Download learning objectives

30 RESPIRATION
CHAPTER OUTLINE
LEARNING OBJECTIVES








List several diseases of the circulatory system.
List types of animal respiratory systems.
Discuss features of respiration in aquatic vertebrates.
Describe the features of the terrestrial vertebrate respiratory system.
Know the features of the mammalian respiratory system.
Discuss the mechanics of inhalation and exhalation.
Explain how the blood carries oxygen and carbon dioxide.
Cite evidence that suggests why smoking causes lung cancer.
Respiration (p. 574)
30.1
30.2
30.3
30.4
Types of Respiratory Systems (p. 574; Figs. 30.1, 30.2)
A. Aquatic animals respire using a variety of methods; some extract oxygen by diffusion directly
from the water, while others use gills.
B. Terrestrial arthropods employ a network of air ducts called tracheae, and terrestrial
vertebrates use lungs.
Respiration in Aquatic Vertebrates (p. 575; Fig. 30.3)
A. Aquatic vertebrates employ a countercurrent flow method of extracting oxygen from water in
which the flow of blood in gills is opposite to the flow of water past the gills.
B. This arrangement optimizes oxygen uptake.
Respiration in Terrestrial Vertebrates (p. 576; Figs. 30.4, 30.5)
A. Amphibians Get Oxygen from Air with Lungs
1. Amphibians exchange gases through their skin surface as well as using a simple lung.
B. Reptiles and Mammals Increase the Lung Surface
1. The lungs of reptiles contain tiny air chambers that greatly increase the surface area of
the lung and enhance air exchange.
2. The lungs of mammals possess tiny, thin-walled alveoli that are attached in clusters to
bronchioles.
3. Greater numbers of alveoli in very active mammals facilitate gas exchange.
C. Birds Perfect the Lung
1. Bird lungs are the most efficient of the land-dwellers because they achieve
countercurrent flow to maximize the exchange of oxygen and thus support their high
metabolic rate.
The Mammalian Respiratory System (p. 578; Figs. 30.6, 30.7)
A. The mammalian respiratory system consists of the lungs and bronchi.
B. Air passes in and out of the lungs, which are housed in the thoracic cavity.
C. Air is warmed and filtered as it flows through the nasal cavity.
D. It passes next through the larynx, or voice box, at the top of the trachea, or windpipe.
E. From there air is distributed throughout the bronchial tree into the lungs.
F. The tissue of the lungs is divided into tiny air sacs called alveoli; through these thin-walled
cells, air exchange with the blood occurs.
131
30.5
G. The lungs are covered by a thin pleural membrane that also lines the thoracic cavity.
H. Between the pleural membrane covering the lungs and that lining the chest cavity is a
lubricating interpleural fluid.
I. A muscular diaphragm separates the thoracic and abdominal cavities.
J. The Mechanics of Breathing
1. When the chest cavity expands, the two layers of pleura travel together, and the lungs are
also expanded.
2. During inhalation, the muscular diaphragm expands downward, and the chest muscles
move upward and outward, causing the chest cavity to expand; the lungs are drawn along
for the ride.
3. When the air pressure outside the lungs exceeds that within the lungs, air flows inward,
filling the lungs.
4. During exhalation, the diaphragm and chest muscles relax, causing the air pressure to
become greater inside the lungs than outside the body, and air is expelled from the lungs.
5. The depth and rate of breathing are controlled by the brain.
How Respiration Works: Gas Exchange (p. 580; Figs. 30.8, 30.9)
A. Oxygen is carried in the blood in conjunction with the hemoglobin molecules of the red blood
cells.
B. O2 Transport
1. Oxygen binds to hemoglobin as blood passes by the alveoli of the lungs.
2. As blood travels throughout the body, hemoglobin gives up its oxygen in areas where
oxygen is low.
3. The process of releasing oxygen is enhanced in metabolically active areas where carbon
dioxide is being generated.
a. The presence of CO2 causes hemoglobin to change shape and give up O2 more
readily.
4. This speeding up of oxygen release from the hemoglobin is called the Bohr effect.
C. CO2 Transport
1. Red blood cells absorb the carbon dioxide when they release their oxygen.
2. An enzyme called carbonic anhydrase combines with molecules of carbon dioxide so
they are not released into tissues where carbon dioxide is low.
3. The bound carbon dioxide dissociates into bicarbonate ions that do not diffuse out of the
blood.
4. Once back at the alveoli in the lungs, the carbon dioxide is given off and oxygen is taken
up once again.
D. NO Transport
1. Nitric oxide acts on many kinds of cells to change their shape and function.
2. Blood flow and blood pressure are regulated by the amount of NO released into the
bloodstream.
3. Hemoglobin carries NO in a form called super nitric oxide.
Lung Cancer and Smoking (p. 582)
30.6
The Nature of Lung Cancer (p. 582; Figs. 30.10, 30.11)
A. A host of environmental factors appears to be linked to lung cancer.
B. Mutations to two of the most important tumor-suppressor genes and the proteins they
produce, Rb and p53, are implicated in development of cancer.
C. The Rb Protein
1. The Rb protein acts as a break on cell division; mutations in the gene producing it cause
cell division to go out of control.
2. The p53 protein, also called the “Guardian Angel” of the cell, inspects the DNA to
make sure it is ready to divide.
3. When this protein detects damaged DNA, it normally activates the cell’s DNA repair
mechanisms and delays cell division.
4. About 50% of all cancers have a disabled p53 gene.
132
D. Smoking Causes Lung Cancer
1. Smoking cigarettes is a leading cause of lung cancer.
2. Many types of carcinogens (mutagens) found in cigarette smoke trigger changes in genes,
especially those that control the rate of cell division.
3. Cancer cells grow at rapid rates and often metastasize to surrounding, or even distant,
tissue.
4. Lung cancer kills two out of every 1,000 smokers each year, regardless of their ages.
KEY TERMS








countercurrent flow (p. 575) Aquatic vertebrates employ this method of extracting oxygen from water
in which the flow of blood in gills is opposite to the flow of water past the gills. This arrangement
optimizes oxygen uptake.
lung (p. 576) The lung is a bag-like respiratory organ that evolved in land animals.
alveoli (p. 576) Small sacs in the lungs through which gas exchange occurs.
diaphragm (p. 578) A muscular partition between the thoracic and abdominal cavities that aids in
breathing movements.
bicarbonate ions (p. 580) HCO3lung cancer (p. 582) Lung cancer is directly related to smoking cigarettes, among other causes.
Rb protein (p. 582) A protein that acts as a break on cell division.
p53 protein (p. 582) A tumor suppressor, nicknamed the “Guardian Angel” of the cell.
LECTURE SUGGESTIONS AND ENRICHMENT TIPS
1.
Tuberculosis. Tuberculosis is a disease of the lungs caused by the bacterium Mycobacterium
tuberculosis. Tubercles, or sacks of fibrous connective tissue, form in the lung around infected areas as
the body tries to wall off this organism. The infected individual may carry on this way for quite some
time or never go past this stage. Sometimes, however, the bacteria become widely spread throughout
the lungs, usually because the person has contracted another disease. Other symptoms of tuberculosis
include fever, fatigue, and weight loss. A chronic cough with bloody sputum is a hallmark of this
disease. In later stages, other bacteria begin infecting the lungs. Extensive destruction of lung tissue
makes it difficult for the person to feel as though he or she is getting enough air. Scar tissue develops in
the lungs, making gas exchange even more difficult. We often think of tuberculosis as a disease of the
past. Indeed, 100 years ago, tuberculosis caused one-third of the deaths of young adults in Europe.
Tuberculosis has not, however, gone away. In fact, it is becoming more widespread. Probably 20% of
the world's population, one billion people, are infected with this disease. And three million or more
people will die from tuberculosis this year, 12,000 or more from the United States alone. With the
rising AIDS epidemic, increased homeless population, and drug abuse, tuberculosis is increasing.
Antibiotic treatment can cure tuberculosis in the early stages of the disease, but antibiotic-resistant
strains are surfacing. Treatment during later stages is possible, but lung damage has often already
occurred. Better public health measures and sanitation are needed to slow the spread of this disease.
CRITICAL THINKING QUESTIONS
1.
2.
It is known that 2 out of 1000 smokers die of lung cancer annually, regardless of their age. Explain how
it is possible for young smokers to die from lung cancer.
Why is an arrangement of countercurrent flow in aquatic vertebrates not as necessary to optimize
oxygen retrieval from the air in most land-dwelling animals?
133