Cardiovascular System PDF

• • Cardiovascular system is made up of a series of organs which is made up of connective tissues and cells (epithelial and muscle) o Epithelia form barriers between blood and the walls of the vascular system to prevent coagulating and clotting of blood inside blood vessels. o Muscle consists of c...

• • Cardiovascular system is made up of a series of organs which is made up of connective tissues and cells (epithelial and muscle) o Epithelia form barriers between blood and the walls of the vascular system to prevent coagulating and clotting of blood inside blood vessels. o Muscle consists of cardiac muscles (only in heart) and smooth muscles (in the blood vessel walls) Organs consists of the... o Heart - pump o Supply - arteries o Veins/lymphatics - drainage o Capillaries - exchange with tissues (+ nutrients, - waste) END GOAL of CVS CVS Anatomy - 2 systems, 1 function 1. Blood vascular system - closed supply and drainage system containing blood (a continuous loop that starts and returns to the heart) 2. Lymphatic (vascular) system - open-entry drainage system containing lymph (a one-way system that later reunites with the blood vascular system) o porous set of capillaries that surrounds blood capillaries and drains excess fluid that has escaped the blood vascular system, prevents blood capillaries from swelling up Blood and lymph vascular systems - 2 circuits • Pulmonary and systemic circuit work in SERIES not parallel. o Pulmonary circuit: right heart ---> oxygenated at gas exchange surfaces in lungs ---> left heart o Systemic circuit: left heart ---> deoxygenated at gas exchange surfaces of exchange capillaries of rest of body ---> right heart (A) Supply Side = Arteries • Transport blood away from the heart and contain high velocity and pressurised blood • Major arteries are situated according to their function to avoid damage (very dangerous, can lose large volume of blood in short time) o E.g. Deep in the trunks and on flexor aspects of limb (protecting harm with extensor sides by putting arm up, extensor aspects contain no arteries) • Important structures often receive supply from two sources (two separate arteries) o E.g. Hand has 2 supplies (radial and ulnar), brain has 4 supplies (2 up vertebrae and 2 up neck) • Arteries change their name at each major branch (B) Exchange network = capillaries (L7) • Capillaries present with varying degrees of permeability (leakiness) for exchange of nutrients, dissolved gases and wastes between blood and surrounding interstitial fluid achieved by changing the epithelial (endothelial) lining of capillaries. o Continuous (controlled - tight) o Fenestrated (leaky) o Sinusoidal (very leaky) (C) Drainage - 3 pathways • Transport blood towards the heart and contain low velocity and low pressure blood o Deep veins (adjacent and in close proximity to supply arteries, deep in position) o Superficial veins (large veins can be located in vulnerable locations as lower risk of bleeding out) o Lymphatics (porous set of capillaries that surrounds blood capillaries and drains excess fluid that has escaped the blood vascular system, prevents blood capillaries from swelling up) Arteries and veins have different physiological structures due to the difference in pressure of blood. • Pressure decreases significantly after capillary exchange and blood has low pressure and moves slowly and is not re-established before returning to the heart. • Arteries and veins shift the same volume of blood per second • To compensate for the difference in pressure, cross-sectional area of veins is at least twice as wide of arteries to shift the same volume of blood per second Orientation of the heart in the thoracic cavity • Located in the thorax (chest), flanked laterally by the left and right pleural cavities (lung), anterior portion of mediastinum (med-region between pleural cavities) • Rotated to the left and base tilted posteriorly/apex pushes against the anterior chest wall creating the apex beat at the point of maximal impulse or intensity (PMI) o 2/3 of heart located in L side of thoracic cavity and 1/3 of heart located in R side of thoracic cavity • Venous return to the atria of the heart: atrium - thin-walled (not very muscular) receiving chambers o Right atrium receives deO2 blood from superior vena cava, inferior vena cava, coronary sinus o Left atrium receives O2 blood from 4 pulmonary arteries Layers of the heart wall (both in atrium and ventricle) • Endocardium - innermost layer • Myocardium - cardiac muscle that generates force to pump blood (ventricle has thicker layer of myocardium than atria) • Epicardium - superficial layer Pericardium – outermost layer of thick epithelial (endothelial) tissue, lubricating sac for heart to sit in when beating, protection from abrasion and injury Endocardium - innermost layer • Simple squamous epithelium (endothelium) - delicate, lines the inner surface of the heart including heart valves and larger vessels (forms a barrier between blood and vascular wall of CVS) • Loose irregular fibrous connective tissue (FCT) - supports endothelial cells • Small blood vessels • Purkinje fibres - modified cardiac muscle tissue carrying electrical conduction for the rhythmic electrical conduction of the heart. Myocardial thickness (left vs right ventricles) • Atrium: functional demands of R/L atria similar; two chambers look almost identical • Ventricle: functional demands of R/L ventricles are very different; two chambers have significant structural differences • • • Both ventricles pump the same volume of blood per second but at different pressure (blood from left ventricle has higher pressure than right) To compensate for the difference in pressure, left and right ventricle have different composition of myocardium - ratio of 3:1 Structural differences due to differing functional demands of R/L ventricles o Right ventricle: does not need to generate large force to push blood through pulmonary circuit as lungs as close to the heart AND pulmonary vessels are relatively short and wide o Left ventricle: thick muscular walls to push blood around the systemic circuit than pulmonary circuit (right) Pericardium • Closed serous membrane • Pericardial cavity contains pericardial fluid (lubricant) secreted by the pericardial serous membrane which allows frictionless movement of the heart Fibrous pericardium - outermost layer of pericardium layer (high collagen content, thin but very strong, "tough leathery bag")