Men have a higher rate of cardiovascular disease than women do, but it is the number one health problem for women in industrialized countries. The risk for older women (in late adulthood) is almost equal that of older men.
Cardiovascular Disease Awareness: What You Can Do
Being active every day and eating healthfully are two of the most important things you can do to maintain a healthy cardiovascular system. Avoiding tobacco is also very important. You do not to be on a sports team or join a gym to be physically active. For example, shooting hoops at your school or local basketball courts can help keep your heart healthy. Aerobic activities are activities that cause your heart to beat faster and allow your muscles to use oxygen to get energy to contract. When done regularly, aerobic activities increase the size of the heart so it pumps blood around the body more efficiently. Aerobic activities also help to keep blood vessels healthy. To stay healthy, teens and children should be active for at least 60 minutes most days of the week.
Limiting the amount of saturated fat in your diet can also keep your heart healthy. Saturated fats are found in dairy foods, meats, cookies, pies, some chocolates, and ice cream. Saturated fats are usually solid at room temperature. Fat gives food flavor and texture. Saturated fats occur naturally in foods that come from animals, such as meat and milk, but they are often added to baked products such as cookies, shown in Figure below, to give the foods flavor and texture. Not all fats are harmful to the cardiovascular system. Fats called monounsaturated and polyunsaturated fats are needed by the body, and should make up most of the fats that you eat in your diet. Monounsaturated and polyunsaturated fats are found in plants and fish, and are usually liquid at room temperature. To learn more about the importance of fats in your diet, read the Choosing Healthful Foods lesson of the Food and the Digestive System chapter.
Figure 18.25
The USDAs MyPyramid recommends that you limit the amount of such foods in your diet to occasional treats; some foods containing saturated fats may contain other nutrients.
Cardiovascular diseases are called lifestyle diseases because they are caused mostly by everyday choices that people make, such as what to eat for dinner, or what to do during their free time. For example, watching TV with your dog does not involve much moving around so it does not exercise the body, whereas bringing the dog for a walk outside exercises both of you. Decisions that you make today and everyday - those of developing healthy lifelong habits - will affect your cardiovascular health many years from now.
Many studies have shown that plaque build-up starts in the teen years. However, teens are more concerned about risks such as HIV, accidents, and cancer than cardiovascular disease. One in three people will die from complications due to atherosclerosis. For this reason there is an emphasis on the prevention of CVD through risk reduction. For example, healthy eating, regular physical activity, and avoidance of smoking can greatly decrease a person’s chance of developing a CVD.
Lesson Summary
Blood pressure is the force exerted by circulating blood on the walls of blood vessels. The force of the contractions put the blood under pressure. Blood pressure is measured by an instrument called a sphygmomanometer.
In the United States the healthy ranges for systolic pressure is less than 120 mm Hg and a diastolic pressure of less than 80 mm Hg. Hypertension is a condition in which a person’s blood pressure is always high.
A cardiovascular disease (CVD) is any disease that affects the cardiovascular system. Atherosclerosis, coronary heart disease, and stroke are examples of CVDs.
Cardiovascular diseases are lifestyle diseases, they are mostly caused by lifestyle choices that people make. Having a poor diet and not getting enough exercise are two major causes of CVD.
Further Reading / Supplemental Links
http://mypyramid.gov http://www.presidentschallenge.org/; http://mypyramid.gov
http://www.cdc.gov/youthcampaign/marketing/tweens/yellowball/index.htm
http://www.cdc.gov/nccdphp/dnpa/physical/everyone/recommendations/index.htm
http://www.cdc.gov/bloodpressure http://en.wikipedia.org/wiki/Aerobic_exercise; http://www.cdc.gov/bloodpressure
Review Questions
What is the cause of blood pressure?
How is the pulse related to blood pressure?
Is the blood in veins under pressure? Explain your answer.
What is the healthy range for blood pressure?
When is a person considered to have hypertension?
Why is hypertension called a silent killer?
A stroke is often called a brain attack, in a similar way to a heart attack. How are these two things similar?
What is atherosclerosis?
What is a risk factor?
What is the difference between a controllable risk factor and an uncontrollable risk factor?
Why are cardiovascular diseases called lifestyle diseases?
Identify three things a person could do to reduce their chances of developing a CVD.
Vocabulary
angina
Chest pain caused by the lack of oxygen to the heart muscle; can happen during times of stress or physical activity.
atherosclerosis
A chronic inflammation of the walls of arteries that causes swelling and a buildup of material called plaque.
blood pressure
The force exerted by circulating blood on the walls of blood vessels.
cardiovascular disease (CVD)
Any disease that affects the cardiovascular system, although the term is usually used to describe diseases that are linked to atherosclerosis.
coronary heart disease
The end result of the buildup of plaques within the walls of the coronary arteries.
heart attack
Event that occurs when the blood supply to a part of the heart is blocked.
hypertension
Also called high blood pressure; a condition in which a person’s blood pressure is always high; the systolic blood pressure is always 140 mm Hg or higher, and/or their diastolic blood pressure is always 90 mm Hg or higher.
plaque
Cell pieces made up of fatty substances, calcium, and connective tissue that build up around the area of inflammation; builds up on the lining of blood vessels.
risk factor
Anything that is linked to an increased chance of developing a disease or an infection.
stroke
A loss of brain function due to a blockage of the blood supply to the brain.
Points to Consider
Do you think there is a relationship between the cardiovascular system and the respiratory system? What could it be?
Do you think hypertension affects the ability of the blood to release carbon dioxide and pick up oxygen in the lungs? Why?
Chapter 19: Respiratory and Excretory Systems
Lesson 19.1: Respiratory System
Lesson Objectives
Identify the parts of the respiratory system.
Identify the main function of the respiratory system.
Describe how breathing works.
Outline how the respiratory system and the cardiovascular system work together.
Identify how breathing and cellular respiration are connected.
Check Your Understanding
What is an organ system?
What is the role of the circulatory system?
How does your blood get oxygen?
Introduction
You breathe mostly without thinking about it. But, do you remember how uncomfortable you felt the last time you had a cold or a cough? You usually do not think about your respiratory system or how it works until there is a problem with it. Every cell in your body depends on your respiratory system. In this lesson, you will learn how your respiratory system works with your cardiovascular system to bring oxygen to every cell in your body.
Roles of the Respiratory System
Your respiratory system is made up of the tissues and organs that allow oxy
gen to enter and carbon dioxide to leave your body. These structures include your nose, mouth, larynx, pharynx, lungs, and diaphragm. These structures are shown in Figure below. The main function of the respiratory system is to bring oxygen into the body and release carbon dioxide into the atmosphere.
Figure 19.1
The respiratory system; air moves in through the nose and mouth, and down the trachea which is a long straight tube in the chest.
Parts of the Respiratory System
Figure 1 shows many of the structures of the respiratory system. Each of the parts has a specific job. The parts of the respiratory system include:
The diaphragm is a sheet of muscle that extends across the bottom of the rib cage. It performs an important function in respiration. When the diaphragm contracts the chest volume gets larger and the lungs take in air. When the diaphragm relaxes, the chest volume gets smaller and air is pushed out of the lungs.
The nose and nasal cavity filters, warms, and moistens the inhaled air. The nose hairs and mucus produced by the cells that line the nose catch airborne particles and prevent them from reaching the lungs.
Behind the nasal cavity, air next passes through the pharynx, a long tube that is shared with the digestive system. Both food and air pass through the pharynx. A flap of connective tissue called the epiglottis closes over the trachea when food is swallowed to prevent choking or inhaling food.
The larynx, also called the voicebox, is found just below the point at which the pharynx splits into the trachea and the esophagus. Your voice comes from your larynx. Air from the lungs passes across thin membranes in the larynx and produces sound.
The trachea, or wind pipe, is a long tube that leads down to the chest where it divides into the right and left bronchi in the lungs. The bronchi branch out into smaller bronchioles in each lung.
The bronchioles lead to the alveoli. Alveoli are the little sacs at the end of the bronchioles. They look like little bunches of grapes at the end of the bronchioles, as shown in Figure below. Most of the gas exchange occurs in the alveoli. Gas exchange is the movement of oxygen across a membrane and into the blood and the movement of carbon dioxide out of the blood.
Figure 19.2
The alveoli are the tiny grape-like structures in the lungs and the sites of gas exchange.
How We Breathe
Most of the time, you breathe without thinking of it. Breathing is mostly an involuntary action that is controlled by a part of your brain that also controls your heart beat. If you swim, do yoga, or sing, you know you can also control your breathing.
Figure 19.3
Being able to control breathing is important for many activities, such as swimming. The man in the photograph is exhaling before he surfaces the water.
Taking air into the body through the nose and mouth is called inhalation. Pushing air out of the body through the nose or mouth is called exhalation. The man in Figure above is exhaling before he surfaces in the pool water. The lungs cannot move by themselves. As mentioned above, air moves into and out of the lungs by the movement of muscles. The diaphragm and rib muscles contract and relax to move air into and out of the lungs.
During inhalation, the diaphragm contracts and moves downward. The rib muscles contract and cause the ribs to move outward. This causes the chest volume to increase. Because the chest volume is larger, the air pressure inside the lungs is less than the air pressure outside. This difference in air pressures causes air to be sucked into the lungs. When the diaphragm and rib muscles relax, air is pushed out of the lungs. Exhalation is normally a passive process, similar to letting the air out of a balloon.
The walls of the alveoli are very thin and are permeable to gases. The alveoli are lined with capillaries, the walls of which are also thin enough to allow gas exchange. These capillaries are shown in Figure below. Oxygen diffuses from the alveoli to the blood in the capillaries that surround the alveoli. At the same time, carbon dioxide diffuses in the opposite direction, from capillary blood to the alveoli. At this point, the pulmonary blood is oxygen-rich, and the lungs are holding carbon dioxide. Exhalation follows, thereby ridding the body of the carbon dioxide and completing the cycle of respiration.
Figure 19.4
The bronchi and alveoli; during respiration, oxygen gets pulled into the lungs and enters the blood by passing across the thin alveoli membranes and into the capillaries.
Breathing and Respiration
When you breath in, oxygen is drawn in through the mouth and down into the lungs. The oxygen then passes across the thin lining of the capillaries and into the blood. The oxygen molecules are carried to the body cells by the blood. Carbon dioxide from the body cells is carried by the blood to the lungs where it is released into the air. The process of getting oxygen into the body and releasing carbon dioxide is called respiration.
Sometimes breathing is called respiration. But, there is much more to respiration than just breathing. There are actually two parts to respiration. The movement of oxygen into the body and carbon dioxide out of the body is called external respiration. The exchange of gases between the blood and the cells of the body is celled internal respiration.
The Journey of a Breath of Air
Breathing is only part of the process of delivering oxygen to where it is needed in the body. Gas exchange occurs in the alveoli by passive diffusion of gases between the alveoli and the blood in the capillaries of the lungs. The passive diffusion of oxygen and carbon dioxide is shown in Figure below.
Recall that diffusion is the movement of substances from an area of higher concentration to an area of lower concentration. The difference between the high concentration of oxygen (O2) in the alveoli and the low O2 concentration of the blood in the capillaries is enough to cause O2 molecules to diffuse across the thin walls of the alveoli and capillaries and into the blood. Carbon dioxide (CO2) moves out of the blood and into the alveoli in a similar way.
After leaving the lungs, the oxygenated blood returns to the heart to be pumped through the aorta and around the body. The oxygenated blood travels through the aorta, to the smaller arteries and finally to the capillaries where gas exchange occurs. The oxygen molecules move out of the capillaries and into the body cells. While oxygen diffuses from the capillaries and into body cells, carbon dioxide diffuses from the cells into the capillaries.
Figure 19.5
Gas exchange is the movement of oxygen into the blood and carbon dioxide out of the blood.
Breathing and Cellular Respiration
The oxygen that arrives at the cells from the lungs is used by the cells to release the energy stored in molecules of sugar. Cellular respiration is the process of breaking down glucose to release energy (see the Cell Functions chapter). The waste products of cellular respiration include carbon dioxide and water. The carbon dioxide molecules move out of the cells and into the capillaries that surround the cells. The carbon dioxide is removed from the body by the lungs.
Lesson Summary
Your respiratory system is made up of the tissues and organs that allow oxygen to enter and carbon dioxide to leave your body. These structures include your nose, mouth, larynx, pharynx, lungs, and diaphragm. The main function of the respiratory system is to bring oxygen into the body and releases carbon dioxide into the atmosphere. During inhalation, the diaphragm contracts and moved downward. The rib muscles contract and cause the ribs to move outward, causing the chest volume to increase. Air pressure inside the lungs is less than the air pressure outside so air is sucked into the lungs. When the diaphragm and rib muscles relax, air is pushed out of the lungs. Exhalation is normally a passive process.
Oxygen enters the lungs, passes through the alveoli and into the blood. The oxygen is carried around the body in blood vessels. In a similar way, carbon dioxide, a waste product, moves into the blood capillaries by passive diffusion and is brought to the lungs in the pulmonary circulation. The carbon dioxide is released into the air during exhalation. The oxygen that arrives from the lungs is used by the cells dur
ing cellular respiration to release the energy stored in molecules of sugar. A waste product of cellular respiration, carbon dioxide, is removed from the body by exhalation.
Review Questions
Name the parts of the respiratory system.
What is the main function of the respiratory system?
A classmate says that the lung muscles cause the lungs to move during breathing. Do you agree with your classmate?
How do the respiratory system and the cardiovascular system work together?
Breathing is an involuntary action. Does this mean that you cannot control your breathing?
In what part of the lung does gas exchange occur?
What is the difference between breathing and respiration?
Identify how breathing and cellular respiration are connected.
What is the important gas that is carried into the lungs during inhalation?
What is the name of the waste gas that is released during exhalation?
If a disease caused the alveoli to collapse, how might this affect a person’s health?
Further Reading / Supplemental Links
http://en.wikipedia.org/wiki
Vocabulary
alveoli
Little "sacs" at the end of the bronchioles where most of the gas exchange occurs.
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