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!

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.


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 (: ).

Pins and Needles aka Parasthesia

Nowadays, it seems like my legs get a lot more sleep than I do. “#firstworldproblems, #universitywoes”. But, really, why do our limbs fall asleep and why do they tingle us so uncomfortably when they do?

Pins and Needles

The sleeping of our limbs, also termed ‘parasthesia’, is the result of our nerves acting abnormally due to an increased pressure on them for a prolonged period of time. Our nerves essentially act as little messengers between our limbs and our brain. So this prolonged pressure on the nerves results in the loss of communication between the limbs and our brain.

There is also a prolonged pressure placed on our blood vessels, which results in our nerves not receiving enough oxygen or nutrients.

So, in response to this pressure, nerves, much like how we respond to pressure, can react in to different ways: They can either become unresponsive and wait until the pressure has been removed, or they will essentially begin to spaz out and rapidly send signals in hopes of sending them in the right direction.

Now, the latter causes a problem because we have a lot of different nerves feeding our brains with a lot of different information: some inform us about temperature, some others about pressure on our skin and so forth. So when the nerves start spastically sending signals, the brain is unable to fully interpret what is happening and gets a mix of signals about warmth and numb sensations as well as conflicting signals about being cold and tingling sensations. This is why our sleeping limbs are described as having pins and needles. The mix of signals results in a mix of sensations, including an odd duality of numbness and tingling.

How to wake up your limbs

Many people try to hit their limbs that have fallen asleep. That doesn’t really do anything, unfortunately. The best we can do is to change our positions to remove the pressure and wait for the blood flow and nerve responses to return to normal.

And that’s all there is to know about pins and needles. Ironically, my foot has now fallen asleep so it’s time to practice what I preach.


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Blood Types

If you haven’t noticed, this month’s theme is appropriately set to ‘blood’ in honour of Halloween. So we might as well talk about the blood types, or groups, that we hear about so often.

Why do we have different blood types?

While blood is generally the same for everyone, where it contains red cells, white cells, platelets and plasma, there is one key component which differs. This component is a little protein and sugar marker, which is found on the surfaces of our red blood cells. These markers, also known as antigens, act as little flags to your immune system to tell it that the cells are part of your system and not an invader.

This is why blood transfusions can get so complicated; if your immune system recognizes the difference between the markers on your usual blood cells and the blood cells you received from a donor, then your immune system will attack those donor blood cells.

What are the different blood types?

A, B, AB, O

There are three different antigens: A, B, and Rh (which is discussed later).

The presence or absence of these antigens results in four major blood divisions:

    1. Type A – has the “A” antigen.
    2. Type B – has the “B” antigen.
    3. Type AB – has both the “A” and “B” antigens.
    4. Type O – has neither the “A” or “B” antigens.

The fact that Type O blood doesn’t have A or B antigens makes it easier for Type O to be donated to anyone, regardless of their blood types; the immune system cannot recognize Type O blood as an invader because it doesn’t have any antigens for the immune system to latch onto. Type O individuals, however, cannot accept any blood except Type O since its immune system isn’t accustomed to seeing any antigens whatsoever; the presence of an antigen on the donor blood would elicit an immune response.

+, –

The other antigen that might be present on our blood cells is the Rhesus factor (Rh).

If it is present, the main blood divisions (A, B, AB, or O) are assigned a plus sign (+): A+, B+, AB+, O+.

If the Rh factor is absent from the blood cells, they are assigned a minus sign (-): A-, B-, AB-, O-.

O- individuals are universal donors, because they do not carry any antigens which the immune system would be able to attack. AB+ individuals, on the other hand, have all of the possible antigens and therefore are the universal acceptors as their immune system is used to seeing each of the  antigens. This means it won’t attack any of the antigens!

Those are the different blood types. It’s important that you know your own blood type and the blood type of your loved ones in case of emergencies. It’ll be easier for doctors to determine which blood type to provide you!

Donating blood is also a great idea, though it isn’t for everyone. If you are interested in donating blood, contact your local blood donor clinic to check if you meet the requirements! 🙂

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Ouchy, that’s a boo boo!

It can hurt like no tomorrow whenever you scrape your skin deeply or get a nasty cut and you start to bleed. Eventually, you’ll notice that in place of the bloody cut or scrape, there’s a scab. But what are scabs made of and how do scabs form?

As soon as your skin and blood vessels are damaged, your blood interacts with collagen. This is a protein that is found in your skin. When this is detected, specialized blood cells called platelets, or thrombocytes, rush to the area and secrete inflammatory factors. At the same time, these platelets stick together; they aggregate to form a clot.

Two other proteins, fibrin and fibronectin, then form a net-like structure to prevent further blood loss. Platelets attach to this net and acts as a temporary skin layer until the entirety of the net structure is replaced by collagen.

The platelets release growth factors, which stimulate the rate of cellular division, to help regenerate the lost or damaged skin cells. It releases a lot of other proinflammatory factors that help in the healing process, like serotonin and histamine, to dilate blood vessels and increase cell proliferation.

scab is basically the net structure intermediate of fibrin, fibronectin and platelets that acts as a shield for your body against any external infectious particles.

So, it’s good that our bodies scab in response to blood vessel damage because, otherwise, we would be exposed to several infectious particles and contract diseases with every paper cut that drew blood. And that could lead to much more pain than a little boo boo.

Nosebleeds aka Epistaxis

My roommate had a nosebleed a while ago, and I thought that it might be a good idea to go into why people get nosebleeds and how to properly take care of one.

What are the common causes for nosebleeds?

Picking your nose or Minor injuries

When you pick your nose, you might scratch against a blood vessel that lines the inside of your nose, which leads to blood escaping the vessel and your nose. Minor injuries like bashing your nose against a table or being punched in the nose can lead to the breaking of the blood vessels too.

Colds or Allergies or Dry, heated air or Blowing your nose

The inside of your nostrils are usually lined with mucous, which makes it a moist environment. On the other hand, these situations, excluding blowing your nose, cause your blood vessels to dry out and and become crusty, which can lead to the breaking of the vessels. Blowing your nose while having a cold or an allergic reaction can further irritate the vessel lining of your nose, which can eventually lead to a nosebleed too.

How to take care of a nosebleed

If your nose is bleeding because of a sustained injury, make sure to go see your doctor to ensure that everything is okay. If your nose starts bleeding on its own, likely due to the other reasons, then here are some things you should do:

  • Do not lie down
  • Damp washcloths usually work best to catch blood
  • Do not tip your head back
  • Pinch the part of your nose just below the bony part and breathe through your mouth for 10 minutes or so. If you do this for 20 minutes and your nose is still bleeding, talk to your doctor.
  • If you have a room with dry air, getting a humidifier helps to prevent future nosebleeds.

Both of the italicized points are things you should not do. They both lead to the blood going down, into your throat, which can lead to you choking on your blood. So please remember to sit up or stand with your head leaned forward, not back!

See your doctor if: you feel like you might pass out, you look like you’re losing too much blood or you just started taking a new prescription.

So, all you nose-pickers, watch out because winter might be the worst time for you to do your thing; the dry air will make your nose lining less moist and picking your nose is basically like begging for a nosebleed.

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Whenever you run into something or take a bad fall, you’ll find a bruise in the place that hurts (so long as your skin didn’t tear!). But what causes bruising and is there a way to treat it?

What is bruising?

Bruises, also known as contusions or ecchymosis, are the localized pooling of blood outside of blood vessels. So a bruise is simply when your blood escapes your blood vessels in a tissue yet remains in a certain area.

Why do we bruise?

When a part of your body is struck, the impact causes your blood vessels (more specifically capillaries, though sometimes it’s venules) in that area to rupture. This releases blood cells close to the skin’s surface, which spread out under the skin giving it a reddish colour.

The Colour changes of a Bruise

  1. This reddish colour changes over the period of healing for a bruise. At the beginning, your bruise will be red because it will have an iron-oxygen complex.
  2. After a couple days, however, your bruise will change to a deep purple or a blue colour; this is because the oxygen will have been used up by the surrounding tissues, resulting in the loss of an iron-oxygen complex (which gave the blood its red colour).
  3. Then you bruise will slowly begin to heal; at around 5 days, your bruise may turn a green colour which is the result of hemoglobin, the protein found in our blood cells that contains iron to attract oxygen, breaking down in the blood cells that escaped.
  4. The final colour stage is a yellow or brown colour, where the body is reabsorbing the lost blood and in its last stretch of healing itself. This usually occurs after 9 or 10 days.

How to help your bruise heal

When your bruise is healing, the blood that remains in the blood vessels needs to clot to prevent the further loss of blood. To help with the clotting process, it is recommended that you rest the affected area to ensure that there is no additional stress on the tissue.

Also, apply something to cool the area, perhaps a bag of ice or an ice pack. By cooling the area, you help influence the blood vessels to constrict. By constricting, the blood vessels reduce blood flow which means that there will be less blood that is lost through the rupture. Icing the area will also help calm down any swelling that occurs, but make sure to only apply ice intermittently for a maximum duration of 20 minutes. For the first day, it’s recommended that you ice the bruise for 20 minutes, take a break from the cooling for 20 minutes, and then repeat.

Both of these methods will help prevent the spread of blood underneath the skin but outside of the blood vessels; in other words, it helps contain the blood that escaped from the blood vessel in one area.

If you don’t rest the tissue after its blood vessel ruptures, it is likely that blood will spread to other areas in the vicinity of the impacted area. This is why you will sometimes find that there is a new bruise near the original one a day or two later.

Your blood vessels will heal themselves over the roughly 9 day period and your skin should go back to normal; just remember, rest and ice up! If you don’t, it can take a lot longer for the tissue to heal.


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Cholesterol – Bad?

Last week, we talked about the good side of cholesterol, which we don’t really hear about. No, instead we hear about the evils of cholesterol and how it can lead to heart disease. But cholesterol seems to help us out a lot, so what makes it so bad?

Types of Cholesterol

There are two ‘types’ of cholesterol. I use ‘types’ but it’s really the type of transport that the cholesterol uses that differentiates one ‘type’ from the other.

You see, cholesterol requires a transport system between the liver, where it is predominantly produced, and other cells because cholesterol is insoluble. The transporters for cholesterol are lipoproteins. Lipoproteins are molecules that consist of a mix of lipids and proteins. The lipid portion of the lipoprotein can interact with the cholesterol, while the protein portion allows the complex to travel in the bloodstream.

There are two different transporters that transport cholesterol; LDL and HDL. LDL stands for Low-Density Lipoprotein while HDL stands for High-Density Lipoprotein. LDLs transport cholesterol from the liver to the other cells in the body, while HDLs transport cholesterol from the cells of the body to the liver.

“Bad Cholesterol”

This refers to cholesterol that is being transported by LDLs. Since the LDLs carry the cholesterol from the liver to the cells, which have a lower storage capacity for cholesterol, there is the possibility of the build-up of the LDLs (and cholesterol) in your bloodstream if you have more cholesterol in your bloodstream than is required for your cells. The build-up will occur on the walls of the arteries that lead to your heart and brain. Too much build-up can result in the formation of a clot, which can induce heart attacks or strokes.

They’re not all bad…

HDL is the superhero of lipoproteins. It’s like the older sibling that looks out for their younger sibling, slowly cleaning up any mess they make. HDLs carry cholesterol from the cells and the bloodstream back to the liver, where it can be broken down into bile and then stored in the gallbladder. On their way, they can help clean up the LDLs’ messes by grabbing them and dragging them back to the liver, where the cholesterol is deposited for further storage. This reduces the amount of LDL in the bloodstream, reducing the build-up in your blood and reducing your risk of heart disease. This is probably why HDLs are referred to as “Good cholesterol”.

LDLs are larger than HDLs, which is probably why the former causes clots whereas the latter doesn’t.

Lowering your Risk

You produce LDLs and HDLs naturally. While you can’t control exactly how much your body produces, you can control what you eat as it was found that certain fats stimulate the production of LDLs.

The American Heart Association’s Nutrition Committee strongly advises these guidelines for people over the age of two:

  • Limit total fat intake to less than 25–35 percent of your total daily calories (TDC)
  • Limit saturated fat intake to less than 7 percent of TDC
  • Limit trans fat intake to less than 1 percent of TDC
  • The remaining fat (17-27% of TDC) should come from sources of monounsaturated and polyunsaturated fats
  • Limit cholesterol intake to less than 300 mg per day, for most people.  If you have coronary heart disease or your LDL cholesterol level is 100 mg/dL or greater, limit your cholesterol intake to less than 200 milligrams a day.

Your physician can check your cholesterol levels by performing a blood test. You want to keep your LDL levels below 130mg/dL and your HDL levels ideally above 60mg/dL. You want low LDL levels and high HDL levels to reduce your risk of heart disease. If you have high LDL levels (the dreaded “high cholesterol”) and/or low HDL levels (the dreaded “low cholesterol”), then you’re going to want to look into dietary and lifestyle changes.

So, it looks like cholesterol can be the good guy or an accomplice depending on who it’s traveling with. Or, I suppose it could be considered a bystander. But now you know that bad cholesterol doesn’t really have to do with the cholesterol itself, but rather its ride.


American Heart Association. 2013. Know Your Fats. <> May 30, 2013.