Circulation 1 Flashcards
what organisms lack circulatory systems (2)
- unicellular organisms
- small metazoans
what do organisms without a circulatory system rely on to transport molecules
- diffusion, which can be rapid over small distances
how to large animals deal with limits to diffusion (2)
- circulation
- they move fluid through their bodies by bulk flow or convective transport
which organisms have a circulatory system
- most metazoans larger than a few cells
what are the major functions of circulatory systems (6)
transport:
- oxygen
- carbon dioxide
- nutrients
- waste products
- immune cells
- signalling molecules
how do circulatory systems move fluids
- by increasing pressure of the fluid in one part of the body
describe the flow of fluid through the body in terms of pressure
- flows “down” the pressure gradient
what are the three main components needed for a circulatory system (3)
- pump or propulsive structures to create high pressure
- system of tubes, channels, or spaces
- fluid that circulates through the system
types of pumps (3)
- chambered hearts
- skeletal muscle
- pulsating blood vessels
pumps: chambered hearts (2)
- contractile chambers
- blood enters atrium, and is pumped out by ventricles
pumps: skeletal muscle
- squeeze on vessels to generate pressure
pumps: pulsating blood vessels
- peristalsis; rhythmic contractions of vessel wall pumps blood
how does the circulatory system prevent back flow
- one-way valves help to ensure unidirectional flow
types of fluid (4)
- blood
- hemolymph
- interstitial fluid
- lymph
fluids: blood
- fluid that circulates within the vessels of a closed circulatory system
fluids: hemolymph
- fluid that circulates in an open circulatory system
fluids: interstitial fluid (2)
- extracellular fluid that directly bathes the tissues and exists between cells
- similar composition to plasma
fluids: lymph (2)
- fluid that circulates in the lymphatic system
- fluid that has filtered out of the vessels
lymphatic system (2)
- secondary circulatory system of vertebrates
- carries lymph that has filtered out of the vessels
open circulatory system (3)
- circulatory fluid comes in direct contact with the tissues in sinuses (open spaces)
- circulatory fluid mixes with interstitial fluid
- no control on how fluid returns to the hearts
closed circulatory system (3)
- circulating fluid remains within vessels and does not come in direct contact with the tissues
- circulating fluid is distinct from interstitial fluid
- molecules must diffuse across vessel wall
multicellular animals that lack circulatory systems (3)
- sponges
- cnidarians
- flatworms
why do sponges, cnidarians and flatworms lack circulatory system
- they have mechanisms for propelling fluids around their body
what mechanisms do sponges and flatworms have to makeup for their lack in circulatory system
- ciliated cells move water within body cavity