integument membrane

integument

largest organ=skin

• epithelial tissue = epidermis

• connective tissue = dermis

epidermis

=epithelial tissue

• keratinocytes - stratified squamous cells

• ectodermal origin

in epidermis, outermost cells…

completely keratinized

• keratin - protective protein

epidermis has…

• no vascular network

• houses secretory cells

• secretory glands originate from epidermis

  • extend into dermis

dermis

= connective tissue

• loose and dense irregular

• mesodermal origin

dermis has…

• blood vessels

• location of: hair follicles, sweat and oil glands, nerve endings

epidermis layers from inside to out

1. stratum basale

2. stratum spinosum

3. stratum granulosum

4. stratum lucidum

5. stratum corneum

stratum basale is a…

single layer of proliferative cells = basal cells/keratinocyte precursors

• sym and asym division

• produce keratin 5 and 14

startum basale is anchored to

basal lamina and dermis via keratin 5 and 14

• basal lamina lies between stratum basale and dermis

stratum spinosum is a …

stratified layer

• spiny appears due to desmosomes

• keratinocytes produce keratin 1 and 10 and glycolipid

stratum granulosum is a…

stratified layer

• cell nuclei begin to degrade

• keratinoctyes produce 1 and 10 and keratohyalin

  • keratohyalin collects into lamellar granlues and promotes keratinization

stratum lucidum is…

present only in thick skin of palm, soles, and digits

• stratified layer

• keratinocytes: dead and flat

  • undergoing keratinization

stratum corneum is…

keratinocytes almost completely keratinized

• dead, flat, dry

• lamellar granules emptied

in stratum basale, what are the 2 other cells present

1. melanocytes - produce pigment protein

2. mechanoreceptors- merkel’s cells and tactile discs

in stratum spinosum what is the other cell present

langerhans cell - immunologic functions

dermis layer from inside out

1. reticular layer

2. papillary layer

reticular layer is made up of…

• dense irregular connective tissue

• fixed cells = fibroblasts

• wandering cells = mast and lymphocytes

• mechanoreceptors=pacinian corpuscle

reticular layer fibroblasts

extra cellular matrix

• fibers = collagen and thick elastic

• ground substance = hyaluronic acid, glycoproteins and proteoglycans

papillary layer is made up of…

• loose connective tissue

• fixed cells = fibroblasts

• wandering cells = mast, macrophages, dermal dendrocytes

• mechanoreceptors = meissner’s corpuscle

papillary layer purpose

provides nourishment to epidermis

• interdigitated with epidermis = dermal papppillae

tissue homeostasis

stratum corneum constantly sloughed off so stratum basale cells needs to provide replacement cells

tissue homeostasis replacement cells

unipotent precursor cells behave similarly to neural progenitor cells

• 1st sym = self renewing daughters

• 2nd asym= self renewing daughter + 1 replacement TA

• 3rd sym= replacement TA daughters

tissue homeostasis - 5 stem cell lineages

1. basal layer of epidermis

2. feather/hair follicle bulge

3. base of sebaceous gland

4. dermal papillae

5. dermis

to maintain tissue homeostasis…

stem cells balance self renewal against replacement

• self renewal rate = replacement rate

post natal growth disrupting homeostasis

precise mechanism unknown

• basal cells produce special precursors

  • limited, imbalanced divisions

  • decrease replacement cell production with progressive divisions

factors that affect integument growth

• nutrition

• hormones

• genetics

• physical condition

• disease