The human digestive system
is formed by a long tube muscular organs which are associated glands and
involved in digestion. Has the following regions; mouth, pharynx,
esophagus, stomach, small intestine, large intestine and anus. The wall of the
digestive tract, the esophagus to the intestine, is composed of four layers:
mucosa, submucosa, muscular and adventitia. Mouth the opening through
which food enters the digestive tract is the mouth. There are teeth and
tongue, which prepare the food for digestion by chewing. Teeth reduce food
into small pieces, mixing them with saliva, which will facilitate the future
action of enzymes. Language the tongue moves food by pushing it toward the
throat to be swallowed. On the surface of the tongue there are dozens of
taste buds, whose sensory cells perceive four primary flavors: bitter, sour or
acid, salty and sweet. Their combination results hundreds of different
flavors. The distribution of four types of taste receptors on the surface
of the tongue, is not homogeneous.
Salivary Glands
The presence of food in the
mouth as well as their vision and smell, stimulate salivary glands secreting
saliva, which contains the enzyme salivary amylase or ptyalin, as well as salts
and other substances. The salivary amylase digest starch and other
polysaccharides (such as glycogen), reducing the molecules of maltose
(disaccharide).Three types of salivary glands release their secretions in the
oral cavity, parotid, submandibular and sublingual.
Pharynx and Esophagus
The pharynx, situated at the
end of the oral cavity is a common channel to the digestive and respiratory
systems: the food pass through it, which goes to the esophagus, and air, which
is directed to the larynx. The esophagus, the tube that connects the
pharynx to the stomach, is located between the lungs behind the heart and
passes through the diaphragm muscle that separates the chest from the abdomen. The
bolus takes 5-10 seconds to traverse it. The stomach produces the gastric
juice, a clear, transparent, highly acidic, containing HCl, mucus, enzymes and
salts. The hydrochloric acid maintaining the pH of the stomach between 0.9
and 2.0. Also dissolves the intercellular cement tissue of the food, thus
assisting the mechanical fragmentation initiated by chewing.Pepsin enzyme most
potent gastric juice, is secreted in the form of pepsinogen. As this is
inactive, does not digest the cells that produce it. By action of the acid
cloródrico the pepsinogen, to be released into the lumen of the stomach,
becomes pepsin, an enzyme that catalyzes the digestion of proteins.
Small Intestine
The small intestine is a
tube with a little over 6 meters long by 4 cm diameter and can be divided into
three regions: duodenum (approximately 25 cm), jejunum (about 5 m) and ileum
(about 1.5 cm.)The upper portion or duodenum has a horseshoe shape and
comprises the pyloric sphincter muscle of the lower stomach through which it
empties its contents in the gut.
Large Intestine
It is the site of absorption
of water both as ingested the digestive secretions. A person drinking
about 1.5 liters of liquids per day, which binds the 8 or 9 liters of water
secretion. Mucosal glands of the large intestine secrete mucus that
lubricates the stool, facilitating their transit through the anus and disposal.
Pancreas
The pancreas is a gland
mixed for about 15 cm long and of triangular shape, located transversely on the
posterior abdominal wall, the loop formed by the duodenum, in the stomach. The
pancreas consists of a head that fits within the duodenum, of a body and a
tapered tail. The external secretion it is directed into the duodenum
through the channels of Wirsung and Santorini. The canal of Wirsung canal
leads alongside the bile duct ampulla of Vater. The pancreas has two
organs closely interwoven: exocrine and endocrine pancreas.
Liver
It is the largest internal
organ, and is still one of the most important. It is the most voluminous
of all organs, weighs about 1.5 kg in adult male and adult female from 1.2 to
1.4 kg. It purplish color, smooth surface and covered by a capsule itself. It
is located in the upper right quadrant of the abdominal cavity. The liver
tissue is composed of minute formations that are called lobes, composed of
columns of liver cells or hepatocytes, surrounded by tiny channels
(canaliculi), by which bile is secreted by hepatocytes. These channels
unite to form the hepatic duct, which together with the duct coming from the
gallbladder to form common bile duct, which discharges its contents into the
duodenum.
By: Rhayanne and JNMarcos