Functional Anatomy and Physiology of the Skin

Question 1

Name the 4 layers of the Epidermis

Answer 1

Basal Layer, Granular Layer, Prickle cell layer and Keratin layer

Question 2

What cell type makes up 95% of the epidermis?

Answer 2

Keratinocytes

Question 3

What is the main proliferative compartment within the epidermis?

Answer 3

The basal layer

Question 4

What happens at the basal layer of the epidermis?

Answer 4

The keratinocytes migrate from the basal layer to the top later. They differentiate, producing a variety of protein and lipid products

Question 5

What is the normal time for differentiation from the basal layer to the keratin layer of the epidermis?

Answer 5

28 days

Question 6

What are the main features of the Prickle cell layer?

Answer 6

Larger Polyhedral cells and lots of Desmosomes

Question 7

What happens to the keratinocytes at the Granular layer of the Epidermis?

Answer 7

They undergo apoptosis

Question 8

What are the main features of the Granular Layer?

Answer 8

Cell nuclei lost, 2-3 layers of flatter cells, high lipid content

Question 9

What layer can you not see in psoriasis?

Answer 9

Granular layer

Question 10

Where does terminal differentiation occur?

Answer 10

At the Keratin layer

Question 11

How does terminal differentiation take place?

Answer 11

Filaggrin aggregates keratin filaments and causes terminal differentiation

Question 12

What are the features of the keratin layer of the Epidermis?

Answer 12

Flattened corneocytes with no nucleus and overlapping cells which creates a tight waterproof barrier

Question 13

What is psoriasis?

Answer 13

Ongoing, non stop phase of a wound reaction, increased production of skin cells

Question 14

What is the difference in time for normal differentiation and psoriasis?

Answer 14

Normal: 28 days
Psoriasis: 4-5 days

Question 15

How does intraepidermal blisters arise?

Answer 15

Lots of hydrostatic water pushes apart the desmosomes within the Prickle cell layer, forming a huge dome

Question 16

How is the regulation of epidermal turnover controlled?

Answer 16

By growth factors, cell death and hormones

or Loss in control in: skin cancer and psoriasis

Question 17

What are the skin appendages?

Answer 17

Nails, hair, mucosae, glands

Question 18

Name 3 other major types of cell within the epidermal layer

Answer 18

Melanocytes, Langerhans cells, Merkel cells

Question 19

What happens at the melanocytes?

Answer 19

The Melanin pigment is synthesised from Tyrosine–> Melanin absorbs light–> Full Melanocomes are transferred to adjacent keratinocytes via dendrites

Question 20

Name two of the melanin pigments in the Melanocytes

Answer 20

Euchelanin (brown or black)

Phaeomelanin (red or yellow)

Question 21

What is the function of melanin caps?

Answer 21

To protect the nuclear DNA in the basal cells

Question 22

What is the role of the Langerhans cells in the Epidermal layer?

Answer 22

They are involved in the skin immune system, in the antigen presentation to lymphocytes
They circulate between the epidermis and the lymph nodes

Question 23

What are Birbeck granules?

Answer 23

Organelles within the Langerhans cells with an unknown function

Question 24

Where are Langerhans cells found in the epidermis?

Answer 24

Dispersed at the prickel cell level, very densely packed together

Question 25

What are Merkel cells?

Answer 25

Mechanoreceptors which are found in the basal layer

Question 26

What happens to Merkel cells in diabetes patients?

Answer 26

Merkel cells are myelinated--> Diabetes affects the myelin sheaths, glucose disrupts the protein arrangement and the sheath no longer conducts--> This causes paraethesia or itchiness

Question 27

What can affect the Merkel cells?

Answer 27

A specific viral infection which has a high mortality rate

Question 28

Where are the Merkel cells?

Answer 28

In the basal layer

Question 29

What is Vitiligo?

Answer 29

An autoimmune disease with loss of melanocytes - "white spot disease: - constant and active loss of melanocytes

Question 30

What is Albinism?

Answer 30

Genetic partial loss of pigment production

Question 31

What is Nelson's syndrome?

Answer 31

Melanin stimulating hormone is produced in excess by the pituitary

Question 32

What is Virilisation?

Answer 32

Excess hair on women (facial hair etc) due to excess androgen from a tumour

Question 33

What is Alopecia Areata?

Answer 33

An autoimmune condition which caused hair loss. Can be triggered by massive psychosocial stress such as bereavement or pregnancy

Question 34

What can you look at as a sign of internal inflammation?

Answer 34

Nails

Question 35

During the hair cycle what do these phases refer to, and for how long dot they last?: - Anagen - Catagen - Telogen

Answer 35

- Anagen: growing (years) - Catagen: transitional (a few days) - Telogen: resting phase (3 months)

Question 36

What is the difference between lanugo hair and vellum hair?

Answer 36

Lanugo: newborns and non pigmented Vellus: similar to lanugo but pigmented

Question 37

Why do we have lots of hair?

Answer 37

To reduce the need to have melanin and melanocytes

Question 38

What are the three layers of the Dermo-epidermal junction?

Answer 38

- Lamina lucida - Lamina densa - Sublamina densa

Question 39

What are some of the components of the dermis?

Answer 39

- 75% collagen - 1% elastin - mast cells, langerhans, blood vessels, lymphatics, ground substance, T lymphocytes

Question 40

What is the function of the basement membrane?

Answer 40

allows the movement of cells and nutrients between the dermis and epidermis

Question 41

How are the cell membrane of the epidermal basal cell and the basement membrane attached?

Answer 41

By hemi-desmosomes

Question 42

What is present at the DEJ?

Answer 42

Proteins, fibrils and keratins

Question 43

What happens to the DEJ during old age?

Answer 43

Becomes flatter | -wrinkles are caused by tired elastic

Question 44

What does smoking and UV do to the DEJ?

Answer 44

depletes the collagen

Question 45

What happens in inherited diseases of the DEJ?

Answer 45

Skin fragility due to a mutation in one of the proteins

Question 46

Give examples of inherited diseases of the DEJ

Answer 46

Epidermolysis bullosa simplex or dystrophic

Question 47

Give an examples of an acquired disease of the DEJ

Answer 47

Bullous Permohigoid - Type 2 hypersenstivity reaction - formation of anti-hemidesmosome antibodies - treated with steroids

Question 48

What is Meissner's corpuscle?

Answer 48

- Dermis nerves | - Touch receptors in the fingertips

Question 49

What is Pacinian Corposcle?

Answer 49

- Dermis nerves | - Pressure receptors

Question 50

What can chronic lymphoedema be seen as?

Answer 50

"Elephantism"

Question 51

What is the function of the lymphatic vessels of the dermis?

Answer 51

Continual drainage of plasma proteins, extravasated cells and excess interstitial fluid

Question 52

What are the three main skin glands in the dermis?

Answer 52

- Sebaceous - Eccrine - Apocrine

Question 53

What do Eccine glands do?

Answer 53

- Whole body sweat glands - None in groin and mouth - Cools by evaporation

Question 54

What do Apocrine glands do?

Answer 54

- In axillary and groin - Produce oily fluid - Odour

Question 55

What do Sebaceous glands do?

Answer 55

- Produces sebum - Activated during puberty - Moisture control - Opens onto hair follicle - High concentration on face and back

Question 56

Name the main functions of the skin

Answer 56

Barrier function, metabolism and detoxification, thermoregulation, immune defence, communication, sensory functions

Question 57

What is Toxic Epidermal Necrolysis?

Answer 57

Acute skin failure, usually caused by a reaction to drugs | -rare and life threatening

Question 58

What is erthyroderma?

Answer 58

Another type of acute skin failure, red skin all over 80-90% of the body - skin peeling off in layers - can be due to a number of conditions such as dermatitis, psoriasis and T cell lymphoma

Question 59

How can statins cause dry skin?

Answer 59

- Lowers cholesterol | - skin is made up of "brick and mortar" with brick being keratin and mortar cholesterol

Question 60

In dermatitis, if the skin between the fingertips is affected what is it more likely to be?

Answer 60

Irritancy

Question 61

What is the function of melanocytes?

Answer 61

Absorb UV rays

Question 62

How is vitamin D3 produced?

Answer 62

By photosynthesis

Question 63

How is vitamin D stored and converted?

Answer 63

D3 is stored as hydroxycholecalciferol in liver | This is converted to 1,25-dihydroxycholecaliferol in the kidney

Question 64

What vitamin do kidney failure patients need?

Answer 64

Vitamin D

Question 65

Where is T4 metabolised to T3?

Answer 65

- 20% conversion occurs in thyroid gland | - 80% conversion in the peripheral tissues including skin

Question 66

What is more abundant T3 or T4?

Answer 66

T4 is more abundant but less active

Question 67

What happens when body temperature decreases?

Answer 67

Blood flows from the superficial plexus

Question 68

What is Hansen's disease?

Answer 68

TB Leprosy | Granuloma formation around peripheral nerves, causing damage due to immune response

Question 69

Name some autoimmune diseases

Answer 69

Eczema herpeticum, chronic discoid lupus erythmatous, squamous cell carcinoma

Question 70

How does the epidermis form in embryology?

Answer 70

- Ectoderm cells form single layer periderm - There is a gradual increase in layer of cells - Periderm casts off

Question 71

How does the dermis form in embryology?

Answer 71

Formed from mesoderm below ectoderm

Question 72

How does the melanocytes form in embryology?

Answer 72

Pigment producing cells from the neural crest

Question 73

What does the foetal skin look like at 4 weeks?

Answer 73

Periderm, Basal layer and dermis

Question 74

What happens in the foetal skin at 16 weeks?

Answer 74

Melanocytes migrate from neural crest

Question 75

What are Blascho's lines?

Answer 75

Developmental growth pattern of skin which doesn't follow vessels or lymphatics