Histology and Epithelial Tissue

What are the types of tissues

Epithelial, connective, muscle, nervous

Define epithelial tissue

* Made of a continuous layer of cells
* Avascular (has no blood cells)
* Attached to a basement membrane
* Has polarity (touches an apical surface and basal surface)

What does a basement membrane do?

Attaches epithelial tissue to connective tissue and acts as a filter in between tissues

What are the intercellular junctions and their functions

1). Tight junctions - close the gaps in between cells

2). Gap junctions - an open channel between cells, promotes communication

3). Desmosomes - attaches to two cells. Attached to intermediate filaments

How do you classify epithelial tissue?

Shape of cells on an apical surface and number of layers

Simple - 1 layer; Stratified - 2 or more layers; Squamous - flat; Cuboidal - circular nucleus; Columnar - oval nucleus

Simple squamous epithelium

Single layer of flat cells, located in areas with lots of diffusion (lungs and kidneys)

Simple cuboidal epithelium

Single layer of cells with a circular nucleus, located in areas with SOME diffusion (glands)

Simple columnar epithelium

One layer of cells with an oval nucleus, often have goblet cells

Goblet cells function

Secrete mucus; function of mucus - protect from harmful substance (pathogens and pollution)

Psuedostratified columnar epithelium

Appears to have many layers, but has only 1 oval shaped nucleus, always has goblet cells and always has cilia

What is the function of cilia?

Small hair-like projections that move mucus

What is the Psuedostratified columnar epithelium composed of?

Tight juctions, gap junctions, desmosomes, cilia, mucus, goblet cells, basement membrane, areolar connective tissue

Stratified squamous epithelium and function

Multiple layers of flat cells, function - provide physical protection against abrasion

Where is non-keratinized stratified squamous epithelial tissue located?

Mouth, throat, anus, vagina

Define keratinized stratified squamous epithelial tissue.

Only in the epidermis, contain keratin, top layer of cells are dead, and there are no nuclei in this layer of skin

Stratified cuboidal epithelium

Multiple layers of cells with a circular nucleus, lines ducts

Transitional Epithelium

Vuboidal when relaxed (empty bladder), squamous when stretched (full bladder), located in the bladder

What are the glands made of?

Simple cuboidal epithelial tissue

What are the 4 glands and their functions?

Serous gland - water secretions (sweat glands)

Mucous gland - secrete mucus (goblet cells)

Mixed glands - serous & mucus secretion (salivary glands)

Oil glands - oil/waxy secretions (ear wax/sebaceous glands)

What is merocrine secretion? (examples)

Products are secreted by exocytosis, non-smelly sweat glands and goblet sells

What is apocrine secretion? (examples)

Mammary glands, prostate glands, and SMELLY sweat glands

What is holocrine secretion?

Sebaceous glands of the skin