Epithelial Tissue Flashcards
Describe the composition of microvilli. What proteins are present? Where are they located?
core is formed by actin filaments bound together by fimbrin and fascin, and are anchored to the membrane by myosin I
The apex is formed by villin
(striated border of small intestine and brush border of kidney)
What are the 3 major characteristics of epithelial tissue?
- An exposed free surface
- little to no extracellular matrix
- avascular
Describe the composition of stereocilia. Where are they found?
core formed by actin filaments (similar to microvilli)
(Epididymis and ear cochlea)
Describe the composition of cilia. Where are they located?
10 pairs microtubules that form the axoneme
At its base, each cilium is attached to the centriole (basal body, which is formed by 9 triplets of microtubules w/o a central pair)
Respiratory tract and oviduct
What disease is cause by a genetic defect of ciliary proteins? What are the consequences of this disease?
primary ciliary dyskinesia
- embryological pathologies
- impaired development skull sinuses
- no mucus removal from lungs
- infertility
How are junctional complexes visualized with a light microscope?
terminal bars
What type of cell junction is formed by sealing strands of transmembrane proteins that bind membranes of 2 adjacent cells? What is the major function of this type of junction?
occluding junctions; zonula occludens virtually impermeable, prevent diffusion by blocking paracellular pathways
Found in cells w/ secretory or absorptive role
What type of anchoring junction connects the actin filaments of adjacent cells? What actin binding proteins are present? Peripheral protein? Transmembrane link protein?
Zonula adherens
Actin binding: vinculin, alpha actinin
peripheral: catenin
Transmembrane link : cadnerin (Ca++ dependent, loss is associated with cancer)
What type of anchoring junction connects the intermediate filaments of two cells? Where are they commonly found? Intracellular plaque? Transmembrane proteins? What disease is caused when these junctions fall apart?
desmosomes (macula adherens) skin and muscles
intracellular plaque: desmoplakin that IF go through
transmembrane proteins: cadherin pemphingus (mucous membrane blistering)
What type of junction allows for diffusion of small molecules and ions between cytoplasm of adjacent cells? describe the composition of these channels
communicating or gap junctions each channel formed by a pair of connexons each connexon is composed of 6 subunits, connexins
What is the function of the basement membrane? What are its 2 layers?
separates epithelium from underlying connective tissue
- Basal lamina: most external; belongs to epithelium (collagen IV and laminin)
- Reticular lamina: deep layer; belongs to connective tissue (thin collagen fibers)
What type of anchoring junction connects the actin cytoskeleton of a cell to the extracellular matrix? actin-binding protein? peripheral protein? transmembrane protein?
Focal adhesions
actin-binding: vinculin and alpha-actinin
peripheral protein: talin (actin binding to transmembrane)
transmembrane: integrin (Ca++ independent)
What type of anchoring junction connects the intermediate filaments of the cell cytoskeleton to the extracellular matrix? intracellular plaque? transmembrane proteins?
Hemidesmosome
intracellular plaque: desmoplakin
transmembrane proteins: integrin family
Where are simple squamous epithelium found and what is its major function?
lining vascular system, body cavities, parietal layer of Bowman’s capsule, alveoli of lungs
- barrier
- diffusion of oxygen and carbon dioxide
What is the name for simple squamous epithelium that lines walls of blood vessels and the heart? What is the name for simple squamous epithelium that cover internal organs (pleural, pericardial and peritoneal cavities
- endothelium
- mesothelium
Where is simple cuboidal epithelium most commonly found? What are its major functions?
walls of ducts of glands, kidney tubule, germinal epithelium of ovary and thyroid follicles
- barrier
- secretion
- absorption
Where are the 2 types of simple columnar epithelium found? What are the main functions of this type of epithelium?
non-ciliated: lining gastrointestinal tract and walls gallbladder
ciliated: lining oviduct
1. absorption
2. secretion
3. lubrication
4. transport
Where are the 2 types of pseudo-stratified columnar epithelium found? What are the main functions of this type of epithelium?
ciliated: respiratory tract (move mucous up respiratory tract)
non-ciliated: epididymis (has stereocilia that are used for absorption)
What is it called when ciliated pseudo-stratified columnar epithelium change into stratified squamous in the respiratory tract? What group of people is this most commonly found in?
metaplasia (can occur in other epithelia as well) common in heavy smokers leads to accumulation of mucus and inflammation
What are the 2 types of stratified squamous epithelium? What is the main function of this type of epithelium?
forms a barrier between the environment and the underlying tissue
- keratinized: presence dead cornified layer on the surface (epidermis of skin)
- non-keratin: does not have a dead layer (oral cavity, esophagus, vagina)
Where is transitional epithelium found? What is the major purpose of this type of epithelium?
only found in urinary system it is able to stretch enormously, so the shape of the epithelium changes from rounded cuboidal to squamous
How is glandular epithelium formed? What happens next?
invagination of epithelial tissue then epithelial cells start secreting various materials (mucins, steroids, etc.)
What type of glands secrete their product into intracellular space or underlying connective tissue to diffuse into blood? What type of gland maintains connection to originating epithelium and secretes into ducts/spaces lined with originating epithelium?
endocrine (no ducts, arranged in chords along capillaries)
Exocrine (arranged into acini or tubules)
What are the 3 major types of exocrine glands?
-
Merocrine: secretory product delivered in membrane-bound vesicles to apical surface, release via exocytosis
- serous: thin, watery, protein rich secretion; well developed rough ER, pyrimidal cell shape so acini are rounded in shape (pancreas and parotid salivary gland)
- mucous: mucins (viscous, used for lubrication & protection); not well developed rough ER, columnar in shape so glands are generally tubular (goblet cells, glands soft palate, Brunner’s glands)
- mixed: mucous cells form tubules capped by serous cells that orm serous demilunes (submandibular salivary gland)
- Apocrine: pinchign of apical cytoplasm with formaiton of secretory cesicel (mammary gland)
- Holocrine: as cell acuulated secretory product, goes through apoptosis, which releaseds cellular content (sebaceous glands of the skin)
What are the most common type of unicellular glands? Where are they located and what do they secrete?
Goblet cells
secrete mucous; found w/in columnar epithelium of GI and respiratory tract
What is the term for the terminal part of hte invagination for multicellular exocrine glands? What are the 3 shapes for this portion?
WHat is the name for the portion that connects it to the surface?
- secretory portion
- shaped like flask: alveolar/acinar (serous)
- shaped like tube: tubular (mucous)
- shaped with a secretory tube ending in a flask dilation: tubuloalveolar (mixed)
- duct
What are the contractile cells present in gland between the basal lamina and the secretory portion of gland and ducts?
myoepithelial cells (sweat glands, salivary glands, mammary gland)
What are the 2 principal types of cancers derived from epithelial tissues?
- carcinoma: barrier epithelium
- adenocarcinoma: glandular epithelium
