C6 Combined SAMS Notes PDF

The Components of Cardiovascular system are: Blood Blood vessels –arteries, veins, capillaries Heart Functions of Cardiovascular system 1. Transport Gases – Oxygen, carbon dioxide, nitrogen Nutrients – glucose, amino acids, vitamins, proteins, lipids Metabolic wastes – urea, uric acid, creatinine, a...

The Components of Cardiovascular system are: Blood Blood vessels –arteries, veins, capillaries Heart Functions of Cardiovascular system 1. Transport Gases – Oxygen, carbon dioxide, nitrogen Nutrients – glucose, amino acids, vitamins, proteins, lipids Metabolic wastes – urea, uric acid, creatinine, ammonium ions Regulatory molecules – hormones, enzymes Processed molecules – proteins, enzymes, carbohydrates, lipids 2. Protection Inflammation Phagocytosis Antibodies Platelets for clotting 3. Regulation Fluid balance pH Body temperature Blood pressure Exchange between blood, extracellular fluid and cells Heart Function: Pump - generate pressure in the blood Routes blood – separate pulmonary and systemic circulation One-way flow Regulate blood supply Heart Protection Ribcage Protective membranes Fluids Heart Location Located in the Thoracic cavity, sits obliquely in the mediastinum, is medial to the two lungs, is superior to the diaphragm Size of closed fist 250-300g Blunt cone, 2/3rd towards left side of midline the rounded end is the apex, anteriorly & inferiorly pointed, above the diaphragm broader end is base, directed posteriorly and slightly superiorly Heart Pericardium Fibrous pericardium: tough fibrous outer layer, prevents overdistention; acts as anchor. Serous pericardium: thin, transparent, inner layer, simple squamous epithelium. Parietal pericardium: lines the fibrous outer layer Visceral pericardium: covers heart surface The parietal pericardium and visceral pericardium layers of the serous membrane are continuous and have a pericardial cavity between them filled with pericardial fluid Heart – morphology (how does it look): Anterior and posterior sides of the heart contain major vessels. The anterior side contains the aorta, pulmonary trunk and anterior interventricular sulcus The posterior side contains lots of smaller blood vessels and the atrial wall. The heart has three Sulci (grooves) The coronary sulcus separates the atria and the ventricles. The anterior interventricular sulcus demarcates the separation between the right ventricle and the left ventricle The posterior interventricular sulcus is the continuation of the anterior interventricular sulcus and separates the right ventricle and left ventricle on the posterior side of the heart. The sulci run the coronary circulation of the blood vessels that supply the heart. Pericardial & epicardial fat Pericardial fat is lies between visceral and parietal pericardium Epicardial fat lies between the outer layer of myocardium and the visceral layer of the pericardium (epicardium) Four chambers: The artia are the superior chambers. The artia are collecting chambers. The ventricles are the Inferior chambers. The ventricles are the discharging chambers. The atrial walls are thin and the ventricular walls are thick. The tissue of the heart wall is made of three layers: Epicardium: The epicardium is the outermost layer of the heart wall tissues. It is a serous membrane; simple squamous epithelium over areolar tissue, a smooth outer surface of the heart. The epicardium is also called the visceral pericardium. Myocardium: The myocardium is the middle layer of the heart wall tissue. It is the thickest, it is composed of cardiac muscle cells and can contract. Endocardium: The endocardium is the innermost layer of the heart wall tissue. It is the smooth inner surface of heart chambers, squamous epithelium over areolar tissue, covers valve surface &it is continuous with endothelium Heart anatomy: Interventricular septum is separation between two ventricles Inter atrial septum is the wall between the atria. Contains a depression, fossa ovalis which is a remnant of the fetal opening (foramen ovale) between the atria. Pectinate muscles are muscular ridges in auricles and atrial wall. Trabeculae carnae: muscular ridges and columns on inside walls of ventricles The l eft ventricle wall is much thicker than the right ventricle wall. The Right atrium- Heart Chambers: The right atrium is a thin-walled receiving chamber and most of the right atrium is on the posterior side of the heart. The right atrium contains auricles which are extensions are extensions to increase volume. The right atrium contains pectinate muscles for large force of contraction The right atrium receives deoxygenated blood returning from the body through three openings: the Superior vena cava, the inferior vena cava and the coronary sinus. The Right ventricle- Heart Chambers: The right ventricle Pumping/discharging chamber. Most of the right ventricle is on the anterior side of the heart. The right ventricle has thicker walls than atria. The right ventricle receives deoxygenated blood from the right atrium. The right ventricle opens to the pulmonary trunk. The left ventricle contains trabeculae carnae. The Left Atrium- Heart Chambers: The left atrium is a thin-walled receiving chamber. Most of the left atrium is on the posterior side of the heart. The left atrium forms the heart’s base. The left atrium contains auricles which are extensions that increase volume. The left atrium contains pectinate muscles for large force of contraction. The left atrium receives oxygenated blood returning from lungs through four openings which are the four pulmonary veins. The Left ventricle- Heart Chambers: The left ventricle is a pumping/discharging chamber. The left ventricle forms the apex and posteroinferior aspect of the heart. The left ventricle is the thickest-walled chamber in the heart. The left ventricle receives oxygenated blood from the left atrium. The left ventricle opens to the aorta. The left ventricle contains trabeculae carnae. Blood entering the heart: Into the right atrium: Deoxygenated blood enters the right atrium from the superior and inferior vena cava from systemic circulation and the coronary sinus from coronary circulation. Into Left Atrium: Oxygenated blood enters the left atrium from the left and right pulmonary veins from the pulmonary circulation. Blood exiting the out of the heart: Out of the right ventricle: Deoxygenated blood exits the right ventricle through the pulmonary trunk to pulmonary circulation (to the lungs). Out of the left ventricle: Oxygenated blood exits the left ventricle through the aorta to systemic circulation (to be distributed throughout the body). Atrioventricular (AV) values – heart values: The atrioventricular values are the valves between atria and ventricles. The atrioventricular valves have leaf-like cusps. The cups of the atrioventricular values are attached to papillary muscles by tendons(which are like strings) called chordae tendineae. Between the right atrium and the right ventricle is the tricuspid value- it has three cusps. Between the left atrium and the left ventricle is the bicuspid value- it has two cusps. The bicuspid value is also called the mitral value. When the atrioventricular valve is open, blood flows from atrium to the ventricle. When the atrioventricular value is closed, blood exits the ventricle. Semilunar (SL) valve: The semilunar values (SL) are the valves at the base of large vessels/ exit of ventricles. The semilunar valves are cup-shaped. The Pulmonary SL valve is at the base of the pulmonary trunk. The Aortic SL valve is at the base of the aorta. When cups (of the semilunar valves) are filled, valves close. The valves close to prevent backflow. When the cups (of the semilunar valves) are empty, the valve is open and blood exits the heart. Functions of heart values: The valves prevent backflow of blood The chordae tendineae are strings connecting valve cusps to papillary muscles. The chordae tendineae prevent the atrioventricular valves from bulging into atria. The papillary muscles are pillar-like muscles in the ventricles. The papillary muscles prevent the prolapse of atrioventricular valves. The valves open and close due to changes in blood pressure within the heart chambers. Blood flow in the heart in pulmonary and systemic circulation: The blood flows from the superior and inferior vena cava to the right atrium to the tricuspid valve to the right ventricle to the pulmonary semilunar valves to the pulmonary trunk to the pulmonary arteries to lung tissues (pulmonary circulation) to the pulmonary veins to the left atrium to the bicuspid valve To the left ventricle To the aortic semilunar valves To the aorta To systemic circulation Blood flow in the heart in the coronary circulation. The blood flos from the coronary sinus To the right atrium to the tricuspid valve to the right ventricle to the pulmonary semilunar valves to the pulmonary trunk to the pulmonary arteries to lung tissues (pulmonary circulation) to the pulmonary veins to the left atrium to the bicuspid valve To the left ventricle To the aortic semilunar valves To the aorta To the coronary arteries To the heart tissue (coronary circulation) Pulmonary circulation: Deoxygenated blood is transported to the lungs for oxygenation and then returned to the heart. The deoxygenated blood enters the right atrium and flows into the right ventricle. The deoxygenated blood exits the heart through the pulmonary trunk. The pulmonary trunk divides into left and right pulmonary arteries. The deoxygenated blood travels to the right and left lung where gas exchange occurs. Oxygenated blood travels in the left or right pulmonary veins and enters the left atrium. Systemic circulation: oxygenated blood is transported to body tissues and then returned to the heart. The Oxygenated blood enters the left atrium. The oxygenated blood flows into the left ventricle. The left ventricle contracts and pushes blood out of the heart through the aorta. The aorta branches into the ascending aorta, the aortic arch and the descending aorta. The oxygenated blood is delivered to all cells and tissues in the body for gas/nutrient/fluid exchange. The deoxygenated blood travels back to the heart and re-enters the right atrium through the vena cava. Contraction of the heart produces the pressure Blood moves through the circulatory system from areas of higher to lower pressure The Cardiac cycle: The repetitive contraction (systole) and relaxation (diastole) of heart chambers move the blood through the heart and body. Blood flow is proportional to the metabolic needs of tissues. The brain, kidneys, liver, exercising skeletal muscle have very high needs for blood. Cardiac output is heart rate x stroke volume Nervous control system: The nervous control system maintains blood pressure and thus blood flow. It controls the re-routing of blood flow e.g., an increase in BP with exercise. It controls the re-routing of blood flow away from skin and viscera towards the brain and cardiac muscle in response to blood loss/injury Hormonal Control: Epinephrine (adrenaline) from the adrenal gland – increases HR and SV, Vasoconstriction in response to stress Conducting system: The cardiac conduction system is an internal pacemaker & nerve-like pathway through the myocardium. An action potential is a rapid change in membrane potential. Action potential acts as an electrical signal /impulse. Action potentials spread through the conducting system of the heart to all cardiac muscle cells. This causes the cardiac muscle cells to contract. Blood is ‘pumped’. The heart can generate its own action potentials. Auto-rhythmicity is the repetitive contractions caused by autorhythmic contractile cells. The conducting system process steps: Step one: Action potential originates in the sinoatrial (SA) node (the pacemaker) and travels across the wall of the atrium from the SA node to the atrioventricular (AV) node. Step 2: Action potentials pass through the AV node and along the atrioventricular (AV) bundle which extends from the AV node, through the fibrous skeleton, into the interventricular septum. Step 3: The AV bundle divides into right and left bundle branches, and action potentials descend to the apex of each ventricle along the bundle branches. Step 4: Action potentials are carried by the Purkinje fibres from the bundle branches to the ventricular walls and papillary muscles. Blood composition: Blood is made up of 55% plasma and 45% formed elements. The plasma makes up 55% of the blood: The plasma is made up of 91% water. The plasma also contains 7% proteins. The proteins contained in the plasma are 58% albumin, 38% globulins, 4% fibrinogen. The plasma contains other solutes: ions, nutrients, waste products, gases, and regulatory substances. The formed elements make up 45% of the blood : The formed elements are platelets, white blood cells and red blood cells. Red blood cells make up the majority of the formed elements (4.2-6.2 million). The white blood cells in the formed elements are neutrophils (60-70%), lymphocytes (20-25%), monocytes (3-8%), eosinophils (2-4%) and basophils (0.5-1%). Erythrocytes - Cells in the blood: Erythrocytes are also called Red Blood cells (RBC) Red blood cells are Biconcave disc - shaped Red blood cells are 7.5 µm non-nucleated Red blood cells contain no organelles Red blood cells contain haemoglobin (Hb), a pigmented protein Red blood cells carry oxygen from the lungs to tissues. 1.5% of the oxygen is dissolved in plasma & 98.5% of the oxygen is attached to the haemoglobin protein. Red blood cells carry carbon dioxide from tissues to the lungs. 7% of the carbon dioxide is transported in plasma, 23% is attached to the haemoglobin protein, and 70% is transported as bicarbonate. Leukocytes - Cells in the blood: Leukocytes are also known as White blood cells (WBC) White blood cells are complete cells, nuclei & organelles. There are various types of WBC: e.g. neutrophils, lymphocytes, monocytes, eosinophils, basophils White blood cells mainly help in protection - phagocytosis, immune response ( both cell – mediated and antibody - mediated), white blood cells develop into macrophages, release histamines etc. Blood vessels are the arteries, the veins and the capillaries: Arteries: Arteries take blood away from the heart Arteries contain blood under pressure Arteries are elastic, and muscular, and contain arterioles. Arterioles are very small blood vessels that branch off from arteries and carry blood to the tissues and organs by linking with capillaries. Veins: Veins take blood to the heart The blood in the veins is not under pressure Veins have thinner walls than arteries. Vein walls contain less elastic tissue and less smooth muscle. Veins have venules of various sizes i.e. small, medium, large Capillaries: The capillaries are the site of exchange with tissues (interstitial fluid). The capillaries are the smallest of the three blood vessel types. The capillary wall consists of endothelial cells (simple squamous epithelium), a basement membrane and a delicate layer of loose C.T. There are three types of capillaries: continuous capillaries, fenestrated capillaries and sinusoidal capillaries. Continuous: are the least permeable capillaries type. No gaps between endothelial cells, less permeable to large molecules than other capillary types. Continuous capillaries are found in muscle and nervous tissue. Fenestrated: fenestrated capillaries have pores in endothelial cells called fenestrae. Fenestrated capillaries are highly permeable. Fenestrated capillaries are found in the intestinal villi and glomeruli of the kidney. Sinusoidal. Sinusoidal capillaries have a large diameter, and an irregular incomplete wall of endothelial cells. Sinusoidal capillaries have less basement membrane. Sinusoidal capillaries are found in endocrine glands, and liver (large molecules cross their walls). Blood vessels histology: Tunica intima (interna): is made up of Endothelium, has a basement membrane, lamina propria, Elastic tissue Tunica media: made up of smooth muscle cells and elastin arranged circularly. The smooth muscle changes the diameter of the lumen. The elastic tissue allows distension and recoil. During vasoconstriction, the smooth muscles contract causing a decrease in blood flow. In Vasodilation, the smooth muscles relax causing an increase in blood flow. Tunica externa (adventitia): is made up of connective tissue (CT), transitions from dense connective tissue to loose connective tissue as it merges with surrounding tissue. Capillary exchange: Capillary exchange is the movement of substances into and out of capillaries. The cells are bathed in interstitial fluid (extracellular fluid) Transport (diffusion) in and out of cells requires a pressure gradient (going from high to low) Interstitial fluid needs constant turnover Diffusion: Oxygen, hormones, and nutrients diffuse from a high concentration in the capillary to a low concentration in the interstitial fluid. Lipid soluble substances (O2, CO2, steroid hormones, fatty acids) diffuse through the plasma membrane of endothelial cells. Water soluble (glucose, amino acids) diffuse through intercellular spaces or the fenestrations of capillaries. The spaces between cells are very small and very few molecules can pass e.g. blood-brain barrier (protects the brain from toxins). In large spaces between endothelial cells, proteins and whole cells can pass, for example in the liver or spleen. The Lymphatic System consists of: The lymphatic system is made up of lymphoid organs such as the spleen, thymus, and tonsils, lymphoid tissues and cells such as the lymphocytes B and T cells, Lymph, Lymphatic ducts, trunks, vessels, capillaries and Lymph nodes. Cardiovascular-Lymphatic link: Capillary permeability, blood pressure, and osmotic pressure affect the movement of fluid from capillaries. Fluid moves out of capillaries into interstitial (intercellular) space and most returns to capillaries. The fluid that remains in tissues is picked up by the lymphatic capillaries and then eventually returned to venous circulation. The cardiovascular-lymphatic link maintains blood volume, pressure, and fluid balance Edema: Edema (oedema) is swelling caused by excess fluid accumulation in body tissues (interstitial space). Edema is caused by problems with capillaries, heart failure, kidney disease, liver problems, pregnancy, problems with lymphatic system, standing or walking a lot in hot weather, and eating too much salt. If capillaries become ‘leaky’, proteins can leak into the interstitial fluid. This increases the osmotic pressure (osmolarity) outside the capillary and draws more fluid from the capillaries into the interstitial fluid.