3.Integumentary system

3.Integumentary system

1. Functions of the skin

   • Temperature regulation
   • Produce vitamin D
   • Protect from the harmful radiation by melanin
   • Protection

2. Structure

   • Three layers(simple)
     • Epidermis
       • 1. composed of keratinized stratified squamous epithelium
       • Sweet glands
       • Melanocytes
         • 1. produce melanin(primarily responsible for skin color)
         • Round cell + clear cytoplasm
         • Locate in stratum basale
       • Sebaceous glands
       • Hair follicles and hair
     • Dermis
       • 1. composed of a dense connective tissue: - impact mechanical support -strength -thickness(e.g. papillae layer(PL), collagen fibers of the reticular layer(RL)
     • Hypodermis
       • -contains large amount of adipose tissue

3. Types of skin

   • Thick
     • 1.  epidermis is supported by dermis(a layer of dense fibro-elastic tissue) 2.Merges with the loose supporting tissue of hypodermis
     • Stratified squamous keratinizing epithilium
       • 1.extremely thick 2.keratinized surface layer
     • Structure
       • Epidermis(five layers)
         • Stratum corneum(SC)
           • 1. stratified squamous epithelium 2. consist of flattened, closely packed, dead cells and absent nuclei
         • Stratum granulosum(SG)
           • 1. 2-5 layers of nucleated cells 2. basophilic granules(keratohyalin)
         • Stratum basale(SB)
           • 1. single layer of cubondal cells on basement menbrane
         • Stratum lucidum(SL)
           • - homogenous line of flattened cells
         • Stratum spinosum(SS)
           • 1. 3-4 cells thick 2. polyhydral 3. basophilic
       • Dermis(three layers)
         • Subcutaneous layer
           • 1. loose connective tissue 2. adipose tissue
         • Reticular layer
           • 1. mainly of bundle of  coarse collagenous fibres(in various direction)
         • Papillary layer
           • Consist of: 1. fine collagenous fibres 2. reticular fibre 3. elastic fibres -all interweaving with Blood vessels
       • Hypodermis
   • Thin
     • abdominal skin
       • 1. thin stratified squamous   2.only stratum corneum and stratum germinativum
   • Scalp
     • Papillary layer
       • 1. marrow zone of fibred dense irrugular connective tissue
     • Reticular layer
       • 1. Hair follicle associated with sebaceous gland 2.also find cross section of sweet gland
       • Hair follicle
         • 1. features: extended hair bulb and the dermal papilla 2. the main mass of hair bulb= matrix(for hair growth)
       • Sebaceous gland
         • 1. simple branched acinar glands 2. appear encapsulated spherical masses form 3. Vacuolate cytoplasm( for lipid and waxy secretion)
       • Sweet gland
         • 1. simple coil tubular gland - appear in section as groups of small circular ovoid  structure