1. Unifying Concepts of Animal Structure and Function
Chapter 20
Unifying Concepts of Animal Structure and Function

2. THE HIERARCHY OF STRUCTURAL ORGANIZATION IN AN ANIMAL
20.1 Structure fits function in the animal body
Anatomy is the study of structure
Physiology studies how structures function
The functions of the various parts of the body result from their specific structures
Example: Flight apparatus of birds provides strength, support, insulation, stability, minimal weight
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

3. 20.2 Animal structure has a hierarchy
Structure in the living world is organized in a series of hierarchical levels
Cell: smallest independent unit of life
Tissue: integrated group of cells that perform a specific function
Organ: two or more types of tissues that together perform a specific task
Organ system: multiple organs that together perform a vital body function
Organism: integrated unit made up of a number of organ systems functioning together

4. LE 20-02 Cellular level Muscle cell Tissue level Muscle tissue
Organ level
Heart
Organ system level
Circulatory system
Organism level
Many organ systems
functioning together

5. 20.3 Tissues are groups of cells with a common structure and function
The cells composing a tissue are specialized to perform a specific function
In almost all animals, most body cells are organized into four main categories of tissues
Epithelial
Connective
Muscle
Nervous

6. 20.4 Epithelial tissue covers the body and lines its organs and cavities
Epithelial tissue occurs as sheets of closely packed cells anchored to underlying tissues by a basement membrane
Categories of epithelial tissues
Simple: single layer of cells
Stratified: multiple layers of cells
Shapes: squamous, cuboidal, or columnar
Epithelial tissue functions in protection, secretion, and exchange

7. LE 20-04 Free surface of epithelium Basement membrane Cell nuclei
Underlying
tissue
Simple squamous epithelium
(lung)
Stratified squamous epithelium
(esophagus)
Simple cuboidal epithelium
(kidney)
Layers of
dead cells
Rapidly dividing
epithelial cells
Colorized SEM
Stratified squamous
epithelium (skin)
Simple columnar epithelium
(intestine)

8. 20.5 Connective tissue binds and supports other tissues
The various types of connective tissue consist of sparse cells in an extracellular gel matrix
Loose connective tissue
Fibrous connective tissue
Adipose tissue
Cartilage
Bone
Blood

9. LE 20-05 Fat droplets Cartilage- forming cells Adipose tissue Matrix
nucleus
Cartilage
(at the end of a bone)
Collagen
fiber
Central
canal
Fibrous connective
tissue (forming a
tendon)
White blood
cells
Matrix
Cell
Bone-
forming
cells
Red blood
cell
Collagen fiber
Elastic fibers
Bone
Plasma
Loose connective
tissue (under the skin)
Blood

10. 20.6 Muscle tissue functions in movement
Muscle tissue consists of bundles of long cells called muscle fibers
Skeletal muscle is responsible for voluntary body movements
Cardiac muscle forms the contractile tissue of the heart
Smooth muscle moves the walls of internal organs such as the stomach, bladder, and arteries

11. LE 20-06 Unit of Muscle muscle Muscle fiber contraction Junction fiber
between
two cells
Nucleus
Nucleus
Muscle fiber
Nucleus
Cardiac muscle
Skeletal muscle
Smooth muscle

12. 20.7 Nervous tissue forms a communication network
Nervous tissue senses stimuli and rapidly transmits information through the body
The neuron is the structural and functional unit of nervous tissue
Specialized to conduct electrical impulses
Consists of cell body, axon, and dendrites
Nourished by supporting cells

13. LE 20-07
Cell body
Nucleus
Cell extensions
LM 330

14. 20.9 Organs are made up of tissues
Each organ is made of several tissues that collectively perform specific functions
In some organs, tissues are arranged in layers
An organ performs functions that none of its component tissues could carry out alone

15. LE 20-09 Small intestine Lumen (cut open) Lumen Epithelial tissue
(columnar epithelium)
Connective tissue
Smooth muscle
tissue (2 layers)
Connective tissue
Epithelial tissue

16. 20.10 Organ systems work together to perform life functions
There are twelve major organ systems in vertebrate animals
Digestive system
Respiratory system
Circulatory system
Immune system
Lymphatic system

17. Excretory system
Endocrine system
Nervous system
Integumentary system
Skeletal system
Muscular system
Reproductive systems

18. Digestive system Mouth Esophagus Liver Stomach Small intestine Large
LE 20-10a
Digestive system
Mouth
Esophagus
Liver
Stomach
Small
intestine
Large
intestine
Anus

19. LE 20-10b
Respiratory system
Nasal cavity
Larynx
Trachea
Bronchus
Lung

20. LE 20-10c
Circulatory system
Heart
Blood
vessels

21. Immune system Lymphatic system Bone marrow Thymus Spleen Lymph nodes
LE 20-10d-e
Immune system
Lymphatic system
Bone marrow
Thymus
Spleen
Lymph nodes
Lymph vessels

22. LE 20-10f
Excretory system
Kidney
Ureter
Urinary
bladder
Urethra

23. Endocrine system Pituitary gland Thyroid gland Thymus Adrenal gland
LE 20-10g
Endocrine system
Pituitary
gland
Thyroid
gland
Thymus
Adrenal
gland
Pancreas
Testis
(male)
Ovary
(female)

24. LE 20-10h
Nervous system
Brain
Sense
organ
Spinal
cord
Nerves

25. LE 20-10i
Integumentary system
Hair
Skin
Nails

26. LE 20-10j
Skeletal
system
Cartilage
Bones

27. LE 20-10k
Muscular
system
Skeletal
muscles

28. Reproductive system Male Female Prostate gland Vas deferens Oviduct
LE 20-10l
Reproductive system
Male
Female
Prostate
gland
Vas
deferens
Oviduct
Urethra
Ovary
Penis
Uterus
Testis
Vagina

29. 20.13 Animals regulate their internal environment
The internal environment of a vertebrate is the interstitial fluid surrounding the cells
In response to changes in external conditions, animals regulate their internal environment to achieve homeostasis, an internal steady state
Homeostasis is a dynamic state with constant small fluctuations

30. External environment Internal environment Homeostatic mechanisms Small
LE 20-13b
External
environment
Internal
environment
Homeostatic
mechanisms
Small
fluctuations
Large
fluctuations

31. 20.14 Homeostasis depends on negative feedback
In negative feedback, a change in a variable triggers mechanisms that reverse the change
Negative feedback mechanisms keep internal variables fairly constant, with small fluctuations around set points
In animals, most control centers that maintain homeostasis are located in the brain

32. LE 20-14 Sweat glands secrete sweat that evaporates, cooling body
Thermostat in brain
activates cooling
mechanisms
Blood vessels in
skin dilate and
heat escapes
Temperature rises
above normal
Thermostat shuts off
cooling mechanisms
Temperature decreases
Homeostasis:
Internal body temperature
of approximately 3638C
Temperature
increases
Thermostat shuts off
warming mechanisms
Temperature falls below normal
Blood vessels in skin
constrict, minimizing
heat loss
Thermostat in
brain activates
warming
mechanisms
Skeletal muscles rapidly
contract, causing shivering,
which generates heat