Structure and Function of Skin Flashcards by S B

what are the layers of skin and type of cells do they consist of

1) epidermis - outer layer
- stratified cellular epithelium

2) dermis - beneath epidermis
- connective tissue

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how does the epidermis form (embryology)

ectoderm cells form single layer periderm
gradual increase in layers of cells
periderm cells cast of

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where does dermis come from (embryology)

formed from mesoderm below ectoderm

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what are melanocytes and where do they migrate to

pigment producing dendritic cells

neural crest

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what happens around 7-10 days in early foetal development

gastrulation

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what layers are there after 4 weeks development

Periderm
Basal layer
Dermis (corium)

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what layers are there at 16 weeks development

Keratin layer
Granular layer
Prickle cell layer
Basal layer
Dermis

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what are Blaschko’s lines

developmental growth pattern of skin

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true or false - blaschko’s lines follow vessels

false

they do not

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what separates the epidermis from the dermis

the dermo-epidermal junction

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what are the cells of epidermis

keratinocytes (95%)
melanocytes
langerhans cells
merkel cells

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what are the layers of the epidermis - top to bottom

keratin layer
granular layer
prickle cell layer
basal layer

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what causes the hair on you arms to stand up

arrector pilli muscle

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what regulates epidermal turnover

growth factor
cell death
hormones

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what are diseases where the epidermal turnover is affected

skin cancer

psoriasis

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where do keratinocytes migrate from and how long does it take

basement membrane

takes 28 days from bottom to top

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description of basal layer

Usually one cell thick
Small cuboidal
Lots of intermediate filaments (keratin)
Highly metabolically active

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description of prickle cell layer

Larger polyhedral cells
Lots of desmosomes (connections)
Intermediate filaments connect to desmosomes

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description of granular layer

2-3 layers of flatter cells
Large keratohyalin granules – contain structural filaggrin & involucrin proteins
High lipid content
cell nuclei lost

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what originates in the granular layer

the cornified envelope

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what does the granular layer contain

odland bodies (lamellar bodies)

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what is contained in the keratin layer

corneocytes - overlapping non-nucleated cell remnants

lamellar granules - release lipid

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where does the cornified envelope become insoluble

keratin layer

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what are the features of oral mucosa

Masticatory – keratinised to deal with friction/pressure
Lining mucosa – non-keratinised
Specialised mucosa - tongue papillae (for taste)

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where are melanocytes found

in basal layer and above

what do melanocytes contain and how and where are they transferred

melanosomes | transferred to adjacent keratinocyte via dendrites

what is melanocytes function

convert tyrosine to melanin pigment (eumelanin and phaeomelanin)

what does melanin do

absorbs light

true or false - melanosomes form a protective cap over nucleus

true

what is nelson's syndrome

melanin stimulating hormone is produced in excess by the pituitary

where do langerhans cells originate and where are they found

bone marrow prickle cell layer and above also in dermis and lymph nodes

what is the function of langerhans cells

involved in skin immune system antigen presenting cells Pick up antigen in skin and circulate to lymph nodes via lymphatic system

where are merkel cells found and what do they do

basal layer between keratinocytes & nerve fibres | mechanoreceptors

what is pilosebaceous unit

hair follicles

what does hair follicles consist of

Epidermal component plus dermal papilla | Adjacent sebaceous gland

what does hair follicles contain

specialised keratins

what are the phases of growth of hair follicles

anagen - growing catagen - involuting telogen - resting

what is the most common cause of human hair-loss

telogen effluvium

what is virilisation and what causes it

male features developing in women | excess androgen

what is an autoimmune cause of hair loss

alopecia areata

what are nails made of and what is the growth rate

specialised keratins | 0.1mm per day (fingers>toes, summer>winter)

what is the role of the demo-epidermal junction

support, anchorage, adhesion, growth and differentiation of epidermal cells semi-permeable membrane acting as barrier and filter

inherited diseases of DEJ

epidermolysis bullosa: simple (EBS) or dystrophic (EBD)

causes of congenital disease of DEJ and examples

auto-antiobides to proteins in DEJ | e.g. pemphigus, pemphigold, dermatitis herpetiformis

what are the components of the dermis

cells - fibroblasts, macrophages, mast cells, lymphocytes, Langerhans cells fibres - collagen (majority) and elastin

what are the function of fibroblasts

make collagen and elastin

true or false - skin has a small blood supply

false | supply is greater than metabolic need

what is the flow of blood in the skin

Arteriole --- precapillary sphincters --- arterial capillaries ---venous capillaries -- post-capillary venules --- collecting venules

what is an angioma

localised overgrowth of blood vessels | e.g. port wine stain, "stork marks:

what is the function of lymphatic vessels

- immune surveillance by circulating lymphocytes and Langerhans cells - channelling of micro-organisms / toxins - Continual drainage of plasma proteins, extravasated cells and excess interstitial fluid

what does the loss of protein in the skin lead to

oedema

what nerves are responsible for sensing pressure on skin

pacinain corpuscles

what nerves are responsible for sensing vibration on skin

meissners corpuscles

what are the types of nerves in the skin - top to bottom

``` free nerve ending meissners corpuscles sensory nerve fibre pacinian corpuscle motor nerve fibre ```

what are neurofibromatosis

overgrowth of the nerve endings

what are the 3 type of skin glands

Sebaceous Eccrine Apocrine

description of sebaceous glands

Widely distributed: - largest glands present on face and chest Hormone sensitive – inactive pre-puberty

what does sebaceous glands produce and where do they mainly open up onto

sebum | hair follicles

what is the function of sebaceous glands

control moisture loss | protection from bacterial and fungal infection

what are sebaceous glands are part of

pilosebaceous unit

what is acne a combo of

increased sebum, blocked ducts | and bacterial activity

what is the function of apocrine sweat glands

Produce oily fluid - produce odour | Scent glands

what do apocrine glands develop as part of

pilosebaceous unit

where are apocrine glands found

axillae and perineum

what are apocrine dependant on and when are they most prominent

androgen | after puberty

where are eccrine glands found

Whole skin surface  - palms, soles and axillae in particular

what is the nerve supply for eccrine glands

sympathetic cholinergic nerve supply

what are the functions of the eccrine glands

cooling by evaporation | moistens palms/soles to aid grip

what are the functions of skin

``` Barrier function Metabolism & detoxification Thermoregulation Immune defence Communication Sensory functions ```

what is toxic epidermal necrolysis

acute skin failure | sheering off of the epidermis all over the skin

what are the consequences of failure of barrier

1 - fluid loss therefore, dehydration 2 - protein loss therefore, hypoalbuminaemia 3 - infection

what are the consequences of failure of thermoregulation

heat loss - hypothermia

what are the consequences of failure of immune defence

spread of infection

what are the consequences of failure of metabolic

disordered thyroxine metabolism

what are the consequences of failure of sensation

pain

what are the four stratum layers of epidermis - top to bottom

1 - stratum corneum 2 - stratum granulosum 3 - stratum spinosum 4 - stratum basale

why does melanin cover the nuclei

to absorb UV rays and protect DNA in the cells nuclei

what is vitamin D3 stores as and where

hydroxycholecalciferol in liver

what happens to hydroxycholecalciferol

Converted to 1,25-dihydroxycholecaliferol in kidney

what are the functions of melanosomes

synthesis, storage and transport of melanin

Structure and Function of Skin Flashcards

(80 cards)