Only organ is the skin
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The body
Only organ is the skin
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on this image for an audio message
I. Functions of system
1) Protection:
a) Physical – stratified squamous epithelium keeps pathogens out.
b) Chemical – melanin blocks uv rays.
c) cellular-white blood cells (macrophage) eat and destroy invading bacteria
2) Prevents water loss
tough scaly epidermis, oily secretions prevent water loss.
3) Thermoregulation:
a) sweat secretions allow evaporative cooling
b) altered blood flow allows changes in skin temperature
4) Sensation-all receptors in dermis
a) Touch receptors – Meissner’s corpuscles-touch
b) Pressure receptors – Pacinian corpuscles-pressure
c) Pain receptors – bare/naked/free dendrites-pain/damage
5) Vitamin D (Calcitriol) production
Vit D is important in promoting calcium absorption by intestine.
II. Structure:
Composed of three LAYERS
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A. Epidermis layer:
- The superficial layer - Made of a keratinized stratified squamous epithelium,
avascular
1) Stratum Basale/Germinativum:
the deepest layer is an active zone of cell division
contains melanocytes that increase pigmentation (melanin) and therefore protection
against UV radiation from sun
2) Stratum Corneum:
the most superficial layer forming 75% of the epidermis.
20 – 30 cell layers thick with all cells dead which is constantly shed,
thereby removing attached pathogens.
B. Dermis layer:
- Made of dense irregular connective tissue.
- Vascular.
- Contains leucocytes (white blood cells) that digest pathogens
- Contains glands, receptors, hair follicles, etc.
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C. Hypodermis layer: the subcutaneous layer
- Mostly adipose tissue.
- For energy storage and thermal insulation.
- Anchors the skin to the muscles.
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Distinguish the locations (layers) from the structures
(tissues) that make up the layers.
III. Glands:
A. Sweat/Sudoriferous Glands:
They cover the entire body except the nipples and external genitalia.Abundant
on the palms, soles, and forehead.
Produce sweat that reduces body temperature.
Also acts as an antibiotic, killling bacteria.
B. Ceruminous: produce ear wax in the acoustic canal.catches debris entering
ear.
C. Sebaceous Glands:
Found everywhere except the palms and soles.
Secrete sebum (oil) into hair follicles to reduce loss of water.
Also acts as an antibiotic, killling bacteria.
Helpful web link
A web activity
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Professor Thomas M. Lancraft
Human Anatomy Courses
at St. Petersburg College
St. Petersburg/Gibbs Campus
9/2007