PY 105 Chapter Notes - Chapter 11: Hepatic Portal System, Adipose Tissue, Pulmonary Vein
Circulatory System
1. Distributes nutrients from digestive tract, liver and adipose (fat) tissue
2. Transport oxygen from the lungs to the entire body and carbon dioxide from the tissues to the
lungs
3. Transport metabolic waste products from tissues to excretory system (kidneys)
4. Transport hormones from endocrine glands to targets and provide feedback
5. Maintain homeostasis of body temperature
6. Hemostasis (blood clotting)
• Flow of blood through a tissue is perfusion
• Inadequate blood flow - ischemia
o Results in tissue damage due to shortages of O2 and nutrients and buildup of metabolic
wastes
• When adequate circulation is present but the supply of oxygen is reduced - hypoxia
Components of the Circulatory System
• Transport of blood throughout the body
• Exchange of material between the blood and tissues
• Heart - muscular pump that forces blood though a branching series of vessels to the lungs and the
rest of the body
• Vessels that carry blood away from the heart at high pressure are arteries
• Vessels that carry blood to the heart and low pressure are veins
• As arteries pass farther from the heart, the pressure of blood decreases and they branch into
increasingly smaller arteries called arterioles
• The arterioles pass into capillaries
o Very small vessels often just wide enough from a single blood cell to pass
• Arterioles have smooth muscle in their walls that can act as a control valve to restrict or increase
the flow of blood into the capillaries
• Capillaries are designed to allow the exchange of material between the blood and tissues
• After passing through capillaries, blood collects in small veins called venules, and then into the
veins leading back to the heart
• Veins lack a muscular wall
• The inner lining of all blood vessels is formed by a thin layer of endothelial cell
o Vasodilation and vasoconstriction - the secretion of substances like nitric oxide and
endothelin can regulate vessel diameter
• Important in maintaining blood pressure, tissue oxygenation and thermoregulation
o Inflammation - the release of inflammatory chemicals from injured tissues stimulate
endothelial cells to increase their expression of adhesion molecules
o Angiogenesis - the formation of new blood vessels
• Angiogenic growth factors stimulate endothelial cells to break free from an existing
vessel and proliferate in surrounding tissues
o Thrombosis (blood clotting) - undamaged endothelial cells secrete substances that inhibit
the coagulation cascade, thus preventing the formation of potentially life-threatening clots
• The heart has two sides separated by a thick wall to pump blood in two separate circuits
o The right side of the blood pumps blood to the lungs
o The left side pumps blood to the rest of the body
o The flow of blood from the heart to the lungs and back to the heart is the pulmonary
circulation
o The flow of blood from the heart to the rest of the body and back is the systemic circulation
• Most blood only passes through one set of capillaries before returning to the heart
find more resources at oneclass.com
find more resources at oneclass.com
