The heart

Question 1

Four main functions of the circulatory system

Answer 1

–> To transport oxygen and carbon dioxide around the body 🡪To distribute nutrients and transport waste
🡪To maintain body temperature
🡪To circulate hormones

Question 1

Blood vessels

Answer 1

Arteries: thick-walled blood vessels that ALWAYS carry blood AWAY from the heart.
Veins: thin-walled blood vessels that ALWAYS carry blood TOWARD the heart.
Arteries 🡪 Arterioles 🡪 Capillaries 🡪 Venules 🡪 Veins
Capillaries:
Narrowest of all blood vessels.
RBCs travel in single file.
Branching of the capillaries increases the surface area available for diffusion.
Connects the arterial & venous systems.

Question 2

The human heart

Answer 2

Muscular organ
Made of 4 chambers separated by the septum (wall of muscle).
About the size of a fist.
Top 2 chambers called the atria (atrium sl.), which are thin walled
Bottom 2 chambers are called the ventricles, which are thick walled
Ventricle walls are much thicker because they have to pump over longer distances. The muscles twist to “wring” the blood out of the ventricles

Question 3

The heart part 2

Answer 3

The right side circulates to the pulmonary circuit (lungs) which means it carries deoxygenated blood
The left side circulates to the systemic circuit (the rest of the body) which means it carries oxygenated blood.
Each beat requires a contraction and relaxation of the heart muscles.
Heart beats over 100 000 times per day, 37 million times per year and 2.5 billion times in your lifetime.
The heart is surrounded by a pericardium- a two layered connective tissue layer with fluid in between. This protects the heart from friction with the other organs and the thoracic cavity.
The heart requires around 10% of the total oxygen load in the blood. It therefore has its own blood supply from the coronary blood vessels.

Question 4

Circulation of blood in the heart(pathway of blood)

Answer 4

When resting, the heart can pump around 5L of blood per minute. At max output it can pump more than 25L per minute.
Deoxygenated blood enters the right atrium via the vena cava, contraction of the right atrium forces the blood into the right ventricle. Right ventricle contracts to force the blood out through the pulmonary arteries to the lungs. Oxygen diffuses to the capillaries from the lungs.
Oxygenated blood enters from the lungs into the left atrium via the pulmonary veins. The left atrium contracts and squeezes blood into the left ventricle, which then forces blood out the aorta to carry blood to different areas of the body.

Question 5

Routes

Answer 5

Pulmonary Circulation:
Right atrium – right ventricle- pulmonary arteries- arterioles- lung capillaries- venules- pulmonary veins- left atrium.
Systemic Circulation:
Left atrium- left ventricle- aorta- arteries- arterioles- capillaries of body cells- venules- veins- superior/inferior vena cava- right atrium.

Question 6

Valves

Answer 6

Atrioventricular valves:
- Located between the atria and ventricles.
- has two or three flaps
- These valves open when when the atria contract
- Once the ventricles have filled that av valves snap shut to prevent backflow of blood to the atria.

Semi-lunar valves:

• has three flaps
• these open when the ventricles contract
• on the right blood is pumped to pulmonary artery and simultaneously on the left blood is pumped into the aorta.
• Once completed, these valves snap shut to prevent the backflow of blood into the ventricles.