Cardiovascular System PDF

The CARDIOVASCULAR SYSTEM 2024  Objectives: To know the functions of the cardiovascular system To identify the cardiovascular system structures and each of their functions To name some diseases associated with this system  THE CARDIOVASCUL...

The CARDIOVASCULAR SYSTEM 2024  Objectives: To know the functions of the cardiovascular system To identify the cardiovascular system structures and each of their functions To name some diseases associated with this system  THE CARDIOVASCULAR SYSTEM ✔ Cardio = HEART ✔ Vascular = Blood vessels ✔ Also called Circulatory System ✔ Consists of the HEART, BLOOD VESSELS and closely assoc. with the LYMPHATIC system  ▪ Heart: pumping action ensures constant circulation of the blood ▪ Blood Vessels: form a lengthy network through which the blood flows ✔ The lymphatic system is closely connected, both structurally and functionally, with the cardiovascular system Functions Functions Functions  HEART ✔its weight is about 250-300 g ✔Situated in the middle of the mediastinum behind the breastbone in the chest (located in the chest between the lungs behind the sternum and above the diaphragm) ✔ In the average lifetime the heart beats 250 million times and pumps 340 million litres of blood ✔The heart is a sophisticated pump that is controlled by an electrical current that is initiated in the brain  ▪ 3 layers – the pericardium (tunica The heart wall adventitia) is made up of two sacs: the outer sac consist of fibrous tissue – the myocardium (tunica media) is the muscle layer and responsible for heart contractility – the endocardium(tunica intima) this lines the chamber and valves of the heart; permits smooth flow of the blood inside the heart Four CHAMBERS of the Heart ***Chordae tendineae : strong, fibrous connections between the valve leaflets and the papillary muscles 5 distinct types of BLOOD VESSELS Blood vessels Arteries: distribute oxygen-rich blood to your body Arterioles: a small branch of an artery leading into capillaries; feed the capillary beds in the tissues Capillaries: smallest and most numerous of the blood vessels; form the connection between arteries and veins Veins: collect oxygen-poor blood and return it to the heart Venules: smallest veins and receive blood from capillaries ✔Control of blood vessel diameter Vasoconstriction When nervous activity is increased, the smooth muscle of tunica media contracts and thickens Decreased nerves stimulation relaxes the smooth muscle thinning the vessel wall and enlarging the lumen = Vasodilation Conducting system of the heart ✔ Small group of specialized neuromuscular cells in the myocardium initiate and conduct impulses, causing coordinated and synchronized contraction of the heart muscle ✔The conduction system of the heart contains pacemaker cells, which have (3) three unique characteristics: Automaticity. The ability to generate an electrical impulse automatically Conductivity. The ability to pass impulse to the next cell Contractility. The ability to shorten fibers in the heart when receiving impulse.  Purkinje fibers - specialized conducting fibers composed of electrically excitable cells - allow the heart's conduction system to create synchronized contractions of its ventricles - essential for maintaining a consistent heart rhythm SA node/ Sinoatrial node / Superior node - acts as the normal pacemaker of the heart - It initiates an action potential that results in an electrical impulse traveling through the heart’s electrical conduction system to cause myocardial contraction ✔Impulse conduction Sinoatrial node (SA node) -Mass of specialized cells -Lies in the wall of right atrium -Is the pacemaker of heart -Firing of SA node causes atrial contraction  Atrioventricular node (AV node) – situated in the wall of atrial septum near the atrioventricular valve – conducts the impulse that arrive from SA node, passes it through AV bundle (Bundle of His) and purkinje fibres which in turn convey the impulse to the ventricle ✔3 methods of circulation Coronary circulation Pulmonary circulation Systemic circulation https://youtu.be/x2R0_lBr_zk  Coronary circulation is an important and essential part of the human body’s systemic circulatory pathway The coronary arteries are located on the outside of the heart Without them, the heart tissue would not receive blood, nutrients or oxygen AORTA - largest artery in the body - an inch wide in diameter - receives the cardiac output from the left ventricle and supplies the body with oxygenated blood via the systemic circulation Ascending Aorta arises from the aortic orifice from the left ventricle and ascends to become the aortic arch Aortic Arch continuation of the ascending aorta ends at the level of the T4 vertebra Branches 1.Brachiocephalic trunk: first and largest branch that ascends laterally to split into the right common carotid and right subclavian arteries supplying the right side of the head and neck, and the right upper limb Aortic Arch 2. Left common carotid artery: Supplies the left side of the head and neck 3. Left subclavian artery: Supplies the left upper limb Thoracic Aorta - descending aorta - spans from the level of T4 to T12 - leaves the thorax via the aortic hiatus in the diaphragm, and becomes the abdominal aorta - Branches 1. Bronchial arteries: supply bronchial and peribronchial tissue and visceral pleura Thoracic Aorta 2. Mediastinal arteries: supply the lymph glands and loose areolar tissue in the posterior mediastinum 3. Esophageal arteries: supply the esophagus 4. Pericardial arteries: supply the dorsal portion of the pericardium 5. Superior phrenic arteries: Paired parietal branches that supply the superior portion of the diaphragm 6. Intercostal and subcostal arteries: 9 pairs of intercostal arteries supply the intercostal spaces, with the exception of the first and second (they are supplied by a branch from the subclavian artery) - The subcostal arteries supply the flat abdominal wall muscles Abdominal Aorta - continuation of the thoracic aorta beginning at the level of the T12 vertebrae - approximately 13 cm long and ends at the level of the L4 vertebra - At this level, the aorta terminates by bifurcating into the right and left common iliac arteries that supply the lower body  Cardiac Cycle Period from the beginning of one heartbeat to the beginning of the next Electrical and mechanical events must occur in the proper sequence and to the proper degree to provide adequate blood flow to all the body parts  Has (2) two phases: Systole-the phase of the heartbeat when the heart muscle contracts and pumps blood from the chambers into the arteries Diastole-the phase of the heartbeat when the heart muscle relaxes and allows the chambers to fill with blood  Stroke volume: volume of blood pumped out of the left ventricle of the heart during each systolic cardiac contraction - depends on (3) three major factors: ✔ Preload- stretching of muscle fibers in the ventricles ✔ Contractility- inherent ability of the myocardium to contract normally. This is influenced by preload. The greater the stretch the more forceful the contraction. ✔ Afterload-refers to the pressure that the ventricular muscles must generate to overcome the higher pressure in the aorta to get the blood out of the heart.