Chapter 8 - Transport In Mammals

Transport in Humans The Blood Circulatory System

Introduction • Confusion over the nature and role of the heart and blood in the body had existed for centuries • Pliny the Elder (AD 23-79 ) • Galen, a Greek physician (~ AD 150) • William Harvey (1578, England)

William Harvey • Most physicians of the time thought that lungs were responsible for moving the blood around throughout the body • Heart was a pump • Blood flow was unidirectional due to valves • Closed circulatory system

You will learn… • Structure and functions of – Circulatory system – Arteries, veins and capillaries – Heart

• • • •

Human blood cells Main blood vessels Lymphatic system Cause and prevention of coronary heart diseases

Why the need? • Diffusion alone not adequate • Need efficient transport system • Bring substances very close to body cells for easier diffusion. • 2 kinds: Blood system and lymphatic system

The Circle of Blood • Blood flows around the body (circulation) • Closed circulatory system – No whole blood escapes into the tissues or mixes with the tissue fluid – Consist of the blood vessels, heart and blood

• Main Functions: – Carry oxygen and food TO cells of body – Carry waste FROM cells to outside the body

No whole blood escapes into the tissues or mixes with the tissue fluid

Human Circulatory System Human Circulatory System

Blood

Blood Vessels

Heart

Human Circulatory System Blood

Plasma -55%

Blood Cells -45% -Red blood cells -White blood cells - Platelets

Centrifuged blood

Textbook pg 125 Can you identify the different blood cells? WBCs RBCs

Platelets

Main functions of blood 1. Transport • • • • •

Oxygen Food Hormones Waste products Heat

RBCs

Carried in plasma

2. Protection • •

Against foreign particles clotting

Plasma • Yellow fluid Constituents

Functions

Water (makes up 90%)

•Solvent •Transport medium •Maintains body temperature

Inorganic ions (Na+, K+, Ca2+, Mg2+, Fe2+)

•Maintains osmotic pressure •pH buffering (pH 7.4)

Soluble proteins (Albumen, antibodies, fibrinogen, globulins)

•Maintain normal blood pressure •Defence •Blood clotting •pH buffering

Red Blood Cells • • • •

aka Erythrocytes Formed in bone marrow Biconcave disc shaped cells; lack of nucleus Red colour due to haemoglobin – Protein that contains iron and readily combines with oxygen

Function of RBC Transport oxygen to cells – In the lungs, oxygen readily combines with iron in haemoglobin to form oxyhaemoglobin (bright red) – In body tissues, oxyhaemoglobin will unload its oxygen to become haemoglobin (dark red) again

Hb + 4 O2

High oxygen concentration Low oxygen concentration

Hb(O2)4

Acclimatization • People living at high altitudes usually have large number of RBCs. • Compensate for low oxygen concentration at high altitudes

White Blood Cells • • • •

aka leucocytes Colourless and larger than RBC Contain nucleus 2 main types: Lymphocytes and Phagocytes Produce antibodies

- Monoctyes, Polymorph - Engulf and ingest bacteria (phagocytosis)

Monocyte Lymphocyte

Polymorph

Phagocytosis • By phagocytes (Monocytes and Polymorphs) – Able to ingest and digest foreign particles – Cell “eating”

• http://www.sp.uconn.edu/~terry/Common/phago053.h

RBC • Biconcaved disc shape • No nucleus • Red colour (haemoglobin) • Diameter < 0.01mm • 5,000,000 in 1 mm3 • 700: 1 • Life span: 3-4 months

WBC • Round • Irregular nuclei (circular or lobed) • Colourless • • • •

4 times larger 5000-10,000 in 1 mm3 700:1 Life span: Few days (except memory cells)

Recap… What does a “closed circulatory system” mean? No whole blood escapes into the tissues or mixes with the tissue fluid

What are the main components of the circulatory system? Blood, blood vessels and heart

The plasma makes up how many percent of the blood? 55%

What is the function of haemoglobin? Transport oxygen in RBCs What are the 2 main types of WBCs called? Lymphocytes and Phagocytes

Antibodies • Pathogens contain antigens (chemicals) • These antigens stimulate lymphocytes to produce specific antibodies • Antibodies can: – kill bacteria – neutralize toxins – Cause bacteria to clump together (agglutination)

Specificity • Antibodies specific for bacteria A (eg. measles) will not attack bacteria B (eg. chicken pox)

Immunity • After an illness (e.g. chicken pox), antibodies against chicken pox persist and remain in the blood • Thus, the person is said to be immune to chickenpox

Memory cells • • • •

Special type of lymphocytes (WBCs) Formed after an infection / illness Remain in the blood stream for life Able to be activated very quickly if person encounters the same antigen again • Person is said to be immune to that infection/ illness

Vaccines • Dead or harmless form of the pathogen (BCG vaccine against tuberculosis) • Toxoid – the inactivated toxin from the pathogen (tetanus vaccines)

Organ transplant and tissue rejection • Replacement of diseased organ with healthy one • BUT new organ must not be rejected by body • (Body detects new organ as foreign particle  Defence system kicks in)

Prevention of tissue rejection • Donor and recipient must be close relatives • Suppress immune system – Use of drugs – X-ray of bone marrow to reduce blood production

Platelets • Tiny pieces of cytoplasm • Not true cells • Plays important role in blood clotting

Blood clotting • Clotting of blood seals the wound • Prevents excessive blood loss • Prevents foreign particles from entering blood

Textbook pg 127

Blood Clotting Injury/ Ruptured blood vessel Activates platelets to release

Thrombokinase (enzyme) catalyses

Prothrombin (inactive)

(Ca2+, Vit K)

Thrombin (active) catalyses

Fibrinogen (soluble)

Fibrin (insoluble) Forms meshwork

Blood Clot

Why doesn’t blood clot in undamaged blood vessels? • Anticlotting substance called heparin • Produced in liver • Thrombokinase able to neutralize the action of heparin

Summary What is the name of the specific structure that antibodies recognise? Antigens How can a person become immune to a disease like chicken pox? Antibodies specific for the chickenpox virus remain in the blood stream after the illness, and will be activated to attack the same virus again in future.

How can we prevent tissue rejection? Close relatives or Suppress immune system (Use of drugs / reduce blood production) Do platelets have a nucleus? No, they are not true cells What reaction does the enzyme thrombokinase catalyse in the blood clotting process? Prothrombin  thrombin

Blood Groups • Most common blood group systems: ABO and Rhesus Factor (Rh) • Difference due to presence or absence of certain antigens (surface of RBCs) and antibodies (in plasma) • Individuals have different types and combinations of these molecules. • The blood group you belong to depends on what you have inherited from your parents. • Not all blood groups are compatible with each other. Mixing incompatible blood groups leads to blood agglutination, which is dangerous for individuals.

ABO blood group • 4 blood groups: A, B, AB and O Blood group A - A antigens - B antibodies

Blood group B - B antigens - A antibodies

Blood group AB - A and B antigens - NO antibodies

Blood group O - NO antigens - A and B antibodies

Rh factor • Rh is another antigen on RBC’s surface • Rh+ (people who have this factor) or Rh-

Parent  Child • Must a child’s blood group always be the same as one, or both, of their parent’s blood group? • Punnett square

Agglutination of incompatible blood groups Blood Type A

Antigen Antibody A

B

Can receive A, O

Can donate A, AB

B

B

A

B, O

B, AB

AB

A and B

None

All

AB

O

none

A and B

O

all

BG B

BG A Blood Type A

BG B

BG A Blood Type AB

Blood Type B

Blood Type O

BG AB

BG O Blood Type A

BG AB

BG O Blood Type AB

Blood Type B

Blood Type O

• Blood typing game: http://nobelprize .org/medicine/educational/landsteiner/

Human Circulatory System Human Circulatory System

Blood

Blood Vessels

Heart

Blood Vessels Blood Vessels

Arteries and aterioles

Capillaries

Veins and venules

Arteries & Aterioles • Vessels carrying blood AWAY from the heart • Aterioles are smaller vessels that join the larger arteries to the capillaries Elastic layer Connective Tissue Endothelium Thick smooth muscle Lumen

Capillaries • Small vessels connecting arteries and veins • One cell thick • Site where exchange takes place – Gases, nutrients and waste products – Between blood in capillaries and interstitial fluid – Mainly by diffusion Basement membrane

Endothelium

Veins and Venules • Vessels carrying blood back TOWARDS the heart • Venules are the smallest veins, joining the capillaries to the larger veins • Valves: for unidirectional blood flow • Vericose veins Connective Tissue

Endothelium

Thin smooth muscle

Lumen

Elastic layer Thick smooth muscle

Elastic layer Thin smooth muscle

Veins and Venules

Capillaries

Arteries and Arterioles

Function : Carry blood Function is to carry towards from heart blood from tissues to the heart

Function is to allow exchange of materials between the blood and the tissues

Function : Carry blood Function is to carry blood away from heart from the heart to the tissues

Thin walls, mainly collagen, since blood at low pressure

Very thin, permeable Thick walls with smooth walls, only one cell thick to elastic layers to resist high allow exchange of pressure and muscle layer materials to aid pumping

Veins and Venules

Capillaries

Arteries and Arterioles

Large lumen to reduce resistance to flow.

Very small lumen. Blood cells must distort to pass through.

Small lumen

Many valves to prevent back-flow

No valves

No valves (except in heart)

Blood at low pressure

Blood pressure falls in capillaries.

Blood at high pressure

Blood usually deoxygenated (except in pulmonary vein)

Blood changes from oxygenated to deoxygenated (except in lungs)

Blood usually oxygenated (except in pulmonary artery)

Blood on the wall

What type of blood vessel was severed?

Human Circulatory System Human Circulatory System

Blood

Blood Vessels

Heart

The Human Heart • Made up of cardiac muscles • About the size of a clenched fist • Lies between the lungs with its apex extending slightly towards the left apex

• Pericardium (doublewalled sac) surrounds the heart • The space between the double walled pericardium is filled with pericardial fluid. • Acts as a lubricant – reduces friction when heart beats

The heart chambers

Atrium

Ventricle

Atrium

Ventricle

LEFT Atrium

RIGHT Atrium

LEFT Ventricle RIGHT Ventricle

Part of heart Atria: Plural Atrium: Singular Ventricles

Function •Receive blood coming into heart •Pumps blood into ventricles •Pump blood out of the heart

Note: Atria have thinner walls than ventricles because they only need to pump blood to the ventricles below. Ventricles have thicker walls because they need to pump blood to the rest of the body

The heart chambers

Heart Valves Median Septum

Valves Valves Median Septum

Part of heart Median septum

Valves:

Function •Muscular wall that divides the heart into left and right side •Blood from the 2 halves never mix Prevent backflow of blood

1. Tricuspid

Found between right atrium and ventricle

2. Bicuspid

Found between left atrium and ventricle

3. Semilunar

Found between ventricles and pulmonary artery and aorta

Textbook Pg 133, Fig 8.10 (b)

Valves in the Heart Tricuspid Valve

Chordae Tendineae

Semilunar Valves Bicuspid Valve

Chordae Tendineae • Cords / tendons that are attached to the tricuspid and bicuspid valves • Help to prevent the valves from being turned inside out

Walls of Heart • Thinner walls on right side • Thicker walls on left side • Why? Left side pumps oxygenated blood (higher pressure) to whole body Need stronger and bigger muscles

Double Circulation • The heart pumps oxygenated blood to all organs • Deoxygenated blood is returned to heart • This deoxygenated blood must be sent to the lungs to replenish its oxygen content • Once oxygenated, the blood returns to the heart again to be pumped to the rest of the body • This is known as double circulation (blood need to pass by the heart twice in one cycle)

Double Circulation • Pulmonary Circulation – Transports blood to lungs and back to heart – Low pressure

• Systemic Circulation – Pumps blood to rest of body and back to heart – Higher pressure

Double Circulation

Rest of Body

Blood vessels to and from Heart Aortic arch

Superior Vena Cava

Pulmonary artery Pulmonary Vein

Inferior Vena Cava

Direction of blood flow inside heart

Double Circulation Left Ventricle

aorta

Body

Rt Atrium Tricuspid valves

Vena cava

Right Atrium

Rt Ventricle Pulmonary artery Lung Semilunar valves

Rest of Body

Lung Pulmonary vein

Lt Atrium Bicuspid Valves Lt Ventricle

Summary… Name the 4 chambers of the human heart Right and left atria; right and left ventricles What are the roles of the semilunar valves in the heart? To prevent backflow of blood into the ventricles What is the function of the median septum? To separate the left side from the right side of the heart (prevent the mixing of oxygenated and deoxygenated blood)

Why is the human circulatory system described as a double circulatory system? Blood flows from heart to rest of body back to heart; then from heart to lungs and back to the heart again. What is the main difference between the hepatic portal vein and other veins in the body? The hepatic portal vein transport blood from organ to organ

Main Blood Vessels

Hepatic portal vein

Hepatic portal vein • Transport blood filled with nutrients from stomach & intestine to liver • The only vein that joins organ to organ

Mode of Action of the Heart (i.e. How the heart beats) • The chambers of the heart contract and relax in pairs • When both atria contract; ventricles are relaxed • When ventricles contract, atria are relaxed

Heartbeat: http://www.psionica.co.uk/biology/KS4Biology/heartbt.htm

Heartbeat (Cardiac Cycle) One heartbeat (a cardiac cycle) consists of two parts: 3. Systole (ventricular contraction) 4. Diastole (ventricular relaxation)

Systole (contraction) – – – –

Ventricles contract Blood is forced into the pulmonary artery and aorta Tricuspid and bicuspid valves are closed Blood pressure normally rises to120 mmHg

Diastole (relaxation) – Ventricles are relaxed; tricuspid and bicuspid valves open – Blood flows from vena cava and pulmonary veins into atria – Blood then flows from atria into ventricles – Both atria contract at the end of diastole, forcing any remaining blood into the corresponding ventricles. – Semilunar valves closed to prevent blood from entering the pulmonary artery and aorta. – Blood pressure falls to around 80 mmHg

Heart sounds • During systole, “Lup” sound is caused by backflow of blood against closed tricuspid and bicuspid valves • During diastole, “Dup” sound is caused by backflow of blood against closed semilunar valves • Rhythmic “Lup-Dup” sounds results • Stethoscope can be used to hear the heart beat

Control of Heartbeat • The heart has a natural rhythmic contraction of its own • Can be also controlled by some nerves from the brain to increase or decrease the number of heart beats when necessary.

Pacemaker • Group of specialized cells found at top right atrium • Pacemaker initiates heart beat • Pacemaker is controlled by nerves from the brain • To speed up or slow down heart rate when necessary

http://www.phschool.com/science/biology_place/biocoach/cardio1/electrical.html

Artificial Pacemaker • Some heart diseases can cause the heart to beat irregularly • Can be corrected by using an artificial (manmade) pacemaker • Doctors will implant this small electronic device near the patient’s heart • It will produce regular pulses of electricity which stimulates the heart to contract and relax at the right rate.

Pulse Rate • The number of times the heart beats in one minute • The resting heart beats approximately 60 to 100 times per minute • Pulse rate increases during exercise, and when one is feeling stressed, nervous, angry or excited.

Pulse Rate How many times does your heart beat in : • One minute? 70 • One day?

100,800

• One week?

705,600

• One month? 21,168,000 • One year?

254,016,000

Pulse Rate of… • Foetus:

140-150 beats/min

• Newborn baby: • 3 year old:

130-140

95-100

• 10 year old:

84

• 25 year old:

72

• 50 year old:

76

Blood Pressure • Blood pressure is around 120/80 mmHg • Blood pressure is the force of the blood pushing against the walls of the arteries each time the heart beats. • Blood pressure is at its highest during systole. • Blood pressure is lowest when the heart is at rest, between beats (diastole) http://www.phschool.com/science/biology_place/labbench/lab10/intro.html

High Blood Pressure • Blood pressure of 140/90 or higher is considered high blood pressure Who is at risk? – middle-aged and elderly people – obese people – heavy drinker – Inherited form parents

Key Words • • • • •

Coronary arteries Arteriosclerosis Atherosclerosis Cholesterol Thrombosis

Cardiovascular Diseases • Diseases of the heart and blood: – – – –

Coronary heart disease Hypertension (high BP) Arteriosclerosis (hardening of arteries) Atherosclerosis (narrowing of arteries)

Coronary arteries • A lot of blood pass through the heart all the time • But heart is NOT nourished by the blood pass through it • Coronary arteries supply oxygen and nutrients to the heart

Coronary Heart Diseases • Occur when coronary arteries become blocked • Result: Oxygen and nutrients cannot be supplied to the heart

Recap… What is the main difference between the hepatic portal vein and other veins in the body? The hepatic portal vein transport blood from organ to organ What are the 2 parts of a cardiac cycle? Systole and diastole What causes the heart sounds as the heart beats? Backflow of blood against the valves

Recap… What is the pacemaker? Group of specialized cells found at top right atrium that regulates heartbeat. What is the pulse rate? The number of times the heart beats in one minute When is blood pressure the highest in a cardiac cycle? During systole (120 mmHg)

Steps in coronary heart disease •

•

Coronary arteries become blocked when lipids (fat and cholesterol) carried by the blood get deposited on the walls of the arteries, thus making them narrower This is called atherosclerosis

• • • •

Calcium salts then cover the lipids to form a fibrous net called atheroma Blood clots (thrombus) may also form Coronary occlusion occurs when the artery is fully blocked and the supply of blood to the heart is stopped A heart attack results, as part of the heart dies from the lack of oxygen

Causes of Heart Diseases • • • • •

Fatty diet (high in sodium, cholesterol and saturated fats) Lack of exercise Obesity Smoking Stress

Tissue Fluid • NOT blood or plasma • But similar to plasma, with fewer proteins • Escapes from capillaries during fluid exchange • Also forms a thin film over all body cells

Fluid Exchange • Take place in capillaries • But blood has a higher osmotic potential than the surrounding tissue fluid • How would nutrients and water flow out of capillaries??

Fluid Exchange in Tissues Arterial end

Venous end

• Exchange of substances between blood and body cells take place through the capillaries • Blood pressure higher at arterial end • This pressure forces water and nutrients out of capillaries into intercellular spaces

Water Nutrients

Arterial end

Tissue Fluid

Water Waste

Venous end

• Body cells take in nutrients from intercellular spaces • Blood pressure is lower at venous end, water and waste products from cells enter capillaries • Fluid in intercellular spaces is called tissue fluid

Oedema • Occurs when tissue fluid is formed faster than it can be drained away • Accumulate in tissues and cause them to swell • Occurs in elderly people or pregnant women

Lymphatic System • Not all the tissue fluid returns to the capillaries • Some will enter blind–ending vessels called lymphatics as lymph fluid • Lymph fluid – pale yellow liquid – Similar to plasma except for the absence of plasma proteins

Lymphatic System • Lymphatic vessels: – Transport excess tissue fluid back into blood stream

• Lymphatic Organs: – Lymph node, tonsils, thymus and spleen

Lymphatic Vessels • Blind-ended • Compression of skeletal muscles aids in unidirectional flow • Valves present • Small vessels join up to form 2 larger ones; right lymphatic duct and thoracic duct • Both ducts empty their contents back into the blood stream via the subclavian veins

Lymph Nodes • Swellings at certain points in the lymphatic vessels • Stores lymphocytes and phagocytes (WBCs) • Releases them into the blood stream • Thus, lymph nodes play an important role in body’s defence

Lymphatic Organs • Spleen: – Found on the left side of the abdomen – Removes worn-out RBCs and produces lymphocytes and antibodies

• Thymus: – Found between the collarbone and above the heart – Produces and stores lymphocytes

Blood circulatory system

Heart

Blood Vessels

Atria and Ventricles

Arteries Arterioles Capillaries Venules Veins Lymphatic system

Blood Plasma

Blood Cells RBC WBC Platelets

Functions (2) 1. RBCs catalyse carbon dioxide reaction - RBCs pick up CO2 from tissues - CO2 then combines with water to form carbonic acid (Enzyme in RBC) H2CO3 CO2 + H2O - Carbonic acid then ionises to form hydrogen ions and hydrogen carbonate ions H2CO3

H+ + HCO3-

Functions (2) -About 70% of the ions then leave the RBC and remain in the plasma -CO2 is released when the blood reaches the lungs H+ + HCO3H2CO3

H2CO3 CO2 + H2O

BACK

Valves • • • •

Found in the heart and veins Folds of the inner walls of heart and veins Shaped like half moons, so called semilunar valves Function: Prevent backflow of blood.

Textbook pg 130

NEXT

Unidirectional flow of blood

BACK

Vericose Veins

• When the valves in the veins near the surface of the skin fail to close properly • Allow blood to accumulate in the veins • Causes vein to bulge (swollen appearance) NEXT

Valves fail to close properly

BACK

Superior Vena Cava • Brings deoxygenated blood from head and arms to right atrium of heart

Inferior Vena Cava • Brings blood from bottom part of body into right atrium of heart

Pulmonary arteries • Brings deoxygenated blood from right ventricle to lungs to uptake oxygen • The ONLY arteries that transport deoxygenated blood • 2 pulmonary arteries – one to each lung

Pulmonary Vein • Transports oxygenated blood from the lungs back to the left atrium of heart • The ONLY vein that carries oxygenated blood • 2 pulmonary veins – one from each lung

Aorta • Transport oxygenated blood from left ventricle to rest of body • Forms the characteristic aortic arch • Largest artery of the body