1. Biology Sylvia S. Mader Michael Windelspecht
Chapter 31
Animal Organization and Homeostasis
Lecture Outline
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2. 31.3 The Integumentary System
Biology, 9th ed, Sylvia Mader
Chapter 33
31.3 The Integumentary System
Animal Organization & Homeostasis
Functions of skin
Covers and protects underlying body regions
Regulates body temperature, and
Contains sensory receptors
Skin and its derivatives make up the integumentary system

3. The Integumentary System
Biology, 9th ed, Sylvia Mader
Chapter 33
The Integumentary System
Animal Organization & Homeostasis
Regions of the Skin
Epidermis - Outer, thinner region
Stratified squamous epithelium
New cells are pushed outward, become keratinized, and are sloughed off
Melanocytes produce melanin (pigment)
UV radiation can cause mutations in the DNA of skin cells, leading to skin cancer. 3

4. The Integumentary System
Biology, 9th ed, Sylvia Mader
Chapter 33
The Integumentary System
Animal Organization & Homeostasis
Regions of the Skin (cont.)
Dermis - Deeper and thicker than epidermis
Fibrous connective tissue containing elastic and collagen fibers contains:
Receptors
Nerve fibers
Blood vessels
Subcutaneous Layer - Loose, connective tissue located below dermis

5. The Integumentary System
Biology, 9th ed, Sylvia Mader
Chapter 33
The Integumentary System
Animal Organization & Homeostasis
Accessory Structures of Human Skin
Nails
Grow from nail root and form protective covering of distal portion of fingers and toes
Hair follicles
Begin in the dermis and continue through the epidermis
Contain oil glands (sebaceous glands) which secrete sebum
Lubricates the hair within the follicle as well as the skin
Sweat glands
Present in all regions of the skin
Begins in dermis and opens either to a hair follicle or to the surface of the skin
Functions to help maintain constant body temperature

6. Biology, 9th ed, Sylvia Mader
Chapter 33
Human Skin Anatomy
Animal Organization & Homeostasis
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
hair shaft
sweat pore
Epidermis
melanocytes
sensory receptor
capillaries
oil gland
arrector pili muscle
Dermis
free nerve endings
hair follicle
hair root
sweat gland
artery
Subcutaneous layer
vein
nerve
adipose tissue

7. Biology, 9th ed, Sylvia Mader
Chapter 33
The Epidermis
Animal Organization & Homeostasis
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
flattened and
dead cells
Epidermis
b. Basal cell
carcinoma
cells undergoing
keratinization
stem cells
and melanocytes
dermal
projection
Dermis
a. Photomicrograph of skin
c. Melanoma
a: © John D. Cunningham/Visuals Unlimited; b: © Ken Greer/Visuals Unlimited; c: © James Stevenson/SPL/Photo Researchers, Inc.

8. Biology, 9th ed, Sylvia Mader
Chapter 33
31.4 Homeostasis
Animal Organization & Homeostasis
The organ systems of the human body contribute to homeostasis
The ability of an organism to maintain a relatively constant internal environment
Animals vary to the degree in which they can regulate internal variables.

9. Biology, 9th ed, Sylvia Mader
Chapter 33
Homeostasis
Animal Organization & Homeostasis
The organ systems of the human body contribute to homeostasis
The digestive system
Takes in and digests food
Provides nutrient molecules that replace used nutrients
The respiratory system
Adds oxygen to the blood
Removes carbon dioxide
The liver and the kidneys
Store excess glucose as glycogen
Later, glycogen is broken down to replace the glucose used
The hormone insulin regulates glycogen storage
The kidneys
Under hormonal control as they excrete wastes and salts

10. Biology, 9th ed, Sylvia Mader
Chapter 33
Homeostasis
Animal Organization & Homeostasis
Homeostatic Control
Partially controlled by hormones
Ultimately controlled by the nervous system
Negative feedback is the primary homeostatic mechanism that keeps a variable close to a set value
Sensor detects change in environment
Regulatory center initiates an action to bring the conditions back to normal

11. Regulation of Room Temperature Using Negative Feedback
Biology, 9th ed, Sylvia Mader
Regulation of Room Temperature Using Negative Feedback
Chapter 33
Animal Organization & Homeostasis
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Control center
sends data to
thermostat
directs furnace
to turn off
68°F set point
Sensor
70°F
too hot
furnace off
negative feedback
and return to
normal temperature
stimulus
too hot
Homeostasis
too cold
negative feedback
and return to
normal temperature
stimulus
Sensor
furnace on
66°F
too cold
Control center
directs furnace
to turn on
sends data to
thermostat 11
68°F set point

12. Regulation of Body Temperature by Negative Feedback
Biology, 9th ed, Sylvia Mader
Chapter 33
Regulation of Body Temperature by Negative Feedback
Animal Organization & Homeostasis
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Control center
sends data to
control center
98.6°F set point
directs response
to stimulus
Sensor
Effect
Blood vessels dilate;
sweat glands secrete.
negative feedback
and return to normal
temperature
stimulus
above normal
Normal body temperature
below normal
negative feedback
and return to normal
stimulus
Effect
Sensor
Blood vessels constrict;
sweat glands are inactive.
Control center
directs response
to stimulus
sends data to
control center
98.6°F set point

13. Biology, 9th ed, Sylvia Mader
Chapter 33
Homeostasis
Animal Organization & Homeostasis
Positive feedback is a mechanism that brings about an ever greater change in the same direction
Childbirth process
Positive Feedback
Does not result in equilibrium
Does not occur as often as negative feedback

14. Biology, 9th ed, Sylvia Mader
Chapter 33
Positive Feedback
Animal Organization & Homeostasis
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
2. Signals cause pituitary gland to
release the hormone oxytocin.
As the level of oxytocin increases,
so do uterine contractions
until birth occurs.
pituitary gland + +
uterus
1. Due to uterine contractions,
baby’s head presses on
cervix, and signals are
sent to brain.