Epithelial Tissues: Structure and Function Flashcards
What are conditions in which epithelial function is going wrong ? How so ?
Breast Cancer
Cystic Fibrosis (defective epithelial Cl- ion transport)
Cholera (enhanced activation of epithelialCl- transport)
Atherosclerosis (superficial injury to endothelium)
What are characteristics of epithelial cells ?
- Uninterrupted later of cells (tightly attached)
- Seperated from underlying tissue by BM
- Polarized
- Avascular (nutrients diffuse through BM from capillaries in underlying connective tissue. Limits how thick epithelium may be).
What are the main functions of epithelia ?
Absorption Secretion Transport Selective and Protective barrier Strength and support
How are epithelial tissues seperated from underlying tissues ?
By BM
What are the different kinds of shape of epithelial cells ?
Cuboidal, columnar, and squamous
What are the different kinds of epithelial cells when classified by layer number ?
Simple and stratified
Where would you find simple epithelium ?
At sites where diffusion, absorption or secretion occur.
What are the two kinds of cells in stratified epithelium?
Basal and apical cells
Where would you find stratified epithelium ?
At sites which need protection from abrasion, infection, and caustic content.
Give examples of sites where simple squamous epithelium is used and any distinctive characteristics.
Pavement-like appearance, no gaps between cells.
- Blood vessels (=endothelium),
- Pleura, pericardium (membrane in abdominal cavity) and peritoneum (=mesothelium)
Give examples of sites where simple columnar epithelium is used and any distinctive characteristics.
- Small intestine.
What surface modification does the small intestine show ?
-3 levels of folding:
Large folds (pilicae circulares)
Vili
Microvili (0.5-1.0 micron (forming brush border to which mucus adheres)
-Goblet cells secreting mucus (stains red/purple)
Give examples of sites where pseudo-stratified ciliated columnar epithelium is used and any distinctive characteristics.
-Respiratory Tract
Which other cells does the respiratory epithelium show other than ciliated columnar cells ?
Goblet cells secreting mucus
Basal cells ready to replace superficial one
Give examples of sites where stratified squamous epithelium is used and any distinctive characteristics.
Oesophagus, vagina, anal canal, mouth.
Characteristic of wet epithelia subject to abrasion but NOT dehydration
Basal cells divide and move upward desquamation process occurs
Give examples of sites where keratinised stratified squamous epithelium is used and any distinctive characteristics.
Skin
Top layer still undergoes desquamation
Subject to abrasion AND dehydration
Give examples of sites where transitional epithelium is used and any distinctive characteristics.
Bladder
Cells of basal layer cuboidal or columnar
Cell of apical layer may become squamous to give bladder more elasticity if need to become distend (when empty, apical cells round)
High number of tight junctions prevents leakage of urine into tisses
What is the function of actin in epithelial cells ?
It helps anchor cells (adherens junctions are linked to these).
What are the two main kinds of transport?
Transcellular and paracellular (through intercellular space) ?
What are the different possible roles of tight junctions ?
- Crate barrier between different compartments (i.e. basal vs apical compartments) (Barrier, fence)
- Maitain asymmetric distribution of lipids and proteins in apical basal membranes (differential distribution of transport systems) which enables vectorial transport
- Allows selective movement
-As a result, compartments with different compositions
What are the colors of H and E ?
Haematoxylin stains acidic molecules blue
Eoisin stanins basic molecules pink (cytoplasmic proteins)
What is PAS ?
Periodic Acid Shift, a test for glycoprotein (stains them pink)
Give examples of sites where simple cuboidal is used and any distinctive characteristics.
In the tubules of the kidneys.
What color does PSA stain mucus ?
Red/Purple
What is mesothelium ?
Simple squamous epithelium lining body cavities. Derived from embryonic mesoderm. Provides friction free surface by secreting watery fluid facilitating movement of organ within cavity.
What is mesothelioma ?
Cancer of mesothelium. Usually due to asbestos exposure.
What are intra-abdominal adhesion ? Causes ? Consequences ?
Fibrous adhesions between opposing surfaces due to mesothelium damage causing its inability to remove fibrin deposits. May result in intestinal obstruction (intestine), female infertility (abdomen), impairment to heart/lung function (thorax).
What is the histology of endothelial cells ?
Vesicles involved in process of transport of substances form one side of the cell to other.
Tight junctions linking them
Small flattened nuclei
What are the functions of endothelial cells ?
- Regulation of exchange of substances in blood
- Control of BP
- Help Blood coagulation
- Secrete factors to break down blood clots
- Angiogenesis
- Participate in acute inflammation
Where is fenestrated endothelium found ?
Endocrine glands, kidney.
What are the main pathological implications of smoking on endothelium ?
Smoking causes opening up of junctions (so large molecules can pass through)
How does transport work in the BBB ?
What is the implication of this on infections of the brain ?
Allows entry of essential nutrients, O2, CO2, drugs and anaesthetics through diffusion (lipid soluble molecules) and selective transport through cell by carriers (water soluble molecules).
Since antibodies too large to cross, infections big problem.
Can the BBB be opened ? How so ?
- By hypertension
- By hyperosmolarity
- exposure to microwaves, radiation and infectious agents (including meningitis)
- injury to brain (trauma, ischemia, increased P inside skull)
- Hypercholesterolemia
- Diabetes
What is the implication of increased numbers of goblet cells and increased mucus production ?
Cystic Fibrosis, asthma, or COPD
What is immotile Cilia Syndrome ?
Cilia fail to be beat (or not as well). Mucus not cleared, obstruction occurs. Mucus eventually infected by bacteria. Bacteria release chemicals causing tissue damage. Inflammatory cells cause further local tissue damage.
How does cholera relate affect epithelia ?
Toxins from the bacteria cause opening of ion channels -> Secretions of all kinds of substances into lumen of small intestine —> H2O and electrolytes replaced from blood —> Diarrhea and dehydration
What is metaplasia ? Give examples of sitesin the body in which it may occur.
Change from one distinctive tissue to another at a definite site after development is complete.
May occur in:
1. Epithelia (from pseudostratified to stratified squamous in larynx or trachea due to smoking)
2. Oesophageal stratified squamous to simple columnar after repeated acid reflux.
What is a carcinoma ? Where is it most likely to occur ?
A tumour originating in epithelial cells.
In tissues where brisk mitosis occurs (like the guy)
