Skin

Question 1

What are the four main functions of the skin?

Answer 1

Protection against water/infection/UV
Detect sensory stimuli
Thermoregulation (e.g sweat)
Prevent dehydration

Question 2

What are the three layers of the skin?

Answer 2

Epidermis, dermis and subcutis/hypodermis

Question 3

Are there blood vessels in epidermis?

Answer 3

No

Question 4

What sort of epithelium is epidermis?

Answer 4

Stratified squamous epithelium with keratinised upper layer

Question 5

What are the layers of the epidermis?

Answer 5

Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum.

Question 6

How are cells of the stratum basale attached to the basement membrane?

Answer 6

Hemidesmosomes

Question 7

What shape are the stratum basale ?

Answer 7

Cuboidal/columnar

Question 8

What cells are in the stratum basale?

Answer 8

Stem cells and melanocytes

Question 9

What happens to cells in the stratum basale?

Answer 9

Divide and differentiate to form keratinocytes

Question 10

What cells are in the stratum spinosum?

Answer 10

Prickle cells (keratin producing)

Question 11

What is highly expressed in the stratum spinosum

Answer 11

Keratin

Question 12

What do desmosomes interact with

Answer 12

Keratin filaments

Question 13

What do cells in the straum granulosum contain

Answer 13

Keratohyaline granules

Question 14

What happens when stratum granulosum die?

Answer 14

Contents of granules and tonofilamnets form cross linked keratin under keratinocyte membrane

Question 15

What is constantly happening to stratum corneum?

Answer 15

Shed and replaced by new keratinocytes from deeper layers which die forming keratin plates

Question 16

What is the turnover from basal layer to desquamated keratin

Answer 16

25 days in feet (large impact) 45 days for back

Question 17

In thick skin, which layer is thicker?

Answer 17

Stratum corneum

Question 18

What do keratohyaline granules consist of ?

Answer 18

Specialised linking proteins that cross link each other and keratin tonofilaments, when cells die they release contents allowing cross linking with keratin filaments, cornified layer

Question 19

What do keratinocytes become?

Answer 19

Corneocytes that make up the stratum corneum, after keratinoytes complete their differentiation programme, lose nucleus and cytoplasmic organelles.

Question 20

What cell junctions are present?

Answer 20

Tight junctions in upper layers to maintain barrier. Desmosomes and hemidesmosomes for structural integrity.

Question 21

What do melanocytes do in epidermis?

Answer 21

Synthesise melanin in granules (in basal layer)

Question 22

What happens to melanin in granules in melanocytes?

Answer 22

Advance along cytoplasmic processes into cytoplasm of basal and prickle cell keratinocytes, melanin passed into other cell via projections

Question 23

What causes albinism?

Answer 23

1) Tyrosinase catalyses formation of melanin in melanosome. Defects - albinism so non pigmented hair and skin.
2) May be deficincies of melanin granule transport (melanocytes are modified lysosomes so lysosomal protein trafficking abnornality)

Question 24

What do Langerhan’s cells do?

Answer 24

Dendritic cell, present phagocytosed antigenic material to lymphocytes

Question 25

Where are the langerhans cells found ?

Answer 25

All layers, especially the spinosum

Question 26

Where are Merkel cells?

Answer 26

Stratum basale

Question 27

What do Merkel cells do?

Answer 27

Sensory receptors in skin which synapse with peripheral nerve endings (can be grouped to form touch receptors)

Question 28

What are nails?

Answer 28

Hard plates of keratinised epithelium (keratin filled squames in layers), specialised corneum.

Question 29

Describe 2 skin appendages.

Answer 29

``` Pilosebaceous apparatus (i.e. hair folicle/shaft) Glands (eccrine and apocrine) ```

Question 30

What is the embryological origin of eccrine and apocrine glands

Answer 30

Ectoderm

Question 31

What are downgrowths of the epidermis?

Answer 31

Sweat glands and hair follicles (extend into the dermis)

Question 32

What does the hair shaft grow from?

Answer 32

Hair bulb

Question 33

What surrounds the hair shaft?

Answer 33

Hair follicle

Question 34

What does the hair bulb consist of?

Answer 34

Contains rapidly dividing epithelial cells and melanocytes and surrounds dermal papilla

Question 35

What muscle controls hair follicle and shaft?

Answer 35

Erector pilli muscles

Question 36

Describe blood vessels supplying hair follicle

Answer 36

Hair follicle supplied by blood vessels in dermal papilla + nerve endings

Question 37

Where are sebaceous glands found, what do they do?

Answer 37

Around follicle secrete sebum and moisturises hair. (holocrine secretion- cells diet and release contents)

Question 38

Whereabouts in skin are eccrine glands found?

Answer 38

Subcutis or secretory part in dermis

Question 39

What do eccrine glands do?

Answer 39

Secrete sweat for thermoregulation

Question 40

Describe nerve supply of eccrine glands

Answer 40

Cholinergic symp control of secretion of sweat

Question 41

Where are apocrine glands found?

Answer 41

Breasts, axillary, genital regions

Question 42

Describe nerve supply of apocrine glands

Answer 42

Adrenergic sympathetic control

Question 43

What is found in the dermis?

Answer 43

Blood vessels ,lymph, nerves ,epidermal appendages,

Question 44

What are 2 layers of dermis?

Answer 44

Superficial loose papillary dermis | Dense reticular dermis

Question 45

What is loose papillary dermis composed of?

Answer 45

Thin, loosely arranged collagen + elastin fibers with blood vessels and nerve endings

Question 46

What are dense reticular dermis composed of?

Answer 46

Thicker, denser layers of collagen, elastic fibres and blood vessels

Question 47

What are 2 plexues that supply skin, where are they found?

Answer 47

Cutaneous and subpapillary in dermis

Question 48

Where does subpapillary plexus extend to?

Answer 48

Papillary dermis to form capillaries near BM of epidermis

Question 49

What is subcutis layer made of?

Answer 49

Adipose tissue + network of vessels extending to form cutaneous plexus

Question 50

What leads cells to differentiate in the epidermis?

Answer 50

A calcium gradient, with the lowest concentration in the stratum basale and increasing concentrations until the outer stratum granulosum, where it reaches its maximum. Calcium concentration in the stratum corneum is very high in part because those relatively dry cells are not able to dissolve the ions.

Question 51

What is the most peripheral layer of living cells in the skin?

Answer 51

Stratum granulosum

Question 52

What cells are not found in the corneum?

Answer 52

Fibrobasts

Question 53

Non-ectodermal strucuture of the skin?

Answer 53

Erector pilli muscle (mesoderm)

Question 54

A cell/structure that cycles through proliferative, regressive and quiescent stages?

Answer 54

Hair bulb

Question 55

Where is melanin contained in melanocytes?

Answer 55

Their melanin is contained in melanosomes and premelanosomes

Question 56

Describe cell junctions in stratum spinosum

Answer 56

Desmosomes, that appear as spiky membrane projections on histology.