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BL - SEM1 > Session 3 - Epithelial cells, tissues, organs & systems > Flashcards

Session 3 - Epithelial cells, tissues, organs & systems Flashcards

1
Q

What are epithelia?

A

Sheets of contiguous cells that cover the external surface of the body & line internal surfaces including the body’s vessels

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2
Q

What is the embryonic origin of epithelial cells? (give examples)

A

Derived from all the embryological germ layers:
- ectoderm (eg epidermis)
- endoderm (eg inner & outer lining of gastrointestinal tract)
- mesoderm (eg inner linings of body cavities)

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3
Q

Why are dead cells able to be scrapped off the surface easily?

A

They are not held by desmosomes

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4
Q

Describe the structure of simple squamous epithelia. Which part of the body do they line and what are their functions?

A

One single layer of flattened cells

Line body cavities (mesothelium) => heart, blood vessels, pleural & peritoneal cavities.

Functions:
- Lubrication (pericardium, pleural membranes, peritoneum/viscera)
- Gas exchange
- Water, nutrient & waste exchange (eg endothelial cells lining heart & capillaries)
- Barrier ( skin, oesophagus, conjunctivae of eye, brain)

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5
Q

Describe the structure of simple cuboidal epithelia. Which part of the body do they line and what are their functions?

A

One single layer of polygonal cells whose height & width are approx equal
Line small ducts and tubules that may have excretory, secretory or absorptive functions eg kidney tubules, thyroid, exocrine gland
Functions:
- Absorption & secretion of materials into ducts/tubes
- Barrier (ovary)
- Hormone synthesis, storage & mobilisation

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6
Q

What is the basement membrane? What is it made up of?

A

A thin sheet-like layer of ECM
Made up of basal lamina + reticular layer

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7
Q

Where is the basement membrane found?

A

Located between most epithelium and deeper connective tissue

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8
Q

What are the functions of the basement membrane?

A

Acts as a filter for substances reaching epithelial tissue
Provides structural support for epithelial cells
Anchors the epithelial to connective tissue

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9
Q

What are serous membranes?

A

thin, two-part membranes which line most closed body cavities and envelop the viscera eg peritoneum (envelopes abdominal organs), pleural sacs (envelops lungs) & pericardial sac (envelops heart)

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10
Q

Why do serous membranes exude lubricating fluid?

A

for friction-free movement of structures that it surrounds

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11
Q

What do serous membranes consist of?

A
  • simple squamous epithelium (mesothelium) => exudes watery lubricating fluid
  • thin layer of connective tissue that attaches epithelium to adj tissues
  • carries blood, lymphatic vessels & nerves
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12
Q

What are mucous membranes?

A

Moist inner lining of internal tubes which open up to exterior eg GI tract, respiratory tract & urinary tract

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13
Q

Why are mucous membranes coated with mucous gland secretions?

A

protects membranes & keep them moist

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14
Q

What do mucous membranes consist of?

A
  • Epithelium lining the lumen of tube
  • Adj layer of connective tissue (lamina propria)
  • Third layer of smooth muscle cells (muscularis mucosae)
  • Carries blood, lymphatic vessels & nerves
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15
Q

Describe the structure of simple columnar epithelia. Which part of the body do they line and what are their functions?

A

One single layer of column-like cells which are taller than they are wide
- Line stomach, gastric glands, SI, colon & gall bladder (most organs of the digestive tract)
Functions:
- Absorption (SI, colon & gall bladder)
- Secretion (stomach lining, gastric glands, SI & colon)
- Lubrication (SI & colon)

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16
Q

Describe the structure of pseudostratified epithelia. Which part of the body do they line and what are their functions?

A

consists of column-like cells of varying heights where all cells are in contact with the basement membrane not but all in contact with apical surface, nucleus all at diff levels
- Line nasal cavity, trachea, bronchi
Function:
- secretion & conduit
- mucus secretion
- particle trapping & removal (respiratory tract)

17
Q

How does the composition of keratin render it the ability to be produce a waterproof surface?

A

tightly packed dead cells (keratinocytes) on the uppermost layer of the epidermis produces waterproof layer?

18
Q

What are the functions of keratin (2)?

A

Reduce water loss
Protects against abrasion

19
Q

Describe the structure of STRATIFIED SQUAMOUS KERATINISED EPITHELIUM. Which part of the body do they line and what are their functions?

A

Multiple layers of cells, outermost are squamous cells have lost their nuclei & cornified (squames of keratin)

  • Lines surface of the skin (epidermis)
  • Oral cavity (limited)

Functions:
- Protection against abrasion & physical trauma
- Preventing of water loss
- Preventing of microbial ingress
- Shielding against UV light damage

20
Q

How do the outermost dead cells of stratified squamous keratinised epithelium protect the rest of the tissue?

A
  • Reduces water loss & ingress
  • Prevents ingress of toxins
  • Protects against abrasion
  • Reduces microbial colonisation
21
Q

Describe the structure of the epidermis?

A

Made up of avascular EPIDERMIS & dense, irregular tissue consisting of collagen elastin bundles, DERMIS

22
Q

Describe the structure of transitional urinary epithelium (urothelium). Which part of the body do they line and what are their functions?

A

Surface cells round & pear-shaped => cuboidal when relaxed & squamous when stretched

  • Lines urothelium

Function: enable tissue to contract and expand eg allow the bladder to enlarge when the bladder is filled with urine.
- Protection of underlying tissue from toxic chemicals

23
Q

Why are there tight junctions between urothelial cells (transitional urinary epithelium)?

A

prevents urine from entering body which will kill nerves & vessels

24
Q

What are club cells? List their functions (3).

A

On the airway side of terminal bronchioles; club like apical surfaces; no cilia; no basal bodies

Functions:
- Protect bronchiolar epithelium => secretion of products eg uteroglobin & solution
- Detoxification of harmful substances inhaled in lungs
- Act as stem cells => multiplying & differentiation into diff ciliated cells to regenerated bronchiolar epithelium

25
Q

What are microfold cells? List their functions (2).

A

Specialised intestinal epithelial cells, found in small intestine & close to lymphatic nodules. Folded extension that looks like a mushroom cap.

Functions:
- Trap pathogens => present to dendritic cells & process material => present to lymphocytes & macrophages to raise immune response
- M cells important for generation of immune response

26
Q

What makes microfold cells special from the rest?

A

They are not attached to basement membrane when simple epithelium (only type of epithelial cell to do this)

27
Q

Why are microfold cells a weak point in intestinal epithelium?

A

pathogens exploit them as portal of entry eg salmonella uses M cells exclusively to enter body

28
Q

What are stereocilia. List its function.

A

Mechanosensing organelles of hair cells in inner ear which respond to fluid motion for hearing & balance

  • in auditory system coverts pressure waves into electrical signals
29
Q

How do microvilli increase surface area for absorption & secretion?

A

they are one cell thick

30
Q

What do cillia control?

A

micro-movement of luminal contents

31
Q

What is chronic bronchitis?

A

inflammation of brochi

32
Q

What is emphysema?

A

shortness of breath due to permanent widening of airspaces distal to the terminal bronchiole w/o fibrosis (destruction of air sacs)

33
Q

What is asthma?

A

wheeze, shortness of breath, chest tightness & cough caused by bronchospasm (tightening of smooth muscle layer in bronchi & bronchioles), obstruction from mucus and narrowing of conducting airways

34
Q

What is COPD

A

chronic obstructive pulmonary disease
umbrella term for both emphysema and chronic bronchitis

35
Q

What are the renewal rates for tracheal, alveoli, goblet & club cells?

A

Trachea = 1 to 2 months
Alveoli = 8 days
Goblet = 10 days
Clubs cells = never (die or become cancer)

36
Q

What occurs in chronic smoking?

A
  1. Goblet & basal cells proliferate = produce thick mucus to make sure carcinogens & carbon monoxide through tissues
  2. Club cells undergo metaplasia (turning into cancer) or die
  3. Carcinogens induce mutations in all cells in respiratory tract
  4. Pneumocytes in alveoli die => remaining type II cells proliferate to make type I and type II pneumocytes, fibroblasts lay down scar tissue
37
Q

Explain the cause of CF.

A

Mutation in CFTR gene affects ability for gene to release Cl- ions and water on the surface cell causing mucus to be sticky and immovable.

38
Q

What is the function fo the CFTR gene?

A

to release Cl- ions and water on surface of cell, causing mucus to thin and slide

39
Q

What occurs in early smoking?

A
  • Normal mucus layer thickens
  • Cilia die off
  • Ciliagenesis – 2 to 4 days

BL - SEM1 (7 decks)

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