“Transport: Circulatory System”

🟢 Lite — Quick Review (1h–1d)

Rapid summary for last-minute revision before your WAEC exam.

Transport Systems in Living Organisms:

Organism	Transport System	Medium
Amoeba	Diffusion	Cytoplasm
Hydra	Diffusion through cells	Body surface
Earthworm	Closed circulatory system	Blood in vessels
Insects	Open circulatory system	Haemolymph in body cavity
Fish	Single closed circulatory system	Blood in vessels
Mammals	Double closed circulatory system	Blood

Double Circulation (Mammals):

• Pulmonary circuit: Heart → Lungs → Heart (oxygenation)
• Systemic circuit: Heart → Body → Heart (nutrient/O₂ delivery)

The Heart:

Chamber	Function
Right atrium	Receives deoxygenated blood from body
Right ventricle	Pumps blood to lungs
Left atrium	Receives oxygenated blood from lungs
Left ventricle	Pumps blood to body (thickest wall)

Blood Flow Through the Heart: Superior/inferior vena cava → Right atrium → Tricuspid valve → Right ventricle → Pulmonary valve → Pulmonary artery → Lungs → Pulmonary veins → Left atrium → Bicuspid (mitral) valve → Left ventricle → Aortic valve → Aorta → Body

Valves:

• Tricuspid (right AV valve) — 3 flaps
• Bicuspid/mitral (left AV valve) — 2 flaps
• Semilunar valves — prevent backflow into ventricles

⚡ WAEC Tip: Remember the sequence: RA → RV → lungs → LA → LV → body. The left ventricle has the thickest wall because it pumps blood the farthest (around the entire body).

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🟡 Standard — Regular Study (2d–2mo)

For students who want genuine understanding.

Blood Vessels:

Vessel	Function	Structure
Arteries	Carry blood from heart	Thick muscular walls, small lumen, high pressure
Veins	Carry blood to heart	Thin walls, valves, large lumen, low pressure
Capillaries	Site of exchange	One cell thick, very narrow

Artery vs Vein:

• Arteries have thick tunica media (smooth muscle + elastic tissue)
• Veins have valves to prevent backflow
• Blood in arteries is usually oxygenated (except pulmonary)
• Blood in veins is usually deoxygenated (except pulmonary)

Blood Composition:

Component	Function	Normal Count
Plasma (55%)	Transport medium	-
Red blood cells	Carry oxygen	4.5-6.0 million/mm³
White blood cells	Fight infection	4,000-11,000/mm³
Platelets	Blood clotting	150,000-400,000/mm³

Plasma Contents:

• Water (~90%)
• Proteins (albumin, globulins, fibrinogen)
• Nutrients (glucose, amino acids, lipids)
• Waste products (urea, creatinine)
• Hormones
• Dissolved gases (O₂, CO₂)

Blood Groups (ABO System):

Group	Antigens on RBC	Antibodies in plasma
A	A antigen	Anti-B
B	B antigen	Anti-A
AB	A and B antigens	Neither
O	Neither antigen	Both Anti-A and Anti-B

Rhesus Factor (Rh):

• Rh positive (Rh+): Has D antigen
• Rh negative (Rh-): No D antigen
• Problem: Rh- mother with Rh+ baby → mother produces anti-D antibodies (Haemolytic Disease of the Newborn)

Blood Clotting (Coagulation):

1. Damaged tissue releases thromboplastin
2. Thromboplastin + Ca²⁺ + Prothrombin → Thrombin
3. Thrombin + Fibrinogen → Fibrin
4. Fibrin forms mesh that traps blood cells → CLOT

Vitamin K is needed for prothrombin synthesis. Calcium is essential for clotting cascade.

⚡ Common Mistake: Students confuse thrombosis (abnormal clot inside blood vessel) with haemostasis (normal clotting to prevent blood loss after injury). A thrombus can cause heart attacks or strokes if it blocks coronary or cerebral arteries.

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🔴 Extended — Deep Study (3mo+)

Comprehensive theory for serious exam preparation.

Cardiac Cycle:

Phase	Ventricles	AV valves	SL valves
Atrial systole	Relaxed	Open	Closed
Ventricular systole (isovolumetric)	Contracting	Closed	Closed
Ventricular systole (ejection)	Contracting	Closed	Open
Diastole	Relaxed	Open	Closed

Heart Sounds:

• First sound (LUB): AV valves closing
• Second sound (DUB): Semilunar valves closing

ECG (Electrocardiogram):

Wave	Represents
P wave	Atrial depolarisation
QRS complex	Ventricular depolarisation
T wave	Ventricular repolarisation

• P-Q interval: Time for impulse to travel from SA node to ventricles
• Abnormal ECG indicates heart conditions

Heart Rate Regulation:

• SA node (pacemaker) sets intrinsic rate ~70 bpm
• Sympathetic nerves: increase heart rate (fight or flight)
• Parasympathetic (vagus nerve): decrease heart rate (rest)
• Adrenaline: increases heart rate and force of contraction

Blood Pressure:

Systolic pressure: Maximum during ventricular systole (~120 mmHg) Diastolic pressure: Minimum during ventricular diastole (~80 mmHg)

Blood pressure = Systolic/Diastolic = e.g., 120/80 mmHg

Factors Affecting Blood Flow:

• Blood pressure gradient (main driver)
• Resistance (mainly in arterioles)
• Blood viscosity (thick blood = harder to pump)
• Vessel radius (small change causes large change in flow)

Lymphatic System:

• Drains excess tissue fluid back to blood
• Lymph nodes filter pathogens
• Contains lymphocytes (WBCs)
• No pump — relies on muscle contractions

Coronary Heart Disease:

• Coronary arteries supply heart muscle
• Atherosclerosis: fatty deposits (plaques) in artery walls
• Angina: chest pain from reduced blood flow
• Myocardial infarction (heart attack): complete blockage

Disorders:

Condition	Description	Treatment
Atherosclerosis	Plaque buildup in arteries	Statins, lifestyle
Hypertension	High blood pressure (>140/90)	Medication, diet
Heart failure	Heart cannot pump effectively	Medication, transplant
Varicose veins	Damaged valves in veins	Surgery, compression

⚡ WAEC Previous Year Pattern:

Year	Question	Concept
2023	Blood flow through heart	Sequence of chambers and valves
2022	Blood group genetics	Inheritance of ABO and Rh
2021	Comparison of vessels	Artery vs vein structure

Heartbeat and Pulse:

• Pulse = surge of blood through artery when ventricle contracts
• Radial pulse: felt at wrist
• Normal resting pulse: 60-100 bpm
• Athletes may have lower (50-60 bpm due to training)

Exchange at Capillaries:

• Thin walls (one cell layer)
• Pores allow exchange of small molecules
• At arterial end: high pressure → fluid leaves (nutrients, O₂)
• At venous end: low pressure → fluid returns (CO₂, waste)
• ~85% of fluid returns; ~15% becomes lymph

Transportation in Plants:

Xylem:

• Conducts water and mineral salts (from roots to leaves)
• Dead cells (tracheids and vessels)
• No cytoplasm
• Cell walls thickened with lignin

Phloem:

• Conducts dissolved food (sugars) from leaves to all parts
• Living cells (sieve tubes + companion cells)
• Uses energy for active transport

Transpiration Pull:

• Water evaporates from stomata
• Creates negative pressure (tension) in xylem
• Cohesion (water molecules stick together) and adhesion (water sticks to xylem walls)
• Pulls water up (capillary action contributes at small scale)

⚡ Exam Strategy: Draw and label a cross-section of a vein showing valves. For heart questions, trace blood flow from one point to another, naming all chambers and valves. Remember: arteries usually carry oxygenated blood AWAY from heart; veins carry deoxygenated blood TOWARD heart — except pulmonary vessels (reverse of normal).

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