When blood calcium levels drop, the parathyroid gland secretes parathyroid hormone. This hormone works to raise blood calcium levels by stimulating osteoclasts to break down bone and release calcium into the bloodstream. PTH also signals your kidneys to conserve calcium by reducing the amount excreted in the urine.itamin D. Vitamin D acts as a hormone in your body to help regulate blood calcium. This steroid hormone is so vital in maintaining calcium balance that its active form is sometimes referred to as calcitriol.
The Colosseum, originally known as the Flavian Amphitheatre, is a large amphitheatre in the city of Rome. The construction of the Colosseum started around 70â72 AD and was finished in 80 AD.Emperor Vespasian started the works, and Emperor Titus completed them. Emperor Domitian made some changes to the building between 81â96AD. It had seating for 50,000 people. It was 156 metres wide, 189 metres long and 57 metres tall.he Colosseum is a free standing building, quite different to the earlier Greek theatres which were built into the sides of hills. It is really two Roman theatres joined together. It is oval shaped, 189 meters (615 ft / 640 Roman feet) long, and 156 meters (510 ft / 528 Roman feet) wide.
The Colossus of Rhodes, depicted in this hand-colored engraving, was built about 280 BC. Standing 30 meters (100 feet) high, it was built to guard the entrance to the harbor at Rhodes. The ancient Greeks and Romans considered it to be one of the Seven Wonders of the World. Public Domain.