Circulatory System in Animals Organs of the cardiovascular system -Circulatory system made up of: 1- organ: -heart 2- tissues & cells: a-blood vessels -arteries -veins -capillaries b- blood: -red blood cells -plasma The blood vessels are arranged as two circuits of blood flow, following a figure of 8 pattern with the heart in the centre. The larger, systemic circulation conveys oxygenated blood from the heart to all the organs of the body and transports deoxygenated blood back to the heart. The smaller, pulmonary circulation conveys deoxygenated blood from the heart to the exchange tissue of the lungs, where it is oxygenated before it is returned to the heart. Circulatory systems open closed hemolymph blood • In fishes the blood only passes through the heart once on its way to the gills and then r o u n d t h e r e s t of t h e b o d y . • However, in mammals and birds that have lungs, the blood passes through the heart twice: once on its way to the lungs where it picks up oxygen and then through the heart again to be pumped all over the body. The heart is therefore two separate pumps, side by side Vertebrate Heart • 4-Chambered heart – atria (atrium) • thin wall • collection chamber left • receive blood atrium – ventricles right • thick wall pump atrium • pump blood out right left ventricle ventricle Lub-dub, lub-dub • 4 valves in the heart – flaps of connective tissue – prevent backflow • Heart sounds – closing of valves SL – “Lub” • force blood against AV closed AV valves AV – “Dub” • force of blood against semilunar valves • Heart murmur – leaking valve causes hissing sound – blood squirts backward through valve Pericardium • The pericardium, or heart sac, is the fibroserous covering of the heart. It is essentially a deeply invaginated sac, contains a small amount of serous fluid (liquor pericardii) which facilitates movement of the heart against the pericardium. • The pericardium can be divided 1- Serous pericardium -Visceral layer - Parietal layer 2 - Fibrous pericardium • The visceral layer of the pericardium is firmly attached to the heart wall, forming the epicardium. It covers the myocardium, the coronary vessels and fat on the surface of the heart. • The parietal layer of the serous pericardium is firmly fused to the fibrous pericardium. • The base of the fibrous pericardium is continuous with the great arteries and veins that leave and enter the heart, uniting with the adventitia of these vessels. Ventrally it continues into the following ligaments: Sternopericardiac Phrenopericardiac ligament ligament (only present in the dog ) Position and size of the heart • The heart is located within the mediastinum with the larger part (60%) lying to the left of the median plane. It extends between the third and sixth (seventh in the cat and dog) rib. The heart base is roughly located on a horizontal plane drawn through the middle of the thorax. Most of the surface of the heart is covered by the lung, • Variations in position and size occur among species, breeds and individuals, according to age, condition and the presence of disease. As a rough guide, the heart provides about 0.75% of the body weight. Compartments of the heart • The heart is divided internally by a longitudinal interatrial & interventricular septum into left and right sides. These in turn are incompletely divided by a transverse septum into the blood receiving atria (atrium cordis) and the blood-pumping ventricles The right atrium • forms the right, dorsocranial part of the base of the heart. • It receives the blood from the cranial and caudal vena cava and the coronary sinus (sinus coronarius), which collects the venous blood from most of the heart itself. • It is divided into a main part, the sinus of the venae cavae (sinus venarum cavarum) and a blind-ended part, the right auricle. It is separated from the left atrium by the interatrial septum • The intervenous tubercle is a transverse ridge of tissue between the openings of the two vena cavae, protrudes into the interior of the right atrium. • It directs the inflow of blood through the Right atrioventricular opening. • Just caudal to this tubercle, on the interatrial septum is a depressed area, the oval fossa, which is the remnant of the foramen ovale of foetal development. • The internal surface of the wall of the right auricle is strengthened by interlacing muscular bands (pectinat ms). Left atrium The left atrium forms the left, dorsocaudal part of the base of the heart. It receives the oxygenated blood from the pulmonary veins. It is similar to the right atrium in shape and structure It opens into the left ventricle by the left atrioventricular opening. Several openings mark the entrance of the pulmonary veins into the left atrium. .