Intergumentary system. Premed II. Integumentary System. Skin and its epidermal derivatives such as nail, hair, sweat gland, sebaceous gland and mammary gland. Epidermis is an epithelial layer of ectodermal origin. Morphometry of skin:
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Skin and its epidermal derivatives such as nail, hair, sweat gland, sebaceous gland and mammary gland.
Epidermis is an epithelial layer of ectodermal origin.
Morphometry of skin:
- largest and heaviest organ– 1.2 to 2.3 m2 ;16% of the total body weight in adults.
- thickness varies form 1mm to 5mm;
- thickest over the back; thinnest in the eyelid
- two types : - non-hairy (thick or glabrous or smooth skin) found in palm and sole
- hairy or thin skin – covering most of the body surface
- two layers : epidermis, dermis
- supported and anchored to subcutaneous tissue – hypodermis (subcutis)
Epidermis - the superficial layer
- keratinised stratified sqamous epithelium; well developed in nonhairy skin
- five layers in non – hairy skin:
from deep to superficial
- stratum basale or germinativum
- strat. spinosum
- strat. granulosum
- strat.lucidum (not found in hairy skin)
- strat. Corneum
Dermis - connective tissue arranged in two strata:
- superficial papillary layer
- deep reticular layer
Finger Prints and Foot Prints
Unique for each individual , appearing as loops, arches and whorls or combinations of these form.
Probably determined by multiple genes.
Used for person identification .
Stratum Malpighii = str. basale + str spinosum
-cuboidal or polyhedral cells, exhibit numerous cytoplasmic extensions (spines) so the name.
Colour of skin is the result of several factors,the most important of which are the content of melanin and carotene,number of blood vessels in the dermis .
Eumelanin is a dark brown pigment produced by the melanocyte, a specialised cell of the epidermis found beneath the cells of the str. Basale and in the hair follicles.
-A common skin disease
There is increase in number of proliferating cells in the str. Basale and spinosum as well as a decrease in the cycle time,.
This results in greater epidermal thickness and more rapid renewal of epidermis----7 days ,instead of the regular 15-30 days.
Although melanocytessythesize melanin ,epithelial cells act as a depot and contain more of this pigment.
-- hereditary inability of melanocytes to sythesizemelanin.
Melanocytessythesize a dark brown pigment(melanin) in oval shaped organelles(melanosomes).
Melanosomes contain tyrosinase, a UV- sensitive enzyme involved in melanin synthesis.
--lack of cortisol from the adrenal cortex, causes overproduction of ACTH, which increases the pigmentation of the skin.
Addison”s disease is caused by dysfunction of the adrenal glands**
--the degeneration and disappearance of the entire melanocyte results in a depigmentation disorder.
-major env. factor is the sun or UV light.
***pheomelanin***is less protective against UV radiation damage.
Appendages of Skin
Dermal fibroblasts: synthesize ground substance & fibres
Langer lines: lines of cleavage or tension lines
- formed by definitive orientation of fibres in the dermis
- a cut in the skin parallel to Langer lines will heal fast with minimal scar
- a linear wound perpendicular to Langer lines will tend to gape and heal slowly with conspicuous scar.
A holocrine gland-----the products are secreted with the remnants of dead cells,stem cells at the base of the gland proliferate to replace lost cells.
The products comprises of a complex mixture of lipids that includes:triglycerides ,waxes ,squalene, and cholesterol and its esters.
Sebaceous gland begins to function by puberty,the primary control of sebaceous gland secretion in men is testosterone and in females a combination of ovarian and adrenal androgens.
Flow of sebum is continuos, and a disturbance in the normal secretion and flow of sebum is one of the reasons for development of a chronic inflammation of obstructed sebaceous glands.
**it occurs mainly during puberty**
Glands of moll and the ceruminuous glands????
Where are these glands found??