Circulatory System Notes
Circulatory Systems link exchange surfaces with cells throughout the body
Diffusion is too slow of an exchange system for large organisms
Gastrovascular Cavities
Fluid bathes both the inner and outer layers
This facilitates exchange between both layers easily, as a sort of bridge
Evolutionary Variation of Circulatory System
Diffusion distance was too great of a problem
Three components:
Fluid
Interconnecting vessels
Heart
Open and Closed Circulatory Systems
Arthropods and most molluscs have an open circulatory system
Organization of Vertebrate Circulatory System
The closed circulatory system of humans and other vertebrates is often called the cardiovascular system.
Total length of blood vessels is twice the circumference of the equator
Arteries carry blood away, they branch into arterioles
Arterioles are small vessels that convey blood to the capillaries.
Capillaries are microscopic vessels with very thin, porous walls.
Networks of capillaries are called capillary beds
Sites of diffusion
They converge into venules at the downstream end, and venules converge into veins
Portal veins are the only veins that carry blood between capillary beds
Heart:
Atria - chambers that receive blood
Ventricles - pump blood out
Single Circulation
Bony fishes, rays, sharks
Heart consists of two chambers: one atrium and one ventricle
The blood passes through the heart once in each complete circuit
Ventricle contraction pumps blood to the gills
Blood that leaves the heart in single circulation passes through two capillary beds before returning
Double Circulation
Amphibians, reptiles, mammals
One pump from the right side delivers oxygen-poor blood to the capillary beds of the gas exchange tissus
This is part of the pulmonary circuit if the capillaries are in the lungs
This is part of the pulmocutaneous circuit if it includes capillaries in both the lungs and skin (amphibians)
The blood then enters the left pump, which propels the blood to capillary
Diffusion is too slow of an exchange system for large organisms
Gastrovascular Cavities
Fluid bathes both the inner and outer layers
This facilitates exchange between both layers easily, as a sort of bridge
Evolutionary Variation of Circulatory System
Diffusion distance was too great of a problem
Three components:
Fluid
Interconnecting vessels
Heart
Open and Closed Circulatory Systems
Arthropods and most molluscs have an open circulatory system
Organization of Vertebrate Circulatory System
The closed circulatory system of humans and other vertebrates is often called the cardiovascular system.
Total length of blood vessels is twice the circumference of the equator
Arteries carry blood away, they branch into arterioles
Arterioles are small vessels that convey blood to the capillaries.
Capillaries are microscopic vessels with very thin, porous walls.
Networks of capillaries are called capillary beds
Sites of diffusion
They converge into venules at the downstream end, and venules converge into veins
Portal veins are the only veins that carry blood between capillary beds
Heart:
Atria - chambers that receive blood
Ventricles - pump blood out
Single Circulation
Bony fishes, rays, sharks
Heart consists of two chambers: one atrium and one ventricle
The blood passes through the heart once in each complete circuit
Ventricle contraction pumps blood to the gills
Blood that leaves the heart in single circulation passes through two capillary beds before returning
Double Circulation
Amphibians, reptiles, mammals
One pump from the right side delivers oxygen-poor blood to the capillary beds of the gas exchange tissus
This is part of the pulmonary circuit if the capillaries are in the lungs
This is part of the pulmocutaneous circuit if it includes capillaries in both the lungs and skin (amphibians)
The blood then enters the left pump, which propels the blood to capillary