Lecture 1 - Skin Flashcards Preview

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Flashcards in Lecture 1 - Skin Deck (49):
1

What are the 2 main layers of skin?

Epidermis

Dermis

2

How are the dermis and epidermis different to each other?

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.

3

What is hairless thick skin also known as?

Glabrous skin

4

What is thin hairy skin also known as?

Hirsute skin

5

What is the dermis vascular supply like?

It is rich in vascular and nerve supply.

6

What are the important functions of skin?

Protection (+ self repair)

Sensation

Catalysis (vitD)

Thermoregulation

Attraction + repulsion

7

How does skin regenerate itself?

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.

8

Why does burnt skin regenerate without hair often?

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

9

What does skin regeneration depend on?

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

10

How does epidermis regenerate?

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

11

How does the dermis regenerate?

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

12

What are the stages of wound repair?

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.

13

How are burns classified?

By how deep tissue involved in burn is

14

What are the effects of first degree burns?

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

15

What are the effects of second degree burns?

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

Takes weeks to several months to heal and may leave scars

16

What are the effects of third degree burns?

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

17

How is a third degree burn treated?

Skin grafts

Fluid replacement

Infection control

Supplemental nutrition

18

What are the important receptors required for light touch sensation?

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

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

19

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

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.

20

What sensory receptors detect pain, warm and cold feeling?

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

21

What are thermoreceptors also called?

Transient Receptor Potential (TRP) channels

22

How do thermoreceptors detect temperature?

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

23

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

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

What are warm receptors called?

TRPV1/3, and TREK1 channels

25

How do warm receptors detect warm temperatures?

Firing rate increases as temperature increases.

TRPV3 = 22 - 40

TRPV1 = 42+

26

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

K+ leak channels

Na/K-ATPase

27

What important physiological process is catalysed by skin?

Vitamin D synthesis

28

How is vitamin D synthesized?

7-dehydrocholesterol + UV light -> D3

Liver -> 25-hydroxy-D3

Kidneys -> 1,25-dihydroxy D3

29

How does the skin regulate body temperature?

Evaporative cooling (sweat)

Convective cooling (skin blood flow)

30

How is skin blood flow regulated?

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

31

How much heat is lost from sweating?

0.58kcal/g of water evaporated

32

What division of the nervous system controls sweating?

Sympathetic nervous system

33

What is insensible water loss?

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

34

What is another name for sweat glands?

Sudoriferous glands

35

What are the types of sweat glands?

Eccrine (produce sweat)

Apocrine (secrete onto hairs)

36

How is sweating regulated?

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

What nerves control sweating?

Sudomotor nerves. they are sympathetic postganglionic cholinergic nerves.

38

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

mAChRs (Muscarinic acetylcholine receptors)

39

What is used to decrease sweating?

Cholinergic (muscarinic) antagonists will also act to decrease sweating

40

What is the blood flow to the skin in cold?

Low (1ml/min)

41

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

High (150ml/min)

42

What supplies blood to skin?

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

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

Glomus bodies

44

How is skin perfusion often relative to its needs?

It is normally overperfused for its metabolic requirements.

45

What innervation do skin blood vessels have?

Sympathetic innervation.

46

how is skin blood flow regulated?

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

47

Is the skin's blood flow metabolically regulated?

No

48

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

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

How does blushing take place?

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