Sources:
Khan Academy
General Information
I. Circulatory System Organs
a. Cells constantly need new nutrients and oxygen. System that distributes these nutrients and oxygen is the circulatory system. The circulatory system transports nutrients and oxygen as well as carries away waste from cells. In addition, the circulatory system also repairs tissue and protects the body from infection.
b. Circulatory system has three main parts: blood, heart, and blood vessels.
--> Blood
- Pumped through the heart to the rest of the body
- Is a connective tissue that is composed of cells and liquids
- Flows through blood vessels, another part of the circulatory system
--> Heart
- In humans, a 4-chambered muscular organ
- Flow of blood: from heart to tissues (delivers nutrients and oxygen) then throughout the body and back to the heart. Cycle then starts again
--> Blood vessels:
- Resting takes about a minute for all blood to circulate throughout the body (full cycle from heart to tissue then back to heart) and increased activity (depending on amt. of activity) increases the speed of circulation
1. Capillaries
i. Arteries branch into smaller and smaller blood vessels, called capillaries
ii. Capillaries allow close contact to all cells in the body
iii. Allows diffusion of nutrients and oxygen outside the blood and diffusion of waste products into the blood.
2. Arteries
i. Takes blood away from heart - from heart to capillaries (smallest, thinnest blood vessels)
ii. Muscle tissue lets artery constrict and dilate (contract and relax)
iii. Pressure in arteries helps with blood flow
3. Veins
i. Brings blood back to the heart
II. Lymphatic System
a. Approximately 4 liters of blood a day to interstitial fluid - lymphatic system retrieves fluid to the circulatory system
b. Collected fluid is called lymph
c. Lymph nodes = enlargements in lymph tissue
(http://www.phschool.com/science/biology_place/biocoach/cardio2/circuits.html)
III. Circuits of Blood Flow
a. Pulmonary circuit - brings deoxygenated blood from the heart to the lungs and oxygenated blood (by alveoli) back to the heart
b. Systemic circuit - brings oxygenated blood from the heart to the rest of the body and deoxygenated blood back to the heart
c. Blood is either flowing in pulmonary or systemic circuit
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