Question

26) arteries in the head and the neck must contain valves because blood is flowing away from gravitational pull

27) a disease state characterized by overproduction of nonfunctional white blood cells to the extent that the cells /bone marrow function is imapired is:

28) which of the following is not a mechanism used to return venous blood to the heart?

29) which of the following pacemaker cell population has the fastest intrinsic rate of depolarization at about 60 or more times per minute

30) what is the function of the valves in the heart

Answer 1

26) Arteries in the head and the neck must contain valves because blood is flowing away from gravitational pull. Usually arteries are not provided with valves except aorta and pulmonary artery because the pressure inside the arteries is much more which prevents backflow of blood to heart. But carotid artery which supplying blood to head and neck are having baroreceptors and maintain the pressure of blood

27) Chronic myelogenous leukemia (CML) a condition where the bone marrow cells are mutated and results in the unregulated and increased overproduction of white blood cells occurs and their accumulation in blood resulting in immunodeficiency and other symptoms.

28) Venous return is the return of blood from venous system to the right atrium of heart. Return of venous blood to heart is governed by Skeletal muscle pump--Rhythmical contraction of limb muscles occurring during normal locomotory activity which promotes venous return, Respiratory pump--During respiratory inspiration, the venous return transiently increases because of a decrease in right atrial pressure. The opposite occurs during expiration. Valves present in veins helps in preventing the back flow of blood from heart against gravity and pressure gradient.

29) SA node which is the regulator of action potentials and is the major pacemaker of heart which is located in the right atrium. SA node having the intrinsic rate of depolarizations of 60-100 beats per minute followed by atrial foci having 60-80 bpm, AV node and bundle of his (junctional foci) having 40-60 bpm and Ventricles 20-40 bpm

30) valves of heart functions to prevent the backflow of blood. Valves present in heart are mitral valve, tricuspid valve which ensures the one way flow of blood from atria to ventricles and prevents the backflow of blood during contractions of heart chambers and atrial valve and pulmonary valve prevents the flow of blood back to heart from aorta and pulmonary artery respectively.