Skin Structure & Function

Question 1

What is the Epidermis, and what are its properties?

Answer 1

1. Outermost layer of skin
2. Avascular - lack of blood vessels
3. Acts as a protective barrier
4. Contains 4 main types of cells; Keratinocytes, Melanocytes, Langerhans and Merkel
5. Has 5 layers; Stratum corneum, Stratum lucidum, Stratum Granulosum, Stratum spinosum, Stratum basal.

Question 2

What are Melanocytes, and what are their properties?

Answer 2

1. Cells which produce Melanin, a protective skin darkening pigment
2. Protects against UV radiation
3. Located in the Stratum basal layer 4. Stimulates keratinocyte production, thickening the epidermis

Question 3

What are Langerhans, and what are their properties?

Answer 3

1. Dendritic cells located in the stratum spinosum
2. Alerts immune system of harmful substances
3. Highly specialised macrophages, take part in destruction of pathogens
4. Part of hypersensitivity and allergic reactions

Question 4

What are the five layers of the epidermis?

Answer 4

1. Stratum Corneum
2. Stratum Lucidum
3. Stratum Granulosum
4. Stratum Spinosum
5. Stratum Basal

Question 5

What are Keratinocytes, and what are their properties?

Answer 5

1. Cells which produce keratin
2. Forms a protective barrier resistant to physical and chemical damage
3. Held together by desmosomes

Question 6

What are properties of the Stratum basal layer?

Answer 6

1. Comprised mostly of keratinocytes
2. Also include melanocytes and merkel cells
3. Stem cells mitose to produce keratinocytes here, replacing corneocytes which have shed (in the stratum corneum layer)
4. The cells are attached to the dermo-epidermal junction by hemi desmosomes

Question 7

What are properties of the Stratum Spinosum layer?

Answer 7

1. Cells from the basal layer migrate upwards to this layer and change shape to polygonal.
2. Develop keratin filaments (tonofilaments)
3. Some tonofilaments project out of the cell desmosomes
4. These filaments fill with others and form intercelluar bridges to add resilience.

Question 8

What are Desmosomes?

Answer 8

1. Bridges between cells
2. Provide robust barrier against trauma, particularly shearing forces

3 Loss of adhesion could result in blistering diseases,

Question 9

What are properties of the Stratum Granulosum?

Answer 9

1. Cells migrate up to this level and begin to flatten out from their polygonal shapes
2. Cells begin to lose nuclei and organelles, undergoing programmed cell death
3. Granules of keratohyalin organise keratin into thick bundles, increasing strength

Question 10

What is filaggrin and why is it important?

Answer 10

1. it is a filament associated protein which binds to keratinocytes
2. They are important as they retain the water within keratinocytes

Question 11

What are properties of the Stratum Lucidum?

Answer 11

1. visible on soles, palmes, fingertips and anywhere with thick skin.
2. thin layer of dead keratinocytes.

Question 12

What are properties of the Stratum Corneum?

Answer 12

1. Uppermost layer, filled with Keratin and filaggrin
2. Cells change shape to hexagonal, and become cornified.

Question 13

What is Desquamation?

Answer 13

1. Essentially the shedding of the skin
2. Includes breaking the desomosome links between corneocytes
3. Can only function well in the presence of a well-hydrated Stratum corneum
4. Desquamation is abnormal in the absence of hydration, leading to thick and dry skin.

Question 14

What are properties of the dermis?

Answer 14

1. Cells - composed of mainly fibroplasts, but also contains lymphocytes, langerhans, macrophages and mast cells
2. • Fibres - 70% collagen, the protein which gives toughness and strength. Also contains Elastin, which makes the skin pliable

Question 15

What are the layers of the Dermis?

Answer 15

1. Papillary
2. Reticular

Question 16

What are the properties of the Papillary layer of the dermis?

Answer 16

1. Composed of loosely woven collagen
2. Contains most of the blood/lymphatic vessels
3. DERMAL PAPILLAE & EPIDERMAL RETE RIDGES connect dermis to the epidermis

Question 17

What are the properties of the Reticular layer of the Dermis?

Answer 17

1. Consists of dense irregular tissue
2. has Courser, horizontally running bundles of collagen
3. Covers underlying subcutaneous tissue

Question 18

What are Fibroplasts, and their properties?

Answer 18

1. Cells which are responsible for the synthesis and degradation of connective tissue proteins
2. Imperative for Tissue repair

Question 19

What are Mast Cells, and their properties?

Answer 19

1. Cells which release a variety of inflammatory mediators (e.g. histamine)
2. Are derived from Bone marrow

Question 20

What is Adipose tissue?

Answer 20

Connective tissue mainly consisting of fatty/adipose cells

Question 21

What is the Hypodermis, and its properties?

Answer 21

1. Consists of Adipose tissue
2. Insulates the body, and serves as an energy supply
3. Thickened over the heel and metatarsal heads
4. Acts as sealed chambers of fat
5. With mechanical forces, acts as a fluid cushion to absorb force of walking

Question 22

Which subsystem of the Nervous system concerns sensation/touch?

Answer 22

Somatosensory system

Question 23

Which Skin Receptor is stimulated by pressure and touch?

Answer 23

Mechanoreceptors

Question 24

Which skin receptor is stimulated by temperature changes?

Answer 24

Thermoreceptors

Question 25

Which skin receptor is stimulated by pain?

Answer 25

Nociceptors

Question 26

What are Merkel discs and their properties?

Answer 26

1. Mechanoreceptors distributed throughout the Epidermis 2. Disc-like structures on the terminal twigs of nerve branches 3. Attached to merkel cells 4. Sensetive to light touch and superficial pressure 5.

Question 27

What are pacinian corpuscles and their properties?

Answer 27

1. Mechanoreceptors located in deep layer of dermis 2. Detect deep pressure and touch and are responsible for Proprioception 3. Rapidly adaptive

Question 28

What are Meissners Corpuscles (Tactile) and their properties?

Answer 28

1. Mechanoreceptors situated in papillary layer of Dermis 2. Respond to touch/pressure 3. found in areas of high sensetivity (e.g arch of foot)

Question 29

How do Blood vessels prevent heat loss in cold conditions?

Answer 29

Shunt vessels dilate, meaning less blood flows through the capillaries near the skin surface, meaning less heat is lost through radiation in blood

Question 30

What are properties of Hair?

Answer 30

1. Composed primarily of Keratin 2. Follicles contain the muscle 'arrector pili' which contracts in response to emotion 3. hair follicles have associated glands (oil/sebacious)

Question 31

What are the function and properties of Sebacious glands?

Answer 31

1. Produces and releases sebum excreted through the hair follicle 2. Sebum protects the skin keeping it smooth and supple 3. Not present on Glaborous skin (palms or soles)

Question 32

Label all cells and epidermal layers

Answer 32

Question 33

What is this?

Answer 33

Sebacious Gland

Question 34

What are these?

Answer 34

Red - Pacinian Corpuscle Blue - Ruffini's Corpuscle Green - Meissner's Corpuscle

Question 35

Complete the labels

Answer 35