simple cuboidal epithelium (lining of glands and ducts)

Simple columnar epithelium (lining of stomach, intestines)

Stratified squamous epithelium (skin)

Simple columnar epithelium (lining of digestive tract)

Simple cuboidal epithelium (lining of ducts in kidneys)

Simple squamous epithelium (lining of the heart)

Pseudostratified columnar epithelium (lining of nasal cavity)

Transitional epithelium (urinary bladder)

Stratified squamous epithelium (lining of mouth)

Type of Tissue Function Location

Pseudostratified columnar

removing dust and particles from airways, has cilia

lines the respiratory passageways

Simple Columnar Absorptionlines the uterus and most organs of the digestive tract

Simple Cuboidal Secretion and Absorptionglands, kidney tubules, ovaries

Simple Squamous Diffusion and Filtrationlungs, walls of capillaries and vessels

Stratified Squamous Protects underlying cellsskin(keratinized) and the throat, vagina, mouth (soft)

Stratified Cuboidal Protectionlines ducts of the mammary glands, sweat glands, pancreas

Stratified Columnar Protection, secretionmale urethra and vas deferens, parts of the pharynx

Transitional (unstretched)

Specialized to become distended

urinary tract