Download Heart and Circulation

HEART AND CIRCULATION
Chapter 30 Sections 3 and 4
• If you were to lay out all of the arteries, capillaries and
veins in one adult, end-to-end, they would stretch about
60,000 miles
- By comparison, the circumference of the Earth is
about 25,000 miles (40,000 km). That means a person's
blood vessels could wrap around the planet
approximately 2.5 times!
FLOW OF BLOOD THROUGH THE HEART
1.) Blood returns from the body and enters the heart through
the Superior or Inferior Vena Cava
2.) Blood enters the right atrium
3.) Blood moves into the right ventricle, by going through
the tricuspid valve
4.) Blood then moves to the lungs via the pulmonary
artery.
- Blood gets oxygenated
5.) Blood returns from lungs and enters the left atrium
6.) Blood then moves into the left ventricle via the
mitral valve
7.) Blood leaves the heart through the aorta, and goes to
the body
Components of Blood
• Heart is the main propulsive organ to force blood around the body through veins, arteries,
and capillaries
• What is blood?
- Plasma: the fluid portion of blood,
containing proteins, nutrients, and
other solutes
- Formed Elements: red and white blood
cells and platelets
BLOOD CIRCULATION
• Divided into two distinct processes
- Pulmonary Circulation: Pumps blood between
the heart and lungs
- Systemic Circulation: Pumping of blood to the
rest of body (besides lungs)
• Blood supplies all body tissues with the substances
needed for survival, so it is vital that blood delivery is
ample for tissue demands.
FUNCTIONS OF BLOOD CIRCULATION
• Transport of nutrients
- From digestive tract to tissues, to and from
storage organs
• Transport of metabolites
- Lactic acid from muscle to liver
• Transport of excretory products
- From tissues to excretory organs
• Transport of gases
- Respiratory organs to/from tissues
• Transport of hormones
• Transport of cells
- Including cells of non-respiratory function
• Transport of heat
• Transport of force
- e.g., locomotion (earthworms, spiders),
erection of penis
• Coagulation
BLOOD PRESSURE
• Force blood exerts against the wall of a blood vessel.
- Pressure is highest at the heart end of any artery.
- Pressure decreases in the blood vessels furthest from the heart
• Heart chambers fill during diastole (relaxation of the heart) and pump blood out
during systole (contraction of the heart).
• Normal blood pressure 120/80 mmHg ( book states 120/70 mmHg)
- Various factors can cause an increase or decrease in blood pressure
PERIPHERAL RESISTANCE
• Opposition of blood flow
- measure of the degree to which the blood vessel hinders or resists the flow of
blood
• Main factors in Peripheral Resistance
1.) Blood vessel radius
2.) Blood vessel length
3.) Blood viscosity
RADIUS
• Single most important factor in determining blood flow
resistance
• Smaller the blood vessel radius, the greater the resistance
- due to frictional drag between the blood and the vessel
walls
• Lipid deposits (fats) can cause the radius of an artery to
decrease
- Atherosclerosis
- Can lead to coronary heart disease, heart attack, stroke, or
death
LENGTH OF BLOOD VESSEL
• The longer the vessel length, the greater the
resistance
- Due to friction between the blood and
vessel walls
- The length of a person’s blood vessels
change only as a person grows; otherwise,
length generally remains constant.
BLOOD VISCOSITY
• Measurement of the “thickness” of blood.
• Blood viscosity depends mainly on hematocrit, or the
fractional contribution of red blood cells to total blood
volume.
- The higher the hematocrit, the more viscous the
blood is;
- The lower the hematocrit, the less viscous the
blood.
• Temperatures also has a significant effect on viscosity
- As temperature decreases, viscosity increases