Chapter 3: Epithelial Tissue

What are the tissue types of the body

• Epithelial tissue

• Connective tissue

• Nervous tissue

• Muscle tissue

Epithelial tissues

Covers the internal and external surfaces of the body

Properties of Epithelial tissues

1. Had an apical surface exposed to the outside of the body to the lumen of the internal cavity

2. Held together by special contacts which includes tight junctions and desmosomes

3. A basement membrane connects the basal surface of the epithelium to an underlying layer of connective tissue

4. They are avascular

Apical Surface

Surface of the epithelial cell which faces the lumen or the external environment

Lumen

The space inside the body’s spaces and cavities

Tight junctions

Protein complexes in epithelial cells that seal and prevent solutes and water from leaking from the cell

Desmosomes

Weld epithelial cells together. Kind of like a glue between cells

Basement membrane

Thin, dense layer of membrane that lines human tissues and serves as a supporting structure and scaffolding for epithelial tissue. It is between cells and underlying connective tissue

Basal Surface

The bottom part of the epithelial cell that faces underlying connective tissue. It is connected to the basement membrane

Avascular

Having no or few blood vessels

If the epithelium is avascular, how do they get their nutrients?

Diffusion through the connective tissue

Simple epithelium

• An epithelium made of one layer of cells

• Found where substances are exchanged across a surface

Stratified epithelium

• Made up of two or more layers of cells.

• Provide strength and protection

Where are non-keratinized stratified epithelium found?

They would be in areas with a lot friction and not exposed to air such as

• Vaginal canal

• Anus

• Inside of mouth

Where are keratinized stratified epithelium found?

They are found on the epidermis of the skin

How does the function of stratified epithelium relate to their function

Simple Squamous

Cell shaped like pancakes

Where do you find simple squamous epithelium?

• lungs

• alveoli

• Lining of lumen in blood vessels and lymph vessels

• Serous membrane of body cavities

How does the structure of simple squamous epithelium relate to their function?

Their thin membrane allows for diffusion and filtration

Allows for secretion in serous membranes

Simple Cuboidal

Epithelial cells shaped like cubes

Where do you find simple cuboidal?

Kidney tubules

Follicles of the thyroid gland

Ovaries

Secretory regions

Ducts of most glands

How does the structure of simple cuboidals relate to their function?

They are good for secretion and absorption

Simple Columnar

Elongated epithelial cells

Where are simple columnar found

Inner lining of most of the digestive tract

How does the structure of simple columnar epithelium relate to their function

Their morphology aides in absorption and secretion. They sometimes have microvilli and/or contain goblet cells that secrete mucin

Stratified Squamous Epithelium

Multiple layers of squamous cells

Stratified columnar epithelium

Multiple layers of columnar epithelium

How does the structure of stratified columnar epithelium relate to their function

They aid in protection and secretion

Where are stratified columnar epithelium found?

• Large ducts of salivary glands

• Conjunctiva covering the eye

• Membranous part of the male urethra