Skin Structure and Function

Question 1

What are the 2 main layers of skin?

Answer 1

The epidermis (outer) and the dermis

Question 2

Which germ layer is the epidermis derived from?

Answer 2

ectoderm

Question 3

How does the epidermis form in the fetus?

Answer 3

Ectoderm cells form a single layer periderm which gradually increase in layers and before birth the periderm cells are cast off

Question 4

What germ layer is the dermis derived from?

Answer 4

mesoderm

Question 5

What are melanocytes derived from?

Answer 5

the neural crest

Question 6

What are the 6 layers in skin?

Answer 6

Keratin layer
Granular layer
Prickle cell layer
basal layer
dermis
sub-cutis

Question 7

what are blaschkos lines?

Answer 7

developmental growth patterns of skin, which don’t follow vessels, nerves or lympathics

Question 8

What does the skin consist of?

Answer 8

epidermis; appendages (hair, nails, glands, mucosae) ; dermo-epidermal junction; dermis and the sub-cutis

Question 9

What does the basal layer do?

Answer 9

Divides in order to replenish the upper layers

Question 10

How does the prickle cell layer become the granular layer?

Answer 10

It differentiates and produces lots of protein (granular- lots of proteins)

Question 11

How does the granular layer becoem the keratin layer?

Answer 11

Releases protein in order to become flat

Question 12

What type of epithelium is the epidermis

Answer 12

stratified squamous epithelium

Question 13

What are the majority of the cells found in the epidermis?

Answer 13

Keratinocytes which contain structural keratins

Question 14

What other cells are found within the epidermis?

Answer 14

Melanocytes; langerhan cells and merkel cells

Question 15

How is epidermal turnover regulated?

Answer 15

growth factors; cell death and hormones

Question 16

How long does it take for a keratinocytes to migrates from the basmement membrane to the top?

Answer 16

28 days

Question 17

Describe the basal layer

Answer 17

usually one cell thick
small cuboidal
lots of intermediate filaments (keratin)
highly metabolically active

Question 18

Describe the prickle cell layer

Answer 18

larger polyhedral cells
lots of desmosomes
intermediate filaments connect to desmosomes
(named after prickly pear appearance)

Question 19

Describe the granular layer

Answer 19

2-3 layers of flatter cells
large keratohyalin granules- contain structural filaggrin and involucrin proteins
odland bodies ( lamellar bodies)
high lipid content
origin of "cornified envelope"
cell nuclei lost

Question 20

What is the cornified envelope?

Answer 20

A layer of ceramides which become covalently bonded to an envelope of structural proteins. This replaces the cell membrane during a process called cornification in which live keratinocytes become non-living corneocytes. The complex surrounds the cells and contributes to the barrier function of the skin.

Question 21

Describe the keratin layer

Answer 21

Made up of the corneocytes- overlapping non-nucleated cell remnants
insoluble cornified envelope
80% keratin and filagrin
lamellar granuels release lipid
TIGHT WATRETPROOF BARRIER

Question 22

What are melanocytes?

Answer 22

pigment producing dendritic cells

Question 23

Where are melanocytes found?

Answer 23

in the basal layer and above

Question 24

What happens in the melanosomes?

Answer 24

tyrosine is converted to melanin pigment

Question 25

What happens to full melanosomes (melanin granules)?

Answer 25

they are transferred to adjacent keratinocyte via dendrites

Question 26

What is the function of melanin granules?

Answer 26

form a protective cap over nucleus as they absorb light and prevent UV ray messing with the DNA in basal cells

Question 27

What is vitiligo?

Answer 27

an autoimmune disease where there is loss of melanocytes

Question 28

What is the origin of langerhan cells?

Answer 28

mesenchymal origin (bone marrow)

Question 29

Where are Langerhan cells found in the skin?

Answer 29

prickle cell level in the epidermis and in dermis (also in lymph nodes)

Question 30

What is the function of langerhan cells?

Answer 30

APCs - pick up Ag in skin and circulate to lymph nodes via lymphatics

Question 31

What is the special organelle found in langerhan cells?

Answer 31

birbeck granules/ racket organelle (looks like a tennis racket)

Question 32

Where are Merkel cells found?

Answer 32

in the basal layer between keratinocytes and nerve fibres

Question 33

What are merkel cells?

Answer 33

mechanoreceptors

Question 34

Look at picture of hair follicle and be able to name different parts of it

Answer 34

``` :) sebaceous unit (grease bag that sits on top of muscle) pili arrector muscle dermal papilla matrix cortex medulla interal and external root sheaths ```

Question 35

What are the 3 phases of growth in a hair follicel

Answer 35

anagen- growing catagen- involuting telogen- resting

Question 36

What is telogen effluvium?

Answer 36

when stress pushes more hair follicles prematurely into the telogen phase (meaning more fall out)

Question 37

When does telogen effluvium most commonly occur?

Answer 37

postpartum

Question 38

How is the nail plate and the matrix of a nail connected?

Answer 38

The 3 partsof the nail plate- dorsal; intermediate and ventral all grow from the same corresponding subdivision of the matrix

Question 39

What are the functions of the dermo-epithelial junction?

Answer 39

- support; anchorage; adhesion; growth and differentiation of basal cells - semi-permeable membrane acting as a barrier and filter between the epithelium and mesenchyme

Question 40

What cells are found in the dermis?

Answer 40

fibroblasts, macrohpages, mast cells, lymphocytes and langerhan cells

Question 41

what fibres are found in the dermis?

Answer 41

collagen and elastin

Question 42

Describe the blood vessels found within the dermis

Answer 42

The supply is greater than metabolic need vessel walls are well spported plexuses are horizontal

Question 43

What is an angioma?

Answer 43

localised overgrowth of blood vessels

Question 44

What is the somatic sensory supply of the dermis like?

Answer 44

there are: free nerve endings speical receptors for pressure-pacinian corpuscles and for vibration- meissners corpuscles

Question 45

Where does the pigmentation of the hair follicles take place?

Answer 45

In the melanocytes above the dermal papilla

Question 46

What are the 3 types of skin glands?

Answer 46

sebaceous; apocrine and eccrine

Question 47

Describe sebaceous glands

Answer 47

``` widely distrbuted but the largest glands are in the face and chest produce sebum hormone sensitive (dont do anything before puberty) ```

Question 48

what are the functions of sebaceous glands?

Answer 48

control moisture loss and protect from fungal infections

Question 49

what is sebum made from?

Answer 49

squalene, wax esters, triglycerides and free FAs

Question 50

Decribe apocrine sweat glands

Answer 50

develop as part of pilo-sebaceous unit found in axillae and perineum androgen dependent produce oily fliud- odour after bacterial decomp

Question 51

Describe eccrine sweat glands

Answer 51

whole skin surface- especailly skin, soles and axillae | sympathetic cholienrgic nerve supply

Question 52

function of eccrine sweat glands?

Answer 52

cooling by evap | moisten palms/soles to aid grip

Question 53

Why would you describe the skin as metabolically active?

Answer 53

takes part in vitamin D metabolism and thyroid hormone metabolism (which also occurs in thyroid gland-20%)

Question 54

What are the sensory functions of the skin

Answer 54

touch, pressure, vibration, pain and itch, heat and cold

Question 55

What cells carry out vitamin D metabolism?

Answer 55

keratinocytes

Question 56

Where are hemi-desmosomes found?

Answer 56

In the DEJ

Question 57

What are commonest sweat glands in the face?

Answer 57

eccrine glands

Question 58

Which hormone stimulates the sebaceous glands production of sebum?

Answer 58

androgen

Question 59

Which glands play a role in temperature regulation?

Answer 59

eccrine glands

Question 60

Which glands play a role in scent?

Answer 60

apocrine glands