1. Circulatory
System

2. *Closed circulatory system in humans
*4 chambered heart
*High levels of oxygen needed by body to maintain homeostasis/ temp.

3. *3 types of blood vessels:
Arteries: transport blood away from heart
Veins: transport blood to heart
Capillaries: 1 layer of cells– exchange of materials

4. *HEART:
*ATRIUM: thin-walled chamber, receives incoming blood
*VENTRICLE: larger, more muscular, thicker-walled;
pumps blood to body

5. PATHWAY OF BLOOD:
Blood w/ low O2 enters right atrium through superior and inferior vena cavae
Right atrium contracts, blood moves to right ventricle
Right ventricle contracts, blood goes through pulmonary artery and into capillaries in lungs (gas exchange takes place)

6. PATHWAY OF BLOOD:
Blood goes from lungs to left atrium through pulmonary veins
Left atrium contracts, blood goes to left ventricle
Left ventricle contracts, blood goes to aorta (largest blood vessel); aorta forms arch & then branches to arteries which branch into capillaries

7. PATHWAY OF BLOOD:
@ capillaries, O2 released, CO2 taken in
Capillaries merge into veins and eventually lead to superior and inferior vena cavae
**There are valves in heart between ventricles/ atria and arteries to prevent backflow!!

8. *The 2 ventricles prevent blood of high and low oxygen levels from mixing!!!
*Blood pressure: as blood is pumped, pressure is exerted on walls of blood vessels

9. FYI: How does blood get back to heart, especially from lower body?
*one way valves in veins open only towards heart
*contraction of skeletal muscles squeeze veins– force blood through valves
*as they relax, valves close and prevent backflow
*breathing also creates a vacuum effect in chest cavity- helps draw blood to heart

10. *HEARTBEAT: “electricity”
*each beat of heart originates in small bundle of tissue in RA: sinoatrial (S-A) node (atria contract)
*impulse eventually travels to atrioventricular (A-V) node; causes ventricles to contract
*Squeezing=  blood pressure- closes hearts valves, opens valves of arteries (where sound of heartbeat comes from)
*Average adult: 70 beats/ min ( during exercise)

11. *Exchange of Materials:
*at capillaries (high surface area)
*DIFFUSION: CO2 and O2
*OSMOSIS: seepage of fluid through space between cells= tissue fluid (fatty acids, Na+); at venous end, low pressure so fluid can seep back in; wastes and nutrients

12. *BLOOD:
*transports nutrients (glucose, fats, O2, AA, ions, vitamins)
*transports hormones from glands to tissues
*transports wastes (CO2, urea)

13. *BLOOD COMPONENTS:
Plasma: yellow fluid
Red blood cells: disk-shaped, no nucleus, contain hemoglobin which transports oxygen
*3 month life span (ANEMIA results when fewer produced than destroyed)
*about 5 million in a mm3 of blood

14. 3. White blood cells: 5 types; round w/ nucleus
*immunity
*10,000 in a mm3 of blood (25,000 w/ infection)
Platelets: cell fragments
*blood clotting
*Also: proteins, hormones, urea, glucose and other nutrients