skin and structure Flashcards

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1
Q

what is the epidermis and dermis of the skin in mammals

A

epidermis is the outer layer made of stratified cellular epithelium

dermis is beneath the epidermis and is made of connective tissue

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2
Q

how is the epidermis formed

A

ectoderm cells from a single layer or periderm. Gradual increase in layers of cells. Periderm cells case off

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3
Q

how is the dermis formed

A

formed from mesoderm below ectoderm

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4
Q

what are melanocytes

A

pigment producing cells from neural crest

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5
Q

what are the layers of the epidermal cells from outside in

A
keratin layer 
granular layer 
prickle cell layer 
basal layer 
dermis
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6
Q

what is the basal layer made of

A

one cell thick, small cuboidal, keratin, highly metabolically active

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7
Q

what is the prickle cell layer made of

A

large polyhedral cells, lots of desmosomes (connections), intermediate filaments (keratin) connect to desmosomes

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8
Q

what is the granular layer made of

A

2-3 layers of flatter cells, large keratohyalin granules (contain structural filaggrin and involucrin proteins), Leland bodies, high lipid content, origin of “cornfield envelope”, cell nuclei lost

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9
Q

what is the keratin layer made of

A

corneocytes (overlapping non nucleated cell remnants), insoluble cornfield envelope, 80% keratin and filaggrin, lamellar granules release lipid, tight waterproof barrier

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10
Q

what are melanocytes

A
  • basal layer and above
  • pigment producing dendritic cells
  • contains melanosomes
  • convert tyrosine to melanin pigment
  • form a protective cap over nucleus (melanin caps protect the nuclear DNA in basal cells)
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11
Q

what is Nelsons syndrome

A

Melanin stimulating hormone is produced in excess by the pituitary

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12
Q

what are langerhans cells

A

mesenchymal origin (bone marrow), prickle cell in epidermis, involved in the skin immune system (antigen presenting cells, pick up antigen in skin and circulate to lymph node via lymphatic system)

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13
Q

what are Merkel cells

A
  • basal
  • between keratinocytes and nerve fibres
  • mechanoreceptors
  • direct entry point to CNS to the dorsal route ganglion
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14
Q

what makes up a pilosebatious unit (hair follicle)

A
  • hair follicle (3 main segments = infundibulum, the isthmus and hair bulb)
  • hair shaft
  • arrestor pili muscle
  • sebaceous glands
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15
Q

what are the phases of growth of hair follicles

A

anagen - growing (3-7 years)
catagen - involuting (3-4 weeks)
telogen - resting (shedding phase)

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16
Q

what is the key role in epitehelial-mesenchymal interactions

A

Support, anchorage, adhesion, growth and differentiation of basal cells

Semi permeable membrane acting as barrier and filter

17
Q

what layers make up the demo-epithelial junction

A
  1. basal cells (keratinocytes)
  2. lamina lucida
  3. lamina densa
  4. sub-lamina densa zone
18
Q

what substances make up the dermis

A
  • ground substance
  • cells = mainly fibroblasts, macrophages, mast cells, lymphocytes, Langerhans cells
  • fibres = collagen and elastin
  • muscles, blood vessels, lymphatics, nerves
19
Q

what is angioma

A

benign group of blood vessels in the dermal tissue that are bumpy red on appearance

20
Q

what is the function of the lymphatic system

A
  • continual drainage of plasma proteins, extravasated cells and excess interstitial fluid
  • important immune functions = immune survalance by circulating lymphocytes and langerhans cells. Channeling of micro-organisms /toxins
21
Q

what is the nerve receptor for pressure and vibration

A

pressure receptor = Pacinian

vibration receptor = Meissners corpuscles

22
Q

what are the 3 types of skin glands

A

sebaceous
apocrine
eccrine

23
Q

what is the function of sebaceous glands

A
  • largest gland in face and chest
  • produces sebum
  • its function is to control moisture loss and protection from fungal infection
24
Q

what is the function of apocrine sweat gland

A
  • Found in the axillae, groin, eyelids, ears, mammary and perineal regions
  • Produces oily fluid and creates an odour after bacterial decomposition
25
Q

what is the function of eccrine sweat glands

A
  • found on the whole skin surface: palms, soles, forehead and axillae in particular
  • function is to cool by evaporation ie moisten palms
26
Q

what are the functions of the skin

A
  • barrier function
  • metabolism and detoxification
  • thermoregulation
  • immune defence
  • communication
  • sensory functions