Capillaries: Arterioles branch into capillary networks, or capillary beds. Lowers blood pressure, giving a chance for blood to release nutrients to the body.
The body works efficiently and only sends nutrients to tissues when then they need it. Capillaries do not exist only around the hear but all throughout the body.
Veins: Veins and venules carry blood without oxygen. Blood depleted of nutrients is sent to the heart. They have thin walls because blood pressure is lower far away from the heart.
Vein Walls- 3 Layers
Outer Layer- Connective tissue.
Middle Layer- Smooth muscle and elastic tissue.
Inner Layer- Endothelium
Veins bringing blood back to the heart are able to defy gravity with 3 things:
1. Skeletal and smooth muscle pumps contract blood to heart.
2. Respiratory pumps create contractions that pull blood to the heart.
3. One-way valves prevent blood from flowing backwards.
Blood flows from heart, to arteries to arterioles, to capillaries, to venules, to veins and back.
Pulmonary Circuit
The pulmonary circuit is made up of the pulmonary artery and the pulmonary vein. The pulmonary artery moves blood from the heart to the lungs. The pulmonary vein moves blood from the lungs to the heart.
Systematic Circuit
The systemic circuit carries blood with oxygen from the left ventricle to the various capillaries throughput the body.When the oxygen has been used, veins take it back to the right ventricle of the heart.
Essentially, the pulmonary system works with the lungs and the upper part of the body. The systemic circuit serves the rest of the body.
Hepatic Portal System
The hepatic portal system is a network of veins that carries blood from capillaries in the stomach, intestine, spleen, and pancreas to the liver capillaries.
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