What are 3 things transported by the circulatory system?

The Human Road Network

A classic way to think about the human body is to think about it as like a miniature city. Individuals in a city are like the different cells of your body. Groups of individuals work in offices, doing different jobs just like organ systems, which are made of many cells perform different jobs within your own body.  So what is the city equivalent of the circulatory system?

The circulatory system can be described as the road network within our city example.  Like a road system, it carries food to individual homes and carries waste away.  There are major highways (arteries and veins), and side alley ways (capillaries).  In our bodies, blood is a specialized bodily fluid that flows down the roads which carries nutrients and oxygen to cells and carries wastes like carbon dioxide and urea away.

An average human has about 5 liters of blood that flows through the circulator

y system.  Some of the major steps of the circulatory system include the passage through the heart (coronary circulation), the movement to the lungs where it picks up oxygen (pulmonary circulation), and the transport of that oxygen to the rest of the body (systemic circulation).

Circulatory System Video Introduction

For our middle grades series with Pearson publishing we created a video for every topic in human biology. Pearson was kind enough to let us release a few, just so that you can get a taste for what we’ve been up to. In this video, we start off by using the road analogy to talk about the circulatory system. Jonas and Haley then take us all on an amazing journey through some of the most interesting facts about this human biology topic. We hope you enjoy it, we had fun making it!

http://blip.tv/play/htl2gr%2BQbAA

Some of the biggest parts of the circulatory system include the following:

• The Blood
• The Heart
• Blood Vessels – Arteries, Veins, and Capillaries

Circulatory System Quick Facts

• A single drop of blood contains 5,000,000 Red Blood Cells, 10,000 White Blood Cells, and 250,000 Platelets.
• Your blood vessels are so long that you could wrap them around the earth twice!
• The average human heart will beat about 3,000,000,000 times!
• A single red blood cell will circulate around the body in about 20 seconds.
• Blood is created in our bones!
• Humans have red blood – it appears brighter red when it is oxygen rich and darker red when it is oxygen poor – we never have blue blood.
• Some animals do have blue blood – instead of hemoglobin they have hemocyanin.

Created: March 12, 2010; Last Update: January 31, 2019; Next update: 2022.

The blood circulatory system (cardiovascular system) delivers nutrients and oxygen to all cells in the body. It consists of the heart and the blood vessels running through the entire body. The arteries carry blood away from the heart; the veins carry it back to the heart. The system of blood vessels resembles a tree: The “trunk” – the main artery (aorta) – branches into large arteries, which lead to smaller and smaller vessels. The smallest arteries end in a network of tiny vessels known as the capillary network.

There isn't only one blood circulatory system in the human body, but two, which are connected: The systemic circulation provides organs, tissues and cells with blood so that they get oxygen and other vital substances. The pulmonary circulation is where the fresh oxygen we breathe in enters the blood. At the same time, carbon dioxide is released from the blood.

Blood circulation starts when the heart relaxes between two heartbeats: The blood flows from both atria (the upper two chambers of the heart) into the ventricles (the lower two chambers), which then expand. The following phase is called the ejection period, which is when both ventricles pump the blood into the large arteries.

In the systemic circulation, the left ventricle pumps oxygen-rich blood into the main artery (aorta). The blood travels from the main artery to larger and smaller arteries and into the capillary network. There the blood drops off oxygen, nutrients and other important substances and picks up carbon dioxide and waste products. The blood, which is now low in oxygen, is collected in veins and travels to the right atrium and into the right ventricle.

This is where pulmonary circulation begins: The right ventricle pumps low-oxygen blood into the pulmonary artery, which branches off into smaller and smaller arteries and capillaries. The capillaries form a fine network around the pulmonary vesicles (grape-like air sacs at the end of the airways). This is where carbon dioxide is released from the blood into the air inside the pulmonary vesicles, and fresh oxygen enters the bloodstream. When we breathe out, carbon dioxide leaves our body. Oxygen-rich blood travels through the pulmonary veins and the left atrium into the left ventricle. The next heartbeat starts a new cycle of systemic circulation.

Sources

• Menche N (Ed). Biologie Anatomie Physiologie. Munich: Urban und Fischer; 2016.

• Pschyrembel. Klinisches Wörterbuch. Berlin: De Gruyter; 2017.

• Schmidt R, Lang F, Heckmann M. Physiologie des Menschen: mit Pathophysiologie. Berlin: Springer; 2017.

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The function of the circulatory system is to transport materials around the body. There are many materials that need transporting. These include oxygen, carbon dioxide, nutrients (such as glucose and amino acids), hormones and waste chemicals such as urea. These substances are transported in a medium called blood through the body through tubes called blood vessels. The blood is forced around these vessels by a pump - the heart.

There are different types of blood vessels.

• Arteries - take blood away from the heart.
• Veins - take blood towards the heart.
• Capillaries - small vessels connecting arteries & veins.

The blood travels around the circulatory system in a series of parallel circuits so that the blood travels from the heart, through an organ before returning to the heart. If the blood went through each organ in turn the organs near the end of the chain would not receive as many nutrients as the organs first in line. This is because the first organs would take out the nutrients leaving fewer for the organs that follow.

There is one exception to this. The blood leaving the stomach & intestines first goes through the liver. The Liver receives its own blood supply, but this second supply gives the liver a chance to absorb any extra nutrients the body needs to store as well as neutralising any toxins that have been absorbed before they can wreak havoc throughout the body.

The heart is a pump, usually beating about 60 to 100 times per minute. With each heartbeat, the heart sends blood throughout our bodies, carrying oxygen to every cell. After delivering the oxygen, the blood returns to the heart. The heart then sends the blood to the lungs to pick up more oxygen. This cycle repeats over and over again.

What Does the Circulatory System Do?

The circulatory system is made up of blood vessels that carry blood away from and towards the heart. Arteries carry blood away from the heart and veins carry blood back to the heart.

The circulatory system carries oxygen, nutrients, and to cells, and removes waste products, like carbon dioxide. These roadways travel in one direction only, to keep things going where they should.

What Are the Parts of the Heart?

The heart has four chambers — two on top and two on bottom:

• The two bottom chambers are the right ventricle and the left ventricle. These pump blood out of the heart. A wall called the interventricular septum is between the two ventricles.
• The two top chambers are the right atrium and the left atrium. They receive the blood entering the heart. A wall called the interatrial septum is between the atria.

The atria are separated from the ventricles by the atrioventricular valves:

• The tricuspid valve separates the right atrium from the right ventricle.
• The mitral valve separates the left atrium from the left ventricle.

Two valves also separate the ventricles from the large blood vessels that carry blood leaving the heart:

• The pulmonic valve is between the right ventricle and the pulmonary artery, which carries blood to the lungs.
• The aortic valve is between the left ventricle and the aorta, which carries blood to the body.

What Are the Parts of the Circulatory System?

Two pathways come from the heart:

• The pulmonary circulation is a short loop from the heart to the lungs and back again.
• The systemic circulation carries blood from the heart to all the other parts of the body and back again.

In pulmonary circulation:

• The pulmonary artery is a big artery that comes from the heart. It splits into two main branches, and brings blood from the heart to the lungs. At the lungs, the blood picks up oxygen and drops off carbon dioxide. The blood then returns to the heart through the pulmonary veins.

In systemic circulation:

• Next, blood that returns to the heart has picked up lots of oxygen from the lungs. So it can now go out to the body. The aorta is a big artery that leaves the heart carrying this oxygenated blood. Branches off of the aorta send blood to the muscles of the heart itself, as well as all other parts of the body. Like a tree, the branches gets smaller and smaller as they get farther from the aorta.

  At each body part, a network of tiny blood vessels called capillaries connects the very small artery branches to very small veins. The capillaries have very thin walls, and through them, nutrients and oxygen are delivered to the cells. Waste products are brought into the capillaries.

  Capillaries then lead into small veins. Small veins lead to larger and larger veins as the blood approaches the heart. Valves in the veins keep blood flowing in the correct direction. Two large veins that lead into the heart are the superior vena cava and inferior vena cava. (The terms superior and inferior don't mean that one vein is better than the other, but that they're located above and below the heart.)

  Once the blood is back in the heart, it needs to re-enter the pulmonary circulation and go back to the lungs to drop off the carbon dioxide and pick up more oxygen.

How Does the Heart Beat?

The heart gets messages from the body that tell it when to pump more or less blood depending on a person's needs. For example, when you're sleeping, it pumps just enough to provide for the lower amounts of oxygen needed by your body at rest. But when you're exercising, the heart pumps faster so that your muscles get more oxygen and can work harder.

How the heart beats is controlled by a system of electrical signals in the heart. The sinus (or sinoatrial) node is a small area of tissue in the wall of the right atrium. It sends out an electrical signal to start the contracting (pumping) of the heart muscle. This node is called the pacemaker of the heart because it sets the rate of the heartbeat and causes the rest of the heart to contract in its rhythm.

These electrical impulses make the atria contract first. Then the impulses travel down to the atrioventricular (or AV) node, which acts as a kind of relay station. From here, the electrical signal travels through the right and left ventricles, making them contract.

One complete heartbeat is made up of two phases:

1. The first phase is called systole (pronounced: SISS-tuh-lee). This is when the ventricles contract and pump blood into the aorta and pulmonary artery. During systole, the atrioventricular valves close, creating the first sound (the lub) of a heartbeat. When the atrioventricular valves close, it keeps the blood from going back up into the atria. During this time, the aortic and pulmonary valves are open to allow blood into the aorta and pulmonary artery. When the ventricles finish contracting, the aortic and pulmonary valves close to prevent blood from flowing back into the ventricles. These valves closing is what creates the second sound (the dub) of a heartbeat.
2. The second phase is called diastole (pronounced: die-AS-tuh-lee). This is when the atrioventricular valves open and the ventricles relax. This allows the ventricles to fill with blood from the atria, and get ready for the next heartbeat.

How Can I Help Keep My Heart Healthy?

To help keep your heart healthy:

• Get plenty of exercise.
• Eat a nutritious diet.
• Reach and keep a healthy weight.
• If you smoke, quit.
• Go for regular medical checkups.
• Tell the doctor about any family history of heart problems.

Let the doctor know if you have any chest pain, trouble breathing, or dizzy or fainting spells; or if you feel like your heart sometimes goes really fast or skips a beat.