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Medicine year 1 semester 2 > Case 8- skin > Flashcards

Case 8- skin Flashcards

1
Q

How to work out the surface area of the skin

A

Can be worked out using the rule of 9

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2
Q

Surface area of the anterior and posterior head and neck

A

9%

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3
Q

Surface area of the anterior and posterior arms, forearms and hands

A

18%

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4
Q

Surface area of the anterior and posterior trunk

A

36%

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5
Q

Surface area of the Perineum

A

1%

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6
Q

Surface area of the anterior and posterior thighs, legs and feet

A

36%

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7
Q

What are the cutaneous layers of the skin

A
  • Epidermis (most superficial)
  • Dermis- split into the papillary layer, which contains the dermal papillae these are projections of the dermis into the epidermis. Below that is the reticular layer.
  • Hypodermis/subcutaneous layer- this is not a layer of the skin but connects the skin to the underlying tissue.
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8
Q

Accessory structures of the skin

A

Nails, exocrine glands and hair. They start in the dermis but are ectodermally derived from the epidermis

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9
Q

The surface epithelium

A

Keratinized stratified squamous

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10
Q

The epidermis

A

Ectodermal in origin. Composed mostly of keratinocytes and is organised in four/five layers

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11
Q

Thin skin

A

Covers most of the body, the epidermis has 4 distinct layers of cells, no stratum lucidum. Has a thin epidermis, is Hirsute and contains hair

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12
Q

Thick skin

A

Covers your palms and soles of feet. The epidermis has five distinct layers including the stratum lucidum. Is Glabrous meaning it doesn’t have hair on it. Specialised for grip

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13
Q

Blood supply to the epidermis

A

The epidermis is avascular, the oxygen and nutrients diffuse from the dermis

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14
Q

Movement of cells through the epidermis

A

Cells move up through the layers from the stratum basale to the surface, differentiation and programmed cell death takes place as they move upwards. When it gets to the highest layer, the stratum corneum the cells will be dead Keratocytes. The skin is then shed from the surface. The skin is therefore being constantly renewed as it is being exposed to the external elements. This process takes between 15 to 30 days and occurs in waves.

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15
Q

Stratum Basale

A

Where skin cells are derived, continuously divides. A mitotically active component (single later of cells). Produces basal lamina that attaches to the dermis below. 5th layer

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16
Q

Stratum spinosum

A

Consists of several layers of keratinocytes. The cells are connected by desmosomes which give them a spiny appearance. Variable cell thickness, cells produce large amounts of cytoplasmic keratin. 4th layer

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17
Q

Stratum granulosum

A

The cells contain granules. They also produce lipids, they go into the intracellular space forming the waterproof properties of the skin. 2-5 cells thick. Most cell organelles are degraded through apoptosis but the cytoskeleton remains. Contains lots of keratohyalin granules which organise the cytoskeleton. 3rd layer

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18
Q

Stratum lucidum

A

A transparent band of flattened skin cells, found only in thick skin. 4-6 cells thick. Made of dead cell which are anucleate (no nucleus). Do not stain well. 2nd layer.

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19
Q

Stratum corneum

A

Variable cell thickness (5-100 cell layers). Squamous in appearace, flattened, thick plasma membrane, eventually it desquamates. The outermost layer, consists mostly of dead cells. Replaced every 2 weeks. 1st layer

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20
Q

Specialised cell type in the epidermis- Melanocyte

A

Produces pigment. Found in the basal layer, found in 1 per 4-10 basal cells. They contain cytoplasmic projections that transfer melanin granules into keratinocytes. Melanin production is stimulated by UV-B exposure and by ACTH. Melanin protects DNA from UV-B. All humans possess the same number of melanocytes, the levels of production and the type explains the difference in skin colour.

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21
Q

Specialised cell types on the epidermis- Langerhans cells

A

Dendrocytes/ dendritic cells, phagocytes that move to the lymph nodes when activated

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22
Q

Specialised cell type in the epidermis- Merkel cells

A

Within the basal layer, senses fine touch and pressure

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23
Q

Dermis layers

A

1) Papillary layer

2) Reticular layer

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24
Q

Papillary layer

A

Made of loose connective tissue (collagen). It projects into the stratum basale of the epidermis to form finger-like dermal papillae. Contains fibroblasts, adipocytes, blood vessels, phagocytes, lymphatic capillaries, nerve fibres and Meissner corpuscles (touch sensors).

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25
Q

Fibroblasts

A

They synthesise the extracellular matrix, which is predominantly made of collagen and elastin

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26
Q

Reticular layer

A

Underlying the papillary layer, it is much thicker and is composed of dense, irregular connective tissue (collagen and elastin). It is well vascularised and has a rich sensory and sympathetic nerve supply

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27
Q

Hypodermis

A

Consists of well vascularised, loose, areolar connective tissue and adipose tissue that provides insulation and cushioning. It connects the skin to the underlying fascia (fibrous tissue) of the bones and muscle

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28
Q

The arteries in the skin

A

The arteries of the skin are derived from the plexus in the subcutaneous connective tissue. Branches from this plexus form a sub papillary network in the dermis. The veins have a similar arrangement to the arteries and arteriovenous anastomoses are abundant.

29
Q

Function of skin- Protection

A

From the environment, chemical, mechanical, osmotic, thermal and UV damage.

30
Q

How the skin forms a physical barrier

A

Physical barrier separating the external environment from the skin. Keratinisation and shedding of the skin (exfoliation)) continually remakes the physical barrier and sheds off any unwanted chemicals and pathogens

31
Q

Structures in the skin which form the physical barrier

A

It contains Keratinocytes (make up the physical barrier and produce keratin that has waterproof properties), Melanocytes (UVB protection through melanin production), and Stratum granulosum (secretes lipids into the intracellular space). There are also sebaceous glands which secrete sebum onto the skin which lubricates and waterproofs the skin

32
Q

Function of skin- water barrier

A

The epidermis stops water from leaving or entering. This prevents dehydration

33
Q

Function of skin- thermoregulators

A

Within the dermis you have the sweat glands, hair and blood vessels. Evaporation of sweat cools down the body. Hairs can stand up straight and trap a layer of insulating air to try and keep us warm. In the Hypodermis you have adipose tissue and blood vessels. The adipose tissue acts an insulator. The surface area affects how much heat is lost.

34
Q

Roles of the skin- immunity

A

It is a physical barrier to stop pathogens getting into the underlying structures, this is the first line of defence in innate immunity. Langerhans cells (dendritic) present antigens and activate T lymphocytes for immune protection. Mast cells initiate the inflammatory process within the dermis. Keratinisation and shedding of skin helps remove pathogens.

35
Q

Roles of the skin- endocrine

A

Within the skin there is 7-Dehydrocholesterol, in the presence of UVB rays this gets generated into Previtamin D 3 and vitamin D 3. Vitamin D 3 will go to the liver to be metabolised and then into the kidneys. Vitamin D is needed in the absorption of calcium which helps in the maintenance and formation of bones and muscle.

36
Q

Different cells that detect touch sensitivity

A

Meissner’s corpuscles, Pacinian corpuscles, Merkel cells and Ruffini corpuscles

37
Q

Meissner’s corpuscles

A

In the dermis, detects delicate touch (high density of receptors in the fingertips / lips)

38
Q

Pacinian corpuscles

A

In the dermis, detects vibration and pressure (high density in thick skin)

39
Q

Merkel cells

A

In the stratum basale, detects light touch (high density in thick skin)

40
Q

Ruffini corpuscles

A

Detects skin stretch, helps finger coordination

41
Q

Dermal papillae

A

In the fingertips these form epidermal / papillary ridges and are the fingertips. They amplify vibrations, assist in grip and improve surface contact in wet conditions

42
Q

Roles of skin

A
  • Protection: from the environment, chemical, mechanical, osmotic, thermal and UV damage.
  • Water-barrier: by the epidermis, stops water from leaving or entering. Prevents de-hydration.
  • Thermo-regulator: through its surface area, blood supply to the skin and sweat glands.
  • Innate immune system- first line of defence
  • Sensory function: touch, heat, pain etc
  • Endocrine role- produces vitamin D
43
Q

Terminal hair

A

Pigmented, coarse, found on your head, armpit and groin

44
Q

Vellus hair

A

Fine, unpigmented, the hair found on the rest of your body

45
Q

Lanugo hair

A

Fine, pigmented. Found in infants and in anorexia

46
Q

Hair

A

A type of keratinised epithelial cell

47
Q

What is hair associated with?

A

The sebaceous glands (empty their secretion directly on the hair follicle), Apocrine sweat glands (empties into hair follicle) and Arrector pili muscles.

48
Q

Pilo-sebaceous unit

A

Formed from the hair follicle, the sebaceous gland, the Apocrine sweat gland and the Arrector pili muscle

49
Q

Where is the hair folicle

A

The epidermis descends to contain the hair follicle

50
Q

The hair bulb

A

Where the hair is produced. Contains the matrix and dermal papilla

51
Q

Hair- the matrix

A

Within the hair bulb. Produces keratinocytes which die, loosing their nuclei and projecting outwards forming hair. Within the matrix you have the melanocytes, giving the hair colour. The matrix is surrounded by the internal root sheath, it mostly covers the base of the hair follicle, once you get higher you loose it.

52
Q

Hair- the dermal papilla

A

Within the hair bulb. The dermal papilla supplies nutrients to the hair follicle, like oxygen and removes waste. Also contains loose connective tissue which anchors the hair follicle

53
Q

Hair structure

A

1) Once the hair emerges from the follicle it will be totally keratinised.
2) The medulla is the central core and consists of empty space, the type of hair will depend on the medulla and whether it is continuous or not.
3) The medulla is surrounded by the cortex which is a layer of compressed cuboidal cells which are pigmented.
4) The outer most layer is the cuticle which is made of flattened squamous cells.
5) Outside the cuticle is the internal root sheath.
6) Keratinisation begins just after the matrix, after the follicle it is completely keratinised. The external root sheath extends throughout the length of the hair follicle.

54
Q

Arrector pili muscle

A

When it contracts it causes hair to stand up. This squeezes the sebaceous gland. It is a type of smooth muscle and is activated by sympathetic innervation.

55
Q

Sebaceous glands

A

Produces sebum which is full of lipids and oils. It waterproofs and lubricates the skin. They are a Holocrine gland which releases its contents via apoptosis, the cells in the gland migrate from the edge of the hair follicle towards the lumen then they die and release their contents into the lumen of the canal.

56
Q

Sweat glands

A

There are Eccrine sweat glands and Apocrine sweat glands. The sweat glands are very coiled tubular structures. The glands originate in the epidermis but are found in the dermis

57
Q

Contents or Eccrine/ merocrine sweat

A

Clear secretion which is hypotonic to plasma, it contains mainly water, some NaCl and trace waste products.

58
Q

Eccrine sweat glands location

A

It empties onto the skin and presents over most of the body, contributes to insensible fluid loss

59
Q

How is eccrine sweat released

A

By vesicles which contain the sweat, its released into the lumen of the gland

60
Q

Eccrine sweat gland

A

A coiled structures made up of secretory cells which produce the fluid. Duct cells take the fluid to the surface so that they can be secreted. The secretory cells are cuboidal with a light staining. They are found in the lower reticular layer of the dermis. Less commonly they are found in the Hypodermis/subcutaneous layer. The duct cells stain darker and are a couple of layers thick.

61
Q

Formation of Eccrine sweat

A

Hypotonic as it contains fewer dissolved substances then the plasma. The sweat glands are innervated by the sympathetic post ganglionic fibre. Acetylcholine is released from the nerve which stimulates secretion of the initial liquid. The initial secretion is almost isotonic to the plasma and contain water and NaCl, this liquid moves into the lumen.

62
Q

How to make eccrine sweat hypotonic

A

The initial liquid is isotonic as it enters the lumen. The solution then flows along the sweat duct, you get reabsorption of NaCl out of the lumen as there is low permeability to water. The NaCl is removed through the ENaC channels and CFTR, so you get a hypotonic solution. There is secretion of NaCl and water by coil cells and reabsorption of NaCl alone by duct cells.

63
Q

How is sweating regulated?

A

Through Homeostasis. It is a thermoregulatory response which is controlled by thermoreceptors mostly in the skin, the autonomic NS activates eccrine sweat glands. During the thermoregulatory response humans can produce 1-2L of sweat per hour. There are also internal thermoreceptors in the brain and spinal cord. The thermoreceptors feed back to the hypothalamus in the brain. The initial response to being too hot is vasodilation. After this the autonomic NS activates the sweat glands.

64
Q

Normal sweat loss

A

600-1000ml/day

65
Q

Role of eccrine sweat

A

Temperature regulation

66
Q

Apocrine sweat

A

A viscous secretion, high in lipids and carbohydrates. It empties onto hair follicles or directly onto the skin. Responsible for body odour as bacteria feed of the secretion

67
Q

Where are Apocrine sweat glands found?

A

High density in armpits and pubic areas

68
Q

How is Apocrine sweat released?

A

Vesicles are pinched off the cell, releasing their secretory products

69
Q

Apocrine sweat glands

A

A coiled structure that is larger than the eccrine sweat gland. The secretory products are stored at the apex of the cell in secretory regions. They have a much larger lumen then Eccrine cell because the sweat is larger. There are also Myoepithelial cells which help squeeze the fluid through. You can also secretory granules which have the vesicles which contain the secretory products.

Medicine year 1 semester 2 (61 decks)

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