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pharm phys intro > epithelia + integumentary system > Flashcards

epithelia + integumentary system Flashcards

1
Q

describe the basic structure of epithelial cells

A

outer layer of epithelial cells, basement membrane beneath, connective tissue beneath that

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2
Q

explain the terms simple, stratified and pseudostratified

A

simple = single layer

stratified = many layers

pseudostratified = one layer appearing as more than one due to different sizes of cells

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3
Q

simple squamous epithelia - describe structure, function and location

A

appears like thin, flattened scales, mostly for rapid passage of molecules.
found in alveoli and serosa (peritoneal membrane on the outer intestine)

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4
Q

simple cuboidal epithelia - structure, function, location?

A

structure as named - single layer, cuboidal so not as flat as squamous or as long as columnar.

function is typically something to do with absorption.

found in kidney tubules and ducts of glands.

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5
Q

simple columnar epithelia - structure, function and location?

A

quite long with nuclei near the basal end. can have microvilli/cilia

function is typically involving absorption and/or secretion - majority of the GI tract.

also used to move things along in respiratory system and fallopian tubes (egg)

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6
Q

stratified squamous epithelia - structure, function and location?

A

this is the most common one, the cells at the top (apical layer) appear ‘squamous’ - flat - and the rest appear more columnar/cuboidal.

appears in upper layers of skin (keratinised) and in the oesophagus (non-keratinised)

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7
Q

stratified cuboidal epithelia - structure, function, location?

A

mostly in glands, looks like neat layers of cells

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8
Q

stratified columnar epithelia -

A

very rare, layers of columnar cells.

resist tearing by allowing tissue to stretch.

found in conjunctiva (eye), pharynx, anus, male urethra, embryo

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9
Q

pseudostratified columnar epithelia - structure (and how to identify it easily), function, location?

A

appears layered, just different sizes - so all cells reach the basement membrane, but not all reach the apical surface - so can be easily spotted by nuclei at lots of different levels.

can be ciliated, and if so are often interspersed with goblet cells

found in the upper respiratory tract

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10
Q

transitional epithelia - how structure relates to function, and location?

A

found in the bladder, helping it stretch i.e. it facilitates distension. the cells appear flat when distended and rounder when relaxed

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11
Q

glands that used ducts to secrete are?

A

exocrine, typically multicellular and often different cell types

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12
Q

glands that don’t use ducts are?

A

endocrine, usually a single cell type and can be a single cell

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13
Q

mucus vs serous glands?

A

secrete mucus vs proteins

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14
Q

what do unicellular goblet cells do?
what do multicellular acinar do?

A

goblet - interspersed in epithelia (pseudostratified columnar), secrete mucus
acinar - found in the salivary glands and pancreas, secrete enzymes

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15
Q

what are the 4 main properties of all epithelial cells?

A

POLARITY
connected to basement membrane
cell-cell junctions
cell replacement (different rates of turnover but need to be replaced due to hostility of external environment)

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16
Q

the basement membrane - describe its structure and function regarding epithelial cells

A

has the basal lamina (made up of the lucida and the densa), then the reticular lamina beneath it.

provides mechanical strength to resist tears, gives access to nutrients from blood including O2 as epithelia are avascular

reticular lamina tethers the basement membrane to the underlying connective tissue

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17
Q

describe all cell-cell junctions and cell-matrix attachments

A

gap junctions - allow small molecules (water and ions) to move between cells.
adherens junctions hold cells together, some junctions use desmosomes

cell-matrix attachments use hemidesmosomes

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18
Q

why are myosin filaments important in embryos?

A

allow invagination to occur via contraction to then form certain structures

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19
Q

what are tight junctions and what do they control?

A

between cells, near the apical surface, seal the gap, controls paracellular movement - the movement of substances between cells

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20
Q

what are claudins?

A

claudins are proteins important in tight ju8nctions, there are 24 genes for claudins, because they must meet the needs of different areas of the body - due to different ions needed/different permeability

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21
Q

changes in claudins can result in what change?

A

epithelial cells can convert to mesenchyme cells (the underlying cells) and vice versa

22
Q

what are the cell replacement times for the intestine, interfollicular epidermis and the lung epithelium?

A

5 days
4 weeks
6 months
stem cells provide the ability to replace cells

23
Q

the integumentary system has three layers. what are they?

A

epidermis, dermis, hypodermis

24
Q

what is the hypodermis?
what does it do?

A

the bottom most layer, it is subcutaneous fat and adipose tissue (connects skin to the muscle and bones), yellow due to carotene.

it physically protects, cushions what’s underneath
insulates
stores energy

25
Q

describe the structure of the dermis (general + papillary)

A

thicker than the epidermis, it has two layers, both connective tissue. The laminin and fibronectin etc… for this is made by fibroblasts.

papillary layer (upper) -
thin connective tissue, allows immune cells to move through (and up)
rich layer of blood and lymphatic vessels.
nerve endings reach right up to the edge of this layer, correspond with Merkle cells in the stratum Basale of the epidermis.

26
Q

describe the reticular layer of the dermis

A

thicker connective tissue in order to anchor things
these things include sweat and oil glands (with ducts going to the outer skin), hair follicles

27
Q

describe the dermal-epidermal boundary

A

wavy structure with finger like projections, cause of fingerprints

has dermal papillae (these projections of the dermis further up into the epidermis, can help nerve endings reach closer to the surface in more sensitive areas)

epidermal ridges

boundary made clear by basement membrane

28
Q

describe the general structure of the epidermis - what cells are present?

A

made up of five layers of keratinised (lots of keratin) squamous epithelia

stem cells in the basal layer produce the keratinocytes that move upwards as the dead upper layers are lost

dendritic cells (Langerhans) in spinosum
melanocytes in the basal layer
merkel (tactile) cells

29
Q

non glabrous (skin with hair) has only 4 layers. which one is missing?

A

stratum lucidum

30
Q

describe the stratum Basale and the function of its cells

A

bottom most layer, attached by hemidesmosomes to the basement membrane .

the only mitotically active layer that replenishes the keratinocytes.

has melanocytes that produce red and brown melanin (pheomelanin and eumelanin) which causes skin pigmentation and protect against UV
Merkel cells - tactile cells - communicate with dermal nerve endings

31
Q

what is the purpose of melanin?

A

protects DNA from UV radiation
one way this works is vesicles containing melanin -0 melanosomes - are phagocytosed by keratinocytes and surround DNA to protect it

32
Q

describe the structure of the stratum spinosum and the function of its cells

A

biggest layer, produces a lot of keratin that causes the cells to flatten (hence spines)

keratinocytes tightly linked by desmosomes, these tight junctions ensure water retention

Langerhans cells involved in immune response

cells cannot divide

33
Q

describe the structure of the stratum granulosum

A

3-5 flat layers of keratinocytes

has keratohyalin granules that make proteins involved in cornifying keratin

produces glycolipid filled vesicles called lamellar vesicles, to form a waterproof barrier

bound by tight junctions

34
Q

describe the structure of Stratum Lucidum

A

only in thick glabrous skin

translucent layer, with densely packed dead keratinocytes, no organelles

granules of eleidin (product of the keratohyalin granules) to do with water retention

35
Q

describe the structure of the stratum corneum

A

15-30 most outer layers of cornified dead keratinocytes

the keratinocytes are known as squames and can be lost by desquamation (has two parts, stratum compactum and the loosest stratum disjunctum)

36
Q

what is the cornified envelope and how does it contribute to the function of the stratum corneum?

A

a layer beneath the plasma membrane of the cells that provides a waterproof barrier resistant to abrasion and penetration

keratins are enclosed in an insoluble mix of proteins, cross links are formed between keratin by transglutaminases, so its quite a solid layer

surrounded by a lipid envelope

37
Q

tell me about nails

A

derivatives of the stratum corneum

nail matrix adds 1mm/week

window into health:
flat = iron deficiency = clubbed = hypoxemia

38
Q

what is hair made of, and what are the different kinds of hair?

A

keratinised dead cells renewed from the hair follicle (the root and bulb)

lanugo = foetus hair, fine and unpigmented
vellus = fine and unpigmented (peach fuzz)
terminal/androgenic = longer and coarser and pigmented

39
Q

describe the structure of a hair follicle

A

in dermal layer and is made up of the root which stems rom the bulb
the bulb grows around a dermal papilla (blood supply), and is surrounded by the mitotically active hair matrix which has three sections (medulla, cortex, cuticle)

40
Q

name all the glands and what they do in the skin

A

merocrine = sweat (associated with myoepithelial cells of the SNS)

apocrine = sweat, associated with scents, stress, sex/pheromones

sebaceous = lubricates, produces sebum

ceruminous = ear wax

mammary = milk

41
Q

how does the skin function as a biochemical and physical barrier?

A

physical = cross linked keratin layers

biochemical = slightly acidic (pH 4 - 6) to deter growth of microorganisms
sebum has bactericidal agents to inhibit bacterial growth
C6H (cis-6-hexadeconic acid) prevents antibiotic resistance induction

42
Q

how does the skin act as an immunological barrier?

A

stratum spinosum - Langerhans cells
they have a level of tolerance, decide if an immune system response is necessary
one mechanism is increased proliferation of the keratinocytes to replace lost/damaged cells - if this happens unnecessarily it can lead to psoriasis

43
Q

list the immune cells present in the dermal layer

A

macrophages
mast cells
neutrophils
eosinophils
monocytes
Langerhans cells
B and T lymphocytes

44
Q

what are AVAs?

A

arteriovenous anastomoses
they connect arterioles and venules, bypassing capillary beds (so aren’t involved in nutrients)
they play an important role in thermoregulation as they can vasoconstrict/dilate, they have a constant low level tonic activity at rest

45
Q

what is one way not involving nerves that ensures extremities don’t get too hot?

A

counter current heat exchange between arteries and venules

46
Q

finish the sentence - the skin is perfused with blood past…

A

its need for nutrients

47
Q

how does the body respond to high core temperatures?

A

sympathetic innervation decreased, so AVAs dilate/stop constricting - more blood flows to the AVAs and reaches skins surface to increase heat dissipation, lowering core temperature.
NT used is thought to be ACh

Sweating

48
Q

how does the body respond to lower core temperatures?

A

increased sympathetic innervation causes vasoconstriction, less blood flows through AVAs to the apical skin, reducing heat dissipation
NT used is noradrenalin (working on a 1 and 2 receptors of cutaneous arterioles) and shivering helps

49
Q

how does the body detect temperature?

A

peripheral receptors in skin detect external temperature
receptors in the preoptic anterior hypothalamus detects core temperature

50
Q

how do glabrous and non glabrous skin differ in thermoregulation?

A

non glabrous - has the paracrine signal bradykinin a vasodilator. has both sympathetic nerves, vasoconstrictors and vasodilators.
glabrous - has lots more AVAs and pretty much only vasoconstrictor nerves as staying warm is the main issue for extremities like ears, nose, hands etc…

51
Q

is blood flow effective in thermoregulation?

A

it is very effective -
at rest blood flow to the skin is around 250ml/min (dissipates 80kcal/hr)
in severe hyperthermia we can increase this to 6-8l/min to increase heat loss
however it only requires an 8ml increase/100ml/min over the entire body to double our heat loss

pharm phys intro (9 decks)

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