Arteries are connected to veins by capillaries. brainstorming question?

Question

What happens to the oxygenated blood(arteries) & deoxygeated blood by veins when they pass through capillaries.

Answer 1

The blood and circulation

This page tells you about the blood and circulation. There is information on

* What the blood does
* The circulation
* What is in the blood
* White blood cells
* Red blood cells
* Platelets
* How and where blood cells are made
* Your blood and chemotherapy

What is blood for?

The blood circulates throughout the body. It carries nutrients (food) and oxygen to all the cells of the body. And carries away waste products so that they can be removed from the body. Without access to the blood, cells and body tissues die.

The circulation

diagram of circulation

The blood moves around the body inside the circulatory system. This is made up of blood vessels (tubes) called arteries, veins and capillaries. The blood keeps moving through these blood vessels because it is being pumped by the heart.

Arteries carry blood that is full of oxygen from the heart to all parts of the body. As the arteries get further and further away from the heart, they get smaller and smaller.

Eventually they turn into capillaries. These are the smallest blood vessels. They go right into the tissues. Here the blood in the capillaries gives oxygen to the cells and picks up the waste gas, carbon dioxide, from the cells.

The capillaries are connected to the smallest veins in the body. The veins get bigger and bigger as they carry the blood back towards the heart.

The blood passes through the right side of the heart and goes to the lungs where it gets rid of carbon dioxide and picks up more oxygen.

It then passes through the left side of the heart and is pumped back around the body.

The blood always circulates through the body in the same direction. As well as oxygen and carbon dioxide, many other substances are carried in the blood. The blood circulating through the digestive system picks up digested food products and carries them to the liver to be used or stored.

cancer cell stuck in capillary

The circulation can help explain why some cancers nearly always spread to the same place. Cancers of the colon (large bowel) often spread to the liver. This is because blood circulates from the bowel through the liver on its way back to the heart. If there is a cancer in the large bowel, and some cancer cells have found their way into the circulation, they may stick in the liver as the blood passes through. They can then begin to grow into secondary cancers.

The blood

Although blood looks like a red liquid, if some is left in a test tube it separates out into a pale liquid called plasma and a solid layer of blood cells.

plasma

The blood is about 55% plasma and 45% cells. Plasma is mostly water with some proteins and other chemicals dissolved in it. There are three main types of cells in the blood

* White blood cells
* Red blood cells
* Platelets

White blood cells

There are several different types of white cells in the blood in differing amounts. They all play a part in the immune response. This is the response of the body to infection, or anything else the body recognises as 'foreign'. These blood cells can be made very quickly and generally have a short life. Some only live for a few hours, others for days.

There isn't an exact 'normal' figure for blood counts. 'Normal' for a large man wouldn't be the same as for a small woman. But generally the normal white cell count is between about 4,000 and 11,000 per cubic millimeter of blood. If you have surgery or an infection, your white blood cell counts will go up within a day or two.

The most numerous of the white blood cells are the neutrophils. There are between 2,000 and 7,500 of these per cubic millimeter of blood. They are important for fighting infection. If you have chemotherapy, particularly high dose, your doctors will probably talk about your neutrophil count.

The next most numerous are the lymphocytes. A normal lymphocyte count is between 1,300 and 4,000 per cubic millimeter of blood. Lymphocytes are involved in making antibodies as part of the immune response.

There are other white blood cells that are present in smaller numbers in the circulating blood. There are between

* 40 and 400 eosinophils
* 0 and 100 basophils
* 200 and 800 monocytes

per cubic millimeter of blood. As we've said, the range quoted as normal for blood cell counts does vary. These figures have come from the Oxford Handbook of Clinical Medicine.

Red blood cells

Red blood cells give the blood its red colour. There are more than 4 or 5 million of them in every cubic millimeter of blood. A red blood cell can live for up to 120 days.

Red blood cells are able to attach to oxygen to carry it within the circulation to the tissues. When they get to an area where the oxygen is needed, they give it up and pick up carbon dioxide which they carry back to the lungs. A shortage of red blood cells is called anaemia. The role of the red blood cell in carrying oxygen explains why very anaemic people usually feel breathless.

Platelets
Platelets are really bits of much bigger cells called megakaryocytes. A normal platelet count is between 150,000 and 440,000 per cubic millimeter of blood.

Platelets are very important in blood clotting. They clump together to form a plug if bleeding occurs. Then they release other chemicals that help the blood to clot and the blood vessel to be repaired.

How and where blood cells are made
All the different types of blood cells develop from one type of cell called a 'blood stem cell'. In adults, blood stem cells are normally found in the red bone marrow inside the bones. Blood cells are made in the bone marrow in the skull, ribs, sternum (breast bone), spine and pelvis.

where blood cells are made

The stem cells divide and multiply to make the blood cells. These cells differentiate (develop and mature) as they grow into white cells, red cells or platelets. It is now possible to collect stem cells and freeze them. They you have them back after high dose chemotherapy treatment. There is information about stem cell and bone marrow transplants elsewhere in this section of CancerHelp UK.

Answer 2

Blood vessels are the tubes that carry blood around our bodies. There are two types of blood vessels: arteries and veins. Arteries carry blood under high pressure out to all areas of the body after being pumped by the heart.

Veins carry blood that should be under low pressure, on its way back to the heart. An artery does not usually connect directly to a vein. Usually there are very small blood vessels called capillaries that connect an artery to a vein..

Answer 3

when the oxygenated blood from the arteries enter the capillaries, exchange of gases takes place. the oxygen from the blood enters the various organs and the CO2 from the organs passes into the blood to get removed from the body.the deoxygenated blood then flows through the veind to the heart to get oxygenated and is passed into the arteries and the cycle is repeated.

Answer 4

In humans and other mammals, respiratory gas exchange or ventilation is carried out by mechanisms of the lungs. The actual exchange of gases occurs in the alveoli.

Convection occurs over the majority of the transport pathway. Diffusion occurs only over very short distances. The primary force applied in the respiratory tract is supplied by atmospheric pressure. Total atmospheric pressure at sea level is 760 mm Hg, with oxygen (O2) providing a partial pressure (pO2) of 160 mm Hg, 21% by volume, at the entrance of the nares, and an estimated pO2 of 100 mm Hg in the alveoli sac, pressure drop due to conduction loss as oxygen travels along the transport passageway. Atmospheric pressure decreases as altitude increases making effective breathing more difficult at higher altitudes.

Gas exchange occurs only at pulmonary and systemic capillary beds.

CO2 is a result of cellular respiration. The concentration of this gas in the breath can be measured using a capnograph. As a secondary measurement, respiration rate can be derived from a CO2 breath waveform.

Answer 5

As the RBC (red cell) passes, no squeezes through a capillary, it exchanges its payload of oxygen for Co2 and waste, then caries it out through the veins to be excreted.