Physiology Flashcards
What is the largest organ in the body?
Skin
What is the outermost layer of skin called?
Epidermis
Which type of epithelium makes up epidermis?
Stratified squamous epithelium
Which layer of skin is deep to epidermis?
Dermis
Which tissue type makes up dermis?
Connective tissue
Which germ layer forms epidermis?
Ectoderm (forms periderm)
Which germ layer forms dermis?
Mesoderm
In foetal skin development, which layers are formed after 16 weeks?
Keratin layer (corneum) granular layer (granulosum) Prickle cell layer (spinosum) Basal layer Dermis
Which cell makes up 95% of epidermis?
Keratinocytes
The basal layer of skin is highly metabolically active. True/False?
True
Lots of intermediate filaments
Name 3 other epidermal cells (other than keratinocytes)
Melanocytes
Langerhans cells
Merkel cells
Where do melanocytes derive from?
Neuronal cell crest
What are melanocytes? Which layer of skin are they found?
Pigment-producing dendtritic cells
Basal layer
Convert tyrosine to melanin pigment
What do melanocytes do?
Convert tyrosine to melanin pigment and load colour onto adjacent keratinocytes
Eumelanin is brown/red
Brown
Phaeomelanin is brown/red
Red
Which disease results due to loss of melanocytes?
Vitiligo
Where do Langerhans cells derive from?
Bone marrow
What are Langerhans cells? Which layer of skin are they found?
Antigen-presenting cells
Prickle cell layer
What are Merkel cells? Where are they found?
Mechanoreceptors that aid sensation
Between keratinocytes + nerve fibres
Found in basal layer
What are the 3 phases of growth of a hair follicle?
Anagen (growing)
Catagen (curve inwards)
Telogen (resting/going bald)
What is the dermo-epidermal junction (DEJ)?
The junction between the dermis and epidermis
List 2 key roles of the DEJ
Support, anchoring, adhesion and growth of epidermal cells
Semi-permeable membrane acts as a filter/barrier
Give an example of inherited skin fragility as a result of mutation to one of the proteins in the DEJ
Epidermolysis bullosa complex in young infants
Give an example of acquired skin fragility
Dermatitis herpetiformis
Bullous pemphigoid
What do fibroblasts in the dermis produce?
Procollagen (becomes collagen)
Elastin
The blood vessel supply to skin is greater than its metabolic need. True/False?
True
Which nerve receptors sense pressure in skin?
Pacinian corpuscles
Which nerve receptors sense vibration in skin?
Meissners corpuscles
What do free nerve endings provide sense for in skin?
Temperature
Pain
Which inherited condition arises due to overgrowth of nerve endings?
Neurofibromatosis
List the 3 main secretory glands in skin
Eccrine
Apocrine
Sebaceous
Eccrine glands secrete ?
Apocrine glands secrete ?
Sebaceous glands secrete ?
Eccrine glands secrete sweat
Apocrine glands secrete odourous fluid
Sebaceous glands secrete moisturiser
Which areas of the body have a high concn of sebaceous glands?
Head, neck and chest
What is the significance of the melanin cap on basal cells?
Absorbs UV rays to protect DNA in the cells’ nuclei
Which vitamin does skin metabolise?
Vitamin D
20% of thyroxine conversion to triiodothyronine (T4 to T3) is done in peripheral tissues such as skin. True/False?
False
80%!
20% in thyroid gland
Which cells help protect skin from UV rays?
Melanocytes
Ratio of melanocytes : basal cells = ?
1:10
Where is the papillary dermis found?
Uppermost layer of the dermis
What is the 5th layer of the epidermis in palm/soles called?
Stratum lucidium (between the corneum and granulosum)
What are precursors for keratinocytes?
Basal cells
What do keratinocytes do?
Create and store the protein keratin
What creates pigmentation in hair follicles?
Melanocytes above dermal papilla
What are the growth hormones for hair follicles?
Thyroxine
Androgens
What is nail body made from?
Packed dead keratinocytes
What is the dermis made from?
Two layers of connective tissue (collagen and elastin) containing
Blood/lymphatics
Nerves
What do pacinian receptors do?
Detect pressure
What do meissners receptors do?
Detect vibrations
What do sebaceous glands do?
Produce sebum for skin lubrication [+anti-infectious]
What are apocrine glands?
Hair follicle gland, produce oily fluid, gives sweat smell
What are eccrine glands?
Cover whole skin surface
For cooling by evaporation
Sympathetic cholinergic nerve supply
What does the skin act as a barrier to?
Physical (UV light)
chemical (allergens)
pathogens
What are the functions of the skin?
Barrier Metabolism Thermoregulation Immune defence Communication Sensory functions
What does the skin metabolise?
Vitamin D
Thyroid hormone metabolism
Where is vitamin D stored?
Liver
What is vitamin D converted to and where ?
Converted to 1, 25 dihydroxy-vtD3
In the kidney
Acanthosis?
Increased thickness of epidermis
Parakeratosis?
Persistence of nuclei in the keratin layer
The developmental growth pattern of skin follows….?
Blaschko’s lines
