UNIT 3: The Human Circulatory System Flashcards
open circulatory system
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.
closed circulatory system
blood flows around the body enclosed in blood vessels and does not leave the blood vessels e.g. humans
the human circulatory system consists of
- blood vessels
- heart
- blood
arteries
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.
veins
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.
capillaries
blood vessels with walls one cell thick that carries blood from arterioles to venules through tissues, releasing nutrients and taking away wastes.
systemic and pulmonary circuits
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.
portal system
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.
aorta
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)
pulmonary artery
carries de-oxygenated blood away from the right side of the heart to the lungs to excrete carbon dioxide and absorb more oxygen.
pulmonary vein
carries oxygenated blood towards the right side of the heart from the lungs
left atrium
upper left chamber of the heart that receives blood from the lungs and contracts pumping blood into the left ventricle.
bicuspid valve
allows one-way flow of blood from left atrium into the left ventricle - prevents backflow of blood
chordae tendineae
connective tissue holding the heart valves in position
left ventricle
strongest of the four heart chambers and pumps blood into the aorta
septum
divides the heart into two separate pumps
right ventricle
pumps deoxygenated blood to the lungs via the pulmonary artery
papillary muscle
contracts preventing the heart valves prolapsing backwards
inferior vena cava
carried deoxygenated blood from the lower half of the body back to the heart
tricuspid valve
allows one-way flow of blood from the right atrium to the right ventricle -preventing backflow of blood
right atrium
upper right chamber of the heart that receives blood from the vena cavae and contracts pumping blood into the right ventricle
superior vena cava
carries deoxygenated blood from the upper half of the body back to the heart
semilunar valves
allow one-way flow of blood out of the heart - prevent backflow of blood into the heart
the cardiac cycle
controlled by the pacemaker - which is located in the top of the right atrium. the pacemaker is a type of nervous tissue
atrial contraction
- pacemaker sends an electrical signal to the cardiac muscle of the atria.
- the atria contract.
- blood moves into the ventricles through the heart valves.
ventricular contraction
- 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.
SA node
sino-atrial - located in the top wall of the atrium
AV node
atrio-ventricular node - located between the right atrium and ventricle
atrial systole and ventricular diastole
- 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).
ventricular systole and atrial diastole
- 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
pulse
expansion of an artery as blood passes through.
blood pressure
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.
effects of smoking on the circulatory system
- 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
effects of diet on the circulatory system
- 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.
effects of exercise on the circulatory system
- exercise stimulates a temporary increase in heart rate and blood pressure.
- it strengthens the heart and promotes healthy blood vessels.
Diastole
When the heart chambers relax
Systole
When the heart chambers contract
