Alcohol and Urine

For the last couple of weeks, I’ve talked to you about pee… a lot. But now that we’ve got all of that good stuff down pat, it’s time to get to the point of this whole thing: the effects of alcohol on urine!

Whenever you drink alcohol, you eventually feel the need to urinate frequently. But why?!

Well, last week we learned about the two hormones that are involved in regulating the production of urine: the antidiuretic hormone and aldosterone.

Interestingly enough, alcohol has an inhibitory effect on the antidiuretic hormone. This hormone is responsible for helping the body retain water by preventing the loss of water through excretory pathways, like the urine system.

The inhibition of the antidiuretic hormone results in the loss of regulating how much water is reabsorbed in the kidneys, which means that there is an uncontrollable loss of water in your urine, which is why you feel the need to urinate a lot. Your bladder is always filled because there is no reabsorption of water in the nephron of your kidneys.

So basically, alcohol reduces the amount of water reabsorbed in the kidneys, which leads to the water ending up in your bladder and putting pressure on your urinary sphincters. And then you feel the need to urinate, even if you already went to the bathroom 10 minutes ago.

One of many life’s mysteries have been solved. The inhibition of the antidiuretic hormone by alcohol is another reason why rehydration is so important for post-drinking. You lost all of the water your body would have reabsorbed when you peed, so you need to drink even more water to save your body from being in a state of dehydration.

And that’s how alcohol affects your body’s urinary system! Next week, we’ll look into hangovers.

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The Urinary System – Selective Reabsorption

Last week, we learned about the general filtration process that occurs in our kidneys. This week, we’ll learn just how our kidneys modify the filtrate to produce urine.

The filtrate that is in the renal tubule consists of water as well as other small molecules, like sugars and urea. Some of these molecules, like sugars, can return to the bloodstream in a ‘process’ known as selective reabsorption. It’s called ‘selective’ reabsorption because the bloodstream is picky as to what it absorbs from the tubule. The molecules that leave the tubule enter tiny blood vessels next to the tubule, which are called peritubular capillaries. The molecules can then be carried through the rest of the circulatory system, to provide our body cells with nutrients (if they’re sugars).

Parts of the Kidney

Selective reabsorption mainly occurs in the proximal tubule, which is the beginning of the tubule. The proximal tubule is just after the Bowman’s capsule. Whenever a molecule leaves, it is accompanies by water, which means a lot of water is reabsorbed by the bloodstream in this process.

By returning the molecules to the bloodstream, the remaining filtrate’s composition changes. As water leaves, the concentration of particles in the tubule increases.

Hormones can affect what is reabsorbed in the distal tubule. These hormones are the anitidiuretic hormone (ADH), which is also known as vasopressin, and aldosterone. They’ll be discussed next week when we talk about Concentration and Dilution!

The Urinary System – Filtration

Last week, we talked about the basics of the urinary system, including the organs involved. This week, let’s take a closer look at what happens in the kidney, starting with filtration. The posts will be segmented because there will be a lot of new terms coming your way, and I would hate for you to get overwhelmed! So let’s learn how our bodies makes our pee, step by step.

Parts of the kidney

The basic functional unit within the kidneys is known as the nephron. This consists of all of the numbered portions, starting at the glomerulus (5) and ending at the distal tubule (6). 

The main components involved in filtration are the arteries, and the glomerulus.

Filtration

It is at the Bowman’s capsule where the filtration of blood occurs. The blood from the renal artery (renal means ‘kidney’) flows into a smaller version of an artery, known as the afferent arteriole. The name sounds weird, but ‘afferent’ basically means ‘towards something’. So this arteriole is moving blood towards the glomerulus. So this arteriole can also be referred to as the afferent glomerular arteriole.

The afferent arteriole then branches to form tiny blood vessels known as capillaries. These capillaries form a ball-like structure, which is part of the glomerulus (5). The capillaries are therefore called the glomerular capillaries.

The blood from the capillaries continues to flow into the next vessel, which is another arteriole, named the efferent arteriole. ‘Efferent’ means ‘away from something’, so the blood is moving away from the glomerulus. So this arteriole can also be referred to as the efferent glomerular arteriole.

This movement of the blood increases the amount of pressure within the capillaries, causing fluids to leak out. These fluids pass through a filter-like membrane, known as the glomerular basement membrane. Some substances are too large to pass through the basement membrane and, therefore, continue to circulate through the bloodstream.

The filtrate that goes through the glomerular basement membrane enters the Bowman’s capsule. The space inside the Bowman’s capsule is continuous with the rest of the tubule, which includes the proximal tubule, the loop of Henle and the distal tubule. The filtrate is concentrated and modified within these components of the tubule, which will be discussed next week.

And that is, thankfully, all there is to the filtration process for the urinary system! Next week, we’ll learn about what happens to the filtrate in the tubule.

The Urinary System – Basics

Before we can talk about how alcohol affects your urinary system, it’s important to understand the urinary system and how it usually works first. This will be a pretty general overview, though I will also provide a molecular overview of the system next week!

So let’s start learning about how urine is made!

The Urine Pathway

The organs involved in your urinary system:

  • Liver – synthesizes urea and releases it into the blood
  • Kidneys – filters the blood for urea, sodium, bicarbonate and water. If they are high levels of any of them, the kidneys will divert them from the bloodstream, and produces urine.
  • Bladder – the products of urine move from the kidney to your bladder, then to the urethra to be released.

The bladder actually has two muscles that control the release of urine: the internal and external sphincter. The internal sphincter relaxes on its own accord, thanks to your sympathetic nervous system. It is the external sphincter that helps you control whether you pee your pants or not.

And those are the basics of the urinary system! Next week, we’ll be looking at the detailed pathway (for you keeners (: ).