Chapter 2 - B. Circulatory System and Respiratory System PDF

CHAPTER 2 STRUCTURE AND FUNCTION OF THE BODY OF LIVING THINGS B. Circulatory System and Respiratory System Circulatory System 1. Blood Humans can't live without blood. Without blood, the body's organs couldn't get the oxygen and...

CHAPTER 2 STRUCTURE AND FUNCTION OF THE BODY OF LIVING THINGS B. Circulatory System and Respiratory System Circulatory System 1. Blood Humans can't live without blood. Without blood, the body's organs couldn't get the oxygen and nutrients they need to survive, we couldn't keep warm or cool off, fight infections, or get rid of our own waste products. Without enough blood, we'd weaken and die. Here are the basics about the life-sustaining fluid called blood. What Is Blood and What Does It Do? Blood brings oxygen and nutrients to all the parts of the body so they can keep working. Blood carries carbon dioxide and other waste materials to the lungs, kidneys, and digestive system to be removed from the body. Blood also fights infections, and carries hormones around the body. Blood is made up of blood cells and plasma. Plasma is a yellowish fluid that has nutrients, proteins, hormones, and waste products. The different types of blood cells have different jobs. What Are the Types of Blood Cells? 1. Red blood cells: Red blood cells (RBCs, also called erythrocytes) are shaped like slightly indented, flattened disks. RBCs contain hemoglobin, a protein that carries oxygen. Blood gets its bright red color when hemoglobin picks up oxygen in the lungs. As the blood travels through the body, the hemoglobin releases oxygen to the different body parts. Each RBC lives for about 4 months. Each day, the body makes new RBCs to replace those that die or are lost from the body. RBCs are made in the inside part of bones called the bone marrow. 1  2. White blood cells: White blood cells (also called leukocytes) are a key part of the immune system. The immune system helps the body defend itself against infection. Different types of white blood cells (WBCs) fight germs, such as bacteria and viruses. Some types of WBCs make antibodies, which are special proteins that recognize foreign materials and help the body get rid of them. There are several types of WBCs, and their life spans vary from hours to years. New cells are constantly being formed — some in the bone marrow and some in other parts of the body such as the spleen, thymus, and lymph nodes. Blood contains far fewer WBCs than red blood cells, although the body can increase WBC production to fight infection. The white blood cell count (the number of cells in a given amount of blood) in someone with an infection often is higher than usual because more WBCs are being made or are entering the bloodstream to battle the infection. 3. Platelets: Platelets (also called thrombocytes) are tiny oval-shaped cells that help in the clotting process. When a blood vessel breaks, platelets gather in the area and help seal off the leak. Platelets work with proteins called clotting factors to control bleeding inside our bodies and on our skin. Platelets survive only about 9 days in the bloodstream and are constantly being replaced by new platelets made by the bone marrow. How Does Blood Travel in the Body? With each heartbeat, the heart pumps blood throughout our bodies, carrying oxygen to every cell. After delivering the oxygen, the blood returns to the heart. The heart then sends the blood to the lungs to pick up more oxygen. This cycle repeats over and over again. The circulatory system is made up of blood vessels that carry blood away from and toward the heart. 2  There are three main types of blood vessels: 1. Arteries: o Function: Carry oxygen-rich blood away from the heart to the rest of the body. o Structure: Thick, muscular walls to handle the high pressure of blood pumped by the heart. 2. Veins: o Function: Carry oxygen-poor blood back to the heart. o Structure: Thinner walls than arteries, with valves that prevent blood from flowing backward. 3. Capillaries: o Function: Connect arteries and veins, allowing the exchange of oxygen, nutrients, and waste between blood and tissues. o Structure: Very thin walls, just one cell thick, to allow easy exchange of substances. 2. Heart and Circulatory System What Does the Heart Do? The heart is a pump, usually beating about 60 to 100 times per minute. With each heartbeat, the heart sends blood throughout our bodies, carrying oxygen to every cell. After delivering the oxygen, the blood returns to the heart. The heart then sends the blood to the lungs to pick up more oxygen. This cycle repeats over and over again. What Does the Circulatory System Do? The circulatory system is made up of blood vessels that carry blood away from and towards the heart. Arteries carry blood away from the heart and veins carry blood back to the heart. The circulatory system carries oxygen, nutrients, and hormones to cells, and removes waste products, like carbon dioxide. These roadways travel in one direction only, to keep things going where they should. 3 What Are the Parts of the Heart? The heart has four chambers — two on top and two on bottom: The two bottom chambers are the right ventricle and the left ventricle. These pump blood out of the heart. A wall called the interventricular septum is between the two ventricles. The two top chambers are the right atrium and the left atrium. They receive the blood entering the heart. A wall called the interatrial septum is between the atria. The atria are separated from the ventricles by the atrioventricular valves: The tricuspid valve separates the right atrium from the right ventricle. The mitral valve separates the left atrium from the left ventricle. Two valves also separate the ventricles from the large blood vessels that carry blood leaving the heart: The pulmonic valve is between the right ventricle and the pulmonary artery, which carries blood to the lungs. The aortic valve is between the left ventricle and the aorta, which carries blood to the body. What Are the Parts of the Circulatory System? 4 Two pathways come from the heart: The pulmonary circulation is a short loop from the heart to the lungs and back again. The systemic circulation carries blood from the heart to all the other parts of the body and back again. In pulmonary circulation: The pulmonary artery is a big artery that comes from the heart. It splits into two main branches, and brings blood from the heart to the lungs. At the lungs, the blood picks up oxygen and drops off carbon dioxide. The blood then returns to the heart through the pulmonary veins. In systemic circulation: Next, blood that returns to the heart has picked up lots of oxygen from the lungs. So it can now go out to the body. The aorta is a big artery that leaves the heart carrying this oxygenated blood. Branches off of the aorta send blood to the muscles of the heart itself, as well as all other parts of the body. Like a tree, the branches gets smaller and smaller as they get farther from the aorta. At each body part, a network of tiny blood vessels called capillaries connects the very small artery branches to very small veins. The capillaries have very thin walls, and through them, nutrients and oxygen are delivered to the cells. Waste products are brought into the capillaries. Capillaries then lead into small veins. Small veins lead to larger and larger veins as the blood approaches the heart. Valves in the veins keep blood flowing in the correct direction. Two large veins that lead into the heart are the superior vena cava and inferior vena cava. (The terms superior and inferior don't mean that one vein is better than the other, but that they're located above and below the heart.) Once the blood is back in the heart, it needs to re-enter the pulmonary circulation and go back to the lungs to drop off the carbon dioxide and pick up more oxygen. How Does the Heart Beat? The heart gets messages from the body that tell it when to pump more or less blood depending on a person's needs. For example, when you're sleeping, it pumps just enough to provide for the lower amounts of oxygen needed by your body at rest. But when you're exercising, the heart pumps faster so that your muscles get more oxygen and can work harder. 5 One complete heartbeat is made up of two phases: 1. The first phase is called systole. This is when the ventricles contract and pump blood into the aorta and pulmonary artery. During systole, the atrioventricular valves close, creating the first sound (the lub) of a heartbeat. When the atrioventricular valves close, it keeps the blood from going back up into the atria. During this time, the aortic and pulmonary valves are open to allow blood into the aorta and pulmonary artery. When the ventricles finish contracting, the aortic and pulmonary valves close to prevent blood from flowing back into the ventricles. These valves closing is what creates the second sound (the dub) of a heartbeat. 2. The second phase is called diastole. This is when the atrioventricular valves open and the ventricles relax. This allows the ventricles to fill with blood from the atria, and get ready for the next heartbeat. Diseases of the Circulatory System The circulatory system can be affected by various diseases. Here are some common ones: 1. Anemia: o What it is: A condition where the body doesn't have enough healthy red blood cells to carry oxygen. o Symptoms: Fatigue, weakness, and pale skin. 2. Atherosclerosis: o What it is: A condition where the arteries harden and narrow due to the buildup of fatty deposits (plaque) on their walls. o Symptoms: Often none until it becomes severe, but can lead to chest pain, heart attack, or stroke. o Causes: High cholesterol, high blood pressure, smoking, and lack of exercise. 3. Hypertension (High Blood Pressure): o What it is: A condition where the force of blood against the artery walls is too high. o Symptoms: Often none, but can cause headaches, shortness of breath, and nosebleeds in severe cases. o Causes: Unhealthy diet, lack of physical activity, stress, and genetics. 4. Stroke: o What it is: A condition that occurs when blood flow to a part of the brain is blocked or reduced, leading to brain cell damage. o Symptoms: Sudden weakness, difficulty speaking, loss of balance, and severe headache. 6  How Can I Help Keep My Heart Healthy? To help keep your heart healthy: Get plenty of exercise. Eat a nutritious diet. Reach and keep a healthy weight. Do not smoke Respiratory System 1. Function of the Respiratory System Breathing is the process of taking oxygen into the body and expelling carbon dioxide. This process is carried out by the respiratory organs through the respiratory system. Oxygen that enters the body is used by cells for cellular respiration. Cellular respiration is a process that occurs in cells where glucose from food is broken down with the help of oxygen to produce energy. During this process, carbon dioxide and water are waste products that are expelled when you exhale. The energy produced from respiration is used for various activities. 2. Respiratory Organs These organs play a role in the respiratory system, each having a different structure and function: a. Nose: The first organ air passes through when entering and the last when exiting the body, acting as the gateway for air. The nose has two nasal cavities lined with mucus and fine hairs. The hairs filter out dirt, and the mucus traps any remaining particles while also warming and humidifying the air before it reaches the lungs. 7 b. Pharynx: A tube that connects the nasal cavity to the throat, serving as a pathway for both air and food. It is also the site where the respiratory and digestive systems meet, and it plays a role in sound resonance and immune defense. c. Larynx: Located at the top of the throat, it contains the vocal cords and is involved in producing sound. It also has a flap called the epiglottis that closes off the airway when swallowing to prevent food from entering the lungs. d. Trachea (Windpipe): A tube located in the neck that carries air to the lungs. It has cartilage rings and is lined with cilia that filter out dirt, which is then expelled by coughing or sneezing. e. Bronchi and Bronchioles: The trachea splits into two bronchi, each leading to a lung. Inside the lungs, the bronchi divide into smaller bronchioles that eventually end in tiny air sacs called alveoli, where oxygen enters the blood and carbon dioxide is expelled. f. Lungs: The lungs are located in the chest cavity above the diaphragm, a muscle that separates the chest from the abdomen. The right lung has three lobes, while the left lung has two, making the right lung slightly larger. The lungs are primarily made up of bronchi, bronchioles, and alveoli. The alveoli are tiny air sacs where gas exchange takes place. Oxygen from the air we breathe diffuses through the thin walls of the alveoli and into the blood. At the same time, carbon dioxide, a waste product from the body, moves from the blood into the alveoli to be exhaled. 8 3. Gas Exchange: O₂ and CO₂ a. Internal Respiration: Internal respiration is the process where oxygen from the blood is exchanged for carbon dioxide in the body's tissues. This process occurs during cellular respiration, where cells use oxygen to break down glucose and produce energy. b. External Respiration: External respiration takes place in the lungs, where oxygen from the air is exchanged for carbon dioxide from the blood. The alveoli in the lungs have very thin walls that allow oxygen to pass into the blood and carbon dioxide to leave the blood and enter the alveoli, to be expelled from the body when we exhale. 4. Breathing Mechanism Breathing consists of three main stages: inhaling (inspiration), gas exchange, and exhaling (expiration). The process of air moving in and out of the lungs is driven by the difference in air pressure between the inside of the chest cavity and the outside air. a. Abdominal Breathing: This type of breathing involves the diaphragm, a large muscle at the base of the lungs. During inspiration, the diaphragm contracts and flattens, creating more space in the chest cavity and allowing air to flow into the lungs. During expiration, the diaphragm relaxes and moves back to its dome shape, pushing air out of the lungs. b. Chest Breathing: In chest breathing, the muscles between the ribs, called intercostal muscles, play a key role. When these muscles contract during inspiration, the rib cage expands, increasing the volume of the chest cavity and drawing air into the lungs. During expiration, the muscles relax, the rib cage returns to its original size, and air is expelled from the lungs. 9  Smoking and Respiratory System Disorders 1. Smoking Avoiding smoking and secondhand smoke is essential for maintaining a healthy respiratory system. A person who smokes is called an active smoker, while someone who does not smoke but inhales smoke from others is a passive smoker. Both active and passive smoking are harmful to health, with passive smoking often being more dangerous. This is because an active smoker inhales only a small portion of the smoke, while the rest is exhaled into the air, where it can linger for hours. These harmful particles can be inhaled by passive smokers. Residue from smoke can also settle on clothes, hair, furniture, and carpets, posing a significant risk, especially to children. Physical signs of a smoker include: ▪ Dull-looking skin due to the effects of smoke. ▪ Breath and sweat that smell like smoke. ▪ Yellowed teeth and bad breath. ▪ Darkened lips. ▪ Dirty nails stained with nicotine. ▪ Frequent coughing. Cigarettes contain addictive substances that can cause users to become dependent. This addiction is harmful as cigarettes contain toxic chemicals that can infect and damage the respiratory system. A single puff of a cigarette contains about 4,000 harmful chemicals. Some of these include: 1. Carbon Monoxide: An odorless, colorless gas produced when a cigarette is burned. Carbon monoxide binds to hemoglobin more easily than oxygen, forcing the heart to work harder to supply the body with oxygen. Carbon monoxide poisoning can be fatal. 2. Nicotine: A colorless, oily liquid that can suppress hunger. Nicotine is a harmful insecticide that can damage the heart and circulatory system and cause addiction. The dangers of nicotine include: 1) Damaging brain tissue. 2) Making blood more likely to clot. 3) Hardening of the arteries. 10  3. Tar: A thick, dark brown or black liquid obtained from tobacco, wood, or charcoal. The dangers of tar include: 1. Killing cells in the respiratory tract and lungs. 2. Increasing mucus production in the lungs. 3. Causing lung cancer. 2. Respiratory System Disorders ❖ Lung Cancer: Caused by a malignant tumor in the bronchioles, lung cancer can disrupt the gas exchange in the lungs. It is often linked to smoking, but passive smokers can also develop this type of cancer. ❖ Emphysema: A condition where excess air in the lungs reduces the area available for gas exchange. It can be caused by chronic infections from smoking or other irritants, leading to mucus buildup and inflammation in the bronchioles, making it difficult to exhale. This traps air in the alveoli, causing them to stretch. ❖ Embolism: A blood clot that blocks capillaries in the lungs, obstructing the flow of oxygen and carbon dioxide. Lung embolism can occur after a heart attack, poisoning, drug overdose, or electric shock and is potentially fatal. ❖ Pneumonia: An inflammation of the lungs that causes alveoli to fill with fluid and red blood cells. Bacterial pneumonia, for example, is caused by Diplococcus pneumoniae, which spreads from one alveolus to another, potentially affecting an entire lung. 11 ❖ Bronchitis: Inflammation of the bronchial lining, leading to narrowed airways due to mucus buildup. Bronchitis makes breathing difficult and can be caused by frequent smoking. ❖ Asthma: A condition characterized by the narrowing of the airways due to allergies such as dust, fur, or hair. Asthma can be hereditary and may also be triggered by cold temperatures. It causes difficulty in breathing due to the contraction of the smooth muscles in the trachea, narrowing the airways. 12