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Physiology And Pharmacology > Skin > Flashcards

Skin Flashcards

1
Q

Key ideas about the skin

A
  • largest organ (12-15%
  • barrier to external environment
  • insight to internal health, even in adulthood
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2
Q

what are the layers of the skin

A

Epidermis (uppermost layer)
Dermis

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3
Q

Is hypodermis a layer of the skin? why?

A

No as it is a layer of tissue that binds skin to underlying tissue

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4
Q

Is the dermis thicker or the epidermis?

A

Dermis

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5
Q

what are fibroblasts?

A

Cells that produce the extracellular matrix proteins in the dermis
(main ECM protein is collagen)

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6
Q

What other ECM proteins are produced?

A

Laminin and fibronectin

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7
Q

What do these ECM proteins do?

A

they form elastic and reticular fibres

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8
Q

what are the 2 zones within in the dermis?

A

papillary layer- thin loose connective tissue, movement of leukocytes, mast and macrophage cells
reticular layer- thick dense irregular connective tissue layer, less cells + adipocyte clusters

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9
Q

what are adipocyte clusters?

A

They are fat cells that cluster together in the reticular layer
*These can cause stretching of skin in individuals with lots of fat

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10
Q

what accessory organs pass through the dermis?

A

nails, hair, oil + sweat glands

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11
Q

The skin has a rich layer of blood + lymphatic vessels as well as a specialised vessel know as?

A

arteriovenous anastomoses

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12
Q

Why are arteriovenous anastomoses vessels important?

A

they are important for thermoregulation

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13
Q

what causes sensitivity within the dermis layer?

A

nerve endings

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14
Q

what is the structure of the epidermis made of?

A

keratinised stratified squamous epithelium

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15
Q

what are the 5 layers of the epidermis?

A
  1. Stratum Basale
  2. Stratum spinosum
  3. Stratum granulosum
  4. Stratum corneum
    5- stratum lucidum (TRANSLUCENT LAYER ONLY IN THICK SKIN THAT PROTECTS FROM MECHANICAL STRESS)
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16
Q

What are the 2 types of skin and how are they different?

A

Thick- 5 layers, smooth + no hair (palms, feet and fingertips)
Thin- 4 layers

17
Q

Does the epidermis have any blood vessels?

A

No

18
Q

What are the properties of Stratum Basale?

A

They have:
- keratinocytes- stem cells constantly dividing to replenish the skin (mitotically active)
- Melanocytes- give skin colour
- Tactile/Merkel cells- connected to sensory nerves

19
Q

Other than melanin, what else gives skin pigmentation?

A

Blood perfusion
Carotene pigments

20
Q

what are the 2 types of melanin?

A

pheomelanin- red/ yellow pigment
eumelanin- brown/ black pigment

21
Q

What are Melanocytes and how do they work?

A

They are cells that release Melanin

Melanin is a UV absorbent, antioxidant –> protects skin form UV damage

Melanosomes produced by melanocytes are phagocytosed by Keratinocytes –> these then surround the nucleus on the sun side for protection

22
Q

What are the types of wavy boundry in the skin?

A
  • Dermal papillae - raised areas eg fingerprint (the ones going up)
  • Epidermal (rete) ridges (the ones going down)
  • These prevent the sliding of layers - providing high degree of mechanical stress
23
Q

What are the properties of the Stratum Spinosum?

A

-Several keratinocyte layers
-Usually thickest layer (except in thick skin = stratum corneum)
-Deepest cells are mitotic - and they are pushed upwards –> cease to divide (stops dividing)
-As they go on this journey, they produce Keratin filaments –> flatten more in upper layers

-KERATINOCYTES ARE STRONGLY LINKED BY DESMOSOMES
-TIGHT JUNCTION ENSURE WATER RETENTION OF SKIN
-DENDRITIC CELLS PRESENT

24
Q

What are the properties of Stratum Granulosum?

A

-3-5 layers o flat keratinocytes (more present in thick skin than thin skin)
-Post-mitotic, tight junction claudins - important barrier function
-contain dark-staining granules - bind to cytoskeleton
cells undergo apoptosis - programmed cell death
-produce glycolipid-filled vesicles - these spread over the surface of this layer and form a waterproof barrier between stratum spinosum

25
Q

What are the properties of Stratum Corneum?

A

-Most superficial (on the surface) - 15-30 layers of dead cornified calls flattened on the surface
-lots of keratins
-enclosed within insoluble amalgam of cross-linked proteins
-surrounded by extracellular lipid envelope (fused lamellar bodies)
-especially resistant to abrasion, penetration and water loss

26
Q

What are nails and how are they formed?

A

composed of dead scaly cells densely packed with hard keratin fibers
New cells added by mitosis in the nail matrix

Appearance can indicate underlying conditions - iron deficiency –> flat or concave - long term hypoxemia –> clubbed

27
Q

What are the three types of barriers in skin protection?

A
  1. Physical barrier
  2. Biochemical barrier
  3. Immunological barrier
28
Q

What are the five types of glands found in the skin?

A
  1. Eccrine/merocrine sweat glands
  2. Apocrine sweat glands
  3. Holocrine sebaceous glands
  4. Ceruminous glands
  5. Mammary glands
29
Q

How do eccrine sweat glands function and what is their

A

Produce watery perspiration

Controlled by sympathetic nervous system via myoepithelial cells
Primary role in temperature regulation
Release secretions directly to skin surface

30
Q

What are the characteristics of apocrine sweat glands?

A

Cells “pinch off” into ducts

Release secretions into hair follicles
Function as scent glands
Respond to stress and sexual stimulation
Located in armpits and genital regions

31
Q

How do holocrine sebaceous glands work?

A

Entire cell disintegrates to release product

Produce oily sebum that lubricates skin and hair
Primarily located on face, chest, and back
Differentiated epithelial cells accumulate lipids before rupturing

32
Q

What immune cells are present in the dermis?

A

Macrophages and monocytes

Mast cells
Eosinophils
Neutrophils
B and T lymphocytes

33
Q

What is the role of dermal immune cells?

A

Tissue remodelling

Repair processes
Tissue proliferation
Release of cytokines and chemokines
Maintain balance in immune response

34
Q

How does counter current heat exchange work in the skin?

A

Occurs between arterial and venous blood flow in extremities

Located in dermis
Minimizes heat loss
Important for maintaining core temperature

35
Q

What is special about blood flow in apical skin?

A

Contains high density of arteriovenous anastomoses (AVA)

Rich sympathetic innervation using norepinephrine
Core temperature increase → decreased sympathetic tone → increased blood flow
Core temperature decrease → increased sympathetic tone → decreased blood flow

36
Q

How does non-apical skin regulate temperature?

A

Uses sympathetic nervous system acetylcholine release

Activates eccrine sweat glands
Releases vasoactive molecules
These molecules relax vascular smooth muscle cells
Results in increased perfusion and heat loss

37
Q

Which areas of the body are most important for heat exchange?

A

Areas with high surface area to volume ratio:

Ears
Finger pads
Toes

38
Q

What characterizes the skin’s microflora?

A

Contains over 1,000 species

Includes harmless commensals
Contains opportunistic pathogens (e.g., S. aureus)
Plays role in skin defence

Physiology And Pharmacology (17 decks)

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