Download Transport in Humans

Transport in Humans
Pure Biology Chapter 8
Coloured scanning electron micrograph (SEM) of a resin cast
of blood vessels supplying the small intestine.
Learning Objectives
• State the functions of the following components of blood:
plasma, red blood cells, white blood cells, platelets
• List the different blood groups and all possible combinations
for the donor and recipient in blood transfusions.
• Relate the structure of arteries, veins and capillaries to their
functions.
• Identify the main blood vessels to and from the heart, lungs,
liver and kidneys.
• Describe the structure and function of the heart in terms of
muscular contraction and the working of valves.
• Outline the cardiac cycle in terms of what happens during
systole and diastole.
Learning Objectives
• Describe the transfer of substances between capillaries and
tissue fluid.
• Describe coronary heart disease in terms of the occlusion of
coronary arteries.
• List the possible causes of coronary heart disease.
• State the possible preventive measures for coronary heart
disease.
Why the need for a transport
system??
• In simple unicellular organisms, oxygen and
nutrients can diffuse through the cell surface
membrane and reach all parts of the cell easily.
Why the need for a transport
system??
• In complex multicellular organisms, simple diffusion
cannot bring enough oxygen and food materials to
the cells situated deep in the body. Waste products
cannot be easily removed as well.
• A transport system helps to carry substances from
one part of the body to another.
Mammalian Transport System
Lymphatic system
Blood system
blood
fluid
blood
vessels
heart
Structure and Composition of
Blood
What are the components of blood?
Investigation 8.1
• Examine a slide of blood smear using
a light microscope.
• Make drawings of the different cells
observed.
Composition of Blood
platelet
white
blood cell
(lymphocyte)
red blood
cells
white
blood cell
(phagocyte)
Blood Tissue
fluid part
55%
blood plasma
red blood cells
(erythrocytes)
cell-like part
45%
blood cells
(corpuscles)
platelets
(thrombocytes)
white blood cells
(leucocytes)
lymphocytes
phagocytes
Blood Plasma
• A pale yellowish liquid
• About 90% water and 10% mixture of dissolved
substances.
• The amounts of the various dissolved substances in
the blood plasma are kept relatively constant.
• Blood plasma transports the dissolved substances
and blood cells around the body.
Blood Plasma: Dissolved
Substances
• Soluble proteins:
– Fibrinogen and prothrombin: for blood clotting
– Antibodies: for fighting diseases
• Dissolved minerals (occurring as ions):
– Hydrogencarbonates, chlorides, sulfates
– Phosphates of calcium, sodium and potassium
• Food substances: glucose, amino acids, fats,
vitamins
• Excretory products: urea, uric acid, creatinine
• Hormones (e.g. insulin)
Blood Serum
• When storing blood, blood-clotting factors
(fibrinogen and prothrombin) are removed to prevent
the blood from clotting during storage.
• Blood plasma with its blood-clotting factors removed
is known as blood serum.
Blood Tissue
fluid part
55%
blood plasma
red blood cells
(erythrocytes)
cell-like part
45%
blood cells
(corpuscles)
platelets
(thrombocytes)
white blood cells
(leucocytes)
lymphocytes
phagocytes
Red Blood Cells (Erythrocytes)
• Quantity: ≈5 million red blood cells per mm3 of
blood.
• Produced by the bone marrow.
• Lifespan: 3-4 months
• Worn-out cells are destroyed in the spleen.
• Haemoglobin obtain from destroyed cells are
brought to the liver and broken down to form:
– bile pigments (excreted as bile)
– Iron (stored in liver)
Structure and Function of Red
Blood Cells
Structure
Contains
haemoglobin
Function
Haemoglobin combines reversibly with
oxygen, enabling red blood cells to transport
oxygen from lungs to all cells in the body.
Circular, flattened Increases cell’s surface area to volume ratio
biconcave disc
for faster absorption and release of oxygen.
Absence of
nucleus
Allows cell to contain more haemoglobin
Elastic
Can turn bell-shaped when squeezing
through blood vessels smaller than its
diameter.
Role of the Bone Marrow
• Location: spongy red tissue found in the centre of
bones
• The marrow of the vertebrae, ribs and pelvis contain
stem cells:
– Can divide many times to produce different cells
• Many blood cells are produced throughout one’s life
as the cells have a limited lifespan.
– Red blood cells: 120 days
– Platelets: 6 days
– White blood cells: 1 day or less
Blood Tissue
fluid part
55%
blood plasma
red blood cells
(erythrocytes)
cell-like part
45%
blood cells
(corpuscles)
platelets
(thrombocytes)
white blood cells
(leucocytes)
lymphocytes
phagocytes
White Blood Cells (Leucocytes)
•
•
•
•
•
Quantity: ≈5000-10000 per mm3 of blood
Produced by the bone marrow.
Lifespan: 1 day or less
Size: larger than red blood cells
Features:
– Colourless: does not contain haemoglobin
– Contains nucleus
– Can move, change its shape and squeeze through
walls of capillaries
2 Kinds of Leucocytes
• Lymphocytes
– Nucleus: large, round
– Cytoplasm: non-granular, small
amounts
– Shape: round
– Movement: limited
– Function: produce antibodies to
protect body from disease-causing
microorganisms
2 Kinds of Leucocytes
• Phagocytes
–
–
–
–
–
Nucleus: lobed
Cytoplasm: granular
Shape: irregular
Movement: can be fast
Function: ingests (take in and digest) foreign particles
such as bacteria
Blood Tissue
fluid part
55%
blood plasma
red blood cells
(erythrocytes)
cell-like part
45%
blood cells
(corpuscles)
platelets
(thrombocytes)
white blood cells
(leucocytes)
lymphocytes
phagocytes
Blood Platelets (Thrombocytes)
•
•
•
•
Not true cells
Membrane-bound fragments of cytoplasm
From bone marrow cells
Involved in blood clotting
Blood Groups
• The understanding of blood groups is important in
blood transfusion.
• If the wrong blood group is being put into a person,
red blood cells from the donor will clump together.
This is known as agglutination.
• The clumps will block up small blood vessels and
prevent the flow of blood, causing death.
Agglutination of Red Blood Cells
• Surface of all red blood cells contain antigens.
These special proteins are the same on all cells.
• Blood plasma contains natural antibodies which are
always present in blood.
• A person’s blood group is based on the types of
antigens and antibodies present in the blood.
• When both antigen and antibody of the same type
are present, agglutination occurs.
Blood Groups
B
B
B
Blood group A
Blood group AB
A
B
A
A
A
A
Blood group B
B
B
Blood group O
A
Antigens and Antibodies in
Blood Groups
Mixing Blood Groups
Functions of the Blood
transport
function
protective
function
• food substances
• blood clotting
• excretory products
• phagocytosis
• hormones
• antibody production
• heat
• oxygen
Transport Function of the Blood
The following are carried in solution in blood plasma:
• Digested food:
– Transported from blood capillaries in the small
intestine to all parts of the body
• Excretory products:
– Nitrogenous waste – urea, uric acid, creatinine,
removed from the body as blood flows through the
kidneys
– Carbon dioxide from cell respiration enters the blood
as hydrogencarbonate ions, and converted to carbon
dioxide in the lungs and expelled when we exhale
Transport Function of the Blood
The following are carried in solution in blood plasma:
• Hormones
– Transported from production glands to the parts of the
body which require them
• Heat
– Produced in respiring body tissues
– Main heat production is in the muscles and liver
– Blood distributes the heat throughout the body,
maintaining a uniform body temperature
Gas Exchange
in
the
Body
O
2
CO2
alveolus
(in lung)
O2
CO2
HCO3-
O2 (oxyhaemoglobin)
veins
arteries
capillaries
HCO3-
O2 (oxyhaemoglobin)
C6H12O6 + 6O2  6CO2 + 6H2O + energy
Tissue cells
Transport of Oxygen in the
Blood
• As blood passes through the lungs, oxygen diffuses
from the alveoli into the blood.
• Oxygen combines reversibly with haemoglobin to
form an unstable compound, oxyhaemoglobin,
which is bright red in colour.
• Blood transports oxyhaemoglobin to all tissues of
the body.
• As blood passes through tissues with low oxygen
concentration, the oxyhaemoglobin releases its
oxygen, which diffuses into the cells.
Transport of Oxygen in the
Blood
O2
haemoglobin
(purplish-red)
oxyhaemoglobin
(bright red)
O2
Carbon Monoxide Poisoning
• If carbon monoxide enters the blood, it combines
more readily with haemoglobin.
• Carboxyhaemoglobin is formed, which is bright pink.
• This compound does not readily give up its carbon
monoxide.
• Haemoglobin is unavailable to transport oxygen.
• Blood cannot transport oxygen, leading to death.
• Carbon monoxide is found in car exhaust fumes.
Human Adaptation to High
Altitudes
• At high altitudes, oxygen concentration in the
atmosphere is low.
• Body produces more red blood cells, thus increasing
the haemoglobin content per unit volume of blood.
• More oxygen can be transported to tissue cells per
unit time.
• This is known as acclimatisation.
Human Adaptation to High
Altitudes
• Long-distance runners often train at high altitudes
for several months before a race.
– Amount of haemoglobin in the blood increases
– When running the race at lower altitudes, their bodies
can carry oxygen more efficiently.
– Runners can run for longer periods.
Protective Function: Blood
Clotting
• Also known as blood coagulation.
• Blood exposed to air will form a clot
• Function of the clot:
– Seal the wound and prevent excessive loss of blood
– Prevent foreign particles from entering the blood
• Some people suffer from haemophilia, a hereditary
disease, where their blood-clotting mechanism is
impaired. The person can bleed to death with slight
injuries.
The Blood Clotting Process
damaged tissue
and platelets
produce
thrombokinase
(enzyme)
prothrombin
(inactive)
thrombokinase
thrombin
(active)
calcium ions
thrombin
fibrinogen
insoluble fibrin threads,
form mesh to trap blood cells
The Blood Clotting Process
• In undamaged blood vessels, the blood does not
clot due to the presence of heparin.
• Heparin is produced in the liver.
• When thrombokinase is released, it neutralizes the
action of heparin so that clotting can take place.
Protective Function:
Phagocytosis
When bacteria enters the blood:
• phagocyte will engulf the bacteria and enclose them
• phagocyte ingests the bacteria
• bacteria is digested in the phagocyte
• Some phagocytes may get killed. These cells,
together with dead bacteria, form pus.
Protective Function:
Phagocytosis
bacteria
bacteria
ingested into
cytoplasm
phagocyte
engulfing
bacteria
Protective Function: Antibody
Production
When disease-causing organisms (pathogens) enter
the blood:
• pathogens stimulate lymphocytes to produce
antibodies which destroy bacteria by:
– attaching to them and causing their surface
membrane to rupture
– causing bacteria to agglutinate so they can be easily
ingested by phagocytes
– neutralize harmful toxins produces by bacteria
– attaching to viruses and making them unable to bind
to a host cell.
Protective Function: Antibody
Production
• Antibodies can stay in the blood for a long time after
overcoming the disease.
• The person then becomes immune or resistant to
the infection.
• In immunisation:
– dead bacteria are injected into the blood
– antibodies are formed
– the person is temporarily immune from disease
Organ Transplant and Tissue
Rejection
• In a tissue or organ transplant, the transplanted
organ may be treated as a foreign body by the
recipient’s immune system.
• The recipient’s lymphocyte may produce antibodies
to destroy the transplanted organ.
• Doctors must be careful to obtain transplants from
suitable donors to avoid rejection.
• There will be no rejection if the transplanted tissue /
organ came from the same person.
Organ Transplant and Tissue
Rejection
To prevent tissue rejection:
• a tissue match is necessary – tissues from both
donor and recipient must be as genetically close as
possible
• take immunosuppressive drugs which inhibit the
responses of the recipient’s immune system
– recipient’s resistance to other infections is reduced
– recipient must take drugs for the rest of his life
Mammalian Transport System
Lymphatic system
Blood system
blood
(fluid)
blood
vessels
heart
circulatory
system
The Circulatory System
• Function: to transport substances from one part of
the body to another.
• 2 types of systems:
– open system: found in insects, where blood flows
freely through tissues and bathes them
– closed system: found in vertebrates, where blood is
contained in blood vessels
Components of the
Human Circulatory
heart
System
vein
Components:
• Heart
• Blood vessels:
artery
blood
flowing
back to
the heart
veins
a capillary
network links
arteries and veins
capillaries
venules arterioles
arterioles
blood flowing
from the heart
arteries
–
–
–
–
–
Arteries
Arterioles
Capillaries
Venules
Veins
The Circulatory System – Heart
• A muscular pump
• Function: keep blood circulating
throughout the body
• When relaxed: it fills up with blood
• When contracted: blood is
squeezed out with a great force
The Circulatory System – Blood
Vessels
Arteries
• Blood vessels that carry blood away from the heart
• Branches to form arterioles
Arterioles
• Arteries branch to form arterioles
• Branches to form capillaries
The Circulatory System – Blood
Vessels
Blood capillaries
• Microscopic blood vessels found between tissue
cells
Venules
• When leaving an organ / tissue, capillaries unite to
form venules
Veins
• Venules join together to form veins
• Carry blood back to the heart
The Circulatory System – Blood
Vessels
arterioles
venules
vein
artery
capillaries
Blood Vessels – Arteries
• Function: Receives blood directly from the heart
structure
function
Thick, elastic Withstand high blood pressure of the blood as it is
walls
forced out of the heart. The wall is much thicker in
arteries nearest the heart.
Elastic walls
Constricts
and dilates
Enables artery wall to stretch and recoil, pushing the
blood in spurts along the artery. This gives rise to the
pulse.
Achieved through contraction and relaxation of
muscles in the arterial wall.
When it constricts: lumen becomes narrower, less
blood flows through per unit time.
When it dilates: lumen becomes wider, more blood
flows through per unit time.
Blood Vessels - Arteries
• Most arteries carry oxygenated blood from the heart
to other parts of the body.
– Exception: the pulmonary artery carries
deoxygenated blood from the heart to the lungs.
external layer (connective tissue)
middle layer (smooth muscle and
elastic fibres)
endothelium
lumen
wavy elastic band
Blood Vessels – Capillaries
• Function: Food substances diffuse out, while waste
materials diffuse into capillaries
structure
Walls made up of a
single layer of
flattened cells
(endothelium)
Endothelium is
partially permeable
Repeated branching
function
Microscopic capillaries can be found between
the cells of almost all tissues.
Quick diffusion of substances into and out of
capillaries
Provide large surface area for exchange of
substances. Blood pressure lowers, slowing
down the flow of blood and giving more time
for the exchange of substances
Blood Vessels - Capillaries
single layer of
endothelial cells
Blood Vessels – Veins
• Function: transports blood to the heart
structure
function
thinner, less
elastic walls
Low blood pressure, where blood flows slowly and
smoothly.
presence of
valves
Internal valves prevent backflow of blood. Known as
semi-lunar valves due to their half-moon shape.
large lumen
Lowers blood pressure to allow blood to flow slowly
• Movement of blood is assisted by the action of
skeletal muscles on the veins.
– Exercising the muscles increases the pressure
exerted on the veins
Blood Vessels - Veins
• Most veins carry deoxygenated blood from other
parts of the body to the heart.
– Exception: the pulmonary vein carries oxygenated
blood from the lungs to the heart.
external layer (connective tissue)
middle layer (smooth muscle and
elastic fibres)
endothelium
lumen
Flow of Blood in Blood Vessels
Blood Circulation in Vertebrates
• In a double circulation,
blood passes through the
heart twice in one
complete circuit.
pulmonary
circulation
Double Circulation in Mammals
systemic
circulation
– Pulmonary circulation
– Systemic circulation
systemic
circulation
• Blood flows from the heart
to the lungs, and then
back to the heart.
• Blood goes from the heart
to lungs via the pulmonary
artery.
• Blood returns to the heart
from the lungs via the
pulmonary vein.
pulmonary
circulation
Double Circulation – Pulmonary
Circulation
systemic
circulation
• It is the circulation of
blood around the body.
• Oxygenated blood leaves
the left side of the heart
and is distributed by
arteries to all parts of the
body (except the lungs).
• Veins carry deoxygenated
blood from all parts of the
body to the right side of
the heart.
pulmonary
circulation
Double Circulation – Systemic
Circulation
Double Circulation – Advantages
• Blood entering the lungs is at a lower pressure
compared to blood leaving the heart.
– Blood can flow more slowly through the lungs
– More time for blood to absorb oxygen before returning
to the heart
• Heart can pump the blood at high pressure to the
rest of the body.
– Distributes oxygenated blood to the body tissues
more quickly
– Maintain high metabolic rate in mammals
The Heart – Structure
External structure:
• Surrounded by a pericardium, which is made up of
two layers of membrane
– Inner membrane: in contact with the heart
– Between the two membranes: fluid to help reduce
friction when the heart is beating
The Heart – Structure
Internal structure:
• 4 chambers:
– Upper chambers: atria (singular: atrium)
– Lower chambers: ventricles
• Divided down the middle into left and right halves by
a muscular wall called the median septum
– Prevents the mixing of deoxygenated blood and
oxygenated blood
superior
vena cava
aortic arch
pulmonary
arch
pulmonary
artery
pulmonary
vein
right atrium
left atrium
semi-lunar
valves
inferior
vena cava
chordae
tendineae
right ventricle
median septum
bicuspid valve
left ventricle
Route of the Blood in the Heart
1. Return of deoxygenated blood from the rest of the
body to the heart
•
•
•
Blood from the head, neck and arms enter via the
superior vena cava
Blood from the other parts of the body (except
lungs) enter via the inferior vena cava
Enters the right atrium
Route of the Blood in the Heart
2. Right atrium contracts: blood goes into the right
ventricle
•
•
Tricuspid valve opens (consists of 3 flaps, attached
to the walls by chordae tendinae)
Pressure in the right atrium is higher than the
pressure in the right ventricle.
Route of the Blood in the Heart
3. Right ventricle contracts:
•
•
•
•
•
Blood pressure in right ventricle causes the tricuspid
valve to close, preventing backflow of blood into the
atrium.
Chordae tendinae prevent valve flaps from reverting
into the atrium.
Blood leaves right ventricle via the pulmonary arch
Pulmonary arch divides into two pulmonary arteries,
one to each lung.
Semi-lunar valves in pulmonary arch prevent
backflow of blood into the right ventricle.
Route of the Blood in the Heart
4. Blood enters the lungs:
•
•
Blood is slowed down by the branching of the artery
into a capillary network.
Gaseous exchange occurs
5. Oxygenated blood from the lungs return to the
heart:
•
•
Blood enter via the pulmonary vein
Blood enters the left atrium
Route of the Blood in the Heart
6. Left atrium contracts, blood goes into the left
ventricle:
•
•
Bicuspid valve opens (consists of 2 flaps)
Pressure in the left ventricle is lower than the
pressure in the left atrium.
Route of the Blood in the Heart
7. Left ventricle contracts:
•
•
•
Bicuspid valve closes
Blood leaves left ventricle via the aortic arch
Semi-lunar valves in aortic arch prevent backflow of
blood into the left ventricle.
Route of the Blood in the Heart
8. Blood in aorta is distributed to the rest of the body
(except lungs):
•
•
•
Aortic arch have branches to direct the blood to
specific areas of the body
Blood entering the aorta is at a very high pressure
Two small coronary arteries emerge from the aortic
arch, to bring oxygen and nutrients to the heart
muscles
The Cardiac Cycle
• Two keywords:
– Systole: contraction
– Diastole: relaxation
• 3 stages:
–
–
–
–
Complete diastole (whole heart)
Atrial systole
Ventricular systole / Atrial diastole
Ventricular diastole (back to complete diastole)
The Cardiac Cycle
• Complete diastole
–
–
–
–
Both atria and ventricles are relaxed
Right atrium receives blood from vena cavae
Left atrium receives blood from pulmonary veins
Some blood flows directly into the ventricles
pulmonary
vein
vena
cava
right atrium
right
ventricle
left
atrium
left
ventricle
The Cardiac Cycle
• Atrial systole
– Atria contract
– Blood is forced into the ventricles
right
ventricle
left
ventricle
The Cardiac Cycle
• Ventricular systole / Atrial diastole
– Ventricles contract – high pressure in ventricles
– Blood flows from left ventricle into the aortic arch, and
from right ventricle into the pulmonary arch
– Bicuspid and tricuspid valves close, producing a loud
‘LUB’ sound.
aortic arch
pulmonary
arch
tricuspid
valve
bicuspid
valve
The Cardiac Cycle
• Ventricular diastole
– Ventricles relax
– Drop in blood pressure in ventricles causes semilunar valves in the arches to close
– Produce a soft ‘DUB’ sound.
– Whole heart is relaxed
(complete diastole)
right
ventricle
left
ventricle
The Heart and Blood Pressure
• Definition of blood pressure:
– the force that blood exerts on the walls of blood
vessels
• Measured using a sphygmomanometer
• Unit of measurement: mm of mercury
The Heart and Blood Pressure
• High blood pressure in arteries:
– Occurs during ventricular systole when blood is
forced into arteries
• Decrease in blood pressure:
– Occurs during ventricular diastole
• Blood pressure varies in different parts of the body.
– Highest: near aortic arch
– Lowest: vena cava (almost 0 mm mercury)
Blood Pressure of a Person
• Average blood pressure:
120 (systolic)
80 (diastolic)
• High blood pressure: 140/90 or higher
– Can occur temporarily after heavy exercise or when a
person is angry
– Can be persistent, which is unhealthy
Pressure Changes in the Heart
(Left)
ventricular diastole
Pressure / mm of mercury
ventricular
systole
pressure in aorta
pressure in ventricle
atrial
diastole
Time/s
atrial
systole
pressure in atrium
Pressure Changes in the Heart
(Right)
ventricular diastole
Pressure / mm of mercury
ventricular
systole
pressure in ventricle
pressure in aorta
atrial
diastole
Time/s
atrial
systole
pressure in atrium
Main Arteries of the Body
refer to LN
Tissue Fluid
• Description: colourless liquid
• Location: between tissue cells
• Function: carry substances in solution between
tissue cells and blood capillaries
• Formation:
– Blood pressure at arterial end of capillaries is high
– Blood plasma is forced through capillary walls as
tissue fluid.
• Other names: intercellular fluid, interstitial fluid
Exchange of Substances between Blood
and Tissue
• Wanted substances:
– food substances and oxygen
– originate from the arterioles
– diffuse from the blood into the tissue fluid
• Unwanted waste products:
– hydrogencarbonate ions, urea, creatinine
– diffuse from cells into tissue fluid, and then through
capillary walls into the blood plasma
Red Blood Cells in Capillaries
• Lumen of the capillary is very narrow, thus red blood
cells have to move through the lumen in single file.
• Red blood cells may become bell-shaped as they
pass through narrow blood capillaries.
• Advantages:
– Reduce diameter of the cell so that it can pass
through easily
– Increase surface area to speed up transfer
– Reduce rate of blood flow
Coronary Heart Disease
• Cause: blockage or narrowing of coronary arteries
– Arteries lie on the outside of the heart
– Carry blood to the muscles in the walls of the heart
– Muscle cells are kept alive by the fresh supply of
oxygen from the arteries, keeping the heart pumping
Coronary Heart Disease
• Result: heart attack
– Blood flow to a particular part of the heart may be
completely blocked
– Heart does not receive sufficient oxygen and nutrients
– Region of heart muscle dies
– Blood is unable to pump blood to various parts of the
body
Causes of Coronary Heart
Disease
• Atherosclerosis
– Fatty substances (e.g. cholesterol, polysaturated fats)
deposited on the inner surface of the coronary
arteries.
– Lumen of the artery is narrowed
– Blood pressure increases
– Artery develops rough inner surfaces
– Increases the risk of forming a blood clot
Causes of Coronary Heart
Disease
• Coronary thrombosis
– Thrombosis: blood clot
– Cuts off blood and oxygen supply to the heart
muscles
– Heart attack occurs
Reducing the Risk of Coronary Heart
Disease
• Proper diet
– Replace animal saturated fats with polyunsaturated
plant fats: may lower cholesterol
– Rich in dietary fibres from green vegetables and fruits
• Proper stress management
• Avoid smoking
– Nicotine increases blood pressure and the risk of
coronary thrombosis
– Carbon monoxide increases the risk of
atherosclerosis
• Regular physical exercise