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imed3004 > Lecture 1 - Skin > Flashcards

Lecture 1 - Skin Flashcards

1
Q

What are the 2 main layers of skin?

A

Epidermis

Dermis

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2
Q

How are the dermis and epidermis different to each other?

A

Epidermis is avascular containing mostly keratinocytes and forms appendages (such as hair, nails, glandular structures)

Dermis is a deeper connective tissue layer containing nerves and muscles and makes up most of the skin.

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3
Q

What is hairless thick skin also known as?

A

Glabrous skin

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4
Q

What is thin hairy skin also known as?

A

Hirsute skin

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5
Q

What is the dermis vascular supply like?

A

It is rich in vascular and nerve supply.

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6
Q

What are the important functions of skin?

A

Protection (+ self repair)

Sensation

Catalysis (vitD)

Thermoregulation

Attraction + repulsion

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7
Q

How does skin regenerate itself?

A

Skin has a high cell turnover of ~10 - 30 days (epidermus) due to presence of epidermal stem cells which proliferate and differentiate and slowly migrate and die. Other stem cells form appendages.

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8
Q

Why does burnt skin regenerate without hair often?

A

Due to presence of way more epidermal stem cells than hair follicle (or sebaceous gland) stem cells

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9
Q

What does skin regeneration depend on?

A

It is layer dependent. Epidermis is faster and easier than dermis.

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10
Q

How does epidermis regenerate?

A

Stratum basale epidermal stem cells proliferate, migrate and fill gaps left by the injury

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11
Q

How does the dermis regenerate?

A

More difficult, Bleeds, results in immune response, secretion of matrix takes place (collagen and elastin) to fill wound.

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12
Q

What are the stages of wound repair?

A

Inflammation (injury +48 hrs): Hypoxic, fibrin clot is formed, platelets + neutrophils, full of microbes

New tissue formation (2 - 10 days post injury): Scab formed, angiogenic, epithelial cells migrate in.

Remodelling (Can last >1 year): Disorganized collagen, distorted shape/density, absence of normal appendages.

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13
Q

How are burns classified?

A

By how deep tissue involved in burn is

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14
Q

What are the effects of first degree burns?

A

Involves only epidermis and is characterised by redness, slight edema, and pain, heals in days.

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15
Q

What are the effects of second degree burns?

A

May appear red, tan, or white; blistered and painful.

Takes weeks to several months to heal and may leave scars

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16
Q

What are the effects of third degree burns?

A

Full-thickness involves epidermis, all of the dermis, and some deeper tissues.

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17
Q

How is a third degree burn treated?

A

Skin grafts

Fluid replacement

Infection control

Supplemental nutrition

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18
Q

What are the important receptors required for light touch sensation?

A

Tactile (Meissner’s) corpuscle is a rapidly adapting mecahnosensor.

Tactile (Merkel’s) disks are slowly adapting mechanosensors that sense continuous light touch

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19
Q

What are the important receptors that are required for heavy touch sensation?

A

Lamellar (pacinian) corpuscle is a rapidly acting mechanosensor for heavy touch.

Bulbous (Ruffini’s) corpuscle is a slowly adapting mechanosensor for heavy touch sensation and stretch.

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20
Q

What sensory receptors detect pain, warm and cold feeling?

A

Free nerve endings which are slowly adapting and have variable gating.

21
Q

What are thermoreceptors also called?

A

Transient Receptor Potential (TRP) channels

22
Q

How do thermoreceptors detect temperature?

A

They temperature-sensitive ion (excitatory Na+/Ca2+) channels

23
Q

What are cold receptors also called? How do they detect cold?

A

TRPM8 channels. Their firing rate increases as temperature decreases and their temperature range spans about 10 - 35 degrees and they also react to menthol and eucalyptus oil.

24
Q

What are warm receptors called?

A

TRPV1/3, and TREK1 channels

25
Q

How do warm receptors detect warm temperatures?

A

Firing rate increases as temperature increases.

TRPV3 = 22 - 40

TRPV1 = 42+

26
Q

What other channels besides thermoreceptor channels are temperature dependent in skin?

A

K+ leak channels

Na/K-ATPase

27
Q

What important physiological process is catalysed by skin?

A

Vitamin D synthesis

28
Q

How is vitamin D synthesized?

A

7-dehydrocholesterol + UV light -> D3

Liver -> 25-hydroxy-D3

Kidneys -> 1,25-dihydroxy D3

29
Q

How does the skin regulate body temperature?

A

Evaporative cooling (sweat)

Convective cooling (skin blood flow)

30
Q

How is skin blood flow regulated?

A

Hypothalamus detects blood temperature and either activates or deactivates sweat glands and capillaries in skin as well as hair erection.

31
Q

How much heat is lost from sweating?

A

0.58kcal/g of water evaporated

32
Q

What division of the nervous system controls sweating?

A

Sympathetic nervous system

33
Q

What is insensible water loss?

A

Water loss that isn’t from sweat glands (~500ml/day)

34
Q

What is another name for sweat glands?

A

Sudoriferous glands

35
Q

What are the types of sweat glands?

A

Eccrine (produce sweat)

Apocrine (secrete onto hairs)

36
Q

How is sweating regulated?

A

They contain myoepithelial cells that contract upon nervous stimulation to force sweat into ducts.

Initially protein free filtrate is secreted

Ions are reabsorbed that are hypo-osmolar (~120 mOsm/L)

Reabsorption of Na+ and Cl- and are powered by Na+/K+-ATPase (powers everything important to know for exam!)

37
Q

What nerves control sweating?

A

Sudomotor nerves. they are sympathetic postganglionic cholinergic nerves.

38
Q

What receptors receive signal from postganglionic cholinergic sympathetic nerves that innervate sweat glands?

A

mAChRs (Muscarinic acetylcholine receptors)

39
Q

What is used to decrease sweating?

A

Cholinergic (muscarinic) antagonists will also act to decrease sweating

40
Q

What is the blood flow to the skin in cold?

A

Low (1ml/min)

41
Q

What is the blood flow to the skin in hot weather?

A

High (150ml/min)

42
Q

What supplies blood to skin?

A

2 Cutaneous plexuses connected by communicating vessels that form arteriovenous anastomoses (glomus bodies):

Superficial - rich capillary loop system in the superficial dermal papillae

Deep - venous plexus between dermis and fat

43
Q

What is another name for the arteriovenous anastomoses in the skin?

A

Glomus bodies

44
Q

How is skin perfusion often relative to its needs?

A

It is normally overperfused for its metabolic requirements.

45
Q

What innervation do skin blood vessels have?

A

Sympathetic innervation.

46
Q

how is skin blood flow regulated?

A

Both locally (by temperature and hormones) and systemically (via sympathetic nervous system)

47
Q

Is the skin’s blood flow metabolically regulated?

A

No

48
Q

If a person is both hot and excited how is the sympathetic nervous system used to vasoconstrict and vasodilate the skin?

A

The sympathetic response causes little change in blood flow to skin unless it stimulates sweating. When sweating we activate NANC nerves which trigger vasodilation.

Post-ganglionic sympathetic nerve fibers that release ACh vasodilate

Non-adrenergic non-cholinergic nerves (NANC) release bradykinin and NO to vasodilate.

2 types of sympathetic nerves innervate skin NA releasing nerves that are vasomotor and ACh releasing nerves that are vasodilator.

As a result: in the cold, sympathetic adrenergic is acting

In the heat sympathetic cholinergic as well as NANC (bradykinin and NO)

49
Q

How does blushing take place?

A

Facial capillaries vasodilate in response to fear. Face is packed with beta-adrenergic receptors which dilate blood vessels in response to sympathetic nervous system innervation.

*Propranolol blocks blushing

imed3004 (50 decks)

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