Understanding Urinary Systems

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Understanding Urinary Systems

“… And the Little Piggy Went ‘wee-wee-wee’ All the Way Home!”*

(* origin: This Little Pig Went to Market by Lilly Martin Spencer, 1857)

Understanding Urinary Systems

What goes in must come out.” In this case, we mean understanding urinary systems, their structure and multiple functions.

“Urinary” is defined in Webster’s Dictionary as, “of or related to urine; of the organs involved in the secretion and discharge of urine.” This leads us to define “urine.”

Urine is “… a yellowish liquid containing urea — a highly soluble(dissolves in water) solid — found in body fluids and certain salts, etc., which is stored in the bladder and discharged periodically from the body through the urethra.” The word’s origin is rooted in Latin, “urina,” and Greek “ouron,” meaning water. 

Since the human body is composed mostly of water, the urinary system, though small and simple compared to other human systems, is vital to the continued health and survival status of the body at any given moment.

Urinary System Structure

The main parts of the urinary system are four:

  1. a pair of kidneys,
  2. a pair of ureters,
  3. a urinary bladder, and
  4. a urethra. 

Collectively called the urinary tract, these organs drain urine from the kidneys, accumulate and store it in the bladder, and then cause its release through the urethra in a simple process called urination. The system’s kidneys also balance the water, ions, pH, blood pressure, and calcium and magnesium levels (among other minerals, enzymes and hormones) of the whole body.

Urinary System Functions

Kidneys are bean-shaped organs located along the back wall of the abdomen, which produce urine by filtering blood wastes. The left kidney’s higher location accommodates the larger, right side of the liver. The kidneys enjoy a protection from damage by a layer of fat (called adipose) that also holds them in place.

Ureters are tubes that carry urine from the kidneys to the urinary bladder. About a foot long, they run on the left and right sides of the body parallel to the vertebral column. Gravity and a rhythmic movement of smooth muscle tissue inside the ureters move urine toward the bladder. Valves inside of the bladder prevent a back-flow of the fluid.

The urinary bladder is a sac-like hollow organ centrally located in the pelvis region, which stretches to hold anywhere from 600 to 800 milliliters of urine (slightly more than one pint).

The tube-like urethra passes urine from the bladder to outside of the body. The female urethra, around 2 inches long, ends at the vagina. The male urethra is around 8 to 10 inches long and it does double-duty by also carrying sperm out of the body through the penis, making it also an organ of the male reproductive system.

Internal and external urethral muscles control the flow of urine. When the bladder stretches to a certain level, a smooth muscle opens involuntarily, causing the sensation of needing to urinate (colloquially, needing to “pee” or “wee”). Another external, skeletal muscle may also open or be held closed, allowing urine to pass or be delayed.

Kidneys are the Kingpins

A lot goes on inside of the human body all the time. But it’s the kidneys who are the Kingpins, because they maintain and control several body systems’ status beyond their main duty to regulate the flow of substances out of the body.

The kidneys’ control over potassium, sodium, calcium, magnesium, phosphate, and chloride ions levels in urine, maintains a healthy ongoing balance (called homeostasis), despite constant changes inside of the body. One could say that their blood work is amazing!

More specifically, the kidneys monitor and regulate the levels of hydrogen ions (H+) and bicarbonate ions in the blood to control blood pH — the indicator of alkaline/acid ratios. They do this by controlling the amount of water that is filtered out of the blood and excreted into urine.

When a person consumes a large amount of water, the kidneys, by reducing the re-absorption of water into the blood, allow excess water to be excreted, giving a more-diluted quality to the urine, which, incidentally, also lowers blood pressure.

If a body is dehydrated, the kidneys re-absorb as much water as possible into the blood, producing as a result highly concentrated urine full of excreted ions and wastes. This production of more water in the blood stimulates the enzyme renin, which then constricts blood vessels, producing a more concentrated urine and raising blood pressure when it is low.

Hormones and Calcium Absorption

The kidneys interact with several hormones that control other body systems beyond the urinary. Parathyroid hormone (PTH) helps them to raise calcium ion levels in the bloodstream, and promote the small intestine to absorb more calcium from food and deposit it into the bloodstream. In this process, PTH and the kidneys work with calcitriol, which is an active form of vitamin D produced by UV radiation striking the skin.

An article prepared by Tim Taylor for Inner Body online, offers details about understanding male and female urinary systems.

There are still one or more human body systems to be explored in upcoming posts in this series, and the past posts within the series are informative. With a greater understanding of the systems of your body, you will appreciate not only the marvel that is the human body, but also how and why so many people use our product, Instant Calmag-C, every day of their lives.