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Body Logistics > Lecture 7: Integrating cells into tissues, organs and systems > Flashcards

Lecture 7: Integrating cells into tissues, organs and systems Flashcards

1
Q

What holds cells together at the molecular level?

A
  • Cell-cell adhesion molecules
  • Extracellular matrix proteins (fibers)
  • Internal-external scaffolding
  • Close proximity (pressure effects)
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2
Q

What are the epithelial cell adherence systems in the lateral surface?

A
  • Tight junctions
  • Adherens junctions
  • Desmosomes (adhesion plaque)
  • Gap junctions
  • Cell adhesion molecules
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3
Q

What are the epithelial cell adherence systems in the basal surface?

A
  • Hemi-desmosomes
  • Focal adhesions
  • Integrins
  • Proteoglycans
  • Cell adhesion molecules
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4
Q

Where are tight junctions found?

A

Always at the very top of the cell nearest to the lumen or apical surface in the lateral border

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5
Q

What are the key features of tight junctions?

A

Relatively long cell-to-cell fusion point

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6
Q

What is the role of tight junctions?

A

Seals neighboring cells together in an epithelial sheet to prevent movement of larger molecules through the outer layer/lumen into the deeper tissue layers of the organ

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7
Q

Where are adhesion junctions found?

A

Almost always found 1/3rd distance from luminal surface

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8
Q

What are the features of adhesion junctions?

A
  • In lateral surface
  • Found in pairs
  • Formed from intracellular actin filaments
  • Linked to E-cadherin proteins that cross the intercellular space
  • Also known as ‘adhesion belt’
  • Found only in epithelial and endothelial cells
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9
Q

What is the role of adhesion junctions?

A

Functions as tissue stabilizing factor and additional transport barrier by joining an action bundle in one cell to a similar bundle in a neighboring cell

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10
Q

Where are desmosomes found?

A

Halfway between top and bottom of cells

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11
Q

What are the features of desmosomes?

A
  • Strongest of all cell-to-cell adhesions
  • Random distribution pattern
  • Found in tissues that experience intense mechanical stress
  • Made of cytokeratin fibers intracellularly and E-cadherins intercellularly
  • Only cell-to-cell adhesion found in epidermal cells
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12
Q

What is the role of desmosomes?

A

Provide mechanical strength and prevent tissue destruction by joining the intermediate filaments in one cell to those in a neighbor

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13
Q

Where are gap junctions found?

A

Close to the base of epithelial cells

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14
Q

What are the features of gap junctions?

A
  • Important in smooth muscle contraction
  • Only spermatozoa, erythrocytes and other motile cells don’t have gap junctions
  • Consists of cylinders of proteins arranged in hexagonal pattern that open and close
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15
Q

What is the role of gap junctions?

A
  • Quickly communicate changes in intercellular molecular composition
  • Allows free movement of small molecules from one cell to another
  • Allows wave of electrical impulse - important in smooth muscle contraction
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16
Q

What are cell adhesion molecules?

A

Trans membrane proteins that bind to each other and to extra cellular materials

17
Q

Where are hemi-desmosomes found?

A

Only found on basal surface of epithelial cells

18
Q

What are the features of hemi-desmosomes?

A
  • Resemble half of a desmosome
  • Rather than attaching one cell to another, it attaches a cell to extracellular filaments in basement membrane
  • Intracellular intermediate filaments of cytokeratin attached today laminin through integrins
19
Q

What is the role of hemi-desmosomes?

A

Anchors intermediate filaments in a cell to the basal lamina

20
Q

Where are focal adhesions found?

A

Basal lamina

21
Q

What are the features of focal adhesions?

A
  • Uses intracellular actin filaments (instead of cytokeratin in hema-desmosomes)
  • Uses integrins (like hemidesmosomes)
  • Binds to fibronectin
  • When bound to fibronectin, conformational change results in binding to collagen fibers
22
Q

What is the role of focal adhesions?

A

Similar to hemi desmosomes but anchor intermediate filaments in a cell to the basal lamina and stabilize its position

23
Q

What are the features of integrins?

A
  • Central to cohesive forces holding tissues together

- Always work as alpha-beta dimer

24
Q

What are the features of the mucosal membrane?

A
  • Lines all the moist hollow internal organs of the body
  • Continuous with the skin at various body openings
  • Most mucous membranes secrete mucus, a thick protective fluid
25
Q

What is the function of the mucosal membrane?

A
  • Stop pathogens and ‘dirt’ from entering the body
  • Prevent bodily tissues from becoming dehydrated
  • Lubricate the surface
26
Q

What are some examples of mucosal membranes?

A
  • GI tract
  • Urinary tract
  • Respiratory tract
27
Q

What is the structure of the GI tract?

A
  • Mucosa: epithelial cell lining + lamina propria (supporting loose connective tissue layer) + muscularis mucosae (thin discontinuous smooth muscle layer)
  • Submucosa: connective tissue layer containing arteries and veins
  • Muscularis externa: smooth muscle layer with muscle fibers going in 2 directions (inner circular + outer longitudinal)
  • Serosa: outermost layer of loose connective tissue
28
Q

What are the functions of the GI tract mucosa?

A
  • Absorb substances from the lumen
  • Prevent ingress of pathogens
  • Move contents and expel waste
29
Q

For the GI mucosa, how does the structure of its constituent tissues relate to its function?

A
  • Epithelial cell specializations help to absorb substances from the lumen and prevent ingress of pathogens
  • Lamina propria contains lymphatic tissue to help prevent ingress of pathogens
  • Muscularis mucosae folds mucosa to increase surface area, hence aiding to absorb substances from the lumen and prevents ingress of pathogens
  • Muscularis externa performs peristalsis to aid the moving of contents and expelling of waste
30
Q

What is the structure of the urinary tract?

A
  • Epithelium also known as urothelium
  • Muscularis mucosa
  • Lamina propria
  • Inner longitudinal muscle
  • Outer circular muscle
31
Q

What are the functions of the urinary tract mucosa?

A
  • Absorption of essential nutrients in the kidney
  • Prevention of pathogen entry (especially lower urinary tract)
  • Removal of waste products
32
Q

For the urinary mucosa, how does the structure of its constituent tissues relate to its function?

A
  • Epithelial cells produce mucus which protects the bladder from damage by acidic urine
  • Tight junctions in epithelial cells prevents leakage to inner cell layers
  • Mucus glands produce large amounts of sticky mucus and so prevent ingress of pathogens
33
Q

What is the structure of the trachea and primary bronchi?

A
  • Conducting portion: Nasal cavity to bronchioles
  • Mucosa
  • Very thin lamina propria
  • No longitudinal muscularis mucosa layer
  • Submucosa: connective tissue layer containing mainly collagen, elastin fibers and fibroblasts
  • C-shaped Hyaline cartilage: 2 layers (perichondrium which has fibroblasts that lay down collagen fibers and chrodrogenic layer from which cartilage is formed)
  • NO outer layer of smooth muscle
34
Q

What is the structure of the secondary and tertiary bronchi?

A
  • Epithelium
  • Smooth muscle
  • Submucosa
  • Crescent shaped cartilage
  • No outer layer of muscle

Similar to primary except the cartilage is not present as full circle of rings

36
Q

What is the function of the conducting portion of the respiratory tract?

A
  • Provide route for incoming and outgoing air
  • Remove debris and pathogens from incoming air
  • Warm and humidify incoming air
37
Q

What is the structure of the alveolus?

A
  • Specialized Epithelial cells
  • Basal lamina
  • Connective tissue ‘muscle’ layers
  • Small amounts of collagen at the junction
38
Q

What is the function of the conducting portion of the respiratory tract?

A

Ensure fast efficient transfer of oxygen and carbon dioxide between blood and air

39
Q

For the alveolus, how does the structure of its constituent tissues relate to its function?

A
  • Folds in basal lamina allow for expansion of air sacs when air is drawn into the lungs
  • Connective tissue ‘muscle’ layers created by collagen and elastin fibers which provides elastic recoil to return the sac to empty state on exhaling gases
40
Q

For the trachea and bronchi, how does the structure of its constituent tissues relate to its function?

A

Secretions from epithelium and Submucosa glands contain:

  • Mucins and water: make sticky mucus
  • Serum proteins: lubricates surfaces
  • Lysozyme: destroys bacteria
  • Anti-pro teases: inactivate bacterial enzymes

Mucociliary escalator in trachea
- Using a ‘cilia wave’, mucus move materials to the oral cavity where material can be swallowed

Body Logistics (21 decks)

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