Transportation 🚗🩸
I. Introduction to Transportation (Life Process)
Transportation is a vital life process in which essential materials are moved within an organism's
body. In multicellular organisms like humans and plants, there is a regular demand for
substances such as food, oxygen, water, minerals, and the removal of waste products.
Specialized transport systems fulfill this function, ensuring that all cells receive necessary
nutrients and dispose of metabolic by-products to maintain life and proper functioning.
II. Transportation in Human Beings: The
Circulatory System
The human circulatory system is a complex network responsible for the internal transport of
substances. It consists of:
● A Pumping Organ: The Heart
● Blood Vessels: Arteries, Veins, and Capillaries
● A Circulatory Medium: Blood and Lymph
A. The Heart: The Pumping Organ
The heart is a muscular organ, roughly the size of your clenched fist, situated in the chest cavity,
slightly tilted to the left. Its continuous rhythmic contraction and relaxation, known as the
cardiac cycle, ensures the constant circulation of blood throughout the body.
1. Structure of the Heart
● Chambers: The human heart has four chambers:
○ Two Upper Chambers: Right Atrium (RA) and Left Atrium (LA), also called
auricles.
○ Two Lower Chambers: Right Ventricle (RV) and Left Ventricle (LV).
● Septum: A dividing wall separates the right and left sides of the heart, preventing the
mixing of oxygenated and deoxygenated blood.
● Valves: Located between the chambers and at the exits of the ventricles, valves prevent
the backflow of blood, ensuring its one-way flow.
2. Working of the Human Heart (Double Circulation)
The human circulatory system is a double circulatory system, meaning blood passes through
the heart twice in one complete cycle. This ensures efficient delivery of oxygen to the body.
● Pulmonary Circulation (Heart-Lungs-Heart):
1. Deoxygenated blood (rich in CO_{2}) from the body (via the Vena Cava from
upper and lower body) enters the Right Atrium.
2. From the Right Atrium, blood moves into the Right Ventricle.
3. The Right Ventricle pumps this deoxygenated blood to the lungs via the
Pulmonary Artery.
4. In the lungs, blood releases CO_{2} and picks up O_{2} (it gets oxygenated).
● Systemic Circulation (Heart-Body-Heart):
1. Oxygenated blood from the lungs is brought back to the Left Atrium via the
Pulmonary Veins.
2. From the Left Atrium, blood moves into the Left Ventricle.
3. The Left Ventricle, which has thicker muscular walls, pumps this oxygenated blood
to the rest of the body through the largest artery, the Aorta.
4. Oxygenated blood is then delivered to all body organs.
B. Blood Vessels
Blood vessels are a network of tubes that carry blood throughout the body.
1. Arteries:
○ Carry oxygenated blood away from the heart to various body parts (except the
pulmonary artery, which carries deoxygenated blood to the lungs).
○ Have thick, elastic walls to withstand the high pressure of blood pumped directly
from the heart.
○ Do not have valves (except at their origin from the heart).
2. Veins:
○ Carry deoxygenated blood from various body parts back to the heart (except the
pulmonary vein, which carries oxygenated blood from the lungs to the heart).
○ Have thinner walls than arteries as blood pressure is lower.
○ Contain valves to prevent the backflow of blood, especially against gravity.
3. Capillaries:
○ Are the smallest and thinnest blood vessels (one cell thick).
○ Form a network connecting arteries (arterioles) to veins (venules).
○ This is the primary site for the exchange of gases (oxygen, carbon dioxide),
nutrients, and waste products between blood and body cells.
C. Blood: The Circulatory Medium
Blood is a fluid connective tissue that circulates throughout the body, performing various crucial
functions.
1. Components of Blood
● Plasma:
○ The fluid matrix of blood, primarily composed of water.
○ Transports food, carbon dioxide, nitrogenous wastes, hormones, and salts in
dissolved form.
○ Also transports proteins, digested food, common salt, and urea.
● Red Blood Cells (RBCs) / Erythrocytes:
○ Contain hemoglobin, a red pigment that binds with oxygen.
○ Responsible for transporting oxygen from the lungs to all body tissues.
○ Also transport some carbon dioxide from tissues back to the lungs.
● White Blood Cells (WBCs) / Leucocytes:
○ Are the body's defense mechanism.
○ Fight against infection and foreign invaders.
● Platelets:
○ Cell fragments responsible for blood clotting.
○ Prevent excessive blood loss in case of injury.
2. Functions of Blood
● Transportation: Carries oxygen, nutrients, hormones, and enzymes to body cells.
● Waste Removal: Transports metabolic waste products (like carbon dioxide and urea) to
excretory organs.
● Defense: Protects the body against infections and diseases.
● Regulation: Helps regulate body temperature.
D. Lymphatic System
The lymphatic system is a parallel system to the circulatory system, playing a crucial role in
immunity and fluid balance.
● Lymph (Tissue Fluid):
○ A yellowish fluid that escapes from the pores present in the walls of capillaries
during blood circulation.
○ It contains plasma, proteins, and blood cells.
○ It lacks red blood cells (RBCs) and large proteins.
● Formation and Function:
○ Some amount of plasma, proteins, and blood cells filter out through the small pores
present in the walls of capillaries into the intercellular spaces to form tissue fluid or
lymph.
○ Lymph drains into lymphatic capillaries, forming the lymphatic system.
○ It carries digested and absorbed fat from the intestine.
○ It drains excess fluid from the intercellular space back into the blood, preventing
swelling.
○ It contains lymphocytes (a type of WBC), which fight infection.
III. Transportation in Plants
Plants also require a system for transporting water, minerals, and food throughout their body.
A. Materials Transported
● Oxygen and Carbon Dioxide: Exchanged with the atmosphere.
● Water and Minerals: Absorbed from the soil.
● Food (glucose, sucrose): Produced during photosynthesis.
● Hormones: For growth and development.
● Wastes: Metabolic by-products.
B. Mechanisms of Short-Distance Transportation
For short distances between plant cells, water and nutrients can move through:
● Diffusion: Movement of particles from a region of higher concentration to a region of
lower concentration, without the need for a membrane.
● Osmosis: Movement of solvent (usually water) from a region of lower solute
concentration to a region of higher solute concentration through a semi-permeable
membrane.
C. Vascular Tissues: Xylem and Phloem
Plants have specialized vascular tissues for long-distance transport:
1. Xylem:
○ Function: Transports water and dissolved minerals from the roots upwards to all
aerial parts of the plant.
○ Flow: Unidirectional (one-way flow).
○ Structure: Composed of dead cells with no end walls between them, forming
continuous tubes. Their walls are stiffened with lignin, providing structural support
to the plant.
2. Phloem:
○ Function: Transports photosynthesis products (food), primarily sugars like
sucrose, from the leaves (where food is made) to other parts of the plant, including
storage organs and growing regions.
○ Flow: Bidirectional (two-way flow), allowing food to move both upwards and
downwards.
○ Structure: Composed of living cells (sieve tubes) with end walls that have
perforations (sieve plates).
D. Transpiration
● Definition: The process of water vapor loss from the aerial parts of a plant, primarily
through stomata in leaves.
● Transpiration Pull / Suction Pull: The continuous evaporation of water from the leaves
creates a "pulling force" or suction force in the xylem. This force draws water from the
roots up to the top of the plant, even against gravity.
● Functions of Transpiration:
○ Helps in the absorption and upward movement of water and dissolved minerals
from the soil to the leaves.
○ Regulates plant temperature by evaporative cooling.
○ Aids in removing excess water from the plant.
