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Body Logistics > The Skin > Flashcards

The Skin Flashcards

1
Q

What is the location of the hypodermis?

A
  • the lowest layer of skin

- sometimes called the subcutaneous layer

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2
Q

How does the thickness of the hypodermis vary between males and females?

A

Men: thickest on the abdomen and shoulders

Women: thickest on the hips, thighs and buttocks

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3
Q

What is the hypodermis composed of?

A
  • mainly adipose tissue

- loose connective tissue (fibroblasts, macrophages, fibres)

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4
Q

What is the function of the hypodermis?

A
  • provides energy store for heat production
  • insulates underlying muscle
  • shock absorber
  • connects skin to underlying muscle and bone
  • makes hormone leptin (controls eating habits)
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5
Q

Where is the dermis located?

A

Between the hypodermis and the epidermis

  • also called the cornium
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6
Q

What are the 3 layers of the dermis called and what are their functions?

A
  • papillary layer (upper layer)
  • reticular layer (lower layer) contains many fibres
  • dermal papillae ( interdigitiating layer) holds the top layer layer together. Damage can cause the epidermis to fall off
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7
Q

What are the functions of the dermis?

A
  • thermoregulation - contains hairs and sweat glands
  • sensory structures for touch
  • gives skin structure and shape (by collagen and elastin fibres)
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8
Q

Where is the epidermis located what cells is it composed of?

A
  • outermost layer of skin composed of keratinocytes
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9
Q

What is the structure of the epidermis?

A
  • either 4 or 5 layers of skin depending on body location
  • held together by adherens junctions
  • no blood vessels
  • some nerve terminals
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10
Q

What is the function of the dermis?

A
  • prevents water loss
  • prevents entry of bacteria and parasites
  • special cells that present pathogens to immune cells
  • keratin synthesis
  • prevents tissue loss due to abrasion
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11
Q

What are the 5 layers of epidermis called? ( in order)

A
  1. Stratum Corneum
    - outer layer of dead keratinocytes
    - thick on palms and soles of feet
    - continuously shed
  2. Stratum Lucidium
    - ONLY on palms and soles of feet
    - very thin, transparent layer
  3. Stratum Granulosum
    - stratified squamous epithelium
    - lamellar granules that assemble & secrete keratin
    - tonofibrils. Bundles of keratin filaments and keratohyalin made forum lamellar bodies
  4. Stratum spinosium
    - cuboidal epithelium arranged in 3 layers held by desmosomes
    - produce lamellar bodies
    - 1st time Golgi apparatus is seen
  5. Stratum basale
    - tall columnar epithelial cells
    - constantly renewing keratinocytes by mitosis
    - daughter cells differentiate to tonofilaments as they move further from epidermis- dermis junction
    - home to melanocytes
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12
Q

What are melanocytes and where are they found?

A

Melanocytes produce melanin

They’re found in the stratum basale layer of the epidermis

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13
Q

Describe the role of keratin in the epidermis

A

In epidermis keratinocytes synthesise keratins which are fibrous proteins. They contribute to strength and protection of the epidermis

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14
Q

Describe what happens in psoriasis

A

Normal transit time of a keratinocytes from basal layer to st. corneum is 28-40 days.

In psoriasis the transit time is reduced to 2-3 days. Produces silvery scales on skin surface.

Psoriasis is a persistent condition

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15
Q

What is hyperkeratosis?

A

Too much keratin on the surface of the skin.

Can happen anywhere on body but especially hands and feet.

Caused by defective apoptosis mechanism- cells don’t die so desmosomes aren’t broken and cells are not got rid of in the normal way.

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16
Q

How do melanocytes release melanin?

A

Mature melanocytes transfer melanin to neighbouring keratinocytes by pigment donation where tops of the dendritic processes are phagocytosed by the keratinocyte

17
Q

What are langerhan cells?

A
  • highly specialised cell found in the epidermis

- present antigens to T cells to mediate immune reactions e.g contact dermatitis

18
Q

What are Merkel cells?

A

Mechanoreceptor cells in the epidermis associated with sensory nerve endings to senses touch

Account for 6-10% of cells in the epidermis

Dark skin has more Merkel cells (10%) than light skin (6%). Number lost with ageing

19
Q

Describe the location, structure and function of non hairy thick skin

A

Location: plantar surfaces of hands and feet and webs of fingers and toes

Structure: no hair, pilli muscles or sebaceous glands

  • thick stratum corneum
  • thinner dermis
  • increases density of mechanoreceptors

Function: prevents tissue loss from abrasion, increases friction between skin and surfaces to stop slips and increases sensation

20
Q

Compare thick (non hairy) and thin (hairy) skin

A

Thick:

  • no hair follicles
  • no sebaceous glands
  • no arrector pili muscles
  • pronounced ridges and furrows on surface (fingerprints)
  • regular shaped dermal papillae
  • stratum lucidum often seen

Thin:

  • hair follicles
  • sebaceous glands
  • arrector pili muscles
  • small ridges and furrows
  • irregular dermal papillae
  • stratum lucidum absent
21
Q

Identify and describe the 3 types of hair

A

Lanugo: covers developing foetus, only found in utero and lost in foetal development

Vellus: replaces lanugo. Short, thin, soft and light hair not connected to a sebaceous gland

Terminal: found on the scalp, eyebrows, nasal passage, external genital regions

  • long, wide, dark and coarse hair
  • produced by the actions of testosterone
22
Q

What are the 4 functions of hair?

A
  1. Thermoregulation
    - arrector pili contracts when stimulated by sympathetic fibre from the autonomic NS
  2. Sexual attraction
    - apocrine sweat glands secrete pheromones, trapped by hair which accentuates pungency
  3. Sensation
    - air movement, physical interactions and vibrations sensed and transmitted to CNS
  4. Protection
    - eyelashes and nasal hair protect from dust and pathogens
    - eyebrows reduced light and sweat entering the eyes
    - axilla(armpit) hair conducts sweat away from the body
23
Q

Describe the structure and function of arrector pilli muscle

A

Structure: smooth muscle fibres attached to papillary region of dermis (origin) and then hair bulb (insertion)

Function: sympathetic NS controls fight or flight response. Cold causes involuntary contraction and goosebumps

Also induces sebum release from sebaceous gland when muscle contracts- makes skin more slippery

24
Q

Identify the different mechanoreceptors in skin and what their function is

A

End bulbs- thermoreceptor in dermal layer

Free nerve ending- pain receptors (nociceptors) in epithelial layer

Tactile discs- vertical dimpling of skin that attaches basal layer to keratinocytes. Senses touch, pressure and texture

Messiner corpuscle- detects tapping and flicker movements

Pacinian corpuscle- detects vibration

Ruffini’s corpuscle- joint movement and tissue stretch

Root hair plexus- detects vibrations in the hair shaft

25
Q

Describe the structure of nails

A

Consists solely of alpha keratin

Has 4 important sections:

  1. Nail plate
  2. The nail matrix
  3. The nail bed
  4. Surrounding grooves
26
Q

What are the functions of nails?

A
  • Protect distal phalanges from damage
  • enhance precise delicate movement of digits
  • enhance fingertip sensitivity (nail itself has no nerve endings)
  • can be used as a tool
27
Q

How does growth rate of nails correlate to length of phalanges?

A

The longer the phalanx, the faster the rate of nail growth

Body Logistics (6 decks)

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