Epithelial Tissue Flashcards
Tight Junctions
Impermable junctions that prevent molecules from passing through the intercellular space
Ex: Blood-Brain barrier
Desmosomes
Anchoring junctions bind adjacent cells together like a molecular “Velcro” and help form an internal tension-reducing network of fibers
Composed of Cadherin (Linker proteins), Plaque, and Keratine (intermediate filament)
Gap Junction
Connexon proteins allow ions and small molecules to pass for intercellular comunication
Which Intercellular junction is most likely to be found on a horizontal structure? Vertical structure?
Horizontal: Gap Junction
Vertical: Desmosomes
Gap on the Horizon, Spiders on a String
Apical Surface
Upper Free; exposed to exterior of cavity
Basal Surface
Lower attached;
Stages of Tissue Repair
- Inflammation Stage
- Proliferation Stage
- Regeneration Stage
Describe the Inflammatory stage in Tissue Repair
- Severed blood vessels bleed
- Inflammatory chemicals are released
- Local blood vessels become more permeable, allowing WBC, Fluid, Clotting proteins, and other plasma proteins to seep into the injured areas
- Clotting occurs; surface dries and forms a scab
Describe what happens during the Proliferation Stage of Tissue Repair
- The clot replaced by granulation tissue, which restores the vascular supply
- Fibroblast produce collagen fibers that bridge the gap
- Macrophages phagocytize dead and dying cells and other debris
- Surface epithelial cells multiply over the granulation tissue
Describe what happens during the Regeneration Stage of Tissue Repair.
- The fibrosed area matures and contracts; the epithelium thickens
- A fully regenerated epithelium with an underlying are of scar tissue
7 Epithelial Tissues
- Simple columnar
- Ciliated pseudostratified columnar with goblet cells
- Simple cuboidal
- Transitional
- Simple squamous
- Stratified squamous
Keratinizing stratified squamous
Simple Columnar E.T.
Singe layer of tall cells with round to oval nuclei; may have contain microvilli and/or goblet cells
What is the Function of Simple Columnar?
Absorption; Secretion of mucus, enzymes, and other substances
Where are Simple Columnar E.T. generally located?
Nonciliated types: lines most of the digestive tract (stomach to rectum), gallbladder, and excretory ducts of some glands
Ciliated types: line small bronchi, uterine tubes and some regions of the uterus
Pseudostratified Columnar E.T.
Single layer of cells of differing heights, some not reaching the free surface; nuclei seem at different levels; may contain mucus-secreting cells and bear cilia
What is the function of Pseudostratified Columnar E.T.?
Secrete substances, particularly mucus; propulsion of mucus by ciliary action
Where are Pseudostratified Columnar E.T. Generally located?
Nonciliated type: in male’s sperm-carrying ducts and ducts of large glands
Ciliated types: Line the trachea, most of the upper respiratory tract
Simple Cuboidal E.T.
Single layer of cube-like cells with large, spherical central nuclei.
What is the function of Simple Cuboidal E.T.?
Secretion and absorption
Where are Simple Cuboidal E.T. generally located?
Kidney tubules; ducts and secretory portions of small glands; ovary surface
Transitional E.T.
Resembles both stratified squamous and stratified cuboidal; Basal cells cuboidal or columnsar; Surface cells dome shaped or squamous-like, depending on degree of organ stretch
What is the function of Transitional E.T.?
Stretches readily, permits stored urine to distend urinary organ
Where are Transitional E.T. generally found?
Lines the ureters, bladder, and part of the urethra
Mesothelium (Simple Squamous E.T.)
Located: in the mesothelia lining ventral body cavity, endothelia lining heart and blood vessels and portions of kidney tubules, inner lining of the cornea and alveoli of lungs
Function: reduces fiction; controls vessel permeability; performs absorption and secreation
Simple Squamous E.T.
Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; the simplest of the epithelia
What is the Function of Simple Squamous E.T.?
Allows materials to pass by diffusion and filtration in sites where protection is not important; Secretes lubrication substances in serosae
Where is Simple Squamous generally located?
Kidney glomeruil; air sacs of lungs; lining of hearts, blood vessels, and lymphatic vessels; lining of ventral body cavity (serosae)
Stratified Squamous E.T,
Thich membrane composed of several cell layer; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (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.
What is the function of Stratified Squamous E.T.?
Protects underlying tissue in areas subjected to abrasion
Where are Stratified Squamous E.T. generally located?
Nonkeratinized type forms the moist lining of the esophagus, mouth, and vagina
Keratinized type: forms the epidermis of the skin, a dry membrane
Endocrine Glands
Ductless glands that internally secrete protein hormones or steroid hormones
ex: blood, Interstitial fluid, lymph
