NEM 10V Lecture Notes - Lecture 45: Extracellular Fluid, Pulmonary Vein, Gas Exchange
Nematology
Circulatory System:
• The human heart has four chambers and pumps blood through two circuits.
• The pulmonary circuit carries oxygen-poor blood from the right ventricle
- through the pulmonary artery
-to the pulmonary capillaries
- back to the left atrium via the pulmonary vein.
• The systemic circuit carries the blood from:
1. the left ventricle,
2. through the aorta,
3. to the systemic capillaries
4. back to the right atrium.
• As blood leaves the heart, it travels through the vessels in the following order:
1. arteries that have the largest diameter,
2. arterioles,
3. capillaries that are the thinnest vessels with the smallest diameter where
exchange occurs,
4. then to venules and large veins that return blood to the heart.
• A one-way valve is located at the exit of each of the four chambers.
• The four valves open and close as pressure changes
- causing the lup-dup sound of the heartbeat.
• The cardiac cycle is a sequence of relaxation and contraction.
• The atria contract and force more blood into the ventricles.
• The ventricles begin to contract and cause an increase in pressure
-leading to the closing of the atrioventricular valves (the lup sound)
- subsequent opening of the aortic and semilunar valves as blood rushes out.
find more resources at oneclass.com
find more resources at oneclass.com
