Transport in Humans Candidates should be able to: (a) name the main blood vessels to and from the heart, lungs, liver and kidney (b) state the functions.

Transport in HumansCandidates should be able to:

(a) name the main blood vessels to and from the heart, lungs, liver and kidney

(b) state the functions of blood• red blood cells – haemoglobin and oxygen transport• white blood cells – phagocytosis, antibody formation and tissue rejection• platelets – fibrinogen to fibrin, causing clotting• plasma – transport of blood cells, ions, soluble food substances, hormones, carbon dioxide, urea, vitamins, plasma proteins

(c) relate the structure of arteries, veins and capillaries to their functions

(d) describe the structure and function of the heart in terms of muscular contraction and the working of valves (histology of the heart muscle, names of nerves and transmitter substances are not required)

(e) describe coronary heart disease in terms of the occlusion of coronary arteries and list the possible causes, such as diet, stress, smoking, and the possible preventative measures

1© Nur Huda (2012)

Main blood vessels

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Heart

Vena cava(from the body)

Pulmonary artery(to the lungs)

Aorta (to the body)

Pulmonary vein(from the lungs)

Left atrium

Left ventricle

Thick muscular wall of left ventricle

Right atrium

Right ventricle

Semi-lunar valve

Tricuspid valve Bicuspid valve

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deoxygenated oxygenated

HeartRight atrium• Receives deoxygenated blood from vena cava• Right atrium contracts, force blood to enter right

ventricle

Triscupid valve• Prevents backflow of blood to right atrium

Right ventricle• Right ventricle contracts and pumps deoxygenated

blood to the lungs via pulmonary artery

Semi-lunar valve• Prevents backflow to right ventricle

Superior vena cava

Inferior vena cava

Pulmonary artery

Right atrium

Triscupid valve

Right ventricle

Semi-lunar valve

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HeartLeft atrium• Receives oxygenated blood from the lungs via

pulmonary vein• Left atrium contracts, forces blood to enter left

ventricle

Biscupid valve• Prevents backflow of blood to left atrium

Left ventricle• Left ventricle contracts and pumps oxygenated

blood to the rest of the body via the aorta

Semi-lunar valve• Prevents backflow to left ventricle

Semi-lunar valve

Left atrium

Biscupid valve

Pulmonary vein

Aorta

Left ventricle

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Common exams questions

• Why does left ventricle has muscular wall than the right ventricle?– Left ventricle pump blood to the rest of the body, a greater distance

compared to right ventricle which pump blood into the lungs. Hence, it has a thicker muscle wall to produce strong force to pump blood over longer distance.

• Function of septum– Prevent mixing of oxygenated and deoxygenated blood

• Function of valve– To prevent backflow of blood and ensure blood flow in one direction

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Blood vessels

artery

blood flowing from the heart

heart

arteriesarteriolescapillaries

venulesveins

blood flowing back to the heart

vein

a capillary network links arteries and veins

Heart Artery Arteriole Capillary Venule Vein Heart

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Blood vesselsArtery Vein Capillary

Structure

• Thick and muscular wall

• Thin and less muscular wall

• Very thin wall(One-cell thick/one layer of cells)

• Elastic tissue • Not elastic • Not elastic

• Narrow lumen • Wide lumen • Very small lumen

• Valves absent • Valves present • Valves absent

Function

• Carries blood away from heart

• Carries blood towards the heart

• Allows exchange of materials between blood and body cells

• Transport oxygenated blood except pulmonary artery

• Transport deoxygenated blood except pulmonary vein

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Blood Flow

• Very fast flow• Highest pressure

• Slow and smooth flow

• Lowest pressure

• Slow and smooth flow

• Pressure is between artery and vein

Blood vesselsArtery Vein Capillary

- Thick muscular wall to withstand the pressure of blood exerted on the walls because artery receive blood directly from the heart and the blood is under high pressure.

- Elastic to enable the artery wall to stretch and recoil to push the blood forward

- Small lumen to maintain the high pressure

- Artery receive blood directly from the heart and the blood is under high pressure, hence no valve to impede the flow

- Thin outer wall and wide lumen as blood pressure is the lowest

- Valve ensure blood flows in one direction back to the heart because blood in veins is under low pressure and there is no direct force to push the blood forward.

- Thin wall of one layer of cells to allow higher rate of diffusion of substances

- Permeable walls to allow diffusion of substances

- Branching of capillaries to increase the surface area to volume ratio for diffusion of substances

- Slow blood flow gives more time for the diffusion of substances

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Coronary Heart Disease

• Coronary artery becomes hardened and narrow due to fatty deposits in the innermost lining of coronary artery.

• More resistance for blood to flow and the heart will overwork to pump blood.

• Blood clot of coronary artery will prevent blood flow to the muscle tissues in the heart. Blood and oxygen supply to the cardiac muscles is reduced.

• Heart muscles becomes deprived of oxygen and die. When too much heart muscles tissues is damaged, it leads to heart attack and even death.

(myocardial infarction= heart attack)(Occlusion = blood clot)(atherosclerosis: fatty deposits on the inner arterial walls)

Fatty deposit

Narrow artery

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Coronary Heart Disease

Causes Preventive measureHigh saturated fats diet- Increases the cholesterol level in the blood and build up fatty deposits.

Reduce intake of high saturated fats

Smoking-Nicotine increase risk of blood clotting in arteries-Carbon monoxide increases the risk of fatty deposits on the inner surface or arterial wall

Quit smoking

Lack of exercise- Result in unfit heart which slows down blood circulation and may allow fatty substances to deposit easily in the arteries

Exercise regularly

Stress Manage stress

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BloodParts Function Appearance

Plasma Transport dissolved substances (e.g blood cells, ions, soluble food substances, hormones, carbon dioxide, urea, vitamins, plasma proteins)

Pale yellow fluid

White blood cells

- Destroy harmful bacteria by phagocytosis

- Produce antibody

- Defend the body against infection

- Involve in tissue rejection after organ transplant

Platelets Fibrinogen converted into fibrin, causing blood clot

Red blood cells

- contain a red pigment called haemoglobin which binds to oxygen

- transport oxygen from the lungs to other parts of the body

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Blood clot

• When blood vessels are damaged, platelets release an enzyme that catalyses the conversion of the soluble protein fibrinogen to insoluble threads of fibrin

• Fibrin threads entangle blood cells which forms a clot

• Blood clot prevents entry of foreign particles through open wound or cuts

red blood cell fibrin thread

Red blood cells entangled in fibrin threads, forming a blood clot

red blood cell fibrin thread

Fibrin threads entangle red blood cells

clot

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