Skin structure and function 1

Question 1

What are the two main layers that make up the skin and what are each layer primarily made up off? include how they relate to each other in terms of position

Answer 1

The two main layers of skin are the epidermis and dermis.

Epidermis is the outer layer of the skin so lies about the (inner layer) dermis which is the connective tissue.

• The epidermis made up off stratified cellular epithelium (stratified squamous epithelium)
• The dermis is made up off connective tissue

Question 2

In basic embryological terms how is the epidermis made?

Answer 2

Formed from the ectoderm - ectoderm cells form a single later periderm, there is then a gradual increase in the layers of cells, the periderm is then cast off, the epidermis is then formed

Question 3

In basic embryological terms what is the dermis formed from ?(germ layer)

Answer 3

Formed from mesoderm below ectoderm

Question 4

What are melanocytes and where do they come from in terms of embryological development of the skin ?

Answer 4

They are pigment producing dendritic cells that come from the neural crest and migrate to the epidermis (basal layer and above)

Question 5

What are the different layers of skin developed at each of the stages; week 4, 16 and 24 in foetal skin development ?

Answer 5

At week 4 - Periderm, Basal layer, Dermis (corium) have developed.

At week 16 - Keratin Layer, Granular Layer, Prickle cell, Layer, Basal Layer, Dermis have developed.

At week 24 - the same layers in 16 have developed but there is now also hair follicles and sebaceous glands developed.

Question 6

What are Blaschko’s lines?

Answer 6

They are the developmental growth pattern of skin - they don’t follow nerves, vessels or lymphatics

Question 7

What are the main components of skin?

Answer 7

Epidermis

Appendages:

• Nails
• Hair
• Glands
• Mucosae

Dermo-epidermal junction

Dermis: connective tissue, less cellular

Sub-cutis: predominantly fat

Question 8

Which type of cells makes up for 95% of the cells in the epidermis ? and what do they contain

Answer 8

Keratinocytes - which contain keratin.

Question 9

What are the other less common cells are found in the epidermis ?

Answer 9

• Melanocytes
• Langerhans cells
• Merkel cells

Question 10

What are the 4 distinct layers within the epidermis ?

Answer 10

• Keratin layer
• Granular layer
• Prickle layer
• Basal layer

Question 11

where do keratinocytes migrate from ?

Answer 11

The basement membrane

Question 12

Regulation of epidermal turnover is a balance between cells in/out controlled by growth factors, hormones and cell death. Name 2 conditions where there is a loss in control of epidermal turnover ?

Answer 12

• Skin cancer
• Psoriasis

Question 13

What is the condition shown?

Answer 13

Psoriasis

Question 14

What condition is shown? what should it look like ?

Answer 14

Psoriasis

Question 15

What type of cells is the basal layer made up of and what does it have lots of in it ?

Answer 15

Made up of small cubodial cells with lots of intermediate filaments (keratin) in it

Question 16

What type of cells make up the prickle layer and what does it have in it ?

Answer 16

Made up of larger polyhedral cells.

Has lots of desmosomes (connections) with intermediate filaments connecting to the desmosomes

Question 17

Describe the features of the granular layer and the appearance of the cells which make it up?

Answer 17

• Made up by 2-3 layers of flatter cells.
• Contains Large keratohyalin granules – contain structural filaggrin & involucrin proteins
• Odland bodies (lamellar bodies) present
• High lipid content
• Origin of “cornified envelope”
• Cell nuclei lost - e.g. in keratinocytes they loose their nuclei

Question 18

Describe the features of the keratin layer

Answer 18

• Contains corneocytes - which are overlapping non-nucleated cell remnants
• Contains lamellar granules which release lipid
• It is a tight waterproof barrier
• Insoluble cornified envelope
• 80% keratin & filaggrin

Question 19

Give an example of a skin disease which affects keratinocytes?

Answer 19

HPV - Human papilloma virus infection of keratinocytes causes warts

Question 20

Note that mucosal surfaces can also be affected by skin disease

Answer 20

appreciate this