Muscle (& epithelia) Flashcards
What are the 4 basic types of tissue?
- Epithelia
- Muscular
- Nervous
- Connective tissue
Where are epithelia found (vaguely)?
As a boundary between controlled internal environment & uncontrolled external environment
What are the 3 germ layers that epithelia can develop from?
Endoderm - e.g. GI lining
Mesoderm - e.g. Lining of CV system
Ectoderm - e.g. epidermis
What is an example of an area of high abrasion where epithelia is found?
Skin
Why is the purpose of epithelia in the lungs?
Aids with diffusion in the lungs
What is the purpose of epithelia in the small intestine?
Aids with absorption
Why is epithelia described as a dynamic barrier?
It is able to import & expel substance, sometimes against concentration gradients.
What connects epithelial cells and creates very low free diffusion to occur?
Tight junctions
What effect does tight junctions have on the location on differing membrane properties & functions?
Leads to the apical & basolateral domains to be polarized
Epithelia is avascular - what does this mean?
- It is entirely cellular (no blood vessels & cells)
- it lacks extracellular fibers
Why do epithelial have minimal extracellular space?
Due to tight packing of junction
What property is CRITICAL to epithelial function?
Polarity
What do basement membranes separate?
Cells from underlying connective tissue (collagen 4)
What attaches epithelia to a basement membrane?
Epithelial cell’s basal surface attaches to a basement membrane.
What is the benefits for epithelia, of epithelia’s basal layer attaching to the basement membrane?
- Provides mechanical support
- Supports the growth & survival of epithelial, through controlling its nutrient, ions, proteins & oxygen.
What does epithelia rely on for their blood supply?
Capillaries in the underlying tissues.
Why is the basement membrane’s ability to regulate growth & division of epithelial cells so important?
Restricts migration of metastatic cells in the progression of cancer
What are the 2 components of the basement membrane?
- Basal lamina
- Reticular lamina
What is the function of the basal lamina?
Provides support by resisting stretching & tearing
What can the basal lamina be subdivided into?
- Lamina lucida
- Lamina densa
What is the function of the reticular lamina?
Anchors basal lamina to connective tissue
What type of movement does tight junction prevent?
Paracellular transport
How do claudins determine the ‘tightness’ of tight junctions?
Different claudins have different levels of permeability (combinations of claudins determine permeability)
Which is more permeable - small intestine or bladder?
Small intestine
How many claudins genes are there?
24
What type of junctions form a belt around the cell?
Adhering junctions
What type of junctions allow lateral communication between cell?
Gap junctions (permit small molecules to diffuse) - therefore cells are electrically coupled
What are desmosomes?
Extracellular domains that form strong adhesion points
What is more likely to occur when the cell experiences a hostile external environment?
Cell death
How long does it take for intestine self-renewal to occur?
5 days
How long does it take for inter-follicular epidermis self-renewal to occur?
4 weeks
How long does it take for lung epithelial self-renewal to occur?
6 months
What are the 2 ways of classifying epithelia?
- Simple epithelia
- Stratified epithelia
What is simple epithelia?
Single layer of cells
Where is an example of simple epithelia?
Lungs
What is stratified epithelia?
Many layers of cells
What are 2 types of non-typical epithelia classification?
- pseudo-stratified (upper respiratory tract)
- transitional (urothelium - found in bladder)
What are the 2 types of simple epithelia?
- simple squamous epithelium
- simple cuboidal epithelia
What is the role of simple squamous epithelium?
Facilitate rapid passage of molecules
Where is simple squamous epithelium found?
Alveoli
What is the difference between simple squamous epithelium and simple cuboidal epithelium?
Simple cuboidal epithelium has a non-motile cilium
What are the 2 types of columnar epithelia?
- simple columnar epithelia
- pseudostratified columnar epithelia
Where are 2 examples of where simple columnar epithelia can be found?
- GI tract
- Fallopian tubes
Which membrane are pseudostratified columnar always touching?
Basolateral membrane
What is the most common type of stratified epithelium in human body?
Stratified squamous epithelia
Which membrane are stratified squamous epithelia always touching?
Apical cells
Where are stratified cuboidal found?
- Glands
- Anus
- Male urethra
- Embryo
What is the function of transitional epithelia?
Facilitates shape change in distension without damaging the epithelial lining
What system is adopted when glands secrete through ducts?
Exocrine system
What system is adopted when glands secrete without ducts?
Endocrine system
What are the 3 substances that can be secreted from glands?
- Mucus
- Protein
- Sebum