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Body logistics > Epithelial tissue and cell surface specialisations > Flashcards

Epithelial tissue and cell surface specialisations Flashcards

1
Q

definition of 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

embryonic origins of epithelial cells

A

epithelial tissues are derived from all 3 embryological germ layers
ectoderm - e.g. epidermis
endoderm - e.g. inner and outer lining of GI tract
mesoderm - e.g. inner linings of body cavities

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3
Q

mesothelium

A

epithelium lining closed cavities such as peritoneal, pleural and pericardial cavities

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4
Q

endothelium

A

epithelium lining chambers of the heart and blood + lymph vessels

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5
Q

functions of epithelia

A
  • protection
  • secretion
  • lubrication
  • absorption
  • reproduction
  • sensation
  • excretion
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6
Q

how are epithelia classified

A
  • shape of individual cells (squamous, cuboidal, columnar)
  • arrangement of cells into layers (simple, stratified/compound)
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7
Q

locations of simple squamous epithelium

A
  • heart
  • endothelium of blood and lymph vessels
  • mesothelium of pleural and peritoneal cavities
  • glomerulus
  • Bowman’s capsule
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8
Q

functions of simple squamous epithelium

A
  • lubrication - pericardium, pleural membranes, peritoneum/viscera (mesothelium)
  • gas exchange - type 1 pneumocytes of pulmonary alveoli
  • water, nutrient and waste product exchange - endothelial cells lining heart + capillaries
  • barrier - bowman’s capsule, skin, oesophagus, conjunctivae of eye, brain
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9
Q

what is simple cuboidal epithelium

A

single layer of polygonal cells with equal height and width

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10
Q

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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11
Q

locations of simple cuboidal epithelium

A
  • exocrine gland ducts
  • proximal kidney tubules
  • parenchyma of glands
  • thyroid gland follicles
  • pancreatic duct
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12
Q

thyroid gland follicles

A
  • simple cuboidal epithelium synthesise thyroglobulin and store in centre of follicle in a colloid
  • follicle reprocesses thyroglobulin to thyroxine and releases into blood
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13
Q

what is simple columnar epithelium

A

single layer of cells whose heights are greater than their widths - nuclei close to basement membrane

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14
Q

locations of simple columnar epithelium

A
  • stomach lining + gastric glands
  • small intestine + colon (crypts of Lieberkuhn)
  • gallbladder
  • jejunum
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15
Q

functions of simple columnar epithelium

A
  • absorption - small intestine, colon, gallbladder
  • secretion - stomach lining + gastric glands, small intestine, colon
  • lubrication - small intestine, colon
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16
Q

what are pseudostratified epithelia

A

all cells make contact with basement membrane but not all cells reach the epithelial cell surface so nuclei lie at different levels giving the impresssion of multiple cell layers

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17
Q

locations of pseudostratified epithelium

A
  • lining of nasal cavity
  • trachea
  • bronchi
  • upper respiratory tract
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18
Q

functions of pseudostratified epithelium

A
  • secretion + conduit - respiratory tract, ductus deferens
  • mucus secretion - respiratory tract
  • particle trapping and removal - respiratory tract
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19
Q

goblet cells

A
  • microvilli on apical surface instead of cilia
  • release mucins by exocytosis
  • water release increased by release of ions
  • found in epithelium of upper respiratory tract + intestinal villus
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20
Q

cystic fibrosis mechanism

A
  • mutation in CFTR gene (usually puts Cl- on surface of cell so water released so runny mucus)
  • deficiency of chloride ion release
  • sticky and immovable mucus
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21
Q

what tissues does cystic fibrosis affect (any with mucins and cilia)

A

airways
- clogging and infection of bronchial passage with thick sticky mucus obstructs breathing and progressively damages lungs
- major cause of mortality in CF

liver
- small bile duct blocked
- disrupts digestion in 5%

pancreas
- zymogen secretion not released in 85%

small intestine
- thick non-motile stools in 10% of neonates
- requires surgery - remove large part of SI

reproductive tracts
- absence of fine ducts such as vas deferens - 95% males infertile
- thick mucus plug in cervix prevents semen transit so female infertile

skin
- malfunctioning of sweat glands causes salty sweat
- crystals on surface of skin

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22
Q

what is stratified squamous epithelia

A

multiple layers of cells of which the outermost are thin squamous (layers held together by desmosomes)

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23
Q

functions of stratified squamous epithelium

A
  • protection against abrasion
  • reduces water loss but remains moist
  • prevention of microbial ingress
  • shielding against UV light damage
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24
Q

locations of stratified squamous keratinised epithelium

A
  • surface of skin
  • oral cavity (limited)
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25
Q

locations of stratified squamous non- keratinised epithelium

A
  • oral cavity
  • oesophagus
  • vagina
  • anal canal
  • surface of cornea
  • inner surface of eyelid
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26
Q

what is stratified squamous keratinised epithelium

A

contains multiple layers of cells, the outermost of which are squamous cells that have lost their nuclei and cornified (become squames)

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27
Q

what is stratified squamous non-keratinised epithelium

A

contains multiple layers of cells, the outermost of which are squamous cells that retain their nuclei - found in areas that are moist and subject to abrasion

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28
Q

locations of stratified cuboidal epithelium

A
  • glandular ducts
29
Q

functions of stratified cuboidal epithelium

A
  • absorption of materials
  • secretion of products - water and salts
30
Q

locations of stratified columnar epithelium

A
  • conjunctiva of eye
  • larger secretory ducts
  • parts of male urethra
31
Q

functions of stratified columnar epithelium

A
  • secrete tears and fluids
  • absorb excess materials produced elsewhere e.g. spermatazoa
  • protection e.g. prevention of tissues from effects of urine
32
Q

what is transitional epithelium (urothelium)

A

surface cells vary in shape from columnar/cuboidal to flattened

33
Q

location of transitional epithelium (urothelium)

A

urinary tract

34
Q

functions of transitional epithelium (urothelium)

A
  • distensibility
  • protection of underlying tissues from toxic chemicals e.g. urea
35
Q

structure of the basement membrane

A

basal lamina
reticular layer

36
Q

function of basement membrane

A

filter of proteins

37
Q

position of basement membrane

A

attached to basal surface of epithelial cells, separating them from connective tissue

38
Q

regeneration of epithelial cells

A
  • skin wound healing - replacing srface skin cells
  • cells lining GI tract
  • cells lining respiratry tract
  • renewal of uterine lining following menstruation
39
Q

what is metaplasia

A

some epithelia have capacity to change from one type of epithelium to another
- e.g. in heavy smokers the pseudostratified columnar epithelium of respiratpory tract can become stratified squamous

40
Q

what are carcinomas

A

tumours of epithelial origin

41
Q

what are adenomas

A

benign tumours of glandular epithelial cells

42
Q

what are adenocarcinomas

A

malignant tumours of glandular epithelial cells

43
Q

what is neoplasia

A

changes in epithelia giving rise to a tumour (neoplasm)

44
Q

cell renewal rate of trachea

A

1-2 months

45
Q

cell renewal rate of alveoli

A

8 days

46
Q

cell renewal rate of goblet cells

A

10 days

47
Q

cell renewal rate of club cells

A

never once they die or undergo morphogenesis

48
Q

how does smoking damage the lungs

A

early stage
- normal mucus layer thickens
- cilia dies
- ciliagenesis - 2-4 days

chronic stage
- goblet cells and basal cells proliferate and make thick mucus
- club cells die
- carcinogens induce mutations and malignancy
- pneumocytes in alveoli die (type II proliferates to make type I and II)
- fibroblasts lay down scar tissue

49
Q

7 cell surface specialisation

A
  • keratin
  • cilia
  • goblet cells
  • microvilli
  • club cells
  • microfold cells
  • stereocilia
50
Q

function of keratin

A

prevent water loss and protect against abrasion

51
Q

function of cilia

A

controls micro-movement of luminal contents

52
Q

function of goblet cells

A

mucus secretions, moistens and lubricates

53
Q

what are club (clara cells)

A
  • cells with club like apical surface
  • no cilia and no basal bodies
  • on the airway side of terminal bronchioles
54
Q

functions of club (clara) cells

A

protect bronchiolar epithelium
- secrete variety of products including uteroglobin and similar solution to pulmonary surfactant

detoxification of harmful substances inhaled into lungs
- cytochrome P450 enzymes in SER

stem cell
- multiply and differentiate into ciliated cells to regenerate bronchiolar epithelium

55
Q

what are microfold cells

A
  • found in small intestine and close to lymphatic nodules
  • folded extension that looks like a mushroom cap that samples lumen by endocytosis
  • represent a weak point in intestinal epithelium as many pathogens exploit them as portal of entry e.g. salmonella
56
Q

function of microfold cells

A

rapid sampling of gut microflora

57
Q

how do microfold cells work

A
  • trap pathogens and other molecules
  • present to underlying dendritic cells that process material
  • presented to lymphocytes and macrophages residing in basal pocket not linked to basement membrane
  • raises an immune response or digestions
58
Q

functions of stereocilia

A
  • inner ear - mechanosensing organelles of hair cells which respond to fluid motion for hearing and balance
  • epididymis + vas deferens - absorption of residual sperm body after spermiation has completed
59
Q

what are stereocilia

A
  • projections longer than microvilli and cilia
  • contain actin and myosin filaments
60
Q

what are the parts of a serous membrane

A
  • visceral - closest to organs in cavity
  • parietal - lines outer edge of cavity
61
Q

difference between mucous membrane and serous membrane

A

mucous
- line certain internal tubes which open to the exterior
- e.g. GI, respiratory and urinary tracts

serous
- thin, two-part membranes that line certain closed body cavities and envelop the viscera
- e.g. peritoneum, pleural sacs, pericardial sac
- exude a lubricating fluid for friction-free movement

62
Q

what does a mucous membrane consist of

A
  • epithelium lining the lumen of tube
  • adjacent layer of connective tissue - lamina propria
  • layer of smooth muscle cells - muscularis mucosae
  • blood + lympathic vessels and nerves in connective tissue
63
Q

what does a serous membrane consist of

A
  • simple squamous epithelium (mesothelium) that exudes watery lubricating fluid
  • thin layer of connective tissue attaching epithelium to adjacent tissues
  • blood + lympathic vessels and nerves in connective tissue
64
Q

acute bronchitis

A
  • inflammation of bronchi
  • cough and mucus production, breathlessness <3 months
  • due to inflammation, swelling and narrowing of lung airways
  • excess mucus in lung passages
  • later stage = increased risk of serious respiratory disease
65
Q

chronic bronchitis

A
  • chronic inflammation of bronchi
  • cough and mucus production with 2 episodes of cough >3 months over 2 years
  • due to inflammation, swelling and narrowing of lung airways
  • excess mucus in lung passages
  • start of irreparable damage to bronchioles and alveoli
66
Q

emphysema

A
  • shortness of breath due to permanent widening of airspaces distal to terminal bronchiole without fibrosis
  • damage to air sac, loss of elastic recoil and permanent changes to size of alveoli
67
Q

COPD (chronic obstructive pulmonary disorder)

A

umbrella condition that includes both emphysema and chronic bronchitis

68
Q

asthma

A
  • wheeze, shortness of breath, chest tightness and cough that may vary in time and intensity
  • variable expiratory airflow limitation
  • often has trigger e.g. cold, exercise, allergens, stress
  • caused by bronchospasm (tightening of smooth muscle layer in bronchi and bronchiole), obstruction from mucus and narrowing of conducting airways

Body logistics (20 decks)

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