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Learning Objectives Define what you understand by the term “Angiology”. State the organs of circulatory and lymphatic system. Mention the various functions of circulator system and lymphatic system. Contrast lymph and circulatory system. List the functions of blood and lymph. Trace the path of blood in the typical animal body. Begin with the aorta. State what you understand by the term “ANGIOLOGY” The word ANGIOLOGY came from Greek “angiologos” which means: angio, “vessel”; and logos, “knowledge”. It is the medical specialty which deals with the disease of circulatory system and lymphatic system, i.e., arteries, veins and lymphatic vases, and its diseases. Living things must be capable of transporting nutrients, wastes and gases to and from cells. Single-celled organisms use their cell surface as a point of exchange with the outside environment. Multicellular organisms have developed transport and circulatory systems to deliver oxygen and food to cells and remove carbon dioxide and metabolic wastes. Multicellular animals do not have most of their cells in contact with the external environment and so have developed circulatory systems to transport nutrients, oxygen, carbon dioxide and metabolic wastes. Components of the circulatory system include blood: a connective tissue of liquid plasma and cells heart: a muscular pump to move the blood blood vessels: arteries, capillaries and veins that deliver blood to all tissues There are several types of circulatory systems. The open circulatory system, examples of which are diagrammed in Figure below, is common to molluscs and arthropods. Open circulatory systems (evolved in insects, mollusks and other invertebrates) pump blood into a hemocoel with the blood diffusing back to the circulatory system between cells. Blood is pumped by a heart into the body cavities, where tissues are surrounded by the blood. The resulting blood flow is sluggish. 1 Vertebrates, and a few invertebrates, have a closed circulatory system, shown in Figure BOV (BELOW). Closed circulatory systems (evolved in echinoderms and vertebrates) have the blood closed at all times within vessels of different size and wall thickness. In this type of system, blood is pumped by a heart through vessels, and does not normally fill body cavities. Blood flow is not sluggish. Hemoglobin causes vertebrate blood to turn red in the presence of oxygen; but more importantly hemoglobin molecules in blood cells transport oxygen. The human closed circulatory system is sometimes called the cardiovascular system. A secondary circulatory system, the lymphatic circulation, collects fluid and cells and returns them to the cardiovascular system. 2 Identify the Organs of circulatory system and lymphatic system Circulatory system: Heart: a muscular pump to circulate the blood. Blood: a connective tissue of liquid plasma and Cells, tissues. Blood vessels: arteries, capillaries and veins that deliver blood to all tissues and cells. Lymphatic system: The lymphatic system consists of organs, vessels, capillaries, and nodes. Mention the Functions of circulatory system This system is involved in transport of nutrients and oxygen to the cells and removal of metabolic waste from the cells. Transport of hormones to target organs. Aids in the regulation of body temperature. Body defense- WBCs as antigens. Maintains water balance- blood plasma. Mention the Function of lymphatic system. To collect and return intestinal fluid, involving plasma protein to the blood, and thus help maintain fluid balance. To defend the body against disease by producing lymphocytes. To absorb lipids from the intestine and transport them to the blood. Discuss the Vascular Systems of farm animals. The invertebrates have the open type of circulator system whereas in higher vertebrates it is closed type. Former type lacks vessels where the blood is pumped in body cavity called as hemocoel therefore the flow of blood is sluggish. But, in closed type of circulatory system have the blood closed at all times within vessels of different size and wall thickness, so the flow of blood is not sluggish. 3 The Chambered heart completely separates oxygen-rich and oxygendepleted blood, as is shown in Figure 1. Fish have a two-chambered heart. Amphibians have a three-chambered heart with two atria and one ventricle. Birds and mammals have a four-chambered heart. Fig. 1 Images from Purves et al. Comprehend heart on following sub-topic: a) Location: b) Chambers: c) Valves: d) Layers: Anatomy of heart. Structures Right heart. Left heart Layers Atria (interatrial septum). Ventricles (interventricular septum). valves (Vena cavae, coronary sinus) → Right atrium (auricle) → tricuspid valve → right ventricle → pulmonary valve → (pulmonary artery and pulmonary circulation). (Pulmonary veins) → left atrium (auricle) → mitral valve → left ventricle → aortic valve (aortic sinus) → (aorta and systemic circulation). pericardium (sinus) • epicardium • myocardium • endocardium • 4 a) Location of heart. The construction, the form, and the position of heart are similar in all mammals. The connective tissue invests the heart which is called as “pericardium”. The pericardium is included within the mediastinum. It is conical and is placed asymmetrically within the thorax with larger part lying to the left of the median plane. The base is dorsal and reaches approximately to the horizontal plane that bisects the first rib; the apex is placed close to the sternum. The projection of pericardium upon the chest wall extends between the third and sixth ribs. Heart is under cover of the forelimbs. b) Chambers. As stated earlier all farm animals have all four chambers in the heart – two atria (auricle) and two ventricles they are referred as right and left according to their which region they are located. The two atria are separated by an internal septum called interatrial septum as are the two ventricles interventricular septum; but the atrium and ventricle of each side communicate through a large opening. The heart thus consists of two pumps that are arranged in series but combined within a single organ. The right pump receives de-oxygenated (venous) blood from the body and ejects it into the pulmonary trunk which carries it to the lungs for reoxygenation; the left pump receives the oxygenated (arterial) blood from the lungs and ejects it into the aorta which distributes it once more to the body. The sizes vary among the animals. The right atrium (in older texts termed the “right auricle”) This chamber lies mainly on the right. It receives de-oxygenated blood from the cranial and caudal vena cava and the coronary sinus, and pumps it into the right ventricle through the tricuspid valve. The sinoatrial node (SA node) is located within this chamber next to the vena cava. SA node is a group of pacemaker cells which spontaneously depolarize to create an action potential. 5 The left atrium (in older texts termed the “left auricle”) It receives oxygenated blood from the pulmonary veins, and pumps it into the left ventricle. Blood is pumped through the left atrioventricular orifice, which contains the mitral valve. The right ventricle It receives de-oxygenated blood from the right atrium via the tricuspid valve (right atrioventricular), and pumps it into the pulmonary artery via the pulmonary valve. It is triangular in form, and extends from the right atrium to near the apex of the heart. It’s under surface is flattened, rests upon the diaphragm, and forms a small part of the diaphragmatic surface of the heart. Its posterior wall is formed by the ventricular septum. Its upper and left angle forms a conical pouch, from which the pulmonary artery arises. The wall of the right ventricle is thinner than that of the left, But thicker than that of the atria. Between the atria and the ventricles are tricuspid valves, overlapping layers of tissue that allow blood to flow only in one direction. Valves are also present between the ventricles and the vessels leading from it. The left ventricle It receives oxygenated blood from the left atrium via the mitral (bicuspid) valve, and pumps it into the aorta via the aortic valve. The left ventricle is longer and more conical in shape than the right. It forms a small part of the sternocostal surface and a considerable part of the diaphragmatic surface of the heart; it also forms the apex of the heart. C) Valves The tricuspid valve is on the right side of the heart, between the right atrium and the right ventricle. The normal tricuspid valve usually has three leaflets and three papillary muscles. ***** The tricuspid valve also opens and closes at periods of time making the blood flow through from the right atrium to the right ventricle***** 6 The mitral valve (also known as the bicuspid valve or left atrioventricular valve), is a dual flap valve in the heart that lies between the left atrium (LA) and the left ventricle (LV). In Latin, the term mitral means shaped like a miter, or bishop's cap. The mitral valve and the tricuspid valve are known collectively as the atrioventricular valves because they lie between the atria and the ventricles of the heart and control flow. d) Layers Made up of three (3) distinct layers: The pericardium is a double-walled sac that contains the heart and the roots of the great vessels. the visceral layer, also known as the epicardium. Space called the pericardial cavity, which contains a supply of fluid. The serous fluid that is found in this space is known as the pericardial fluid enclosed by parietal and visceral pericardium. The layer next to the heart is 7 Great vessels heart Visceral pericardium Connective tissue Pericardial cavity Parietal pericardium Mediastinal pleura Sternopericardial ligament. Epicardium describes the outer layer of heart tissue (from Greek; epiouter, cardium heart). When considered as a part of the pericardium, it is the inner layer, or visceral pericardium apparently produces the pericardial fluid, which lubricates motion between the inner and outer layers of the pericardium. o Functions as an outer protective layer. o Serous membrane that consists of connective tissue covered by epithelium. o Includes blood capillaries, lymph capillaries, and nerve fibers. During ventricular contraction, the wave of depolarization moves from endocardial to epicardial surface. The muscles fibers of the heart are self-excitatory, means they can initiate contraction themselves without receiving signals from the brain. Myocardium is heart muscle Myocardium o Relatively thick. o Consists largely of cardiac muscle tissue responsible for forcing blood out of the heart chambers. o Muscle fibers are arranged in planes, separated by connective tissues that are richly supplied with blood capillaries, and nerve fibers. 8 Endocardium o Consists of epithelial and connective tissue that contains many elastic and collagenous fibers. o The innermost layer of tissue that lines the chambers of the heart. o Connective tissue also contains blood vessels and some specialized cardiacmuscle fibers called Purkinje fibers. o Lines all of the heart chambers and covers heart valves. The heart, shown in Figure, is a muscular structure that contracts in a rhythmic pattern to pump blood. An auricle is the chamber of the heart where blood is received from the body. A ventricle pumps the blood it gets through a valve from the auricle out to the gills through an artery. Images from Purves et al 9 Discuss the various blood vessels of farm animals. The blood vessels are the part of cardiovascular system The arteries, capillaries and veins form a continuous system lined by an unbroken low-friction, the tunica interna for the transportation of blood. Arteries carry blood away whereas veins towards the heart. Valves 10 The arteries the arterial wall is composed of three concentric tunics. The endothelium of the inner one (tunica interna) is supported by a thin layer of specialized connective tissue that is bounded externally by a well-developed, fenestrated elastic sheet, the inner elastic membrane. The middle tunic (tunic media) is the thickest and most variable layer. It is composed of an elaborately organized admixture of elastic tissue and smooth muscle in varying proportions. The outer tunic (tunic adventitia) is predominately fibrous. It is importance in limiting expansion of the artery, safeguarding against spontaneous rupture. A few very large arteries-those that are required to expand considerably when they receive the systolic output of the ventricles-have a media predominantly composed of concentric, fenestrated elastic membranes with relatively little muscle interspersed. The elastic tissue stretches to absorb and store the energy contained in the moving blood stream; later, on recoil, it releases this energy to forward the flow of blood toward periphery. For Example-The first part of aorta, certain of its major branches, and the pulmonary trunk. Whereas arteries and others of smaller size have a tunica media that consists largely of smooth muscle arranged in many closely spiraled layers. The smallest arteries, known as arterioles, principally regulate the resistance to the flow of blood and hence the peripheral blood pressure. They have reduced layers of muscle progressively. Though arterioles may be little wider than the capillaries into which they open, they are differentiated from the retention of some muscle in the wall. The capillaries and sinusoids the capillaries are reduced to narrow endothelial tubes supported by a very delicate connective tissue investment. Capillaries, the smallest blood vessels, are the site for the exchange of water and solutes between the blood stream and the interstitial fluid. Because of their small size, the capillaries are sometimes called as “Microcirculation”. They are also called as exchange vessels, because they exchange water and solutes between the blood stream and the interstitial fluid takes place across the walls of the capillaries. Minute pores are present in the capillaries which in some situation are like that of intestinal villi and renal glomeruli. Sinusoids are a special type of capillaries found in certain organs- liver, spleen, and bone marrow. They are wider, less regular, and more commonly fenestrated than the ordinary capillary and their endothelial cells are able to extract colloidal substances from the blood. 11 Microcircul ation (from Cunningha m) The veins. The construction of larger veins is similar to that of arteries. Anyhow the smallest one, the venules, do not posses muscle and may pass through several successive confluences before acquiring this component of the wall. The tunica interna is always thin and lacks an elastic membrane (therefore collapsed appearance); its chief distinction is its involvement in the formation of valves (repeated at the intervals along their length, which ensure a uni-directional flow and prevent reflux of blood when the circulation stagnates. Each valve consists of 2 or 3 semi-lunar cusps facing each other. 12 . Identify the components of lymphatic system. The system has two components. The first comprises a system of lymphatic capillaries and larger vessels that return intestinal fluids to the blood stream. The second compromises a variety of widely scattered aggregations of lymphoid tissue, including the many lymph nodes. The Lymphatic System includes o o o Lymph nodes located along the paths of collecting vessels. Isolated nodules of lymphatic patches in the intestinal wall. Specialized lymphatic organs such as the tonsils, thymus, and spleen The lymphatic system differs from the circulatory system in that the lymphatics do not form a closed ring or circuit. Instead, begin blindly in the intercellular spaces of the soft tissues of the body. 13 Lymph: is a clear, colourless liquid similar to plasma and it is formed during the metabolic exchange between the blood and the tissue. Lymphatic vessels- a plexus of lymphatic capillaries (Wall of the lymphatic capillary consists of a single layer) spread through most tissues collects a fraction of the interstitial fluid (the capillaries begins blindly which is called as lymphatic capillaries from the intercellular spaces), a fraction that is disproportionately important, since it contains protein and other large molecules unable to enter the less permeable blood vessels. The greater permeability of the lymphatic capillaries also allows them to take in particulate matter, including microorganisms on occasion. The fluid (lymph) they contain is generally pale, they are rarely conspicuous, though easily identified once seen. Lymphatic vessels resemble veins in structure with these exceptions: o o o o Lymphatics have thinner walls. Lymphatics contain more valves which directs in one direction i.e. to right. Lymphatics contain lymph nodes located at certain intervals along their course. Lymphatics play a critical role in homeostasis. 14 The Lymphatic Pump Although there is no muscular pumping organ connected with the lymphatic vessels to force lymph onward as the heart forces blood, still lymph moves slowly and steadily along its vessels. Occurs despite the fact that most of the flow is against gravity or "uphill". o It moves through the system in the right direction because of the large number of valves that permit fluid flow only in one direction. o The movement is due to breathing movements and skeletal muscle contractions. Activities that result in central movement or flow are called lymphokinetic actions. Research has shown that literally thoracic respiration leads lymph to “pumped" into the venous system during inspiration. The rate of flow of lymph into venous circulation is proportional to the depth of inspiration. Contracting skeletal muscles also exert pressure on the lymphatics to push the lymph forward. Other pressure generating factors: o o o Arterial pulsations Postural changes Passive compression (massage) of the body soft tissues Lymphatic nodes- are incorrectly termed lymph glands, are placed along the lymph pathways since they don’t secret substances, anyhow it filters lymph and produces lymphocytes which traps the antigen (foreign particles). The nodes are firm, smooth-surfaced, and generally ovoid or bean-shaped. Some are superficial which can be easily noticed on palpation through the skin. Lymph node: is the nodular gland or nodular structure located along the course of lymph vessels. It filters lymph and produces lymphocytes. 15 Each node is bounded by a fibrous capsule, a below which runs an open space (subcapsular sinus) into which the afferent vessels open at scattered sites. Inside the lymph node the fibrous capsule extends to form trabeculae (thin reticular fibers form a supporting meshwork inside the node i.e., Fibrous septa or trabeculae extend from the covering capsule toward the center of the node). Branches from the subcapsular sinus lead to a medullary sinus close to the generally indented (sunken) were the few efferent vessels emerge. The concave side of the lymph is called as hilum. The artery and vein are attached at the hilum and allows blood to enter and leave the organ, respectively. The lymph node is divided into an outer cortex and inner medulla. Cortex- in the cortex, the subcapsular sinus drains to corticoid sinusoids. Again due its different properties it is named as outer and inner cortex. It has got fluid made from the blood called plasma. 16 1=external and internal jugular veins. 2=lymph from head. 3=lymph from the shoulder and forelimb. 4=tracheal duct. 5=thoracic duct. 6=lymph from the thoracic organs. 7=cisterna chyli. 8=lymph from the abdominal organs. 9=lymph from the lumbar regions and kidneys. 10=lymph nodes of the pelvis. 11=lymph from the hind limb. Generalized scheme of the lymph nodes and lymphatic vessels (dorsal view). The top represents the neck region. (text book of vet.DYCE.SACK.WENSING. 17 1=parotid node. 2=mandibular nodes. 3=superficial cervical nodes. 4=accessory axillary node. 5=femoral node. 6=Popliteal node. From" Getty, 1975 Medulla – there are two named structures in the medulla: The medullary cords- are cords of lymphatic tissue, and include plasma cells and Tcells. The medullary sinus (or sinusoids) is vessel-like spaces separating the medullary cords. Lymph flows to the medullary sinus from cortical sinus, and into efferent lymphatic vessels. Medullary sinus contains histiocytes (immobile microphages) and reticular cells. The function of lymph nodes act as filters, with an internal honeycomb of reticular connective tissue filled with lymphocytes (the lymph nodes contain lymph nodules, germinal centers in which lymphocytes-B and T cells are produced) that collects and destroys bacteria and other antigen when the body is fighting an infection, lymphocytes multiply rapidly and produce a characteristic swelling of lymph nodes. The tissue of node is divided between cortical and medullary regions. The cortex (cortical) contains the germinal centers in which lymphocytes are continually produced, the medulla consists of looser branching cellular cords, and both the cortical and medullary sinuses are lined with specialized reticuloendothelial cells (fixed macrophages) capable of phagocytosis. 18 Lymph vessels and blood vessels both carry white blood cells. But lymph vessels carry lymph, not blood. They also carry nutrients that would not fit inside small blood vessels. Tonsils – the name is most often used specifically for those in the pharyngeal region where they guard against the passage of infection to deeper parts of the respiratory and digestive systems. 1) Palatine tonsils--located on each side of the throat. 2) Pharyngeal tonsils--also known as adenoids are near the posterior openings of the nasal cavity. 3) Lingual tonsils--near the base of the tongue 4) The tonsils serve as the first line of defense from the exterior and as such are subject to chronic infection—tonsillitis. 19 Schematic drawing of the palatine tonsils of cattle. Epithelium. Tonsillar sinus. Palatine tonsil. Efferent sinus. Thymus It is an organ whose importance is greatest in the young animal. It begins to regress about the time of puberty and may eventually almost disappear. The thymus has a paired origin from the third pharyngeal pouches, the buds grow down the neck beside the trachea and invade the mediastinum in which they extend to the pericardium. Structure of the thymus o The thymus is subdivided into small lobules by connective tissue septa that extend inward from a fibrous covering capsule. o Each lobule is composed of a sense cellular cortex and an inner less dense medulla. Both cortex and medulla are composed of lymphocytes in an epithelial framework. Got similar structures with that of lymph nodes. 20 Functions of the Thymus o Thymus performs two important functions: Serves as a final site of lymphocyte development before birth. Soon after birth the thymus begins secreting a group of hormones collectively called thymosin that enable lymphocytes to develop into mature T-cells. Spleen Location of the Spleen o It is contained within the left cranial part of the abdomen where it is joined to the greater curvature of the stomach. Structure of the Spleen – the basis form is very dissimilar in the various domestic species, being dumb-bell in the dog and cat; strap-like in the horse. Because of its whitish appearance, this tissue is called white pulp. Near the outer regions of each compartment is tissue called red pulp made up of fine reticular fibers submerged in blood that comes from nearby arteries. Functions of the Spleen Defense o As blood passes through the sinusoids, reticuloendothelial cell (macrophages) lining these venous spaces remove microorganisms from the blood and destroy them by phagocytosis. Hematopoiesis o Monocytes and lymphocytes complete their development to become activated in the spleen. o Before birth, red blood cells are also formed in the spleen. Red blood cell and platelet destruction. o Macrophages lining the spleen's sinusoids remove worn-out red blood cells and imperfect platelets from the blood and destroy them by phagocytosis. o Also break apart the hemoglobin molecules from the destroyed red blood cells and salvage their iron and globin content by returning them to the blood stream for storage in bone marrow and liver. Blood reservoir - Pulp of the spleen and its venous sinuses store considerable blood which can be released during hemorrhage. 21 Briefly describe Lymphatic circulation. Lymph circulates to the lymph node via afferent lymphatic vessels and drains into the node just beneath the capsule in a space called the subcapsular sinus. The subcapsular sinus drains into trabecular sinus and finally into medullary sinus. The sinus space is criss-crossed by the pseudo or pseudopodia (false feet) of macrophages that act to trap foreign particles and filter the lymph. The medullary sinus converges at the hilum and lymph then leaves the lymph node via the efferent lymphatic vessel. Lymphocytes, both B and T cells, constantly circulate the lymph nodes. They enter the lymph node via the blood stream and cross the wall of blood vessels by process of diapedesis. The B cells migrate to the nodular cortex and medulla. The T cells migrate to the deep cortex. When a lymphocytes recognizes an antigen, B cells become activated and migrate to germinal centers (by definition, a “secondary nodule” has a germinal center, while a “primary nodule” does not). When antibody- producing plasma cells are formed, they migrate to the medullary cords. Stimulation of the lymphocytes by antigens can accelerate the migration process to about 10 times normal, resulting in characteristic swelling of the lymph nodes. The spleen (left cranial part of the abdomen, joined to the greater curvature of the stomach) and tonsils are larger lymphoid organs that serve similar functions to lymph nodes, though the spleen filters blood cells rather than bacteria or viruses. 22 Identify the various paths or circuits way taken by the blood. Circulatory circuits-Three circuits are 1. Pulmonary circuit 2. Systemic circuit 3. Coronary circuit The pulmonary circulation- such circulation the blood starts or leaves the heart through the pulmonary arteries, goes to the lungs, and returns to the heart through the pulmonary veins. The right heart, pulmonary artery, lung and pulmonary vein are involved in pulmonary circulation. The pulmonary arteries: the pulmonary trunk arises from the pulmonary orifice of the right ventricle. It is slightly expanded at its origin where it presents a small sinus above each cusp of the pulmonary valve. The trunk, passes between the two atria, then bends caudally over the base of the heart where it is joined on its right face by ligament. After penetrating the pericardium it divides into right and left pulmonary arteries, each directed to the hilus of the corresponding lung, where it ramifies for their function. The pulmonary veins: it opens variously into the roof of the left atrium. Valves are absent. The systemic circulation- the blood leaves the heart through the aorta. Goes to all the organs of the body through the systemic arteries, and then returns to the heart through the systemic veins. Left heart, vessels in the cranial part of the body, aorta, liver, intestine, portal vein, kidneys, vessels in the caudal part of the body, caudal vena cava, and cranial vena cava. The systemic arteries: The aortic arch and its ramification= the origin of the aorta is similar to that of the pulmonary trunk but is from the left ventricle. The initial portion, the aortic bulb, is concealed between the atria and forms sinuses above the three cusps of aortic valve. Following are the its ramifications, Coronary arteries- run cranially, dorsally and caudally penetrating the pericardium. Paired subclavian artery- supplies blood to forelimb and to structures of the neck and cervicothoracic. Paired carotid artery- they supplies blood to brain, face. Costocervival trunk-the second largest branch provides the first few intercostal arteries and the deep cervical artery. 23 The internal thoracic artery- the third branch provides to thoracic and sternum which extends till abdomen. The superficial cervical artery- fourth branch arises from the subclavian which supplies to muscles of the ventral part of the neck, the cranial part of shoulder, and the upper arm. The axillary artery= supplies blood to forelimb. The thoracic aorta= it runs caudally below the roof of the thorax to enter the abdomen. Abdominal aorta= it follows the roof of the abdomen. The external Iliac artery= is the principle artery of the hind limb. The internal Iliac artery= supply of the pelvic viscera and walls. The systemic veins: Veins returns blood to the heart through the cranial venacava, caudal vena cava, and coronary sinus (returns the bulk of blood from the heart wall). The cranial vena cava= is formed close to the entrance to the chest. The veins corresponding to artery of aorta and its ramification (which provides blood above abdomen) connects with it. The caudal vena cava= it is formed on the roof of the abdomen, near pelvic inlet. Coronary circulation- the heart muscle is supplied by its own set of blood vessels. These are called as coronary arteries. The coronary arteries are classified as "end circulation", since they represent the only source of blood supply to the myocardium. 24 Describe the cardiovascular circulation. The work of the heart is to pump blood to the lungs through pulmonary circulation and to the rest of the body through systemic circulation. This is accomplished by systematic contraction and relaxation of the cardiac muscle in the myocardium. cardiovascular system, showing that the systemic and pulmonary circulations are arranged in series and that the organs within the systemic 25 General layout of the cardiovascular system, showing that the systemic and pulmonary circulations are arranged in series and that the organs within the systemic circulation are arranged in parallel. (adapted from Milnor WR:cardiovascular physiology. NY, oxford Unv Press,1990) 26 Other parts of the conduction system include the atrioventricular node, AV bundle, bundle of His, Purkinje’s fibers. All these components coordinate the contraction and relaxation of the heart chambers. Sleeping 50 awake 100 walking running 150 200 defence reaction. 250 Heart Rate (beats/min) of dog. 27 Conduction System An effective cycle for productive pumping of blood requires that the heart be synchronized accurately. Both atria need to contract simultaneously, followed by contraction of both ventricles. Specialized cardiac muscle cells that make up the conduction system of the heart coordinate contraction of the chambers. The conduction system includes several components. The first part of the conduction system is the sinoatrial node. Without any neural stimulation, the sinoatrial node rhythmically initiates impulses. Because it establishes the basic rhythm of the heartbeat, it is called the pacemaker of the heart. Other parts of the conduction system include the atrioventricular node, AV bundle, bundle of His, Purkinje’s fibers. .All these components coordinate the contraction and relaxation of the heart chambers. 28 Cardiac Cycle - The cardiac cycle refers to the alternating contraction and relaxation of the myocardium in the walls of the heart chambers, coordinated by the conduction system, during one heartbeat. Systole is the contraction phase of the cardiac cycle, and diastole is the relaxation phase. The contraction of the heart and the action of the nerve nodes located on the heart. Images from Purves et al. 29 The below shows the relationship between Electro Cardio Graph (ECG) and transmission of impulse throughout the heart. Heart Sounds – The sounds associated with the heartbeat are due to vibrations in the tissues and blood caused by closure of the valves. Abnormal heart sounds are called murmurs. Heart Rate -The sinoatrial node, acting alone, produces a constant rhythmic heart rate. Regulating factors are reliant on the atrioventricular node to increase or decrease the heart rate to adjust cardiac output to meet the changing needs of the body. Most changes in the heart rate are mediated through the cardiac center in the medulla oblongata of the brain. The center has both sympathetic and parasympathetic components that adjust the heart rate to meet the changing needs of the body, former increases latter decreases the heart beat. Peripheral factors such as emotions, ion concentrations, and body temperature may affect heart rate. These are usually mediated through the cardiac center. 30 Pulse: is the wave of pressure that spreads through the arteries when the blood is forced into the aorta with each heart beat. The rate of the pulse is the number of pulse per minute and it is directly proportional to temperature and respiration. Undertake a brief view on the blood composition and functions. The blood is a complex liquid tissue that transports nutrients, respiratory gases, metabolic products and other substances from one part to the other parts of the body. The flow chart below shows the types of blood: Blood Erythrocytes (RBC) Leucocytes (WBC) Granulocytes Eosinophil Basophil Thrombocytes (Platelets) Agranulocytes Monocytes Lymphocytes Functions of blood o o o o o o o Contains phagocytic cells that fight infection- Leucocytes are for body defence mechanism. It phogocytose the microbes (that cause infection) invading the body. Erythrocytes are involved in gaseous exchange, transport of nutrients and removal of metabolic waste. Carry hormones from endocrine glands to target cells Maintain water balance. Prevent excess loss of blood by clotting- Thrombocytes are involved in the clotting of the blood. Contains chemicals that buffer internal pH. Helps maintain normal body temperature. Blood constituents Plasma, Serum, Cells. 31 60% of total. 1) Plasma- Blood minus cells. The plasma is a slightly alkaline fluid, with a typical yellowish color. It consists of 90 % water and 10% dry matter. Nine parts of it are made up by organic substances, whereas one part is made up by minerals. These organic substances are composed of glucides (glucose), lipids (cholesterol, triglycerides, phospholipids, lecithin, and fats), proteins (globulins, albumins, and fibrinogen), glycoproteins, hormones, amino acids and vitamins. The mineral substances are dissolved in ionic form that is dissociated into positive and negative ions. 2) Serum- Plasma minus fibrinogen, Straw colored fluid left after clotting. 3) Cells- Formed structures in blood, Different types seen are ERYTHR0CYTES (RED BLOOD CELLS )In lower vertebrates and birds, the RBCs are nucleated. In mammals, the RBCs are anucleated and have the shape of a biconcave lens. RBCs form from stem cells in the bone marrow. The erythrocytes are the most numerous blood cells. The red cells are rich in hemoglobin, a protein able to bind in a faint manner to oxygen. Hence, these cells are responsible for providing oxygen to tissues and partly for recovering carbon dioxide produced as waste. However, most CO2 is carried by plasma, in the form of soluble carbonates. 32 In the red cells of the mammalians, the lack of nucleus allows more room for hemoglobin and the biconcave shape of these cells raises the surface and cytoplasmic volume ratio. These characteristics make more efficient the diffusion of oxygen by these cells. In so-called "sickle-cell anaemia", erythrocytes become typically sickle-shaped. LEUKOCYTES (white cells) White blood cells (leukocytes) (nucleated, phagocytic cells that remove worn-out RBCs and unwanted cell debris from the bloodstream. Leukocytes are also formed from stem cells in the bone marrow. There are five types: Lymphocytes (B and T cells of immune system), monocytes (differentiate into macrophages), neutrophils (60% of WBCs), eosinophils, and basophils (allergic responses) . monocyte Lymphocyte basophil eosinophil neutrophil Leukocytes, or white cells, are responsible for the defense of the organism. In the blood, they are much less numerous than red cells. Leukocytes divide in two categories: granulocytes and lymphoid cells or agranulocytes. The term granulocyte is due to the presence of granules in the cytoplasm of these cells. In the different types of granulocytes, the granules are different and help us to distinguish them. In fact, these granules have a different affinity towards neutral, acid or basic stains and give the cytoplasm different colors. So, granulocytes distinguish themselves in neutrophil, eosinophil (or acidophil) and basophil. The lymphoid cells, instead, distinguish themselves in lymphocytes and monocytes. PLATELETS The main function of platelets, or thrombocytes, is to stop the loss of blood from wounds (hematostasis). To this purpose, they aggregate and release factors which promote the blood coagulation. They are much smaller than erythrocytes. 33 T- Lymphocytes Platelets RBCs Brief the Clinical importance 1. Anaemia: is a condition in which either there is less red blood cells (RBC) in circulation or haemoglobin content in RBC. Anaemia can occur when there is heavy parasite infestation (endoparasite or ectoparsite), haemorrhage (internal of external) can also result in anaemia. Protozoan infections like Babesiosis cause anaemia due heavy destruction of RBC. 2. Oedema: Is the accumulation of fluid in tissue. This mainly due to imbalance in osmotic pressure between blood and tissue. This is seen when there is heavy parasite like Liver fluke infestation causing decrease in blood protein level that reduces osmotic pressure in blood resulting in drainage of fluid from blood into tissue in dependent parts. 34 35 References. 1) http://images.google.com/imgres?imgurl=http://education.vetmed.vt.edu/Curriculum/VM8054 /Labs/Lab13/IMAGES/THYMUS%2520COMPOSITE%2520SMALL.jpg&imgrefurl=http://edu cation.vetmed.vt.edu/Curriculum/VM8054/Labs/Lab13/Lab13.htm&h=413&w=864&sz=114&hl= en&start=3&um=1&tbnid=kOg1FB4xsTkKdM:&tbnh=69&tbnw=145&prev=/images%3Fq%3Dthy mus%2Bof%2Bcattle%26svnum%3D10%26um%3D1%26hl%3Den 2) Notes for diploma (by Dr. Penjor and Nidup. K) 3) http://images.google.com/imgres?imgurl=http://www.ucd.ie/vetanat/images/65.gif&imgrefurl =http://www.ucd.ie/vetanat/images/image.html&h=550&w=845&sz=146&hl=en&start=9&um=1 &tbnid=k1_z53cv_aHqtM:&tbnh=94&tbnw=145&prev=/images%3Fq%3Ddeep%2Blymph%2Bdra inage%2Bof%2 4) http://images.google.com/imgres?imgurl=http://www.ucd.ie/vetanat/images/65.gif&imgrefurl =http://www.ucd.ie/vetanat/images/image.html&h=550&w=845&sz=146&hl=en&start=9&um=1 &tbnid=k1_z53cv_aHqtM:&tbnh=94&tbnw=1 45&prev=/images%3Fq%3Ddeep%2Blymph%2Bdrainage%2Bof%2Bthe%2Bdog%2B%26svnum%3D1 0%26um%3D1%26hl%3Den%26sa%3DG. 36