Transportation — Class 10 Biological Science
"Your heart beats 100,000 times a day, pumping 7,500 litres of blood. It never rests. It never takes a holiday. It is the most dedicated pump ever built."
1. The Need for Transportation
Every cell needs OXYGEN and NUTRIENTS. Every cell produces WASTE (CO₂, urea). Transportation CONNECTS supply to demand. In complex multicellular organisms, DIFFUSION ALONE is too slow — a dedicated transport system is ESSENTIAL.
2. The Human Heart — The Pump
Structure
Four chambers: Right Atrium. Right Ventricle. Left Atrium. Left Ventricle. The atria are RECEIVING chambers (thin walls). The ventricles are PUMPING chambers (thick walls — especially the LEFT ventricle, which pumps blood to the ENTIRE BODY).
Valves — One-Way Doors
Tricuspid (right atrium → right ventricle). Bicuspid/Mitral (left atrium → left ventricle). Pulmonary and Aortic semilunar valves (ventricles → arteries). 'Valves prevent BACKFLOW. The "lub-dub" sound of the heart is the valves CLOSING.'
Double Circulation
Blood passes through the heart TWICE in one complete circuit. Pulmonary Circulation: Right Ventricle → Pulmonary Artery → LUNGS (picks up O₂, releases CO₂) → Pulmonary Vein → Left Atrium. Systemic Circulation: Left Ventricle → Aorta → BODY (delivers O₂, collects CO₂) → Vena Cava → Right Atrium.
'Double circulation ensures: oxygenated and deoxygenated blood NEVER MIX. All blood to the body is FULLY OXYGENATED.'
Cardiac Cycle (~0.8 seconds)
Systole (contraction — 0.3s): Ventricles contract → blood pumped OUT. Diastole (relaxation — 0.5s): Chambers relax → blood flows IN. Heart rate ~72 beats/min. 'The heart is actually RESTING (diastole) for MORE time than it's working (systole).'
Pacemaker — The SA Node
Sinoatrial Node in the right atrium generates electrical impulses → atria contract → AV Node → Bundle of His → Purkinje fibres → ventricles contract. 'The SA node sets the RHYTHM. It's why your heart beats REGULARLY without you thinking about it.'
3. Blood Vessels
| Type | Structure | Function | Key Feature |
|---|---|---|---|
| Artery | Thick, ELASTIC, muscular walls | Carries blood AWAY from heart | Withstands HIGH pressure. Except: pulmonary artery carries O₂-POOR blood. |
| Vein | Thinner walls. Have VALVES. | Carries blood TO heart | Valves prevent BACKFLOW. Except: pulmonary vein carries O₂-RICH blood. |
| Capillary | ONE cell thick wall | EXCHANGE of O₂, CO₂, nutrients, waste | Tiny. Network connects arteries to veins. |
4. Blood Components
| Component | Function | Key Detail |
|---|---|---|
| RBCs (Erythrocytes) | O₂ transport via HAEMOGLOBIN | NO nucleus (in mammals). Biconcave shape — more surface area. ~120 day lifespan. Made in BONE MARROW. |
| WBCs (Leukocytes) | IMMUNITY — fight infection | Several types (neutrophils, lymphocytes). Can LEAVE blood vessels. |
| Platelets (Thrombocytes) | BLOOD CLOTTING | Cell fragments. Release clotting factors. |
| Plasma (55% of blood) | Liquid transport | 90% water. Carries: nutrients, hormones, CO₂ (as bicarbonate), urea, proteins. |
Blood Groups (ABO System)
A, B, AB, O. Determined by antigens on RBCs. Universal donor: O−. Universal recipient: AB+.
5. Transportation in Plants
| Feature | XYLEM | PHLOEM |
|---|---|---|
| Transports | WATER + MINERALS | FOOD (sucrose) |
| Direction | ONE-WAY (roots → leaves) | TWO-WAY (source → sink) |
| Cells | DEAD (tracheids, vessels) | LIVING (sieve tubes, companion cells) |
| Driving Force | TRANSPIRATION PULL (passive) | Active transport (uses ENERGY — ATP) |
Transpiration Pull
Water evaporates from leaves through STOMATA → creates NEGATIVE PRESSURE (suction) → pulls water UP through xylem. 'Cohesion (water molecules stick together) + Adhesion (water sticks to xylem walls) + Transpiration = the COHESION-TENSION THEORY.'
6. Common Mistakes
- 'All arteries carry oxygenated blood' — WRONG. Pulmonary artery carries DEOXYGENATED blood to lungs.
- 'All veins carry deoxygenated blood' — WRONG. Pulmonary vein carries OXYGENATED blood from lungs.
- 'Xylem is living' — Xylem cells are DEAD at maturity. Phloem cells are LIVING.
- 'Heart is on the left side' — The heart is in the CENTRE, tilted slightly LEFT.
7. AP SSC Exam Focus
| Topic | Marks |
|---|---|
| Heart structure (diagram) | 4-5 |
| Double circulation | 3-4 |
| Blood vessels comparison | 3-4 |
| Xylem vs Phloem | 3-4 |
| Blood components | 2-3 |
8. Heart Structure — Detailed Four-Chamber View
'The human heart has FOUR chambers. This is a KEY feature that distinguishes mammals and birds from reptiles and amphibians (which have 3-chambered hearts). Four chambers ensure COMPLETE SEPARATION of oxygenated and deoxygenated blood.'
The Four Chambers
Right Atrium (Upper right chamber): RECEIVES deoxygenated blood from the body via TWO large veins — SUPERIOR VENA CAVA (from upper body) and INFERIOR VENA CAVA (from lower body). 'Think: Right side = DEOXYGENATED blood (blue in diagrams).'
Right Ventricle (Lower right chamber): PUMPS deoxygenated blood to the lungs via the PULMONARY ARTERY. 'The right ventricle has MODERATELY thick walls — it only needs enough force to send blood to the nearby lungs.'
Left Atrium (Upper left chamber): RECEIVES oxygenated blood from the lungs via FOUR PULMONARY VEINS (two from each lung). 'Think: Left side = OXYGENATED blood (red in diagrams).'
Left Ventricle (Lower left chamber): PUMPS oxygenated blood to the ENTIRE BODY via the AORTA. 'The left ventricle has the THICKEST walls — it must generate enough PRESSURE to push blood to the farthest parts of the body (toes, fingers, brain). This is why left ventricular failure is so serious.'
Valves — The One-Way Doors
Atrioventricular (AV) Valves: Tricuspid (right side — three flaps) and Bicuspid/Mitral (left side — two flaps). Open when atria contract → blood flows to ventricles. Close when ventricles contract → prevents BACKFLOW into atria. Semilunar Valves: Pulmonary valve (right ventricle → pulmonary artery). Aortic valve (left ventricle → aorta). Open when ventricles contract. Close to prevent blood flowing BACK into the ventricles. '"Lub-dub": The "lub" is the sound of AV valves CLOSING (ventricles contract). The "dub" is the sound of semilunar valves CLOSING (ventricles relax).'
9. Double Circulation — The Complete Pathway
'Blood passes through the heart TWO TIMES in one complete circuit. This is DOUBLE CIRCULATION. It is MORE EFFICIENT than single circulation (found in fish).'
Deoxygenated Blood Pathway (Blue — CO₂-rich)
Body tissues → Vena Cava → Right Atrium → Tricuspid Valve → Right Ventricle → Pulmonary Valve → Pulmonary Artery → LUNGS (CO₂ released, O₂ picked up)
Oxygenated Blood Pathway (Red — O₂-rich)
LUNGS → Pulmonary Vein → Left Atrium → Bicuspid Valve → Left Ventricle → Aortic Valve → AORTA → Body tissues
Why Double Circulation Matters
'In fish (single circulation): blood passes through the heart ONCE per circuit. Blood goes: heart → gills → body → heart. Pressure drops at the gills → blood moves slowly through the body. In humans (double circulation): blood returns to the heart AFTER the lungs → gets a SECOND PUMP → HIGH PRESSURE → blood reaches every cell QUICKLY.'
10. Blood Vessels — Detailed Comparison
Arteries — The Pressure Vessels
- Thick, MUSCULAR, ELASTIC walls (three layers: endothelium, smooth muscle, connective tissue).
- CARRY blood AWAY from the heart.
- HIGH PRESSURE — blood surges with each heartbeat.
- NO VALVES (pressure is high enough to prevent backflow).
- PULSE can be felt (expansion of artery with each heartbeat).
- ALL arteries carry OXYGENATED blood EXCEPT: PULMONARY ARTERY (carries deoxygenated blood to lungs).
Arterioles
Smaller branches of arteries. Have SOME smooth muscle — can CONSTRICT or DILATE to control blood flow to different body parts. 'During exercise: arterioles supplying muscles DILATE (more blood flow). Arterioles supplying digestive system CONSTRICT (less blood flow).'
Veins — The Return Vessels
- Thinner, LESS MUSCULAR walls.
- CARRY blood TOWARD the heart.
- LOW PRESSURE — blood flows relatively slowly.
- HAVE VALVES — prevent BACKFLOW (blood must often flow AGAINST GRAVITY from legs back to heart).
- Visible as 'blue lines' under the skin.
- ALL veins carry DEOXYGENATED blood EXCEPT: PULMONARY VEIN (carries oxygenated blood from lungs).
Capillaries — The Exchange Vessels
- WALLS are ONE CELL THICK (endothelium only).
- DIAMETER is just wide enough for a SINGLE RBC to squeeze through.
- This is WHERE the actual exchange happens: O₂, CO₂, nutrients, waste, hormones all cross the capillary wall by DIFFUSION.
- The capillary network is MASSIVE — if all capillaries in the body were laid end to end, they would stretch ~100,000 km!
- 'Capillaries are where the circulatory system DOES its job. Everything else — heart, arteries, veins — is just TRANSPORT to and from the capillaries.'
11. Blood Pressure — The Force of Blood
'Blood pressure is the PRESSURE exerted by blood against the walls of blood vessels — particularly arteries. It is measured using a SPHYGMOMANOMETER.'
Systolic Pressure: Pressure during VENTRICULAR CONTRACTION (systole). Normal: ~120 mm Hg. Diastolic Pressure: Pressure during VENTRICULAR RELAXATION (diastole). Normal: ~80 mm Hg.
'Blood pressure is written as: 120/80 mm Hg (systolic/diastolic).'
Factors affecting BP: Age (increases with age). Stress (increases). Exercise (temporary increase, then decrease). Diet (high salt → higher BP). Weight (obesity → higher BP).
Hypertension (High BP) : >140/90. Risk factor for: heart attack, stroke, kidney damage. Hypotension (Low BP) : <90/60. Can cause dizziness, fainting.
12. Lymph — The Second Circulatory System
'Lymph is a COLOURLESS fluid that circulates in the LYMPHATIC SYSTEM. It is essentially the SAME as blood plasma — but with FEWER proteins and NO RBCs.'
Formation: Some fluid LEAKS out of capillaries into the intercellular spaces (tissue fluid). This fluid bathes the cells — provides O₂ and nutrients, collects CO₂ and waste. About 90% of this fluid returns directly to the capillaries. The remaining 10% enters LYMPHATIC CAPILLARIES → becomes LYMPH.
Lymph Nodes: Small, bean-shaped structures along lymphatic vessels. FILTER lymph → trap bacteria, viruses, and cancer cells. Contain LYMPHOCYTES (a type of WBC) → fight infections.
Functions of the Lymphatic System:
- Returns INTERSTITIAL FLUID to the blood (prevents swelling/oedema).
- Transports DIGESTED FATS from the small intestine to the blood (via lacteals in intestinal villi).
- Plays a role in IMMUNITY (lymph nodes produce and store lymphocytes).
13. Transportation in Plants — Detailed
Xylem — The Water-Transport System
Structure: Made of DEAD cells at maturity (no cytoplasm — just hollow tubes). TWO types of conducting cells: TRACHEIDS (long, tapered cells — water moves through pits) and VESSELS (shorter, wider — water moves through perforated end walls — more efficient). Also contains: XYLEM PARENCHYMA (living — storage) and XYLEM FIBRES (structural support).
Driving Force — Transpiration Pull: Water evaporates from leaf cells → creates a NEGATIVE PRESSURE → water is pulled UP from the xylem in the roots. 'This is a purely PHYSICAL process — no energy is needed. It is driven by the SUN (which causes evaporation).'
Cohesion-Tension Theory:
- Water evaporates from SPONGY MESOPHYLL cells into air spaces → exits through STOMATA (transpiration).
- Water potential in leaf cells DECREASES → water moves from XYLEM into leaf cells.
- This creates TENSION (negative pressure) in the xylem.
- Water molecules are COHESIVE (stick to each other via HYDROGEN BONDS) → the entire water column is pulled upward.
- Water is also ADHESIVE (sticks to xylem walls) → helps pull water up narrow xylem vessels.
- Water enters roots from soil by OSMOSIS → continues upward.
Phloem — The Food-Transport System
Structure: Made of LIVING cells. SIEVE TUBE ELEMENTS (main conducting cells — have perforated SIEVE PLATES at ends for flow between cells). COMPANION CELLS (living — provide metabolic support and ATP — connected to sieve tubes through PLASMODESMATA).
Translocation — Movement of Food: Food (sucrose) is transported from SOURCE (where it is produced or stored) to SINK (where it is used or stored). Sources: leaves (photosynthesis), storage organs (potato tuber, carrot root during sprouting). Sinks: growing roots, developing fruits and seeds, young leaves.
Pressure Flow Hypothesis (Münch's Hypothesis) :
- At the SOURCE: sucrose is loaded into phloem sieve tubes by ACTIVE TRANSPORT (requires ATP).
- Higher sucrose concentration in phloem → WATER enters from xylem by OSMOSIS.
- Increased water volume → INCREASED PRESSURE in phloem.
- The pressure difference drives the sucrose solution toward the SINK (where pressure is lower).
- At the SINK: sucrose is UNLOADED → used or stored → water returns to xylem.
'Xylem is PASSIVE (powered by the sun). Phloem is ACTIVE (requires ATP from companion cells).'
14. Common Mistakes (Additional)
- 'All arteries are red and all veins are blue' — Blood is ALWAYS RED (when oxygenated, bright red; when deoxygenated, dark red). Veins appear BLUEISH through the skin because of how LIGHT penetrates tissue.
- 'Pulse is felt where blood flows in veins' — Pulse is felt in ARTERIES (the expansion of the arterial wall with each heartbeat). Veins have NO pulse.
- 'Lymph is the same as blood' — Lymph is DIFFERENT: it has NO RBCs, fewer proteins, and fewer platelets. It circulates in the LYMPHATIC SYSTEM (separate from blood circulation).
15. Self-Test Questions
- Draw a labelled diagram of the HUMAN HEART showing all four chambers and valves.
- Explain DOUBLE CIRCULATION. Draw a flowchart of the complete pathway.
- Differentiate between ARTERIES, VEINS, and CAPILLARIES (4 points).
- What is BLOOD PRESSURE? Differentiate between systolic and diastolic pressure.
- What is LYMPH? What are its THREE functions?
- Differentiate between XYLEM and PHLOEM (5 points).
- Explain the COHESION-TENSION THEORY of water transport in plants.
- Describe the PRESSURE FLOW HYPOTHESIS for translocation of food in phloem.
- Why is the LEFT VENTRICLE thicker than the right ventricle?
- Name the FOUR components of blood with their functions.
Answers to Selected Questions: Q9: The left ventricle pumps blood to the ENTIRE BODY — it needs more MUSCLE to generate HIGH PRESSURE. The right ventricle only pumps to the LUNGS — needs less pressure. Q10: RBCs (O₂ transport), WBCs (immunity), Platelets (clotting), Plasma (liquid transport of nutrients, hormones, waste, CO₂).
