skin structure and function Flashcards
what is the largest organ in the human body
the skin
in general how thick is human skin
0.1mm thick but varies in areas e.g. eyelids
how many major layers are there to human skin and what are they
3; epidermis, dermis and hypodermis
describe the epidermis layer and what its made of
a stratified squamous epithelial layer made up of keratinocytes and melanocytes (these contain our pigment that helps prevent damage from UV)
describe the dermis layer and what its made of
a supportive connective tissue matrix made up of fibroblasts and immune cells
describe the hypodermis and what its made of
an adipose (fat layer) under the dermis that is made up of adipocytes
what are rete ridges and where can they be found in the skin
rete ridges make up the uneven shape of the lower epidermis - where it joins to the dermis - they are there to increase cell contact and prevent blisters
at what points is gestation do the epidermis and dermis form
epidermis - 1st month
dermis - 11 weeks
name the 7 functions of the skin
1.Prevents mechanical abrasion of underlying tissues and coordinated wound healing
2.Prevents desiccation or water absorption - stops water getting out
3.Prevents injury by chemicals / radiation
4.Barrier to pathogens
5.Mechanism of sensation
6.Some metabolic functions - vitamin D is made in the skin
7.Mechanism of thermoregulation
which layer are sensory nerve endings found
dermis
what do sebaceous glands do
feed fluid into the hair follicle duct
what do arrector pili muscles do
move the hair follicles during thermoregulation
which layer of the skin are sweat glands found
the hypodermis but the extend all the way to the skins surface
name 4 functions of the hypodermis layer of skin
- gives stability to structures above
- reduces heat loss from the body
- absorbs blows to the body - prevents injury
- energy reserve - keeps us warm over winter
where are merkel cells found and what do they do
in the epidermis but they are rare - they provide sensation in the skin
why is the epidermis stratified
the upper cells provide protection of the lower (stem) cells, meaning that during abrasion the skin cell layers are not hard to replace
what are the 5 layers of the epidermis (starting from the layer closest to the dermis)
basal layer
spinous layer
granular layer
transition zone
cornified layer
describe the cells in the basal layer of the epidermis
all they cells are columnar and they divide every 200-400 hours - they cannot differentiate as they have very low levels of calcium
describe the cells in the spinous layer of the epidermis
the cells are larger, flattened, and contain more calcium than those in the basal layer - meaning they can differentiate
what do Langerhans cells cause and where do they come from
they cause allergic reaction response and they come from the bloodstream in the dermis
describe the granular layer in the epidermis
made up of keratohyalin granules containing profilaggrin, and lipid-filled lamellar granules - these provide structure and waterproofing of the skin
where is the transition zone found in the epidermis layer of the skin
between granular (living) and cornified (dead) layers
name 5 things that happen in the transition zone in the epidermis layer of the skin
- enzymatic activity and cellular restructuring
- profilaggrin is cleaved to produce filaggrin - a good biomarker
- organelles are destroyed by different enzymes
- lamellar granules fuse with plasma membrane and release lipids into extracellular space
- cornified envelope forms - empty cells
describe the cells in the cornified layer of the epidermis
corneocytes are flattened, empty, dead cells that form a protective surface for the skin
