Epithelial Tissue Flashcards
Name the types of epithelial tissue
Simple squamous Simple cuboidal Simple columnar Stratified squamous Stratified cuboidal Stratified columnar Pseudo-stratified columnar Transitional
Describe simple squamous tissue?
Thin and flat with flat disc nucleus
Permeable
^ facilitate diffusion, only possible function
Found in alveoli, glomerulus, endothelium and mesothelium
endothelium - cells that line the interior surface of blood vessels
mesothelium - membrane composed of simple squamous epithelium that forms the lining of several body cavities: the pleura (thoracic cavity), peritoneum (abdominal cavity including the mesentery), mediastinum and pericardium (heart sac)
Describe simple cuboidal tissue?
Cube with a spherical nucleus
Secrete and absorb
Found in nephron lining, thyroid, salivary glands, ovary surface
Describe simple columnar tissue?
Column shaped, elongated nucleus and contain cilia that help movement of mucous
Secrete digestive enzymes and absorb digested food
Found in stomach, intestines and endometrium (the inner lining of the uterus)
Describe stratified squamous tissue?
Multiple layers of flat cells
keratinized or not
Only available function is protection
Keratinized tissue found in skin, dead layers of cells that are expendable
Non keratinized found in moist linings: mouth, oesophagus, vagina
Describe stratified cuboidal tissue?
Multiple layers of cuboidal
Secretion + Reabsorption
Found in mammary glands
Describe stratified columnar tissue?
Multiple layers of columnar
Protection + secretion
Urethra
Describe pseudo-stratified columnar tissue?
‘Multiple’ looking layers of cells. ALL connect with basement membrane
Secretion
Large glands like sperm carrying ducts and trachea
Describe transitional tissue?
Resemble both stratified squamous and stratified cuboidal
Has elastic properties
Urethra, urinary bladder (stretch)
What are the 6 functions of epithelial tissue?
Protection Absorption Filtration Excretion Secretion Sensory
Example of protection?
Skin epidermis - Stratified squamous e.g.
Gut lumen
Example of Absorption?
Intestines - absorb nutrients
Example of filtration?
Respiratory tract - filters air
Example of excretion?
Skin - sweats and oils
Example of secretion?
All glands are made of epithelial tissue - thyroid, pineal gland
Example of sensory?
Ear and nose
Describe a tight junction
Forms the continuous intercellular barrier between epithelial cells, which is required to separate tissue spaces and regulate selective movement of solutes across the epithelium
Describe an adhesion belt
The adhesion belts are directly apposed in adjacent epithelial cells, with the interacting plasma membranes held together by the cadherins that serve here as transmembrane adhesion proteins
Describe a desmosome protein
Desmosomes are intercellular junctions that provide strong adhesion between cells. Because they also link intracellularly to the intermediate filament cytoskeleton they form the adhesive bonds in a network that gives mechanical strength to tissues
What is the difference between an adhesion belt and a desmosome?
Adhesion belts are involved in dynamic cell interactions in development and disease, whereas desmosomes are responsible for strong adhesion in epithelia and cardiac muscle
Describe a hemidesmosome
Similar to desmosomes but anchor cell to basement membrane
Stop cells lifting off
Describe a gap junction
Small pores / tubes
Allow chemical communication between cells
Contains connexons (made of connexins)
Describe a connexon
Also known as a connexin hemichannel, is an assembly of six proteins called connexins that form the pore for a gap junction between the cytoplasm of two adjacent cells. This channel allows for bidirectional flow of ions and signaling molecules
What are the cell junction transmembrane glycoproteins?
Adherin + Integrin
Adherin: Part of the adhesive belt; Attaches to actin microfilaments on the cytoskeleton; binds adjacent cells
Integrin: attaches to actin microfilaments on the cytoskeleton; Within hemidesmosomes, attach cell to basement membrane
