Video Transcript
Which of the following structures is responsible for urine formation? (A) The pelvis, (B) the ureter, (C) the nephron, or (D) the urinary bladder.
Urine is the name of the fluid with which the body can eliminate excess water, salt,
and nitrogen compounds, such as urea. Urine is therefore formed in order to be removed from our body. The organ system which is specifically responsible for removing urine from the body
is called the urinary system. In order to find out which structure is responsible for urine formation, let’s
discuss the parts and functions of the organs which make up the urinary system.
The kidneys are the primary organ of the urinary system. Their function is to filter waste from the blood and form urine. The ureter connects the kidneys to the urinary bladder. The urinary bladder, also commonly just called the bladder, is an expandable muscular
saclike organ that sits in the lower pelvis. It stores urine until it is ready to be removed from the body. A sphincter muscle controls the expulsion of urine.
When we urinate, urine passes from the bladder to the external environment through a
tube called the urethra. We just discussed the fact that one of the kidney’s function is to make urine. The ureter and the urinary bladder’s function are to transport and store the
urine. We can therefore exclude answer options (B) and (D).
However, as “kidney” is not in our answer choices, there has to be a specific part of
the kidney which is responsible for urine formation. So let’s have a closer look at the kidney itself.
The kidneys are soft, delicate organs. They are protected by the bones of the ribs and surrounded and supported by a tough
membrane known as a renal capsule. The renal capsule surrounds a layer of tissue called the renal cortex. Within the cortex are teardrop-shaped sections of tissue called the renal
medulla. At the center of the kidney is the renal pelvis, which connects the kidney to the
bladder through the ureter.
Spanning the renal cortex and medulla are millions of microscopic structures called
nephrons. These nephrons, a series of tubules and capillaries, are the functional units of the
kidney that make the urine. Each nephron connects to a collecting duct, which connects to the renal pelvis and
ureter to deliver urine to the bladder. With this information, we can now exclude answer option (C) as well. The function of the renal pelvis is to transport and not form urine.
The structure which is responsible for urine formation is the nephron.
