This lecture was presented to nursing students undertaking their bridging course at Nursing Training Institute of Technology (NTIT), Eenhana, Campus, Ohangwena Region, Namibia. It discusses the transport system in humans, touching on topics like the heart, blood vessels, lymphatic system, and immunity in Biology. The resources used were the Namibian Namcol new curriculum for grade 10-11 ordinary level biology text book. It was presented by myself, Dr. Nghitukuhamba Tangi Elikana Kalipi MBChB, Bsc HB.

1. NURSING TRAINING INSTITUTE OF
TECHNOLOGY (NTIT), EENHANA
CAMPUS
BIOLOGY
UNIT 7: TRANSPORTATION
SECTION 2: TRANSPORT IN HUMANS
DR. NGHITUKUHAMBA T.E KALIPI
- BACHELOR OF SCIENCE IN HUMAN BIOLOGY (Bsc HB)
- BACHELOR OF MEDICINE AND BACHELOR OF SURGERY (MBChB)

2. LESSON OBJECTIVES
By the end of the lesson a student should be able to describe:
➢ How substances/materials can be transported from one part of the body to
another part
➢ The heart and its components
➢ The heartbeat
➢ Structure of blood vessels
➢ The double circulatory system
➢ The lymphatic system
➢ Blood and its components
➢ Defense against diseases
➢ Transplant rejection
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3. 1. Transport of substances and materials
 The human circulatory system is said to have a double circulation, this is due
to the fact that blood from the rest of the body goes to the heart, then to the
lungs and back to the heart again before traveling to the rest of the body,
doubling its circulation within the heart.
 The heart is the pump of the body.
 Large organisms have complex systems far removed from where food is
absorbed and oxygen is needed.
 Toxic waste products (such as Urea, Nitrogen and Carbon Dioxide) produced
by cells must also be removed from the cells and excreted through various
organs.
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4. 2. The Heart
 The size of a human heart is about the size of a clenched fist.
 It lies between the lungs (in the middle mediastinum).
Layers of the heart:
1. The pericardium
This is the outer layer encapsulating the heart, it is made of a tough inelastic
membrane which protects the heart from overexpansion. A fluid termed
pericardial fluid is secreted between the pericardial layer and the heart that
serves to lubricate the heart and reduce friction.
2. The myocardium
This is the middle layer of the heart composed of cardiac muscle, a special type
of muscle only found in the heart. This contracts rhythmically without tiring
throughout your lifetime.
3. The endocardium
This is the innermost layer of the heart made up of endothelium and
subendothelial connective tissue.
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5. The Heart continued…
 The heart is made up of two halves separated by a septum, this leads to
formation of four heart chambers;
Chambers of the heart
Right side;
- The upper right chamber is the right atrium
- The lower right chamber is the right ventricle
Left side;
- The upper left chamber is the left atrium
- The lower left chamber is the left ventricle
 The right and left atrium are thin-walled and receive blood from the body
and lungs through the veins.
 The right and left ventricle thick muscular walls and pump blood to the lungs
and rest of the body through arteries.
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6. The Heart continued…
 The septum separates deoxygenated blood on the right side of the
heart from oxygenated blood on the left side of the heart.
Flow of blood in the heart
1. Deoxygenated blood flows to the heart via the superior vena cava
(blood from the head and arms) and inferior vena cava (blood from
the rest of the body) into the right atrium
2. Blood from the right atrium flows through the tricuspid valve into the
right ventricle, the right ventricle then contracts and pushes
deoxygenated blood through the pulmonary valve into the pulmonary
artery and into the lungs.
3. Oxygenated blood returns through the pulmonary veins into the left
atrium, it passes through the biscupid (mitral) valve into the left
ventricle.
4. The left ventricle then contracts and pushes oxygenated blood
through the aortic valve into the aorta and to the rest of the body.
The left ventricle is thicker than the right ventricle( about 3 times
the size).
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7. The Heart continued…
The heart valves
 There are two types of heart valves, those found between the atrium and
ventricle (inflowing part of the heart) are called atrioventricular valves, and
those between the ventricles and pulmonary artery and aorta (the outflowing part
of the heart) are called semilunar valves. Valves prevent the back flow of blood.
Types of heart valves
1. Two atrioventricular valves, mainly;
- Tricuspid valve (on the right side of the heart)
- Biscupid/mitral valve (on the left side of the heart)
These valves prevent back flow of blood into the atria when the
ventricles contract.
2. Two semilunar valves, mainly;
- The pulmonary valve (on the right side of the heart)
- The aortic valve (on the left side of the heart)
These valves prevent back flow of blood into the ventricles when
ventricles relax.
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8. The Heart continued…
The heart beat
 The cardiac muscle contracts and relaxes at about ~70 beats/minute (the
normal range is between 60 beats/minute to 100 beats/minute).
 One complete sequence of contraction and relaxation in called a cardiac cycle.
 The cardiac cycle is dived into;
1. General diastole; when the muscles of the atria and ventricles are relaxed.
- This consists of atrial diastole and ventricular diastole.
2. Atrial systole; when the muscles of the atria contract.
3. Ventricular systole; when the muscles of the ventricles contract.
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9. The Heart continued…
Effect of exercise of heartbeat
 Heartbeat changes according to the needs of the body.
 During exercise, the brain sends a signal through the nerves to specialized cardiac
muscle cells in the right atrium called the pacemaker cells, this causes the heart
to beat faster to meet the extra demand for oxygen.
 The pulse rate is a measure of heartbeat, this is produced by arteries stretching
and snapping back as blood is pumped through them causing a pressure wave. You
can feel this wave as your pulse at points where arteries are close to the skin such
as your radial pulse, femoral pulse, carotid pulse, etc.
 The increase in heartbeat increases the cardiac output [ Cardiac Output = Heart
rate x Stroke Volume, written as CO = HR x SV ]. This causes more blood to be
pumped to the rest of the body supplying the required amount of oxygen.
 Thinking about exercising can also increase the stroke volume and heart rate.
 An athlete, such as a sprinter can have a heartrate as high as 200 beats/minute,
and the heart rate remains high for sometime after exercise.
 Skeletal muscles receive most of the body’s blood during exercise diverting blood
away from certain areas such as the intestines.
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10. The Heart continued…
Effect of exercise of heartbeat
 Oxygen deficit is the difference between the amount of oxygen consumed and
the amount of oxygen that would have been consumed if a steady state had been
reached from the start.
 Oxygen debt is the amount of oxygen consumed during the recovery period
(recovery oxygen consumption). This is dependent of exercise intensity, the
greater the exercise, the greater the oxygen debt. Oxygen debt serves to
replenish energy stores utilized during exercise, such as ATP/PC stores, remove
lactic acid by converting it to lactate and then to glucose in the liver.
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11. The Heart continued…
Importance of regular exercise;
 It improves ventilation.
 Respiratory muscles become stronger.
 Increases blood supply to the lungs.
 Alveoli function is improved.
 Increases blood volume and total number of red blood cells.
 Heart becomes enlarged and resting pulse is lowered, improving the oxygen
transport system.
 Increases concentration of respiratory enzymes and number of mitochondria
therefore improving cellular energy generation and energy usage.
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12. 3. Blood Vessels
There are 3 main types of blood vessels
1. Arteries; transporting blood away from the heart.
2. Veins; transporting blood to the heart.
3. Capillaries; connecting the arterial and venous systems and is also the site of
exchange between the blood and body tissues.
 After arteries leave the heart, they divide into smaller vessels called arterioles,
these lead into capillaries, which then join venules, these go to join veins which
then return blood to the heart.
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13. Blood Vessels continued…
Arteries
 Blood travels in arteries in spurts called pulses. Blood is forced out of the
ventricles of the heart under high pressure. Each spurt represents the ventricle
contracting and relaxing.
 Arteries have strong elastic walls that can withstand this high pressure so that
blood flows smoothly. Arteries have narrower lumens.
Arteries carrying deoxygenated blood
1. Pulmonary artery
2. Umbilical artery
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14. Blood Vessels continued…
Veins
 Blood travels in veins slowly and smoothly, at much lower pressures than in
arteries. This blood is returned to the atria of the heart.
 Veins have thinner elastic walls than arteries, and they have wider lumens. This
ensures ease of flow of blood.
 Blood in veins is kept moving by the contraction of muscles surrounding the veins,
such as muscles in the legs when walking squeeze large veins in the legs pushing
blood back up to the heart.
 Veins have valves that ensure unidirectional flow of blood. Arteries do not have
valves except in the aorta and pulmonary arteries which have valves (the
semilunar valves found in the heart).
Veins carrying oxygenated blood are;
1. Pulmonary veins
2. Umbilical veins
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15. Blood Vessels continued…
Capillaries
 These are small blood vessels that reach every part of the body.
 Capillaries walls consist of a single layer of cells so that oxygen, nutrients, and
waste products such as carbon dioxide can diffuse in and out of capillaries.
Capillaries are adapted to allow the effective exchange of substances
between the blood and the body tissues. Blood reaching capillary beds
is at high pressure forcing blood plasma out into the tissues becoming
tissue fluid. As plasma moves from capillary beds towards the veins,
pressure drops and this stops squeezing out of plasma. Tissue fluid acts
as a bridge in the diffusion of chemicals between capillaries and body cells.
Oxygen and glucose move into the tissues, and carbon dioxide and urea
diffuse back into capillaries from body cells.
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16. 4. The Double Circulatory System
 The double circulatory system means that blood flows through the heart twice in
order to make one complete circuit around the body.
 The pulmonary circulation transports blood between the heart and the lungs.
 The systemic circulation transports blood between the heart and all parts of the body.
• Blood moves from veins into the right side of the heart
and goes to the lungs. From the lungs it goes to the
left side of the heart which is then pumped to the
rest of the body.
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17. The Double Circulatory System continued..
 Blood moves from high-pressure areas to low pressure-areas down pressure gradients.
 Pressure gradients are produced in three ways;
1. By pumping action of the heart.
2. Contractions of skeletal muscles squeezing blood along veins.
3. Inspiratory movement of the thorax (chest) reduces the pressure inside the thoracic
cavity, which draws blood back to the heart.
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18. Oxygenated and deoxygenated blood
 Blood in the left side of the heart is oxygenated blood, that has come from the
lungs. The oxygen was taken up by capillaries surrounding the alveoli in the lungs.
The heart pumps this oxygenated blood to the rest of the body, the oxygen is then
used up by the body cells for respiration.
 After oxygen is used up by the cells, this blood becomes deoxygenated blood, and it
is transported to the right side of the heart. This deoxygenated blood is pumped to
the lungs, where it becomes oxygenated again.
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19. 5. The coronary arteries
 The cardiac muscle has its own blood supply, which is provided by the coronary
arteries. These arteries are visible on the surface of the cardiac muscle of the heart.
 They maintain a constant supply of oxygen and glucose to the heart muscles.
 If these vessels become blocked by blood clots, or fatty deposits it causes coronary
artery disease, it results in a reduction of oxygen and nutrient supply to the heart
muscles, causing what is called a heart attack (myocardial infarction).
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20. The coronary arteries continued…
Causes of heart attack (Risk factors)
• A genetic predisposition.
• A high cholesterol diet (causing atherosclerosis).
• Being overweight (Obesity).
• Stress.
• Smoking cigarettes.
• Lack of physical exercise.
Preventive measures of heart attack
• Diet modification (eat healthier, reduce on high fat diets, such as red meat, butter
and eggs)
• Weight loss.
• Stop smoking cigarettes.
• Exercise regularly.
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21. The coronary arteries continued…
Treatment of coronary artery disease
• Aspirin; This drug is part of a group called antiplatelet medication, it essentially
exerts its effects through blood thinning by inhibiting platelet aggregation and
preventing blood clot formation, therefore prevent obstruction of coronary arteries.
• Angioplasty; This is a procedure used to remove obstruction and open up blocked
coronary arteries as a result of coronary artery disease.
• Stent placement; This involves insertion of a wire-mesh tube into coronary arteries,
and it is often done during the procedure of angioplasty. This wire-mesh compresses
the fatty deposits against the arterial walls relieving the obstruction.
• Coronary artery bypass surgery; A procedure done during open heart surgery
whereby a surgeon creates a graft by using a blood vessel from another part of the
body to bypass the site of obstructed coronary arteries.
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22. 6. The Lymphatic System
Function of the lymphatic system;
1. Collect and return tissue fluid back to the systemic circulation.
2. Produce lymphocytes and antibodies to defend the body against diseases.
 Tissue fluid is formed when blood plasma leaks out of the blood capillaries through
the very thin walls of the capillaries. This tissue fluid drains into lymphatic
capillaries which are part of the lymphatic system.
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23. The Lymphatic System continued…
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 When tissue fluid enters the lymphatic capillaries, it is called lymph. This
lymph then flows through several lymph nodes that contain a large number of
lymphocytes, which destroy bacteria and toxins to protect the body against
disease.
 The lymphatic vessels eventually join to form two large lymph ducts, mainly
the right lymphatic duct (which drains the right upper thorax, right upper
limb, and right side of the head and neck) and the thoracic duct which drains
the rest of the body.
 The lymphatic system does not have a pump like the circulatory system, the
flow of lymph through lymphatic ducts depends on the contraction of
surrounding muscles. Lymphatic ducts have valves that ensure unidirectional
flow of lymph.
See diagram on next page for parts of the lymphatic system

24. The Lymphatic System continued…
Parts of the lymphatic system
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25. 7. Blood
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Blood is made up of different types of cells, which are floating in a liquid called
plasma. Plasma is a medium for transporting materials in blood.
Function of blood;
1. Transport
2. Defense against disease
Cells found in blood;
1. Red blood cells
2. White blood cells
3. Platelets (cell fragments)

26. Blood continued…
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Red Blood Cells
 Also called erythrocytes.
 These are biconcave in shape, without a nucleus.
 They transport oxygen from the lungs to body tissues.
 Red blood cells contain haemoglobin, which carries oxygen. This is a type of protein
containing iron. When haemoglobin combines with oxygen in the lungs, it forms
oxyhaemoglobin, this then releases oxygen as blood flows through the tissues.
Blood rich in oxyhaemoglobin is called oxygenated blood.
Blood with little oxyhaemoglobin is called deoxygenated blood.
Special features (adaptations) of red blood cells
1. No nucleus, therefore more area inside the cell for haemoglobin, hence more oxygen.
2. Biconcave shape, gives a large surface area for diffusion.
3. Thin cell membrane, oxygen and carbon dioxide can easily diffuse in and out rapidly.

27. Blood continued…
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White Blood Cells
 These are also called leucocytes.
 They are produced in the bone marrow and lymph nodes.
 Their function is defense of the body against diseases.
 There are several types of white blood cells, classified as;
Granulocytes; Neutrophils (with bilobed nucleus), eosinophils, and basophils.
Agranulocytes; Monocytes, and lymphocytes (with large nucleus).
 White blood cells can move out of blood capillaries into body tissues, a process called
diapedesis.

28. Blood continued…
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Platelets (cell fragments)
 These are also called thrombocytes.
 They are small pieces of cells that float in the blood plasma.
 They play an essential role in blood clotting when a blood vessel is damaged.
Importance of blood clotting;
1. It helps to prevent further blood loss.
2. Prevents disease causing microorganisms (pathogens) such as bacteria, viruses,
parasites, and fungi from entering the body.
Blood clotting;
 Platelets that are in the blood collect at the site of tissue damage
and release an enzyme that sets of a chain reaction in the blood
converting fibrinogen (a soluble protein) to fibrin threads network (insoluble).
This network of fibrin threads trap red blood cells forming a blood clot, which
later becomes a hard scab.

29. Blood continued…
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Diagram of the blood clotting process

30. Blood continued…
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Plasma
 Makes up 55% of blood.
 Its main function is transport of materials
 Serum differs from plasma, in serum there are no clotting factors (lacks fibrinogen).
Composition of plasma
~90 – 92% is made up of water.
~7% is made up of proteins (Albumin 58%, globulin 37% (antibodies), fibrinogen 4%,
regulatory proteins 1%).
~1% is made up of dissolved solutes (oxygen, glucose, electrolytes, hormones, amino
acids, and waste products such as urea and carbon dioxide).

31. 8. Defense against diseases
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Pathogen (disease-causing microorganisms) such as bacteria, viruses, fungi, and parasites
can enter the body through a cut in the skin and cause infection. White blood cells
protect the body against these types of infections.
Types of white blood cells;
 Neutrophils (have bilobed nucleus).
They squeeze out of blood capillaries into the tissue at the site of infection and
destroy harmful bacteria and viruses through a process called phagocytosis. This is a
general immune response.
 Lymphocytes (have large nucleus).
They produce antibodies against disease-causing microorganisms by recognizing
foreign antigens (molecules that trigger an immune response).
This is a specific immune response.
Other types of white blood cells;
Monocytes, eosinophils, basophils.

32. Defense against diseases continued…
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The immune response
 The white blood cells recognize pathogens that enter the body as foreign, and attack them.
This process that results in the production of disease-fighting cells and antibodies is called
an immune response.
The body’s defense mechanisms;
1. Hair and mucus in the nose; traps inhaled particles.
2. Respiratory tract cells; has cells that secretes mucus to trap particles and pathogens.
3. Respiratory tract cilia; hair-like projections that beat to sweep mucus up to the pharynx to
be swallowed.
4. Skin; has a tough outer layer that serves as a mechanical barrier and is constantly renewed.
5. Hydrochloric acid in the stomach; destroys pathogens.
6. Enzymes in the intestines; destroy pathogens.
7. White blood cells recognize and destroy pathogens via engulfment or antibody production.

33. Defense against diseases continued…
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The immune response
 White blood cells recognize bacteria and viruses by their surface molecules called antigens,
these are proteins or polysaccharides, and are very different from the body’s own surface
molecules, they recognized as foreign or non-self molecules/antigens.
What is phagocytosis?
It is an immune response that involves recognizing, engulfing and digesting pathogens. This can
occur at the site of infection, or within the lymph nodes. Neutrophils are one type of many
cells that destroy pathogens by phagocytosis. This is an innate/general immune response.

34. Defense against diseases continued…
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The process of phagocytosis
• Receptor proteins on the surface on neutrophil cell membrane bind to the
surface of the pathogen.
• The neutrophil membrane then flows around and encloses and engulf the
pathogen in a vacuole, called a phagosome.
• The vacuole gets pinched off inside the neutrophil.
• Enzymes (hydrolytic enzymes) in a lysozyme found inside the neutrophil move
towards and fuse with the vacuole forming a phagolysozyme, these enzymes
then digest the ingested particles and neutralize them.

35. Defense against diseases continued…
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Antibodies
 These are globular proteins called immunoglobulins that are carried in blood.
 They combine with antigens to form antigen-antibody complexes, this makes the
invading pathogen harmless.
 Antibodies have a Y shape, each arm of the Y shape has a receptor site that is
specific to one type of antigen.
 Antibodies are produced by lymphocytes within the lymph nodes in response to a
foreign antigen. This antibodies will be specific to that particular antigen.
 Types of lymphocytes are; B-lymphocytes, and T-lymphocytes.
B-lymphocytes produce plasma cells that then produce antibodies and release them
into the blood stream. T-lymphocytes produce antibodies on its surface membrane.

36. 9. Immunity
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Lymphocytes continue producing antibodies even years after you last had an infection. This
gives you protection against the disease caused by that pathogen. This happens because of
memory cells, these are cells remember that specific antigens and trigger an immune response
if you are to be exposed to it again, this response is faster than the first response to that
pathogen.
Types of immunity
 Active immunity
Further classified as;
Natural active immunity; the body produces antibodies against an active infection,
such as measles or chicken-pox. This type of immunity is long lasting.
Artificial active immunity; The body produces antibodies in response to a vaccine against
a certain disease. This type of immunity is long lasting.
Several types of vaccines exist; such as BCG for TB, tetanus toxoid, hepatitis B vaccine,
coronavirus vaccine, pneumococcal vaccine, polio vaccine, HPV vaccine etc.

37. Immunity continued…
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 Passive immunity
A person receives ready-made antibodies.
Further classified as;
Natural passive immunity; whereby the mother transfers immunoglobulins/antibodies to
the unborn child via the placenta (IgG antibodies) or to a neonate through breastmilk (IgA
antibodies). This type of immunity is short lasting, because it does not involve memory cells.
These antibodies protect the baby until his/her immune system matures.
Artificial passive immunity; This is through injection of ready-made antibodies that were
harvested from a mammal. An example of these type of antibodies is the snake venom. This
type of immunity is also short lasting.

38. 10. Transplant rejection
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 This is an immune response that results from recognition of a transplanted organ as
foreign by the lymphocytes of the recipient, in the same way lymphocytes recognize
pathogens.
 People on transplant lists are carefully matched before such operations.
 This type of immune reaction is potentially dangerous and can lead to death of the
recipient.
 These people receive drugs called immunosuppressants to downregulate their
immune responses, such drugs include tacrolimus, mycophenolate mofetil,
prednisone, azathioprine and many more.

39. THE END
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40. References
1. Nakaziko, A (2018). NAMCOL, Ordinary Level, Grades 10 – 11, Biology Learner’s
Book, New Curriculum. 1st Edition, pg 221-246. Cambridge University Press.
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