UNIT 3: The Human Circulatory System

Question 1

open circulatory system

Answer 1

blood is pumped from a simple heart and flows out of blood vessels and around tissue cells of the organism e.g. invertebrates, such as insects.
the blood is then returned to the heart via small pores called ostia.

Question 2

closed circulatory system

Answer 2

blood flows around the body enclosed in blood vessels and does not leave the blood vessels e.g. humans

Question 3

the human circulatory system consists of

Answer 3

• blood vessels
• heart
• blood

Question 4

arteries

Answer 4

blood vessels that carry blood away from the heart in pulses. it has a thick wall and a small lumen.
the thick wall of arteries contains a tough layer of collagen that gives strength to the artery that supports the pressure the blood is under from the heart.
it also contains a layer of smooth (involuntary) muscle that contracts pushing blood along. the internal layer of the artery is composed of a layer of cells called endothelium.

Question 5

veins

Answer 5

blood vessels that carry blood towards the heart in an even flow. they have thin walls, a large lumen and valves.
blood pressure in veins is much lower than arteries, hence the thinner wall.
they also have a smooth muscle to push blood along in one direction and have valves to prevent backflow of blood.

Question 6

capillaries

Answer 6

blood vessels with walls one cell thick that carries blood from arterioles to venules through tissues, releasing nutrients and taking away wastes.

Question 7

systemic and pulmonary circuits

Answer 7

2 blood circuits -> double circulatory system.
the systemic circuit carries blood to all the major organs of the body, except the lungs.
the lungs have their own blood circuit, called the pulmonary circuit.

Question 8

portal system

Answer 8

a network of blood capillaries that connect two organs or tissues, e.g. hepatic portal system connects the small intestines to the liver via the hepatic portal vein.

Question 9

aorta

Answer 9

largest artery in the body carrying oxygenated blood away from the left side of the heart to all the major organs of the body (except the lungs)

Question 10

pulmonary artery

Answer 10

carries de-oxygenated blood away from the right side of the heart to the lungs to excrete carbon dioxide and absorb more oxygen.

Question 11

pulmonary vein

Answer 11

carries oxygenated blood towards the right side of the heart from the lungs

Question 12

left atrium

Answer 12

upper left chamber of the heart that receives blood from the lungs and contracts pumping blood into the left ventricle.

Question 13

bicuspid valve

Answer 13

allows one-way flow of blood from left atrium into the left ventricle - prevents backflow of blood

Question 14

chordae tendineae

Answer 14

connective tissue holding the heart valves in position

Question 15

left ventricle

Answer 15

strongest of the four heart chambers and pumps blood into the aorta

Question 16

septum

Answer 16

divides the heart into two separate pumps

Question 17

right ventricle

Answer 17

pumps deoxygenated blood to the lungs via the pulmonary artery

Question 18

papillary muscle

Answer 18

contracts preventing the heart valves prolapsing backwards

Question 19

inferior vena cava

Answer 19

carried deoxygenated blood from the lower half of the body back to the heart

Question 20

tricuspid valve

Answer 20

allows one-way flow of blood from the right atrium to the right ventricle -preventing backflow of blood

Question 21

right atrium

Answer 21

upper right chamber of the heart that receives blood from the vena cavae and contracts pumping blood into the right ventricle

Question 22

superior vena cava

Answer 22

carries deoxygenated blood from the upper half of the body back to the heart

Question 23

semilunar valves

Answer 23

allow one-way flow of blood out of the heart - prevent backflow of blood into the heart

Question 24

the cardiac cycle

Answer 24

controlled by the pacemaker - which is located in the top of the right atrium. the pacemaker is a type of nervous tissue

Question 25

atrial contraction

Answer 25

• pacemaker sends an electrical signal to the cardiac muscle of the atria.
• the atria contract.
• blood moves into the ventricles through the heart valves.

Question 26

ventricular contraction

Answer 26

• the electrical signal that came from the pacemaker then travels onto the cardiac muscle of the ventricles.
• the ventricles contract.
• blood is pushed out of the heart via the semilunar valves.

Question 27

SA node

Answer 27

sino-atrial - located in the top wall of the atrium

Question 28

AV node

Answer 28

atrio-ventricular node - located between the right atrium and ventricle

Question 29

atrial systole and ventricular diastole

Answer 29

• atria receive blood from the major veins (vena cavae and pulmonary veins).
• the SA node sends an electrical signal to the cardiac muscle of the atria.
• the atria contract (systole).
• the bicuspid and tricuspid valves open.
• blood flows into the ventricles, which are not contracting (diastole).

Question 30

ventricular systole and atrial diastole

Answer 30

• electrical signal reaches the AV node, which relays the signal onto the cardiac muscle of the ventricles.
• the ventricles contract (systole).
• the bicuspid and tricuspid valves close and the semilunar valves open.
• blood flows out of the heart via the aorta and pulmonary artery

Question 31

pulse

Answer 31

expansion of an artery as blood passes through.

Question 32

blood pressure

Answer 32

force blood exerts on the walls of the blood vessels.
measures as two values, systolic pressure and diastolic pressure.
normal blood pressure is 120/80 mmHg - millimeters of mercury.
measured using a sphygmomanometre.

Question 33

effects of smoking on the circulatory system

Answer 33

• cigarettes contain many addictive chemicals, of which the most important is nicotine.
• nicotine raises heart rate and blood pressure putting a strain on the circulatory system

Question 34

effects of diet on the circulatory system

Answer 34

• a diet high in saturated fats increases blood pressure and the risk of atherosclerosis (hardening of the arteries).
• salt in the diet also raises blood pressure by increasing thirst and water intake.

Question 35

effects of exercise on the circulatory system

Answer 35

• exercise stimulates a temporary increase in heart rate and blood pressure.
• it strengthens the heart and promotes healthy blood vessels.

Question 36

Diastole

Answer 36

When the heart chambers relax

Question 37

Systole

Answer 37

When the heart chambers contract