:) TRANSPORTATION:- 

-> Transportation is the process by which water, nutrients, respiratory gases, hormones, and waste products are transported to and from cells and tissues.

-> In simple words, the transport system ensures that every cell receives the substances it needs and that metabolic wastes are efficiently removed.

-> In humans, transport is primarily carried out by the circulatory and lymphatic systems, whereas in plants, it occurs mainly through the xylem and phloem.

* Human Circulatory System:-

-> Humans have a closed, double circulatory system: 

Q. Why is double circulation important? 

-> It keeps oxygenated and deoxygenated blood largely separate, allowing efficient oxygen delivery to body tissues.

* The Heart:-

-> The heart is a muscular, hollow organ that acts as a pump to maintain continuous blood circulation.

. Four chambers of the heart

Imp:-  The left ventricle has the thickest muscular wall because it has to pump blood throughout the body.

. Valves of the heart

-> Valves ensure that blood flows in one direction and prevents backflow.

• Tricuspid valve: Between right atrium and right ventricle.
• Bicuspid/Mitral valve: Between left atrium and left ventricle.
• Pulmonary semilunar valve: Between right ventricle and pulmonary artery.
• Aortic semilunar valve: Between left ventricle and aorta.

* LYMPHATIC SYSTEM

-> The lymphatic system is a secondary transport and defence system that works alongside the circulatory system.

-> Its major functions include:

• Returning excess tissue fluid to the bloodstream.
• Transporting absorbed dietary fats.
• Supporting immune defence.
• Providing a pathway for lymphocytes and other immune cells.

. Pathway of lymph

Tissue fluid → lymph capillaries → lymph vessels → lymph ducts → subclavian veins → bloodstream

1) Lymph nodes- Lymph nodes act as filters for lymph and contain immune cells where immune responses can be initiated.

2) Thoracic duct - The thoracic duct is the largest lymphatic vessel and drains lymph from most of the body into the bloodstream near the left subclavian vein.

3) Lacteals - Lacteals are specialised lymphatic capillaries present in the intestinal villi. They absorb dietary lipids, particularly lipids packaged into chylomicrons, and transport them through the lymphatic system.

* BLOOD: COMPOSITION AND FUNCTIONS

-> Blood is a specialised connective tissue consisting of a fluid matrix called plasma and formed elements.

-> It can broadly be divided into:

Blood = Plasma + Formed elements

The formed elements include:

1. Red blood cells
2. White blood cells
3. Platelets

1. Plasma

-> Plasma makes up approximately 55% of blood.

-> It is a pale, straw-coloured fluid containing approximately 90–92% water, along with:

• Plasma proteins
• Electrolytes
• Nutrients
• Hormones
• Dissolved gases
• Waste products

Important plasma proteins

• Albumin: Helps maintain osmotic pressure.
• Globulins: Include transport and immune proteins.
• Fibrinogen: Important for blood clotting.

Functions of plasma

• Transports nutrients and hormones.
• Carries metabolic wastes.
• Helps maintain osmotic balance.
• Contains clotting proteins.
• Contains antibodies and other immune components.

 2. Red Blood Cells

-> Red blood cells, or erythrocytes, are specialised cells responsible mainly for gas transport.

Features

• Biconcave disc-shaped.
• Mature human RBCs lack a nucleus.
• Contain haemoglobin.
• Approximately 4.5–5.5 million cells/µL of blood in adults, with normal ranges varying by sex, age, and laboratory.

Functions of RBCs

1) Oxygen transport: Haemoglobin binds oxygen to form oxyhaemoglobin.

2) Carbon dioxide transport: A portion of CO₂ binds to haemoglobin to form carbaminohaemoglobin. Most CO₂, however, is transported in blood as bicarbonate ions. RBCs also contribute to maintaining the acid–base balance of blood.

3) White Blood Cells:  White blood cells, or leucocytes, are nucleated blood cells involved in immunity and defence.

-> Normal adult WBC counts are approximately 5,000–10,000 cells/µL, although reference ranges vary.

. Five major types

1. Neutrophils – Important in phagocytosis and acute inflammation.
2. Eosinophils – Associated with allergic responses and defence against certain parasites.
3. Basophils – Release mediators such as histamine during inflammatory and allergic responses.
4. Monocytes – Can enter tissues and differentiate into macrophages and other phagocytic cells.
5. Lymphocytes – Include B cells, T cells, and natural killer cells.

. Major functions

• Defence against pathogens.
• Phagocytosis.
• Antibody production by B lymphocytes.
• Cell-mediated immunity through T lymphocytes.
• Coordination of immune responses.

 3. Platelets

-> Platelets, or thrombocytes, are small cell fragments derived from megakaryocytes.

-> Normal platelet counts are approximately 150,000–400,000/µL.

Functions

• Help stop bleeding.
• Form a platelet plug at the site of injury.
• Participate in the blood-clotting process.
• Release substances involved in haemostasis and wound repair.

 4. BLOOD VESSELS

-> Blood vessels form a continuous network through which blood travels.

Important point:-

-> Arteries do not always carry oxygenated blood, and veins do not always carry deoxygenated blood.

For example:

• Pulmonary artery: Carries deoxygenated blood from heart → lungs.
• Pulmonary veins: Carry oxygenated blood from lungs → heart.

* TRANSPORTATION IN PLANTS

-> Plants also need an efficient transport system because their roots, stems, leaves and other organs are located at different positions.

-> Plants mainly use two vascular tissues:

Xylem → Water + minerals

Phloem → Organic nutrients

* XYLEM:-

-> Xylem transports water and dissolved mineral ions mainly from the roots towards the leaves.

-> Main conducting cells: Tracheids, Vessel elements

-> These cells are generally dead at maturity and have thick, lignified walls that provide mechanical support.

-> Direction of transport ; Roots → Stem → Leaves

-> The movement of water through xylem is predominantly upward, although xylem can also participate in lateral movement of water.

. Mechanism:-

The major driving force for long-distance water movement is the transpiration pull, explained by the cohesion-tension mechanism.

* TRANSPIRATION:-

-> Transpiration is the loss of water vapour from the aerial parts of plants, mainly through the stomata of leaves.

-> When water evaporates from leaf surfaces, it creates negative pressure (tension) in the leaf xylem. Because water molecules are held together by cohesion, this tension is transmitted down the continuous water column in the xylem.

Importance of transpiration:

1) Helps transport water from roots to leaves.

2) Facilitates movement of mineral ions.

3) Helps cool the plant.

4) Contributes to maintaining water movement through the plant.

* PHLOEM:-

-> Phloem transports organic nutrients, especially sucrose, from regions where they are produced or released (sources) to regions where they are used or stored (sinks).

-> Main conducting cells- Sieve tube elements, Companion cells

-> Unlike mature xylem conducting elements, sieve tube elements are living cells, although they lack a nucleus at maturity and depend on companion cells for many metabolic functions.

-> Direction of transport : Phloem transport can occur in different directions in different sieve tubes, depending on the locations of sources and sinks.

For example:

Mature leaf → growing root

Storage organ → developing fruit

. Mechanism

-> Long-distance phloem transport is explained by the pressure-flow hypothesis (mass-flow hypothesis).

Transportation is an essential life process that maintains the continuous movement of water, nutrients, gases, hormones and wastes, ensuring that cells and tissues receive the materials necessary for survival and proper functioning.