Skin Flashcards

1
Q

skin general main role:

A

tough, tensile strength, covers the whole body, protection from friction/impact, UV rays

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2
Q

skin functions:

A

external layer relatively impermeable to water, thermoregulation, immune function

  • makes vit D3, secretes oil, sweat
  • receptors: touch, heat, pressure and pain
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3
Q

main layers of skin and composition:

A

epidermis and dermis, btw is basement membrane

  • epidermis: keratinised stratified squamous epithelium
  • dermis: deep connective tissue

hypodermis/ subcutaneous layer: areolar and adipose tissue

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4
Q

layers of epidermis and cell types found:

A

stratum: corneum, lucidum, granulosum, spinosum, basale (from superficial-deep)

mainly keratinocytes, also melanocytes, intraepidermal macrophages (Langerhans cells) and tactile (Merkel’s cells)

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5
Q

stratum basale: cell type/ composition/ features/ function

A

LIVING: simple basal columnar or cuboidal cells -> dermal/epidermal junction

  • frequent mitotic cells, constantly renewing keratinocytes
  • every 15-30 days
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6
Q

stratum spinosum: cell type/ composition/ features/ function

A

LIVING: prickle cell/ spiny layer (8-10 layers)

  • cuboidal/ polyhedral
  • or slightly flattened keratinocytes w/ nucleus and cytoplasm filled with bundles of keratin (strength, resistance)
  • thick in areas of friction and pressure
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7
Q

stratum granulosum: cell type/ composition/ features/ function

A

DEAD: 3-5 layers of flatterned polygonal keratinocytes, cytoplasm filled with coarse basophilic granules

  • cells undergo apoptosis
  • also has small lamellar granules, fuse with cell membrane-> discharging contents into intercellular spaces= lipid-rich sheets (seals skin, barrier)
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8
Q

stratum lucidem: cell type/ composition/ features/ function

A

DEAD: 3-5 layers of translucent flattened cells, no evident nuclei/ organelles
- densely packed keratin filaments, thick plasma membrane

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9
Q

stratum corneum: cell type/ composition/ features/ function

A

DEAD: cornified (keratinised)

  • varies thickness (15-20, up to 50 layers)
  • no nucleus, packed with keratin
  • layers continuously shed

keratinisation: enzymes remove cell organelles, leave mainly keratin = closely packed plates, tough, waterproof layer
- callouses from mechanical pressure

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10
Q

melanocytes: location/ features/ function

A

in basal layer, abundant cytoplasm, large irregular shape with projections extend in btw. keratinocytes
- produce melanin, skin pigment, blocks UV radiation from deeper skin layers

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11
Q

cytoplasm of epidermis:

A

contains ovoid granules, which produce melanin -> passes along cytoplasmic processes to basal and prickle cell layer keratinocytes

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12
Q

what gives skin colour?

A

melanin, carotene (temporary yellow), haemoglobin (pink/ red)

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13
Q

albinism:

A

lack of melanin in skin, eyes and hair, susceptible to damage from UV

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14
Q

Vitiligo:

A

autoimmune disease, degradation of melanin pigment, due to somatic cells not recognising

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15
Q

intraepidermal macrophages:

A

Langerhans cells

  • important part of immune system, present in small no. on healthy skin
  • ovoid nucleus, cytoplasm and cytoplasmic processes extending btw. keratinocytes
  • mainly in spinosum
  • in hypersensitivity reactions
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16
Q

tactile cells:

A

Merkel’s cells

  • found in basal layer
  • resemble melanocytes, form synapses with peripheral nerve endings = touch receptors
17
Q

Dermis: function/ composition/ features/ layers

A

supporting ct. of epidermis, binds to subcutaneous tissue

  • has epidermal appendages: hair follicles, hair, sweat glands, sebaceous glands, nails, mammary glands
  • vascularised: has blood vessels, nerves, and nerve endings

upper papillary layer, lower reticular layer

18
Q

upper papillary layer: cell type/ composition/ features/ function

A

areolar ct.

  • paler than reticular dermis, less collagen/ elastin, more matrix
  • random collagen/ elastin
  • fine blood vessels and nerve endings
19
Q

lower reticular layer: cell type/ composition/ features/ function

A

most of dermis, DICT, broad bands of dense collagem, thick fibres of elastin, usually parallel to surface
- blood vessels, lymph, nerves

20
Q

collagen and elastic fibres general function:

A

collagen: strength, no elastic
elastic: connect dermis -> basal lamina, stretch and return to og size

21
Q

stretch marks: and eg

A

striae, from extensive stretching of skin fast, and collagen fibres break

  • pregnancy, growth
  • surgery can cut btw tension lines, minimise scarring
22
Q

dermal/ epidermal junction:

A

irregular, dermal papillae interdigitate (like interconnect) with epidermal ridges

  • creates fine ridges on hands and feet (thick skin)
  • dermatoglyphics (finger print)
23
Q

hair layers/ structure

A

derived from epithelium, shaft (above skin) + root (within skin)

  • medulla (pigment granules, air cells)
  • cortex (heavily keratinised, pigment granules)
  • cuticle (cuboidal/ columnar, heavily keratinised)
  • follicles surround root, deep into dermis/ hypodermis
  • internal/ external root sheaths: ct. sheath
24
Q

hair bulb, arrector pili:

A

dilation at base, specialised area of dermis -> germinative cells produce hair shaft = keratinised dermal papilla

  • arrector pili: narrow band of smooth muscle, contracts- hair more erect
25
Q

sebaceous glands: cell type/ composition/ features/ function

A
  • sebaceous glands connected to hair follicle
  • secretes sebum, coating hair and skin (waterproof, protects from drying out)
  • most on body surface, esp face, forehead and scalp
  • outgrowth of external root sheath (hair) in dermis
  • simple branched acinar
  • holocrine gland (whole cell ruptures), secretion = cell death
  • basal cells in periphery of gland proliferate (multiply) to replace lost cells
26
Q

sweat glands: cell type/ composition/ features/ function

A

sudiferous:

secrete: water, electrolytes
- temperature regulation
- merocrine (eccrine) (forming vesicles to move into cell) and apocrine (rupturing of vesicles to discharge from cell) NOT associated with hair follicles
- simple coiled tubular

27
Q

sweat glands: secretory and duct portions

A
  • secretory portion in dermis, sometimes hypodermis
  • secretory segment: cuboidal/ low columnar epithelium
  • duct segment: stratified cuboidal epithelium (2 layers) smaller/ darker than secretory cells
28
Q

sweat glands: apocrine

A

located in axilla, nipple region, anus, external genitalia

  • connected to hair follicles, secretes protein/ carb/ ammonia/ lipids
  • interacts with skin bacteria= body odour (only from puberty)
  • larger glands
  • coiled, tubular gland
  • secretory portion: dermis/ hypodermis, large lumen
  • duct: stratified cuboidal epithelium
29
Q

compare thin vs thick skin: distrubution

A

thin: all parts of body except palms, digits, soles
thick: palms, palmar surfaces, digits, soles

30
Q

compare thin vs thick skin: epidermal strata

A

thin: lucidum lacking, thin spinosum/ corneum
thick: thick lucidum, spinosum, corneum

31
Q

compare thin vs thick skin: epidermal ridges

A

thin: lacking due to undeveloped disorganised dermal papillae
thick: present as papillae in parallel rows

32
Q

compare thin vs thick skin: hair follicles/ arrector pili

A

thin: present
thick: absent

33
Q

compare thin vs thick skin: sebaceous glands

A

thin: present
thick: absent

34
Q

compare thin vs thick skin: sudoriferous glands

A

thin: fewer
thick: more numerous

35
Q

compare thin vs thick skin: sensory receptors

A

thin: sparser
thick: denser