Skin Structure and Function

Question 1

What embryology layer does the epidermis arise from?

Answer 1

Ectoderm

Question 2

What embryology layer does the dermis arise from?

Answer 2

Mesoderm

Question 3

Where do melanocytes arise from in embryology?

Answer 3

Neural crest

Question 4

What are the layers of the epidermis from superficial to deep?

Answer 4

Keratin layer
Granular layer
prickle cell layer
Basal layer
Dermis

Question 5

What type of cells make up the epidermis?

Answer 5

Stratified squamous epithelium

Question 6

Basal layer

• What type of cell?
• Special feature?
• Metabolic feature?

Answer 6

Small cuboidal
Lots of intermediate filaments (keratin)
Highly metabolically active

Question 7

Prickle cell layer

• What type of cells?
• Special feature?

Answer 7

Larger polyherdral
Lots of desmosomes
Intermediate filaments connect desmosomes

Question 8

Granular layer

• What is the function of the large keratohylin granules?
• Lipid content?

Answer 8

Contain structural filaggrin & involucrin proteins

Question 9

Where are lamellar (Oddland) bodies found?

What is their significance?

Answer 9

Granular layer

These are secretory organelles found in type II pneumocytes and keratinocytes.

Question 10

Keratin layer

- Nuclei?

Answer 10

No nuclei

Question 11

What type of cell are melanocytes?
Which organelles do they contain which allows them to do their job?
What are the two types of melanin?
What is the function of melanin and how does it do this?

Answer 11

Pigment producing dendritic cells
Melanocytes contain organelles called “melanosomes”, which convert tyrosine to melanin pigment, of which there are two types:
- Eumelanin (brown or black)
- Phaeomelanin (red, yellow)
Melanin absorbs light (neutral density filter).
Full melanosomes (‘melanin granules’) are transferred to adjacent keratinocytes via dendrites, where they form a protective cap over the nucleus.
Melanin caps protect the nuclear DNA in basal cells.

Question 12

Langerhans cells
What cell type?
Where are they found?
Function?

Answer 12

Dendritic
Prickle cell level in epidermis; also found in dermis and lymph nodes
Antigen presenting cells - pick up antigen in skin and circulate to lymph nodes via lymphatic system
Act as “hoovers” to bacteria in the skin

Question 13

Merkel cells
Where are they located?
Function?

Answer 13

Reside in clusters at the tips of nerves, lining the epidermis
Act as mechanoreceptors

Question 14

Meissner’s corpuscles
Location?
Function?

Answer 14

These are nerve endings which lie wedged in the DEJ

Sense light touch

Question 15

Hair follicles - pilosebaceous unit
Location?
What lies adjacent?

Answer 15

Mostly in epidermis, except follicle, which lies in dermis
Sebaceous gland - grease sits on top of the muscle
Arrector pili muscle

Question 16

What are the three phases of growth in hair follicles?

How long is each?

Answer 16

Anagen = growing, 3-7 years, 90% of hairs
Catagen = involuting, 3-4 weeks, 10% hairs
Telogen = resting phase, each day 50-100; <1% hairs

Question 17

Where does the pigment that makes hair brown lie?

Answer 17

In the matrix of the follicles

Question 18

Revise histological structure of pilosebaceous unit + nail

Answer 18

Revise histological structure of pilosebaceous unit + nail

Question 19

Dermis
Main cell type?
Other cell types?
What else does it contain?

Answer 19

Fibroblast - make collagen and elastic fibers
Macrophages, lymphocytes, mast cells, langerhans cells
Collagen, ground substance, blood vessels, lymphatics, nerves

Question 20

What are the special nerve receptors in the dermis?

Answer 20

Pacinian - pressure

Meissners - vibration

Question 21

What are the three types of skin gland?

Answer 21

1. Sebaceous
2. Apocrine
3. Eccrine

Question 22

Sebaceous glands

Function?

Answer 22

Control moisture loss and protection from bacterial and fungal infection

Question 23

Apocrine sweat glands
Where are they found?
Dependent on what?
Function?

Answer 23

Axillae and perineum
Androgen dependent
Produce oily fluid –> odour after bacterial decomposition
“Scent glands”

Question 24

Eccrine sweat glands
Where are they found?
Function?

Answer 24

Cover the whole body surface - palms, soles and axillae in particular
Functions include cooling by evaporation, moisten palms/soles to aid grip

Question 25

Give a list of basic functions of the skin

Answer 25

• Barrier function
• Metabolism & detoxification
• Thermoregulation
• Immune defence
• Communication
• Sensory functions