B3.2 HL Transport in Animals [IB Biology HL]

Transport in Animals

Circulatory System Overview

  • Components:

    • Arteries: Carry blood away from the heart at high pressure.

    • Veins: Return blood to the heart at low pressure.

    • Capillaries: Sites of diffusion between blood and tissues.

  • Function of Pressure:

    • High arterial pressure forces blood plasma into capillaries, creating tissue fluid filled with oxygen, glucose, and ions.

    • Waste products like carbon dioxide diffuse from cells into capillaries due to low pressure.

Mechanisms of Transport

Diffusion

  • Oxygen Transport:

    • Oxygen diffuses from blood into tissues via passive diffusion (high to low concentration without energy).

  • Glucose Transport:

    • Glucose also moves into tissues, often against its concentration gradient (low to high concentration).

    • Uses sodium-glucose co-transporters, involving sodium ion concentration gradients for passive movement.

    • Important for cellular respiration as cells require both oxygen and glucose.

Waste Removal

  • Carbon Dioxide Transport:

    • Carbon dioxide diffuses from cells into blood (high concentration in cells, low in blood) to be transported to the lungs for exhalation.

Important Themes

  • Concentration gradients crucial for nutrient and waste product exchange.

  • Fluid Return:

    • About 85% of the forced tissue fluid reenters capillaries, while 15% drains into the lymphatic system (lymph) before returning to the circulatory system.

Circulatory Systems in Mammals

Heart Structure

  • Four-Chambered Heart:

    • Right side receives deoxygenated blood from the body (via vena cava).

    • Blood flows from the right atrium to the right ventricle through atrioventricular (AV) valves.

    • Blood exits right ventricle through semilunar valves to the lungs for oxygenation.

Double Circulation

  • Functionality:

    • High-pressure loop sends oxygenated blood to the body.

    • Low-pressure loop sends deoxygenated blood to the lungs.

  • Efficiency of Pressure Regulation:

    • High pressure essential for distributing blood to organs but must be lower in the lung capillaries for efficient oxygen diffusion from alveoli into blood.

Comparison with Fish Circulatory System

  • Fish have a single-loop circulatory system due to water pressure surrounding gills, allowing for effective oxygen extraction and nutrient distribution without needing separate loops.

Summary of Heart Blood Flow Steps

  1. Deoxygenated blood enters the right atrium through the vena cava.

  2. Blood moves into the right ventricle via AV valves.

  3. Blood is pumped to the lungs through semilunar valves.

  4. Oxygenated blood returns to the left side of the heart from the lungs to begin the cycle anew.