Histology of the Skin

Question 1

What is the largest organ of the body?

Answer 1

Skin

Question 2

What percentage of body weight does the skin make?

Answer 2

15%

Question 3

What is the thickness range of skin?

Answer 3

1.5-5mm

Question 4

List the functions of the skin.

Answer 4

Protective 
- barrier against microbial organisms 
- against mechanical, chemical, osmotic, thermal, UV, radiation damage 
- immunological response 
Biomedical synthesize 
- vit D under influence of UVB
Homeostasis
- controlling body temp 
- sweating - sweat glands  
Major sensory organ 
- touch, temperature, pain

Question 5

What is the epidermis?

Answer 5

Self-renewing stratified epithelia tissue

Question 6

What is the predominant cell in the epidermis?

Answer 6

Keratinocytes

Question 7

List the other types of cells found in the epidermis.

Answer 7

Langerhans cells - immune function
Merkel cells - sensory nerve ending
Melanocytes - produce melanin pigment

Question 8

What mediates the turnover of keratinocytes?

Answer 8

Stem cell - basal layer

Question 9

Describe the renewal of keratinocytes.

Answer 9

Undergo continuous renewal throughout life

Question 10

List the layers of the epidermis.

Answer 10

Cornified layer (Stratum corneum)
Clear layer (Stratum lucidum) 
Granular layer (Stratum granulosum) 
Spinous/prickle cell layer (Stratum spinosum) 
Basal layer (Stratum basale)

Question 11

Where are the keratinocyte stem cells found?

Answer 11

Basal layer

Question 12

What shape are keratinocytes?

Answer 12

Columnar in shape

Question 13

What is the basal layer the site of?

Answer 13

Epidermal cellular proliferation

Question 14

What is the function of desmosomes?

Answer 14

Connect plasma membranes of basal keratinocytes

Question 15

Name the function of hemidesmosomes.

Answer 15

Connect basal keratinocytes to basal lamina.

Question 16

What does the basal layer cytoplasm consist of?

Answer 16

Melanosomes and keratin filament bundles (keratin tonofilaments)

Question 17

What are the basal keratinocytes in contact with?

Answer 17

Basal lamina (lamina lucida and lamina densa)

Question 18

What other cells are present in the basal layer?

Answer 18

Melanocytes
Langerhans cells
Merkel cells

Question 19

What does the prickle/spiny cells layer consist of?

Answer 19

Closely packed keratinocytes (connected to each other by desmosomes which provides tensile strength)

Question 20

What does the cytoplasm of the spiny cell layer consist of?

Answer 20

Melanosomes

Question 21

What cells are also present in the spiny layer?

Answer 21

Langerhans cells

NO MERKEL CELLS

Question 22

What does the granular layer consist of?

Answer 22

3-4 layers of flattened cells

Question 23

What happens to nuclei and organelles in the granular layer?

Answer 23

Become disintegrated

Question 24

What makes up the water barrier of the granular layer?

Answer 24

Densely stained keratocyte hyaline granules

Question 25

Describe what happens to the cytokeratin filament bundles in the granular layer.

Answer 25

Cytokeratin filament bundles become more compact

Question 26

What does the cornified layer consist of?

Answer 26

Closely packed/flattened cells/ corneocytes | Packed with keratin filaments

Question 27

What do the cells of the cornified layer lack?

Answer 27

Lack nucleus & membranous organelles

Question 28

List qualities of melanocytes.

Answer 28

Present at the basal lamina Produce melanin pigment Lack desmosome connections with keratinocytes Present hemidesmosomes connection with basal lamina

Question 29

Describe the characteristics of langerhans cells.

Answer 29

Immune function | Distributed in both basal and spiny layers

Question 30

List the qualities of merkel cells.

Answer 30

Present in basal lamina Sensory nerve ending (touch sensation) Has desmosomes connections to keratinocytes

Question 31

What is the dermis made up of?

Answer 31

Irregular, moderately dense CT Meshwork of collagen (tensile strength) and elastin (stretch/recoil) fibres Ground substance (glycosaminoglycans, glycoproteins and water)

Question 32

What does the dermis contain?

Answer 32

Fibroblasts, plasma cells, macrophages, blood vessels, nerves, lymphatics, epidermal appendages (hair, sweat galnds and sebaceous glands)

Question 33

Name the two regions of the dermis.

Answer 33

Reticular layer | Papillary layer

Question 34

Describe the differences between the papillary layer and reticular layer.

Answer 34

Papillary Layer - immediately next to the epidermis - can find rete ridges which interdigitate with rete pegs - predominantly consist of collagen type III and some elastic fibres - fine and loosely packed collagens - sensory receptors (Meissner's corpuscles) Reticular Layer - no proper boundary between papillary and reticular layer - absent - collagen type II with some elastin fibers - thick, irregular bundles of collage - sensory receptors (Pacinian corpuscles) - also present in hypodermis

Question 35

What is the hypodermis made up of?

Answer 35

``` Layer of connective tissue of variable thickness, deeper to dermis Mainly consists of adipose tissue Blood vessels (BV), nerves and lymphatics travel through it ```

Question 36

What is the function of the hypodermis?

Answer 36

Increase morbidity of skin | Adipose - thermal insulation, shock absorber, store metabolic energy

Question 37

Name the accessory structures & their function.

Answer 37

Hair - sensory/thermoregulation Sebaceous glands - produce sebum, epidermal barrier Sweat glands (apocrine, eccrine/regular) - thermoregulation

Question 38

Sweat glands (Eccrine)

Answer 38

Secretions from the secretory cells will be passed to the eccrine duct Duct is deeply stained

Question 39

What do the sensory receptors detect?

Answer 39

Touch Pressure Temp Pain

Question 40

Where are meissner corpuscles found?

Answer 40

Dermal papillae

Question 41

What is the function of the meissner corpuscles?

Answer 41

Rapidly adoptive mechanoreceptor | Sensitive to touch

Question 42

Where are Pacinian corpuscles found?

Answer 42

Deep in dermis & hypodermis

Question 43

List the functions of the Pacinian corpuscles and associated features.

Answer 43

Rapidly adapting mechanoreceptors Sensitive to pressure & vibration Has a capsule, intermediate zone and a central core Central core contains an axon terminal