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
what mechanisms do cnidarians use to replace a circulatory system
- muscular contractions of body wall pump water in and out of body cavity
circulatory system: annelids (2)
- mechanism
- open or closed
- polychaetes circulate interstitial fluid with cilia or muscular contractions of the body wall
- circulatory system can be open (polychaetes) or closed (oligochaetes)
circulatory system: molluscs (2)
- structures
- open vs closed
- all have hearts and some blood vessels
- most have open systems (clams), while only cephalopods have closed systems (squid)
circulatory system: arthropods - crustaceans (4)
- structures
- open vs closed
- complexity
- control
- all have one or more hearts and some blood vessels
- all have open systems
- circulatory systems become more complex in larger crustaceans
- some control over distribution of blood flow in body
circulatory system: arthropods - insects (3)
- open vs closed
- structures
- gas transport
- relatively simple open circulatory system
- multiple, contractile “hearts” along dorsal vessels
- use tracheal system for most gas transport
phylum chordata (3)
- invertebrate: urochordates (tunicates)
- invertebrate: cephalochordates (lancelets)
- vertebrates (fish, amphibian, reptiles, birds, mammals)
circulatory system: urochordates (2)
- open vs closed
- structures
- open circulatory system
- tubular heart at base of the digestive tract
circulatory system: cephalochordates (2)
- open vs closed
- structures
- closed system with a few open sinuses
- tubular heart at base of the digestive tract and pulsating blood vessels
circulatory system: vertebrates
- open vs closed
- all have closed systems
describe the evolutions of circulatory systems (4)
- first evolved to transport nutrients to body cells
- began to serve a respiratory function very early
- closed systems evolved independently in jawed vertebrates, cephalopods, and annelids
- closed systems evolved in combination with specialized oxygen carrier molecules
why did closed systems evolve/what is its advantage (2)
- increased blood pressure and flow
- increased control of blood distribution
why did closed systems with specialized O2 carrier molecules evolve
- to support high metabolic rates
which organisms have an open circulatory system (4)
- urochordata
- annelida
- arthropoda
- mollusca
which organisms have a closed circulatory system (4)
- vertebrates
- mollusca: cephalopods
- cephalochordata (some open sinuses)
- annelida
how does the circulatory system fit into O2 delivery (4)
- acts in internal convection
- quickly saturates respiratory pigment with O2
- pumps blood to where and when it is needed (changing vessel radius)
- rapidly unloads O2 from blood to mitochondria
when will the body experience increased O2 needs
- during all activities
what are the ways to provide O2 to the body during activity (2)
- heart pumps mor blood per unit time (increased cardiac output)
- tissues extract more O2 from capillaries (O2 content in venous blood will decrease)
