Mastering Concepts
24.1
1. What is the difference between anatomy and physiology?
Anatomy is the study of the physical arrangement of the body’s parts; physiology
explains how those parts function.
2. What is the relationship among cells, tissues, organs, and organ systems?
Specialized cells form tissues. Multiple tissues working together form organs, and organ
systems are groups of related organs that interact to produce a specific body process.
3. Trace the body’s early development from one fertilized egg to a many-celled organism.
A fertilized egg divides to form a blastula. Then one end of the hollow ball of cells
pushes inward, forming a gastrula with three primary tissue layers. Each tissue layer
contributes to several organs that are related in organ systems.
24.2
1. List the four main tissue types in animal bodies.
Connective, epithelial, nervous, and muscle
2. Where do epithelial tissues occur, and how are they named?
Epithelial tissues line the interior and exterior surfaces of the body. These tissues are
named for their cell shapes and number of layers.
3. List and describe six types of connective tissue.
The six types of connective tissue are:
- Loose connective tissue: fibroblasts and white blood cells in a matrix of elastin and
collagen fibers.
- Dense connective tissue: fibroblasts held in a matrix of dense elastin and collagen
fibers.
- Adipose tissue: fat cells embedded in a small amount of extracellular matrix.
- Blood: red and white blood cells and platelets suspended in a liquid matrix called
plasma.
- Cartilage: chondrocytes in a network of fine collagen fibers.
- Bone: bone cells held within a matrix composed of collagen and minerals.
4. Explain the similarities and differences among the three types of muscle tissue.
All three types of muscle tissue contract by sliding actin filaments across myosin.
Differences between the three muscle types include:
- skeletal muscle: cells have many nuclei and have a striated appearance. Skeletal muscle
is under voluntary control, and most of it attaches to bone.
- smooth muscle: each cell has one nucleus and no striations. Smooth muscle forms part
of many internal organs and is under involuntary control.
- cardiac muscle: cells are striated and each contains one nucleus. Cardiac muscle cells
are connected electrically so that they contract simultaneously. Cardiac muscle forms
much of the heart and is under involuntary control.
5. What are the two main cell types in nervous tissue?
The two main cell types in nervous tissue are neurons and neuroglia.
24.3
1. Which organ systems contribute to each of the five general functions of life?
Here are the five general functions of life and the organ systems that primarily contribute
to them:
Communication: nervous and endocrine systems
Movement and support: muscular and skeletal systems
Acquiring energy: circulatory, respiratory, and digestive systems
Protection: integumentary, urinary, and immune systems
Reproduction: reproductive system (although all systems contribute indirectly to this
function).
2. What are some examples of interactions between organ systems?
Examples of interactions between organ systems include:
- the circulatory system brings blood to the urinary system, where the blood is cleansed.
Fluids then return to the circulatory system. The functions of the urinary system are
monitored by endocrine glands and controlled by hormones.
- the respiratory system exchanges gases with the bloodstream. The nervous system
monitors the breathing rate, which is under the control of voluntary muscles and
involuntary muscles. The breathing rate is also influenced by hormones.
- the digestive system breaks food down into particles that are absorbed into the
bloodstream and carried to cells that need nutrients (or stored in the liver and in fat
deposits). The digestive system is controlled by hormones and influenced by the nervous
system.
24.4
1. Which fluids are part of the body’s internal environment?
Interstitial fluids form part of the body’s internal environment.
2. What is homeostasis?
Homeostasis is the state of internal constancy in the face of a changing environment.
3. What happens to an organism that fails to maintain homeostasis?
An organism that fails to maintain homeostasis will stop functioning and will eventually
die.
4. Distinguish between negative and positive feedback.
In negative feedback, the product of a process turns off its own production. In positive
feedback, the product of a process stimulates its own production.
24.5
1. How does the integumentary system help the body maintain homeostasis?
The integumentary system blocks the entry of foreign organisms and foreign objects into
the body. It also prevents the loss of body fluids and helps to maintain body temperature
through the constriction and dilation of blood vessels and erection of hair or feathers in
animals that have them. The production of vitamin D in skin helps to keep the skeleton
strong.
2. What tissue types occur in each layer of human skin?
The layers of human skin and the tissue types they are made of are:
- epidermis: made of stratified squamous epithelium;
- dermis: made of dense connective tissue.
3. What are some examples of specialized cells of the epidermis and dermis?
Specialized cells of the epidermis include keratinocytes that produce keratin and
melanocytes that produce melanin and affect the skin’s color. Examples of specialized
cells of the dermis include those that make up the hair follicles, sweat glands, mammary
glands, and sebaceous glands.
24.6
1. Describe how folic acid and vitamin D nutrition might explain the variation in
human skin pigmentation.
Deficiencies in vitamin D can cause death or pelvic deformities. Deficiencies in folic
acid can lead to infertility in men or birth defects in pregnant women. Therefore
deficiencies in both vitamins affect a population through the reproductive years when
selective pressures have an effect. Because UV light affects concentrations of the two
vitamins conversely (low UV results in lower vitamin D concentrations, but low UV
results in higher folic acid concentrations) selection for pigmentation probably represents
an evolutionary trade-off between maximizing the two vitamins. As populations
migrated to more northern latitudes, the selective pressure on melanin production
lessened while selection for vitamin D synthesis increased.
2. Why do you think people who migrate from the tropics to urban areas in northern
latitudes are at high risk for vitamin D deficiency? How might they decrease the risk?
People originally from the tropics most likely have a high concentration of melanin
expression in their skin. This melanin blocks their absorption of the little UV present and
hinders the production of vitamin D. They could lower their risks for vitamin D
deficiency by taking supplements and exposing themselves to special UV lamps.
Write It Out
1. Distinguish between:
a. organs and organ systems
b. simple squamous and stratified squamous epithelial tissue
c. loose and dense connective tissue
d. skeletal and cardiac muscle tissue
e. neurons and neuroglia
f. negative and positive feedback
a) Organs are the individual structures that function together to make up an organ
system. b) Stratified squamous epithelial tissue contains more than one layer of
cells, whereas simple squamous epithelium contains just one layer. C) Loose
connective tissue binds tissues together and fills spaces, whereas dense connective
tissue builds ligaments and tendons. D) Skeletal muscle tissue is voluntary and
has long cells, whereas cardiac muscle is involuntary, and has electrically
connected short cells. E) Neurons are the communicating cells of the nervous
system, whereas neuroglia are the supporting cells.
2. Marfan syndrome (see chapter 10) and osteogenesis imperfecta are two examples of
heritable disorders of connective tissue. Use the Internet to learn about these two
diseases. Why do people with connective tissue disorders have many interrelated
symptoms?
Connective tissue disorders cause many symptoms because connective tissues occur
throughout the body.
3. What is homeostasis, and how is it important?
Homeostasis is a state of internal constancy. Cells and tissues must have conditions
within a certain range if they are to function. If the body system cannot maintain
homeostasis, it may stop functioning, and the organism may die.
4. When a person gets cold, he or she may begin to shiver. If the weather is too hot, the
heart rate increases and blood vessels dilate, sending more blood to the skin. How does
each scenario illustrate homeostasis?
Shivering is the involuntary contraction of skeletal muscles; the muscle movement
produces heat, which helps increase the body temperature. In the second scenario, blood
passing near the skin surface releases heat to the atmosphere, which helps cool the
overheated body. Both examples illustrate how the body maintains a constant
temperature.
5. Observe what happens to the size of your eye’s pupil when you leave a dark room and
enter the sunshine. What happens in the opposite situation, when you enter a dark room?
How do the opposing reactions of your eye illustrate negative feedback?
When the light levels reaching the eye’s sensory cells are very high the pupil constricts.
This lets in less light and counters the original stimulus. If you then enter a dark room
where less light reaches the eye, then the pupils will dilate. This will let in more light and
again counters the original stimulus.
6. Which tissues make up skin, the largest organ of the body? How do these tissues
interact to provide each of the functions of skin? Describe at least one interaction
between skin and each of the 10 other organ systems.
The epidermis contains stratified squamous epithelial tissue. The dermis contains
connective tissue, smooth muscle tissue and nervous tissue. These tissues allow the body
to maintain temperature homeostasis as nerves in the skin detect temperature and send the
information to the hypothalamus. For example, if the body is too hot then blood vessels
will dilate and sweat glands will open. This will bring the body temperature back to
normal. The skin also plays a homeostatic role in water balance, nutrition, and defense
against disease. Interactions between the skin and the other 10 systems include:
Nervous—sensory receptors in the skin are part of the nervous system and detect stimuli
Endocrine—the endocrine system produces the hormone that stimulates melanin
production in the skin
Skeletal—the skin absorbs UV light and produces vitamin D, which indirectly influences
bone structure
Muscular—muscle fibers that attach to the dermis produce facial expressions
Digestive—vitamin D in the skin helps regulate calcium and phosphorus needed for
proper nutrition
Circulatory—blood vessels in the skin constrict and dilate to maintain temperature
homeostasis
Respiratory—the respiratory system exchanges the needed O2 with the CO2 waste from
skin cells
Urinary—the loss of body water through the skin is countered by water retention in the
urinary system
Immune/lymphatic—the skin acts a first line of defense to keep out pathogens
Reproductive— mammary glands in the skin produce the milk necessary for lactation
7. How would you design an experiment to determine whether a new brand of artificial
skin is safe for use in humans?
A group of human volunteers could be divided into two groups. One group would
receive a small square of artificial skin; a control group would receive a similar surgery
but without artificial skin. Researchers could test for toxicity to nearby tissues, allergic
reactions, or immune system rejection.
8. Make a chart that compares and contrasts the organization of the animal body with that
of a plant (see chapter 21).
Organization Level
Cells
Tissues
Organs
Animals
many specialized cell types
Epithelial Tissue
Connective Tissue
Muscle Tissue
Nervous Tissue
Many organs
Organ Systems
11 organ systems
Plants
8 specialized cell types
Ground Tissue
Dermal Tissue
Vascular Tissue
Vegetative: root, stem,
leaves
Reproductive: fruit, flowers,
seeds
No organ systems
Pull It Together
1. What features distinguish the four types of tissue?
The epithelial tissues make wall-like tissue layers that surround all the organs and make
up the skin. The connective tissues are organized groups of hard, strong, and sticky cells
that hold organs together and provide structural support. The cells that make up muscle
tissue are elongated and synchronize their activity to contract. Muscle contraction moves
our skeleton and allows our internal organs to function. The nervous tissues are cells that
come in a huge variety of shapes and perform electrochemical communication.
2. Add the specific types of epithelial, connective, muscle, and nervous tissue to this
concept map.
“Epithelial” connects with “includes” to “Simple squamous”, “Simple cuboidal”, “Simple
columnar”, “Stratified squamous”, “Stratified cuboidal”, and “Pseudostratified
columnar”. “Connective” connects with “includes” to “Loose connective tissue”, “Dense
connective tissue”, “Adipose tissue”, “Blood”, “Cartilage”, “Bone”. “Muscle” connects
with “includes” to “Skeletal muscle”, “Cardiac muscle”, and “Smooth muscle”.
“Nervous” connects with “includes” to “Neurons” and “Neuroglia”.
3. Add the 11 organ systems to this concept map.
All connections made with “is carried out by”.
“Communications” connects to “Nervous system” and “Endocrine system”.
“Support and movement” connects to “Skeletal system” and “Muscular system”
“Energy acquisition” connects to “Digestive system”, “Circulatory system” and
“Respiratory system”.
“Protection” connects to “Urinary system”, “Integumentary system”, and
“Immune/Lymphatic system”
“Reproduction” connects to “Reproductive system”
4. Describe examples of organ system interactions that maintain homeostasis.
Organ systems interact in a variety of ways to maintain homeostasis For example, the
brain monitors levels of carbon dioxide in the blood. When these levels are too high, the
autonomic nervous system signals the lungs to increase breathing rates, returning the
oxygen-carbon dioxide ratio to normal.