Grade 9 Biology – Circulatory System & Transport

64 question–answer flashcards covering transport systems, blood composition, vessels, heart anatomy, circulation pathways, cardiac cycle, and coronary disease prevention.

Why do multicellular organisms need transport systems?

Because many cells are far from external surfaces, large quantities of materials must be moved efficiently, and substances often need to travel long distances inside the body.

List three reasons organisms need a transport system.

1) Cells are far apart, 2) Materials must move from one place to another, 3) Large quantities of substances must be transported.

What is the main transport system in humans?

The circulatory system.

Name the three main components of the circulatory system.

Heart, blood vessels, and valves.

Give two major functions of the circulatory system.

Transport nutrients/oxygen to cells and remove waste/carbon dioxide from cells.

Average volume of blood in an adult human.

5–6 litres.

What are the three types of blood cells?

Red blood cells (erythrocytes), white blood cells (leucocytes), and platelets (thrombocytes).

Percentage composition of plasma in blood.

About 55 % of whole blood.

Define plasma.

A pale yellow watery fluid that carries dissolved substances such as nutrients, hormones, antibodies, urea, and carbon dioxide.

Give one example of a waste product carried by plasma.

Urea (to the kidneys).

Which blood component transports most oxygen?

Red blood cells via haemoglobin.

Life span of a typical red blood cell.

≈ 120 days.

Where are old red blood cells destroyed?

Liver and spleen.

Why do mature red blood cells lack nuclei?

To provide more space for haemoglobin, increasing oxygen-carrying capacity.

How does the biconcave shape help RBCs?

It increases surface area for rapid diffusion of oxygen and allows flexibility in narrow capillaries.

Write the reversible reaction involving haemoglobin and oxygen.

Haemoglobin + O₂ ⇌ Oxyhaemoglobin.

What is anaemia and one nutritional cause?

A deficiency of red blood cells or haemoglobin; often caused by lack of iron or vitamin B₁₂.

Two main categories of white blood cells.

Phagocytes (granulocytes) and lymphocytes (agranulocytes).

Role of phagocytes.

Engulf and digest pathogens by phagocytosis.

Role of lymphocytes.

Produce antibodies that neutralise toxins and pathogens.

Approximate WBC count in 1 mm³ of blood.

About 8 000 white blood cells.

Function of platelets.

Initiate blood clotting to prevent bleeding and entry of pathogens.

Enzyme released by damaged platelets.

Thrombokinase (thromboplastin).

Sequence of events in clot formation (simplified).

Thrombokinase + Ca²⁺ & vitamin K → converts prothrombin to thrombin; thrombin converts fibrinogen to fibrin; fibrin forms mesh trapping blood cells, creating a clot.

Scientific names: RBC, WBC, Platelets.

RBC – Erythrocytes; WBC – Leucocytes; Platelets – Thrombocytes.

Compare lumen size in arteries vs. veins.

Arteries have a small lumen; veins have a large lumen.

Why do artery walls contain thick elastic tissue?

To withstand and smooth out the high pressure pulses from the heart.

Describe capillary wall structure.

One cell thick endothelium to allow diffusion of substances.

What prevents backflow of blood in veins?

Semi-lunar (pocket) valves.

Define tissue fluid.

Plasma that has leaked out of capillaries, bathing body cells with nutrients and removing wastes.

State two functions of tissue fluid.

Supplies cells with oxygen/nutrients and removes metabolic wastes.

What is the lymphatic system’s relation to tissue fluid?

Excess tissue fluid enters lymph vessels, becoming lymph, which eventually drains back into the bloodstream.

Name the four chambers of the human heart.

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

Which side of the heart pumps oxygenated blood?

The left side (left atrium/ventricle).

Why is the left ventricle wall thicker than the right?

It must generate higher pressure to pump blood throughout the body, whereas the right ventricle only pumps to nearby lungs.

Function of the atrioventricular valves.

Prevent backflow of blood from ventricles to atria during ventricular contraction.

Name the valves between ventricles and major arteries.

Semi-lunar valves (pulmonary and aortic).

Define pacemaker (SA node).

A patch of specialised muscle in the right atrium that sets the heart’s rhythmic contractions.

Differentiate systole and diastole.

Systole is contraction of heart muscle; diastole is relaxation.

What is a pulse?

The rhythmic surge of pressure felt in arteries with each heartbeat.

Explain single circulation with an example organism.

Blood passes through the heart once per cycle; seen in fish where blood flows heart → gills → body → heart.

Define double circulation.

Blood passes through the heart twice per complete circuit – pulmonary and systemic loops; characteristic of mammals.

Path of pulmonary circulation (start at right ventricle).

Right ventricle → pulmonary artery → lungs → pulmonary veins → left atrium.

Path of systemic circulation (start at left ventricle).

Left ventricle → aorta → body tissues → vena cavae → right atrium.

Give two advantages of double circulation.

Prevents mixing of oxygenated/deoxygenated blood and allows high pressure delivery to systemic tissues while keeping pulmonary pressure low.

What hormone increases heart rate during stress?

Adrenaline.

Define coronary heart disease (CHD).

Narrowing/blockage of coronary arteries reducing blood supply to heart muscle.

List four risk factors for CHD.

Smoking, high blood cholesterol, high blood pressure, stress, age, male gender, poor diet (any four).

What is atheroma?

Fatty cholesterol deposition in artery walls that narrows the lumen.

Define thrombosis.

Formation of a blood clot inside a blood vessel.

Difference between embolism and thrombosis.

Thrombosis is a clot formed in place; an embolism is any clot or solid particle that travels in the bloodstream.

What is angina?

Chest pain caused by partial blockage of a coronary artery leading to reduced oxygen to heart muscle.

Describe a heart attack (myocardial infarction).

Sudden death of heart muscle due to complete blockage of a coronary artery, causing the heart to stop beating effectively.

State two medical treatments for CHD.

Statins (lower cholesterol), angioplasty, coronary bypass surgery, heart transplant (any two).

How do statins help prevent CHD?

They lower blood cholesterol levels and reduce risk of clot formation.

What lifestyle changes help prevent circulatory diseases?

Stop smoking, exercise regularly, limit alcohol, eat balanced diet with less red meat/dairy and more fruits/vegetables.

What is Deep Vein Thrombosis (DVT)?

Formation of a clot in deep veins (often in legs) that can dislodge and cause embolism.

Why is low pressure essential in pulmonary circulation?

High pressure could damage delicate capillaries in the lungs.

What is cardiac output?

Volume of blood pumped by one ventricle per minute (stroke volume × heart rate).

Function of chordae tendineae.

Fibrous cords that anchor atrioventricular valve flaps to papillary muscles, preventing inversion during ventricular contraction.

What triggers increased heart rate during exercise?

Rise in CO₂ lowers blood pH; brain detects this and signals pacemaker to increase rate plus adrenaline release.