Mass Transport - Humans

Haemoglobin

Found in erythrocytes, with 4 haem groups, each with one Fe 2+ ion. High affinity to oxygen so is efficient at transporting oxygen.

Association

The process in which haemoglobin binds to oxygen. In humans this is in the lungs.

Dissociation

The process by which haemoglobin releases oxygen. In humans this is in the respiring tissues.

Type of curve on oxyhaemoglobin dissociation curve

Sigmoidal.

Oxyhaemoglobin dissociation curve

Shows how saturated haemoglobin is with oxygen at any given time partial pressure of oxygen.

At low oxygen partial pressure

Haemoglobin does not easily bind with oxygen as haem groups are at centre which makes it difficult for the oxygen to bind with it. Low saturation level.

As oxygen partial pressure increases.

Diffusion gradient into haemoglobin increases so eventually an oxygen molecule will associate with one of the haem groups. This causes a change of shape so it is easier for oxygen molecules to associate.

High oxygen partial pressure

Difficult for 100% saturation as hard to associate with fourth haem group. Gradient levels out.

The Bohr Effect

Respiring cells produce CO2. A higher pCO2 causes the rate of dissociation to increase. The dissociation curve shifts to the right.

Haemoglobin is low oxygen

Association must be efficient so has a higher affinity. Dissociation curve to the LEFT

Haemoglobin at high activity levels

Must easily dissociate so has lower affinity. The dissociation curve is to the RIGHT.

Haemoglobin in smaller mammals

High metabolic rate so high oxygen demand. Must dissociate easily so low affinity. Dissociation curve to the RIGHT.

Structure of the circulatory system in mammals

Closed: blood is confined to vessels

Double: blood passes twice through the heart

Side of the heart with deoxygenated blood

Right side

Side of the heart with oxygenated blood

Left side

Left ventricle muscle

The thickest muscle to pump oxygenated blood at a high pressure to the whole body

Vena Cava

Transports deoxygenated blood from body to heart

Pulmonary artery

Transports deoxygenated blood from heart to lungs

Pulmonary vein

Transports oxygenated blood from lungs to heart

Aorta

Transports oxygenated blood from heart to body

Why is there a low pressure in the pulmonary artery?

The lung tissues would be damaged

Coronary arteries

Supplies the heart tissues with blood

Arteries

Carry blood from heart to the rest of the body under a high pressure

Adaptations of the artery

Lumen small to maintain blood pressure. Collagen and proteins mean thick walls. Elastic tissue allows stretch and recoil. Smooth endothelium folded. Smooth muscle allows contraction .

Vein

Carry blood back to heart under low pressure

Adaptations of the veins

Large lumen to ease flow of blood. Less muscle and elastic tissue so thin but strong walls. Valves prevent backflow of blood.

Capillaries

Smallest blood vessels where molecules are exchanged between the blood and cells

Adaptations of the capillaries

One layer of flattened endothelial cells which reduces diffusion distance. Narrow lumen slows down erythrocytes so more oxygen can diffuse. Fenustrations allow movement of nutrients

Systole

Contraction of cardiac muscle

Diastole

Relaxation of cardiac muscle

First stage of cardiac cycle

Ventricular diastole and atrial systole. Causes the volume of the atria to decrease, increasing the pressure so blood moves through atrioventricular valve down pressure gradient into ventricle

Second stage of cardiac cycle

Ventricular systole and atrial diastole. Volume of ventricle decreases so pressure increases. Blood flows back shutting atrioventricular valve making ‘LUB’ sound. Blood moves into artery through semi-lunar valve

Third stage of cardiac cycle

Diastole. Blood moves back due to higher pressure in artery shutting semi-lunar valve, ‘DUB’ sound.