Mouth
The mouth is the beginning of the digestive tract. In fact, digestion starts here as soon as you take the first bite of a meal. Chewing breaks the food into pieces that are more easily digested, while saliva mixes with food to begin the process of breaking it down into a form your body can absorb and use.Throat
Also called the pharynx, the throat is the next destination for food you've eaten. From here, food travels to the esophagus or swallowing tube.Esophagus
The esophagus is a muscular tube extending from the pharynx to the stomach. By means of a series of contractions, called peristalsis, the esophagus delivers food to the stomach. Just before the connection to the stomach there is a "zone of high pressure," called the lower esophageal sphincter; this is a "valve" meant to keep food from passing backwards into the esophagus.Stomach
The stomach is a sac-like organ with strong muscular walls. In addition to holding the food, it's also a mixer and grinder. The stomach secretes acid and powerful enzymes that continue the process of breaking down the food. When it leaves the stomach, food is the consistency of a liquid or paste. From there the food moves to the small intestine.Small Intestine
Made
up of three segments, the duodenum, jejunum, and ileum, the small
intestine is a long tube loosely coiled in the abdomen (spread out, it
would be more than 20 feet long). The small intestine continues the
process of breaking down food by using enzymes released by the pancreas
and bile from the liver. Bile is a compound that aids in the digestion
of fat and eliminates waste products from the blood. Peristalsis
(contractions) is also at work in this organ, moving food through and
mixing it up with digestive secretions. The duodenum is largely
responsible for continuing the process of breaking down food, with the
jejunum and ileum being mainly responsible for the absorption of
nutrients into the bloodstream.
Three organs play a pivotal role in helping the stomach and small intestine digest food:
Pancreas
Among
other functions, the oblong pancreas secretes enzymes into the small
intestine. These enzymes break down protein, fat, and carbohydrates from
the food we eat.
Liver
The
liver has many functions, but two of its main functions within the
digestive system are to make and secrete bile, and to cleanse and purify
the blood coming from the small intestine containing the nutrients just
absorbed.
Gallbladder
The
gallbladder is a pear-shaped reservoir that sits just under the liver
and stores bile. Bile is made in the liver then travels to the
gallbladder through a channel called the cystic duct. During a meal, the
gallbladder contracts, sending bile to the small intestine.
Once
the nutrients have been absorbed and the leftover liquid has passed
through the small intestine, what is left of the food you ate is handed
over to the large intestine, or colon.
Rectum
The rectum (Latin for "straight") is an 8-inch chamber that connects the colon to the anus. It is the rectum's job to receive stool from the colon, to let you know there is stool to be evacuated, and to hold the stool until evacuation happens. When anything (gas or stool) comes into the rectum, sensors send a message to the brain. The brain then decides if the rectal contents can be released or not. If they can, the sphincters (muscles) relax and the rectum contracts, expelling its contents. If the contents cannot be expelled, the sphincters contract and the rectum accommodates, so that the sensation temporarily goes away.Anus
The
anus is the last part of the digestive tract. It consists of the pelvic
floor muscles and the two anal sphincters (internal and external
muscles). The lining of the upper anus is specialized to detect rectal
contents. It lets us know whether the contents are liquid, gas, or
solid. The pelvic floor muscle creates an angle between the rectum and
the anus that stops stool from coming out when it is not supposed to.
The anal sphincters provide fine control of stool. The internal
sphincter keeps us from going to the bathroom when we are asleep, or
otherwise unaware of the presence of stool. When we get an urge to go to
the bathroom, we rely on our external sphincter to keep the stool in
until we can get to the toilet.
0 comments:
Post a Comment