1.1 The Importance of having a transport system in some multicellular organisms

Large multicellular organisms:

-increased need in obtaining their cellular requirements and getting rid of their waste products

- the TSA/V ratio decreases

- the cells are often located far away from the external surface of the body

- exchange of substances by simple diffusion is too slow to sustain cellular activities

Compared to unicellular organisms

-large TSA/V ratio

-enabling substances and waste products to diffuse easily through the organism

-directly from their external environment

-these organisms do not need an internal transport system

How the problem is overcome in multicellular organisms?

Developed circulatory system to transport substances in their bodies

1.2 Synthesising the concept of circulatory system

Circulatory system:

3 components:

Medium – blood, haemolymph Vessels - arteries, veins and capillaries Pump - muscular heart

Erythrocytes (red blood cells)

- Small biconcave disc – increase the surface area for gaseous exchange through the thin cell membrane

- No nucleus- Contains haemoglobin- transport oxygen- Produced in the bone marrow- Destroyed by the phagocytes in the liver and spleen- Live for 120 days

Leucocytes (white blood cells)

- Defence against disease- Have nuclei- No haemoglobin- Larger than red blood cells- Do not have fixed shape- Manufactured in the bone marrow, but migrate to the thymus gland and lymph nodes for their

growth and development stages- 2 basic types:- (a) Granulocytes – granular cytoplasm and lobed nuclei

Granulocytes ExplanationNeutrophils Phagocytes.

Engulf foreign materials, for eg. Bacteria by phagocytosis and destroy them

Eosinophils Control allergic responsesBasophils Secrete heparin to prevent blood from clotting

(b) Agranulocytes- clear cytoplasm and their nuclei are not lobed

Agranulocytes ExplanationMonocytes The largest

Phagocytic macrophagesEngulf dead cells and bacteria that enter the body

Lymphocytes SmallestProduces antibodies that destroy pathogens or to neutralize toxins

Platelets- Small irregularly shaped fragments of large cells in the bone marrow- Blood clotting

Plasma

-pale yellow liquid part of the blood

-90% water and 10% dissolved solutes- nutrients,gases,minerals,hormones,plasma protein and excretory wastes

Blood serum – same as plasma except that clotting factors such as fibrin have been removed

Function of blood in transport

Transport of oxygen O2 combines with haemoglobin to form oxyhaemoglobin

Transport of CO2 70% of carbon dioxide is transported in the form of HCO, 23% combines with haemoglobin and forms carbaminohaemoglobin and 7% dissolves directly in the blood plasma

Transport of absorbed food Soluble digested food materials are absorbed into capillaries of the villi in the small intestine

Transport of excretory waste products Urea is transported by the blood to the kidneys to be excreted

Transport of heat Help to regulate body temperature by distributing heat from heat-producing sites (skeletal muscles) to areas of heat loss(skin)

Transport of hormones Transports hormones such as insulin and glucagon produced by pancreas to the target organs

Transport of water to tissues Component of protoplasm and is transported by blood to provide a medium for biochemical reaction.

Function of haemolymph in transport:

-bathes the tissues and internal organs directly

-nutrients such as digested food substances and hormones diffuse from the haemolymph into the cells

-waste products diffuse out from the cells into the surrounding haemolymph.

Arteries Capillaries VeinsTransport blood away from the heart

Connects arteriols to venules Transport blood to the heart

Transport oxygenated blood except pulmonary artery

Act as the sites for exchange of substances with the cells

Transport deoxygenated blood(except the pulmonary vein)

Thick muscular wall (epithelium,smooth muscle and connective tissue)

Thinnest wall, one cell in thickness(only epithelium)

Thinner wall (epithelium,smooth muscle and connective tissue)

No valves except semilunar valve at the base of the aorta and pulmonary artery.

No valves Valves present to prevent back flow of blod

Blood flows in pulses under high pressure

No pulses.Pressure lower than arteries but higher than veins.

No pulses.Blood flows under lower pressure than arteries

How blood is propelled through the human circulatory system?

1. Myogenic cardiac muscles- heart muscles contract and relax automatically throughout life and are not controlled by the nervous system.

2. How?2.1 Sino-atrial node(SAN) acts like a pacemaker which intiates the heartbeat.2.2 SAN generates a wave of impulses which spread to the 2 atria, causing them to contract

simultaneously.2.3 Blood is forced from the atria into the ventricles.2.4 Atrio-ventricular node(AVN) is then stimulated.2.5 Impulses from the AVN are conducted to the ventricular walls by bundle of His and Purkinje

fibres.2.6 Causes both ventricles to contract simultaneously to pump blood out of the heart.

SAN generate impulses spread to both atria both atria contract blood flow from atria to ventricles

AVN is stimulated generate impulses spread to both ventricles

Both ventricles contract to pump blood out of the heart

Blood can circulate in humans because:

Pumping of the heart

- Generates sufficient force to move blood through the arteries,arterioles and capillaries.- When the blood reaches the veins, however the pressure produced by the heart is insufficient

to force it back into the heart.

- The blood in the veins also has to flow against gravitational pull.

Contraction of skeletal muscles around veins

- When the body moves, the skeletal muscles around the veins contract and press on the veins.- The blood pressure increases, forces open the valves pushes the blood towards the heart.- The valves in the veins prevent the blood from flowing backwards

Heart rate may be modified by certain external factors:1. Sympathetic nerve carrying impulses to the heart can increase the heart rate.2. Parasympathetic nerve can slow it down.3. Secretion of hormone adrenaline cause the heart to beat faster.4. Increase in the partial pressure of CO2 in the blood also increases the heart rate.5. Increase in body temperature also can increase the heart rate.

Regulatory mechanism of blood pressure:

1. Baroreceptors located in the walls of the aorta and carotid arteries that branch out from the aorta, monitor the pressure of blood flowing to the body and to the brain.

2. An increase in blood pressure stretches the baroreceptors.3. Impulses are sent to the cardiovascular control centre in the medulla oblongata of the brain.4. Impulses are sent via the parasympathetic nerve to the heart.5. This slows down the heartbeat, resulting in a decrease in blood pressure.6. A decrease in blood pressure increases stimulation of the sino-atrial node by the

sympathetic nerve.7. This increases the contraction of the cardiac muscles of the heart and the smooth muscles

of the arteries.8. Blood pressure increases and returns to its normal level.

Circulatory systems in fish,amphibians and humans:

1. Closed circulatory system- blood flows under pressure through closed vessels in a continuous circuit around the body

Fish- Deoxygenated blood enters the atrium and then the ventricle.- Ventricle pumps the blood to the capillaries in the gills where gaseous exchange occurs- The pressure drops as the oxygenated blood leaves the gills and flows back to the heart.- Blood flows through the heart only once in a complete cycle.(single circulatory system)

Amphibians:- Have double closed circulatory system- a pulmonary circulation system (from heart to the lung

and back to the heart) and a systemic circulation system ( from the heart to the other parts of the body and back to the heart)

- Atria and ventricle not separated by septum- Oxygenated blood and deoxygenated blood mixes in the ventricle- Lower levels of oxygen but is sufficient to meet the cellular requirements of amphibians

Humans:- Prevents mixing of the oxygenated and deoxygenated blood- Blood can be maintained at a relatively high pressure by the contraction of the thick muscular

left ventricle.- Right ventricle is smaller and its wall less muscular as it only has to generate sufficient pressure

to pump blood a short distance from the heart to the lungs- The blood enters the heart twice during one complete cycle

1.3 Understanding the mechanism of blood clotting

1. Necessity for blood clotting:

(a) preventing serious blood loss – when there is damage to the blood vessels

(b) preventing the entry of microorganisms and foreign particles – seals wound

(c) maintaining blood pressure – prevents blood pressure from falling to a low level

- pressure is needed to maintain proper blood circulation

(d) maintaining circulation of blood in a closed circulatory system

2. Mechanism of blood clotting:

Injury/rupture in blood vessels

↓

Platelets clump at the wound

↓

Release of thrombokinase (platelet releases)

↓

Thrombin ____________ prothrombin ← Vitamin K

a. Thrombokinase in the presence of factor VIII (clotting factor) converts prothrombin into thrombin

b. Thrombin converts fibrinogen(soluble plasma protein) into insoluble fibrin fibres which form a meshwork of threads over the wound.

c. Erythrocytes and platelets are trapped in the fibrin fibres and blood clot forms.d. It dries to form a scab which covers the wound.

Consequences of blood clotting related problems:

a. Haemophiliai. Lack of gene for the production of certain clotting factors, for example factor VIII

ii. Impaired clotting mechanismiii. Causes serious bleeding particularly in the jointsiv. In severe cases, haemophiliacs may die of internal or external bleeding

b. Thrombosisi. A local blood clot(thrombus) is formed on the damaged rough inner wall of arteryii. May cause blockage of artery(thrombosis)iii. When the thrombus dislodges and is carried away by blood circulation it is known as

embolusiv. Embolus may be trapped in a small artery where it blocks the blood flow(embolism)

c. Angina , heart attack , stroke

1.4 THE LYMPHATIC SYSTEM

1. Formation of interstitial fluid:

(a) there is higher hydrostatic pressure at the arterial end of the capillaries.

(b) This high pressure forces some fluid(plasma) out through the capillary walls into the intercellular

Spaces(spaces between cells) between the cells.

(c) Materials(amino acid,hormone,glucose,nutrients) from blood capillaries enter these spaces.

(d) Once the fluid leaves the capillary walls, it is called interstitial or tissue fluid

2. Composition of interstitial fluid:

(a) similar in composition to blood plasma

(b) But it has no erythrocytes, platelets or large protein molecules because they are too large to pass

Through the capillary wall

3. Importance of interstitial fluid:

(a) it forms the internal environment of the body

(b) bathes the cell and supplies them with their requirements

(c) O2 and nutrients diffuse from the blood through the interstitial fluid and into the cells

(d) Excretory waste products( co2 and urea) diffuse out of the cells into the interstitial fluid

4. fate of interstitial fluid

a. 90% of the interstitial fluid flows back into the venous end of the capillary system where the

hydrostatic pressure is low

b. 10% of the interstitial fluid enters the lymphatic capillaries and is called lymph

c. if excess interstitial fluid is unable to return to the blood circulatory system it will accuulate and

cause tissue swelling – oedema

5. structure of the lymphatic system:

a. Lymph is colourless

b. Lymph is similar in composition to blood plasma but has no erythrocytes, platelets or large

protein molecules

c. Lymph contains a higher number of lymphocytes than blood

d. Lymph travels through the lymphatic vessels by the contraction of the surrounding skeletal

muscles

e. Lymph flows in 1 direction:

i. one end of the vessel is closed

ii. valves present in larger vessels to prevent backflow

iii. smaller lymphatic vessels join to form larger vessels

iv. vessels from the left side of the body, the alimentary canal and the right side of the lower

part of the body flow into the thoracic duct(largest lymphatic vessel in the body)

v. Thoracic duct carries lymph to the left subclavian vein and back into the bloodstream

vi. Lymph from the right side of the head and chest flow into the right lymphatic duct.

vii. Right lymphatic duct carries lymph to the right subclavian vein and back into the

bloodstream

viii. Lymph nodes are mainly found at the neck, armpits and the groin.

1. Filter out bacteria and other foreign particles2. Phagocytes present in the nodes engulf and destroy these foreign particles

ix. Lymphocytes in the lymphatic tissues produce antibodies which aid in the destruction

of pathogens and the neutralization of toxins

6. Role of lymphatic system in transport:a. Lymphatic system collects the interstitial fluid and returns it to the circulatory systemb. Lacteals are lymphatic capillaries in the villi of the ileum

- absorb fats and fat-soluble vitamins and transport them to the blood circulatory system

7. Comparison between the content of blood, interstitial fluid and lymph:

a. Similarities:

* all of them transport dissolve substances such as o2 and waste products

* all of them have white blood cells

glucose Protein molecules

O2 Waste materials

Erythrocytes Leucocytes platelets

bloodlymphInterstitial fluid

1.5 role of circulatory system in the body’s defence mechanism

1. 1 st line of defence:

a. skin and mucous membrane

b. skin acts as a physical barrier

- made up of dead keratinized layer which is difficult to penetrate

c. tears secreted by tear glands and acidic sebum secreted by sebaceous gland contains lysozymes

which destroy bacteria

d. Mucus secreted by mucous membranes in the nasal cavity and trachea trap dust particles and

bacterial spores

e. When microorganisms enter the stomach, they are killed by the HCI acid in the gastric juices

2. 2nd line of defence:

a. Phagocytic white blood cells (neutrophils) act as phagocytes

3. 3rd line of defence:

a. lymphocytes –produce

b. antibody is a protein produced by lymphocytes in response to the presence of an antigen

c. antigen : foreign substance(bacteria) which stimulates the body to produce an immune

response

d. antibodies are specific in action and promote the destruction of antigens in different ways:

e. after an infection, some lymphocytes remain in the body as memory cells

f. The memory lymphocytes help to defend the body against further infection by the same antigen

g. the body is said to be immune against the particular disease

a. Immunity - refers to the ability of an organism to defend itself against infection by pathogensb. Depends on :

i. Presence of lymphocytesii. Production of antibodies which give a specific immune response

c. Types :i. Active immunity(natural and artificial)- body produce antibodyii. Passive immunity(natural and artificial)- body receive antibody

Active natural immunity:

i. Is acquired after a person recovers from an infection, such as chicken pox or measlesii. The body has the ability to produce more antibodies rapidly against further attack by the

same type of invading antigen

Active artificial immunity:

i. Vaccine is injected into bloodstream, the lymphocytes in the body produce antibodies against that particular antigen.

ii. Vaccine contains killed or weakened antigeniii. This process is known as immunization.iv. More than 1 vaccine is needed. This because after first injection of vaccine the a………….

produced s………w and insufficient v. The booster(second) injection stimulates a quicker and longer lasting response, where the

concentration of antibodies in the blood increases beyond the level of immunity.vi. Eg. B.C.G. vaccine for tuberculosis(tibi), Salk vaccine for poliomyelitis.There also vaccine for

small pox(demam campak), measles(cacar), yellow fever, hepatitis A, hepatitis B and rubella.vii. Some vaccine can induce immunity for a few years only, eg. Hepatitis B and cholera. A

booster is needed after a few years when the antibody wears off.

Passive natural immunity;

i. Antibodies are transport from the mother across the placenta to the foetus or through the mother’s milk to the young infact for a few months

ii. The baby can only get protection against certain diseases for a few months after the baby is born.

iii. Natural passive immunity is short-lived because the immunity response is not stimulated by the antigen. Lymphocytes are not stimulated to produce a………….

Passive artificial immunity

i. Injecting serum containing specific antibodies prepared from the blood of humans or other animals(horses, snakes)

ii. Treat patients who are already seriously ill. Serum(antibody) are injected directly into the body and react immediately.

iii. /8526698/Temporary immunity- injection serum can only induce a short lived immunity because tpppopp;1/.,mncc7\5266955/he level of antibody decreases rapidly. Another injection serum is needed to induce the immunity again.

iv. Eg diseases that can be treated by this type immunity – tetanus, diphtheria, rabies and snke bite

Natural active: Occurs during infection. It is active because lymphocytes are activated by antigens on

pathogen's surface.

Artificial active: Injecting or taking antigens by mouth. Takes time for T and B cells to be activated but gives

long lasting immunity.

Natural passive: Mother to child through placenta or milk.

Artificial passive: Used during potentially fatal diseases. Provides an instant response but only temporary as

antibodies are not the body's own so memory cells are not created. E.g. tetanus - injection of antitoxins given.

Memory cells are only produced in active immunity.

Protection for active immunity is permanent whereas in passive immunity it is only temporary.

Antigens are only encountered in active immunity.

Active immunity takes several weeks to become active but passive is immediate.

Transport of substances in plants

Translocation:

1. Transport of soluble organic food materials( produce from the p_________) by the phloem from the leaves to other parts of the plant

2. Importance:i. Sugars and amino acids are transported to growing regions for growth and developmentii. To cells for metabolismiii. Excess is stored in organs such as roots

Transpiration:

1. Is the loss of water in the form of water vapour from a plant to the atmosphere.2. Most of the water lost lost through the stomata of leaves3. A small amount is lost through the cuticle or through the lenticels in woody stems4. Importance:

i. Creates a transpirational pull that draws water and dissolved mineral salts from the roots to the leaves

ii. Water: - photosynthesis - keep cells turgid to give support to the leaves and young stems - keeps the plant cool in hot weatheriii. Mineral salts: - used for cell activities(active transport)

Pathway of water from the soil to the leaves:

a. Cell sap in root hairs is more concentrated than the surrounding soil solution. (soil solution is more hypotonic than the root hair cell)

b. Water diffuses into the roots by osmosis.c. The entry of water into a root cell causes it to become hypotonic.d. The cell sap of the adjacent cortex cell is hypotonic compared to the root hair cells, causing

water molecules to diffuse across the root, from cell to cell , by osmosise. Mineral ions are actively pumped from the root cells into the solution in the xylem vessels.f. These vessels found in the roots then become more concentrated.g. Water enters the xylem from the root cells by osmosish. This creates an upward force called root pressure, which helps to push water up to a certain

height in plants.

HOWEVER, ROOT PRESSURE ALONE IS INSUFFICIENT TO FORCE WATER TO THE TOP PART OF A TALL TREE

i. Capillary action is due to combined forces of cohesion(among H2O) and adhesion(among H2O and xylem wall)

j. Water molecules form a continuous water column in the xylem vessels due to cohesion.k. Adhesion forces between water molecules and the xylem walls enable water to move up along

the narrow xylem vessels.l. Water evaporates from the mesophyll cells into the intercellular air spaces of the leaves.m. The water vapour then diffuses from the intercellular air spaces through the open stomata into

surrounding air.n. The loss of water from the mesophyll cells is replaced by water from the xylem vessels in the

leaves.o. This creates a suction force called transpirational pull.

-at night, excess water absorbed from the soil is forced out through the hydathodes, located at the leaf edge. This process – guttation

Factors affecting the rate of transpiration:

a. Air movementi. Moving air carries water vapour away rapidly outside the stomata so that more water

molecules can diffuse to the surroundingsii. Rate of transpiration increases in windy conditionsiii. When there is little air movement, water vapours accumulates around the stomata and

the transpiration rate reduces.b. Temperature

i. High temperature increases the rate of transpiration.ii. Increases the kinetic energy of water molecules, causing them to move faster through

the stomatac. Light intensity

i. Higher light intensity stimulates stomatal opening and increases the rate of transpiration

ii. Sunlight also provides heat energy for the leaves and increase evaporation of water.

d. Relative humidityi. Relative atmospheric humidity is high, the air is saturated with water vapour and water

is unable to evaporate from plant cells.ii. Dry air increases the concentration gradient of water between the leaves and the

surrounding air, and the transpiration rate increases.

Opening and closing of stomata:

a. During the day, photosynthesis takes placeb. Glucose is produced and increases the osmotic pressure in the guard cells.

c. Potassium ions are actively transported from the epidermal cells into guard cells- increases the osmotic pressure in the guard cells

d. Water enters by osmosis from surrounding epidermal cells into the guard cells

e. guard cells becomes turgid and curve outward and the stomata opens

f. at night, no photosynthesis

g. potassium ions move out of the guard cells into the epidermal cells

h. osmotic pressure in the guard cells decreases

i. water diffuses out into surrounding epidermal cells by osmosis

j. guard cells becomes flaccid and the stomata closes.