chapter 23 circulation

Question 1

what are the two main veins that return blood to the human heart from the body

Answer 1

*superior vena cava & inferior vena cava *

Question 2

what is the main artery that carries blood from the human heart to the body

Answer 2

aorta

Question 3

trace the pathway of blood through the human heart

Answer 3

Having a closed circulatory system and blood vessels with valves preventing backflow ensures that blood flows only in one direction and in a definite channel. Starting with return of blood to the heart from the body – vena cavae – right atrium – right atrioventricular (AV) valve – right ventricle – pulmonary semi-lunar (SL) valve – pulmonary arteries – lungs – pulmonary veins – left atrium – left atrioventricular (AV) valve – left ventricle – aortic semilunar (SL) valve – aorta – branch arteries – arterioles – capillaries in the various body systems – venules – veins – vena cavae.

Question 4

what is the pacemaker of the human heart

Answer 4

the sinoatrial (SA) node which is a small mass of specialized muscle fibers in the upper right atrial wall contracts and initiates an electrical impulse that spreads across the walls of the atria causing them to contract

Question 5

what is generally considered to be a normal pulse rate for human adults at rest

Answer 5

normal blood pressure falls within a range of values, but optimal pressure for adults is below 120 systolic and below 80 diastolic

Question 6

what do the two numbers in a blood pressure reading mean (how do they relate to the heart cycle)

Answer 6

**systolic pressure–» the systole is the phase of the heartbeat cycle when the ventricles are contracting, thus blood pressure in the arteries is greatest at this point

**diastolic pressure–» the diastole is the phase of the heartbeat cycle when the ventricles are relaxing, thus blood pressure in the arteries is lowest at this point

Question 7

what is the function of red blood cells, white blood cells & platelets

Answer 7

red blood cells –» to carry oxygen

white blood cells –» protection against diseases, some engulf and digest invading microorganisms and some produce antibodies to fight infection

platelets–» function in blood clotting