Lecture 3 Epithelia 1 Flashcards
Epithelial tissus
Cellular
Polar asymmetry - upper diff from lateral or base
Avascular- no blood vessels
Covering layer e.v. tube lumens, surfaces, cavities
Glandular, secretory glands
Bound together by specialised cell junctions
Supported by basement membrane separating cells from other tissues
Basal/ lateral/ apical
B: communicates w/other cells
L: side of cell
A: top of cell, microvilli
Polarity
Nuclei have specific positions related to type of cell they are in. In epithelial cells nuclei are close to basal side
Proteins take specific positions in columnar epithelium. Cells invest energy to ensure this so diff proteins delivered to diff membrane surfaces.
Composition of membranes vary e.g. digestive enzymes localise to microvilli in gut lumen epithelium.
Simple epithelium
One cell thick
All cells in contact w/basal membrane
Selective diffusion/ absorption/secretion
Stratified epithelium
Multi cell layer
Only base layer in contact w/basal membrane
Form protective surfaces
Apical later determines classification.
Psuedo-stratified
Appears multilayered but is only one cell thick (therefore simple)
All cells in contact w/basement membrane but not all cells in contact w/lumen
Confined to larger airways of the respiratory tract
Keratinisation
Basal layer stem cells move up to surface where they are keratinized (lose nuclei) or stay alive on surface ( non- keratinized)
Surface specialisation
1) exchange epithelia: simple squamous, thin and flat for gas exchange ( blood vessels & lungs)
2) transporting epithelia: selective non-gaseous (ion/nutrient) material exchange ( GI tract, kidneys)
3) ciliated epithelia: non transporting, move fluids and particles across tissue ( mucous in resp tract and female repro tract)
4) protective: stratified all cell shapes (epidermis, mouth lining, pharynx, oesophagus, urethra, vagina)
5) secretory: release secretion into extracellular space can be isolated or in groups (glands)
Exocrine - w/duct. Serous (watery) tears sweat and digestive fluid or mucous: sticky containing glycoprotein and proteoglycan
Endocrine: ductless hormone secretors (pancreas, thyroid, gonads)
Simple squamous covering epithelium
Passive transport of gas/fluid
As in alveolar mesothelium and endocardium
Simple cuboidal epithelium
Excretory/secretory/absorptive
In kidney, salivary gland, pancreas, thyroid, follicles
Simple columnar epithelium
Secretory/absorptive. In stomach and small intestine.
Simple ciliated columnal epithelium
Allows movement of material over the surface ( as in fallopian tube and trachea)
Psuedo-stratified ciliated epithelium
Movement of materials over surface as in lungs
Stratified covering epithelium: non keratinised
Non keratinised stratified squamous: protective, found in oral cavity oesophagus cervix vagina.
As cells approach surface they become packed with sugar
Cell suicide releases the sugar onto the surface feeding beneficial bacteria that digest sugar and release lactic acid
Stratified covering epithelium: keratinised
Keratinosis not understood, cells on surface lose their nuclei and become keratinised forming a tough protective barrier
typical features & functions of epithelium compared to connective tissue
Definition
Epithelium - in animal tissue lines internal and external surfaces of organs and cavities
Connective tissue - in animal tissue connects and separates tissues and organs of the body
Origin
E- Ectoderm
C- Mesoderm
Basement membrane
E - cells rest on basement membrane
C - cells do not rest on a basement membrane
Functions
E - lining internal/external surfaces of the body, secretion, selective absorption, protection, transcellular transport and sensing
C - supports and connects organs and tissues, insulation of body, producing blood and lymph and supplies nutrients and oxygen to other tissues
Vascular/Avascular
E - Avascular
C - Vascularised
