30 Questions
What is the term used to describe the portion of the heartbeat during which ejection takes place?
Systole
What valves remain open during atrial systole?
AV valves
What is the duration of atrial systole?
0.1 s
What occurs during ventricular diastole?
Ventricles undergo refilling
How long does ventricular systole last?
0.3 s
What is the term used to describe the portion of the heartbeat during which chamber refilling takes place?
Diastole
What is the thickness of the walls of capillaries?
One cell layer thick
What is the estimated surface area of all the capillaries in the entire system?
500 m2
What is the average length of a capillary in the peripheral circulation?
1 mm
What surrounds the endothelial cells in arterioles?
A single or double layer of smooth muscle cells
What is the function of precapillary sphincters?
To regulate vascular resistance
What determines the operation of arteriolar smooth muscle cells?
The concentration of oxygen or carbon dioxide
What happens to the atria during ventricular systole?
They undergo diastole
During which phase of the cardiac cycle are both the AV valves and the aortic and pulmonic valves open?
None of the above
What is the purpose of the semilunar valves?
To prevent blood from flowing backward into the ventricles
When do the aortic and pulmonic valves close?
When the pressure in the ventricle drops below the pressure in the aorta or pulmonary artery
What happens when the pressure in the left ventricle rises above the pressure in the aorta?
The aortic valve opens
What is the duration of the period shown in the figure?
0.4 s
What allows the passage of water, inorganic ions, glucose, and amino acids through the capillary wall?
Pores
What is the main function of the venous system?
To act as a huge blood reservoir
What is the result of changing venule diameter in a 70-kg person?
A change in blood volume by 1.5 L
What type of molecules are excluded from passage through the pores in the capillary wall?
Serum albumin and globular proteins
What is the characteristic of tight junctions in venules compared to capillaries?
They are more frequent and have bigger pores
What is the main site of diffusion in the microcirculation?
Venules
What do lymphatic vessels primarily transport?
Fluid, serum proteins, lipids, and foreign substances
What is the mechanism by which fluid enters the lymphatic vessels?
Passive movement due to pressure gradient
What is the function of lymph valves in lymphatic vessels?
Prevent backflow and ensure unidirectional flow
What is the daily rate of fluid collection by the lymphatic vasculature?
3 L/day
What is the significance of the lymphatic system in plasma protein circulation?
It returns plasma proteins to the blood
What is the term for the fluid that enters a lymph capillary?
Lymph
Learn about the cardiac cycle, including ventricular systole, atrial diastole, and blood pressure changes in the aorta, left ventricle, and left atrium. Understand the heart's functioning and the pressure changes during different stages.
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