this is the largest organ in the body
skin
skin functions:
_____: barrier against the invasion of physical , chemical , and biological agents
-prevents loss of ___ and __
- ___ regulation-arterio-venous anastomosis , hair elevation and sweating assists in this function.
-sensation
-__ permits movement
-immune function
-___ -sweating helps maintain ion and water balance
-___ homeostasis-UV light absorbed thrugh skin has a role in production of vit D
-___ storage_lipids in adipose tissue within subcutaneous CT
Protection water and electrolytes temperature regulation elasticity excretion calcium homeostasis energy storage
skin regions
epidermis and dermis
-Stratified squamous epithelium , AVAScular, THICK barrier, contains the cells: keratinocytes (most common), non-keratinocytes: langerhans cells, merkel’s cells, melanocytes, and variable numbers of intraepithelial lymphocytes
EPIDERMIS
this part of the skin has a papillary and reticular layer , MESODERMAL origin, CT(principal component) , VAScular and nervous supply, and supports the epidermis,
DERMIS
dermis has 2 layers: this layer is where loose CT is found , type I and III collagen, and found in mast cells, macrophages, vessels and nerves
papillary layer of dermis
dermis has 2 layers: this layer is where dense IRREGULAR CT is, Type I collagen , network of elastic fibers and found in blood vessels and nerves
reticular layer of dermis
what is the order of formation of the strata of the epidermis of the skin
stratum basale stratum spinosum stratum granulosum stratum lucidum stratum corneum
This portion has an
- epidermal dermal junction ,
- single layer of cuboidal to columnar cells,
- rests on the basal lamina,
- is the area of mitotic activity,
- and may have the presence of melanocytes
stratum basale
This layer is
- cuboidal or slightly flattened
- desmosomes and increased number of tonofilaments give SPINY appearance
- cells are cohesive and they resist abrasion
- cells in this layer retain capacity for division if needed
stratum spinosum
This layer is
- 3-5 layers cells start to flatten
- keratohyalin granules present (bind w/keratin filaments)
- stains basophilic
- lamellar granules (secreted to from waterproof lipid sheets)
- NO MITOTIC ACTIVITY
- LAST LIVING LAYER
stratum granulosum
This layer is -translucent
- many keratin filaments, desmosomes present
- cellular organelles are gone now- fully keratinized
- cytoplasm contains eleidin (protein related to keratin)
stratum lucidum
This is the most superficial layer
- 15-20 layers thick
- cells consist of keratin
- known as HORNY cells surrounded by a thicker plasma membrane coated by a thicker plasma membrane
- cells continuously shed here
stratum corneum
-production of stratum corneum by terminal epidermal differentiation is known as
cornification
what produces melanin?these cells also are present in the stratum basale, have neural crest origin, are stable cells and -live for years .
-Absorbs harmful UV radiation by transforming energy into harmless amts of heat
protects cells from effects of UV radiation
-must have tyrosine for proper function
melanocytes
this is the most common form of melanin, brown/black pigment
eumelanin
red brown polymer largely responsible for red hair and freckles
pheomelanin
if there is no tyrosine this means there is no melanin therefore this results in an ______
albino animal
langerhans cells have a function in the ___ __
immune system
this is an epidermal invagination has a glassy membrane - a thick BM.
hair follicle
These parts compose a?
- medulla- loose cuboidal cells, air filled areas
- cortex- dense compact keratinized cells parallel to hair shaft
- cutilce- single layer of flat keratinzed cells
hair
layers of a hair follicle
-dermal papilla-carries blood supply to cells of hair
-root sheath :
external glassy membrane
external root sheath
internal root sheath
cuticle
types of hair follicles
primary and secondary
this type of hair follicle is large diameter , rooted deep in dermis, sebaceous gland, arrector pili muscle, sweat glands
primary hair follicle
