INTEGUMENTARY SYSTEM

 

Integumentary System

 “covering” Composed of:

 	
Cutaneous membrane:

–       Epidermis - superficial epithelium

–       Dermis - underlying “cutaneous tissue” with blood supply

 	
Accessory structures:

–       Hair

–       Nails

–       Exocrine glands

Functions:

 	
Protect underlying tissues from infection, exposure and dehydration.
 	
Excrete salts, water, and organic waste.
 	
Maintain normal body temp (conserve and radiate heat).
 	
Synthesize Vitamin D3 for calcium metabolism.
 	
Store nutrients (fat).
 	
Sensory detection: touch, pressure, pain, and temp.

Epidermis:

 	
The corrugated border between dermis and epidermis helps bond epidermis to the dermis (increased surface area for attachment):

–       In thick skin, epidermal ridges show on the surface as fingerprints: function to enhance gripping.

 	
Epidermis water resistant but notwaterproof:

–       Insensible perspiration: water loss through epidermis: ~500ml (1 pint)/day (more if damaged, e.g. burn).

–        Callus: thickening of the epidermis, due to repeat friction

–       Blister: separation of epidermal layers of epidermis from dermis, space fills with interstitial fluid.

Skin color:

 	
Pigment-based: epidermal pigments and blood pigments contribute to the color.
 	
Epidermal Pigmentation:

–        Carotene: yellow-orange, from diet.

–        Melanin: brown, from melanocytes.

Sensory perception in integument:

 	
Skin highly innervated for sensory perception, mostly in the dermis:
 	
Tactile discs/Merkel cells:

–       deep layers of epidermis, superficial touch.

 	
Free nerve endings:

–       the superficial dermis, pain, and temperature.

 	
Tactile/Meissner’s corpuscles:

–       the superficial dermis, light touch.

 	
Lamellated/Pacinian:

–       corpuscles -deep dermis, pressure and vibration.

Accessory Structures of the Integument:

 	
Hair follicles and hair
 	
Sebaceous glands
 	
Sweat glands
 	
Nails

v   All these structures are anchored in the dermis but are derived from epidermal tissue.

Hair Functions:

 	
Head:

–        UV protection

–        Cushion from trauma

–        Insulation Nostrils, Ears canals, Eyelashes: -prevent the entry of foreign material.

 	
Body hair:

–       Sensory detection

Integumentary Glands:

v  All are exocrine glands (secrete product onto skin surface via a duct).

 	
Sebaceous glands:

–       Holocrine secretion

–        Secrete sebum into hair follicle

Sebum: lipids +cholesterol + proteins + electrolytes.

 	
Function:

–       lubricate and protect keratin.

–       Prevent evaporation.

–       Inhibit bacterial growth.

v   Sebaceous glands active in the fetus, then off until puberty, on whole adult life.

Sudoriferous glands / Sweat glands:

Merocrine/Eccrine sudoriferous glands:

 	
Produce sensible perspiration: 99% water + electrolytes + organic nutrients + antibodies + antimicrobial agents + organic wastes.

–       Functions:

 	


 	
Evaporative cooling of the surface of the skin to reduce body temp
 	
Excrete waste electrolytes and drugs
 	
Protection:




 	


 	


 	


 	
 Prevent adherence of microbes (antibodies).
 	
 Physically wash off microbes.
 	
 Antimicrobial agents to kill microbes dermcidin (antibiotic).








 	


 	
 Merocrine secretion.
 	
 Small coiled tubular glands.
 	
 Located in the superficial dermis.
 	
 Open directly on the surface of the skin.
 	
Secrete in response to high temp or stress.




 	
Merocrine secretion
 	
Armpits, nipples, groin
 	
Secrete into the hair follicle
 	
Secretion is sticky and cloudy:

–       sensible perspiration + proteins + lipids

 	
Microbes eat it → wastes: body odor
 	
Glands deep in the dermis
 	
Surrounded by myoepithelial cells: a contract in response to sympathetic nervous system stimulation
 	
Active only after puberty
 	
Special apocrine sweat glands:

–        Mammary glands:

 	
located in female breast -secrete milk during lactation.

–       Ceruminous glands:

 	
located in external ear canal-secrete cerumen.

Nails:

 	
Scale like projections on the dorsal surface of distal digits.
 	
Functions:

–       Protect tips from mechanical stress, assist gripping.

–       Consists of dead cells containing hard keratin.

–       New nail formed at nail root -nail growth is continuous.

Injury and Repair:

 	
Integument can function independently of nervous and endocrine systems to maintain own homeostasis.
 	
Mesenchymal cells of the dermis can regenerate connective tissue.
 	
Germinative cells (basal cells) of the epidermis can regenerate epithelial tissue.