Vessels, Heart Structure And Function, Cardiac Cycle, Heart Disease Flashcards
(47 cards)
Why do large organisms, like mammals, require a circulatory or transport system?
Larger organisms have smaller surface area to volume ratios, so a transport system is needed to supply oxygen and glucose to every metabolically active cell in their large volume.
What does ‘Double Circulatory System’ mean?
It means that the blood passes through the heart twice for each complete circuit of the body, once in the pulmonary circuit to the lungs and once in the systemic circuit to the rest of the body tissues.
Why does the right ventricle not need to generate much pressure?
The pulmonary circuit to the lungs is only a short circuit.
What is the advantage of the low pressure in the pulmonary circuit?
There is more time for gas exchange between the alveoli and the capillaries of the lungs.
Why is the wall of the left ventricle much more muscular?
The blood in the systemic circuit must be under large enough pressure to deliver glucose and oxygen quickly to our organs and tissues as well as take wastes away quickly.
What is the advantage to mammals of having a 4 chambered heart and double circulation?
Oxygenated blood can be delivered quicker and at a greater pressure to all the cells. This allows mammals to be larger and lead active lives with high energy demands.
What is the disadvantage of a single circulatory system, as seen in fish?
As there is only a single circuit, once blood has passed through the gill capillaries, its pressure is reduced which means less pressure behind the blood flow to other body organs.
What is the role of the elastic tissue in the thick walls of arteries?
Elastic tissue allows arteries to 1. Stretch/distend to withstand the high pressure.
And 2. Recoil between heart beats to maintain pressure and push blood along
What is the role of smooth muscle in the thick walls of arteries?
Smooth muscle controls blood flow to organs via vasoconstriction (narrowing of lumen when smooth muscle contracts) and vasodilation (widening of lumen). It helps to maintain blood pressure via vasoconstriction.
What is the role of the inner squamous endothelium layer of both arteries and veins?
It provides a smooth surface for reducing friction to blood flow.
What is the role of the thin outer fibrous layer of arteries and veins?
Protection.
What is the significance of having less smooth muscle and elastic tissue, a larger lumen and the presence of valves in veins when compared to arteries?
The blood is under much lower pressure in veins, therefore less elastic tissue and smooth muscle is needed. The large lumen means that there is little resistance to blood flow. The valves prevent backflow of blood.
What is the only tissue layer that arteries, veins and capillaries have in common?
The squamous endothelium.
What happens in the capillaries?
The exchange of gases, solutes and wastes between the blood and the tissue fluid surrounding cells and tissues.
How are capillaries adapted for exchange?
They have thin permeable walls to reduce diffusion distance, a narrow lumen which reduces diffusion distance and allows RBCs to squeeze through slowly, and huge networks of capillaries that increase surface area for diffusion.
Why does both blood pressure and velocity drop when blood reaches the capillaries?
The arterioles branch into millions of capillaries in huge capillary networks which causes a large increase in surface area.
How is the heart muscle ‘myogenic’?
Myogenic means that it can generate its own electrical impulses to cause contraction.
How is the heart supplied with the oxygen and glucose it needs to maintain its high metabolic rate?
The coronary arteries supply the cardiac muscle with oxygen and glucose.
How are cardiac muscle cells adapted to their function?
They are branched and have bridges to enable conduction of electrical impulses through walls of atria and ventricles.
Why are the atria only thin-walled?
They need less cardiac muscle as they only receive blood (from the body or the lungs).
Why do the ventricles have thicker walls?
They have more cardiac muscle to enable them to generate the pressure needed to pump the blood all around the body (left ventricle) and to the lungs (right ventricle).
What is the job of the atrio-ventricular or AV valves (tricuspid and bicuspid)?
They prevent backflow into the atria when the ventricles contract.
What is the job of the semilunar or pocket valves? (pulmonary and aortic)?
They prevent backflow from the pulmonary artery and the aorta into the ventricles during diastole.
Why do the AV valves have chordae tendinae attaching them onto papillary muscles on the ventricle walls?
The chordae tendinae are tough, flexible structures needed to prevent the AV valves from turning inside out during ventricular contraction.
