Download Chapters 7, 8, and 9

EXTENDED LECTURE OUTLINE
7.1 Microbes, Pathogens, and You
Microorganisms are widely distributed in the environment and carry out many beneficial functions. Unfortunately human infectious
diseases are typically caused by bacteria and viruses, collectively called pathogens. The body has three lines of defense against
invasion: barriers to entry, first responders, and specific defenses.
Bacteria
Bacteria are single-celled prokaryotes. Bacteria have a cell wall that contains a unique amino-disaccharide and in some
bacteria, a capsule that has a thick, gummy consistency is present outside of the cell wall. Many bacteria have accessory
rings of DNA called plasmids that may carry antibiotic resistance. Bacteria reproduce by binary fission. Bacteria may
release toxins that damage the human body.
Viruses
Viruses are acellular and are obligate parasites, meaning that they must replicate inside a living cells. A virus always has two
parts: an outer capsid composed of protein units and an inner core of nucleic acid, which can be DNA or RNA. In large
measure, viruses rely on the host’s enzymes and ribosomes for reproduction.
Emerging Viruses
New or emerging viruses seem to cause widespread disease. In some cases a virus emerges by being transported
from one location to another where it has not been before. Many viruses are transmitted by vectors, usually insects.
Viruses also change very rapidly and so a new virus may actually be a mutated older virus.
Prions
Prions or proteinaceous infectious particles cause a group of degenerative diseases of the nervous system. Prions are proteins
of unknown function in the brains of healthy individuals. Disease occurs when certain prion proteins change their shape into
a “rogue” form that converts normal prion proteins into the rogue configuration.
7.2 The Lymphatic System
The lymphatic system consists of lymphatic vessels and the lymphatic organs. It has four main functions: absorb excess tissue fluid
and return it to the bloodstream; absorb fats in the form of lipoproteins from the small intestines and transport them to the
bloodstream; produce, maintain, and distribute lymphocytes; and defend the body against pathogens.
Lymphatic Vessels
Lymphatic vessels form a one-way system of capillaries, vessels and ducts that take lymph to cardiovascular veins in the
shoulders. These take up excess tissue fluid called lymph once inside the lymphatic vessels.
Lymphatic Organs
The lymphatic organs are divided into the primary (red bone marrow and thymus gland) and secondary (lymph nodes and
spleen) organs.
The Primary Lymphatic Organs
Red bone marrow is the site of stem cells that divide and produce blood cells. B cells mature in the bone marrow
but T cells mature in the thymus, located in the thoracic cavity. The thymus gland also produces thymic hormones.
Secondary Lymphatic Organs
The spleen contains white pulp and red pulp. The white pulp contains a concentration of lymphocytes while the red
pulp is involved in filtering the blood. Lymph nodes occur along lymphatic vessels. Each node is packed with B
lymphocytes. Lymph is filtered through the lymph nodes. Lymphocytes react with pathogens present in the filtered
blood and lymph.
7.3 Nonspecific Defenses
Immunity involves nonspecific and specific defenses. Nonspecific defenses protect against any pathogen, while specific defenses are
effective against a particular infectious agent.
Barriers to Entry
The body has both physical and chemical barriers to infection.
Skin and Mucous Membranes
Intact skin and mucous membranes are very effective physical barriers that prevent infection. Ciliated cells
that line the upper respiratory tract sweep mucus and trapped particles up into the throat.
Chemical Barriers
Chemical barriers include secretions of the sebaceous glands of the skin, the antibacterial enzyme lysozyme
in perspiration, saliva, and tears, and the acid pH of the stomach and vagina.
Resident Bacteria
A significant chemical barrier is created by the normal flora, microbes that normally reside in certain areas
of the body. They prevent potential pathogens from taking up residence.
Inflammatory Response
Redness, heat, swelling, and pain characterize the inflammatory reaction. The release of histamine from damaged tissue cells
and mast cells brings about redness and swelling. A rise in temperature increases phagocytosis by neutrophils and
macrophages. The swollen area stimulates free nerve endings, causing the sensation of pain.
Protective Proteins
The complement system, which includes various plasma proteins, assists nonspecific immunity. It amplifies the inflammatory
reaction by attracting phagocytes and promoting phagocytosis. Some complement proteins form pores in the surface of
bacteria and thereby cause them to burst. Interferons are proteins produced by virus-infected cells that help noninfected cells
prepare for possible viral attack.
7.4 Specific Defenses
When nonspecific defenses have failed to prevent an infection, the specific line of defense comes into play.
How Specific Defense Works
Specific defenses respond to antigens, which are molecules the immune system recognizes as foreign to the body. Specific
defenses primarily depend on the action of either B lymphocytes or T lymphocytes.
B Cells and Antibody-Mediated Immunity
The receptor on a B cell is called a B-cell receptor. The clonal selection model states than an antigen selects, then
binds to the B-cell receptor of only one type B cell and then this B cell produces multiple copies (clones) itself.
B Cells Become Plasma Cells and Memory B Cells
Plasma cells secrete antibodies and eventually undergo apoptosis. Memory B cells remain in the body and
produce antibodies if the same antigen enters the body at a later date.
Structure of an Antibody
Antibodies are also called immunoglobulins. They are typically Y shaped molecules with two arms. Each
arm has a heavy and a light polypeptide chain. These chains contain variable and constant regions. The
antigen combines with the antibody in the variable regions in a lock-and-key manner.
Classes of Antibodies
There are five different classes of circulating antibodies: IgG, IgM, IgA, IgD, and IgE. They differ from
each other as outlined in Table 7.2.
T Cells and Cell-Mediated Immunity
T cells directly attack diseased cells and cancer cells. Other T cells release cytokines that stimulate both nonspecific
and specific defenses.
How T Cells Recognize an Antigen
Like B cells, each T cell bears a specific receptor. However, for a T cell to recognize an antigen, the
antigen must be presented by an antigen-presenting cell (APC), usually a macrophage, along with a MHC
(major histocompatibility complex) antigen. Thereafter the activated T cell undergoes clonal expansion
until the infection has been stopped. Then most of the activated T cells undergo apoptosis. A few cells
remain, however, as memory T cells.
Types of T Cells
The two main types of T cells are cytotoxic T cells and helper T cells. Cytotoxic T cells kill infected cells
that bear a foreign antigen on contact; helper T cells stimulate other immune cells and produce cytokines.
7.5 Acquired Immunity
Immunity can be brought about artificially by medical intervention.
Active Immunity
Vaccines are available to induce long-lived active immunity. After exposure to a vaccine, antibodies are present in the body.
The secondary response is higher than the primary response. Active immunity is long-lived because there are memory B cells
and memory T cells in the body.
Passive Immunity
Passive immunity occurs when an individual is given antibodies from an outside source. For example, nursing passes
antibodies from mother to child.
Monoclonal Antibodies
Plasma cells are fused with myeloma cells and these hybridomas produce only one type of antibody. These
monoclonal antibodies are most often used in diagnostic procedures such as pregnancy tests.
Cytokines and Immunity
Cytokines, including interferon, are used in an attempt to promote the body’s ability to recover from cancer.
7.6 Hypersensitivity Reactions
Sometimes the immune system responds in a manner that harms the body.
Allergies
Allergic responses occur when the immune system reacts vigorously to substances not normally recognized as foreign.
Immediate allergic responses are due to the activity of antibodies. Symptoms can vary from mild, cold-like symptoms, to
anaphylactic shock. The immunoglobulin IgE appears to be responsible. Delayed allergic responses, such as contact
dermatitis, are due to the activity of T cells.
Tissue Rejection
Rejection occurs when cytotoxic T cells bring about the destruction of foreign tissue in the body. Immunosuppressive drugs
act by inhibiting the response of T cells to cytokines. Xenotransplantation is the use of animal organs instead of human
organs in transplant patients. Genetic engineering can make these organs less antigenic to humans.
Disorders of the Immune System
An autoimmune disease occurs when T cells or antibodies mistakenly attack the body’s own cells. In myasthenia gravis,
neuromuscular junctions do not work properly. In multiple sclerosis, the myelin sheath of the nerve fibers is broken down.
A person with systemic lupus erythematosus has various symptoms eventually leading to death from kidney damage. In
rheumatoid arthritis, the joints are affected. AIDS is an example of an acquired immune deficiency. In individuals with
severe combined immunodeficiency disease (SCID), both antibody- and cell-mediated immunity is lacking or severely
reduced.
EXTENDED LECTURE OUTLINE
8.1 Overview of Digestion
The purpose of the digestive system is to ingest food, digest it, absorb nutrients, and eliminate wastes.
Walls of the Digestive Tract
The wall of the GI tract has four layers. The first layer of the wall next to the lumen is called the mucosa. The second layer
is the submucosa. The third layer is the muscularis and the fourth layer is the serosa.
8.2 First Part of the Digestive Tract
The mouth, pharynx and esophagus are in the first part of the GI tract.
The Mouth
A roof, formed by the hard and soft palates, separates the mouth from the nasal cavities. Three pairs of salivary glands
secrete saliva (containing salivary amylase for digestion of starch) into the mouth.
The Teeth and Tongue
The teeth chew the food and the tongue forms a bolus for swallowing. Each tooth has a crown and a root. The crown
has a layer of enamel, dentin, and an inner pulp. The root has dentin and pulp. Blood vessels and nerves are in the
pulp. Gum disease and dental caries are two ailments associated with the teeth. The tongue contains the sensory
receptors called taste buds.
The Pharynx and Esophagus
The air passage and food passage cross in the pharynx. The esophagus is the long tube that takes food to the stomach.
Swallowing
When one swallows, the air passage is usually blocked off and food must enter the esophagus. A rhythmic
contraction called peristalsis pushes the food along the esophagus and continues in all the organs of the digestive
tract.
8.3 The Stomach and Small Intestine
The Stomach
The stomach expands and stores food. While food is in the stomach, it churns, mixing food with the acidic gastric juices
(contain HCl and pepsin for the digestion of protein to peptides) to produce chyme. Few materials are absorbed through the
stomach lining.
Historical Aspects
An accidental gun shot wound allowed a scientist in the 1800s to study the function of the stomach.
The Small Intestine
The small intestine is smaller in diameter than the large intestine but it is actually longer.
Digestion is Completed in the Small Intestine
The small intestine contains enzymes to digest all types of foods. The duodenum receives bile from the gallbladder
and pancreatic enzymes. Pancreatic juice is basic because of the presence of NaHCO 3.
Nutrients are Absorbed in the Small Intestine
The walls of the small intestine have fingerlike projections called villi where nutrient molecules are absorbed into
the cardiovascular and lymphatic systems. The lymphatic capillary in a villus is called a lacteal.
Lactose Intolerance
Lactose is the primary sugar in milk. Some people are not able to digest lactose because they are missing the enzyme lactase.
Lactose intolerance is characterized by diarrhea, gas, bloating, and abdominal cramps after drinking milk or other dairy
products.
Obesity: Diabetes Type 2 and Cardiovascular Disease
Foods that are high in refined carbohydrates and /or fat may be responsible for the current epidemic of obesity among
Americans. The intake of too much sugar and fat can result in obesity which is associated with diabetes type 2 and
cardiovascular disease.
8.4 Three Accessory Organs and Regulation of Secretions
Three Accessory Organs
The three accessory organs of digestion—the pancreas, liver, and gallbladder—send secretions to the duodenum via ducts.
The pancreas produces pancreatic juice, which contains digestive enzymes to break down carbohydrates (i.e., pancreatic
amylase), proteins (i.e., trypsin), and fats (i.e., lipase). The liver produces bile, which is stored in the gallbladder. The liver
receives blood from the small intestine by way of the hepatic portal vein. It has numerous important functions, and any
malfunction of the liver is a matter of considerable concern. The gallbladder stores bile until it is sent to the duodenum.
Gallstones are crystals of cholesterol.
Liver Disorders
Hepatitis and cirrhosis are two serious diseases that affect the entire liver and hinder its ability to repair itself.
Regulation of Digestive Secretions
The secretions of digestive juices are controlled by the nervous system and by hormones. The parasympathetic nervous
system automatically stimulates gastric secretion when you look at or smell food. The stomach and duodenal wall produce
hormones that regulate digestion.
8.5 The Large Intestine and Defecation
The large intestine consists of the cecum, colon (ascending, transverse, descending, and sigmoid), and the rectum, which ends at the
anus.
Functions of the Large Intestine
The large intestine absorbs water, salts, and some vitamins and it forms and stores feces. Defecation, which is ridding the
body of feces, is also a function of the large intestine.
Disorders of the Colon and Rectum
Many of these disorders can be prevented or minimized by a good diet and good bowel habits.
Diarrhea
The major causes of diarrhea are infection of the lower intestinal tract and nervous stimulation.
Constipation
When a person is constipated, the feces are dry and hard. An intake of water and fiber can help regularity
of defecation.
Diverticulosis
Diverticulosis is the occurrence of little pouches of mucosa that have pushed out through weak spots in the
muscularis.
Irritable Bowel Syndrome
IBS is a condition in which the muscularis contracts powerfully but without its normal coordination.
Inflammatory Bowel Disease
This is a collective term for a number of inflammatory disorders including ulcerative colitis and Crohn’s
disease.
Polyps and Cancer
Polyps are small growths arising from the epithelial lining which may be benign or cancerous. Some
investigators believe that dietary fat increases the likelihood of colon cancer.
8.6 Nutrition and Weight Control
Obesity has doubled in the United States in only 20 years. It is on the rise throughout the world.
How Obesity is Defined
Obesity is often defined as a body mass index (BMI) of 30 or greater. Figure 8.11 will help you determine your BMI.
Classes of Nutrients
A nutrient is defined as a component of food that performs a physiological function in the body.
Carbohydrates
To meet energy needs, dietitians recommend consuming food rich in complex carbohydrates like breads and pasta.
Simple carbohydrates like table sugar (sucrose) are not recommended. Fiber helps regularity and may help prevent
cancer.
Can Carbohydrates be Harmful?
Some nutritionists hypothesize that the high intake of refined carbohydrates and fructose sweeteners
processed from cornstarch may be responsible for obesity. These foods have a high glycemic index
because the blood glucose response to these foods is high, potentially leading to insulin resistance.
Proteins
Dietary meat does assure that all the essential amino acids are acquired but this is also possible by consuming a
combination of legumes, grains, vegetables, seeds and nuts.
Can Proteins be Harmful?
The body can be harmed if the amount of protein in the diet is severely limited, or if it is present in an
overabundance. The average American eats about twice as much protein as needed. Certain types of meat
are known to be high in saturated fats.
Lipids
Fats, oils, and cholesterol are lipids. Saturated fats, which are usually solid at room temperature, promote heart
disease. Oils contain unsaturated fatty acids which do not promote cardiovascular disease.
Can Lipids be Harmful?
Lipids should be used sparingly because they contribute to plaque on blood vessels walls. Trans-fatty acids
arise when unsaturated fatty acids are hydrogenated to produce a solid fat. Trans fats may contribute to
cholesterol in the blood.
Minerals
Minerals are divided into major minerals and trace minerals. The major minerals are constituents of cells and body fluids and
are structural components of tissues. The trace minerals are parts of larger molecules.
Calcium
Calcium is needed to have strong bones and older women in particular are at risk for osteoporosis, a degenerative
bone disease due to insufficient intake of calcium and/or uptake of calcium by their bones.
Sodium
Most Americans have too much sodium in their diet. Salt intake leads to hypertension in some persons.
Vitamins
Vitamins are organic compounds that the body is unable to produce but needs for metabolic purposes. Many vitamins are
portions of coenzymes.
Antioxidants
The vitamins A, E, and C are antioxidants that protect cell contents from damage due to free radicals.
Vitamin D
A precursor molecule in skin is converted to vitamin D after exposure to UV light rays. Vitamin D is modified first
in the kidneys and then the liver until calcitriol results. Calcitriol is needed for calcium absorption.
How to Plan Nutritious Meals
The new food pyramid can be used to help you decide how your daily calories should be distributed among the foods to eat.
Eating Disorders
People with eating disorders are dissatisfied with their body image. Severe conditions such as obesity, anorexia nervosa, and
bulimia can lead to malnutrition, disability, and death.
EXTENDED LECTURE OUTLINE
9.1 The Respiratory System
The organs of the respiratory system ensure that oxygen enters the body and carbon dioxide leaves the body. Ventilation is another
term for breathing that includes both inspiration or inhalation and expiration or exhalation.
9.2 The Upper Respiratory Tract
The nasal cavities, pharynx, and larynx are the organs of the upper respiratory tract.
The Nose
The two nasal cavities, which contain receptor cells, receive tear ducts from eyes and communicate with sinuses. The
auditory tube from middle ear communicates with the nasopharynx. The nose warms and cleanses incoming air.
The Pharynx
The pharynx, a passageway from the nasal cavities to oral cavities, and to the larynx, contains the tonsils. The pharynx takes
air from the nose to larynx and transports food from the oral cavity to esophagus.
Larynx
The epiglottis covers the glottis, an opening to the larynx which contains vocal cords.
9.3 The Lower Respiratory Tract
The trachea and the rest of the respiratory system are in the lower respiratory tract.
The Trachea
The trachea, supported by C-shaped cartilaginous rings, is lined by ciliated cells which sweep impurities up to the throat. The
trachea takes air to the bronchial tree.
The Bronchial Tree
Two primary bronchi, which divide into ever smaller bronchioles, conduct air to and in lungs. During an asthma attack,
bronchioles constrict.
The Lungs
The lungs are paired, cone-shaped organs within the thoracic cavity. The right lung has three lobes, while the left has two
lobes.
The Alveoli
The alveoli are the air sacs lined by squamous epithelium and surrounded by blood capillaries. Alveoli function in
gas exchange. Premature infants often suffer from respiratory distress syndrome.
9.4 Mechanism of Breathing
Ventilation or breathing has two phases: inspiration which moves air into the lungs and expiration which moves air out of the lungs.
Inspiration
During inspiration, the diaphragm and external intercostal muscles contract, increasing the volume of the thoracic cavity.
This causes air to move into the lungs. Humans inhale by negative pressure.
Expiration
Expiration is the passive phase of breathing. The elastic properties of the thoracic wall and lungs cause them to recoil,
moving air out.
Maximum Inspiratory Effort and Forced Expiration
Maximum inspiratory effort involves muscles of the back, chest, and neck, which increases the size of the thoracic
cavity larger than normal. Although expiration is normally passive, it can also be forced. This is necessary to sing
and blow out air.
Volumes of Air Exchanged During Ventilation
A spirometer is used to measure the amount of air that is moving into and out of the lungs.
Tidal Volume
The tidal volume, only about 500 mL, is the small amount of air that moves in and out with each breath
when we are relaxed.
Vital Capacity
The maximum amount of air that can be moved in plus the maximum amount that can be moved out during
a single breath is called the vital capacity.
Inspiratory and Expiratory Reserve Volume
The reserve volumes are measured during forced inspiration and expiration.
Residual Volume
Some air always remains in the lungs. This is the residual volume and is no longer useful for gas exchange.
9.5 Control of Ventilation
Nervous Control of Breathing
Normally adults have a breathing rate of 12 to 20 ventilations per minute. This rhythm is controlled by a respiratory control
center located in the medulla oblongata of the brain. It is thought that a faulty respiratory center signal is the cause of sudden
infant death syndrome (SIDS). We can voluntarily change our breathing pattern to accommodate various activities.
Chemical Control of Breathing
Chemoreceptors are sensory receptors in the body that are sensitive to chemical composition of body fluids. The pH of blood
will become more acidic when there is more carbon dioxide in the blood. Two sets of chemoreceptors that are sensitive to
pH can cause breathing to speed up.
9.6 Gas Exchanges in the Body
Gas exchange is critical to homeostasis. The principles of diffusion govern whether oxygen or carbon dioxide enters or leaves the
blood in the lungs and in the tissues.
External Respiration
External respiration is the diffusion of CO2 from pulmonary capillaries into alveolar sacs and O2 from alveolar sacs into
pulmonary capillaries.
Internal Respiration
Internal respiration is the diffusion of O2 from systemic capillaries into tissues and CO2 from tissue fluid into systemic
capillaries.
9.7 Respiration and Health
The respiratory tract is constantly exposed to environmental air and therefore to pathogens.
Upper Respiratory Tract Infections
Upper respiratory tract infections include the following:
Sinusitis
Infection of cranial sinuses
Otitis Media
Infection of the middle ear
Tonsillitis
Infection of tonsils
Laryngitis
Infection of larynx
Lower Respiratory Tract Disorders
Lower respiratory tract disorders include infections, restrictive and obstructive pulmonary disorders, and lung cancer.
Lower Respiratory Infections
Lower respiratory infections include acute bronchitis (infection of primary and secondary bronchi), pneumonia
(infection of lungs), and pulmonary tuberculosis (infection caused by tubercle bacillus).
Restrictive Pulmonary Disorders
Restrictive pulmonary disorders involve a reduction of vital capacity and can be caused by, for example, asbestos.
Obstructive Pulmonary Disorders
Obstructive Pulmonary Disorders includes chronic bronchitis (inflamed airways) and emphysema (alveolar walls
break down). Asthma is a disease of the bronchi and bronchioles that is marked by an unusual sensitivity to specific
irritants. Asthma is not curable but it is treatable.
Lung Cancer
Lung cancer follows this sequence of events: thickening of airway cells, loss of cilia, atypical nuclei, tumor and
metastasis.