THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -The pyramids consist mainly of tubules that transport urine from the cortical, or outer, part of the kidney, where urine is produced, to the calyces, or cup-shaped cavities in which urine collects before it passes through the ureter to the bladder. The point of each pyramid, called the papilla, projects into a calyx.

Detailed explanation-2: -The papillae are bundles of collecting ducts that transport urine made by nephrons to the calyces of the kidney for excretion. The renal columns also serve to divide the kidney into 6–8 lobes and provide a supportive framework for vessels that enter and exit the cortex.

Detailed explanation-3: -The main function of the medulla is to regulate concentration of the urine. The urine flows from the collecting ducts into the renal calyces and pelvis, which undergoes unidirectional peristaltic movements to allow drainage of the urine into the downstream ureter and bladder.