zkin

Question 1

What is happening to skin constantly

Answer 1

self renewing as sloughing off from surface of epidermis.

Question 2

Layers of skin

Answer 2

Epidermis
Dermis
Subcutis/hypodermis

Question 3

Functions of skin

Answer 3

• Protection against water, infection and sunlight
• Detection of sensory stimuli
• Thermoregulation (e.g. sweat to cool)
• Prevention of dehydration

Question 4

What is the epidermis

Answer 4

Epidermis is outer surface layer of skin, sweat glands and hair follicles are down growths of this layer

Question 5

Are there blood vessels in epidermis

Answer 5

No

Question 6

What type of epithelia is epidermis

Answer 6

stratified squamous epithelium

Question 7

Describe tough upper layer of epidermis with regards to keratin

Answer 7

tough keratinized upper layer, formed from keratin producing cells (keratinocytes) which die forming keratin plates (squames). Outermost layer of keratin constantly being shed and replaced by new keratinocytes from deeper layers

Question 8

Describe layers of epidermis

Answer 8

Stratum basale/basal layer
Stratum spinosum/pickle layer
Stratum granulosum/granular layer
Stratum lucidum
Stratum corneum

Question 9

Describe Stratum basale

Answer 9

• Cuboidal/columnar cells are attached to each other and underlying basement membrane by hemidesmosomes
• Layer contains stem cells and daughter cells that divide to produce keratinocytes
• basal layer contains scattered melanocytes (and hence melanin)

Question 10

Describe stratum spinosum

Answer 10

• Sits on basal layer
• formed from polyhedral cells with round central nuclei.
• High levels of keratin expression. - Intracellular bridges made of cytoplasmic projections connect these prickle cells. - Projections terminate as desmosomal junctions on cell surface between cells.

Question 11

Describe stratum granulosum

Answer 11

• High levels of keratin, (new synthesised reduced) cells contain many keratohyaline granules and keratinosomes
• In upper layers, cells become flattened and densely packed, with little cytosol.

Question 12

Role of keratohyaline granules

Answer 12

These appear dark, contain specialised linking proteins proteins that have sulphur rich amino acid (e.g. Cys) involved in crosslinking with each other and keratin tonofilaments in stratum corneum. When these cells die, release contents, permits cross linking with keratin filaments leads to cornified layer

Question 13

What are keratin tonofilaments

Answer 13

Tonofilaments found in all layers of epidermis, they link to desmosomes in stratum, spinosum and hemidesmosomes in stratum basale.

Question 14

What is stratum lucidum

Answer 14

Merges with upper layer of stratum granulosum, consists of flattened cells where organelle/nuclei not readily apparent

Question 15

What is stratum corneum

Answer 15

• tough keratinised uppermost layer, where keratin is formed from dead cells
• Layer is constantly shed and replaced by new keratinocytes from deeper layers which die, forming keratin plates (squames).

Question 16

Why is epidermis waterproof

Answer 16

In stratum corneum Glycophospholipids stick the dead flakes of cells together and are hydrophobic making layer waterproof

Question 17

Describe turnover of cells from basal layer to desquamated keratin in traumatised site

Answer 17

E.g. sole of feet, quicker

Question 18

Cornified layer much thicker in…

Answer 18

Thick skin

Question 19

What does thickness of cornified layer influence

Answer 19

Strength of epidermis

Question 20

Describe development of keratinocytes

Answer 20

Epidermal stem cells diff to become keratinocytes.

• these move and become part of stratum spinosum, granulosum and then corneum (become corneocytes)
• Corneocytes will eventually be shed off through desquamation as new ones come in

Question 21

Describe the cell junctions found in skin

Answer 21

• Tight junctions only occur in upper layers, so growth factors can diffuse to these apical layers.
• Cell-cell (desmosome) and cell basement membrane (hemidesmosome) attachments necessary for structural integrity of skin.

Question 22

What is junctional epidermolysis bullosa

Answer 22

hemidesmosome defects (due to integrin mutations) lead to skin blistering. Epidermis detaches from dermis so blister formation within the lamina lucida of the basement membrane zone

Question 23

What is pemphigus

Answer 23

is autoimmune condition, antibodies against desmoglein formed, damage desmosome so blistering of skin and mucous membrane

Question 24

What is Epidermolysis bullosa simplex

Answer 24

affecting the keratin genes.Therefore, there is a failure in keratinisation, which affects the integrity and the ability of the skin to resist mechanical stresses
So blisters at site of rubbing

Question 25

Describe 3 other cells in epidermis

Answer 25

Melanocytes Langerhan's cells Merkel cells

Question 26

What are melanocytes

Answer 26

In basal layer they synthesise melanin in melanosomes which advance along cytoplasmic processes into cytoplasm of basal and prickle cell keratinocytes (melanin released/passed into other cells via projections so entire epidermal cell layer pigmented).

Question 27

What is melanin

Answer 27

Pigment that colours skin and reduce damage caused by UV

Question 28

What is melanoma

Answer 28

: type of cancer that affects melanocytes. The primary cause of melanoma is ultraviolet light (UV) exposure which stimulates uncontrolled melanocyte expansion.

Question 29

What happens in albinism

Answer 29

: Tyrosinase catalyses formation of melanin in both types of melanosome. Defects in this pathway lead to albinism – non pigmented hair and skin OR with deficiencies in the transportation of melanin granules (melanosomes are modified lysosomes ), so defects in lysosomal protein trafficking

Question 30

What are langheran's cells

Answer 30

cells present phagocytosed antigenic material to lymphocytes. Found in all layers, especially prickle layer

Question 31

What happens to Langerhan's cells in autoimmune skin disorder/allergy

Answer 31

cytoplasmic processes increase SA of cell membrane | - more processes found in inflamed skin

Question 32

What are Merkel cells

Answer 32

epidermal basal layer, are sensory receptors in skin which synapse with peripheral nerve endings

Question 33

How are merkel cells found/arranged

Answer 33

Found as solitary cells or grouped together to form touch receptors where they are related to hair discs.

Question 34

Describe structure of hair

Answer 34

Hair is formed of organised keratin, hair follicle and shaft are controlled by erector pili muscles that allow hair to stand on end. Hair grows from hair follicles Hair shaft grows from hair bulb (epidermal structure) which contains rapidly dividing epithelial cells and melanocytes and surrounds dermal papilla (dermis)

Question 35

What are hair follicles

Answer 35

Invagination of epidermal tissue extending into dermis and subcutis

Question 36

What layer structure is hair bulb

Answer 36

Epidermal structure

Question 37

Which layer is dermal papilla

Answer 37

Dermis

Question 38

What do holocrine/sebaceous glands do

Answer 38

around follicle secrete sebum – mixture of lipids , waterproofs and moisturises hair.

Question 39

True of false, hair follicle well supplies by blood vessels and nerve endings

Answer 39

True

Question 40

2 types of glands

Answer 40

Eccrine and Apocrine

Question 41

Describe distribution of eccrine and apocrine glands

Answer 41

Eccrine: Everywhere Apocrine: breast, axillae, genital region

Question 42

Describe innervation that controls sweating

Answer 42

Cholinergic sympathetic control

Question 43

What do eccrine glands do

Answer 43

Secrete sweat - thermoregulation

Question 44

What layer of skin is eccrine gland

Answer 44

Dermis/superficial subcutis

Question 45

What do apocrine glands produce

Answer 45

Viscour milky secretion

Question 46

When are apocrine glands stimulated

Answer 46

Fight or flight

Question 47

Describe innervation of apocrine glands

Answer 47

Adrenergic sympathetic control (also sex hormones)

Question 48

Apocrine glands are downgrowths of..

Answer 48

dermis

Question 49

Describe dermis, what does it contain

Answer 49

Middle layer of skin, includes blood vessels, lymphatics, nerves and nerve endings, and epidermal appendages, embedded in a connective tissue stroma produced by fibroblasts

Question 50

2 layers of dermis

Answer 50

Upper layer/superficial loose papillary dermis | Dense reticular dermis

Question 51

Describe superficial loose papillary dermis

Answer 51

thin layer of loosely arranged collagen and elastin fibres, with capillary sized blood vessels, fine nerves and nerve endings.

Question 52

Describe dense reticular dermis

Answer 52

thicker layer containing dense bands of collagen, long thick elastic fibres running parallel to skin, and blood vessels , nerves, lymphatics supplying skin.

Question 53

Describe blood supply of skin, i.e. name 2 plexuses

Answer 53

Cutaneous and subpapillary plexus

Question 54

Where is cutaneous plexus found

Answer 54

Hypodermis/dermis junction

Question 55

Where is superficial/subpapillary plexus found

Answer 55

Upper dermis/superficial appendages

Question 56

Describe what happens to subpapillary plexus

Answer 56

Loops from superficial/subpapillary plexus extend upwards to papillary dermis to form capillaries near basement membrane of epidermis.

Question 57

How is thermoregulation achieved

Answer 57

Variations in blood flow within dermis | . Controlled by arteriovenous shunts e.g. glomus bodies (artery+vein anastomoses) within dermis

Question 58

What happens in psoriasis

Answer 58

abnormally excessive and rapid growth of the epidermal layer of the skin and scaling Basal cell proliferation regulated by signals from dermis and epidermis. These growth factors may be upregulated in psoriasis in premature maturation of keratinocytes and keratinocytes

Question 59

What happens in basal cell cancer

Answer 59

uncontrolled growths or lesions that arise in the skin’s basal cells, which line the deepest layer of the epidermis