Question

3. What happens to your body when you eat something?

1. Explain the science in your own words as if you are describing it to someone with no scientific knowledge (make sure you use appropriate words).

2. Explain all the steps from chewing all the day to the end

Answer 1

So what happens to our body when we eat , in simple the food we eat will be processed by the alimentary canal of our body and nutrients will be absorbed from the processed food and finally excreted. So the steps involved here are : mechanical digestion and chemical digestion, then absorption, assimilation and finally egestion .

First mechanical digestion, the large food particles will be broken down by chewing by our teeth and tongue into smaller particles , salivary glands secretes saliva which also breaks down starch into disaccharides then it will be swallowed into the oropharynx, which is a common passage of food and air . From oropharynx food enters the oesophagus, here through peristalsis the bolus  enters the stomach. From oropharynx food is prevented from entering the larynx through the fold called epiglottis.  

Now from stomach chemical digestion takes place, stomach secretes hcl from oxyntic cells , pepsinogen from chief cells and mucus bicarbonate from goblet cells . Hcl converts pepsinogen to pepsin and mucus bicarbonate precents erosin of stomach wall by the action of hcl thus it acts as a protective mechanism . Pepsin acts on protein molecules and converts into amino acids. Now the processed food is called chyme . Food stays in the stomach for a period of 4 to 5 hours .

Chyme enters small intestine, small intestine is composed of 3 parts , first it enters the duodenum, where hepatopancreatic duct secretes bile and pancreatic juice from liver and pancreas . Bile helps in emulsification of fat and pancreatic juice has trypsinogen, chymotrypsinogen, pancreatic lipase , pancratic amylase . The inactive forms are activated after it enters the duodenum through hapatopancreatic duct which is guarded by sphoncter of oddii. Trypsin and chymotripsin acts on protein converting them to amino acid , pancreatic lipase converts lipids into fatty acids and glycerol. Pancreatic amylase breaks down starch to disaccharides. Small intestine also secretes succus entericus, an intestinal juice which has sucrase, lactase , maltase which breaks down disaccharides to glucose and fructose . Now these broken down glucose molecules, amino acids and fatty acids are absorbed by jejunum and ileum the next 2 parts of small intestine.  

small intestine has specialized mucosal modification that is villi which helps in increasing the surface area for food absorption. Glucose and amino acids are transported through the blood vessels in the villi and fattyacids and glycerol which is insoluble is transported through chylomicrons in the lacteals of villi , which enters the lymphatic stream and finally blood .

Thus from small intestine unabsorbed good enters large intestine, through cecum , ascending colon , transverse colon and descending colon , sigmoid colon and finally rectum . Rectum acts as a temporary storage of fecal matter . Which on stimulation defecated through anal canal and sent out from the body . Absorption of water and certain drugs occurs in the large intestine.  

This this is what happens when we eat , the absorbed glucose , AMINOACID and fatty acids will be utilized by the tissues , this process is called assimilation. Some will also be stored on the liver .