Skin Flashcards
What is alopecia areata?
Autoimmune hair loss.
What is vitiligo
Autoimmune depigmentation (melanocytes destruction)
What causes wrinkles?
Damage to collagen and elastin by UV
What cancers can be caused by UV?
Basal cell carcinoma and malignant melanoma.
What are the four layers of the epidermis?
Basal layer (stratum basale) Prickle cell layer (stratum spinosum) Granular layer (stratum granulosum) Horny layer (stratum corneum)
Where do keratinocytes undergo mitosis?
Basal layer.
What are keratins?
Heterodimeric fibrous proteins.
Why does the prickle cell layer appear the way it does?
Intercellular junctions - desmosomes
What occurs in the granular layer?
Cells lose their plasma membrane and start to differentiate into corneocytes.
What is synthesised by cells in the prickle cell layer?
Keratins
What is present in the granular layer?
Keratohyalin granules (aggregations of: keratin; other proteins such as involucrin and filaggrin; enzymes that degrade phospholipid bilayer, and cross link proteins such filaggrin which aggregates keratin and involucrin which forms the corneocyte envelope)
What are langerhans cells?
Antigen presenting cells of bone marrow origin.
Mediate immune reactions such as contact dermatitis.
What are melanocytes?
Cells of neural crest origin.
Produce melanin (more melanin produced in darker skinned people)
Tips of dendritic processes phagocytosed by keratinocytes.
Where are melanocytes found?
At intervals in the basal layer of the epidermis.
Where are langerhans cells found?
The prickle cell layer.
What is psoriasis?
Common skin condition (2% of population)
Extreme proliferation of basal cell layer, thickening of prickle cell layer, excessive stratum corneum (scaling)
What is the purpose of interdigital ion between dermis and epidermis?
Increase surface area for which they are in contact, reduce the risk of blistering due to shearing.
What makes up the dermis? Classify the connective tissue.
Collagen (type 1) and elastin Ground substance - GAGs, proteoglycans, hyaluronic acid, water. Fibroblasts Mast cells Blood vessels Lymph vessels Nerves
What is a keloid?
Excessive scar tissue following wounding (mainly collagen synthesised by fibroblasts)
Describe the blood supply to the dermis:
Larger blood vessels lie in the deeper dermis, interconnecting vessels connect to smaller vessels (arterioles, venues and capillaries) in the superficial dermis.
What causes a port wine stain?
Congenital malformation of dermal blood vessels.
What do mast cells contain, and what is the effect of release in the tissues?
What is a possible effect of degranulation in sensitised individuals?
Histamine - increases permeability of blood vessels, oedema, can cause angio-oedema and urticaria
Heparin - anticoagulant
Chemoattractants - eosinophilic and neutrophilic.
The degranulation of mast cells can cause anaphylactic reactions.
What does a pilosebaceous unit consist of?
Hair sheath and hair shaft.
Arrector pili muscle
Sebaceous gland.
What do sebaceous glands secrete? Where are they larger in the adult?
Sebum.
The face.
How do sebaceous glands secrete?
Holocrine secretion
What is acne?
Abnormal differentiation of the ducts of sebaceous glands, they become obstructed.
Increased sebum production
Infection with normal skin bacteria.
Changes occur at puberty. Most common on the face.
What is hyperhidrosis?
Increased sweating - wet hands and wet malodorous feet.
What do apocrine sweat glands release, and how does this produce body odour?
Thick protein rich substance.
Digestion by cutaneous microbes produces body odour
What are the four main functions of skin?
Barrier.
Thermoregulation
Psychosexual communication
Sensation
What can disruption of the stratum corneum, meaning the skin cannot perform its function as a barrier, lead to?
Loss of fluid Loss of nutrients Loss of heat Loss of proteins Increased absorption of drugs
Name two pathologies that can affect sensation.
Diabetic sensory neuropathy
Leprosy
What two means of thermoregulation are employed by the skin?
Vascular thermoregulation
Thermoregulatory eccrine sweating
What is erythrodermic psoriasis?
A type of psoriasis - inability to vasoconstrict leads to redness, uncontrolled heat loss, shivering and hypothermia.
