Process of Digestion by Mohamed Adam

Mouth-

mohamed_320 — 2014-04-14 17:43:52 UTC

The mouth is where digestion begins. Food is chewed and torn up (mastication) by the teeth until it becomes a bolus. The mouth consists of three salivary glands that secrete salivary amylase to begin the break down of starch/carbs. This bolus is then swallowed (saliva helps lubricate the path for the bolus).

Esophagus

mohamed_320 — 2014-04-14 17:45:49 UTC

The esophagus is the long tube held up by rings of cartilage. The esophagus uses muscular contractions called peristalsis to force the bolus down into the stomach. At the end of the oesophagus there is a sphincter that will open to allow food to enter the stomach (it is called the lower esophagus sphincter or cardiac sphincter).

Stomach

mohamed_320 — 2014-04-14 17:47:00 UTC

The stomach is lined with two cell types that do all the hard work: parietal and chief cells.Parietal cells secrete hydrogen (H⁺) and chloride (Cl^-) ions to make hydrochloric acid (HCl) molecules, which create a really acidic environment (in the neighborhood of pH = 2–3). The stomach'schief cells join this acidic pool party by secreting a compound called pepsinogen. When pepsinogen enters an acidic solution (like, say, the inside of a stomach), it is converted into the protein digesting enzyme,pepsin In case you wanted to know, bolus is the more technical term for a glob of partially digested food working its way through the body.

**A thin layer of mucus prevents all this acid from harming these parietal and chief cells lining the stomach. If the mucus gets too thin or deteriorates altogether, these acids wreak havoc on the stomach lining, and cause painful ulcers.)

Liver and Gallbladder

mohamed_320 — 2014-04-14 17:50:26 UTC

The liver produces a substance called bile; bile aids in the digestion and break down of fats. The bile produced by the liver is sent into the gall bladder where it is stored until the food/chyme passes by. It will secrete this bile once the food has reached the first section of the small intestine (duodenum).

Pancreas

mohamed_320 — 2014-04-14 17:51:05 UTC

The pancreas works an extra job on the side, producing other enzymes to complete this digestion job. Since the pancreas is so close to the small intestine, it makes sense that it would pitch in and help when needed. Pancreatic amylases are secreted into the small intestine where they will continue the hard work that was started in the mouth. They'll break sugars down even further, to the disaccharide (now they are two sugar molecules big) level. There are also pancreatic enzymes that specifically break bonds in polypeptides, resulting in various individual amino acids.

Just like the gall bladder, the pancreas will secrete its substances once the food has reached the duodenum.

The pancreas secretes a variety of digestive enzymes that will help break down the food (amylase, protease, lipase, etc..).

The Small intestine

mohamed_320 — 2014-04-14 17:54:01 UTC

The S.I. is composed of three parts; duodenum, jejunum and the ileum. When the food has reached the duodenum, the digestive enzymes from the pancreas and the bile from the gall bladder start to work on the food;
Amylase breaks down carbohydrates/starch into glucose.
Protease breaks down proteins into amino acids.
Lipase breaks down fats/lipids (with the aid of bile) into triglycerides.
The small intestine is lined with millions of finger-like projections called villi, and on these are microvilli. These increase surface area enormously so that maximum absorption of nutrients is achieved. A network of capillaries lie beneath the small intestines so that as soon as nutrients are absorbed by the villi, they go straight into the bloodstream.

Large Intestine

mohamed_320 — 2014-04-14 17:58:35 UTC

The caecum makes up the connection between the small and large intestine.

*Up to 1.5 meters long and 7.5 cm wide.

Contains a series of pouches that have a puckered appearance and also contains smooth muscle fibres for peristalsis

*Houses anaerobic bacteria called E.coli which synthesizes vitamins B, and K

The next part is the colon; this is where water, vitamins and minerals from digestion is reabsorbed and the faeces are produced (undigested matter, fibre, vitamins and a bit of water harden to make up the faeces). The L.I also consists of some villi/microvilli so that water/vitamins/minerals can be absorbed. Once the faeces have been made, it is passed into the rectum.
The rectum temporarily stores faeces until you decide to go to the toilet. It consists of 'transverse folds' that hold the faeces in place before being excreted.

Anus/Rectum

mohamed_320 — 2014-04-14 18:02:13 UTC

This is where the faeces are excreted out into the 'external environment'. The anus consists of sphincters that will open when the faeces are passing through.

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References:

mohamed_320 — 2014-04-14 18:48:24 UTC

http://www.enchantedlearning.com/subjects/anatomy/digestive/

http://www.innerbody.com/image/digeov.html

http://www.webmd.com/digestive-disorders/digestive-system

http://en.wikipedia.org/wiki/Digestion

Begining

mohamed_320 — 2014-04-14 19:00:58 UTC

END

mohamed_320 — 2014-04-14 19:01:13 UTC