Transcript Skin and the Integumentary System

Skin and the
Integumentary System
Chapter 6
Anatomy & Physiology
1
I. The Integumentary System
 A. The cutaneous membrane (the skin) and
accessory organs make up the integumentary system
 B. Types of membranes of this system (4)
 1. Serous membranes: line body cavities that do
not open to the outside
 Line the thorax (parietal pleura), abdomen
(parietal peritoneum), and cover the organs w/I
these cavities (visceral pleura, visceral
peritoneum)
 Consists: Layer of simple squamous epithelium
and a thin layer of loose connective tissue
 Secrete serous fluid for lubrication
2

2. Mucous membranes: line cavities and
tubes that open to the outside
 Line the oral and nasal cavities, tubes of
digestive, respiratory, urinary, and
reproductive systems
 Consists: Epithelial tissue over loose
connective tissue
 Goblet cells secrete mucus
3
3. Synovial membrane: form the lining of
the joint cavity between the end of bones
at freely moving joints (aka synovial joints)
 Include dense connective tissue over
loose connective tissue and adipose
tissue
 Secrete synovial fluid into cavity for
lubrication
 4. Cutaneous membrane: THE SKIN,
details follow.

4
II. The Skin
 A. Functions:







regulate homeostasis,
forms protective covering,
regulate body temperature,
retard water loss from deeper tissues,
house sensory receptors,
synthesizes biochemicals, and
excretes small quantities of wastes
5
B. Layers of Skin
1. Epidermis (Figure 6.1-6.3)








Composed of stratified squamous epithelium
As cells divide, older ones are pushed toward the top layer
of skin
Keratinization: the development of the protein keratin in the
outermost cells
Stratum corneum: outermost layer
Stratum basale: innermost layer
Corns and calluses: regions on the palm and foot where
cells are dividing at fast rates
Functions to prevent water loss, mechanical injury, and
harmful chemical effect of underlying tissues
Melanin: dark pigment of the skin to protect from UV light;
work by absorbing UV radiation; sometimes melanin is
passed to other epidermal cells via cytocrine secretion
6
Section of Skin
7
Cross-section of skin showing layers
8

2. Dermis





Boundary between dermis and epidermis is
uneven due to cellular projections
Function: binds the epidermis to underlying
tissues
dense connective tissue creates the toughness of
the skin and its elasticity
Dermal blood vessels supply nutrients to all skin
as well as regulate body temp
Nerve cells, hair follicles, sebaceous glands, and
sweat glands are scattered throughout
9

3. Subcutaneous layer




Layer beneath the dermis
Loose connective tissue and adipose tissue
Insulates to keep heat in and protects to keep
heat out
Contains major blood vessels for the skin
10
III. Accessory Organs
 A. Hair follicles: develops hair; group of epidermal cells at the
base of a tubelike depression
 Found on all body surfaces except palms, soles, lips,
nipples, parts of external reproductive organs
 Contains the hair root; extends from surface to dermis
 Hair is composed of dead epidermal cells; cells become
keratinized & die
 Genes determine hair color by the amount of melanin;
epidermal melanocytes located at deep end of follicle
 Dark hair – lots of melanin




Blonde hair – little melanin
White hair – no melanin
Gray hair – mixture of lots/no melanin
Red hair - trichosiderin
 Arrector pili muscle: group of smooth muscle tissues at
the base of the hair follicles causing short hairs to stand
11
on end when stimulated
 Figure 6.4
 B. Sebaceous glands (holocrine glands)




Associated with hair follicles
Secrete an oily mixture of fatty material and
other cellular debris called sebum
Small ducts into the hair follicle
Figure 6.6
12
 C. Nails





Protective coverings: ends of fingers & toes
Nail plate overlies skin surface called nail bed
Lunula – white, half-moon shaped, actively
producing new cells which are keratinized
Grow from epithelial cells at the base
Figure 6.7
13
 D. Sweat Glands (Sudoriferous glands)



Exocrine gland
Begins as ball-shaped coil in the deep dermis lined with
epithelial cells that secrete sweat; a tube elongates from
here to the surface
Most numerous sweat glands (eccrine glands) respond to
elevated body temperature (due to environment or exercise);
located forehead, neck, back



Other sweat glands (apocrine glands) become active when
individual is upset, frightened, in pain.


Opens in pore at skin surface
Mostly water, some waste, urea, uric acid
Numerous in axially region and groin
Some are more specialized - glands in the ear secrete wax
(ceruminous glands), mammary glands secrete milk
14
Click on the link and try the 4 labeling
exercises:
Labeling excercises 1 and 2
The average square inch of human skin
contains 650 sweat glands, 20 blood vessels,
60,000 melanocytes, in excess of 1,000
nerve endings.
15
IV. Regulation of Body Temp
 A. normal: 37 C or 98.6 F
 B. Metabolic rate drives internal body temperature; active
tissues/organs such as cardiac and skeletal muscle & liver
produce lots of heat
 C. Incr heat warms blood, when it reaches hypothalamus which
controls temp set point for body.
 Muscles in surface blood vessels relax causing vasodilation
 As warm blood enters these vessels, heat escapes to
surface
 Evaporative cooling occurs as sweat absorbs heat and
vaporizes from surface
 D. Shivering is a response to too much heat loss, response is to
rapidly increase cellular respiration producing heat as byproduct & increase muscle groups to contract rhythmically to
create more heat
 E. Figure 6.8 shows the feedback loop for temperature
regulation
16
V. Healing
 A. Inflammation: painful swelling around a wound due to blood




vessel dilation creating more fluid in the tissue
 Brings needed nutrients, oxygen, cells to aid healing
B. Superficial cuts/injury stimulate epithelial cells to divide
C. Deeper wounds often cause blood vessels to break, forming
clots (scab); fibroblasts migrate to injury forming collagenous
fibers to bind wound edges; a suture of superficial skin aids
healing
 Phagocytic cells “eat” dead tissue/debris
 New cells replace damaged cells, scar replaces scab
D. Granulations often form over large open wounds
 Consists of new blood supply, clusters of fibroblasts making
collagenous fibers to aid healing
 As healing proceeds, fibroblasts migrate away, new blood
supply resorbed, scar tissue left
E. Table 6.1
17