Human heart

• Four chambers

• Double circuit

• Oxygen poor blood is pumped from the right side of the heart to the lungs where it is oxygenated. Oxygen rich blood then flows back to the left side of the heart and is pumped from there through the rest of the body.

Fish heart

• The simplest of the vertebrate hearts• Single circuit• Two chambers• Thin walled atrium• Muscular ventricle• Bulbus arteriolus, also ”conus”, does not pump

but is elastic and can stretch and squeeze.

• Blood is pumped from the heart to the gills• From the gills it is directly transported through

the body• Oxygen poor blood from the body returns to

the heart

Reptile heart

• Three chambers• Two atria, one ventricle and one conus

OR

• Four chambers• Two atria, two ventricles and one conus

• Wall (septum) between the ventricles is incomplete

• Some mixing of oxygenated and deoxygenated blood, minimized by timing of the contractions

Oxygen rich blood

Oxygen poor blood

Crocodile heart• The reptilian exception• Four chambers• ”Foramen fo Panizza” can direct oxygen poor

blood to the lungs OR to the stomach.• Why? One theory is that it helps digest bony

meals. Blood flowing from the body is rich in CO2 which is a building block in gastric acid. Thus, directing the CO2 rich blood to the stomach could actually help in digestion.

Active state:

Left Aorta

Right Aorta

”Foramen of Panizza”

Active state:

Resting/under water:

Red blood cells• Most important function: transport of oxygen.• Also: some transport of CO2 back to the lungs,

although this is primalily transported as HCO3- in the plasma.

• This transport is possible because of the haemoglobin.

• The iron in the hemegroup (in haemoglobin) binds temporarily to oxygen and enables the red blood cells to ”carry” the oxygen from the lungs/gills throughout the body.

• Four hemegroups in each red blood cell.• Mammalian red blood cells are haped as bi-

concave disks to increase surface area in relation to volume.

• In vertebrates red blood cells are developed in the bone marrow.

• No nucleus makes the cells different from all other mammalian cells.

• Mammalian red blood cells also lack DNA, RNA and all organelles.