Biology – Chapter 6: Transport in Humans

50 question-and-answer flashcards covering Chapter 6 Transport in Humans: need for transport, heart structure, double circulation, cardiac cycle, blood pressure, coronary heart disease, vessel adaptations, blood components, clotting and blood groups.

Because many of their cells are far from the external environment, simple diffusion is insufficient to supply nutrients and oxygen or remove waste, so a specialised transport system is needed.

Why do multicellular organisms require a transport system?

Their single cell lies close to the external environment, so diffusion alone provides oxygen and nutrients and removes waste products.

How do unicellular organisms such as Amoeba obtain nutrients and remove waste?

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

Name the four chambers of the human heart.

The median septum (muscular wall).

What structure separates the right and left sides of the heart to prevent mixing of blood?

Tricuspid valve, bicuspid (mitral) valve, pulmonary semilunar valve, aortic semilunar valve.

List the four valves found in the human heart.

To prevent back-flow and ensure one-way flow of blood through the heart.

What is the primary function of heart valves?

Chordae tendineae.

What fibrous strands anchor the atrioventricular valves to the ventricular walls?

In one complete circuit blood passes through the heart twice: once to the lungs (pulmonary circulation) and once to the rest of the body (systemic circulation).

Define double circulation in humans.

Pulmonary circulation carries deoxygenated blood from the heart to the lungs and back at low pressure; systemic circulation carries oxygenated blood from the heart to the body and back at high pressure.

Differentiate pulmonary circulation from systemic circulation.

Left atrium < right atrium < right ventricle < left ventricle.

Arrange the heart chambers from thinnest to thickest muscular wall.

It must generate a much higher pressure to pump blood through the aorta to the entire body.

Why is the left ventricle wall thicker than the right ventricle wall?

One complete heartbeat consisting of ventricular systole (contraction) and ventricular diastole (relaxation).

What is a cardiac cycle?

The atrioventricular valves – tricuspid and bicuspid (mitral).

During ventricular systole, which valves close to prevent back-flow into the atria?

Closing of the atrioventricular (tricuspid and bicuspid) valves during ventricular systole.

What event produces the "lub" sound of the heart?

The semilunar valves (pulmonary and aortic).

During ventricular diastole, which valves close to stop blood from re-entering the ventricles?

Closing of the semilunar valves when ventricles relax.

What causes the "dub" sound of the heartbeat?

The force per unit area exerted by blood on vessel walls, expressed in mm Hg.

Define blood pressure.

A sphygmomanometer.

What instrument is used to measure blood pressure?

Systolic: 120–140 mm Hg; Diastolic: 75–90 mm Hg.

Give the normal ranges for systolic and diastolic blood pressure in adults.

A blood pressure of 140/90 mm Hg or higher.

At what reading is a person considered hypertensive?

1) Heart receives freshly oxygenated blood first. 2) Blood enters lungs at low pressure, protecting delicate tissues and allowing full oxygenation. 3) Blood leaves left heart at high pressure, delivering oxygen quickly around the body and sustaining a high metabolic rate.

State three advantages of double circulation.

The pericardium.

What membrane encloses the heart?

It reduces friction as the heart beats.

What is the role of pericardial fluid in the pericardial cavity?

Blockage of coronary arteries by fatty deposits (atherosclerosis).

What is the primary cause of coronary heart disease (CHD)?

Build-up and hardening of cholesterol and fats in arterial walls, narrowing the lumen.

Define atherosclerosis.

Formation of a blood clot on the roughened arterial wall, further blocking blood flow.

What is thrombosis in coronary vessels?

Angina (chest pain), heart attack (myocardial infarction), or stroke if a brain artery is blocked.

What major symptoms can result from severe coronary artery blockage?

A blood vessel that carries blood away from the heart, usually oxygenated except the pulmonary artery.

What is an artery?

A blood vessel that carries blood toward the heart, usually deoxygenated except the pulmonary vein.

What is a vein?

A microscopic vessel that connects arterioles to venules and allows exchange of substances between blood and tissues.

What is a capillary?

To withstand and smooth out the high, pulsatile pressure of blood pumped from the heart.

Why do arteries have thick, elastic, muscular walls?

To maintain one-way flow of low-pressure blood back to the heart and prevent back-flow.

Why do veins contain valves?

Contracting muscles compress veins, pushing blood toward the heart; valves stop back-flow.

How does the skeletal-muscle pump aid venous return?

Capillaries.

Which vessel type possesses the greatest total cross-sectional area?

They are one-cell-thick and highly branched, providing a short diffusion distance and a large surface area.

Give two structural adaptations of capillaries for efficient exchange.

Transports digested food, excretory products, hormones, heat, and respiratory gases (oxygen and carbon dioxide).

List the main transport functions of blood.

Albumin – maintains blood viscosity and osmotic pressure; Globulin – includes antibodies for immunity; Fibrinogen – participates in blood clotting.

Name three major plasma proteins and their roles.

Circular, flattened biconcave discs that increase surface area-to-volume ratio for faster gas diffusion.

Describe the shape and advantage of red blood cells (erythrocytes).

It reversibly binds oxygen to form oxyhaemoglobin for oxygen transport.

What is the role of haemoglobin in red blood cells?

Phagocytes and lymphocytes.

Name the two main categories of white blood cells.

Engulfing and ingesting of foreign particles (e.g., bacteria) by phagocytes.

What is phagocytosis?

They produce antibodies that bind to antigens, rupture membranes, cause agglutination, neutralise toxins, or block viral attachment.

How do lymphocytes neutralise pathogens?

Cell fragments that are highly adhesive and initiate clot formation by forming a platelet plug.

What are platelets?

Damaged tissues and platelets release the enzyme thrombokinase, which neutralises heparin to allow clotting.

What is the first step of blood clotting when a vessel is damaged?

Thrombokinase catalyses this conversion (with calcium ions present).

Which enzyme converts prothrombin into thrombin?

Calcium ions (Ca²⁺).

Which ion is essential for the conversion of prothrombin to thrombin?

Fibrinogen is converted into fibrin threads by thrombin.

What soluble protein is converted into insoluble fibrin during clotting?

A classification based on the presence or absence of specific inherited antigens on red blood cells.

Define a blood group.

Antigens A and B on RBCs; no anti-A or anti-B antibodies in plasma.

Which antigens and antibodies are present in blood group AB?

Recipient B’s plasma contains anti-A antibodies that react with donor A’s antigen A, causing agglutination and potential transfusion failure.

Why is transfusing incompatible blood dangerous? Give an example with recipient B and donor A.