I know travel via the capillaries through the soft and spongy lungs, to the pulmonary vein, as I travel along the vein at low pressure, I feel myself being dragged backwards slightly but I was soon stopped by a valve, a valve prevents the back flow of blood. I flowed through the vein, right into the left atrium of the heart. I felt something contract and push me through the bicuspid valve into the left ventricle, the valve then snaps shut. The left ventricle then contracts, forcing me along with the others into the aorta; the semi-lunar valve fills with blood to close. I then travel down the dorsal aorta at very high pressure, the arteries thick, elastic walls withstand this. The high pressure causes a pulse that can be felt especially in the neck and wrist.
I was now heading towards the gut, as I passed the gut wall, the small and soluble, digested food molecules pass through into the blood stream I am situated in, my job as part of the blood was to carry the small, dissolved minerals around the body, to the working cells. The molecules were the products of digestion.
Digestion starts in the mouth, our teeth begin breaking up the food, then we swallow it and pass it through to the oesophagus (also known as the gullet), it is a circular tube with muscles in its walls. The function of the gullet is to pass food down to your stomach, it does this by the muscles in the walls contracting and squeezing behind the food to push it along. In front of the food the muscles relax. This movement of food down the gut is called peristalsis. The food now has reached the stomach, which has muscular walls to churn up the food and mix it with gastric juices that the stomach itself produces. After 2-3 hours of churning, the food is a runny liquid. A ring of muscle opens to let the food squirt out a little at a time, it passes into the small intestine. From here it travels down the duodenum part of the small intestine, the digestion is completed here and the food is absorbed into the bloodstream. The small intestine is well designed for absorption because the inner surface is covered in tiny finger like projections called villi, this creates a larger surface area and therefore a better blood supply, making it easy for the digested food to pass through the inner-lining into the blood vessels. The digested food passes on through the ileum part of the small intestine, up the ascending colon, through the transverse colon and down the descending colon. In the large intestine, there is not much useful food left, it’s mainly fibre, dead cells, bacteria and water. As this passes along the large intestine some of the excess water is re-absorbed into the blood. .The end roduct at this point is a nearly solid waste called faeces. The faeces are then stored in the rectum before it passes away, they are then egested through the anus.
Now that the food was loaded up, we carried on our journey and reached the hepatic portal vein in super fast time and travelled through it till we reached the liver. The liverproduces bile. The bile breaks up oil droplets to make them easier to digest. It also neutralizes stomach acid to get the food ready for more enzymes. I travel through the liver and proceed along the hepatic vein leading on to the vena cava. At the vena cava, we branched off towards a muscle in the arm. When I reached the muscle , my red blood cell diffused oxygen and its glucose supply via the partialtly permeable membrane. I then watched a chemical reaction take place, as the glucose and the oxygen react to produce carbon dioxide and energy by the process of respiration. This process took nplace in the mitochondria which is in the cell cytoplasm. The cells used the energy for all the chemical reactions in the body. The bi-product carbon dfioxide diffused into the plasma ; a yellow coloured watery liquid in the blood in which the cells float in. I have now attached myself to a particle of carbon dioxide, icarry on my journey back towards the right side of the heart with deoxygenated blood, I enter the right atrium via the vena cava, the blood coming back from the body is travelling very slow because of the lack of energy. The right atrium contracts and pushes bood through the tricuspid valve into the right ventricle (a chamber), i then get pushed up through the semi-lunar valve out of the pulmonary artery.
