The heart receives a large volume of blood from the vena cavae when the atria relax. What prevents it from over-expanding when receiving all this returning blood? A serous layer at the outside of the heart muscle A strong fibrous layer beneath the endothelium A fibrous bag closely enclosing the whole heart but separate from it The concentric organisation of specially modified muscle fibres around and within the myocardium Strong collagenous connective tissues within the muscle layers

Great Vessels of the Heart The great vessels of the heart include the aorta and pulmonary trunk that carry blood away from the heart and the inferior vena cava, superior vena cava and pulmonary veins that carry blood to the heart. • superior vena cava: drains blood from the ______________________________________ (regions of body) to empty into the superior region of the __________________________; contains no valves; • inferior vena cava: drains blood from the __________________________________________ (regions of body) to empty into the inferior region of the __________________________; contains single valve at its terminal end called the Eustachian valve; • pulmonary veins: 4 in number (right and left pairs); carry blood from the right and left lungs to drain into the ___________________________ to complete the pulmonary circuit; coloured red in models since they carry oxygenated blood (the only veins to do so); do not contain valves; • pulmonary trunk: also referred to as the main pulmonary artery; terminally divides into the right and left pulmonary arteries; carries deoxygenated blood from the _____________________________ to the lungs; coloured blue in models since it carries deoxygenated blood (the only arteries to do so); origin of pulmonary blood circuit; • aorta: carries blood from the _____________________________ of the heart to most parts of the body; origin of systemic blood circuit. answers only

The heart is a muscular organ comprising four chambers, two atria and two ventricles, that function synergistically to pump blood through a vast closed network of blood vessels.  The chambers are separated by membranous muscular barriers known as septa.  Oxygenated blood returning from the lungs via the pulmonary veins fills the left atrium and enters the left ventricle, which then pumps the blood into the systemic arteries to supply other organs in the body.  Deoxygenated blood returning from systemic veins first enters the right atrium, then the right ventricle, and is ultimately siphoned into the pulmonary arteries leading to the lungs.  The necessary exchange of oxygen, nutrients, and waste occurs between the thinnest blood vessels (capillaries) and neighboring tissues of the systemic and pulmonary circuits.Blood flow throughout the circulatory system is dictated by blood (hydrostatic) pressure, vascular resistance (force opposing blood flow through a vessel), and cardiac output (blood volume expelled from the ventricles per unit time).  When blood traverses a vessel, it exerts hydrostatic pressure on the vessel walls, which results in the forced movement of fluid out of vessels and into the interstitial space.  The circulating plasma proteins cause the osmotic pressure within the vessel to be higher than that of the interstitial fluid.  In turn, osmotic pressure causes fluid to flow from the interstitial space into blood vessels, opposing hydrostatic pressure.Cardiac output depends in part on heart rate, which is tightly regulated by the sinoatrial (SA) and atrioventricular (AV) nodes, specialized groups of self-depolarizing cells located in the upper right atrium wall and lower interatrial septum, respectively.  Action potentials (APs) generated by SA nodal cells stimulate atrial contraction as they travel to the AV node.  The AV node delays AP transmission to ventricular cells, ensuring ventricular filling is complete prior to heart contraction.A 63-year-old man was admitted to the hospital after he collapsed while exercising.  The patient had an elevated heart rate and an abnormally low blood oxygen level on admission.  X-rays revealed excess fluid in his lungs. Question 20Based on the information in the passage, the excess fluid in the patient's lungs is most likely caused by which of the following at pulmonary sites of gas exchange?A.Increased protein concentration in the blood flowing through pulmonary capillariesB.Decreased solute concentration in the interstitial fluid surrounding the pulmonary capillariesC.Increased hydrostatic pressure within pulmonary capillariesD.Decreased volume of blood flowing through the pulmonary capillariesSubmit

At 2mm Hg in the inferior vena cava, what factors do youthink propel blood into the right heart from the lower partsof the body?

What does the fibrous pericardium do? holds the heart in place so it doesn't bounce aroundpumps the bloodexchanges gases

13 Assertion : Atria receive blood from all parts of the body which subsequently flows to ventricles.Reason : Action potential generated at sino-atrial node passes from atria to ventricles