Flashcards in ToB 10 Skin Deck (84)
What are the 3 main variations in the macroscopic structure of human skin?
What are the 4 main factors which influence the presence of hair on skin?
1) Site (palm vs back of hand)
What are the 2 main factors which influence the presence of laxity/wrinkling of skin?
What are the 3 main factors which influence the presence of colour in skin?
What is the name given to the condition caused by autoimmune depigmentation?
What is vitiligo?
An autoimmune condition that results in depigmentation of skin
What is the name given to the condition caused by autoimmune hair loss?
What is Alopecia areata?
An autoimmune condition that results in hair loss
What is the main cause of skin ageing/wrinkling?
UV-induced damage to dermal collagen and elastin
Compare the thickness' of the dermis vs epidermis:
The dermis is much thicker than the epidermis.
Give a main use of animal dermis:
How many layers male up the epidermis?
Name the 4 layers of the epidermis, in order from outer layer to inner:
1) Stratum corneum
2) Stratum granulosum / granular layer
3) Stratum spinosum / Prickle-cell layer
4) Basal layer
Name the outer-most layer of the epidermis:
Name the layer of the epidermis inbetween the stratum corneum and stratum spinosum:
Name the inner-most layer of the epidermis:
What is another name of the stratum spinosum?
Describe the location of the stratum spinosum:
Above the basal layer, below the stratum granulosum.
What lies beneath the basal layer of the epidermis?
Why are the epidermis and dermis interdigitated?
To help prevent the shearing of layers
What is the main cell type within the epidermis?
In which layer of the epidermis does keratinocyte mitosis occur?
Mainly in basal layer
In which layer of the epidermis does terminal differentiation of the keratinocytes begin?
Prickle cell layer / Stratum spinosum
What do Keratinocytes synthesise?
What are Keratins?
Heterodimeric fibrous proteins which give strength to structures
What gives the epidermis its strength?
Keratin, synthesised by the keratinocytes
What gives the 'prickle cell layer' its name?
The cells in this layer are joined by many prickle-like desmosomes, which are easily viewed at high power microscopy.
What changes occur as cells migrate through the granular layer?
- Keratinocytes ose their phosholipid bilayer plasma membrane
- Keratinocytes begin differentiating into corneocytes
What is the name of the main cells of the stratum corneum?
What are keratohyalin granules, and where are they located?
- Other fibrous proteins
- Enzymes which degrade the phospholipid bilayer
- Enxymes which cross-link protein
Found in granular layer of epidermis
Why does the granular layer of the epidermis appear darker than the other layers?
It contains keratohyalin granules, which are dense aggregations
What is the transit time of a keratinocyte from the basal layer to stratum corneum?
30-40 days / 4-6 weeks
Name 2 types of cells which are present in the epidermis, other than keratinocytes:
2) Langerhans cells
What type of cells are melanocytes, and what is their origin?
Dendritic cells, from neural crest origin
Where and how often are melanocytes present in the epidermis?
Present in the basal layer of the epidermis, at a constant interval of 1 in 8 cells
What is the main pigment which gives skin its colour?
What is the function of melanocytes?
To produce Melanin
What results in the different skin colours of some people?
Their melanocytes in their epidermis produce more or less melanin. More melanin = darker skin
What type of cells are Langerhans cells. and what is their origin?
Dendritic cells, from bone marrow
Where are Langerhans cells located in the epidermis?
Scattered throughout prickle-cell layer / stratum spinosum
What is the main function of Langerhans cells?
To mediate immune reactions, as they are professional antigen-presenting cells, allowing them to present antigens to T lymphocytes.
Which type of cell would be responsible for a dermatitis allergic reaction?
How does melanin protect your epidermal cells?
It lies on top of the nucleus, on the sunny side, protecting the genetic material of the cell and reducing mutations occurring due to UV.
What are 3 unusual factors of palmar skin, compared to other skin areas?
1) Thick stratum corneum
2) Very thick prickle cell layer
3) No hair follicles
What is psoriasis?
A skin disorder characterised by extreme proliferation of the epidermal basal layer, with increased differentiation leading to thickening of prickle cell layer and stratum corneum, causing excessive scaling.
In which skin disorder is the life span of a keratinocyte reduced from 4-6 weeks, to 1 week?
How does Psoriasis affect the life span of a keratinocyte?
Reduced from 4-6 weeks, to 1 week
What is the cause of Psoriasis?
Cause unknown, but is a genetic disorder, and is a type of autoimmune disease.
What type of cells mediate 'allergic contact dermatitis'?
How do Langerhans cells mediate allergic contact dermatitis?
Langerhans cells are professional antigen-presenting cells, presenting them to T lymphocytes, causing immune response
Name 4 disorders of the epidermis:
2) Malignant melanoma
3) Allergic contact dermatitis
What happens to melanocytes with age?
Melanocytes in hair follicles often stop functioning with age, but not in the epidermis
What is a malignant melanoma?
An aggressive, invasive tumour of melanocytes
What signs may indicate that a mole has become a melanoma?
- Change in shape - creating an irregular edge
- Getting bigger
- Change in colour - getting darker or multi-shaded
- Loss of symmetry
- Look inflamed
What stain best visualises the epidermal basement membrane?
Periodic Acid-Schiff (PAS)
What is associated with a good prognosis in melanoma?
The retention of the malignant melanocytes ABOVE the epidermal basement membrane.
The extracellular matrix of the dermis is synthesised by which cells?
Which 2 types of fibres make up the bulk of the dermis?
1) Collagen fibres
2) Elastin fibres
What is 'Solar elastosis'?
Damage to elastin fibres due to excessive UV exposure
What are scars mainly made from?
What is keloid scarring?
Excessive scar production, which become lumpy and may grow larger than the wound
What type of blood vessels are present in the dermis?
Mainly capillaries, but also small venules and arterioles in the superficial dermis. Larger blood vessels are present in deeper dermis.
What causes vascular birthmarks?
Malformation of dermal blood vessels
What is characteristic about a mast cell when viewed at high power (and stained)?
Contains many cytoplasmic granules
What do the granules within a mast cell contain?
Why is it important that mast cells are concentrated around the dermal blood vessels?
When activated, ie by immediate allergic reactions, can release histamine directly into bloodstream, leading to inflammation and oedema (immune response)
What is the affect of histamine release into the dermal blood vessels?
Increased blood vessel permeability, and leakage of plasma into extravascular sites, causing oedema.
What is the name given to oedema of the skin?
Oedema in epidermis = Urticaria
Oedema in dermis = Angio-oedema
What is the difference between Urticaria and Angio-oedema?
Urticaria is oedema within the epidermis, whereas angio-oedema is oedema within the dermis.
What makes up a pilosebaceous unit?
- Hair shaft
- Hair follicle
- Arrector pilli muscle
- Sebaceous gland
What can become obstructed, resulting in acne?
Sebaceous duct associated with a hair follicle.
What type of secretion is used by the sebaceous glands associated with a hair follicle?
On what part of the body are sebaceous glands most abundant?
What 3 factors result in acne?
1) Obstruction of sebaceous duct
2) Increased sebum production
3) Infection (with normally harmless skin bacteria)
What is the shape of an eccrine sweat gland?
Coiled gland, whose duct stretches out to reach the surface of the epithelium
What is 'hyperhidrosis'?
Increased or excessive sweating, without the presence of normal triggers such as hot weather, exercise or anxiety
What are the differences between eccrine and apocrine sweat glands?
- Eccrine sweat glands are present all over body, but apocrine only in axillae, genital and submammary areas
- Eccrine glands reach deep into dermis, and secrete onto a hair follicle, whereas apocrine are more superficial, secreting onto the epidermis
- Apocrine sweat contains higher protein content, which can be broken down by bacteria, producing BO
Which type of sweat glands are associated with BO, and why?
Apocrine sweat glands, as produce protein-rich sweat which is broken down by bacteria, releasing BO
Which layer of the skin plays the main part in providing a barrier function?
Poor skin barrier function leads to:
- Loss of fluid, protein, other nutrients
- Loss of heat
- Excessive absorption of exogenous agents (potentially harmful)
How does leprosy affect sensation?
The infection starts by damaging the small nerves on the surface of the skin, leading to loss of sensation, so cuts and burns are not detected, leading to sores/ulcers/infection etc.
Which 2 regulated pathways are vital in the maintenance of body temperature?
1) Vascular thermoregulation
2) Thermoregulatory eccrine sweating
How can vascular thermoregulation conserve or lose heat?
- Vasoconstriction of skin blood vessels leads to heat conservation
- Vasodilation of skin blood vessels leads to heat loss