Chapter 46. The Heart, continued. The Heart. The Heart, continued

Transcription

1 The Heart The circulatory system is made up of the cardiovascular system and the lymphatic system. The heart is the central organ of the cardiovascular system. The cardiovascular system is made up of the the blood, heart, and blood vessels. The lymphatic system is made up of the lymph, lymph nodes, and the lymph vessels. Some of the important parts of the heart are described below. The septum separates the heart vertically into two sides. The atrium is an upper chamber of the heart that receives blood that is returning to the heart. A ventricle is a lower chamber of the heart that pumps blood out of the heart. The valves are flaps of tissue that control the flow of the fluid. There are two types of valves: the atrioventricular valves and the semilunar valves. The atrioventricular valves prevent blood from flowing backward into the atria. The semilunar valves prevent blood from flowing back into the ventricles when the heart relaxes. Circulation in the Heart Path of blood as it circulates through the heart: Deoxygenated blood enters the right atrium. The right atrium sends deoxygenated blood into the right ventricle.

2 Circulation in the Heart, continued The muscles of the right ventricle contract and force blood into the pulmonary arteries. The pulmonary artery sends blood to the lungs. In the lungs, carbon dioxide diffuses out of the blood, and oxygen diffuses into the blood. Circulation in the Heart, continued The muscles of the right ventricle contract and force blood into the pulmonary arteries. The pulmonary artery sends blood to the lungs. In the lungs, carbon dioxide diffuses out of the blood, and oxygen diffuses into the blood. Circulation in the Heart, continued The muscular walls of the left ventricle contract and force blood into a large blood vessel. This blood vessel is called the aorta, and it carries blood from the left ventricle to the rest of the body. Control of the Heartbeat The heart contracts its muscle cells in waves. The first group of heart-muscle cells that are stimulated lie in an area of the heart known as the sinoatrial node. The sinoatrial (SA) node is a group of specialized heart-muscle cells that lies at the junction of the superior vena cava and the right atrium and regulates the contraction of the heart. Control of the Heartbeat, continued Electrical Regulation of the Heart The electrical impulse initiated by the SA node eventually reaches another special area of the heart, known as the atrioventricular (AV) node. The atrioventricular (AV) node is a group of specialized heart-muscle cells that is located between the right atrium and right ventricle and generates electrical impulses that cause the ventricles of the heart to contract.

3 Control of the Heartbeat, continued A heartbeat has two phases. Phase one is called systole and occurs when the ventricles contract, closing the AV valves and opening the SL valves to pump blood into the two major vessels that exit the heart. Control of the Heartbeat, continued Phase two is called diastole and occurs when the ventricles relax, allowing the back pressure of the blood to close the SL valves and opening the AV valves. A series of pressure waves are caused by the contractions of the left ventricle when it forces blood through the arteries. This is called a pulse. Blood Vessels The circulatory system is known as a closed system because the blood is contained within either the heart or the blood vessels at all times. The blood vessels that are part of the human circulatory system form a vast network to help keep the blood flowing in one direction. Blood Vessels, continued Arteries and Blood Pressure The large, muscular vessels that carry blood away from the heart and to the body are called arteries. Arteries are made up of three layers: an inner endothelial layer, a middle layer of smooth muscle, and an outer layer of connective tissue. Blood Vessels, continued Arteries and Blood Pressure, continued As the heart moves the blood through the arteries, it produces a great force against the inside walls of a blood vessel. This force is known as blood pressure. High blood pressure, or hypertension, can place a strain on the walls of the arteries and could cause that artery to burst. Blood Vessels, continued Arteries and Blood Pressure, continued In order to measure blood pressure, systolic pressure and diastolic pressure must be measured. Systolic pressure, measured first, is the pressure of the blood when the ventricles contract. Diastolic pressure, measured second, indicates the steady flow of blood through the artery.

4 Blood Vessels, continued Capillaries and Veins From the artery, a series of smaller vessels called arterioles carry the blood to capillaries. The capillaries are a vast network of tiny vessels that allow an exchange between the blood and the cells to occur. Blood Vessels, continued Capillaries and Veins, continued After cells interact with the blood, the blood goes back to the heart. To do this, capillaries merge to form venules. These venules are connected to a vein. A vein is a bundle of vascular tissue that transports fluids and nutrients back to the heart. Veins are made up of three layers: endothelium, smooth muscle, and connective tissue. Blood Vessels Patterns of Circulation The heart and blood vessels work together to form a continuous, closed system of circulation. This system contains two subsystems: the pulmonary circulation and the systemic circulation. Circulatory Pathway in the Human Body Anatomy of the Human Cardiovascular System Click below to watch the Visual Concept. Visual Concept

5 Patterns of Circulation, continued Pulmonary Circulation Pulmonary circulation is the circulation of the blood as it travels between the heart and lungs. Pulmonary circulation brings the deoxygenated blood that comes into the heart to the lungs, and returns oxygenated blood back to the heart for distribution to the body. Patterns of Circulation, continued Systemic Circulation Systemic circulation is the circulation of the blood between the heart and all other body tissues. Systemic circulation has several subsystems, including coronary circulation, hepatic portal circulation, and renal circulation. Patterns of Circulation, continued Systemic Circulation, continued Coronary circulation is the systemic circulation that supplies blood to the heart itself. If blood flow in the coronary arteries (arteries that supply blood to the heart) is reduced or cut off, muscle cells will die. Patterns of Circulation, continued Systemic Circulation, continued Hepatic portal circulation is the systemic circulation that supplies blood between the liver and the small intestines. Renal circulation is the systemic circulation that supplies blood to the kidneys. Circulatory Loops in the Human Body Lymphatic System The circulatory system also includes the lymphatic system. The lymphatic system returns fluids that have collected in the tissues to the bloodstream. Excess fluid in the tissues, called lymph, moves into the tiny vessels of the lymphatic system by diffusion.

6 Lymphatic System, continued Lymphatic System Lymph vessels are similar to blood vessels but are also different in many ways. Lymph is filtered through small organs known as lymph nodes to trap tissue debris and other foreign particles. Lymph nodes also store lymphocytes, white blood cells that are specialized to fight disease. Objectives List the components of blood. Distinguish between red blood cells, white blood cells, and platelets in terms of their structure and function. Summarize the process of blood clotting. Explain what determines the compatibility of blood types for transfusion. Composition of Blood Blood is composed of a liquid medium plasma and blood solids red and white blood cells and platelets. Plasma Plasma is a sticky, straw-colored fluid that is about 90 percent water and includes metabolites, nutrients, wastes, salts, and proteins. Plasma provides cells with nourishment and carries various proteins. Composition of Blood, continued Red Blood Cells A red blood cell is a disc-shaped cell that has no nucleus and transports oxygen to cells in all parts of the body. Immature red blood cells synthesize large amounts of an iron-containing protein called hemoglobin. Hemoglobin is the molecule that transports oxygen. Composition of Blood, continued White Blood Cells White blood cells are cells in the blood that destroy bacteria, viruses, and toxic proteins and helps the body develop immunities. In addition to different functions, white blood cells also have a different structure and life span than red blood cells.

7 Composition of Blood, continued Composition of Blood White Blood Cells, continued There are several types of white blood cells, including phagocytes and antibodies. Phagocytes are cells that engulf and digest foreign matter or microorganisms. Antibodies are proteins that react to a specific type of invader or inactivate or destroy toxins. Blood Types Red blood cells have surface proteins that are used to classify a person s blood. The type of surface protein determines a person s blood type. The surface proteins on a red blood cell or on an invading pathogen are called antigens. The most important human antigens are A, B, and Rh. They form two systems of blood typing: the A-B-O system and the Rh system. Blood Types, continued A-B-O System The A-B-O system is a means of classifying blood by the antigens located on the surface of the red blood cells and the antibodies circulating in the plasma. If blood of a different type is introduced into the body it will be treated as a foreign invader and the antigen-antibody reaction will be produced, with some exceptions. Blood Types, continued Blood Types Rh System The Rh system is based on the presence or absence of the Rh antigen. A person with Rh antigens is Rh positive; a person without Rh antigens is Rh negative. Similar complications to those of the ABO system can occur if blood containing the wrong Rh antigens is transfused into a person.

8 Objectives Differentiate external respiration from internal respiration. Trace the path of air from the atmosphere to the bloodstream. Describe how gases are exchanged in the lungs and transported in the bloodstream. Summarize the skeletal and muscular changes that occur during breathing. Describe how the rate of breathing is controlled. Respiration The function of the respiratory system is to exchange gases with the cardiovascular system. The respiratory system involves both external respiration and internal respiration. External respiration is the exchange of gases between the atmosphere and the blood. Internal respiration is the exchange of gases between the blood and the cells of the body. The Human Respiratory System Parts of the Human Respiratory System Click below to watch the Visual Concept. Visual Concept The Lungs The lungs are the central organs of the respiratory system in which gases are exchanged. The lungs are located inside the thoracic cavity, which is bound by the rib cage and the diaphragm. In order to decrease friction from movement of the lungs during breathing, the entire cavity and the lungs are coated with a slippery fluid secreted by membranes, called pleura. The Lungs, continued The Path of Air External respiration begins at the mouth and at the nose. Air is filtered and moistened by various parts of the nose and mouth and them moves into the throat. The throat is also called the pharynx and is a tube at the back of the nasal cavity and the mouth.

9 The Lungs, continued The Path of Air, continued Air then moves from the pharynx through the epiglottis into a cartilaginous tube, called the trachea. The epiglottis is a flap of cartilage that hangs at the entrance of the larynx and directs food and air to the correct places. The Lungs, continued The Path of Air, continued At the end of the trachea, the air moves into the two bronchi. Each of the bronchi lead from the trachea to the lungs. The air moves through the bronchi and then into the smaller tubes called the bronchioles that branch from the bronchi. The Lungs, continued The Path of Air, continued Air finally makes its way through the bronchioles to the place where gas exchange takes place alveoli. Gas exchange is facilitated by the enormous amount of surface area in the lungs. Gas Exchange and Transport Gas Exchange in the Lungs When air enters the lungs, the oxygen in the air crosses the thin alveolar membranes and the capillary walls and dissolves into the blood by diffusion. Carbon dioxide moves in the opposite direction, also by diffusion, and crosses the capillary walls and thin alveolar membranes to enter the alveoli. Gas Exchange and Transport, continued Transport of Carbon Dioxide Carbon dioxide diffuses into the blood and either stays in the plasma, binds to hemoglobin, or reacts with water to produce bicarbonate ions. Bicarbonate ions combine with hydrogen ions to form carbonic acid, which in turn forms carbon dioxide and water. The carbon dioxide diffuses out of the capillaries into the alveoli and is exhaled into the atmosphere. Mechanism of Breathing Breathing is the process of moving air into and out of the lungs. Inspiration is the process of taking air into the lungs. When a deep breath is taken, the chest and ribs expand.

10 Mechanism of Breathing, continued The expansion of the chest and ribs occurs with help from the diaphragm, which is a large skeletal muscle that separates the thoracic cavity from the abdominal cavity and the abdominal wall. Inhalation and Exhalation Expiration is the process of releasing air from the lungs. When this happens, the diaphragm and rib muscles relax, which forces the lungs to deflate. Mechanism of Breathing, continued Regulation of Breathing Both rate and depth of breathing change in order to provide oxygen and eliminate carbon dioxide from cells. The rate of breathing is controlled by the brain and brain stem by monitoring the concentration of carbon dioxide in the blood. All the activities used to regulate breathing are controlled subconsciously by the brain.