Tissues 2- Epithelial Tissues Flashcards
What does the epithilal layer lie on?
Basal lamina
What is under the lamina
Under the lamina you have interstitial connective tissue and extracellular matrix.
Describe and give examples of the Simple squamous
e.g. lung alveolar, mesothelium, endothelium
SQUAMOUS = FLAT (wider than they are tall)
It is only a single layer so it is SIMPLE
This is SIMPLE SQUAMOUS EPITHELIUM
Describe and give examples of the Simple cubodial
Simple Cuboidal e.g. kidney collecting duct
SIMPLE = One cell layer thick
CUBOIDAL = as wide as it is tall
Describe and give examples of the Simple Columnar
Simple Columnar e.g. enterocytes
SIMPLE = One cell layer thick
COLUMNAR = taller than they are wide
Describe and give examples of the Stratified Squamous
STRATIFIED = lots of layers of cells
The cells have a variety of shapes - they are quite cuboidal near the basal lamina and quite flat at the surface.
The surface cells are use for the description therefore this is SQUAMOUS.
Two Main Types of Squamous Epithelia:
Keratinizing - e.g. epidermis (nuclei NOT VISIBLE in the surface cells)
Non-Keratinizing - e.g. linings of mouth (exactly the same but the nuclei are visible in surface layer cells)
Describe and give examples of the Pseudostratified Columnar Epithelium
e.g. upper airway (bronchi) epithelium
There appear to be two layers of cells in the micrograph.
On further investigation, they found that all the cells are in contact with the basal lamina.
Why is Epithelial Polarity important?
Polarity is key for secretion, transport, absorption etc. because all these processes are usually unidirectional.
Polarity gives the directionality to epithelial function.
It is the polarity of the plasma membrane which allows the functions to take place.
The junctions are important in allowing the cells to maintain polarity.
Describe the effect of polarity on the pancreas
Secretory Tissues
The pancreas has both exocrine and endocrine functions.
Exocrine = apical —> duct
Endocrine = basal —> circulation
Describe Cell Division in the Villus
ISC - Intestinal Stem Cells
ISCs are present in the crypt
There is a constant turnover of cells.
Cells are lost at the tip and are produced in the crypt.
It acts like an escalator - as the cells mature they move up towards the tip of the villus.
The two ways in which cells secrete materials can be classified as:
CONSTITUITIVE - secretory vesicles, as they are formed, move directly to the plasma membrane and release their contents e.g. production of plasma proteins by hepatocytes (constituitive endocrine secretion)
STIMULATED - secretory vesicles are stored in the cytoplasm and only fuse with the plasma membrane to release their contents when stimulated. E.g. the release of adrenaline from cells of the adrenal medulla after a fight-or-flight stimulus (stimulated endocrine secretion)
What type of epithelial is involved in protection?
STRATIFIED SQUAMOUS EPITHELIA (both keratinizing and non-keratinizing).
Describe how the skin is a barrier
The skin consists of three main layers: epidermis, dermis and hypodermis
The epidermis is the keratinizing stratified squamous epithelial layer.
It acts as an important BARRIER to the environment and to mechanical damage.
The cells in the skin go through a programme of differentiation as they move up towards the surface.
When subject to mechanical irritation the stem cells are stimulated to proliferate to replace the lost cells.
Describe keratinizing cells
Keratinizing - no nuclei visible in surface layer cells - they are dead cells and are made very tough by the production of several keratin proteins and lipids - this gives a dry protective quality.
