Histology 12: Nsu Spring 2009 Taken By: Gregory Rodocker

Histology 12 NSU Spring 2009 Taken by: Gregory Rodocker

Skin 

   

Largest and heaviest single organ of the body 1.2-2.3 m2 surface area Outer epidermis Lower dermis and Underlying hypodermis (which is not actually considered part of the skin)

Epidermis 

Stratified squamous epithelium 



Cells called keratinocytes

Also contains 

Melanocytes 

 

Produce melanin

Langerhans cells Merkel’s cells

Thin vs. thick skin 

Thick skin or non-hairy 



Thin skin or hairy 



Palms and soles Found everywhere else

What varies is the thickness of the epidermis

Thin skin

Epidermal layers 

Stratum basale 

 



Single layer of columnar to cuboidal cells on basement membrane Desmosomes and hemidesmosomes Intense mitotic activity (every 15-30 day replacement) Produce keratin

Epidermal layers 

Stratum spinosum    

Cuboidal to flattened cells Spiny, studded appearance Thicker in areas of wear and tear Provides resistance to abrasion

Epidermal layers 

Stratum granulosum  

3-5 layer of flattened polygonal cells Cells release lipid material that seals the cell layer

Epidermal layers 

Stratum lucidum    

More obvious in thick skin Translucent Flattened cells Dying and dead cells

Epidermal layers 

Stratum corneum    

15-20 layers (in thick skin) Flattened, non-nucleated keratinized cells Cells dead Cells lost to wear and tear

Melanocytes 

Produce melanin 

 

Eumelanin – dark brown Pheomelanin – reddish Racial and individual differences in skin color result from the amount of melanin and not the number of melanocytes

Melanin

Sunscreen components

Protection by melanin 



Note that the melanin granules are around the nucleus to protect it from solar radiation Skin color caused by melanin, blood vessels and blood flowing

Langerhans and Merkel’s cells 



Langerhans cells are the APC’s of the skin Merkel’s cells may be sense organs for mechanoreception or serve a neuroendocrine role

Dermis 



CT that supports the epidermis and connects it to the hypodermis Two layers 



Papillary layer that is thickest in wear and tear areas Reticular layer

Dermis 

Contains   

Hair follicles Sebaceous glands Sweat glands 





All of epidermal origin

Sympathetic but no parasympathetic innervation to skin structures Rich blood and lymph supply

Sensory structures   

Pacinian corpuscles Meissner’s corpuscles Free nerve endings

Meisner’s Corpuscles

Hair follicles 

Hair is found everywhere except      

Palms Soles Lips Glans penis Clitoris Labia minora

Hair follicle

Sebaceous glands  

Acinar glands 100 glands/cm2 



400-900 glands/cm2 on face, forehead and shoulders

Produce sebum 

Lipids including triglycerides, waxes squalene and cholesterol

Squalene (aka spinicene or supraene)

Sweat gland  

Everywhere but in the glans penis Produce sweat 

Water, sodium chloride, urea, ammonia ad uric acid

Ducts lined by stratified cuboidal epithelium

Skin Cancer 



One third of all cancers are skin cancers Three types:   

Squamous cell carcinoma Basal cell carcinoma Malignant melanoma

Squamous and basal cell Ca