Emphysema is a chronic lung disease caused by loss of elasticity of the lung tissue. The destruction of elastic structures that support the alveoli and the capillaries that feed the alveoli cause them to become hard and stiff. Eventually the walls of the alveoli break down and the alveoli become larger. The amount of oxygen that can enter the blood with each breath is reduced because the large alveoli cannot function efficiently; much of the oxygen that gets into the large alveoli cannot be absorbed into the blood so the oxygen is unused. Symptoms include shortness of breath on exertion (usually when climbing stairs or a hill, and later at rest), and an expanded chest. Damage to the alveoli, which can be seen in Figure below, is irreversible. Smoking is a leading cause of emphysema.
Figure 22.38
The inside of a lung showing the characteristics of emphysema due to smoking. Instead of alveoli, the cut surface shows multiple cavities lined by heavy black carbon deposits.
Bronchitis is an inflammation of the bronchi. Acute bronchitis is usually caused by viruses or bacteria and may last several days or weeks. Acute bronchitis is characterized by cough and phlegm (mucus) production. Symptoms are related to the inflammation of the airways and phlegm production, and include shortness of breath and wheezing. Chronic bronchitis is not necessarily caused by infection and is generally part of a syndrome called chronic obstructive pulmonary disease (COPD). Chronic bronchitis is defined clinically as a persistent cough that produces phlegm and mucus, for at least three months in two consecutive years.
Figure 22.39
Asthma narrows the airways by causing allergy-induced spasms of surrounding muscles, narrowing of the airway, and excessive production of phlegm (mucus), which clogs the airways. The airway constriction responds to medicines called bronchodilators which relax the muscles. The feeling of breathlessness is somewhat like being able to breath only through a straw while walking.
Asthma is a chronic illness in which the airways narrow and becomes inflamed, as shown in Figure above. Excessive amounts of mucus are also made by the lungs. Asthma often happens in response to one or more triggers. It may be triggered by exposure to an allergen such as mold, dust, or pet hair. It can also be caused by cold air, warm air, moist air, exercise, or emotional stress. In children, the most common triggers are viral illnesses such as those that cause the common cold. This airway narrowing causes symptoms such as wheezing, shortness of breath, chest tightness, and coughing. Some people with asthma, especially children, can become very frightened by the symptoms, which may cause even more breathing distress. Between asthma attacks, most patients feel well but can have mild symptoms and may remain short of breath after exercise for longer periods of time than a person who does not have asthma. The symptoms of asthma, which can range from mild to life threatening, can usually be controlled with a combination of medicines and environmental changes.
Public attention in the developed world has recently focused on asthma because of the increasing numbers of cases, affecting up to one in four children who live in cities.
Pneumonia is an illness in which the alveoli become inflamed and flooded with fluid. Effective gas exchange cannot happen across the alveoli membranes. Pneumonia can result from a variety of causes, including infection with bacteria, viruses, fungi, or parasites, and chemical or physical injury to the lungs. Symptoms of pneumonia include cough, chest pain, fever, and difficulty in breathing. Treatment depends on the cause of pneumonia; bacterial pneumonia is treated with antibiotics.
Pneumonia is a common illness which occurs in all age groups, and is a leading cause of death among the elderly and people who are chronically and terminally ill. Vaccines to prevent certain types of pneumonia are available.
Tuberculosis (TB) is a common and deadly infectious disease caused by a type of bacteria called Mycobacterium tuberculosis. TB most commonly attacks the lungs (as pulmonary TB) but can also affect the central nervous system, the lymphatic system, the circulatory system, the genitourinary system, bones, joints and even the skin.
Over one-third of the world's population has been exposed to the TB bacterium. Not everyone infected develops the disease, so TB infection without symptoms (called a latent infection) is most common. However, one in ten latent infections will progress to active TB disease, which, if left untreated, kills more than half of its victims.
The rise in HIV infections and the neglect of TB control programs have led to an increase in cases of tuberculosis. The development of drug-resistant strains has also contributed to this new epidemic. For example, between 2000 and 2004, about 20 percent of TB cases were resistant to standard antibiotic treatments. TB incidence varies widely, even in neighboring countries, apparently because of differences in health care system standards. A TB vaccine, called Bacille Calmette-Guérin (BCG), is available to people in some countries. The BCG is prepared from a strain of weakened live mycobacterium, which has lost its virulence in humans. The effectiveness of the BCG is a matter of debate among researchers, and the governments in some countries, including the United States, do not require people to get the BCG vaccination.
Lung cancer is a disease where epithelial (internal lining) tissue in the lung grows out of control. This leads to invasion of nearby tissue and growth of the tumor beyond the lungs. Lung cancer, which is the most common cause of cancer-related death in men and the second most common in women, is responsible for 1.3 million deaths worldwide every year The most common symptoms are shortness of breath, coughing (including coughing up blood), and weight loss.
The most common cause of lung cancer is exposure to tobacco smoke. The occurrence of lung cancer in non-smokers, who account for less than 10 percent of cases, appears to be due to a combination of genetic factors. Radon gas, asbestos, and air pollution may also contribute to lung cancer.
Asbestos is a mineral that was once used as a fire retardant in buildings and electrical wiring. The inhalation of asbestos fibers can cause a variety of lung diseases, including lung cancer. Tobacco smoking and exposure to asbestos greatly increase a person’s chance of developing lung cancer.
Lesson Summary
The main functions of lungs are to obtain oxygen, and to release carbon dioxide. Oxygen is drawn in through the respiratory tract and is then delivered to the blood in a process called external respiration. The exchange of gases between the blood and the cells of the body is celled internal respiration.
The structures of the respiratory systems include the nose and nasal cavity, the pharynx, the larynx, ( also called the voicebox), the trachea (also called the wind pipe), the right and left bronchi in the lungs, and the bronchioles that end in the alveoli.
During inhalation, the diaphragm contracts, causing the volume of the chest cavity to increase. As a result, the air pressure within the lungs decreases. The pressure difference causes air to rush into the lungs. Relaxation of the diaphragm causes the lungs to recoil and air is pushed out of the lungs, which causes exhalation.
Most of the carbon dioxide (about 70 percent) in the blood is in the form of bicarbonate (HCO3-). A small amount of carbon dioxide dissolves in the water in the plasma to form carbonic acid (H2CO3). When CO2 enters the blood from body cells, it combines with water in the plasma to produce carbonic acid (H2CO3), which is then turned into bicarbonate (HCO3-). The bicarbonate is then picked up by a red blood cell and turned back in to carbonic acid. A water molecule (H2O) is then taken away from the carbonic acid, and the remaining CO2 molecule is expelled from the red blood cells and into the lungs.
Emphysema is a chronic lung disease caused by loss of elasticity of the lung tissue. The destruction of elastic structures that support the alveoli and the capillaries that feed the alveoli cause them to become hard and stiff. It is often caused by smoking. Asthma is also a chronic condition, which is often triggered by such things as exposure to an allergen, cold air, warm air, moist air, exercise, or emotional stress. The airways can constrict and become inflamed, and an excessive amount of mucus is produced. Airway narrowing causes symptoms such as w
heezing, shortness of breath, chest tightness, and coughing.
Review Questions
Identify the respiratory structures through which air flows.
How is the diaphragm involved in breathing?
Compare respiration and cellular respiration.
Outline how most carbon dioxide is carried in the blood.
Why is it important for a pregnant woman to know her Rhesus blood type, and the Rh blood type of the father of her baby?
What is the difference between internal and external respiration?
What happens during an asthma attack?
Outline how emphysema affects the absorption of oxygen.
Where does the exchange of oxygen occur in the lungs?
What factors regulate breathing rate?
Further Reading / Supplemental Links
http://www.estrellamountain.edu/faculty/farabee/biobk/BioBookRESPSYS.html
http://en.wikipedia.org
Vocabulary
alveoli
Multi-lobed sacs in which most of the gas exchange occurs.
asthma
A chronic illness in which the airways narrow and becomes inflamed.
bronchitis
An inflammation of the bronchi.
diaphragm
A muscle that is found below the lungs; contraction of the diaphragm causes the volume of the chest cavity to increase, and the air pressure within the lungs to decrease.
emphysema
A chronic lung disease caused by loss of elasticity of the lung tissue.
external respiration
Process in which oxygen is drawn in through the respiratory tract and is then delivered to the blood.
gas exchange
The diffusion of gases between the alveoli and the blood passing in the lung capillaries; also the diffusion of gases from capillaries into cells, and from cells into capillaries throughout the body (peripheral gas exchange).
internal respiration
The exchange of gases between the blood and the cells of the body.
larynx
Found just below the point at which the pharynx splits into the trachea and the esophagus; also called the voice box.
lung cancer
A disease where epithelial (internal lining) tissue in the lung grows out of control; leads to invasion of nearby tissue and growth of the tumor beyond the lungs.
lung volume (tidal volume)
The average breath capacity of a person.
obstructive
Conditions which lower the rate of the airflow into and out of the lungs, such as in asthma.
pharynx
A long tube that is shared with the digestive system; both food and air pass through the pharynx.
pneumonia
An illness in which the alveoli become inflamed and flooded with fluid.
respiration
The transport of oxygen from the outside air to the cells of the body, and the transport of carbon dioxide in the opposite direction.
respiratory acidosis
Condition in which arterial blood contains too much carbon dioxide, causing a drop in blood pH.
respiratory alkalosis
Condition which results from increased respiration (or hyperventilation) which causes a drop in the amount of carbon dioxide in the blood plasma; the drop in carbon dioxide concentration causes the blood pH to rise.
respiratory disease
The term for diseases of the lung, bronchial tubes, trachea and throat.
restrictive
Conditions that cause a reduction in the functional volume of the lungs, such as emphysema.
trachea
A long tube that leads down to the chest where it divides into the right and left bronchi in the lungs; also called the windpipe.
tuberculosis (TB)
A common and deadly infectious disease caused by a type of bacteria called Mycobacterium tuberculosis; most commonly attacks the lungs, but can also affect the central nervous system, the lymphatic system, the circulatory system, the genitourinary system, bones, joints and even the skin.
Points to Consider
How might the amount of oxygen in the air affect your respiratory and circulatory systems?
Can you identify any structures that are part of both the respiratory and digestive systems?
Chapter 23: Digestive and Excretory Systems
Lesson 23.1: Food and Nutrients
Lesson Objectives
Identify classes of macronutrients and describe their roles in the body.
Describe balanced eating and explain how it helps prevent obesity.
State functions and food sources of vitamins and minerals.
Describe eating disorders, their causes, and treatment.
Introduction
Did you ever hear the saying, “You are what you eat”? It’s not just a saying. It’s actually true. What you eat plays an important role in your health. Eating a variety of healthful foods promotes good physical health and provides energy for growth and activity. Many common diseases and their symptoms can be prevented or helped with healthful eating. Knowing what your body needs can help you choose foods to meet those needs.
Nutrients, Energy, and Building Materials
Nutrients are chemical elements or compounds that the body needs for normal functioning and good health. There are six main classes of nutrients: carbohydrates, proteins, lipids, water, vitamins, and minerals. The body needs these nutrients for three basic purposes: energy, building materials, and control of body processes.
A steady supply of energy is needed by cells for all body functions. Carbohydrates, proteins, and lipids provide this energy. Chemical bonds in molecules of these nutrients contain energy. When the bonds are broken during digestion to form simpler molecules, the energy is released. Energy is measured in units called kilocalories (kcal), commonly referred to as Calories.
Molecules that make up the body are continuously broken down or used up, so they must be replaced. Some nutrients, particularly proteins, provide the building materials for this purpose. Other nutrients—including proteins, vitamins, and minerals—are needed to regulate body processes. One way is by helping to form enzymes. Enzymes are compounds that control the rate of chemical reactions in the body.
Nutrients can be classified in two groups based on how much of them the body needs:
Macronutrients are nutrients that the body needs in relatively large amounts. They include carbohydrates, proteins, lipids, and water.
Micronutrients are nutrients the body needs in relatively small amounts. They include vitamins and minerals.
The exact amount of a macronutrient an individual needs depends on many factors, including gender and age. Recommended daily intakes of three macronutrients for young people of both genders are shown in Table below.
Recommended Daily Intakes of Carbohydrates, Proteins, and Water GenderAnd Age Carbohydrates(grams/day) Proteins(grams/day) Water*(liters/day)
Males 9–13 years 130 34 2.4
14–18 years 130 52 3.3
Females 9–13 years 130 34 2.1
14–18 years 130 46 2.3
Includes water in foods as well as beverages
Carbohydrates
Carbohydrates are organic (or carbon-containing) compounds consisting of the elements carbon, hydrogen, and oxygen. The elements are arranged in small molecules called saccharides. Carbohydrates are classified as either simple or complex, based on the number of saccharides they contain.
Simple carbohydrates contain just one or two saccharides. They are all sugars. Examples of sugars in the diet include fructose, which is found in fruit, and lactose, which is found in milk. The main function of simple carbohydrates is to provide the body with energy. One gram of carbohydrate provides four kilocalories of energy. Glucose is the sugar that is used most easily by cells for energy. It circulates in the blood, providing energy to cells throughout the body. Glucose is the only source of energy used by the brain.
Complex carbohydra
tes, called polysaccharides, generally contain many saccharides. They include starches and fiber. Starches are found in plant foods such as vegetables and grains. They are broken down during digestion to form sugars that provide energy. Fiber consists of indigestible starches and other materials such as cellulose. It is present in all plant foods.
Fiber may be soluble or insoluble.
Soluble fiber dissolves in water as it passes through the large intestine. It helps form substances that keep blood levels of glucose stable and blood levels of harmful lipids low (see below).
Insoluble fiber does not dissolve but attracts water as it passes through the large intestine. This helps keep waste moist and moving easily through the intestine.
Proteins
Proteins are relatively large organic compounds containing carbon, hydrogen, oxygen, and nitrogen. The elements are arranged in small molecules called amino acids. Amino acids are the building blocks of proteins. They bond together to form long chains, called polypeptides. Proteins consist of one or more polypeptides.
Proteins play many vital roles in the body, including:
Making up the majority of muscle tissue.
Regulating many body processes.
Forming antibodies that destroy bacteria and other “foreign invaders.”
CK-12 Biology I - Honors Page 112
