Skin Histology

Question 1

What are the main functions of the skin?

Answer 1

Protection
Sensation perception
Thermoregulation
Metabolism

Question 2

What are the 3 main layers of the skin?

Answer 2

Epidermis
Dermis
Hypodermis/subcutaneous layer

Question 3

What are the layers of the skin epidermis?

Answer 3

Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basalis

Question 4

What is the most superficial layer of the skin epidermis?

Answer 4

Stratum corneum

Question 5

What is the deepest layer of the skin epidermis?

Answer 5

Stratum basalis

Question 6

What does the stratum corneum consist of?

Answer 6

5-50 layers of dead keratinocytes that continuously slough off and regenerate very 4-6 weeks

Question 7

What does the stratum lucidum consist of?

Answer 7

Dead cells that do not contain any nuclei or organelle

-found on palms and soles of feet

Question 8

What does the stratum granulosum consist of?

Answer 8

3-5 layers containing granules. These granules contain a lipid rich secretion which acts as a water sealent

Question 9

What does the stratum spinulosum consist of?

Answer 9

Full of keratinocytes with a spiny appearence. Have lots of desmosomes which anchor the cells to one another (improves strength)

Question 10

What does the stratum basalis consist of?

Answer 10

Mitotically active tall cuboidal stem cells

Question 11

What are the different cell types in the epidermis of the skin?

Answer 11

Keratinocytes
Melanocytes
Langerhans cells
Merkel cells

Question 12

What are melanocytes?

Answer 12

• located in stratum basale
• responsible for skin pigmentation
• melanosomes in the cell make melanin in the cytoplasm which is then transferred into the cytoplasm of stratum spinulosum keratinocytes

Question 13

What are langerhans cells?

Answer 13

• present in all layers but most prominent in the stratum spinosum
• they are tissue resident dendritic cells of the skin

Question 14

What are merkel cells?

Answer 14

• located in the stratum basale
• is a nerve cell that forms a merkel disc
• they are mechanoreceptors that perceives light touch and helps discriminate shapes and textures

Question 15

What is the dermo-epidermal junction?

Answer 15

The junction between the epidermis and dermis

Question 16

What marks the dermo-epidermal junction of the skin?

Answer 16

Marked by downwards folds of epidermis known as rete ridges

Question 17

What are hemidesmosomes and what is their function?

Answer 17

Small stud like structures found in keratinocytes of the epidermis of the skin
-facilitate the stable adhesion of basal epithelial cells to the underlying basement membrane

Question 18

What are rete ridges and what are their function?

Answer 18

They are downward folds of epidermis at the dermo-epidermal junction
-increase surface area of the junction, enhancng adhesion. Less chance the epidermis slides off

Question 19

What are the 2 layers of the dermis of the skin?

Answer 19

Papillary layer- loose connective tissue

Reticular layer- dense irregular connective tissue

Question 20

What appendages sit in the dermis of the skin?

Answer 20

Pilosebaceous unit

Sweat glands

Question 21

What is a pilosebaceous unit?

Answer 21

A unit containing the hair shaft, hair follicle, sebaceous gland and the erector pilli muscle

Question 22

Describe the structures in a pilosebaceous unit?

Answer 22

• Hair- which is a highly modified keritinised structure
• Growth occurs in the hair follicle
• Arector pilli muscles sits in papillary layer- sympathetic innervation can cause pilo-erection by cold or fear
• Each follicle has a sebaceous gland which secretes sebum that acts as waterproofing and a lubricant for the skin

Question 23

What are the 2 different types of sweat glands?

Answer 23

Merocrine

Apocrine

Question 24

What is merocrine sweat?

Answer 24

Main type of sweat

• a watery fluid that aids in thermoregulation
• drains directly to external environment through a pore

Question 25

What is apocrine sweat?

Answer 25

Found in axilla and groin

• a more viscous secretion
• drain via an opening of the hair follicles as it emerges from the skin

Question 26

What are the 4 main types of mechanoreceptors in the skin?

Answer 26

Merkels discs
Meissner’s corpuscle
Ruffini’s ending
Pacinian corpuscle

Question 27

What is the difference between fast and slow reacting nerve structures in the skin?

Answer 27

Rapidly adapting- activated when stimulus first encoutered, but fall silent if stimulent remians present
Slowly adapting- keep responding to a continuously present stimulus

Question 28

What are the properties of merkel’s discs?

Answer 28

Slowly adapting

Small receptive fields

Question 29

What are the properties of Meissner’s corpuscle?

Answer 29

Rapidly adapting

Small receptive field

Question 30

What are the properties of Ruffini’s endings?

Answer 30

Slowly adapting

Large receptive fields

Question 31

What are the properties of Pacinian corpuscle?

Answer 31

Rapidly adapting

Large receptive fields

Question 32

What are Krause’s end bulbs?

Answer 32

Type of thermoreceptor that detects cold

-As well as receptors present on free nerve endings that detect temp changes

Question 33

Where are the blood vessles in the skin?

Answer 33

Blood vessels are in the dermis, that are directed towards the epidermis but dont penetrate

Question 34

How can blood take different paths in the skin?

Answer 34

There are many arteriovenous anastomoses

• which are short vessel segment/loops allowing for the bypass of capilarries
• when blood hot it can flow into most superficial segement to be cooled by evaporation of sweat on the skin
• when temp is lower it can bypass the most superficial segment so it is not cooled and heat is retained

Question 35

What is the hypodermis mainly made up of?

Answer 35

Mainly adipose and areolar tissue