Transcript Circulatory - Local.brookings.k12.sd.us

Circulatory
System
Function and Structure of the Circulatory System
•Transport of gases, nutrients, wastes, and hormones.
•Highway system for leukocytes
•Helps maintain homeostasis by transporting warm blood to
extremities
•Helps stabilize pH and ionic concentrations of body fluids
Blood vessels
•The three types of blood vessels are arteries, veins, and capillaries.
•Blood vessels consist of a layered wall surrounding a central bloodfilled space, called the lumen.
•Arteries carry blood away from heart.
•Arteries have a thick, elastic muscle layer to absorb peaks in pressure
•The smallest blood vessels are capillaries. The diameter is so
small that red blood cells travel single file.
•Not all of the capillary beds are open at one time
•
•Blood pressure is highest in the arteries but is considerably reduced as it flows through the capillaries. It is
lowest in the veins.
•The exchange of substances between blood and the body cells occurs in the capillaries.
•Although fluid leaves and returns to the capillaries, blood cells and large proteins remain in the capillaries.
•The diameter of veins is greater than that of arteries.
•The blood pressure in the veins is low so valves in veins help prevent backflow.
•The contraction of skeletal muscle during normal body movements squeezes the veins and assists with moving
blood back to the heart.
•Veins act as blood reservoirs because they contain 50% to 60% of the blood volume.
Flow of blood within the heart
Blood leaves the body tissues via
various veins and enters the right
atrium of the heart via the vena
cava. Through the tricuspid
valve to the right ventricle where
it is pumped through a semi lunar
valve into the pulmonary artery
where it is passed to the lungs to
be oxygenated.Blood enters the
left atrium via the Pulmonary
vein from the lungs. Flows
through the mitral valve to the left
ventricle. Pumped out of the left
ventricle through a semi lunar
valve into the aorta. Branches
through series of arteries to all
parts of the body. Then the whole
process starts again!!!
Composition of Blood
•A cell that contains hemoglobin and can carry oxygen to the body. Also called a
red blood cell (RBC).
•The reddish color is due to the hemoglobin.
•concave in shape, which increases the cell's surface area
Open versus Closed Circulatory System
In a closed circulatory system, blood is not free
in a cavity; it is contained within blood vessels.
Valves prevent the backflow of blood within the
blood vessels.
This type of circulatory system is found in
vertebrates and several invertebrates
including annelids, squids and octopuses.
In an open circulatory system, blood is pumped from
the heart through blood vessels but then it leaves the
blood vessels
Blood flows slowly in an open circulatory system.
The animal must move its muscles to move the
blood within the spaces.
Arthropods and most mollusks (except cephalopods:
nautilus, squid, octopus) have an open circulatory
system
Fish have closed circulatory systems
Amphibians have a three chambered heart: two atria and a single ventricle. Deoxygenated
blood and oxygenated blood mix; maximum efficiency is not needed to supply the body’s
needs.
Lizards have a muscular septum which partially divides the ventricle.
When the ventricle contracts, the opening in the septum closes and the ventricle is
momentarily divided into two separate chambers.
This prevents mixing of the two bloods.
Four Chambers: Birds, Crocodiles, and Mammals
The septum is complete in the hearts of birds, crocodiles, and mammals providing two
separate circulatory systems:
Raynaud’s phenomenon is a condition in which cold temperatures or strong emotions cause blood vessel
spasms that block blood flow to the fingers, toes, ears, and nose. Raynaud's phenomenon also occurs without
another disease, medication, or cause. This is called primary Raynaud's phenomenon. It most often begins in
people younger than age 30. Strong emotions or exposure to the cold causes the fingers, toes, ears, or nose to
become white, then turn blue. When blood flow returns, the area becomes red and then later returns to normal
color. The attacks may last from minutes to hours.
People with primary Raynaud's phenomenon (no other cause or condition) have problems in the same fingers on
both sides, but they do not have very much pain.
About 5% of the U.S. population has Raynaud’s.
Aortic Aneurysm
A weakened and bulging area in the aorta, the major blood vessel that feeds
blood to the body. Because the aorta is the body's main supplier of blood, a
ruptured thoracic aortic aneurysm can cause life-threatening bleeding. Depending
on the size and rate at which the thoracic aortic aneurysm is growing, treatment
may vary from watchful waiting to emergency surgery. Once a thoracic aortic
aneurysm is found, doctors will closely monitor it so that surgery can be planned if
it's necessary. Emergency surgery for a ruptured thoracic aortic aneurysm can be
risky.
Citations
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