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BL 1021 – Unit 4.9 – 4.14 The Respiratory and Defense Systems 4.9 Respiratory Systems • One of the major duties of the circulatory system is to move gases from place to place in the body. Living cells need a fresh supply of oxygen and need waste carbon dioxide removed. • The respiratory system works to take in new oxygen from the environment and expel carbon dioxide. By working together, all of the cells of the body get the oxygen they need. 4.9 Respiratory Systems • Oxygen is picked up in the blood during the pulmonary circuit. Carbon dioxide is released into the lungs at this same time. • During the systemic circuit, the oxygen is delivered to all of the body’s tissues and carbon dioxide is picked up from cells. 4.9 Respiratory Systems • Some oxygen is carried in the blood by being dissolved into the liquid, or plasma, component of the blood. • The majority, however, is carried by red blood cells called erythrocytes. These a specialized cells filled with the protein hemoglobin which is an oxygen carrier. 4.9 Respiratory Systems • Hemoglobin has a special bonding relationship with oxygen. • It strongly binds oxygen in oxygen-rich areas (lungs) but releases oxygen in oxygen-poor areas (body tissues). • This allows hemoglobin to deliver oxygen where it is most needed. 4.10 Types of Respiratory Surfaces • For a gas like oxygen to be taken up, a special set of cells called a respiratory surface must exist. • This surface must be thin enough to allow gases to diffuse in and out easily. • This surface must be moist to allow gases to be able to dissolve into the liquid to be absorbed. • Respiratory surfaces come in a variety of forms: 4.10 Types of Respiratory Surfaces • Skin • (Frogs, earthworms) • Some organisms will have a very thin skin layer with capillaries close enough to the surface to allow gas exchange. • In these type of animals, the skin must be kept moist to breathe. 4.10 Types of Respiratory Surfaces • Gills • (Fish and most aquatic animals) • Gills have a series of capillaries close to the surface. • Gills do not need to worry about drying out as they re in the water. • Gills typically have some sort of protective cover to keep out dirt and parasites. 4.10 Types of Respiratory Surfaces • Tracheae • (insects) • As insects live on land, they need an internalized system to reduce the water lost from the respiratory surface. • Tracheae are small tube inlets on the body that branch out within. 4.10 Types of Respiratory Surfaces • The majority of the tracheae is dry, with only the “dead end” regions coated in water to allow diffusion. • Tracheae branch out to reach all the cells of the body due and thus insects are limited in size as these simple tubes only work on a small scale. 4.10 Types of Respiratory Surfaces • Lungs • (mammals) • Lungs are an internal respiratory compartment with a highly-branched structure. • Lungs work with the circulatory system to deliver their gases. 4.10 Types of Respiratory Surfaces • Lungs are localized to one area and do not need to reach all of the body because the closed circulatory system is capable of delivering all the gases between the lungs and the body. 4.11 Human Respiratory System • The human respiratory system, is found in the body cavity, is protected by the rib cage, is lined on the bottom by the diaphragm and is entered through the nasal/mouth cavity. 4.11 Human Respiratory System • The diaphragm pulls on the lungs, expanding them and creating a negative pressure that pulls air in. • When the diaphragm relaxes, the lungs decrease in volume, pushing air out. 4.11 Human Respiratory System • The respiratory system is made up of two lungs, a left and right. Air enters through the nasal cavity or mouth. • The nasal cavity conditions the air to make it safe for the sensitive tissues of the lungs. • The nasal cavity acts as a filter and humidifier of the air. 4.11 Human Respiratory System • From the nasal cavity air travels through the larynx. This is the voice box that contains the vocal cords. • The vocal cords move in order to cause different vibrations which create different sounds to speak. 4.11 Human Respiratory System • From the larynx, air continues down the trachea (windpipe) and into two bronchi, tubes which lead to each lung. • No gas exchange occurs at this stage, these are just piping to feed air into/out of the lungs. 4.11 Human Respiratory System • The bronchi further branch within the lung into several smaller tubes called bronchioles. Each bronchiole ends in a series air sacs called alveoli, which appear like clusters of grapes. 4.11 Human Respiratory System • The alveoli are thinwalled spheres with a very thin liquid coating on the inside. • This is the site of gas exchange. • By having all these small sacs, the surface for gas exchange is maximized. 4.11 Human Respiratory System • Special chemicals exist in the fluid of the lungs that keep a thin coating of liquid on all of the lung’s inner surface. • Excess fluid buildup, like in pneumonia, is dangerous as it acts as a barrier to gas exchange, preventing normal breathing. 4.11 Human Respiratory System • Special chemicals exist in the fluid of the lungs that keep a thin coating of liquid on all of the lung’s inner surface. • Excess fluid buildup, like in pneumonia, is dangerous as it acts as a barrier to gas exchange, preventing normal breathing. 4.12 The Defense Systems • The first line of defense in the body is a general series of barrier against multiple threats. • These nonspecific external defense mechanisms are in place to block all invaders. If an infectious organism cannot get inside the body, it cannot infect the body. 4.12 The Defense Systems • The nonspecific external defense systems: • The Skin acts as a physical barrier • Oil and acids are produced on the skin to kill off microorganisms • Hairs in the nasal tract • Mucus in internal membranes traps invaders • Cilia in mucous membranes move mucus out • Sweat, saliva and tears have anti-bacterial materials • Stomach acid kills swallowed bacteria 4.12 The Defense Systems • The body also has internal nonspecific defences. White blood cells (leukocytes) destroy foreign particles and dead cells. Interferon (proteins produced by virus-infected body cells) help healthy cells resist viruses Complement proteins coat the surface of microbes making them easier for white blood cells to identify them The inflammatory response (injured cells and invading microorganisms release chemicals that trigger the release of chemicals such as histamine which causes site to swell which promotes healing) Damaged cells release prostaglandins which increase blood flow to area Cells may release pyrogens which can stimulate a fever 4.13 The Lymphatic System • The lymphatic system carries fluid around the body and is the major carrier of the immune system. • The system also collects lipids from the digestive system as they are extracted from food. 4.13 The Lymphatic System • The lymphatic system is an open system; it collects fluid from the spaces between the tissues and then feeds it back into the circulatory system. • The fluid that is carried through is lymph. 4.13 The Lymphatic System • Germs captured by the lymph are filtered out in the lymph nodes. These are small masses of tissue in the network of lymph vessels. • Antibodies are made in the nodes. Antibodies are used to label and trap invaders. 4.13 The Lymphatic System • At lymph nodes, invading cells can also be destroyed by white blood cells. • When lymph filters through the spleen, special white blood cells destroy bacteria, dead tissue and foreign material. 4.13 The Lymphatic System • At lymph nodes, invading cells can also be destroyed by white blood cells. • When lymph filters through the spleen, special white blood cells destroy bacteria, dead tissue and foreign material. 4.14 The Immune System • The immune system is a series of defenses to specifically target invaders. • The cells that are part of this defense system are white blood cells, or leukocytes. They come in two basic types which work together to seek out and destroy the organisms or substances that cause disease. • Leukocytes are produced and stored in the thymus, spleen and bone marrow but will move throughout the body to fight infections. 4.14 The Immune System • The immune system is a series of defenses to specifically target invaders. • The cells that are part of this defense system are white blood cells, or leukocytes. They come in two basic types which work together to seek out and destroy the organisms or substances that cause disease. • Leukocytes are produced and stored in the thymus, spleen and bone marrow but will move throughout the body through the lymphatic vessels to fight infections. 4.14 The Immune System • Two major types of leukocytes: • Phagocytes engulf and destroy invaders • Lymphocytes allow the body to label, remember, and recognize invaders, allowing the body to better fight off invaders in repeated infections. There are two major types: one labels invaders while the other works more to destroy them. 4.14 The Immune System • Two major types of lymphocytes: • All lymphocytes begin life in the bone marrow. Some cells will remain there and mature into B Lymphocytes. • These cells detect antigens (any invading substance) and create antibodies that latch onto them, labeling them for destruction. 4.14 The Immune System • Antibodies stay in the body and thus the body is able to easily fight off an infection much easier during repeated infections. • Vaccinations work by giving the body a weakened or dead version of an antigen to learn from and create antibodies from. This allows the body to be ready for certain infections and when the body encounters them again. This is not always 100% effective as bacteria can evolve and change so that they are not recognized by antibodies. 4.14 The Immune System • Other lymphocytes will move from the bone marrow to the thymus gland and mature into T lymphocytes. • T cells work to destroy cells that it recognizes as invaders. This may be done directly or by detecting cells labeled by antibodies. Thus, B cells and T cells work together in many cases to destroy invaders. Tcells can also call in other white blood cells to help destroy the invaders in some cases. 4.14 The Immune System • There are two general pathways for immune defense: • Humoral or AntigenMediated immunity involves B cells creating new antibodies by “sizing-up” the invaders and then circulating those antibodies around the body to label all of the invaders. 4.14 The Immune System • Humoral immunity works well on bacteria, microorganisms, and fungi as it can easily label them for destruction. 4.14 The Immune System • The other major type of immunity is Cellmediated immunity. • This system targets infected cells for destruction directly using T-cells. 4.14 The Immune System • Cell-mediated immunity is best at destroying viruses and other invaders that get inside of the body’s cells as it will destroy the host cell as well. 4.14 The Immune System • With both types of immunity, cells can be mistakenly labeled as harmful. • In auto-immune diseases, immune cells label a certain type of cell in the body as harmful and destroy them. This causes damage to healthy tissues and loss of function. Type I diabetes is caused b the body destroying the cells of the pancreas that produce insulin. Without these cells, the body cannot regulate its blood sugar levels properly. 4.14 The Immune System • Blood transfusions can cause problems too. If a person receives blood that is a different type than theirs, the body may label the new blood cells as invaders and destroy them – causing clots of dead cells to form in the blood vessels. • Similarly, when a person receives a new organ from a donor, the body may label the new cells as invaders and destroy the organ in a process known as rejection. The organ recipient may have to take drugs to supress the immune system for the rest of their lives. This may make them more vulnerable to other infections.