Skin

Question 1

What is the general structure of the skin?

Answer 1

Epidermis
Dermis
Hypodermis

Question 2

Where is the hypodermis?

Answer 2

This is the deepest lying skin tissue.

Question 3

How does the thickness of the hypodermis vary?

Answer 3

Depending on the part of the body

Question 4

Where can you find the thickest hypodermis in men?

Answer 4

Abdomen and shoulders

Question 5

Where can you find the thickest hypodermis in women?

Answer 5

Hips, thighs and buttocks

Question 6

What is the structure of the hypodermis?

Answer 6

Mainly contain adipose tissue
Some neurovascular bundles as well as lymphatics
Loose connective tissue with fibroblasts, macrophages and fibres.

Question 7

What are the functions of the hypodermis?

Answer 7

Energy store and generation of heat
Insulator
Shock absorber and cushioning
Connects the skin to underlying muscle and bone
Make hormones such as leptin

Question 8

Where is the dermis?

Answer 8

Between the hypodermis and the epidermis.

Question 9

What is the structure of the dermis?

Answer 9

It has three layers:
Papillary (upper)
Reticular (lower)
Dermal papillae (interdigitating)

Question 10

What are the functions of the dermis?

Answer 10

It contains hairs and sweat glands for thermoregulation
Sensory like touch
Gives structure to skin and body shape

Question 11

Where can you find the epidermis?

Answer 11

It is the outermost layer of the skin.

Question 12

What kind of cells can be found in the epidermis?

Answer 12

Keratinocytes, melanocytes, immune cells (langerhans’ cells), Merkel cells

Question 13

What two type of epidermis are there?

Answer 13

Thin skin and thick skin

Question 14

What are the main differences between thin and thick skin?

Answer 14

Thin skin tends to be hairy
Thick skin tends to be non-hairy
Thin skin has 4 layers
Thick skin has 5 layers

Question 15

What are some exception to this rule?

Answer 15

Lips, back of ear, some areas of external genitalia and eyes. These exceptions are thin skin but not hairy.

Question 16

What are the four layers of thin skin?

Answer 16

Stratum corneum
Stratum granulosum
Stratum spinosum
Stratum basale

Question 17

What are the five layers of thick skin?

Answer 17

Stratum corneum
Stratum lucid
Stratum granulosum
Stratum spinosum
Stratum basale

Question 18

What is the structure of the epidermis?

Answer 18

It is held together by adherens junctions
They have terminal nerve endings
No blood vessels found

Question 19

What are the functions of the epidermis?

Answer 19

Prevent water loss
Prevent entry to bacteria and parasites
Special cells that present pathogens to immune cells
Synthesis of keratin
Prevents tissue loss due to abrasion

Question 20

What is the stratum corneum?

Answer 20

The outermost layer that is made of dead keratinocytes (keratin).
This is especially thick on palms and soles

Question 21

What is the stratum granulosum?

Answer 21

Stratified squamous epithelium
It contains lammetlar granules which assemble keratin fibrils and secrete it.
It also contains tonofibrils that are made by the lamellar bodies

Question 22

What is the stratum spinosum?

Answer 22

A stratified cuboidal epithelium held together by desmosomes.
Produces lamellar bodies.
This is where Golgi apparatus first appear (proximal to distal)

Question 23

What is the stratum basale?

Answer 23

Stratified columnar epithelial
This is where keratinocytes are constantly renewed by cell division
The daughter cells differentiate and mover away from the epidermis-dermis junction
These daughter cells make keratin filaments also called tonofilaments.
This is also where you find melanocytes.

Question 24

What is the role of keratinocytes?

Answer 24

To synthesise keratin (fibrous protein) which contribute to the strength of the epidermis.

Question 25

What is the normal transit time of a keratinocyte from the stratum basale to the stratum corneum?

Answer 25

28-40 days.

Question 26

What is psoriasis?

Answer 26

A skin disease where the transit time of the keratinocytes is reduced greatly from 28-40 days to 2-3 days. This results in an abundance of keratin and silvery scales. Langerhans' cell presence and lymphocytes in the stratum corneum also.

Question 27

What is hyperkeratosis?

Answer 27

When there is too much keratin put on the surface of the skin. This results in thickening of the skin.

Question 28

What are melanocytes?

Answer 28

Cells found in the epidermis, most commonly in the stratum basale. Produce melanin.

Question 29

What are Langerhans' cells?

Answer 29

Specialised cells to present antigens to T lymphocytes to mediate immune reactions. An example is allergic contact dermatitis.

Question 30

What are Merkel cells?

Answer 30

Mechanoreceptor cells associated with sensory nerve endings.

Question 31

Where can you find thick skin?

Answer 31

Palms, soles and area between fingers and toes (webs)

Question 32

How does thick skin differ to thin skin structurally?

Answer 32

No hair, no arrector pili muscles, no sebaceous glands. Thicker stratum corneum Thinner dermis Increased density of mechanoreceptors

Question 33

What are the functions of thick skin?

Answer 33

Prevent tissue loss due to abrasion Increased friction between skin and surfaces Increased sensation

Question 34

What are the three types of hair?

Answer 34

Lanugo Vellus Terminal

Question 35

Where can you find Lanugo?

Answer 35

Cover the developing foetus and can sometimes be seen at birth.

Question 36

Where can you find Vellus?

Answer 36

This hair replaces Lanugo. It is a short thin and light color hair that can be found on the back of the hand for example.

Question 37

Where can you find Terminal hair?

Answer 37

Head, scalp and eyebrows, nasal passage etc. Any other hair. Produced by the actions of testosterone.

Question 38

What are the functions of hair?

Answer 38

``` Thermoregulation Partial warrior to UV-rays Sexual attraction Sensation Protection (eyelashes and nasal hair, eyebrows as well) ```

Question 39

What are the arrector pili muscles?

Answer 39

They consist of smooth muscle fibres attached to papillary region of the dermis and hair bulb. React to fight or flight response or cold environment. It can also induce sebum release from sebaceous glands, usually during fight or flight to make hair and skin more slippery.

Question 40

What are the different mechanoreceptors. Explain what they do.

Answer 40

End bulbs (thermoreceptor) Free nerve endings (pain register) Tactile discs (touch, pressure and texture) Meissner corpuscle (tapping and flicker) Pacinian corpuscle (vibration) Ruffini's corpuscle (join movements and tissue stretch) Root hair plexus (vibrations in the hair shaft)

Question 41

What is the structure of nails?

Answer 41

Consists solely of alpha keratin

Question 42

What are the functions of nails?

Answer 42

Protection of distal phalanges. Enhances precise delicate movements Enhancing sensitivity of fingertip Enabling extended precision grip (pulling out a splinter e.g.)

Question 43

How does the nail relate to the length of the phalanx?

Answer 43

The growth rate of the nail correlates to the length of the phalanx.

Question 44

As a summary: What are the functions of the skin?

Answer 44

``` Protection and repair Thermoregulation Lubrication Storage (adipose tissue in hypodermis) Vitamin D synthesis Absorption Aesthetics Sensation ```