Iron deficiency anemia is the most common type of anemia. It occurs when the dietary intake or absorption of iron is less than what is needed by the body. As a result, hemoglobin, which contains iron, cannot be made. Hemophilia is the name of a group of hereditary genetic diseases that affect the body's ability to control blood clotting. Hemophilia is characterized by a lack of clotting factors in the blood.
Review Questions
Name the four main components of blood.
How does the structure of a red blood cell relate to its function?
Name one other gas that can bind to hemoglobin, and identify an affect that such binding can have on homeostasis.
Why might iron-deficiency anemia cause a person to feel tired?
Identify two different types of human blood systems.
Identify the processes involved in blood clotting.
A sample of blood taken from a patient has elevated (higher than normal) levels of leucocytes. What could this mean?
Identify where in the body red blood cells and white blood cells are made.
Explain why taking erythropoietin (EPO), which stimulates the production of more red blood cells, is considered a form of cheating in sports.
Further Reading / Supplemental Links
http://www.estrellamountain.edu/faculty/farabee/biobk
http://waynesword.palomar.edu/aniblood.htm
http://en.wikipedia.org
Vocabulary
agglutination
The clumping of red blood cells that occurs when different blood types are mixed together.
antibodies
Proteins that are used by the immune system to identify and destroy foreign objects such as bacteria and viruses.
blood
A fluid connective tissue; arterial blood carries oxygen and nutrient to all the body’s cells, and venous blood carries carbon dioxide and other metabolic wastes away from the cells.
blood type (blood group)
Determined by the presence or absence of certain molecules, called antigens, on the surface of red blood cells.
coagulation
Blood clotting, a complex process by which blood forms solid clots.
coagulation factors
Proteins in the plasma which respond damage to a blood vessel; response includes a series of chemical reactions that form a tough protein called fibrin.
erythrocytes
Red blood cells; flattened, doubly concave cells that carry oxygen.
haemochromatosis
A hereditary disease that is characterized by a buildup of iron in the body; can eventually cause end organ damage, most importantly in the liver and pancreas, manifesting as liver failure and diabetes mellitus respectively.
hematopoiesis
The production of blood cells in the red and yellow bone marrow.
heme
The iron-containing portion of hemoglobin; enables the protein to carry oxygen to cells.
hemoglobin
Protein in red blood cells that carries oxygen.
hemophilia
The name of a group of hereditary genetic diseases that affect the body's ability to control blood clotting.
hormones
Chemical messengers that are produced by one cell and carried to another.
leukemia
A cancer that originates in the bone marrow and is characterized by an abnormal production of white blood cells.
leukocytes
White blood cells; function in the cellular immune response; includes neutrophils, eosinophils, and macrophages.
lymphoma
A cancer of the lymphatic system, which helps to filter blood; can be categorized as either Hodgkin's lymphoma or non-Hodgkin's lymphoma.
plasma
The golden-yellow liquid part of the blood; 90% water and 10% dissolved materials including proteins, glucose, ions, hormones, and gases.
serum albumin
A plasma protein that acts as a transporter of hormones and other molecules.
sickle-cell disease
A group of genetic disorders caused by abnormally shaped hemoglobin, called sickle hemoglobin.
thrombocytes
Platelets; important in blood clotting; cell fragments that bud off bone marrow cells called megakaryocytes.
universal donors
Individuals with type O negative blood.
universal recipients
Individuals with type AB positive blood.
Points to Consider
How might the composition of your blood change during a 24-hour period?
What do you think is the relationship between the cardiovascular system, blood, and the respiratory system?
Lesson 22.3: Respiratory System
Lesson Objectives
Distinguish between external and internal respiration.
Identify the structures of the respiratory system.
Outline the process of inhalation.
Describe how carbon dioxide is carried in the blood.
Compare the causes of emphysema and asthma.
Introduction
Have you ever wondered what it would be like to have gills? You would breathe and look very different from the rest of us, but they would be great for swimming and diving! Despite such differences, the main functions of lungs and gills are the same: to obtain oxygen, and to release carbon dioxide.
The human respiratory system brings oxygen, O2, into the body and releases carbon dioxide, CO2, into the atmosphere. Oxygen is drawn in through the respiratory tract, which is shown in Figure below, and is then delivered to the blood. This process is called external respiration. The exchange of gases between the blood and the cells of the body is called internal respiration.
Figure 22.34
The respiratory system. Air moves down the trachea, a long straight tube in the chest. The diaphragm pulls air in and pushes it out. Respiratory systems of various types are found in a wide variety of organisms.
Comparing "Cellular Respiration" and "Respiration"
Respiration is the transport of oxygen from the outside air to the cells of the body, and the transport of carbon dioxide in the opposite direction. This is in contrast to the biochemical definition of respiration, which refers to cellular respiration. Cellular respiration is the metabolic process by which an organism obtains energy by reacting oxygen with glucose to give water, carbon dioxide and ATP (energy). Although respiration is necessary to sustain cellular respiration and thus life in animals, the processes are very different. Cellular respiration takes place in individual cells of the animal, while respiration involves the transport of metabolites between the organism and external environment.
Structures of the Respiratory System
The nose and nasal cavity filter, warm, and moisten the inhaled air. The nose hairs and mucus produced by the epithelial cells in 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. In humans the pharynx is important in vocalization
The larynx, also called the voicebox, is found just below the point at which the pharynx splits into the trachea and the esophagus, shown in Figure below. The voice is generated in the larynx. Air from the lungs is needed for the vocal folds to produce speech.
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, which are the first airway passages that do not contain cartilage. The bronchioles lead into the alveoli, which are the multi-lobed sacs in which most of the gas exchange occurs.
Figure 22.35
The structures of the respiratory system include the nasal cavity, the pharynx, larynx, which together are the upper respiratory tract. The
trachea, bronchi, bronchioles and alveoli are part of up the lower respiratory tract.
The Journey of a Breath of Air
In air-breathing vertebrates such as humans, respiration of oxygen includes four stages:
Ventilation from the atmosphere into the alveoli of the lungs.
Pulmonary gas exchange from the alveoli into the pulmonary capillaries.
Gas transport from the pulmonary capillaries through the circulation to the peripheral capillaries in the organs.
Peripheral gas exchange from the tissue capillaries into the cells and mitochondria.
Ventilation: From the Air to the Alveoli
Air enters the body through the nose, is warmed, filtered, and passed through the nasal cavity. Air passes the pharynx (which has the epiglottis that prevents food from entering the trachea). The upper part of the trachea contains the larynx. The vocal cords are two bands of tissue that extend across the opening of the larynx. After passing the larynx, the air moves into the trachea. The trachea is a long tube that divides into two smaller tubes called bronchi which lead into each lung, shown in Figure above. Bronchi are reinforced to prevent their collapse and are lined with ciliated epithelium and mucus-producing cells. Bronchi branch into smaller and smaller tubes called bronchioles. Bronchioles end in grape-like clusters called alveoli. Alveoli are surrounded by a network of thin-walled capillaries, shown in Figure below.
Breathing in, or inhaling, is usually an active movement, contraction of the diaphragm muscles uses ATP. The diaphragm is a muscle that is found below the lungs (shown in Figure above). Contraction of the diaphragm causes the volume of the chest cavity to increase, and the air pressure within the lungs to decrease. 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. Breathing out, or exhaling, is normally a passive process powered by the elastic recoil of the chest, similar to letting the air out of a balloon.
Figure 22.36
The alveoli are the tiny grape-like structures within the lungs, and are the site of pulmonary gas exchange.
Pulmonary Gas Exchange: From the Alveoli into the Pulmonary Capillaries
Breathing is only part of the process of delivering oxygen to where it is needed in the body. The process of gas exchange occurs in the alveoli by diffusion of gases between the alveoli and the blood passing in the lung capillaries, as 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 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. CO2 moves out of the blood and into the alveoli in a similar way. The greater the concentration difference, the greater the rate of diffusion.
Figure 22.37
Gas exchange happens in the lungs through diffusion. Deoxygenated blood has a high concentration of CO and a low O concentration. CO moves out of the blood and into the alveoli, where the concentration of CO is lower. Likewise, O moves from an area of higher concentration (the alveoli), to an area of lower concentration (the blood).
Breathing also results in loss of water from the body. Exhaled air has a relative humidity of 100 percent because of the diffusion of water that from the moist surface of the breathing passages and the alveoli into the warm exhaled air.
In the lungs, oxygen is transported across the thin membranes of the alveoli and the border of the capillary and attracted to the hemoglobin molecule within the red blood cell.
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, arterioles, and finally to the peripheral capillaries where gas exchange occurs.
Peripheral Gas Exchange: From Capillaries into Cells, and from Cells into Capillaries
The oxygen concentration in body cells is low, while the blood that leaves the lungs is 97 percent saturated with oxygen. So, oxygen diffuses from the blood into the body cells when it reaches the peripheral capillaries (the capillaries in the systemic circulation).
Carbon dioxide concentration in metabolically active cells is much greater than in capillaries, so carbon dioxide diffuses from the cells into the capillaries. 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). Carbonic acid and bicarbonate play an important role in regulating the pH of the body.
In order to remove CO2 from the body, the bicarbonate is picked up by a red blood cell, and is again turned 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 alveoli where it is exhaled. The following equation shows this process:
HCO3- + H+ ⇌ H2CO3 ⇌ CO2 + H2O
Gas exchange between your body and the environment occurs in the alveoli. The alveoli are lined with pulmonary capillaries, the walls of which are thin enough to permit the diffusion of gases. Inhaled oxygen diffuses into the pulmonary capillaries, where it binds to hemoglobin in the blood. Carbon dioxide diffuses in the opposite direction, from capillary blood to alveolar air. At this point, the pulmonary blood is oxygen-rich, and the lungs are primarily holding carbon dioxide. Exhalation follows, thereby ridding the body of the carbon dioxide and completing the cycle of respiration.
Gas Exchange and Homeostasis
The equilibrium between carbon dioxide and carbonic acid is very important for controlling the acidity of body fluids. As gas exchange occurs, the pH balance of the body is maintained as part of homeostasis. If proper respiration is interrupted two things can occur:
Respiratory acidosis, in which arterial blood contains too much carbon dioxide, causing a drop in blood pH.
Respiratory alkalosis 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.
Control of Breathing by the Nervous System
Breathing is one of the few bodily functions which, within limits, can be controlled both consciously and unconsciously. Conscious attention to breathing is common in activities such as yoga, swimming, and karate. In speech or vocal training, a person learns to discipline his or her breathing for purposes other than life support.
Muscular contraction and relaxation controls the rate of expansion and constriction of the lungs. These muscles are controlled by the autonomic nervous system from the parts of the brainstem that control breathing: the medulla and the pons. This area of the brainstem forms the respiration regulatory center. When carbon dioxide levels increase in the blood (in the form of carbonic acid), such as during exercise, the pH level of the blood drops. This causes the medulla to send nerve impulses to the diaphragm and the muscles between the ribs, causing them to contract and increase the rate of breathing. This automatic control of respiration can be impaired in premature babies, or by drugs or disease.
Without breathing, the body’s oxygen levels drop dangerously low within minutes, leading to permanent brain damage followed by death. It is not possible for a healthy person to voluntarily stop breathing indefinitely. If we do not inhale, the level of carbon dioxide builds up in our blood and we experience great air hunger. Eventually, not breathing leads to a loss of consciousness at which time the autonomic nervous system takes control and initiates breathing.
Inhalation
Inhalation is started by the diaphragm and supported by the external intercostal muscles (the muscles that are between the ribs). It is an active process that needs ATP. When the diaphragm contracts, the ribcage expands and the contents of the abdomen are moved downward. This results in a larger thoracic (chest) volume, which in turn causes a decrease in air
pressure inside the lungs. As the pressure in the chest falls, air from outside the body moves into the respiratory system. Normal resting respirations are 10 to 18 breaths per minute. During an average breath, an adult will exchange from 500 ml to 700 ml of air. The average breath capacity of a person is called lung volume, or tidal volume.
Exhalation
Exhalation is generally a passive process, however active, or forced, exhalation is carried out by the abdominal and the internal intercostal muscles. The lungs have a natural elasticity and as they recoil from the stretch of inhalation, air flows out of the lungs until the pressures in the chest and the atmosphere reach equilibrium. During forced exhalation, as when blowing out a candle, expiratory muscles including the abdominal muscles and internal intercostal muscles generate pressure in the chest and abdomen, which forces air out of the lungs.
Homeostatic Imbalances of the Respiratory System: Diseases and Disorders
Respiratory disease is the term for diseases of the lung, bronchial tubes, trachea and throat. These diseases range from mild, such as a cold, to being possibly life-threatening, such as bacterial pneumonia.
Respiratory diseases can be grouped as either obstructive (conditions which lower the rate of the airflow into and out of the lungs, such as in asthma) or restrictive (conditions that cause a reduction in the functional volume of the lungs, such as emphysema.)
CK-12 Biology I - Honors Page 111
