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Semester 1 Body Logistics > L3: Integrating cells into tissues and organs > Flashcards

L3: Integrating cells into tissues and organs Flashcards

1
Q

When do the cells first coalesce?

A

Coalesce→ stick together

Embryogenesis → formation of an embryo

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2
Q

What is the name given to the ball of cells that are stuck together?

A

Morula

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3
Q

What happens after the formation of a morula?

A

Formation of a blastocyst

Separation into inner cell mass: embryoblast and outer cell mass: trophoblast

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4
Q

What does the embryoblast become?

A

Splits into the:

  • Epiblast → all the cells of the body
  • Hypoblast → yolk sac
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5
Q

What does the epiblast differentiate into?

A

Epiblast 3 layers
→ endoderm (organs and structures that maintain contact with the outside world e.g. nervous system and epidermis)
→ mesoderm (supporting tissues e.g. muscle, cartilage, bone, vascular system (heart and vessels))
→ ectoderm (epithelial lining of the GI tract, respiratory tract, parenchyma of glands)

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6
Q

What holds cells together and gives tissues shape?

A

Cell-cell adhesion molecules→ between cells
Extracellular matrix proteins→ fibres outside cells, scaffolding for tissues, holds cells in place
Internal-external scaffolding→ internal scaffolding, holds shape of cell, focal adhesion plaques attach to the external scaffolding holding the cells in place
Close proximity→ pressure effects, internal cells held in place by external cells pushing in

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7
Q

What is the main difference between connective tissue and epithelial tissue?

A

Organisation of tissues
Connective tissue→ lots of fibres/scaffolding, few cells
Epithelial tissue→ lots of cells, few fibres/scaffolding

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8
Q

Describe the structure of connective tissue?

A

ECM plentiful
Cells sparsely distributed
Matrix rather than cells bear mechanical stress→ lots of collagen
Direct attachments between cells is rare

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9
Q

Describe the structure of epithelial tissue?

A

Cells are tightly bound together→ epithelia or epithelium
No ECM between cells→ thin layer below→ basal lamina
Proteins between cells attach together→ bear strain
Cytoskeleton → Intracellular actin filaments and microtubules → maintain cell shape and keep together
Junction between cells and between cells-basal lmina

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10
Q

Where does connective tissue come from?

A

Mesoderm

Mesenchymal stem cells

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11
Q

What are mesenchymal stem cells?

A

Have the ability to differentiate into many different cells
Divides into differentiated cell and progenitor cell (pericyte)
e.g. bone, cartilage, tendons, ligaments, muscles, bone marrow, adipose, connective etc…

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12
Q

What is the structure of connective tissue?

A

3 components:

  • Cells → fibroblasts mainly
  • Fibres → collagen, elastin, reticular fibres
  • Ground substance → GAGs
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13
Q

What is the function of connective tissue?

A 
TIPSSS
T- Transport (blood and interstitium)
I- Insulation (adipose)
P- Protection (bones protecting organs)
S- Storage (bone marrow and fat)
S- Support and binding (skin)
S- Separation (fascia, tendons, cartilage)
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14
Q

Where does epithelial tissue come from?

A

All 3 germ layers
Ectoderm → epidermis, glands
Mesoderm → peritoneal cavities
Endoderm → lining of GIT, respiratory etc…
Lines all the cavities and free surfaces of the body

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15
Q

What is the main function of epithelial tissue?

A

Internal and external covering
Specialised junctions help them make/form tissue barriers → inhibit the movement of water, solute and cells from one compartment to another
Rest on bed of connective tissue→ basement membrane → attaches it to many different tissues

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16
Q

Define tissue?

A

Group of similar cells all working together to perform a particular function

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17
Q

Define organ?

A

Made up of two or more tissues with similar functions

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18
Q

How do epithelial cell adhere to each other?

A

Lateral cell surface

  • Tight junctions
  • Adherens junctions
  • Desmosome (adheson plaques)
  • Gap junctions
  • Cell adhesion molecules (CAMs)
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19
Q

How do epithelial cells adhere to the basement membrane?

A

Basal cell surface

  • Hemi-desmosome
  • Focal adhesion
  • Integrins
  • Proteoglycans
  • Cell adhesion molecules (CAMs)
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20
Q

What are tight junctions?

A

Apical part of lateral surface
Long cell to cell fusion point
Prevent movement
Paracellular transport → allows some small molecule to pass

21
Q

What are adhesion junctions?

A

1/3 way down from apical surface
Found in pairs
Intracellular actin filaments
Linked to E-cadherin proteins→ cross the intracellular space
Forms a belt of adhesion
Tissue stabilising factor and additional transport barrier (BBB)
Epithelial and endothelial cells only

22
Q

What are desmosome? (NOT ESSENTIAL)

A

Strongest of all cell-cell adhesions
Half way down
Random distribution
Tissues that experience intense mechanical stress
Cytokeratin fibres inside cells link to E-cadherin
Provide mechanical strength and prevent tissue destruction

23
Q

What are gap junctions?

A

Close to basal surface of epithelial cells
Role→ quickly communicate changes in intercellular molecular composition e.g. electrical changes in the heart
Free movement of small molecules from one cell to another
Made of cylinders of proteins (connexins) arranged in hexagonal pattern that open and close (ATP)
Connexins can switch e.g. myometrium preparation for birth switch from connexin 45 to 34
Only erythrocytes, spermatozoa ad motile cells do no have gap junctions

24
Q

What are hemi-desmosomes? (NOT ESSENTIAL)

A

Found on basal surface
Attaches cells to ECM
Intracellular filament of cytokeratin attach to laminin through integrins
Anchor epithelial cells in place

25
Q

What are focal adhesions? (NOT ESSENTIAL)

A

Basal surface
Intracellular actin filaments
Uses integrins
Binds to fibronectin → conformational change results in binding to collagen fibres

26
Q

What are integrins? (NOT ESSENTIAL)

A

Always works as an alpha beta dimer
Weak binders of ECM as dimer pair
Phosphorylation by focal adhesion kinase produced heterotetramer that has greater binding capacity

27
Q

What do all of the adhesion junctions require to work?

A

Calcium ions

28
Q

What are the four tissues of the body?

A

Epithelial
Connective
Muscle
Nerve

29
Q

What structure contains all four tissues?

A

The mucosal membrane

30
Q

What is the function of the mucosal membrane?

A

Lines all moist hollow internal organs
Continuous with skin at body openings
Secretes mucus
Stop pathogens and dirt entering the body
Prevent dehydration
Lubricate the surface to aid movement of contents
Absorption of substances

31
Q

What is mucus?

A 
Thick protective fluid 
Contains: 
- mucins (proteins), 
- electrolytes, 
- antiseptic enzymes (lysozyme) and 
- immunoglobulins
32
Q

Where is the mucosal membrane found?

A

GI tract
Urinary tract
Respiratory tract

33
Q

What are the layers of the GI tract wall?

A 
Mucosa lining the lumen 
Muscularis mucosae
Submucosa
Musclaris externa 
The serosa
34
Q

What is the function of each layer?

A

Mucosa→ secrete mucus that lubricates and protects the GI tract
Muscularis mucosae→ thin discontinous layer of smooth muscle
Submucosa→ connective tissue layer that contains arteries and veins
Muscularis externa→ smooth muscle layer, fibres orientated in two directions for peristalisis
- Inner - circular
- Outer - longitudinal
Serosa→ connective tissue layer contianing collagen and elastin fibres with some smaller arteries and veins

35
Q

What is the structure and function of the oesophagus?

A
  • Mucosa→ epithelium, lamina propria, muscularis mucosae
  • Submucosa → CT containing mucus secreting glands
  • Muscularis externa→ inner and outer
36
Q

What additional feature is found in the mucosa in the stomach, small intestine and large intestines?

A

Villi and micro villi
Increase the surface area for absorption
Peristalsis also aid absorption

37
Q

What special feature of the mucosa help prevent pathogen ingress?

A 
Epithelial specialisations (villi) help aid movement
Perisatlisis pushes contents along 
Lamina propria contains lymphatic tissue
38
Q

How is the urinary tract stuctured?

A

Lined with flattened (squamous) epithelium directly adjacent to endothelial cells→ absorption happens more easily
Collecting ducts
→ cuboidal cells - reabsorption
Proximal tubule
→ ciliated epithelial cells - increase SA and help move fluid along

39
Q

What is the structure of the bladder? Why is it structured this way?

A

Transitional epithelium (multiple layered)
Allows cells to flatten out
Produces mucin
→ protection from toxic urine,
→ allows urine to slide out,
→ stops pathogens getting in from the urethra
Thin lamina propria
Massive muscle → detrusor muscle (stretch detected→ message to brain→ go to loo!!!)

40
Q

What is the structure of the urethra?

A

Similar to bladder - epithelial cells change from transitional to squamous - keratinised at outlet
Sticky mucus produced→ prevent ingress of pathogens

41
Q

Summary of the urinary tract mucosa?

A

Similar to GI

  1. Absorption of essential nutrient to the GI tract
  2. Prevention of pathogens entry
  3. Removal of waste products
42
Q

What is the respiratory tract?

A

Gaseous exchange and transport

Conducting portion: nasal cavity to bronchioles and respiratory portion: respiratory bronchioles to alveoli

43
Q

What is the structure of the trachea and primary bronchus?

A

Mucosa→ epithelium several layers deep covered in cilia
Submucosa→ CT contains mainly collagen and elastin fibres and many fibroblasts, contain seromucous glands (watery mucus that thickens during infection)
C shaped hyaline cartilage→ two layers
1. perichondium - fibroblast lay down collagen
2. chrodrogenic layer- cartilage is formed

44
Q

What layer is no found in the trachea and primary bonchus?

A

Outer smooth muscle layer

45
Q

What secretion happen in the trachea and bronchus?

A

Mucins and water- sticky mucus
Serum proteins- lubricates the surface
Lysozymes- destroy bacteria
Anti-proteases- inactivate bacterial enzymes

46
Q

What is a special feature of the trachea?

A

Contains mucocillary escalator
Cilia wave
Backwards slow, forward fast propelling any bacteria towards the mouth where it can be swallowed

47
Q

What is the structure of the secondary and tertiary bronchi?

A

Chondrocytes it the cartilage holds the trachea in place
Same structure as before
Smooth muscle begins here as the cartilage gets less

48
Q

What is the structure of the alveolus?

A

Epithelial cells are very flat
Fused to basal lamina adjacent to endothelial cells
→ short diffusion distance
No muscle or CT
Folds in basal lamina allow for expansion of air sacs when the air is drawn into the lungs
Collagen fibres provide rigidity at junctions
Elastic fibres return sac to empty exhalation state

Semester 1 Body Logistics (19 decks)

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