Epithelial cells Flashcards
What are cancers starting in epithelial cells called
Cancers originating from epithelial cells are carcinomas
What are cancers starting in mesenchymal cells called
Cancers originating from mesenchymal cells are sarcomas
What are cancers starting in haematopoietic cells called
Cancers originating from haematopoietic cells are called leukaemias or lymphomas
What are cancers starting in neural cells called
Cancers originating from neural cells are called neuroblastomas or gliomas
What are the functions of epithelial layers and how are they maintained
Epithelial layers outline external and internal surfaces and serve for transport, absorption, secretion and protection. Epithelial cells are bound together by distinct cell-to-cell junctions.
What are the three shape classifications of epithelial cells
There are squamous, cuboidal and columnar epithelial cells
What are the layer classifications in epithelial cells
There is simple and stratified epithelium
What is function of simple squamous epithelium and where is it found
Simple squamous epithelium is used for exchange of substances between tissues, it is found in alveolar epithelium, mesothelium around body cavities and vascular endothelium of blood vessels
What is simple cuboidal epithelium and where is it found
Simple cuboidal epithelium consists of a single layer of cube shaped epithelium and is found lining ducts, for example renal collecting ducts
What is function of simple columnar epithelium and where is it found
Simple columnar epithelium is involved in absorption and secretion of substances and is found for example in digestive system in the intestines
What are the two main types of stratified squamous epithelium and where are they found
The two main types of stratified squamous tissue are keratinising and non-keratinising and they are found respectively on the skin and mucous membranes
What is pseudo-stratified epithelium and where is it found
In pseudo-stratified epithelium it appears that there are multiple layers of cells, but they are all in contact with the basal lamina. This is found for instance in the cells lining the trachea and bronchi and ducts in urinary system
What is apical and basolateral domain of epithelial cell
The apical domain of epithelial cells is directed towards internal lumina or external space, while the basolateral domain is directed towards the basement membrane and the extracellular matrix
What is the function of epithelial polarity
Epithelial polarity ensures that substances are permeable only in one direction to enable directional movement of substances needed for metabolic processes
What are the four types of cell-cell junction between epithelial cells and their function
Tight junctions are the most apical junctions and prevent leakage of solutes and water via the paracellular routes. Adherens junctions are involved in stabilising cell-cell adhesion and signalling regulation. Desmosomes form spot junction that are mechanically strong to resist forces in epithelial layers that experience many mechanical forces. Gap junctions are the most basolateral junctions and form pore connections between cells to enable substance exchange between adjacent cells and form communities.
Which cell-cell junctions are called spot junctions
Desmosomes are called spot junctions because they form junctions randomly along the lateral membranes between epithelial cells
Where are the mitochondria of transporting epithelial cells found and how is basal membrane increased
The mitochondria of transporting epithelial cells are found on the basolateral domain because active transport takes place on this side of the cell. The basal membrane contains basal folds to increase the surface for substance transport by transport proteins
How is directionality achieved in transporting epithelial cells
Because active transport only takes place at the basal membrane, it can be regulated in which direction substances are transported
In what three ways is the absorption surface area of the intestine increased
By the fact that the intestines are long, the absorption surface area is increased, and by finger-like folds called villi that are lined by the intestinal absorptive enterocytes. These cells then also contain microvilli on their apical membrane to increase the surface for transport.
What secretory cells are interspersed with enterocytes of intestinal villi
Goblet cells that secrete mucus that lubricates and protects the intestinal wall
On what side of cell are carrier proteins found in absorptive epithelium like enterocytes and kidney proximal tubule cell
In absorptive epithelium like enterocytes and kidney proximal epithelium the carrier proteins are found on the apical brush-border to extract substances (nutrients) from the luminal environment
Where is the brush-border membrane found in these cells and what does it contain
The brush-border membrane is found on the apical side of absorptive epithelium of the intestines and kidney and the cell membrane contains microvilli
What cells in pancreas secrete digestive enzymes
Acinar cells in the pancreas carry out exocrine secretion of digestive enzymes like trypsinogen and chymotrypsinogen and lipases and amylase
On what side of exocrine secretory epithelial cell are capillary, nucleus and secretory granules
Capillary is found on the basal side of the secretory epithelial cell, the nucleus is also found in the basal side of the cell and the secretory granules lie ready for secretion on the apical side of the cell
What cell organelle is particularly large in secretory epithelial cell
The rough endoplasmic reticulum is very extensive and is found on the basal side of the cell
On what side of endocrine secretory epithelial cell are capillary, nucleus and secretory granules
In endocrine secretory epithelium, the capillary is found on the basal side of cell and secretory granules lie ready on the basal side as well. The nucleus and ER are found on the apical side of the cell
In what categories can secretory epithelial cells also be divided
Based on their function secretory epithelial cells can also be divided into constitutive secretory epithelium in which produced vesicles immediately are exocytosed and stimulated secretory epithelium where the secretory granules are only released when the cell is stimulated to do so
How is the turning-over of epithelium counteracted
By rapid proliferation of stem cells in the epithelial layer
How do intestinal crypt cells replace tip of villi
Crypt stem cells within the intestinal crypts rapidly divide to replace the enterocytes on the villi that are lost due to mechanical forces within the intestinal lumen. The newly produced enterocytes slowly move up the villus as the cells towards the top are lost due to mechanical abrasion
How does proliferation of intestinal crypt cells relate to gastro-intestinal side effects in chemotherapy
The rapidly dividing intestinal crypt stem cells are inhibited or killed by chemotherapeutic agents and this results in loss of villi in the intestines as the lost cells cannot appropriately be replaced, which results in reduced uptake of nutrients in digestion
What are the four cell layers of the epidermis
The layer above basement membrane is the basal cell layer which divides. Above that is the prickle cell layer which contains many desmosomes as a protective layer and Langerhans cells. Above that is the granular layer which contains cells that produce keratin and lipids to provide hydrophobic protective layer. Last are the keratinised squames which consist of dead keratinised cells.
How does epidermis respond to repeated or constant pressure
In areas of repeated or constant pressure on the skin, the basal layer will proliferate more and result in a thicker layer of keratinised cells to form a better protective layer
What infectious agent can cause hyperproliferation in epithelial stemcells
The human papillomavirus can cause epithelial stem cells to proliferate locally which results in surface growth, for example in warts
