Chapter 5 - Cardiovascular System PDF

ANSCI 3300 (Anatomy and Physiology of Domestic Animals) Prepared by: ALONA T. BADUA E-mail Address: [email protected] Central Luzon State University Science City of Muñoz 3120 Nueva Ecija, Philippines Inst...

ANSCI 3300 (Anatomy and Physiology of Domestic Animals) Prepared by: ALONA T. BADUA E-mail Address: [email protected] Central Luzon State University Science City of Muñoz 3120 Nueva Ecija, Philippines Instructional Material for the Course ANSCI 3300 ANATOMY AND PHYSIOLOGY OF DOMESTIC ANIMALS Chapter 5 The Cardiovascular System Overview The components of the cardiovascular system are the heart and the blood vessels. Blood is the fluid that circulated in this organ system. Blood functions not only to provide nutrients but also protection to the body. Topics in this chapter cover the functions of cardiovascular system, blood, including the structures of the heart, blood circulation and the lymphatic organs. This chapter will provide understanding on the importance of this system on homeostasis and disease protection. I. Objectives On successful completion of this chapter, the student will be able to: 1. List down the structures of the cardiovascular system and describe their functions 2. Identify the components of the blood 3. Discuss the circulation of blood through the heart 4. Identify the organs of the lymphatic system and give their functions II. Learning Activities 1  ANSCI 3300 (Anatomy and Physiology of Domestic Animals) A. Components of the cardiovascular system According to Aspinall & Cappello (2015), the blood vascular system is made up of four parts: 1. Blood which is a fluid connective tissue that transports oxygen and nutrients around the body and collects waste products produced by the tissues. 2. The heart which is a hollow, muscular, four-chambered organ responsible for pumping blood around the body. 3. The circulatory system is a network of arteries, veins and capillaries in which the blood flows around the body. 4. The lymphatic system is a network of lymphatic vessels that transports lymph or excess tissue fluid around the body and is responsible for returning it to the circulation B. The Blood 1. Functions of the blood The following are the functions of the blood (Fails & Magee,2018): 1. Distribution of nutrients absorbed from the digestive tract 2. Transport of oxygen from the lungs to cells throughout the body 3. Transport of carbon dioxide from metabolizing cells to the lungs 4. Transport of waste products from metabolizing cells to the kidneys for excretion 5. Transport of hormones from endocrine glands to target cells 6. Assistance in body temperature control by transporting heat from deeper structures to the surface of the body 7. Assistance in maintaining a constant pH of body fluids by providing chemical buffers 8. Assistance with the prevention of excessive loss of blood from injuries by providing proteins and other factors necessary for blood coagulation 9. Assistance with the defense of the body against disease by providing antibodies, cells, and other factors of body defense 2. Components of the Blood Blood makes up about 7% of the total body weight and has a pH of about 7.4 (7.35–7.45) (Aspinall & Cappello,2015). Blood is sticky and viscous having about five times the viscosity of water with specific gravity of 1/20 more than water (1.06). The color ranges from bright red (oxygenated) to dark red (unoxygenated). It is composed of two parts, the cellular elements and the fluid elements (Fails & Magee,2018). a. Cellular elements of blood The erythrocytes (red blood cells) are non-nucleated biconcave disc cells that specialized in the transportation of oxygen. It contains hemoglobin (principal oxygen transport medium of blood and responsible for its red color). These cells are involved in transporting oxygen to tissues, transporting carbon dioxide to the lungs and maintaining cell shape and deformability (Colville & Bassert,2016). 2  ANSCI 3300 (Anatomy and Physiology of Domestic Animals) The second cellular components of blood are leucocytes (white blood cells). These are nucleated cells capable of independent movement. These can be grouped either as granulocytes, those that contain granules within the cytoplasm or agranulocytes, absence of the granules. Under the granulocutes are the neutrophils, the cells considered as first line of defense against infection and constitute the greatest number of all the white blood cells. The second are the eosinophils which increase in number during allergic reactions and parasitism and the third are the basophils which are involved in mast cell formation. The agranulocytes include the monocytes, the largest white blood cells which are involved in phagocytosis and the lymphocytes which produce antibodies, neutralize or fix toxins and aid in fat resorption from the intestine (Fails & Magee,2018). The third cellular components are the thrombocytes (platelets), these cells are non-nucleated, round to oval in shape with clear cytoplasm that contains small blue to purple granules. The granules contain clotting factors and calcium, which are necessary for blood to clot.smallest of the formed elements and necessary for blood clotting (Colville & Bassert,2016). The plasma is the straw-colored fluid component of an uncoagulated blood while serum is the fluid component after the blood has clotted. Essentially, serum is plasma minus the plasma proteins responsible for producing the clot (Fails & Magee,2018). Plasma is about 92% water and 8% other substances. Globulin, albumin, and fibrinogen are the primary plasma proteins. Globulin and albumin are important in the immune responses of the body. Fibrinogen is important in the process of blood clotting. Plasma also contains small amounts of ions, gases, hormones and nutrient substances (Klein,2019). 3. The Structures of the Heart The heart is a cone-shaped hollow muscular organ. It is partially surrounded by a serous sac called pericardium or pericardial sac. The layers of the heart is composed of an outer serous covering(epicardium), an inner endothelial lining (endocardium) and a thick muscular layer Source:https://simplemed.co.uk/subjects/cardiovascular/ (myocardium) (Figure 1) anatomy-of-the-cardiovascular-system (Openstax College, 2017). Figure 1. The layers of the heart wall 3  ANSCI 3300 (Anatomy and Physiology of Domestic Animals) 1. Blood Circulation To start the circulation of blood through the heart, let’s start in the vena cava, the large vein that brings deoxygenated blood from the systemic circulation (but not the pulmonary circulation) to the heart. The vena cava enters the right atrium of the heart. The deoxygenated blood passes from the right atrium through the tricuspid valve into the right ventricle. At this point the pulmonary valve in the right ventricle is closed. When the right ventricle is full the tricuspid valve is forced closed and the pulmonary valve is forced open. The right ventricle contracts and the deoxygenated blood leaves the right ventricle through the pulmonary valve and enters the pulmonary circulation via the pulmonary artery. After the deoxygenated blood has been oxygenated in the pulmonary circulation (lungs) it comes back to the heart via the pulmonary vein that empties into the left atrium. The mitral valve opens and the blood from the left atrium enters the left ventricle. When the ventricle is full the mitral valve is forced closed and the aortic valve is forced open. The left ventricle contracts and oxygenated blood leaves through the aortic valve and enters the systemic circulation via the aorta, the largest artery in the body. Once in the systemic circulation the blood is distributed throughout the animal’s body through the arteries (Figure 2) (Colville & Bassert,2016). Types of blood circulation 1. cardiac – which involves the heart 2. pulmonary – which involves the lungs 3. systemic – which involves the general body area 4. portal – which involves the intestines and the liver C Source:https://simple.wikipedia.org/wiki/Heart Figure 2. The structures of the heart and blood circulation 4  ANSCI 3300 (Anatomy and Physiology of Domestic Animals) 5. Blood vessels The cardiovascular system is composed of three blood vessels: the arteries, veins and capillaries. Arteries carry blood away from the heart. In the pulmonary circulation they carry deoxygenated blood to the lungs for oxygenation. In systemic circulation they carry oxygenated blood throughout the animal’s body. There are two types of artery: elastic arteries and muscular arteries. Elastic arteries have the greatest ability to stretch when blood passes through them because they have a large number of elastic fibers in the middle layers of their walls. These arteries are found closest to the heart because they have to be able to stretch and recoil without damage each time a surge of blood is ejected from a ventricle during ventricular systole. Best example is the aorta, the largest elastic artery in the body. Muscular arteries have more smooth muscle fibers than elastic fibers in their walls. They are found farther away from the heart than elastic arteries and usually direct blood to specific organs and tissues. Muscular arteries branch off the smallest elastic arteries and therefore have a smaller diameter. They are located far enough away from the heart that the blood surge is not severe enough to cause damage. Muscular arteries branch into arterioles (Colville & Bassert,2016). As veins approach the heart they become larger in diameter as more veins draining other areas of the body join together. The largest vein in the animal’s body is the vena cava, and all other systemic veins eventually drain into it. Many veins are working against gravity to get the blood back to the heart and they don’t have the force of ventricular contraction to propel blood flow. For this reason small and medium veins have one-way valves in their lumens. The valves allow blood to flow only in the direction of the heart. Venules are tiny veins that join together to form larger veins. In the pulmonary circulation these carry oxygenated blood; in the systemic circulation they carry deoxygenated blood and waste materials. Venules have thin enough walls that some fluid exchange between interstitial fluid and plasma can take place. Their walls consist of endothelium, a thin muscle layer, and a few fibrous connective tissue cells. White blood cells leave the circulation at the venule level to enter tissues at a site of inflammation (Colville & Bassert,2016). Capillaries are small, thin-walled, permeable vessels consisting of a single layer of endothelial cells. It is here that the exchange of gases, the uptake of nutrients and the removal of metabolic waste products take place. As the capillaries have a small diameter, blood flows slowly through them, allowing substances to diffuse between the blood and the tissues. The capillary beds are the networks of capillaries that extend between the arterioles and the venules (small veins) within the tissues (Aspinall & Cappello,2015). 6. The Pulse rate The pulse is the rate of alternating stretching and recoiling of the elastic fibers in an artery as blood passes through it with each heartbeat. The pulse wave resulting from the stretching and recoiling of the artery travels through all 5  ANSCI 3300 (Anatomy and Physiology of Domestic Animals) the arteries and arterioles and dissipates in the capillaries. In most animals the pulse is felt on superficial arteries lying against firm surfaces such as bones like the femoral, brachial or coccygeal artery. The pulse and the heartbeat in an animal are not the same thing. The pulse is felt on a superficial artery; the heartbeat is counted using a stethoscope to listen to the animal’s chest (auscultation) to hear the heart sounds (Colville & Bassert,2016). 7. The lymphatic system The lymphatic system is part of the circulatory system of the body and is responsible for returning the excess tissue fluid that has leaked out of the capillaries to the circulating blood. The fluid within the system is called lymph and is similar to plasma but without the larger plasma proteins. However, lymph contains more lymphocytes than are present in the blood. The lymphatic system is composed of both lymphatic vessels and lymphoid tissue, which are found in all regions of the body with a few exceptions such as the central nervous system and bone marrow. The functions of the lymphatic system are (Aspinall & Cappello,2015): a. To return excess tissue fluid that has leaked out of the capillaries to the circulating blood b. To remove bacteria and other foreign particles from the lymph in specialised filtering stations known as lymph nodes c. To produce lymphocytes, which produce antibodies; the lymphatic system may also be considered as part of the immune system d. To transport the products of fat digestion and the fat-soluble vitamins from the lacteals of the intestinal villi to the circulation The lymphatic system begins in the tissue spaces between the capillaries of the blood vascular system. It drains from the lungs and from the rest of the body tissues via a system of vessels that end in the venous system. The lymph vessels begin in the tissues as blind lymph capillaries. By the convergence of lymph capillaries, smaller lymph vessels are formed and these in turn unite to form large lymph vessels. These vessels contain valves which prevent backflow of its content but they have thinner walls than veins. All the lymph vessels drain into either the thoracic duct or the right lymphatic duct which empty into the anterior vena cava (Fails & Magee,2018). What are the organs of the lymphatic system? a. The lymph nodes are ovoid, pinkish bodies intercalated in the course of the lymph vessels. These act as filters and phagocytic structures, removing foreign matter from the lymph stream before passing it on through other lymph vessels toward the heart (Fails & Magee,2018). b. The thymus is located in the cranial thorax. It is largest in size when an animal is young, but shrinks and is replaced by fat as the animal matures, making it difficult to locate in adult animals. It is responsible for the production of T lymphocytes that give rise to the cell mediated immune response (Colville & Bassert,2016, Aspinall & Cappello,2015). 6  ANSCI 3300 (Anatomy and Physiology of Domestic Animals) c. The bursa of Fabricius is found only in birds and is similar in structure and function to the thymus. It is a round sac that sits right above the cloaca (Colville & Bassert,2016). d. Peyer’s patches are located in the wall of the small intestine. They have various structures and functions depending on the species. However, their common function is the activation of B cells to produce antibodies against antigens in the small intestines. Peyer’s patches are just one type of gut associated lymphoid tissue (GALT) located throughout various areas of intestinal mucosa and submucosa (Colville & Bassert,2016). e. The spleen is a tongue-shaped organ located on the left side of the abdomen. It is near the stomach in and near the rumen in ruminants. Not only does the spleen store red blood cells and produce red blood cells during fetal development, but it also filters the blood and lymph (Colville & Bassert,2016) f. The tonsils like those found in the ceca of chickens and in pharynx serve as regional lymph nodes. III. References Aspinall, V. & Cappello, M.(2015). Introduction to Veterinary Anatomy and Physiology Textbook. (3rd ed.). Elsevier. Colville ,T. & Bassert, J.M. (2016). Clinical Anatomy and Physiology for Veterinary Technicians. (3rd ed.). St. Louis, MO: Elsevier. Fails, A. D. & Magee, C. (2018). Anatomy and Physiology of Farm Animals. (8th ed.). Hoboken, NJ: Wiley-Blackwell. Klein, B.G. (2019). Cunningham’s Textbook of Veterinary Physiology. (6th ed.) St. Louis, MO: Elsevier. OpenStax College. (2017). Anatomy and Physiology. OpenStax. https://openstax.org/details/books/anatomy-and-physiology. https://simple.wikipedia.org/wiki/Heart https://simplemed.co.uk/subjects/cardiovascular/anatomy-of-the-cardiovascular- system 7