Cardiovascular System I 2024 PDF

Cardiovascular System I Dr Rodi O. Ojoo Dr R.Ojoo 1  Cardiovascular System o Types of Circulatory systems among the living animals: o The Open transport system o The Closed transport systems o (i) Open Transport System: o Blood is contained in the coelomi...

Cardiovascular System I Dr Rodi O. Ojoo Dr R.Ojoo 1  Cardiovascular System o Types of Circulatory systems among the living animals: o The Open transport system o The Closed transport systems o (i) Open Transport System: o Blood is contained in the coelomic spaces bathing the various body organs. o Suitable for relatively sedentary animals e.g. nematode worms. o Circulation is achieved when the animal moves due to muscular contractions. o Arthropods (like insects) have an open circulatory system with a tubular heart equipped with valves to enable uni-directional movement of the blood within the coelomic cavities. o Insect circulatory system does not participate much in gaseous exchange as they have an efficient tracheal system for this. Dr R.Ojoo 2  Cardiovascular System o (ii) Closed Transport Systems: o In this system circulating blood is confined to a system of branching vessels driven by a heart. o Is the type of circulation in vertebrates (mammals, birds, fish). o Types of Closed Circulatory Systems/Transport Systems: o Single Circulatory system o Incomplete Double circulatory system o Complete Double circulatory system Dr R.Ojoo 3  Cardiovascular System o (i) Single Circulatory System o Found in fish. There is a tubular heart which pumps blood to the gill capillaries where gaseous exchange occurs then to larger vessels that distribute oxygenated blood to the body organs. o Venous system returns blood to the heart. o (ii) Incomplete Double circulatory System: o There is a heart partially partitioned into left and right halves with intercommunication between the left and right ventricles. Dr R.Ojoo 4  Cardiovascular System o There is: (i) pulmonary and skin circulation (ii) systemic circulation. o Blood from right ventricle to lungs or skin circulation. o From lungs to left atrium, left ventricle, body organs then back to right atrium together with skin blood.e.g. Amphibians Dr R.Ojoo 5  Cardiovascular System o (iii) Complete Double Circulation: o Type of circulation found in mammals and birds. o Will be discussed in detail. o In mammalian development this is one of the first systems to acquire functional capacity to facilitate efficient supply of oxygen and nutrients to body tissues and organs. Dr R.Ojoo 6  Cardiovascular System o This system comprises: o A central pumping organ (the heart), o Arteries that convey blood away from the heart to body organs (efferent vessels), o Veins that convey blood from body organs toward the heart (afferent vessels), o Blood capillaries: these are the smallest blood vessels found in body organs, in which exchange of material between the body tissues and blood occurs. o Within the cardiovascular system are three forms of circulation namely; o (i) Systemic Circulation: This is where there is flow of blood from the left ventricle to systemic arteries that supply the body organs and eventually this blood from organs is returned to the right atrium of heart via the 7 systemic veins.  Cardiovascular System o (ii) Pulmonary Circulation: This is where there is blood flow from the right ventricle of the heart to the lungs and back to the left atrium o (iii) Portal Circulation: This is where there is uninterrupted flow of blood from one capillary bed to another (without passing through the heart) Dr R.Ojoo 8  Cardiovascular System o Terminology: o Angiology: G:angios vessel logos:treatise/discourse o Vascular plexus: a network of blood vessels o Anastomosis: intercommunication of adjacent vessels o Retia Vasculosa; a wide mesh/net work of vessels o Rete mirabile: vascular network intercalated in the course of an artery o Collateral vessels: vessels that pursue a course near and similar to that of a large vessel. Common in the limbs o Collateral Circulation: where a main artery gives off branches before its termination. These branches often anastomose with each other ensuring alternate vascularization of the organ. o Vena comitans: A satellite vein that accompanies an artery o Venous sinuses: Thin walled veins enclosed in dense membranes and are usually found running in bony grooves e.g in cranium o Emissarium: A vein connecting venous sinuses to veins outside the cranium o Corpus Cavernosum: An erectile structure consisting of intercommunicating blood spaces lined with an endothelium and enclosed by smooth muscle and fibroelastic tissue. Dr R.Ojoo 9  Cardiovascular System o The Heart (Cor): o Is the central pump in the circulatory system. o Consists of two pumps arranged in series: a right pump comprising right atrium and right ventricle, left pump comprising left atrium and left ventricle. (L:Atrium = entrance chamber L: ventriculus=small belly) o Right pump receives deoxygenated blood from systemic veins while the left pump receives oxygenated pulmonary blood from pulmonary veins. Outflow is via the pulmonary trunk and aorta respectively. o Heart pumps 80% of the blood volume every minute (dog) while in the horse the entire blood volume (100%) is pumped every minute and in humans it is 60% of the blood volume. Dr R.Ojoo 10  Cardiovascular System o Topography: o Heart is located in middle mediastinum. o Mediastinum: Is a sagitally placed partition or potential space enclosed by the left and right mediastinal portions of the pleural membranes (pleura) lying back-to-back and extending from the thoracic inlet to the diaphragm caudally. o The pleural membranes attach to the ventral parts of thoracic vertebrae dorsally and to the sternum ventrally. o The mediastinum is divided into a cranial mediastinum that lies cranial to the heart, middle mediastinum and caudal mediastinum. o Enclosed within the mediastinum are various thoracic visceral organs and blood vessels. Pleura: there is the costal pleura lining the ribs, diaphragmatic pleura lining the diaphragm and mediastinal pleura. 11  Cardiovascular System o Relations Relations of heart in bovine o Dorsally and laterally related to the lungs and heart forms cardiac impressions on both the left and right lungs. Impression is deeper on the left lung. o Also dorsally related to the trachea, oesophagus, vagal trunks and large blood vessels. o Dorsolaterally related to the phrenic nerves and caudally related to the diaphragm and cranial abdominal organs. Cranially in young animals, it is related to the thymus. o *In ruminants the heart is closely related to the reticulum that lies immediately caudal to the diaphragm. This is of clinical importance in the bovine as nails or sharp objects lodged in the reticulum can actually pierce the 12 heart and its coverings.  Cardiovascular System o Positioning o Its construction and positioning is generally similar in all the domestic animals. o Most of the heart is invested by the pericardium. The pericardium in turn is invested by the mediastinal pleura. o The heart is asymmetrically positioned in the thoracic cavity with 60% of it lying to the left of the median plane. It is cone shaped with an apex ventrally and a base dorsally. o Pig and carnivores its long axis is inclined at an angle of