skin and structure Flashcards
what is the epidermis and dermis of the skin in mammals
epidermis is the outer layer made of stratified cellular epithelium
dermis is beneath the epidermis and is made of connective tissue
how is the epidermis formed
ectoderm cells from a single layer or periderm. Gradual increase in layers of cells. Periderm cells case off
how is the dermis formed
formed from mesoderm below ectoderm
what are melanocytes
pigment producing cells from neural crest
what are the layers of the epidermal cells from outside in
keratin layer granular layer prickle cell layer basal layer dermis
what is the basal layer made of
one cell thick, small cuboidal, keratin, highly metabolically active
what is the prickle cell layer made of
large polyhedral cells, lots of desmosomes (connections), intermediate filaments (keratin) connect to desmosomes
what is the granular layer made of
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
what is the keratin layer made of
corneocytes (overlapping non nucleated cell remnants), insoluble cornfield envelope, 80% keratin and filaggrin, lamellar granules release lipid, tight waterproof barrier
what are melanocytes
- 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)
what is Nelsons syndrome
Melanin stimulating hormone is produced in excess by the pituitary
what are langerhans cells
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)
what are Merkel cells
- basal
- between keratinocytes and nerve fibres
- mechanoreceptors
- direct entry point to CNS to the dorsal route ganglion
what makes up a pilosebatious unit (hair follicle)
- hair follicle (3 main segments = infundibulum, the isthmus and hair bulb)
- hair shaft
- arrestor pili muscle
- sebaceous glands
what are the phases of growth of hair follicles
anagen - growing (3-7 years)
catagen - involuting (3-4 weeks)
telogen - resting (shedding phase)
what is the key role in epitehelial-mesenchymal interactions
Support, anchorage, adhesion, growth and differentiation of basal cells
Semi permeable membrane acting as barrier and filter
what layers make up the demo-epithelial junction
- basal cells (keratinocytes)
- lamina lucida
- lamina densa
- sub-lamina densa zone
what substances make up the dermis
- ground substance
- cells = mainly fibroblasts, macrophages, mast cells, lymphocytes, Langerhans cells
- fibres = collagen and elastin
- muscles, blood vessels, lymphatics, nerves
what is angioma
benign group of blood vessels in the dermal tissue that are bumpy red on appearance
what is the function of the lymphatic system
- 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
what is the nerve receptor for pressure and vibration
pressure receptor = Pacinian
vibration receptor = Meissners corpuscles
what are the 3 types of skin glands
sebaceous
apocrine
eccrine
what is the function of sebaceous glands
- largest gland in face and chest
- produces sebum
- its function is to control moisture loss and protection from fungal infection
what is the function of apocrine sweat gland
- Found in the axillae, groin, eyelids, ears, mammary and perineal regions
- Produces oily fluid and creates an odour after bacterial decomposition
