COM1 Cytology week 3

Question 1

What 2 alternative names is the skin also known as

Answer 1

• integument
  -cutaneous

Question 2

Name the layers of the skin+ explain characteristics+ contents if any

Answer 2

• Epidermis-Epithelial layer of ectodermal origin
  -Dermis-connective tissue layer of mesodermal origin
  -Hypodermis- loose connective tissue containing adipocytes

Question 3

What does Epidermal Derivatives in skin include

Answer 3

Hair, nails,sebaceous glands and sweat glands

Question 4

Give characterisitc of the skin

Answer 4

• It is elastic , it can expand and self renew
  -Heals rapidly

Question 5

Name the 5 functions of the skin

Answer 5

-Protective functions
-Sensory functions
-Thermoregulatroy functions
-Metabolic functions
-Sexual signlaing

Question 6

Explain the protective function of the skin- 4

Answer 6

• Acts as a barrier and shields against heat, pathogens
  -Allows passage of lipophilic drugs
  -UV protection
  -Immune defenese

Question 7

Explain the sensory function of the skin

Answer 7

-Receptors monitor enviornment and help in touch interaction

Question 8

Explain the thermoregulatory function of the skin

Answer 8

Maintains body temperature via
-Insulation
-heat loss

Question 9

Explain the metabolic function of the skin
-what it produces
-what it excretes
-what it stores

Answer 9

• Produces vitamin D3
  -Excretes electrolytes via sweat
  -Stores fat for energy in hypodermis

Question 10

Explain the sexual signaling function of the skin+ wht contributes to sexual attraction

Answer 10

-Skin traits acts as health indicators
-Pheromones from apocrine glands contribute to sexual attraction

Question 11

Name the tissue type the epidermis contains

Answer 11

Stratified squamos keratinized epithelium

Question 12

Name the main cell types in the epidermis

Answer 12

Keratinocytes

Question 13

Name other cell types in the epidermis + function

Answer 13

-Melancoytes- Produce melanin
-Langerhans cells- Antgen-presenting imune cells
-Merkel cells-Tactile epithelial cells for sensations

Question 14

Where is the epidermis located

Answer 14

• Outermost layer of the skin

Question 15

Name the layers of the epidermis from top to bottom + THEIR ALTERNATICE NAMES

Answer 15

• Stratum corneum-cornified layer
  -Stratum lucidum- has none
  -Stratum granulosum- granular layer
  -stratum spinosum- spinous layer
  -Stratum basale- basal layer

Question 16

Explain the stratumn corneum layer of epidermis
-what its made up of
-Explain characteristics of the cells+filled with
-What does keratohyaline granules provide
-What do desmosomes + lipids form

Answer 16

• 15-20 layers of fully keratinised cells
  -Cells are squamos,dead,fillwd with keratin
  -Provide filaggrin+ structural proteins
  -Desmosomes and lipids form tigh barriers

Question 17

Give the function of stratum corneum

Answer 17

• Mechanical protection
  -barrier function

Question 18

Explain the stratum lucidum layer of the epidermis:
-What is made up of/structure
-What structures are absent
-What cytoplasm is filled with
-What it is held togeher by

Answer 18

• Thin tranlucent layer of flattened keratinocytes
  -Nuclei and organelles are absent
  -Cytoplasm filled with packed keratin filaments in electron dense matrix
  -Held together by desmosomes

Question 19

What is the function of the stratum lucidum

Answer 19

-Extra barrier in thick skin

Question 20

Explain the structue of stratum granulosum
-Its structure
-Name 2 key feeatures it contains+structure
+ what the last one forms

Answer 20

-3-5 layers of flattened cells undergoing keratinization
-Keratohyaline granules : non membrane bound basophilic granules- contain filaggrin + proteins
-Lamellar granules: Lipid-filled vesicles- forms lipid rich impermeable barrier

Question 21

What is the function of the stratum granulosum

Answer 21

Forms the waterproof barrer in the skin

Question 22

Explain the structure of the stratum spinosum
+ the cells it contains and when they active
+explain its apperance and cause
+where is it thicker

Answer 22

• Thiclest layer
  -cells: Polyhedral, central nuclei active in keratin synthesis
  -Shiny apperance due to desomosmal connection and cell shrinkage
  -Thicler in areas subject to friction

Question 23

wHAT IS the function of stratum spinosum

Answer 23

-Keratin production

Question 24

Explain the stratum basale
+ the attachments

Answer 24

-Single layer of cuboidal/columnar basophilic cells
-Attachments:
hemidesmosomes- to basal lamina
desmosomes- between adjacent cells

Question 25

What are the 2 function of stratum basal

Answer 25

Intense mitotic acitivy source of new keratinocytes

Question 26

What is total skin thickness

Answer 26

Epidermis+ dermis

Question 27

Which epidermis layer is only in thick skin

Answer 27

stratum lucidum

Question 28

What is the thickest layer of the epidermis

Answer 28

Stratum spinousm

Question 29

What is the main function of melanocytes- what do they produce from what

Answer 29

Melanin pigments form tyrosine via enzyme tyrosinase

Question 30

Name the types of melanin + characteristic

Answer 30

- Eumelanin: brown/black pigment -Pheomelanin: Red/yellow pigment

Question 31

Eplain how Melanocytes function in UV protection starting with melanin

Answer 31

Melanin is transferred from melanocytes to keratinocytes. In keratinocytes, melanin forms a supranuclear cap over the nucleus. This absorbs and scatters UV radiation, protecting the DNA from mutagenic and ionizing effects.

Question 32

What forms the Epidermal-melanin unit

Answer 32

1 melanocytes + 5-10 keratincoytes

Question 33

What does the epidermal melanin unit allow

Answer 33

-Efficent melanin transfer -Protection over a broad ares of skin

Question 34

Name the 2 processes that occur in UV Radiation ( tanning)

Answer 34

- Immediate darkening -Delayed tanning

Question 35

Explain what happens in the 2 step process in uv radiation(Tanning)

Answer 35

Immediate darkening: Preexisting melanin is darkened by UV Delayed tanning: UV-exposed keratinocytes secrete paracrine factors that stimulate melanocytes to synthesize more melanin.

Question 36

Which populaion have more melanin?: -Equatiorial or northern populations

Answer 36

Equatorial populations

Question 37

Explain why equatorial populations have darker skin

Answer 37

Melanocytes are more active → more melanin, giving darker skin to protect from intense UV.

Question 38

Explain why nothern populations have less melanin and wht this allows

Answer 38

Genetic polymorphisms → less melanin → allow more UV to penetrate for vitamin D₃ synthesis in low-light environments.

Question 39

Where is langerhans cells found primarily in

Answer 39

Stratum spinosum of the epidermis

Question 40

What are langerhans derived from

Answer 40

Monocytes

Question 41

What is the function of Langerhan cells 3

Answer 41

- They are antigen present cells of the adaptive immune system -Binds,process and present antigens to the T lymphocytes -Trigger immune responses

Question 42

In immunity, what does Langerhans work alongside and why

Answer 42

Work alongside Epidermal lymphocytes and dermal APCs to: - Dectect and present antigens -Act as an immune defense network in the skin

Question 43

What structure is a critical component of the skins adative immunity system

Answer 43

- Langerhans

Question 44

Where are Merkel cells located

Answer 44

In the stratum basale of both thick and thin skin

Question 45

Where do Merkel cells arise from

Answer 45

- The same stem cells as keratincoytes

Question 46

What is the function of merkel cells

Answer 46

- They are Specialised mechanoreceptors fo gentle/light touch -Have low activation threshold

Question 47

What do merkel cells contain

Answer 47

- Dense-core granules near the basolateral membrane

Question 48

What do merkel cells form

Answer 48

Synaptic connections with unmyelinated afferent nerve fibers

Question 49

On stimulation what do merkel cells release

Answer 49

Neurotransmitters

Question 50

What structures contain no/very few melanosomes

Answer 50

Merkel cells

Question 51

What is the Dermis

Answer 51

Layer of connetive tissue beneath the dermis

Question 52

What does the Dermis bind the epidermis to

Answer 52

Subcutaneous tissue

Question 53

What does the dermis have on its surface

Answer 53

dermal papillae

Question 54

Name the layers of the dermis

Answer 54

Papillary layer -superficial Reticular layer-deep

Question 55

Explain the Papillary layer- superfcial of the dermis - Characteristic -What it contains -What it forms

Answer 55

- Loose connective tissue -Contains type 1, 3 and 7 collagen ,fibroblasts, mast cells, dendritic cells and leukocytes -Forms dermal papillae

Question 56

Explain the reticular layer of the Dermis - Characteristic -What it contains -What its rich in

Answer 56

- Dense irregular connective tissue -Contains type 1 collagen bundles and elastic fibers -Ruch in proteoglycan

Question 57

Name the 3 different vascular supply for the dermis+ where they locted

Answer 57

- Microvacular subpapillary plexus- between papillary and reticular layers -Deep vascular plexus- near dermis-subcutaneous -Thermoregulation

Question 58

Where does the lymphatc vesses originate from in the dermis

Answer 58

Dermal papillae

Question 59

Explain the subcutaneous tissue: -Characteristic -What it contains -What does it bind skin to

Answer 59

-Loose connective tissue -Contains adipocytes -binds skin loosely to underlying organs

Question 60

Name a characterstic of the subcutaneous tissue blood supply

Answer 60

High vascularized

Question 61

What is friction blisters caused by

Answer 61

Excessive rubbing

Question 62

What does friction blisters result in

Answer 62

Lymph filled spaces between the epidermis and dermis

Question 63

What is the cause of corns and calluses

Answer 63

- Continues rubbing/pressure

Question 64

What does corns/calluses lead to

Answer 64

Thickening and hardening of the outer cornified epidermis

Question 65

What is psoriasis

Answer 65

Chronic skin condition

Question 66

What does psoriasis lead to

Answer 66

-Thickened epidermis -Increases keratinization and shedding -Inflammation which causes : irritation, scailing redness

Question 67

What is psorasis caused by

Answer 67

Overactive T lymphocyte trigerring an autoimmune reaction