The capillaries have thin walls and arteries have thick walls.

The Tunica adventitia layer of the blood vessels consist of hyaline cartilage.

The cross section of blood vessels (artery and vein) shows three layers. they are ______, ________, and ______.

The cartilage rings prevent trachea from collapsing.

The label 23 is Abdominal Aorta.  

The ______ carry oxygenated blood from the lungs to the heart.

The diffusion of carbon dioxide  into the blood and that of oxygen out of blood into the tissue cells is called ________

If the aorta and pulmonary trunk were switched, oxygen rich blood would be pumped from the left ventricle to the lungs.

The ________ vein drains the liver.

The lungs receives its blood supply from the coronary arteries.