Circulatory System
Materials once taken into the body must be transported to body tissues.
· Some of these materials include
· Gasses (CO2 & O2)
· Nutrients
· Hormones
· This is done via the circulatory system.
Blood
· Is a liquid tissue
· Is composed of approx. 55% Plasma
· Liquid component of blood
· Contains salts, dissolved nutrients
· Other 45% composed of 3 types of cells
· Red blood cells
· ~5 million RBC'c per cc of blood
· Contains hemoglobin which carries O2 to cells, also carries CO2 away from cells
· Each red blood cell can carry 1 billion molecules of O2
· Live approx. 120 days, and are made in bone marrow at a rate of ~2 million/second
Red Blood Cells
· White Blood Cells
· Defend the cell from infection
· Can engulf bacteria, and produce antibodies to fight viruses
· Can move through body tissues
· Are the target cells of HIV.
· 4000-11000 per cc of blood
White Blood Cell
· Platelets
· Are actually fragments of cells
· Act as "plugs" to form clots surrounding breaks in the blood vessels
Blood Types:
· Determined by presence or absence of certain proteins in blood.
· These are A, B, O (absence of A or B) and Rh (+,-).
· Your body defenses will attack any protein which it does not have.
· Since AB+ have all the proteins, they can accept all blood types, but can only donate to other AB+ persons. They are Universal Recipients.
· Since O- have no proteins, they can Only receive blood from O- persons, but can donate blood to anyone. They are Universal Donors.
Note: You cannot contract HIV or other blood-borne illnesses through donating blood.
Blood Vessels:
Blood is transported throughout the body via blood vessels - There are many types.
Classified according to if they carry blood to or away from the heart.
Away:
· Arteries
· Largest blood vessels.
· Very elastic & thick-Surrounded by layers of smooth muscle.
· Generally lead away from heart & carry oxygenated blood.
· Lead into Arterioles
· Arterioles
· Smaller and thinner than arteries
· Still lead away from heart
· Lead to capillaries
· Capillaries
· Small thin vessels - usually only 1 RBC wide
· Pass next to or near every cell in the body
· Gas (CO2 & O2) & nutrient exchange occur here.
Blood Vessel comparison
Towards Heart
· Venules
· Thin walled vessels collect deoxygenated blood from capillaries.
· Not as elastic as arteries, have little muscle surrounding
· Pass blood into veins
· Veins
· Collect blood from venules
· Thin walled, contain valves which only allow blood to go one way.
· Skeletal muscle "squeeze" the veins to move blood back to the heart.
Veinous valves
Circulatory Pathways of Animals:
· Animals have various types of circulatory systems:
· 2 General categories
o Open circulatory system
§ Usually involves a fluid coined hemolymph
§ Involves blood leaving the vessels to directly contact individual cells.
o Closed circulatory system
§ Blood never leaves vessel structures.
§ Is the vertebrate system.
open vs. closed circulatory systems
· Closed circulatory systems have 3 general schemes, each being increasingly efficient.
o Fish have a 2 chambered system where blood must pass through 2 capillary beds before returning to the heart.
§ Lowers blood pressure
o Reptiles have a 3 chambered system which increases blood flow/pressure since blood must pass through only 1 capillary bed per cycle.
§ Disadvantage: mixes oxygenated & deoxygenated blood
o Mammals have a more efficient system with a 4 chambered heart. Blood pressure is increased and there is no mixing of blood.
Human Circulation
The Cardiac cycle:
· Vocab.
o Systole = contraction phase
o Diastole = relaxation phase
1. Contraction impulse originates from sinoatrial (SA) node (aka. Pacemaker)
2. Induces systole of atria which empty contents into ventricles.
3. Atrioventricular (AV) node delays impulse ~0.1 second.
4. Impulse is carried to the base of ventricles stimulating their contraction
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