Transportation
Circulatory system of human being, transportation in plants. Human beings like other
multicellular organism need a regular supply of foods, oxygen etc. This function is performed by
a circulatory system or transport system.
Transportation in Human Beings: The circulatory system is responsible for transport of
various substances in human beings. It is composed of the heart, arteries, veins and blood
capillaries. Blood plays the role of the carrier of substances.
1. Heart: Heart is a muscular organ, which is composed of cardiac muscles.
It is so small that, it can fit inside an adult’s wrist. The heart is a pumping organ which
pumps the blood.
The human heart is composed of four chambers, viz. right atrium, right ventricle, left
ventricle and left atrium.
Systole: Contraction of cardiac muscles is called systole.
Diastole: Relaxation of cardiac muscles is called diastole.
2. Arteries:
These are thick-walled blood vessels which carry oxygenated blood from the heart to
different organs.
Pulmonary arteries are exceptions because they carry deoxygenated blood from the heart
to lungs, where oxygenation of blood takes place.
3. Veins:
These are thin-walled blood vessels which carry deoxygenated blood from different organs
to the heart; pulmonary veins are exceptions because they carry oxygenated blood from
lungs to the heart.
Valves are present in veins to prevent back flow of blood.
4. Capillaries: These are the blood vessels which have single-celled walls.
Difference between arteries and veins
Direction of Blood Flow:
Arteries carry blood away from the heart, while veins carry blood back to the heart.
Blood Oxygenation:
Arteries generally carry oxygenated blood (except for the pulmonary artery), while veins
carry deoxygenated blood (except for the pulmonary vein).
Wall Thickness:
Arteries have thicker walls compared to veins. This is because arteries have to withstand
higher pressure as they carry blood pumped by the heart.
Valves:
Veins have valves that prevent the backflow of blood, especially in the limbs where
gravity can work against blood flow. Arteries generally do not have valves.
Pulse Sensation:
Arteries pulsate with each heartbeat, and this pulsation can be felt at various pulse points
in the body. Veins do not exhibit pulsation.
Appearance:
Arteries typically have a round, more uniform appearance, while veins may appear
flattened or collapsed, especially when blood is not actively flowing through them.
Location:
Arteries are usually found deeper within the body, closer to the bones and muscles, to
protect them from injury. Veins are often located closer to the body surface.
Blood Pressure:
Blood pressure in arteries is higher than in veins. This is because arteries receive blood
directly from the heart and must withstand the force of the heart's contractions.
Blood Color:
Arterial blood appears bright red due to its higher oxygen content, while venous blood
appears darker red or even blue-purple due to its lower oxygen content.
Collateral Circulation:
Arteries have more extensive collateral circulation, which means they have multiple
branches and connections to
ensure blood supply to
tissues, even if one artery
becomes blocked. Veins
have less collateral
circulation compared to
arteries.
Blood: Blood is a connective tissue which plays the role of the carrier for various substances in
the body. Blood is composed of 1. Plasma 2. Blood cells 3. Platelets.
Blood plasma: Blood plasma is a pale coloured liquid which is mostly composed of water.
Blood plasma forms the matrix of blood.
Bloods cells: There are two types of blood cells, viz. Red Blood Cells (RBCs) and White
Blood Cells (WBCs).
(a) Red Blood Corpuscles (RBCs): These are of red colour because of the presence of
haemoglobin which is a pigment. Haemoglobin readily combines with oxygen and carbon
dioxide. The transport of oxygen happens through haemoglobin. Some part of carbon
dioxide is also transported through haemoglobin.
(b) White Blood Corpuscles (WBCs): These are of pale white colour. They play important
role in the immunity.
Platelets: Platelets are responsible for blood coagulation. Blood coagulation is a defense
mechanism which prevents excess loss of blood, in case of an injury.
Lymph:
Lymph is similar to blood but RBCs are absent in lymph.
Lymph is formed from the fluid which leaks from blood capillaries and goes to the
intercellular space in the tissues. This fluid is collected through lymph vessels and finally
return to the blood capillaries.
Lymph also plays an important role in the immune system.
Lymph a yellowish fluids escape from the blood capillaries into the intercellular spaces
contain less proteins than blood.
Lymph flows from the tissues to the heart assisting in transportation and destroying germs.
Double circulation: In the human heart, blood
passes through the heart twice in one cardiac
cycle. This type of circulation is called double
circulation. One complete heartbeat in which all
the chambers of the heart contract and relax once
is called cardiac cycle. The heart beats about 72
times per minute in a normal adult. In one cardiac
cycle, the heart pumps out 70 mL blood and thus,
about 4900 mL blood in a minute. Double
circulation ensures complete segregation of
oxygenated and deoxygenated blood which is
necessary for optimum energy production in
warm-blooded animals.
Transportation in plants: Plants have
specialized vascular tissues for transportation of substances. There are two types of vascular
tissues in plants.
Xylem: Xylem is responsible for transportation of water and minerals. It is composed of
trachids, xylem vessels, and xylem parenchyma and xylem fibre. Tracheids and xylem
vessels are the conducting elements. The xylem makes a continuous tube in plants which
runs from roots to stem and right up to the veins of leaves.
Carry water and minerals from the leaves to the other part of the plant.
Phloem: Phloem is responsible for transportation of food. Phloem is composed of sieve
tubes, companion cells, phloem parenchyma and Phloem fibers. Sieve tubes are the
conducting elements in phloem.
Carries product of photosynthesis from roots to other part of the plant.
Transportation in plants
Ascent of sap: The upward
movement of water and minerals from roots to different plant parts is called ascent of sap. Many
factors are at play in ascent of sap and it takes place in many steps. They are explained as
follows:
Root pressure: The walls of cells of root hairs are very thin. Water from soil enters the
root hairs because of osmosis. Root pressure is responsible for movement of water up to
the base of the stem.
Capillary action: A very fine tube is called capillaiy, water, or any liquid rises in the
capillary because of physical forces and this phenomenon is called capillary action. Water,
in stem, rises up to some height because of capillaiy action.
Adhesion-cohesion of water molecules: Water molecules make a continuous column in
the xylem because of forces of adhesion and cohesion among the molecules.
Transpiration pull: Loss of water vapour through stomata and lenticels, in plants, is
called transpiration. Transpiration through stomata creates vacuum which creates suction,
called transpiration pull. The transpiration pull sucks the water column from the xylem
tubes and thus, water is able to rise to great heights in even the tallest plants.
Transport of food: Transport of food in plants happens because of utilization of energy.
Thus, unlike the transport through xylem, it is a form of active transport. Moreover, the
flow of substances through phloem takes place in both directions, i.e., it is a two-way
traffic in phloem.
Transpiration is the process of loss of water as vapour from aerial parts of the plant.
Functions
Absorption and upward movement of water and minerals by creating pull.
Helps in temperature regulation in plant.
Transport of food from leaves (food factory) to different parts of the plant is called
Translocation.
