3 - Integrating Cells into Tissues Flashcards
What holds cells together in general?
- Cell to cell adhesion
- Close proximity
- Extracellular matrix proteins
What is a tissue and an organ?
- Collection of cells woven together to perform a function
- More than one tissue working together to produce a function
What is the general structure of an organ, in regards to the tissues present?
Epithelia –> Connective Tissue –> Muscle –> Connective –> Epithelia
What is the main differenes between epithelial and connective tissue?
- Connective has large extracellular matrix but epithelial has thin basement membrane
- Cells sparsely spread in connective
- Cells rarely joined in connective but always in epithelia
- In epithelial most of the mechanical stress is on cell-to-cell adhesion but matrix bears most of this stress in connective
What is the progenitor cell for connective tissue?
MSC
What is the function of epithelia?
Sheets that line all the cavities and free-surfaces of the body. Specialised junctions make tissue barriers.
What are the different epithelial cell adherence systems?
Lateral:
- Tight junctions
- Adheren Junctions
- Desmosomes
- Gap Junctions
- Integrins
Basal:
- Hemi-desmosome
- Focal adhesions
- Integrins
- Proteoglycans
Tiny Animals Don’t Give In
What are tight junctions?
- Two tight junction proteins closest to apical surface
- Paracellular transport of large molecules by opening with ATP
- Provides tissue barrier
What are adhesion junctions and their function?
- 1/3 from apical
- Intracellular actin filaments linked to E-cadherin proteins
- Come in pairs, only in endothelial and epithelial
- Calcium ions needed to make these
What are desmosomes and their function?
- Strongest cell-to-cell adhesion
- 1/2 way down
- In cells that experience intense mechanical stress (e.g cardiac, bladder and only ones in skin)
- Cytokeratin intracellularly, E-cadherins intercellularly
What are gap junctions and their function?
- Close to basal surface laterally
- Two transport proteins forming a pore between two cells
- Throughout cardiac and smooth muscle
What are hemidesmosomes and their function?
- Basal layer joining cell to extracellular matrix fibres
- Cytokeratin intracellularly attaching to laminin through integrins
What are focal adhesions?
Same as hemidesmosomes but use actin instead of cytokeratin and attach to fibronectin rather than laminin
What are integrins?
What is the main function of adherance proteins?
- Prevent pathogens entering the internal environment
- Maintain structure and survival of cells
What is the mucosal membrane?
Epithelia (with basal lamina) + Lamina Propria + Muscularis Mucosae
It is an organ that lines all moist hollow internal organs of the body, being continuous with the skin, and it secretes mucus
What is the function of the mucosal membrane and what are some examples of where it is found?
- Prevent pathogens and dirt entering the body (mucocillary escalator)
- Prevent tissues become dehydrated
- Lubrication
e. g genital tract, gi tract, respiratory tract
What are the layers of the GI tract?
1. Mucosal membrane with muscularis mucosae
2. Submucosa
3. Muscularis Externa (circular and longitudinal)
4. Serosa (stop bursting, CT)
5. Epithelia
Label this diagram of the oesphogaus.
How does the wall structure of the stomach differ to that of the oesophagus?
- Mucosa secretes gastric acid, gastrin and digestive enzymes
- Ruggae (to allow expansion)
- 3 layers of muscularis externa (one oblique)
What feature of the epithelium is special to the jejunum?
Plicae circulares
What is the feature of the epithelial in the large intestine (colon) that is special?
Crypts containing large amount of goblet cells
How does the mucosa allow the GI to carry out it’s functions?
- Contains lymphatic tissue
- Epithelial cell specialisations
- Muscularis externa for peristalsis
- Muscularis mucosae to fold mucosa to form large surface area
What epithelial cells line the urinary tract?
- Corpuscle is simple squamous
- Collecting duct is simple cuboidal
Is the mucosal membrane through the whole of the urinary tract?
No - the muscular layer only first appears in the bladder and the ureter
What is the histology of the bladder?
- Transitional epithelia
- Ruggae
- Cells produce mucus and tight junctions to prevent urine damaging underlying tissues
- Lots of fact to act as shock absorber
What is the histology of the urethra?
- Squamous epithelium and then keratinised squamous near opening
- Mucus glands to prevent ingress of pathogens
What is the conducting and respiratory portion of the respiratory tract?
When does the mucosal membrane first appear in the respiratory tract and why does it differ to the mucosal membrsne in the GI tract?
- Trachea
- It has no external smooth muscle layer
What are the secretions in the trachea and what do they do?
What is the histology of the bronchioles?
- Smaller amount of cartilage
- Pseudostratified epithelia
- Seromucous glands in submucosa
- No outer layer of smooth muscle
What is the histology of the alveoli?
- Simple squamous
- Folds in basal lamina so can expand
- All cellsl share same basal lamina
- Fibroblasts lay down collagen and elastin
