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Body Logistics > Lecture 19 - Skin > Flashcards

Lecture 19 - Skin Flashcards

1
Q

3 defining structure of the skin

A
  • Epidermis
  • Dermis
  • Hypodermis
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2
Q

Hypodermis

How is distinguished between males and females?

A

Men- thickest in the abdomen and shoulders

Women - thickest in the hips, thighs and buttocks

-thick on the palm of the hands on both sexes

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3
Q

Location of the Hypodermis

A
  • lowest layer of the skin

- also known as the sub-cutaneous layer

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4
Q

Structure of the Hypodermis

A
  • contains adipose tissue
  • nerves/blood vessels/lymphatic
  • loose connective tissue ; fibroblasts/macrophages/fibres/mastcells
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5
Q

Function of the Hypodermis

A
  • provides energy store : generates heat
  • insulator for underlying muscle heat generation
  • shock absorber: cushions impacts/protection for underlying structures
  • connects skin to underlying muscle and bones
  • makes hormones ,e.g:leptin to control eating habits
  • causes skin wrinkling and hypothermia in old age when thinned during ageing
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6
Q

Location of the Dermis

A

-Between epidermis and Hypodermis

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7
Q

Structure of the Dermis

A

3 layers

  • papillary : upper
  • reticular: lower
  • dermal papillae:interdigitating
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8
Q

Function of the Dermis

A
  • contains hairs and sweat glands; thermoregulation
  • contains sensory structures ;special senses - touch
  • gives structure to skin and so body shape
  • thinning of this layer during ageing is also responsible for skin wrinkling
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9
Q

Location of the Epidermis

A

Outermost layer of the skin

Made up of epithelial cells (keratinocytes )

Keratinised stratified squamous epithelium

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10
Q

Structure of the epidermis

A
  • 4 layers of cells (thin skin)
  • 5 layers (thick skin)
  • held together laterally by adherens junctions
  • some terminal nerve endings
  • NO blood vessels ( Avascular )

-

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11
Q

Function of the Epidermis

A
  • Prevents water loss
  • Prevents entry of bacteria and parasites
  • Special cells that present pathogens to immune cells
  • Synthesis of Keratin
  • Prevent underlying tissue loss due to abrasion
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12
Q

The Epidermis is made up of four layers / 5 layers in palms and soles of feet

What are the layers?

A
  • Stratum Corneum ( horny cell layer)
  • Stratum Lucidum (transparent layer):only on palms and soles of feet
  • Stratum granulosum (granular layer )
  • Stratum Spinosum (Spinous /prickle cell layer)
  • Stratum basale (basal cell layer)
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13
Q

Epidermis layers

Features of the Stratum Corneum ( horny cell layer )

A
  • outermost layer,made of squames (dead keratinocytes )
  • thick on palms and soles of feet ; prone to injury
  • continuously shed
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14
Q

Epidermis layers

Features of Stratum granulosum ( granular layer )

A
  • Stratified squamous epithelium
  • Lamellar granules
  • Tonofibrils made by lamellar bodies
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15
Q

What are lamellar granules ?

A

Filament associated proteins that assemble keratin fibrils and secret it

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16
Q

What are tonofibrils?

A

Bundles of keratin filaments and keratohyalin granules

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17
Q

Epidermis layer

Features of Stratum Spinosum ( spinous/prickle cell layer )

A
  • Cubiodal epithelium arranged in 3 layers ( held together by desmosomes )
  • Producers of lamellar bodies ( keratin factories )
  • first time Golgi appears
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18
Q

Epidermis layer

Features of Stratum Basale ( basal cell layer )

A
  • innermost of the cell layers of the epidermis
  • Tall columnar epithelial cells
  • constantly renew keratinocytes by cell division
  • As daughter cells differentiate , they move away from the epidermis dermis junction (loose their ability to differentiate )
  • produces keratin filaments (tonofilaments)
  • home to the melanocytes (produces melanin )
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19
Q

Role of Keratinocytes

A

Synthesise keratins (fibrous proteins) that contribute to the strength of the epidermis

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20
Q

Apart form contributing to the strength of the epidermis , what other roles is keratin used for ?

A
  • Hair
  • Nail
  • Animal horns
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21
Q

What is the normal transit time of a keratinocyte from basal layer to stratum Corneum ?

A

28-40 days

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22
Q

Cells found in the Epidermis

A
  • Melanocytes (stratum Basale)
  • Langerhans cells
  • Merkel cells
  • Keratinocytes
23
Q

Features of Melanocytes

A
  • produces melanin
  • number not increased in black /dark skin individuals
  • difficult to see histologically without special stain ( immunohistochemistry with S100 antibody )
24
Q

Features of Langerhans cells

A
  • difficult to see histologically without stains

- macrophages ; highly specialised capacity to present antigens to T lymphocytes to mediate immune reactions

25
Q

Features of Merkel cells

A
  • difficult to see histologically without special stains
  • mechanoreceptor cells associated with sensory nerve ending ;pressure touch

6% in white individuals
10% in black individuals

26
Q

State the two types of skin

A

Hairy skin - thin skin

Non hairy skin - thick skin

27
Q

Location of non hairy (thick) skin

A
  • Palmar surface of hand
  • Plantar surface of foot
  • Area between fingers and toes
28
Q

Structure of Non hairy (thick) skin

A
  • No hair, arrest or pills muscle, no sebaceous glands
  • Thicker stratum Corneum
  • Thinner dermis
  • Increased density of mechanoreceptors
29
Q

Function of Non hairy (thick) skin

A
  • Prevents tissue loss due to abrasion
  • Increased friction between skin and surfaces
  • Increased sensation
30
Q

Features of thick (non hairy ) skin

A
  • No hair follicles
  • No sebaceous glands
  • No arrector pili muscles
  • Pronounced ridges and furrows on surface
  • Regular shaped dermal papillae : interdigitation
  • Stratum lucidum often seen
31
Q

Features of thin (hairy skin)

A
  • Presence of hair follicles
  • Presence of sebaceous glands
  • Presence of arrector pili muscles
  • Smaller ridges and furrows
  • Irregular dermal papillae
  • Stratum lucidum absent
32
Q

What are skin appendages ?

A

Skin appendages are skin associated structures that serve a particular function

33
Q

Name 5 skin appendages

A
  • Hair
  • Arrector pili
  • Sebaceous glands
  • Sweat glands
  • Nails
34
Q

Skin appendages -Hair

Sate the three types of hair

A

Lanugo - covers developing foetus

Vellus - replaces lanugo after 2-3 days

Terminal - head ( scalp and eyebrows, nasal passage) armpit and external genital region

35
Q

Skin appendages - Hair

Features of Lanugo

A
  • sometimes seen at birth
  • covers developing foetus
  • very soft fine hair
36
Q

Skin appendages - Hair

Features of Vellus

A
  • replaces lanugo
  • short
  • thin
  • light coloured
  • soft
  • not connected to sebaceous gland
37
Q

Skin appendages - Hair

Features of Terminal

A
  • found on the head, armpit and external genital region
  • long, wide, dark coloured and coarse
  • produced by actions of testosterone
38
Q

Function of Hair on the skin

A
  • Thermoregulation
  • Sexual attraction (apocrine sweat glands)
  • Sensation (sensory nerve endings)
  • Protection (eyelashes , nasal hair, eyebrows , axillae hair)
39
Q

Skin appendages- Arrector pili muscle

Features of this

A
  • Consist of smooth muscle fibres attached to the papillary region of dermis and hair bulb
  • controls thermoregulation function of hair
  • may also induce sebum release from sebaceous gland
40
Q

Skin appendages-mechanoreceptors

State the mechanoreceptors found in the skin

A

End bulbs

Free nerve endings

Tactile discs

Meissner Corpuscle

Pacinian corpuscle

Ruffini’s corpuscle

Root hair plexus

41
Q

Skin appendages - mechanoreceptors

Role of end bulbs

A

Thermo receptors

Register temperature

42
Q

Skin appendages - mechanoreceptors

Role of free nerve endings

A

They have nociceptors

Register pain

43
Q

Skin appendages - mechanoreceptors

Role of tactile discs

A

Vertical dimpling of skin

Attaches to the basal layer keratinocytes

Senses touch, pressure and texture

Merkel in non hairy skin

Meissner in hairy skin

44
Q

Skin appendages - mechanoreceptors

Role of Meissner corpuscle

A

Detects tapping and flicker movements

45
Q

Skin appendages - mechanoreceptors

Role of pacinian corpuscle

A

Senses vibrations

46
Q

Skin appendages - mechanoreceptors

Role of Ruffini’s corpuscle

A

Senses joint movements and tissue stretch

47
Q

Skin appendages - mechanoreceptors

Role of root hair plexus

A

Senses vibrations in the hair shaft

48
Q

Skin appendages - sebaceous gland

Features of this

A

Produces an oily substance called sebum by Holocrine secretion

Found near the top and inside hair follicles or with sweat pores

Found on thick (eyelids ,nose) and thin skin (face, scalp)

Not found is the palms of hands and soles of feet

49
Q

Skin appendages - sweat glands

Features of this

A
  • simple coiled tubular gland
  • found deep to sebaceous gland and a little to one side
  • eccrine sweat glands and apocrine sweat glands
50
Q

Skin appendages - Nails

Location of Nails

A

Distal surface of fingers and Toes ( Phalanges)

51
Q

Skin appendages - Nails

Structure of nails

A

Consists solely of alpha keratin

  • nail plate
  • nail matrix
  • nail bed
52
Q

Skin appendages - Nails

Function on nails

A
  • protection of distal phalanx and surrounding soft tissue from injuries
  • enhances precise delicate movements
  • enhances sensitivity of finger tips (nails bed itself has no nerve endings )
  • as a tool e.g, extended precision grip
53
Q

Function of the skin

A
  • Protection and repair (kartinocytees, melanocytes, Langerhans cells, fibroblasts )
  • temperature regulation and excretion of waste products (sweat gland-apocrine)
  • lubrication (sebaceous glands)
  • storage ( white adipose cells provide lipids for energy )
  • vitamin d synthesis
  • absorption ( small amounts of water and oxygen)
  • aesthetics (as a mode of communication or attraction)
  • sensation (mechanoreceptors)

Body Logistics (6 decks)

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