Epithelia Flashcards
1
Q
Function of epithelia
A
- Line surfaces and form barriers
- Between us, surfaces and different components within our bodies.
2
Q
What are epithelia comprised of?
A
Cohesive sheets of cells with 1 or more layers thick, resting on a basement membrane
3
Q
What do epithelia form barriers for?
A
- Protection-skin
- Absorption-gut
- Secretion-pancreas
4
Q
Difference between Simple and Stratified epithelia
A
Simple comprises of a single layer of cells on a basement membrane whereas Stratified comprises of 2 or more layers of cells on a basement membrane.
5
Q
What are the 3 types of Simple epithelium?
A
- Simple squamous epithelium
- Simple cuboidal epithelium
- Simple Columnar epithelium
6
Q
Simple squamous epithelium
A
- Single layer of flattened plate-like cells on a basement membrane.
- Nuclei-parallel and oval. Thickest part of cell. 1 per cell.
- Lines inside of blood vessels (endothelium)
- Lines outside of lungs (mesothelium)
- Lines abdominal organs (peritoneum)
- Found in lung alveoli-form barrier between air & blood.
- Thin cytoplasm
7
Q
Simple Cuboidal epithelium
A
- Single layer of cells with similar h & w on a basement membrane.
- Have central spherical nuclei, 1 per cell
- Line kidney tubules, small ducts
8
Q
Simple Columnar epithelium
A
- Single layer of cells, taller than they are wide, resting on a basement membrane
- Line stomach, small intestine and uterus
- Each cell has nucleus
- Might have cilia/microvilli-increase S.A for absorption or move material across epithelium.
9
Q
Microvilli
A
- Microscopic projections on luminal surface of absorptive cells
- Increase S.A. across which absorption of water and nutrients can take place
- Intestinal brush border
10
Q
Cilia
A
- Microscopic projections on luminal surface of cells.
- Long, hair like projections that line airways
- Contain contractile proteins-allow cilia to rhythmically beat
- Coordinated movements of cilia waft material, which on surface of epithelium, across it, all in same direction
- In Fallopian tube-have simple columnar epithelium resting on basement membrane. Have cilia which waft fluid & fertilised ovum from direction of ovary towards uterine cavity.
11
Q
Types of Stratified epithelium
A
- Stratified squamous non-keratinising epithelium
- Stratified squamous keratinising epithelium
- Pseudostratified epithelium
- Urothelium- specialised stratified epithelium
12
Q
Function of Stratified Epithelia and sites it can be found
A
- Protective-has many layers of cells continually being worn down, worn away cells replaced from below.
- Found at sites exposed to frequent frictional forces e.g. sites where abrasion-skin, mouth, oesophagus, vagina and cervix.
13
Q
Stratified squamous non-keratinising epithelium
A
- Multiple layers of cells on basement membrane.
- Layers are thin and plate like.
- Lines mouth, oesophagus, vagina etc
- Keratin-protein which helps waterproof epithelium
- Wet sites of body, where there is no need for waterproofing-don’t find keratin.
- Cells start life against basement membrane, as they mature, flatten out become squamous.
- Vagina-epithelial cells accumulating glycogen at various points in menstrual cycle-gives cytoplasm pale appearance.
14
Q
Stratified Squamous Keratinising Epithelium
A
- Keratin found in waterproof places-skin
- Multiple layers of cells on basement membrane.
- Mature surface layers become flattened plate like squamous as mature and move up from basement membrane towards surface.
- As keratin accumulates within cell-cells die. Left with dead flat plates of keratin.
- Thin skin-eyelids
- Thick skin-palms of hands and heels of feet-dense layer of keratin.
15
Q
Pseudostratified epithelium
A
- Single layer of cells at variable heights, mimicking multiple layers on a basement membrane.
- Nuclei at different heights
- All cells in contact with basement membrane therefore appears as single layer.
- Lines conducting airways-ciliated pseudostratified columnar stratified epithelium-known as respiratory epithelium.
