The Integumentary System

THE INTEGUMENT
Basics of the Integumentary System

I. Function
A. Protection
 Against microorganism
 Against water loss
 Against UV light
B. Sensory Organ
 Contains receptors
C. Temperature Regulation
 Sweat Glands – evaporation of sweat
cools the body
 Blood flow through the cutaneous blood
vessels
 Flushed – vasodilation: Increased
blood flow to the skin  Increased
Heat loss
 Pallid – vasoconstriction: Decreased blood flow to the skin  Decreased Heat loss
D. Synthesis of Vitamin D
 Skin produces Calciferol; a steroid hormone which increases absorption of Ca2+ in the small intestine
***SKIN IS THE LARGEST ORGAN OF THE BODY
II. Openings of the skin into the Interior of the body
A. Mouth
B. Nares
C. Anus
D. Urethral Canal
E. Vaginal Canal
III. Layers of the Skin
A. Epidermis
 Stratified Squamous Epithelium – Keratinized
 Differentiates from Ectoderm
 Stratum Germinativum
 Actively growing
 Bottom layer of cells contain Melanin protein
(brown pigment by melanocytes)
 Stratum Corneum
 Consists of dead, flattened cells (keratinocytes)
containing much proteins
 Acts to waterproof the skin surface
 External pressure on the skin stimulate growth and
thickening
 Palms and soles of the feet
 Calluses (hand) and Corns (foot)
 Supplied by blood vessels from dermis through
diffusion
 Friction Ridges – grasping fraction
(fingerprints)
B. Dermis
 Much thicker layer than the epidermis
 Dense Irregular Fibrous Connective Tissue
 Contains fibroblasts and collagen
 Differentiates from Mesoderm
 Supplied with blood vessels and nerve fibers


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