Download circulatory system notes honors 09

Hemoglobin
Oxygen is carried in the human blood by the respiratory pigment hemoglobin, which combines loosely
with oxygen molecules to form the molecule oxyhemoglobin.
To function in the transport of oxygen, hemoglobin must be able to bind with oxygen in the lungs and
unload it at the body cells. That means that the more
tightly the hemoglobin binds to oxygen in the lungs, the more difficult it is to unload the oxygen at the
cells.
Transport of Carbon Dioxide
Carbon dioxide, the by-product of cell respiration, is released from every cell an dissolves in the blood to
form carbonic acid. Therefore, the higher the carbon dioi ide concentration in the blood, the lower the pH.
Very little carbon dioxide is transported by hemoglobin. Most carbon dioxide] carried in the plasma as
part of the reversible blood-buffering carbonic acid bicarbonate ion system, which maintains the blood at
a constant pH of 7.4.
CIRCULATION
Human circulation consists of a closed circulatory system with arteries, veins, and capillaries.
Structure and Function of Blood Vessels
Artery Carries blood away from the heart Walls made of thick layer of elastic, under enormous pressure
smooth muscle. Can withstand high pressure and can contract and expand as needed.
Vein Carries blood back to the heart under Walls do not contain thick layer of muscle very little pressure
Has valves to help prevent backflow. Located within skeletal muscle, which
propels blood upward and back to heart a the body moves and muscles contract.
Capillary Allows for diffusion of nutrients and Walls are one-cell thick and so small that wastes between
cells and blood blood cells travel only single file.Blood travels slowly here to allow time for
diffusion of nutrients and wastes.
Components of Blood
Blood consists of several different cell types suspended in a liquid matrix plasma. The average
human body contains 4 to 6 liters of blood.
The Mechanism of Blood Clotting
Blood clotting is a complex mechanism that begins with the release of clotting factots
from platelets and damaged tissue. It involves a complex set of reactions.
Anticlotting factors constantly circulate in the plasma to prevent the formation of a
clot or thrombus, which can cause serious damage in the absence of injury. Serum
is plasma minus clotting factors. Calcium is necessary for normal blood clotting.
Here is the pathway of normal clot formation:
The Heart
The heart is located beneath the sternum and is about the size of your clenched It beats about 70 beats per
minute and pumps about 5 liters of blood—the total volume of blood in the body—each minute. Two
atria (atria, plural; atrium, singular) receive blood from the cells of the body, two ventricles pump blood
out of the heart.
The heart itself has its own pacemaker, the sinoatrial (SA) node, which sets timing of the contractions of
the heart. Electrical impulses travel through the cardiac and body tissues to the skin, where they can be
detected by an electrocardiogram (EKG). The heart’s pacemaker is influenced by a variety of factors: the
nervor system, hormones such as adrenaline, and body temperature.
Blood pressure is lowest in the veins and highest in the arteries when the ventricles contract. Blood
pressure for all normal resting adults is 120/80. The systol, number (120) is a measurement of the
pressure when the ventricles contract, while the diastolic number (80) is a measure of the pressure when
the heart relax Remember that the right side of the heart in the figure is actually the left side of heart in
the body.
PATHWAY OF BLOOD
Blood enters the heart through the vena cava. From there it continues to the:
1.
Right atrium
2. Right atrioventricular (AV) valve or tricuspid valve
3. Right ventricle
4. Pulmonary semilunar valve
5. Pulmonary artery
6. Lungs
7. Pulmonary vein
8. Left atrium
9. Left atrioventricular (AV) valve or bicuspid valve
10. Left ventricle
11. Aortic semilunar valve
12. Aorta
13. To all the cells in the body
14. Returns to the heart through the vena cava
Blood circulates through the coronary circulation (heart), renal circulation (kidneys), and the hepatic
circulation (liver). The pulmonary circulation includes the
pulmonary artery, lungs, and the pulmonary vein.
One thing to remember is that the pulmonary artery is the only artery that carries deoxygenated blood and
the pulmonary vein is the only vein that carries oxygenated blood.
2.