Where is it?

• Between the two lungs
• Enclosed by the PERICARDIUM
• Pericardial fluid is secreted between them to aid movement
• The pericardium protects the heart from over expansion

Hold your hand in front of you and make a fist. Squeeze and relax. How long can you do this for?

• The walls of the heart are made of cardiac muscle (MYOCARDIUM)
• Only found in heart
• Never tires but can’t tolerate lack of O2.

Crawford, M.H. (2020). Heart. In World Book Student. Retrieved from

https://www.worldbookonline.com/student-new/#/article/home/ar249920

• The circulatory system circulates blood in two circuits: the pulmonary circuit and systemic circuit.
• The pulmonary circuit is the path of circulation between the heart and the lungs.
• The systemic circuit is the path of circulation between the heart and the rest of the body (excluding the lungs). 

Pulmonary circuit

• The pulmonary circuit is the path of circulation between the heart and the lungs.
• Oxygen depleted blood returns from the body to the right atrium of the heart by two large veins called vena cavae.
• The heart to contracts. As a result, blood in the right atrium is pumped to the right ventricle. On the next heart beat, the contraction of the right ventricle sends the oxygen-depleted blood to the lungs via the pulmonary artery.
• This artery branches into left and right pulmonary arteries. In the lungs, carbon dioxide in the blood is exchanged for oxygen at lung alveoli.
• Alveoli are small air sacs that are coated with a moist film that dissolves air.
• The now oxygen-rich blood is transported back to the heart by the pulmonary veins. The pulmonary veins return blood to the left atrium of the heart. When the heart contracts again, this blood is pumped from the left atrium to the left ventricle.

Key Questions

1. What are the primary functions of the Cardiovascular System?
2. Compare the features of veins and arteries.
3. Explain the two circuits of the circulatory system
4. Define what an acute response to exercise is, give 2 examples.
5. Using an analogy, explain the path that red blood cells take, to get around the body

Retrieved 20/03/2020 from https://upload.wikimedia.org/wikipedia/commons/5/59/Dissected_pig_heart.jpg

• Blood comes into the heart from the body
• It then has to pass to the lungs to collect  oxygen (pulmonary circuit)
• This is called a double circulatory system (heart and lungs, heart and body)
• After it returns to the heart it leave again to be transported to the body (systemic circuit).

• All arteries pump oxygenated blood & all veins carry deoxygenated blood?
• FALSE!!!!
• Pulmonary artery pumps deoxygenated blood to the lungs for oxygenation and pulmonary veins transport the blood oxygenated from the lungs back to the heart to be pumped around the body

• Blood pressure is the reason why blood circulates.
• Blood will always flow from an area of high pressure to one of low pressure.
• SYSTOLIC blood pressure is the highest pressure and is the pressure on the arteries as the left ventricle contracts. ( 120 mmhg at rest )
• DIASTOLIC blood pressure is the lowest pressure and is the pressure on the arteries as the left ventricle relaxes. ( 80 mmhg at rest )

Acute responses to exercise

• Increased heart rate ( beats per minute )
• Increased stroke volume ( blood per beat )
• Increased cardiac output ( HR X SV )
• Increased systolic blood pressure ( diastolic remains fairly constant )
• Increased arterio-venous O2 diff.
• Decreased blood plasma ( due to sweating )
• Increased blood flow to working muscles
• Increased blood flow to lungs
• Decreased blood flow to some organs ( digestion )

Stages of Cardiac cycle 

• Diastole – the phase of the heartbeat when the heart muscle relaxes and allows the chambers to fill with blood.
• Systole – the phase of the heartbeat when the heart muscle contracts and pumps blood from the chambers into the arteries.

Systemic system

• The systemic circuit is the path of circulation between the heart and the rest of the body (excluding the lungs). Oxygen-rich blood in the left ventricle leaves the heart via the aorta. This blood is circulated to the rest of the body by various major and minor arteries.
• Coronary Arteries: blood vessels that branch off from the ascending aorta. They supply blood to the heart.
• Brachiocephalic Artery: supplies blood to the head, neck and arms.
• Celiac Artery: supplies blood to the abdominal area.
• Splenic Artery: supplies blood to the spleen, stomach, and pancreas.
• Renal Arteries: supply blood to the kidneys.
• Common Iliac Artery: supplies blood to the legs and feet.
• Gas, nutrients, and waste exchange between blood and body tissues takes place in the capillaries. Blood flows from arteries to smaller arterioles and on to the capillaries. In organs such as the spleen, liver, and bone marrow that do not have capillaries, this exchange occurs in vessels called sinusoids. After passing through the capillaries or sinusoids, the blood is transported to venules, to veins, to the superior or inferior vena cavae, and back to the heart.