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)