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Definition of tissue

(Tissu= woven) are small groups of cells that are similar in structure and preform a common or related function.


What are the 4 basic Tissue types?

1) nervous tissue
2) muscle tissue
3) epithelial tissue
4) connective tissue


What is nervous tissue responsible for?

Internal communication.


What is muscle tissue responsible for?

Contracts to cause movement


What is epithelial tissue responsible for?

Forms boundaries between different environments, protects, secretes, absorbs , filters, excretion, sensory reception.


What is connective tissue responsible for?

Supports, protects, binds other tissues together.


Epithelial tissue definition

A sheet of cells that covers a body surface or lines a body cavity.


What are the 2 types of epithelial tissue ?

Covering/lining epithelium: forms outer layer of skin, forms barriers in open cavities.

Glandular epithelium: fashions the glands of the body


What are the 6 special characteristics of epithelium?

1. Polarity
2. Specialized contacts
3. Supported by connective tissue
4. Avascular but innervated
5. Regeneration
6. Cellularity


Polarity of epithelium

Has Apical surface and basal lamina/basement membrane


Cellularity of epithelium

Epithelium is composed entirely of cells.


Specialized contacts of epithelium

1. Gap junctions
2. Desmosomes
3. Tight junctions


Epithelium is avascular but innervated which means?

It has no blood vessels but it does have nerve endings.


What is special about the regeneration of epithelium cells?

They regenerate quickly


Epithelium always has ______ tissue.

Connective tissue (CT)


What is a gap junction

A communication junction between adjacent cells. Cells are connected by hollow cylinders called connexion a composed trans membrane proteins. Allows simple sugars, ions and small molecules pass through these water filled channels from one cell to another.


What is a tight junction?

A series of integral protein molecules in the plasma membranes of adjacent cells fuse together. To prevent molecules from passing through.


What is a desmosome?

(Binding bodies) Anchoring junctions- like Velcro or zipper hell together by thin linker protein filaments. They bind neighboring cells to make tissues stronger and resist tension and tearing (found in heart)


What are the classifications of epithelial tissue?

1. Simple Squamous (endothelium and mesothelium

2. Simple cuboidal epithelium

3. Simple columnar epithelim

4. Pseudostratified columnar epithelium

5. Stratified squamous epithelium

6. Stratified Cuboidal

7. Stratified columnar

8. Transitional epithelium


What is simple squamous ET? What does it do? Where is it found?

- A single layer of flat squamous cells
- Found where filtration or the exchange of substances by rapid diffusion is a priority.
- Found in kidneys, air sacs of lungs; lining of heart, blood vessels and lymphatic vessels. Lining of central body cavity (serosae)


What is simple columnar et? What does it do? Where is it found?

- a single layer of tall, closely packed cells, aligned like soldiers in a row.
- absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (reproductive cells) by ciliary action.
- Nonciliated type lines most of the digestive tract (stomach to rectum), gallbladder, and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus.


What is simple cuboidal et? What does it do? Where is it found?

- a single layer of cube like cells with large, spherical central nuclei.
- secretion and absorption
-kidney tubules
-ducts and secretory portions of small glands; ovary surface


What is Pseudostratified columnar epithelium? What does it do? Where is it found?

- single layer of cells of differing heights, some not reaching the free surface; nuclei seen at different levels; may contain mucus-secreting cells and bear cilia.
-secrete substances, particularly mucus; propulsion of mucus by ciliary action.
-Nonciliated type in males sperm carrying ducts and ducts of large glands; ciliated variety lines the trachea, most of upper respiratory tract.


What is stratified squamous epithelium? What does it do? Where is it found?

-thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are squamous; in the keratinized type, the surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers.
-protects underlying tissues
-non-keratinized type forms the moist linings of the esophagus, mouth, and vagina; keratinized variety forms the epidermis of the skin, a membrane.


What is transitional et? What does it do? Where is it located?

-resembles both stratified squamos and stratified cuboidal; basal cells cuboidal or columnar; surface cells dome shaped or squamos elite, depending on the degree of organ stretch.
-stretches readily, permits stored urine to distend urinary organ.
-lines the ureters, bladder, and part of the urethra.


What is a gland?

A gland consists of one or more cells that make and secrete a particular product, usually water based, can be steroid based.


Glands are classified by 2 sets of traits. What are they

1. Where they release their product endocrine and exocrine

2. Relative cell number
Unicellular or multicellular



Cancer causing genes


Porto onconogenes

Benign forms of onconogenes in normal cells



New growth