4.2.2.2 The heart + blood vessels + blood

3 topics together

What is the heart and what is it’s function?

The heart is an organ that pumps blood around the body in a double circulatory system

What is the function of the right ventricle?

The right ventricle pumps blood to the lungs where gas exchange takes place

What does the left ventricle of the heart do?

The left ventricle pumps blood around the rest of the body.

Label each part:

What controls the natural resting heart rate?

A group of cells located in the right atrium that act as a pacemaker.

What is an artificial pacemaker + what does it do?

It is an electrical device used to correct irregularities in the heart rate.

What is the blood?

Blood is a connective tissue because it connects the body systems by carrying oxygen, nutrients, and waste around the body.

What are the main components of blood?

Plasma, red blood cells, white blood cells and platelets

Where are red blood cells, white blood cells and platelets suspended?

In plasma

What is the purpose of blood plasma in the human body?

Blood plasma transports many substances around the body, for example it:

• Transports carbon dioxide from organs to the lungs for exhalation.

• Carries soluble products of digestion from the small intestine to other organs and tissues.

• Transports urea from the liver to the kidneys, where it is excreted in urine.

Describe the structure of red blood cells and how this helps them do their job:

Their shape is a biconcave disk, this gives them a large surface area for absorbing oxygen. They don’t have a nucleus, which allows more room to carry oxygen

What is the job of red blood cells?

Carrying oxygen from the lungs to all the cells in the body

What is the name of the red pigment that red blood cells contain?

Haemoglobin

What is the purpose of haemoglobin in red blood cells?

In the lungs, red blood cells use their haemoglobin to combine with oxygen, which forms oxyhaemoglobin. They then carry the oxygen to all the organs, where the oxyhaemoglobin splits back into haemoglobin and oxygen, to release oxygen to the cells.

Do white blood cells have a nucleus?

Yes

What are white blood cells?

Blood cells that are part of the immune system. They defend the body against pathogens such as bacteria, viruses, and other harmful microorganisms.

What is the purpose of white blood cells?

White blood cells protect the body by:

• Destroying pathogens directly (e.g., by engulfing them).

• Producing antibodies to target specific bacteria or viruses.

• Producing antitoxins to neutralize toxins produced by pathogens.

What are the main types of white blood cells and their roles?

• Phagocytes – engulf and digest pathogens.

• Lymphocytes – produce antibodies and antitoxins.

What are platelets?

small fragments of cells

Do platelets have a nucleus?

No

What is the function of platelets?

They help the blood clot at the site of a wound

Describe the process of blood clotting:

Blood clotting is a series of enzyme-controlled reactions:

• Platelets stick to the damaged blood vessel.

• Platelets release chemicals that trigger a series of reactions.

• The final reaction causes fibrinogen (a soluble protein) to change into fibrin (insoluble).

• Fibrin forms a network of fibres that trap red blood cells to form a clot.

• The clot dries and forms a scab, protecting the wound as it heals.

How are platelets adapted to clot blood?

Small, disc-shaped - stick to damaged vessels easily.

Contain chemicals - trigger clotting and fibrin formation.

Clump quickly - forms a plug to reduce blood loss.

How is plasma adapted to transport substances?

Liquid - allows easy transport around the body.

Carries dissolved substances - nutrients, CO₂, hormones and urea.

Helps distribute heat - maintains body temperature.

Maintains blood volume - helps circulation and homeostasis.

In what direction do arteries carry blood?

Arteries carry blood away from the heart

In what direction do veins carry blood?

Veins carry blood to the heart.

What are capillaries responsible for?

Exchange of materials at the tissues.

Explain how capillaries are adapted for efficient exchange of substances.

• One-cell-thick walls: Short diffusion distance for gases and nutrients.

• Narrow lumen - slows blood, allowing time for exchange.

• Branched network - increases surface area for efficient diffusion of oxygen, carbon dioxide, and nutrients.

• Permeable walls - substances can diffuse in and out easily

Describe the structure of veins and explain how it relates to their function.

Thinner walls (than arteries): Blood is at lower pressure.

Large lumen: Allows blood to flow easily.

Valves: Prevent backflow of blood.

Explain why blood in veins is under lower pressure than in arteries.

Blood has already passed through capillaries, which slows it down, so veins do not need thick, muscular walls.

Explain how the structure of an artery is related to its function.

Thick, muscular walls: Withstand and maintain high pressure from the heart.

Elastic fibres: Allow expansion and recoil to maintain blood flow.

Narrow lumen: Helps maintain high pressure for rapid blood flow.

What is the formula for calculating the rate of blood flow?

rate of blood flow= volume of blood/ number of minutes