• The urinary system consists of 2 kidneys, 2 ureters, a urinary bladder,
and a urethra.
• The job of the kidneys is to filter the blood.
• The kidneys receive 25% of the total cardiac output each minute.
• The outside layer of the kidney is called the renal capsule.
• Directly beneath the capsule is the renal cortex.
• The inner portion of the kidney is called the renal medulla.
It is made up of renal pyramids.
• Each renal pyramid is a collection of thousands of nephrons.
• A nephron is a filtering unit. Each kidney has about 1 million
of them.
• Blood vessels enter the nephron. In the glomerular capsule,
which is wrapped around the vessels, waste products and water are removed.
• The very dilute urine then passes through the proximal convoluted
tubule, the loop of Henle, and the distal convoluted tubule before entering
a collecting duct and moving to the calyx.
• The task of the tubules and the loop of Henle is to remove water
from the dilute urine.
• The resulting liquid waste is 95% water, the rest consisting of urea,
salts, etc.
• After wastes are filtered out of the blood in the nephrons, they
are collected in the calyces.
• From the calyces, the urine goes into the renal pelvis and then out
of the kidney into the ureter.
• The ureters carry urine from the kidneys to the urinary bladder.
• The urinary bladder stores the urine until it is ready to be expelled
from the body.
• The bladder can hold about 1 pint (500 ml) of liquid.
• Urine exits the body from the bladder through the urethra.
• Micturition is the process of expelling liquid wastes via the urethra.
It is triggered when bladder capacity reaches about 200 ml.
• Daily urinary volume is about 1.6 to 1.8 L.
• Urine is yellow due to urichrome in bile.
