Physiology Flashcards
What is the embryological origin of the layers of the skin?
epidermis= ectoderm dermis= mesoderm melanocytes= from pigment-producing cells in the neural crest
How will the layers of the skin look at 4 weeks?
periderm
basal layer
dermis
What is a scar?
a loss of appendages as there is connective tissue covering but nothing else
What is the epidermis?
stratified squamous epithelium which is made up of mostly keratinocytes containing keratin
What are the four layers of the epidermis?
Basal layer
Prickle cell
Granular layer
Keratin layer
What are the features of the basal layer?
- one cell thick
- loss of keratin
- highly metabolically active
What are the features of the prickle cell layer?
- larger cells
- lots of desmosomes
- intermediate filaments
What are the features of the granular layer?
- thinner
- less nuclei
- 2-3 layers
- filaggrin
- moist maker
What are the features of the keratin layer?
- insoluble waterproof
- cornfield envelope made of corneocytes
What is the epidermal turnover and what is it controlled by?
- the balance of cells in and out
- controlled by growth factors, cell death and hormones
What does HPV do?
it affects keratinocytes and warts are common in children due to deficient skin barrier
What is a digital artery?
an end artery in the feet and hands which has no collateral so there can be occlusion leading to infarction or amputation
What are the characteristics of superficial veins?
- small
- thin
- run in superficial fascia
- variable
- drain to deep
What are the characteristics of deep veins?
- large
- thick
- deep to deep fascia
- predictable
- run in neurovascular bundles
Where does the cephalic vein run?
- from the dorsal venous network
- up the lateral limb in deltopectoral groove
- drains into axillary vein
Where does the basilic vein run?
- from dorsal venous network
- rises on medial aspect of limb
- drains into brachial vein
What is the median cubital artery?
joins the basilic and the cephalic veins together but this can have variations eg M, H or Y shape
What are the names of the networks in the hand and the foot?
dorsal venous network= hand
dorsal venous arch= foot
Where does the great saphenous vein run?
- from dorsal venous arch
- up medial aspect
- drains into femoral vein at the femoral triangle
Where does the small saphenous vein run?
- from dorsal venous arch
- up posterior midline
- drains into popliteal vein in popliteal fossa
Are the deep veins bilateral or unilateral?
all deep veins are bilateral except the SVC and the IVC
What are vena comitantes?
these are veins next to arteries that are forced to pulse by the artery’s force which increases the venous return to the heart
What does ischaemia lead to?
- decreased arterial perfusion pressure
- increased venous pressure from the back pressure to the capillaries so there is decreased arterial flow
What are perforating veins?
they run at angles and have valves for backflow
What is superficial fascia?
loose connective tissue and fat which varies in depth
this contains superficial blood vessels
What is deep fascia?
tough sheet of dense connective tissue which is named according to body part
What are the largest sections of fascia?
fascia lata on the thigh
iliotibial tract down lateral leg
Where are the main groups of lymph nodes in the upper limb?
apical axillary
lateral axillary
cubital
Where are the main groups of lymph nodes in the lower limb?
superficial inguinal
deep inguinal
popliteal
What are the main epidermal cells?
keratinocytes are the main ones
others are melanocytes, langerhans cells and Merkel cells
What are the features of melanocytes?
- migrate from neural crest to the epidermis
- in basal layer below dendritic cells
- contain melanosomes which move to nearby keratinocytes via dendrites
- melanin absorbs light and melanin casts protect nuclear DNA in basal cells
What are the features of Langerhans?
- these are a type of dendritic cell
- they have a mesenchymal origin in the bone marrow
- they are in the prickle cell layer, dermis and lymph nodes
- they act as APCs and activate T cells
- BIRBECK granules are their distinguishing feature
What are the features of Merkel cells?
- these are basal cells that act as mechanoceptors
- cancer of these cells is rare but deadly
What are the phases of hair growth?
anagen= growing catagen= involuting telogen= resting
What are nails made up of?
specialised keratins and stem cells that are in the matrix of nails and differentiate to become flat
What is the dermis made of?
collagen for support and is made of fibroblasts
What does disrupted lymphatics lead to?
chronic lymphedema which is non-pitting
What nerves are in the dermis and what are the special ones?
- usually somatic sensory
- special receptors are Meissner’s (vibration) and Pascinian corpuscles (pressure)
What are the three types of skin glands and their features?
- Eccrine: palms and soles, keep cool, excess sweating
- Sebaceous: lubricated hair follicles, protect from fungus, largest glands, face and chest, cause of acne
- Apocrine: axilla and perineum, unclear role, odour after secretion
What role does the skin play in metabolism?
- vit D metabolism
- thyroid hormone metabolism
- defence against chemicals
What are the parts of hair?
- follicle which is an invagination of the epidermis
- central medulla with soft keratin
- papilla with vascular channels
- outer cortex with hard keratin
What are the parts of nail?
- plate sits on the bed
- matrix where cells divide and make keratin
- hyponychium where the free edge of the nail is secured
- cuticle is an extension of the skin fold
What are the types of intention wound healing?
- primary intention is suturing the wound
- secondary intention is leaving the wound to heal on its own
What are the features of keratinocytes?
- epidermal
- sense pathogens
- make AMPs that kill pathogens
- make cytokines and chemokines
What are the types of lymphocytes in each layer of the skin?
- CD8 are in the epidermis
- CD4 and CD8 are in the dermis
What do plamacytoid cells do?
are in the dermis and make IFNalpha and are in diseased skin
What do MHC class 1 and 2 do?
- MHC class 1: present antigens to cytotoxic T cells and are present on almost all cells
- MHC class 2: found on APCs and present to T helper cells
What are the factors affecting skin immune response?
- organ transplant: immunosuppression
- sunlight: immunosuppression
- ageing: decrease ability to detect cancer and to see antigen
What cells do vitamin D metabolism?
keratinocytes
