HGH (Human Growth Hormone) is a protein hormone which is produced by the endocrine system in the human body. It is made from 190 individual amino acid molecules, and is secreted by the pituitary gland.
However, in pulmonary circulation, the arteries carry deoxygenated blood from the heart to the lungs, and veins return blood from the lungs to the heart. The difference between veins and arteries is their direction of flow (out of the heart by arteries, returning to the heart for veins), not their oxygen content.he pulmonary veins carry relatively oxygenated blood from the lungs to the heart. The superior and inferior venae cavae carry relatively deoxygenated blood from the upper and lower systemic circulations, respectively. The portal venous system is a series of veins or venules that directly connect two capillary beds.
in most cases, veins carry deoxygenated blood. the exception to this are the pulmonary veins which carry oxygenated blood. all veins carry blood back to the heart, while arter â¦ ies carry blood away from the heart.