circulation main points Flashcards
what is circulation and which cells does it involve?
gaining O2 and shedding CO2, involves every cell in body
What are two adaptations that allow for effective exchange in animals?
- A body plan that places many or all cells in direct contact with the environment (e.g., flatworms, cnidarians).
- A circulatory system that connects cells to organs involved in gas exchange, nutrient absorption, and waste removal.
What are the three main components of a circulatory system?
- Circulatory fluid (e.g., blood in closed systems, hemolymph in open systems).
- Interconnecting vessels to transport the fluid.
- Muscular pump (heart) to move the fluid through the body.
How does the heart power circulation?
The heart uses metabolic energy to elevate the hydrostatic pressure of the circulatory fluid
How does hydrostatic pressure change as blood moves away from the heart?
Hydrostatic pressure is highest when blood leaves the heart and decreases as it moves further from the heart.
what does hemolymph do in open circulatory systems besides acting as blood?
doubles as interstitial fluid that bathes body cells
How does circulation occur in an open circulatory system?
heart pumps hemolymph into sinuses, where it bathes organs directly. The heart then relaxes, drawing the hemolymph back in, aided by body movements
What allows efficient exchange in closed circulatory systems?
Capillaries are numerous and close to all cells, allowing for easy diffusion of materials b/w blood and interstitial fluid.
What is the function of arteries?
Arteries carry blood away from the heart and must withstand high hydrostatic pressure.
How do arteries branch within organs?
Arteries → Arterioles → Capillaries.
What is the function of veins?
Veins return blood to the heart by collecting fluid from capillaries through venules.
What are capillaries, and why are they important?
Capillaries are thin-walled vessels where exchange between blood and interstitial fluid occurs
How do portal veins differ from other veins?
Portal veins carry blood between two capillary beds (e.g., hepatic portal vein from the small intestine to the liver).
What are the two main types of heart chambers?
Atria: Receive blood.
Ventricles: Pump blood.
How many chambers do bony fish, rays, and sharks have?
Two chambers (one atrium, one ventricle).
How does circulation work in fish?
They have a single circulatory circuit: blood passes through the heart once per cycle, moving through two capillary beds (gills → body) before returning to the heart.
What happens to blood pressure in a single circulatory system?
Blood pressure drops significantly after passing through the first set of capillaries (gills) and again at the body capillaries.
