Epithelial Tissue

Histology

Study of tissues.

Tissue

Collection of cells that performs a specific function.

Epithelial

Tissue that covers exposed surfaces, lines internal passageways, and produces glandular secretions.

Exocrine glands

Glands that secrete onto external surfaces or into internal passageways (ducts) that connect to the exterior.

Endocrine glands

Glands that secrete hormones or precursors into the bloodstream to travel to their target sites.

epithelial tissue

It’s functions include protection, filtration, absorption, secretion, and sensation.

Apical

Surface of epithelial cells that faces the outside environment.

Simple

Epithelial tissue type consisting of a single layer of cells.

Stratified

Epithelial tissue type consisting of multiple layers of cells.

Squamous shape

Flat cell shape, most common in the body.

Cuboidal shape

Cell shape that is as high as it is wide, least common in the body.

Columnar shape

Cell shape that is taller than it is wide, second most common in the body.

Gap junctions

Cell structures that permit chemical communication between adjacent cells.

Desmosomes

Strong attachments between cells formed by cell adhesion molecules (CAMs) and intercellular cement.

Hemidesmosomes

Structures that connect epithelial cells to the basal layer.

Basal lamina

The deepest layer of epithelial cells

Simple squamous epithelium

Thin and flat epithelium found in areas of absorption or diffusion.

Stratified squamous epithelium

Multi-layered epithelium providing protection in areas with mechanical or chemical stress.

Keratinized

Type of stratified squamous epithelium that contains the tough, water-resistant epithelium found on the skin's surface.

Nonkeratinized

Type of stratified squamous epithelium: Moist epithelium that resists absorption, found in areas like the mouth and esophagus.

Simple cuboidal epithelium

One layer epithelium found in the lining of exocrine glands and kidney tubules.

Stratified cuboidal epithelium

Multi-layered epithelium found in ducts of some exocrine glands.

Transitional epithelium

Unique epithelium that stretches and recoils, found in the later parts of the urinary system.

Simple columnar epithelium

Single layer epithelium located in the stomach and intestines.

Pseudostratified columnar epithelium

Epithelium that appears stratified but is a single layer with varying cell heights, often ciliated.

Stratified columnar epithelium

Rare epithelium with multiple layers, found in large ducts of salivary glands.

Glands

Collections of epithelial cells that produce secretions.

Merocrine secretion

Secretion released from secretory vesicles via exocytosis, is used to form mucus.

Apocrine secretion

Secretion that includes loss of apical surface and cytoplasm with secretion.

Holocrine secretion

Secretion in which the cell bursts to release secretion, killing the cell.

shape and number of layers

How epithelial cells are classified

Stratified

Epithelial tissues that has a basal surface that leads up to the apical surface

Apical

Layer of epithelial tissue that determines shape classification

Gap Junction

Cell structure that is formed by interlocking junctional proteins (connexons), and allows nervous signals to pass through

Hemidesmosomes

Cell structure made of peripheral and transmembrane proteins, connects to basal layer

Clear Layer

Layer of the basal lamina that contains glycoproteins and fine protein filaments

Dense layer

Layer of the basal lamina that contains bundles of course protein fibers and gives strength to restrict diffusion

Clear and Dense

The two layers of the basal lamina

Adhesion Belt

Cell structure that locks cells together at one level, typically at the same point where blood vessels flow

Occluding Junctions

Cell structure that forms a barrier that isolates basolateral surfaces and deeper tissues from contents of the outside world

Simple Squamous Epithelium

Epithelial tissue that is found along kidney passages, inside the eye, and in the alveoli of the lung

Mesothelium

Type of simple squamous epithelium that lines the ventral body cavity

endothelium

Type of simple squamous epithelium that lines the heart and blood vessels

Stratified Squamous Epithelium

Epithelial tissue that forms a thick protective layer in the skin, mouth, throat, esophagus, rectum, anus, and vagina

Squamous Layer

Part of the stratified squamous epithelium where function occurs

They slough off

What happens to cells after they become squamous in the stratified squamous epithelium

Cuboidal Epithelium

Epithelial tissues that includes cells that look like hexagonal boxes with a nucleus in the center

columnar epithelium

Epithelial tissue that contains elongated nuclei near the basal lamina

Nuclei are located at different areas of the cell

The reason that pseudostratified columnar epithelium appears stratified

All cells connect to the basal lamina

The reason that pseudostratified columnar epithelium is not stratified

Pseudostratified columnar epithelium

Type of epithelial tissue that typically have cilia and are found in nasal cavities, trachea, and larger airways of the lungs

Stem cell division

How holocrine secretions replace burst cells