Human Circulatory System

What is the human circulatory system?

A closed system of tubes with a pump and valves to ensure one-way flow of blood

What ensures one-way blood flow in the circulatory system?

The heart, blood vessels and valves.

What is a closed circulatory system?

A system where blood remains inside the vessels.

What is single circulation?

Blood travels through the heart once each complete circuit.

Which animals in the notes have single circulation?

Fish.

What is double circulation?

Blood travels through the heart twice each complete circuit.

What are the two parts of double circulation?

Pulmonary circulation and systemic circulation.

What is pulmonary circulation?

Blood flow between the heart and lungs.

What is the main function of pulmonary circulation?

Carries deoxygenated blood from the heart to the lungs and returns oxygenated blood to the heart. (MAIN)

How does pulmonary circulation pressure compare with systemic circulation?

It has lower pressure.

How does pulmonary circulation distance compare with systemic circulation?

It is shorter. (heart → lungs)

What happens to oxygen in the lungs?

It diffuses from the lungs into the blood.

What happens to carbon dioxide in the lungs?

Carbon dioxide diffuses out from the blood into the lungs. (Exchange of gases takes place in the lungs)

Where does oxygen-rich blood go after leaving the lungs?

Back to the heart.

What is systemic circulation?

Blood flow between the heart and body tissues except the lungs.

What is the main function of systemic circulation?

Transports oxygenated blood from the heart around the body and returns to the heart with deoxygenated blood (MAIN)

Deliver oxygen, hormones and nutrients and collect carbon dioxide and waste.

How does systemic circulation pressure compare with pulmonary circulation?

It has higher pressure.

How does systemic circulation distance compare with pulmonary circulation?

It is longer. (heart to entire body)

What are the advantages of double circulation?

(It allows different pressures in the pulmonary and systemic circulation.)

Pressure in the systemic circulation is high enough to serve the body efficiently; pressure in the pulmonary circulation can be lower to ensure slower blood flow and hence a more efficient diffusion of oxygen and carbon dioxide between the capillaries and the air sacs of the lungs.

Oxygenated blood (left side) is separate from deoxygenated blood (right side)

What is the heart?

A muscular bag that pumps blood by expanding in size, filling with blood, then contracting, forcing blood on its way.

How does the heart pump blood?

It expands in size, fills with blood and then contracts to force blood on its way

Why is the heart described as two pumps in one?

Each side pumps blood through a different circulation.

What are the parts of the heart RIGHT TO LEFT

RIGHT

Superior vena cava

Semilunar valves

Right atrium

tricuspid valve

Right ventricle

Inferior vena cava

MIDDLE:

Septum

Coronary artery

Coronary veins

LEFT

Aortic Arch

Pulmonary artery

Pulmonary veins

Left atrium

“Heart strings” (both in bicuspid and tricuspid)

Bicuspid valve

Left ventricle

What are the atrioventricular valves?

Bicuspid valve

Tricuspid valve

What are the semilunar valves?

Aortic valve

Pulmonary valve

What does the right side of the heart do?

Pumps blood to the lungs to collect oxygen

What does the left side of the heart do?

Pumps oxygenated blood around the rest of the body

Where does deoxygenated blood return after circulating through the body?

The right side of the heart. (to be sent to the lungs again)

What are the four chambers of the heart?

Right atrium, right ventricle, left atrium and left ventricle.

What does the right atrium receive?

Deoxygenated blood from the superior vena cava (carries blood from the upper parts of the body to the heart) and the inferior vena cava (carries blood from the lower parts of the body to the heart)

Where does blood move after the right atrium?

Into the right ventricle.

What does the right ventricle do?

Pumps deoxygenated blood to the lungs.

What does the left atrium receive?

Oxygenated blood from the pulmonary veins

Where does blood move after the left atrium?

Into the left ventricle.

How does blood enter the ventricles?

Left and right atria contract and squeeze blood into the right and left ventricles respectively

What does the left ventricle do?

Pumps oxygenated blood around the body.

Which chamber has a much thicker wall than the atrium?

The left ventricle.

Why does the left ventricle need a thick muscular wall?

It pumps blood through the high-pressure systemic circulation.

How does the blood flow through the right ventricle?

The right ventricle contracts. As it contracts, deoxygenated blood is pumped to the lungs through the pulmonary artery. The tricuspid valve prevents the backflow of blood into the right atrium during the contraction of the right ventricle.

How does the blood flow through the left ventricle?

The left ventricle contracts. As it contracts, the heart pumps oxygenated blood to all parts of the body via the aorta. The left ventricle has a thicker wall than the right ventricle, as blood must be pumped at high pressure to reach all parts of the body efficiently.

The bicuspid valve prevents the backflow of blood into the left atrium when the left ventricle contracts.

What happens after they send the blood off?

The ventricles relax, and the semilunar valves close to prevent backflow of blood into the ventricles.

What are heartstrings? (chordae tendineae)

Tendons that hold down the bicuspid and tricuspid valves and prevent them from everting.

What is the septum?

A dividing wall that separates the right and the left ventricles in the heart.

Through what type of vessel does blood leave the heart?

Arteries.

Through what type of vessel does blood return to the heart?

Veins.

What does the aorta carry?

Oxygenated blood from the heart to the body.

What does the vena cava carry?

Deoxygenated blood from the body to the heart.

What does the superior vena cava return blood from?

The head and arms.

What does the inferior vena cava return blood from?

The lower body.

What does the pulmonary artery carry?

Deoxygenated blood from the heart to the lungs.

What is unusual about the pulmonary artery?

It is an artery that carries deoxygenated blood.

What do the pulmonary veins carry?

Oxygenated blood from the lungs to the heart.

What is unusual about the pulmonary veins?

They are veins that carry oxygenated blood.

What does the hepatic artery carry blood to?

The liver.

What does the hepatic vein carry blood from?

The liver.

What does the renal artery carry blood to?

The kidneys.

What does the renal vein carry blood from?

The kidneys.

What does the hepatic portal vein connect?

The gut to the liver.

What do coronary arteries do?

Supply the heart muscle with oxygenated blood and nutrients

What do coronary veins do?

Carry deoxygenated blood from the heart to the lungs

What is needed if coronary arteries are blocked?

Bypass surgery → heart cannot be deprived of oxygen, as it works very hard to keep the circulatory system functioning effectively.

What is the pathway of deoxygenated blood through the heart?

Body → right atrium → right ventricle → lungs.

What is the pathway of oxygenated blood through the heart?

Lungs → left atrium → left ventricle → body.

What is the complete basic pathway of blood?

Body → right heart → lungs → left heart → body.

What is the basic vessel sequence from arteries back to veins?

Artery → (branch into smaller) arteriole → capillary → venule(smaller branches of veins) → vein.

What are atrioventricular valves?

Valves between the atria and ventricles.

Where is the tricuspid valve?

Between the right atrium and right ventricle.

Where is the bicuspid valve?

Between the left atrium and left ventricle.

What is another name for the bicuspid valve?

Mitral valve.

What are semilunar valves?

Valves guarding the exits from the ventricles.

Which semilunar valve leads to the lungs?

The pulmonary valve.

Which semilunar valve leads to the aorta?

The aortic valve.

What happens to semilunar valves when the ventricles relax?

They close.

What happens to atrioventricular valves when the ventricles relax?

They open.

What causes the heart's "lub" sound?

Closure of the atrioventricular valves.

What causes the heart's "dup" sound?

Closure of the semilunar valves.

What do heart strings prevent?

Valves everting during ventricular contraction.

What are the three main types of blood vessel?

Arteries, veins and capillaries.

What is the main function of arteries?

Transport blood away from the heart (branches into smaller arterioles then into capillaries)

What are artery walls like?

Thick, muscular, elastic and smooth muscle wall to withstand high blood pressure.

Muscular layer to control the diameter of the artery.

The elasticity of the vessel also helps maintain blood pressure.

Why are artery walls contain more smooth and elastic muscles?

To stretch and recoil with systole and diastole

What is an artery lumen like?

Cylindrical shape, narrower than veins to maintain high blood pressure

What is blood pressure in arteries like?

High.

What is blood flow in arteries like?

Fast, under pressure, and in spurts (pulses).

Do arteries normally contain valves?

No. (absent other than in pulmonary artery and aorta as they exit from the heart)

What type of blood do most arteries carry?

Oxygenated blood.

What is the exception to arteries carrying oxygenated blood?

The pulmonary artery.

How is flow maintained in the arteries?

Contraction of heart muscle

What is the main function of veins?

Return blood to the heart.

What are vein walls like?

Thinner wall, thin muscular layer, and contains fewer elastic muscles than artery walls.

Why can veins have thinner walls?

Blood in veins is at lower pressure.

What is a vein lumen like? Why?

Wider than an artery of comparable size to reduce resistance to blood flow at low pressure

What is blood pressure in veins like?

Low.

What is blood flow in veins like?

Slow and smooth but faster than in capillary

What helps move blood through veins? (how is it maintained?)

Contractions of surrounding skeletal muscles squeeze the veins between them.

Do veins have valves?

Yes (present to prevent backflow due to low pressure)

What type of blood do most veins carry?

Deoxygenated blood.

What is the exception to veins carrying deoxygenated blood?

The pulmonary veins.

What is the main function of capillaries?

Allow exchange between blood and tissues.

Describe the walls of capillaries

One cell thick, partially permeable: to decrease diffusion distance + increase diffusion rate

→ allows water and dissolved substances to diffuse through the wall easily. Allows WBC to pass through but not RBC or plasma proteins