Skin Structure and Function

Question 1

What are the two main layers of the skin called?

Answer 1

Dermis and Epidermis

Question 2

The epidermis is the outer layer of ________1________ and the dermis is beneath the epidermis and is _________2________

Answer 2

1) stratified cellular epithelium

2) connective tissue

Question 3

What is the origin of the epidermis?

Answer 3

Ectoderm

Question 4

What are the 4 layers of the epidermis from superficial too deep?

Answer 4

1- keratin layer
2- granular layer
3- prickle cell layer
4- basal layer

Question 5

The basal layer is usually ____1_______ there are lots of intermediate filaments such as ____2_____ and it is __3_____ metabolically active as _____4______

Answer 5

1) one cell thick with small cuboidal cells
2) keratin
3) highly
4) keratinocytes are constantly being made and moving up from the basement membrane

Question 6

The prickle cell layer contains _____1_____ The cells have lots of __2___ which anchor the cells to each other and contain tufts of intermediate filaments

Answer 6

1) larger polyhedral cells

2) desmosomes

Question 7

In the granular layer ____1_______ are synthesised then secreted by ____2______ to form a _______3_______As cells move outwards they are beginning _____4_____

Answer 7

1) lipid and lipid hydrolyses
2) lamellar bodies
3) water tight intercellular lipid bilayer
4) to lose their nuclei and die

Question 8

What do lamellar bodies in the granular cell layer of the epidermis produce? What is its function?

Answer 8

Pro-filaggrin which is concerted to filaggrin in the outer layer. Filaggrin has a dual role in holding moisture within cells and as a component of tough protein cell envelope.

Question 9

The keratin layer is made up of ___1____ It forms a ___2____

Answer 9

1) overlapping non-nucleated cell remnants.

2) a tight, waterproof barrier

Question 10

95% of epidermal cells are keratinocytes but name 3 other types of cells in the epidermis

Answer 10

melanocytes, langerhan’s cells and merkel cells

Question 11

Where do melanocytes originate from and reside in?

Answer 11

Originate from the neural crest and reside in the basal layer

Question 12

Describe the function of melanocytes

Answer 12

They contain organelles called melanosomes which convert tyrosine to melanin pigment. Melanin is transferred into the surrounding keratinocytes to give protection against UV radiation.

Question 13

What causes racial differences in skin colour?

Answer 13

Variation in melanin production not melanocyte number.

Question 14

Where are langerhan’s cells found?

Answer 14

In the prickle cell layer as well as the dermis and lymph nodes

Question 15

Describe the function of langerhan’s cells

Answer 15

Play a role in antigen presentation and immunoregulation

Question 16

Where are merkel cells found?

Answer 16

In the basal layer between keratinocytes and nerve fibres

Question 17

Describe the function of merkel cells

Answer 17

They are mechanoreceptors and play a role in sensation. They are numerous on the fingertips and in the oral cavity.

Question 18

Describe the hair cycle

Answer 18

Anagen- growth
Catagen- involution
Telogen- shedding
At any one time most hairs will be in the anagen phase (more than 90%) which is usually 3-5yrs for scalp hair

Question 19

What are the three types of hair?

Answer 19

Terminal (medullated coarse hair e.g. scalp, pubic).
Vellus (non-medullated fine hairs e.g. women and children faces)
Lanugo (non-medulalted fetal hair)

Question 20

Nails are tough plates of hardened ___1____ which arise from the ___2____ Growth rate is about __3___ Finger nails grow __4__ than toe nails and growth rate is ___5___ in summer than winter

Answer 20

1) keratin
2) nail matrix (just visible as the moon-shaped lunula)
3) 0.1mm/day
4) faster
5) faster

Question 21

Function of the demo-epidermal junction?

Answer 21

It has a key role in epithelial-mesenchymal interactions. It helps with support, anchorage, adhesion, growth and differentiation of basal cells. It is also a semi-permeable membrane acting as a barrier and filter.

Question 22

3 layers of the demo-epidermal junction/

Answer 22

Lamina lucida, lamina densa, sub-lamina densa zone

Question 23

What is the origin of the dermis?

Answer 23

Mesoderm

Question 24

What does the dermis contain?

Answer 24

Fibroblasts, mast cells, lymphocytes, dermal dendritic cells, langerhans cells and macrophages. It also contains blood and lymphatic vessels, nerves, muscle and appendages e.g. glands.

Question 25

Describe blood vessels in the dermis

Answer 25

Supply is greater than metabolic need as they also help with temperature regulation. The vessel walls are well supported and there are horizontal plexuses.

Question 26

Describe lymphatic vessels in the dermis

Answer 26

Sub epidermal meshed networks. There is continual drainage of plasma proteins, extravasated cells and excess interstitial fluid. Important immune functions like surveillance

Question 27

Describe nerves in the dermis

Answer 27

Somatic sensory dermatomes have free nerve endings and special receptors e.g. pacinian (pressure) and Meissners (vibration) corpuscles

Autonomic nerve supply- acts on blood vessels, nerves and glands.

Question 28

3 types of skin glands?

Answer 28

Eccrine, apocrine and sebaceous

Question 29

Describe eccrine glands

Answer 29

these are found on all of the skin surface, responsible for thermoregulation and sweating

Question 30

Describe apocrine glands

Answer 30

Found in the axillae and anogenital area and do not function until puberty. Function is not fully understood.

Question 31

Describe sebaceous glands

Answer 31

These are also inactive until puberty when they excrete an oily substance called sebum under the influence of androgens. Sebum passes onto the skin surface via the pilosebaceous duct (hair follicle). Its lipids contribute to the skin barrier and have antimicrobial actions. Sebaceous glands are found in the highest density on the face, scalp and upper torso.

Question 32

How is the skin involved in metabolism and detoxification?

Answer 32

Involved in vit d metabolism, thyroid hormone metabolism, defence against chemicals, drugs, pollution and sunlight.

Question 33

How does the skin act as a barrier?

Answer 33

Physical barrier, chemical secretions stop pathogens

Question 34

How is the skin involved in thermoregulation?

Answer 34

Thermoreceptors sense changes, then get sweating, shivering and changes in blood flow

Question 35

How is the skin involved in the immune defence?

Answer 35

Takes part in the specific and non specific reaction

Question 36

How is the skin involved in communication?

Answer 36

Visual and odour

Question 37

How is the skin involved in sense?

Answer 37

Touch, pressure, temperature, vibration sensors.

Question 38

What cells carry out vitamin D metabolism?

Answer 38

Keratinocytes

Question 39

What percentage of GP consultations are for skin disease

Answer 39

15-23

Question 40

The nail lunula is…

Answer 40

the visible part of the nail matrix. the nail matrix sits under

Question 41

Developmental growth pattern of skin follows what lines

Answer 41

Blaschkos lines

Question 42

Define the hyponychium of nails

Answer 42

The hyponychium is the area of epithelium, particularly the thickened portion, underlying the free edge of the nail plate on the nail. Basically the end of the nail.

Question 43

Lamellar bodies are also called …. found in ….

Answer 43

odland bodies found in granular cell layer

Question 44

What is ground substance? Where is it found?

Answer 44

FOUND IN THE DERMIS
Ground substance is an amorphous gel-like substance in the extracellular space that contains all components of the extracellular matrix (ECM) except for fibrous materials such as collagen and elastin.