L3 : Integrating cells into tissues and organs Flashcards
What holds cells together?
- cell-cell adhesion molecules
- Extracellular matrix protein (fibres)
- Internal-external scaffolding
- Close proximity (pressure effect)
What are the characteristics of connective tissue layer
- extracellular matrix is plentiful
- cells are sparsely distributed
- matrix rich in fibrous polymers
What are the characteristics of epithelial tissue layer?
- Extracellular matrix is scant - only basal lamina
- cells are tightly bound together into sheets - epithelia
What is the primary cell of connective tissue and what is its function?
- MSC
- differentiate into fibroblast - produce extracellular fibres
State the 3 components of connective tissue
- cells
- fibres
- ground substance
State the function of connective tissue
- Protect internal organs
- mechanical support
- transport of substance within body
- insulation
Where is epithelial tissue found in the body?
- lining of all cavities
- free surfaces
What are the types of cell adhrenece both basal and lateral surfaces?
Basal
- Integrins
- Hemi-desmosomes
- Focal adhesion
- proteoglycans
- cell adhesion molecules
Lateral
- Tight junction
- Adheren junction
- desmosome
- Gap junction
- cell adhesion molecules
State the characteristics and functions of Tight junctions
Characteristics
- very top of cell nearest to apical surface in lateral border
- long cell to cell fusion point
Function
- Seals neighbouring cells together in epitheial sheet - prevent leakage of molecules between them
State the characteristics and functions of adhesion junction
Charactersitics
- Almost alwyas 1/3rd distance from apical surface o
- Found in pairs
- formed from intracellular actin filaments
- linked to E-cadherin proteins
- found only in epithelial and endothelial cells
Function
- tissue stabilising factor
- cell to cell actin bundle joining
State the characteristics and functions of desmosome
Charactersitics
- strongest cell to cell adhesion
- found 1/2 between top and bottom of cells
- Cytokeratin fibres intercellularly
- E-cadherins intracellularly
- found in cardiac muscle, GI mucosa
- only cell to cell adhesion found in skin cells
Function
- Provide mechanical strength
- prevent tissue destruction
- cell to cell intermediate filament joining
State the characteristics and functions of gap junction
Characteristics
- close to base of epithelial cells
- distributed throughout cardiac and smooth muscle
- Made of cylinders of proteins(connexins) arranged in hexagonal pattern that open and close (ATP)
Function
- allows free movement of small molecules (cell to cell)
What is the connexin switch that occurs in myometrium of pregnant uterus in preperation for birth?
45 to 34
State the characteristics and functions of Hemi-desmosome
Characteristic
- Attach to layer of extracellular matrix
- Intergrins : Attach Intracellular intermediate filaments of cytokeratin to basal lamina
Function
- Anchor epithelial cells to basal lamina
State the characteristics and functions of focal adhesion
Characteristic
- Uses intracellular actin filament
- binds to fibronectin instead of lamina
- when bound to fibronectin, conformational change results in binding to collagen fibres
Function
- anchors actin filaments in a cell to basal lamina*
State the characteristics and functions of Integrins
Characteristics
- works as alpha-beta dimer
- weak binders of extracellular matrix
- Phosphorylation by focal adhesion kinase produces heterotetramer - stronger bond
What ions are needed for adhesion properties to work?
Ca
What is the definition of mucous membrane?
The combination of epithelium, basal lamina and lamina propia
Give examples of where the mucous membrane is found
- GI tract
- Urinary tract
- Respiratory tract
State the characteristics of mucosal membrane
- lines all moist hollow internal organs
- continuous with skin at body openings
- secrete mucus
State the function of mucousal membrane
- prevent pathogens and dirt from entering body
- prevent body tissues from dehydrated
- lubricate surface
State the layers of the GI tract
*From inwards to outwards
- Mucosa lining the lumen
- Muscularis mucosae
- submucosa - contains blood vessels
- muscularis externa
- serosa - secretes fluid to lubricate outer layer
What is the function of mucosa on GI tract
- abosrb substances from lumen
- prevent entry of pathogens
- move contents and expel water
State the function of key layers in GI tract
- Epithelial cells : microvilli - absorption of food
- Lamina propria : contains lymphatic tissue - expels pathogens
- Muscularis mucosae : folds mucosa - increase surface area
- Muscularis externa : Peristalsis
State the function of urinary tract
- Absorption of nutrients in kidneys
- Prevention of pathogen entry
- remove waste prodcuts
State the layers of the urinary tract
*same as GI tract except
x submucosa, x serosa
What cells are in abundance in the adventitia layer of bladder and what is its function?
- Fat cells
- shock absorber for expanding bladder
State the function of epithelial cells in bladder
- secretes mucus : protects bladder from damage by acidic urine
The respiratory tract is divided into 2 parts. What are they?
*state the start and end of each portions
- Conducting portion : nasal cavity - bronchioles
- Respiratory portion : respiratory bronchioles - alveoli
State the layers of trachea structure
- Mucosa : respiratory epithelium + lamina propria
- Submucosa : collagen, elastin fibres, fibroblast
- Cartilage : Perichondirum, chrondrogenic layer
State the characteristics of secondary and tertiary bronchi
* similar to trachea except..
- cartilage not present as full
Describe the structural characteristics of alveolus
- Capillaries : lined with endothelial cells attached to a fused basal lamina
- Basal lamina : folded - allow expansion of air sacs when air drawn in
- Junctions : collagen - add rigidity to mucosa
- Elastin fibres : provide elastic recoil - return sac to empty state
When do cells coalesce?
During embryogenesis
What is a mesenchymal stem cell?
- Stem cell of connective tissue.
- Pluripotent.
- Can convert into different cell types
What is submucosa?
Connective tissue containing artery and vein
What is muscularis externae?
Has muscle fibres going in 2 directions
- inner circular muscle
- outer longitudinal muscle
What is the musculare mucosa?
- Thin layer
- seperate mucuousal layer from submucosa
Where is muscle present in urinary tract?
- Ureter
- bladder
Why is there thick layer of muscle in urinary tract?
Prevent bladder from bursting
What is mucous made of?
Mucin, water, electrolytes, antiseptic enzymes, immunoglobulins
What do secretions from epithelium and submucosal gland in trachea contain?
- mucins
- water
- lysozyme
