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Human Body - The Circulatory System

Grade 6ICSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

The Circulatory System consists of the heart, blood vessels, and blood, responsible for transporting O2O_2, CO2CO_2, nutrients, and waste products.

Blood is composed of Plasma (liquid part) and three types of cells: Red Blood Cells (RBCsRBCs), White Blood Cells (WBCsWBCs), and Platelets.

RBCsRBCs contain a red pigment called Hemoglobin, which binds with oxygen to form Oxyhemoglobin for transport.

The human heart is a four-chambered muscular organ with two upper chambers called Atria and two lower chambers called Ventricles.

Arteries carry oxygenated blood (O2O_2) away from the heart to the body, with the exception of the Pulmonary Artery.

Veins carry deoxygenated blood (CO2CO_2) from the body back to the heart, with the exception of the Pulmonary Vein.

Capillaries are extremely thin-walled vessels where the actual exchange of gases (O2O_2 and CO2CO_2) and nutrients takes place.

Double Circulation involves two circuits: Pulmonary circulation (heart to lungs and back) and Systemic circulation (heart to body and back).

📐Formulae

Heart Rate (bpm)=Number of HeartbeatsTime in Minutes\text{Heart Rate (bpm)} = \frac{\text{Number of Heartbeats}}{\text{Time in Minutes}}

Blood Composition55% Plasma+45% Formed Elements (Cells)\text{Blood Composition} \approx 55\% \text{ Plasma} + 45\% \text{ Formed Elements (Cells)}

Hemoglobin+O2Oxyhemoglobin\text{Hemoglobin} + O_2 \rightleftharpoons \text{Oxyhemoglobin}

💡Examples

Problem 1:

A person's heart beats 150150 times in 22 minutes. Calculate the heart rate in beats per minute (bpmbpm).

Solution:

Heart Rate=1502=75 bpm\text{Heart Rate} = \frac{150}{2} = 75 \text{ bpm}

Explanation:

Heart rate is defined as the number of heartbeats per unit of time (usually 1 minute). By dividing the total beats by the total minutes, we find the rate is 7575 bpmbpm.

Problem 2:

Explain the role of Hemoglobin in the transport of O2O_2.

Solution:

Hb+4O2Hb(O2)4\text{Hb} + 4O_2 \rightarrow \text{Hb}(O_2)_4

Explanation:

Hemoglobin (HbHb) is a protein in RBCsRBCs that has a high affinity for oxygen. In the lungs, it combines with oxygen to form a temporary compound called Oxyhemoglobin, which travels through the blood to reach tissues.

Problem 3:

Differentiate between the pressure in Arteries and Veins.

Solution:

Partery>PveinP_{\text{artery}} > P_{\text{vein}}

Explanation:

Blood in arteries is pumped directly by the heart, resulting in high pressure (PP). Therefore, arteries have thick, elastic walls. Veins carry blood under lower pressure back to the heart and contain valves to prevent backflow.

The Circulatory System - Revision Notes & Key Formulas | ICSE Class 6 Science