1. Circulatory System

2. Do Now
Why is it important for your heart to continue beating even when you’re sleeping?
What does your body need?
What are some wastes?

3. Circulation and Respiration
Each breath brings oxygen rich air into your body
Your cells need that oxygen
Your heart delivers oxygen to your cells
Working together, your circulatory and respiratory systems supply cells throughout the body with the nutrients and oxygen that they need to stay alive!

4. Multicellular Needs
Unicellular organisms don’t need a circulatory system, because the cell is in direct contact with the environment and oxygen, nutrients and wastes can easily diffuse across the cell membrane by diffusion.
Multicellular organisms need a circulatory system to transport substances made in one part of the body to sites where they are needed in another part of the body.

5. Function
The circulatory system transports substances including oxygen, nutrients and wastes to and from cells responding to changing demands by diffusion (from high to low concentration along concentration gradient).

6. Structure Humans have a closed circulatory system.
Blood is pumped through a system of vessels
(In an open system, blood flows in vessels and sinuses/gills)
Sometimes the circulatory system is also called the “cardiovascular system” because:
Cardio = heart
Vascular = vessels
The human circulatory system consists of:
The heart
A series of blood vessels
Blood that flows through them

7. The Heart Located near the center of your chest
A hollow organ about the size of your fist composed of cardiac muscle.
Enclosed in a protective sac of tissue called the pericardium
Inside there are two thin layers of epithelial and connective tissue
Contractions of the myocardium, a thick cardiac muscle, pump blood through the circulatory system
The heart contracts about 72 times a minute
Each contraction pumps about 70 mL of blood

8. Heart
Septum, or wall, separates the right side form the left side preventing mixing of oxygen-rich blood and oxygen-poor blood
Flaps of connective tissue called valves divide each side into 2 chambers: totaling 4 chambers
Upper chambers receive blood = atrium
Lower chambers pump blood out of heart = ventricle

9. Types of Circulation
Pulmonary circulation = from right side of the heart to lungs where carbon dioxide leaves the blood and oxygen is absorbed
Systemic circulation = from left side of the heart to organs
Coronary circulation = through heart tissue

10. Pulmonary Circulation
The right side of the heart pumps blood from the heart to the lungs
In the lungs, carbon dioxide leaves the blood while oxygen is absorbed.
The oxygen-rich blood goes into the left side of the heart

11. Systemic Circulation
The oxygen-rich blood from the left side of the heart is pumped to the rest of the body
Oxygen-poor blood returns to the right side of the heart
This blood is oxygen-poor because the cells absorbed the oxygen and released carbon dioxide into the blood
The oxygen-poor blood is ready for another trip to the lungs to get oxygen again

13. Figure 37-2 The Circulatory System
Section 37-1
Capillaries of head and arms
Capillaries of abdominal organs and legs
Inferior vena cava
Pulmonary vein
Capillaries of right lung
Superior vena cava
Aorta
Pulmonary artery
Capillaries of left lung

14. Coronary Circulation
Remember: the heart is an organ and needs nutrients, oxygen and creates wastes.
Blood flows to the tissues of the heart too!

15. Blood Flow through the heart
Blood leaves the heart in arteries, and blood returns to heart in veins.
Oxygenated blood returns from the lungs through the pulmonary veins to the left atrium.
Oxygenated blood is pumped from the left atrium through the mitral valve to the left ventricle.
Oxygenated blood leaves the left ventricle through the aortic valve to the aorta, which is the largest artery of your body.
The aorta branches into various arteries pumping blood through your body.
Deoxygenated blood returns from the top of your body through the superior vena cava and from the bottom of your body through the inferior vena cava to the right atrium.
Deoxygenated blood is pumped from the right atrium through the tricuspid valve to the right ventricle.
Deoxygenated blood leaves the right ventricle through the pulmonary valve to the pulmonary arteries.
The pulmonary arteries pump blood to the lungs to absorb oxygen and release carbon dioxide.
Heart circulation animation:

16. The Path of Blood

17. Valves
Blood enters into the atria of the heart, separated from the ventricles by valves, preventing back-flow of blood keeping the blood flowing in one direction
When the atria contract, the valves open and blood flows into the ventricles
When the ventricles contract, the valves close preventing blood from flowing back into the atria and blood flows out of the heart
At the exits of the ventricles, there are valves that prevent blood from flowing back into the heart
The “lub-dup” sound of your heart is caused by the closing of the heart’s valves. The “lub” is when the ventricles contract and blood being forced against the artioventricular or A-V (tricuspid or mitral) valves. The “dup” is the blood being forced against the semilunar (aortic or pulmonary) valves.

18. Figure 37-3 The Structures of the Heart
Section 37-1
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

19. Heartbeat There are two muscle contractions in the heart:
The atria
The ventricles
Each contraction begins in a small group of cardiac muscle cells in the right atrium that stimulate the rest of the muscle cells = sinoatrial node (SA node)
Since the sinoatrial node sets the pace for the heart it is also called “the pacemaker”
The impulse spreads from the pacemaker through fibers in the atria to the atrioventricular node (AV node) and through fibers in the ventricles
When the atria contract, blood flows into the ventricles
When the ventricle contract, blood flows out of the heart

20. The Sinoatrial Node Section 37-1 Contraction of Atria
Contraction of Ventricles
Sinoatrial (SA) node
Conducting fibers
Atrioventricular (AV) node

21. Changing Heartbeat
Your heart can beat faster or slower, depending on your body’s need for oxygen-rich blood
When you exercise, your heart rate can increase to 200 beats per minute
The autonomic nervous system influences heart rate
Neurotransmitters released by neurons in the sympathetic nervous system can increase heart rate, and those released by the parasympathetic nervous system can decrease heart rate

22. Blood vessels
Blood circulates in one direction and it is moved by the pumping of the heart
As blood flows through the circulatory system, it moves through three types of blood vessels:
Arteries
Capillaries
Veins

23. Arteries
Large vessels that carry blood away from the heart to tissues of the body
Except for the pulmonary arteries, all arteries carry oxygen-rich blood.
Arteries have thick walls of elastic connective tissue, contractible smooth muscle, and epithelial cells that help them withstand the powerful pressure produced when the heart contracts and pushes blood into the arteries.

24. Capillaries
The smallest of the blood vessels connecting arteries and veins
Walls are one cell thick allowing for easier diffusion of nutrients and oxygen from capillaries to body cells and wastes and carbon dioxide from body cells to capillaries

25. Veins Return blood to the heart
Veins have walls of connective tissue and smooth muscle
Large veins contain valves that keep blood flowing towards the heart
Many veins are located near skeletal muscles, so when the muscles contract, they help force blood through the veins, even against gravity
Exercise helps prevent accumulation of blood in limbs and stretching veins out of shape

26. Figure 37-5 The Three Types of Blood Vessels
Section 37-1
Artery
Vein
Connective tissue
Smooth muscle
Endothelium
Valve
Venule
Arteriole
Capillary

27. Blood Pressure The heart produces pressure when it contracts.
The force of blood on the arteries’ walls = blood pressure
Blood pressure decreases when the heart relaxes, but there must always be some pressure to keep the blood flowing
Doctors measure blood pressure with a sphygmomanometer recording two numbers
Systolic pressure = force felt in arteries when ventricles contract
Diastolic pressure = force of blood felt in arteries when ventricles relax
Average adult’s blood pressure = 120/80

28. Regulating Blood Pressure
With the nervous system:
Sensory neurons at several places in the body detect blood pressure and send impulses to brain stem (medulla oblongata)
When too high, the autonomic nervous system releases neurotransmitters that cause the smooth muscles around blood vessels to relax, lowering blood pressure.
When too low, neurotransmitters are released that cause the smooth muscles to contract, elevating blood pressure.
With the endocrine/excretory system:
Hormones produced by the heart and other organs cause kidneys to remove more water from the blood when blood pressure is too high, reducing blood volume and lowering blood pressure

29. Disorders Disorders of the circulatory system are very common:
High Blood Pressure
Heart Attack
Stroke
Most stem from atherosclerosis = fatty deposits (plaque) builds up on walls of arteries, obstructing blood flow, increasing blood pressure and risk of blood clots

30. High Blood Pressure Also known as Hypertension
Forces heart to work harder, which may weaken or damage the heart muscle and vessels
More likely to develop heart disease and increased risk of heart attack and stroke

31. Heart Attack A medical emergency
Coronary arteries (supplying heart blood) bring oxygen and nutrients to the heart muscle itself
Blockage of coronary artery may damage or kill part of heart muscle (myocardium) due to lack of oxygen = heart attack
Symptoms include: chest pain/pressure, feeling of heartburn/indigestion, sudden dizziness, or brief loss of consciousness

32. Stroke
Blood clots may break free from vessels and get stuck in a blood vessel leading to a part of the brain = stroke
Brain cells relying on that vessel may begin to die from lack of oxygen and brain function in that region may be lost
Strokes can also occur when a weakened artery in the brain burst, flooding the area with blood

33. Prevention Cardiovascular diseases are easy to prevent:
Exercise – increases respiratory system’s efficiency
Weight control – reduces body fat and stress
Sensible diet – low in saturated fat reduces risk of heart disease
Not smoking – reduces risk of heart disease