circulatory systems and respiratory systems

Four main components of blood

1. Plasma: Liquid transport medium for blood cells, nutrients, and dissolved substances.\n2. Red blood cells: Transport oxygen bound to hemoglobin.\n3. White blood cells: Defend the body against infection.\n4. Platelets: Cell fragments essential for blood clotting.

Adaptations of red blood cells for oxygen transport

• Biconcave disc shape: Increases surface area to volume ratio for faster diffusion.\n- No nucleus: Provides maximum space inside the cell for hemoglobin.\n- High hemoglobin content: Binds reversibly to oxygen molecules.

Blood clotting mechanism and function

• Mechanism: Platelets trigger a reaction converting soluble fibrinogen into insoluble fibrin mesh, trapping blood cells. Function: Prevents excessive blood loss and blocks the entry of pathogens into wounds.

Three main types of blood vessels and their functions

1. Arteries: Carry oxygenated blood away from the heart under high pressure (except the pulmonary artery).\n2. Veins: Carry deoxygenated blood towards the heart under low pressure (except the pulmonary vein).\n3. Capillaries: Facilitate exchange of oxygen, glucose, and waste products with surrounding tissues.

Structural adaptations of blood vessels

• Arteries: Thick muscular and elastic walls, small lumen.\n- Veins: Thinner walls, large lumen, and valves to prevent backflow.\n- Capillaries: Wall is one cell thick for a short diffusion path.

Rate of blood flow formula

$$\text{Rate of blood flow} = \frac{\text{Volume of blood}}{\text{Time}}$$

Double circulatory system in mammals

A system where blood passes through the heart twice during one complete circuit:\n1. Pulmonary circuit: Heart to lungs to heart.\n2. Systemic circuit: Heart to rest of body to heart.

Advantage of a double circulatory system

Maintains higher blood pressure, allowing oxygenated blood to be pumped rapidly to tissues throughout the body.

Path of blood through the human heart

1. Deoxygenated blood enters right atrium via the vena cava.\n2. Moves to right ventricle and is pumped to lungs via pulmonary artery.\n3. Oxygenated blood returns to left atrium via pulmonary vein.\n4. Moves to left ventricle and is pumped to body via aorta.

Adaptation of the left ventricle wall

It has a significantly thicker muscular wall than the right ventricle to generate enough pressure to pump blood around the entire body.

Coronary heart disease causes and effects

• Cause: Buildup of fatty materials inside coronary arteries, narrowing them.\n- Effect: Restricts blood flow and reduces oxygen delivery to heart muscle cells, which can cause heart failure or a heart attack.

Stents vs Statins in treating heart disease

• Stents: Metal mesh tubes surgically inserted into coronary arteries to hold them open.\n- Statins: Prescription drugs that lower blood cholesterol levels, slowing fatty deposit buildup.

Treatments for faulty heart valves

Replacing leaky or stiff valves with biological valves (from human or animal tissue) or mechanical valves.

Role of natural and artificial pacemakers

• Natural Pacemaker: A group of cells in the right atrium wall that generates electrical impulses to control heart rate.\n- Artificial Pacemaker: An implanted electrical device used to correct irregular heart rhythms.

Need for exchange surfaces in large organisms

Large organisms have a small surface area to volume ratio ($SA:V$), making simple diffusion across the body surface too slow to supply internal cells.

Adaptations of alveoli for gas exchange

• Large surface area: Millions of alveoli maximize diffusion capacity.\n- Thin walls: Single-cell thick walls minimize diffusion distance.\n- Rich capillary supply: Maintains a steep concentration gradient for gases.

Inhalation mechanism in ventilation

1. Intercostal muscles and diaphragm contract.\n2. Ribcage moves up and out; diaphragm flattens.\n3. Thoracic volume increases, causing thoracic pressure to fall below atmospheric pressure.\n4. Air flows into the lungs.

Exhalation mechanism in ventilation

1. Intercostal muscles and diaphragm relax.\n2. Ribcage moves down and in; diaphragm returns to a dome shape.\n3. Thoracic volume decreases, raising thoracic pressure above atmospheric pressure.\n4. Air is forced out of the lungs.