Lining Epithelium

What are the two main types of epithelial tissue?

1. Lining epithelia 2. Glandular epithelia

What are lining epithelia?

Epithelial tissues that cover or line internal organs, body cavities, and surfaces exposed to the external environment.

Where are lining epithelia commonly found?

• Respiratory tract - Digestive tract - Airways - Skin

What is the main function of lining epithelia?

They form a protective barrier for internal organs and body surfaces.

What is glandular epithelium?

Epithelial tissue specialised to produce and secrete substances.

How do glands form from glandular epithelium?

The epithelial cells grow down into the connective tissue to form a gland.

What two criteria are used to classify lining epithelial tissues?

1. Number of cell layers 2. Shape of the cells at the free surface

What determines whether an epithelium is simple or stratified?

The number of cell layers.

What is simple epithelium?

Epithelium consisting of a single layer of cells.

What is stratified epithelium?

Epithelium consisting of two or more layers of cells.

How many layers can stratified epithelium contain?

Two layers to more than 100 layers of cells.

Which cells determine the classification of stratified epithelia?

The shape of the cells on the top (free/apical) surface.

What are squamous epithelial cells?

Flat cells that are wider than they are tall.

What are cuboidal epithelial cells?

Cube-shaped cells that are as tall as they are wide.

What are columnar epithelial cells?

Tall, narrow cells that are taller than they are wide.

What is simple squamous epithelium?

A single layer of flattened cells.

What is the main function of simple squamous epithelium?

Rapid transport and diffusion of substances across the membrane.

Where is simple squamous epithelium found?

• Blood vessels - Alveoli of the lungs

Why is simple squamous epithelium suited for gas exchange?

Because it is extremely thin, allowing rapid diffusion of gases like oxygen.

What is simple cuboidal epithelium?

A single layer of cube-shaped cells.

What is the main function of simple cuboidal epithelium?

Secretion and formation of glands.

Where is simple cuboidal epithelium commonly found?

Kidney tubules and ducts.

What is simple columnar epithelium?

A single layer of tall column-shaped cells.

Why are simple columnar cells well suited for absorption?

They contain many organelles that support absorption processes.

Where is simple columnar epithelium found?

Gastrointestinal tract, especially the small intestine.

What is pseudostratified columnar epithelium?

A single layer of cells that appears stratified but all cells contact the basement membrane.

Why does pseudostratified epithelium appear stratified?

Because cell nuclei lie at different levels, creating the illusion of multiple layers.

What is stratified squamous epithelium?

Multiple layers of flattened cells that provide protection.

Where is stratified squamous epithelium found?

• Skin - Mouth - Esophagus

What is stratified cuboidal epithelium?

Epithelium with multiple layers of cube-shaped cells.

Where is stratified cuboidal epithelium found?

• Sweat glands - Salivary glands - Mammary glands

What is stratified columnar epithelium?

Epithelium consisting of multiple layers with column-shaped surface cells.

Where is stratified columnar epithelium found?

Parts of the male reproductive system, including the male urethra.

What are the four specialised epithelial tissues?

1. Endothelium 2. Mesothelium 3. Respiratory epithelium 4. Transitional epithelium

What is endothelium?

A specialised simple squamous epithelium lining blood vessels.

What is the function of endothelium?

Allows rapid diffusion and exchange of molecules across blood vessel walls.

Where is endothelium found?

• Cardiovascular system - Lymphatic system

What is mesothelium?

A simple squamous epithelium with lubricating properties.

What is the function of mesothelium?

Reduces friction between moving organs.

Where is mesothelium found?

Around organs such as the lungs.

What is keratinised stratified squamous epithelium?

Epithelium containing dead cells filled with keratin in the outer layers.

Where is keratinised stratified squamous epithelium found?

Skin.

What is the function of keratin in epithelial tissue?

Creates a waterproof protective barrier.

What is non-keratinised stratified squamous epithelium?

Stratified epithelium whose surface cells are alive and contain nuclei.

Where is non-keratinised stratified squamous epithelium found?

• Mouth - Esophagus - Nostrils - Vagina

What is the full name of respiratory epithelium?

Pseudostratified ciliated columnar epithelium with goblet cells.

What are goblet cells?

Cells that produce and secrete mucus.

What is the mucociliary escalator?

A transport system that removes trapped particles from the respiratory tract.

How does the mucociliary escalator work?

1. Goblet cells produce mucus that traps particles 2. Cilia beat to move mucus upward toward the throat.

What is transitional epithelium?

Epithelium that can change shape depending on stretching.

Where is transitional epithelium found?

• Bladder - Ureters

Why is transitional epithelium important in the bladder?

It allows the bladder to expand when filling and contract when emptying.