Blood Pressure

High blood pressure, low blood pressure, what are you saying, doctors? What is blood pressure and why should we care?

What is blood pressure?

Blood pressure is the pressure that your blood exerts on the blood vessels. I know…. that’s a bit redundant.

Let me explain blood pressure a bit more, so you can visualize this. From what we’ve learned in school, the molecules in fluids interact closely with one another, meaning that they will not fill the entirety of a container unless you’ve placed enough of that fluid into the container to fill it completely. Each molecule exerts its own amount of force on each other and on the portion of the surface of the container that it interacts with.

Pressure is defined as a force exerted on a particular area. So the amount of force that the molecules exert on a particular portion of a container’s surface is equivalent to the pressure exerted by the molecule onto the container.

Now, if you replace the fluid with blood serum,the molecules with blood cells and the container with blood vessels, you’ll have the same situation; the blood cells each exert its own amount of force on portions of the blood vessel, which is the blood pressure.

Blood pressure naturally increases when your heart contracts to push blood into the blood vessels, and decreases when your heart relaxes.

Why is blood pressure important?

Blood pressure determines how hard your heart has to work to continuously feed your circulatory system with blood. The harder your heart works, the more strain there is in your circulatory system. This can lead to higher risk for health problems.

It’s also important to note that there are a variety of factors that affect blood pressure including how active you are, how much rest you get, your body temperature, diet, posture, medications and even your emotional state. So it’s important to try and stay healthy and active, for your heart and your health!

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!