Circulatory System
The circulatory system is responsible for transporting and distributing materials - nutrients, water, and oxygen - to billions of cells throughout the entire body, and for helping to carry away cell waste, such as carbon dioxide. Immune Attack’s in-game encyclopedia includes this circulatory system content:
blood vessel network
the heart
arteries and veins
blood cells
platelets
| What do blood vessels do? | Blood vessels make up a network that moves blood from the heart all over the body, and then back again. |
| How many miles of blood vessels do I have? | A child's body contains about 60,000 miles of blood vessels. The average adult's body contains close to 100,000 miles of blood vessels - about four times around the Earth, or nearly half way to the moon. |
| What do capillaries do? | Capillaries are the smallest of the blood vessels. Their wall is composed of a single layer of cells so thin that oxygen and nutrients can pass through them from the blood and into the surrounding tissues. In addition, waste products can pass into the capillaries, removing them from the tissues. In this manner capillaries disperse fresh blood to the tissues and then return it any waste products to the veins. |
| What does the heart do? | The heart is a muscular organ in the body and is the pump that sends blood throughout the body. Blood without oxygen arrives in the right side of the heart which pumps and sends the blood to the lungs to be re-oxygenated. Blood returns from the lungs into the left side of the heart which pumps with so much force that the blood can then travel to the rest of the body. |
| How big is the heart? | The heart is a muscle about the size of your fist. |
| How often does your heart beat? | The average heart beats 72 times per minute. In the course of one day it beats over 100,000 times. In one year the heart beats almost 38 million times, and by the time you are 70 years old, on average, it will have beat 2.5 billion times!. |
| How does the heart pump blood? | A heart's four chambers must beat in an organized manner. This is governed by an electrical impulse. A chamber of the heart contracts when an electrical impulse moves across it. |
| What are arteries? | Arteries are large blood vessels which transport oxygen-rich blood from the heart out to smaller blood vessels. Arteries carry large volumes of blood directly from the heart. They are under a lot of pressure so they are reinforced with a tough wall of connective tissue and many layers of smooth muscle. |
| What are veins? | Veins are large blood vessels that transport oxygen-depleted blood from the tissues back to the heart for re-oxygenation. Veins have layers of smooth muscle and internal valves that help to maintain the forward flow of blood (towards the heart) and prevent any reverse-flow from occurring. |
| What are blood cells? | Blood cells include red blood cells, white blood cells, and platelets. |
| Where are blood cells made? | Blood cells (red blood cells, white blood cells, and platelets) are made in the bone marrow. Bone marrow is a soft tissue inside of our bones that produces blood cells. |
| What does a red blood cell do? | Red blood cells move oxygen from the lungs to the tissues and carbon dioxide from the tissues back to the lungs. |
| How does a red blood cell hold oxygen? | Red blood cells are full of a red colored molecule called hemoglobin. Hemoglobin is able to pick up and hold onto oxygen in the lungs and then let it go in other areas of the body that need it. Red blood cells also help move carbon dioxide ? a waste product of cell activity -- back to the lungs where it is exhaled. |
| How many red blood cells are there? | There are about 25 trillion (25 x 10^12) red blood cells in the adult human body. |
| Where are red blood cells created? | They are created in the bone marrow that?s inside most bones. Special cells in the marrow, called stem cells, produce all types of blood cells, including red blood cells. Newly made red blood cells leave the marrow through blood vessels going through the bone and into the surrounding tissue. |
| How long do red blood cells live? | In humans, red blood cells live only for about 4 months. |
| Where does the name red blood cell come from? | They are named for their color. (The hemoglobin in red blood cells causes them to be bright red.) Red blood cells are also called erythrocytes which comes from "erythros," the Greek word for red. |
| What does a platelet do? | Platelets are small fragments of cells that stick to the edges of damaged blood vessels. They are involved in the initiation of blood clotting. |
| How many platelets are there? | There are about 1.5 trillion (1.5 x 10^12) platelets in an adult human body. |
| Where are platelets created? | Platelets are fragments of large cells, called megakaryoctyes. These large cells reside in the bone marrow and protrude into the surrounding blood vessels. There, fragments of these cells bud off into the blood stream, becoming platelets. |
| How long do platelets live? | Platelets circulate in the blood stream for about 8 ? 10 days. |