blood flow

EMT Blood Flow Basics: Where is the Blood Going?

Imagine your blood is like a delivery truck carrying oxygen and nutrients. The arteries are the roads these trucks travel on. As an EMT, you need to know the major roads to understand where the blood is going and if there are any problems.

The Heart: Your Main Pump and Its Fuel Line

  • Your heart is the body's super-strong pump. It pushes blood everywhere.

  • The left ventricle is the strongest part of this pump, sending blood to most of your body.

  • The Left Coronary Artery is like the heart's own gas tank. It delivers blood to the heart muscle itself so the heart can keep pumping. If this artery is blocked, the heart muscle can get sick or stop working.

Roads to the Head and Arms (A.C.S.B.R.U. - "All Cats Stress Because Rats Undergo")

This helps you remember the main blood roads from your heart up to your head and out to your arms:

  • Aorta: This is the biggest highway out of the heart. All blood starts here.

  • Carotid Arteries (Right & Left):

    • These are the main roads that go straight up from the aorta to your head and brain.

    • EMT Tip: You can feel the strong Carotid pulse on either side of the neck. This tells you the heart is still pumping strong to the brain.

  • Subclavian Arteries (Right & Left):

    • These roads go under your collarbones (where the name "subclavian" comes from).

    • They then send blood down towards your arms.

  • Brachial Artery:

    • This is the main blood road in your upper arm.

    • EMT Tip: This is where you would usually listen for blood pressure, and also a good place to find a Brachial pulse in babies.

  • Near your elbow, the Brachial artery splits into two smaller roads for your lower arm and hand:

    • Radial Artery: Travels along the thumb side of your lower arm and into your hand.

    • EMT Tip: This is the most common place to check a Radial pulse at the wrist. It's a quick check to see if blood is reaching the arm/hand.

    • Ulnar Artery: Travels along the little finger side of your lower arm and into your hand.

Roads to the Legs (D.I.F.A.P.P. - "Down In France, All People Party")

This helps you remember the main blood roads from your chest all the way down to your legs and feet:

  • Descending Aorta: This is the same main highway (Aorta) continuing down through your chest and tummy. At the level of your belly button, it splits.

  • Iliac Arteries (Right & Left):

    • These are the major roads that split off and go to your pelvis and hip area.

    • They then become the roads that go into your legs.

  • Femoral Arteries (Right & Left):

    • These are the big roads that run through your upper legs (thighs) and pass through your groin.

    • EMT Tip: You check for a Femoral pulse in the groin area. This pulse is very important to check if someone is in severe shock and you can't feel other pulses.

  • Around your knee, each Femoral artery splits into other roads for your lower leg and foot:

    • Anterior Tibial Artery: Supplies the front part of your lower leg.

    • Posterior Tibial Artery: Supplies the back part of your lower leg.

    • EMT Tip: You can feel the Posterior Tibial pulse right behind the inner ankle bone. This checks if blood is reaching the foot.

    • Peroneal Artery: Supplies the outer side of your lower leg.

Tiny Roads (Arterioles): The Traffic Cops

  • As blood moves away from the big highways (arteries), it moves onto smaller streets, then even tiny alleyways.

  • These tiny little vessels are called arterioles.

  • Think of arterioles like little traffic cops with stoplights. They can open or close to control exactly how much blood goes to specific body parts. This is how your body sends more blood to your muscles when you're running, or less blood to your skin when you're cold.

Overview of Blood Flow

  • Blood moves through a pipeline system in the body.

  • These pipelines are called arteries, arterioles, capillaries, venules, and veins.

From Arteries to Capillaries

  • Blood first leaves the heart through arteries, which are large vessels.

  • Arteries then split into smaller vessels called arterioles.

  • Arterioles connect directly to capillaries.

  • Capillaries:

    • Think of them as very tiny tubes, so small that blood cells often pass through one by one.

    • Their main job is to act as a bridge between arterioles and venules.

    • They are where the body's cells get what they need (like oxygen and nutrients) from the blood and where the blood picks up waste (like carbon dioxide).

    • You can find them everywhere in your body.

From Venules to Veins

  • After dropping off oxygen and picking up waste, the blood (now low in oxygen) flows into tiny vessels called venules.

  • Venules:

    • These are the smallest parts of the vein system.

    • They gather the blood from the capillaries.

  • Many venules join together to form larger vessels known as veins.

Major Veins Bringing Blood Back to the Heart

  • As venules merge into veins, the vessels get bigger and bigger until they form two main highway-sized veins that lead back to the heart:

    • Superior Vena Cava:

    • This vein collects blood from the upper body (head and arms).

    • It delivers this blood to the right atrium (an upper chamber) of the heart.

    • Inferior Vena Cava:

    • This vein collects blood from the lower body (abdomen, pelvis, and legs).

    • It also delivers its blood to the right atrium of the heart.

  • Both the superior and inferior venae cavae meet at the right atrium of the heart.

  • From there, the blood continues its journey to the lungs to get fresh oxygen.