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Body Logistics > L6) Epithelial tissue and cell surface specialisation > Flashcards

L6) Epithelial tissue and cell surface specialisation Flashcards

1
Q

Define Epithelia

A

Sheets of contiguous cells, of varied embryonic origin, that cover the external surface of the body and line internal surfaces, including the body’s vessels.

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2
Q

What are the embryological germ layers that epithelial tissues are derived from ?

A

Ectoderm ( e.g.- epidermis)
Endoderm ( e.g.- inner and outer lining of the GI tract)
Mesoderm ( e.g. - inner linings of body cavities)

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3
Q

What are the surfaces with epithelial linings ?

A

Exterior surface ( skin)
Interior spaces opening to exterior ( GI tract )
Interior spaces which do not open to the exterior ( pericardial sacs, pleural sacs …)

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4
Q

What are the different types of cell shape in epithelial tissue?

A

Simple
Columnar
Cuboidal

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5
Q

What are the different types of layers present in epithelial tissue ?

A

Simple
Stratified
Pseudostratified
Transitional

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6
Q

What is the basement membrane ?

A

Basal lamina + Reticular layer

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7
Q

What is the mesothelium ?

A

The lining epithelium of ‘closed’ cavities - peritoneal, pleural and pericardial cavities.

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8
Q

What is the endothelium ?

A

Specialised form of epithelium

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9
Q

What are the functions of simple squamous epithelium?

A

Lubrication - mesothelium
Gas exchange - ( Type 1 pneumocytes of pulmonary alveoli)
Water, nutrient & waste product exchange ( endothelial cells lining heart & capillaries)
Barrier ( Bowman’s capsule, skin )

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10
Q

Define simple cuboidal ?

A

A single layer of polygonal cells, whose height & width are approximately equal

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11
Q

What are the functions of simple cuboidal epithelium ?

A

Absorption & conduit - exocrine glands
Absorption & secretion - kidney tubules
Barrier/covering - ovary
Hormone synthesis, storage & mobilisation - thyroid

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12
Q

What types of cells bound thyroid gland follicles?

A

Simple cuboidal epithelium

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13
Q

What happens in the thyroid ?

A

Epithelial cells synthesise thyroglobulin and store in the centre of the follicle ( colloid)
Only organ that stores its product outside of the cells.
Reprocess thyroglobulin to produce thyroxine & release that into the blood ( hormone )

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14
Q

What is simple columnar ?

A

A single layer of cells, whose heights are significantly greater than widths.

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15
Q

Name some locations that include simple columnar epithelium?

A

Stomach lining & gastric glands
small intestine & colon
Gallbladder

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16
Q

What are the functions of simple columnar epithelium?

A

Absorption ( small intestine, colon & gall bladder )
Secretion ( stomach lining & gastric glands, small intestine & colon)
Lubrication ( small intestine & colon)

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17
Q

Define pseudostratified epithelia

A

Tissues in which all cells make contact with the basement membrane, but not all of the cells reach the epithelial cell surface
Results in nuclei lying at different levels giving the impressions of multiple cell layers.

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18
Q

Name some locations that include pseudostratified epithelium?

A

Lining of nasal cavity, trachea, & bronchi

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19
Q

What are the functions of pseudostratified epithelium?

A

Secretion and conduit
Mucus secretion
Particle trapping and removal

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20
Q

What are the features of Goblet cells?

A

Lack of cilia on the apical surface - instead have microvilli
Release of mucins through exocytosis
Water release increased by release of ions

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21
Q

How does a mutation in CFTR gene lead to characteristics of cystic fibrosis?

A

Deficiency in chloride ion release - very sticky & immovable mucous

(chloride ions take with water them = mucus slippery / thin)

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22
Q

How does CF affect the tissues that have mucins and cilia in airways?

A

clogging & infection of bronchial passage with thick sticky mucus obstructs breathing, progressively
damages lungs – major cause of mortality in CF patients

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23
Q

How does CF affect the tissues that have mucins and cilia in the liver ?

A

The small bile duct becomes blocked, disrupts digestion in 5% of CF patients

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24
Q

How does CF affect the tissues that have mucins and cilia in the pancreas ?

A

Zymogen secretions not released in 85% of patients

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25
Q

How does CF affect the tissues that have mucins and cilia in the small intestine ?

A

Thick, non-motile stools in 10% of CF neonates - requires surgery

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26
Q

How does CF affect the tissues that have mucins and cilia in the Reproductive tracts ?

A

Absence of fine ducts such as vas deferens renders 95% of CF males infertile.
Occasionally, a thick mucous plug in cervix prevent semen transit and results in female infertility

27
Q

How does CF affect the tissues that have mucins and cilia in the skin ?

A

Malfunctioning of sweat glands results in very salty sweat and crystals on the surface of the skin

28
Q

Define stratified squamous epithelia ?

A

Contains multiple layers of cells, the outermost of which are thin squamous epitelial cells

29
Q

Name some locations that include stratified squamous non-keratinised epithelium?

A

Oral cavity
Oesophagus
Vagina
Part of anal canal
Surface of cornea
Inner surface of eyelid
( found in areas that are moist)

30
Q

What are the functions of stratified squamous non-keratinised epithelium?

A

Protection against abrasion (all sites)
Reduces water loss but remains moist (all sites)

31
Q

Define stratified squamous keratinised epithelium

A

Stratified squamous keratinised epithelium contains multiple layers of cells, the outermost of which are squamous cells that have lost their nuclei and cornified (i.e. become ‘squames’ of keratin).

32
Q

What is the stratum corneum ( Horny layer) ?

A

The outermost dead cells of the epithelium

33
Q

What are the functions of stratum corneum layer?

A

Greatly reduces water loss and ingress
prevents ingress of toxins
Protects against abrasion
Reduces microbial colonisation

34
Q

What is the primary site of stratified squamous keratinised epithelium ?

A

The epidermis of the skin - contains no blood vessels = avascular

35
Q

What are the examples of the locations that include stratified squamous keratinised epithelium ?

A

Surface of the skin
Limited distribution in oral cavity

36
Q

What are the functions of the stratified squamous keratinised epithelium ?

A

Protection against abrasion and physical trauma
Prevention of water loss
Prevention of microbial ingress
Shielding against UV light damage

37
Q

Define transitional epithelium ( urothelium )

A

Surface cells vary in shape from columnar/ cuboidal to flattened.

38
Q

What is the location of transitional epithelium
( urothelium ) ?

A

Urinary tract : from renal calyces -> ureters -> bladder Proximal urethra

39
Q

What are the functions of transitional epithelium
( urothelium ) ?

A

Distensibility
Protection of underlying tissue from toxic chemicals

40
Q

Define Serous membranes ?

A

Thin, two-part membranes which line certain closed body cavities (spaces which do not open to the exterior) and envelop the viscera.

41
Q

What are the 2 parts of the serous membrane ?

A

Visceral (outer) - closest to organs in cavity
Parietal (inner) - lines outer edge of cavity

42
Q

What do the serous membranes line ?

A

The peritoneum - which envelops many abdominal organs.
The pleural sacs - which envelop the lungs.
The pericardial sac - which envelops the heart.

43
Q

What is a function of a serous membrane ?

A

The serous membranes (or serosae) exude a lubricating fluid that promotes relatively friction-free movement of the structures they surround.

44
Q

What does the serous membrane consist of ?

A

Simple squamous epithelium (mesothelium) that exudes the watery lubricating fluid
Thin layer of connective tissue that attaches the epithelium to adjacent tissues
Carries blood and lymphatic vessels and nerves

45
Q

How are keratin specialised ?

A

Prevents water loss & protects against abrasion

46
Q

How are cilia specialised ?

A

Controls micro-movement of luminal contents

47
Q

How are goblet cells specialised ?

A

Mucus secretion, moistens and lubricates

48
Q

How are Microvilli specialised ?

A

Increases surface area for absorption & secretion

49
Q

What is the structure of Club cells ( clara )?

A

On the airway side of the terminal bronchioles
Have club like apical surfaces
No cilia
No basal bodies

50
Q

What are the functions of the club cells ?

A

To protect the bronchiolar epithelium - secretion of uteroglobin & solution similar in composition to pulmonary surfactant.
Detoxification of harmful substances inhaled into the lungs
Acts as stem cells - multiplying & differentiating into ciliated cells to regenerate the bronchiolar epithelium.

51
Q

Where are microfold cells found ?

A

Only in the small intestine and very close to lymphatic nodules.

52
Q

What are the functions of the microfold cells ?

A
  1. Trap pathogens and other molecules
  2. Present to underlying dendritic cells that
    process material
  3. Present to lymphocytes and macrophages that
    reside in a basal ‘pocket’ that is not linked to the basement membrane to raise an immune response or digestions, respectively
53
Q

What do M cells look like ?

A

Have a folded extension that looks like a mushroom cap that samples the lumen by endocytosis

54
Q

What do M cells represent ?

A

A weak point in the intestinal epithelium as many pathogens exploit them as a portal of entry

55
Q

What is the function of stereocilia in the inner ear ?

A

Mechanosensing organelles of hair cells, which respond to fluid motion for hearing & balance.

56
Q

What is the function of stereocilia in the epididymis & vas deferens ?

A

Facilitate absorption of the residual sperm body after spermentaion has completed.

57
Q

What do stereocilia contain ?

A

Actin & myosin filaments

58
Q

How does smoking damage the lungs ?

A

Early stage :
1. Normal mucus layer thickens
2. Cilia die off
3. Ciliagenesis – 2 to 4 days

Chronic stage :
1. Goblet cells and basal cells proliferate
2. Club cells (metaplasia) or die
3. Carcinogens induce mutations and malignancy
4. Pneumocytes in the alveoli die - Remaining type II cells proliferate to make both type I and II pneumocytes / Fibroblasts lay down scar tissue

59
Q

What are the cell renewal rates ?

A

Trachea - 1 to 2 months
Alveoli - 8 days
Goblet cells - 10 days
Club cells - never (once they die or undergo morphogenesis)

60
Q

How is Acute bronchitis a respiratory condition related to smoking ?

A

cough & mucus production, breathlessness < 3 months
Reduced lung function & breathlessness due to inflammation, swelling & narrowing of the lung airways & excess mucus in the lung passages
Later stage - Increased risk of serious respiratory diseases

61
Q

How is Chronic bronchitis a respiratory condition related to smoking ?

A

Chronic inflammation of the bronchi that produces a cough & mucus production that has at least 2 episodes of cough lasting 3 months or more during a 2 year period (smoker’s cough)
Reduced lung function & breathlessness due to inflammation, swelling & narrowing of the lung airways & excess mucus in the lung passages
Start of or irreparable damage to the bronchioles & alveoli

62
Q

How is Emphysema a respiratory condition related to smoking ?

A

Shortness of breath due to permanent widening of the airspaces distal to the terminal bronchiole without fibrosis (i.e. destruction of the air sacs)
Damage to air sac, loss of elastic recoil and permanent changes to the size of the alveoli (fuse and enlarge)

63
Q

How is COPD a respiratory condition related to smoking?

A

Chronic obstructive pulmonary disease – umbrella condition that includes both emphysema and chronic bronchitis

64
Q

How is Asthma a respiratory condition related to smoking ?

A

Wheeze, shortness of breath, chest tightness & cough that may vary over time & in intensity, with a variable expiratory airflow limitation - often has a trigger (e.g. cold, exercise, allergens, stress, etc.)
Caused by bronchospasm (tightening of the smooth muscle layer in the bronchi and bronchioles), obstruction from mucus & narrowing of the
conducting airways

Body Logistics (15 decks)

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