- Blood circulates through arteries, veins, and capillaries in a closed system.
- Tissue fluid fills the spaces between cells and facilitates exchange between blood and cells.
- Lymph is transported through lymph vessels and supports immune function.
- Arteries carry oxygenated blood (bright red), while veins carry deoxygenated blood (dark red), although veins may appear blue from the outside.
- Non-circulating fluids, like synovial fluid and vitreous humour, are confined to specific organs and do not move through a circulatory system.
Definitions [5]
Definition: Closed Blood Circulatory System
A closed blood circulatory system is one in which blood flows entirely within blood vessels, as seen in humans and other vertebrates.
Definition: Open Blood Circulatory System
An open blood circulatory system is found in animals like insects, where blood flows freely through body cavities without confined blood vessels.
Define a cardiac output.
- Cardiac output is the volume of blood that the heart pumps out in a minute. It is computed by multiplying heart rate (the number of beats per minute) by stroke volume, which is the amount of blood pumped by each ventricle per minute.
- A healthy person's heart beats 72 times per minute, pumping out roughly 70 millilitres of blood with each beat. As a result, the average cardiac output is five litres, or 5000 mL.
Define a cardiac cycle.
- The heart's cyclical repetition of successive events, known as the cardiac cycle, is made up of the contraction and relaxation of the ventricles and atria during diastole.
- A cardiac cycle lasts about 0.8 seconds. The trial systole (0.1 second), ventricular systole (0.3 second), and full cardiac diastole (0.4 second) are the phases of the heart cycle.
Define portal vein.
A portal vein is one that starts with capillaries and also ends in capillaries.
Key Points
Key Points: Fluids in Our Body
