1. Circulatory System
Chapter 37-1

2. The Circulatory System
We need oxygen to live!
Blood brings air to our cells so oxygen can be absorbed and used to produce energy for the cell
The circulatory system transports blood throughout the body and back
The CS consists of the heart, a series of blood vessels, and the blood that flows through them

3. The Heart The heart is approximately the size of a clenched fist.
It is made almost entirely of muscle.
Myocardium: thick layer of muscle which produces powerful contractions to pump blood through the circulatory system.

4. The Heart Useless facts…
The heart is the strongest muscle in the human body
The heart pumps about 72 times a minute on average
Each pump pushes 70ml of blood
In one year, a heart pumps enough blood to fill up an olympic-size swimming pool!

5. The Heart Figure 37-3 The Structures of the Heart Section 37-1 Aorta
Inferior Vena Cava
Vein that brings oxygen-poor blood from the lower part of the body to the right atrium
Tricuspid Valve
Prevents blood from flowing back into the right atrium after it has entered the right ventricle
Pulmonary Valve
Prevents blood from flowing back into the right ventricle after it has entered the pulmonary artery
Pulmonary Veins
Bring oxygen-rich blood from each of the lungs to the left atrium
Superior Vena Cava
Large vein that brings oxygen-poor blood from the upper part of the body to the right atrium
Aorta
Brings oxygen-rich blood from the left ventricle to the rest of the body
Pulmonary Arteries
Bring oxygen-poor blood to the lungs
Aortic Valve
Prevents blood from flowing back into the left ventricle after it has entered the aorta
Mitral Valve
Prevents blood from flowing back into the left atrium after it has entered the left ventricle
Left Atrium
Right Atrium
Left Ventricle
Septum
Right Ventricle

6. The Heart The heart can be divided into four chambers
Atrium: upper chambers which receive blood (enters)
Ventricle: The lower chambers which pump blood out of the heart (exits)

7. Circulation Think of the heart as two separate pumps.
Pulmonary circulation: Right side of heart that pumps blood from the heart to the lungs
Systemic circulation: Left side of heart that pumps blood oxygen-rich blood to the rest of the body

8. Capillaries of head and arms
Superior vena cava
Aorta
Pulmonary artery
Pulmonary vein
Capillaries of right lung
Capillaries of left lung
Inferior vena cava
Capillaries of abdominal organs and legs

10. Circulation Oxygen-poor blood enters heart through right atrium.
Valve (connective tissue that opens & closes) opens so blood froms from R atrium to R ventricle.
R ventricle pumps blood to lungs
Lungs replenish blood with oxygen
Oxygen-rich blood then flows to L atrium

11. Circulation
Valve opens and oxygen-rich blood flows from L atrium to L ventricle
L ventricle pumps blood to the body
Body absorbs oxygen
Oxygen-poor blood goes back to the heart
Cycle starts over!

12. Circulation Atriums contract first (by sinoatrial node)
Contraction of atrium by SA triggers the ventricles to contract (atrioventricular node or AV)
Together, these two nerves serve as the pacemaker.
Remember sympathetic and parasympathetic?
During exercise, sympathetic increases heart rate (can go up to 200bpm) and parasympathetic decreases it

13. Blood Vessels
Aorta: Large blood vessel where blood first leaves the L ventricle
Arteries: carry oxygen rich blood
They have thick walls to withstand the pressure of bloodflow
Think of arteries as the superhighways of the CS

14. Blood Vessels
Capillaries: Narrow tubes where body absorbs oxygen and nutrients are exchanged
Can be as narrow as one cell wide
Think of capillaries as side streets and alleys

15. Blood Vessels Veins: Blood vessels that return blood to the heart
Thinner than arteries
Larger veins have valves to prevent backflow
Muscular contractions help push blood through veins
Otherwise, blood pools and vericose veins result

16. Artery
Vein
Connective tissue
Smooth muscle
Endothelium
Valve
Venule
Arteriole
Capillary

17. Blood Pressure Heart produces pressure when it pumps.
The pressure allows blood to flow throughout the body
If pressure is too low, oxygen can’t get to body
If pressure is too high, heart has to work harder, damaging the CS

18. Blood Pressure BP is measured by systolic & diastolic pressures
Systolic is the blood pressure when a ventricle contracts
Diastolic is the blood pressure when a ventricle relaxes
Normal BP is 120/80
Atherosclerosis, a hardening of the arteries due to fat is a major cause of HBP and heart disease
Result is heart attack or stroke