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oozing on the muggy shore of the gulf coast
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Welcome hob and nobers of the CS art,
SMALL INTESTINE, food changes,
The chyme entering the duodenum after an ordinary meal is normally
free from course particles of food and is acid in reaction, both the
hydrochloric acid and the lactic acid produced by fermentation
contributing to this condition. Much of the food is undigested. The
proteins are partly digested; some progress has been made in hydrolyzing
starch; fats have been liquefied and mixed with other food but not
hydrolyzed themselfs. If milk is part of the diet, it will have been
curdled and redissolved. It is in the small intestine that this mixture
undergoes the greatest digestive changes. These changes which constitute
intestinal digestion are effected by: (1) movement of the
intestines,(2)the pancreatic fluid, (3) the succus entericus, or
secretion of the intestinal glands,and (4) the bile. All of these act
simultaneously. The pancreatic fluid and bile enter the intestine about
7-10 cm. beyond the pylorus, therefore foods in the small intestine are
subject to the mixture of pancreatic fluid,bile and intestinal fluid
throughout its length.
Movements of the small intestine are described as, peristaltic,
rhythmical, and pendular.
Peristalsis may be defined as a wave of dilatation brought about by the
contraction of longitudinal muscles, followed by a wave of constriction
caused by the contraction of circular muscles. The purpose is to pass
the food slowly forward (myenteric reflex). Peristaltic waves pass very
slowly along short distances of the small intestine, with an occasional
rapid wave know as the peristaltic rush,which moves food along greater
distances.
The rhythmical movements consist of a series of local constrictions of
the intestinal wall which occur rhythmically at points where masses of
food lie. These constrictions divide the food into segments. Within a
few seconds each of these segments is halved, and the corresponding
halves of adjoining segments unite. Again constrictions occur, and these
newly formed segments are divided, and the halves re-form. In this way
every particle of food is brought into intimate contact with the mucosa
and is thoroughly mixed with the digestive fluids.
Pendular movements are constrictions which move onward or backward for
short distances,gradually moving the chyme forward and backward over
short distances in the small intestine.
The varied muscular movements of the small intestine increase the
blood supply, bring material for secretion and removing absorbed
materials faster. They assist the minute glands in emptying their
secretion, mix the fluids and food intimately,and bring fresh absorbable
material constantly to the mucosa, thereby increasing absorption.
PANCREATIC SECRETION
Pancreatic secretion (like gastric secretion) consists of two parts;
(1) a nervous secretion caused by the secretory fibers in the vagus and
splanchnic nerves,(2) a chemical secretion, due to the action of a
hormone,secretin. It is thought that secretin exists in the mucous
membrane of the duodenum (or jejunum) and is liberated by the bile which
pores into the intestine during gastric digestion. The bile salts,as
they are absorbed, carry the secretin into the blood, and in this way it
reaches the pancreas. The nervous secretion provides pancreatic fluid in
the early stages of intestinal digestion and the chemical secretion
maintains the flow until all the stomach contents reach the duodenum.
The nervous secretion of pancreatic fluid is thick, and rich in
enzymes and proteins. The chemical secretion is thin,watery,contains
little enzyme or proteins, and is alkaline. Pancreatic fluid contains
three groups of enzymes, which act on proteins,carbohydrates, and fats.
They are trypsin and erepsin, amylase, and lipase.
The proteolytic enzymes, trypsin and erepsin, hydrolyze the protein
molecule to its constituent amino acids (breaks bonds). Trypsin
hydrolyzes proteins into proteoses, peptones, and polypeptides. Erepsin
hydrolyzes (breaks bonds) the peptides to amino acids. Erepsin belongs
to a class of enzymes that act on simpler peptids, hydrolyzing them to
amino acids.
The amylolytic enzyme (amylase) causes hydrolysis of starch with the
production of maltose. Maltose is further acted upon by maltase and is
hydrolyzed to dextrose.
The lipolytic enzyme (lipase) hydrolyzes fats to glycerin and fatty
acids saponizing them to form soaps. The process of hydrolysis is
preceded by emulsification, which is dependent upon the formation of
soaps. The lipase splits some of the fats to fatty acids and glycerin.
The fatty acids combine with the alkaline salts (bile) to form soaps
(saponification). This soap aids in the emulsification of the fat.
Emulsification increases the surface area of the fat exposed to the
lipase and is a mechanical preparation for the further action of lipase.
The glycerin and fatty acids producded by the action of the lipase are
absorbed by the epithelium of the intestine. Fatty acids form soluble
and diffusible compounds with the bile salts and are absorbed in this
form. After absorption the fatty acids and glycerin again combine to
form fat for storage in the tissues. We eat fats,digest them into fatty
acids and glycerin,absorb them into our tissues,then recombine the fatty
acid and glycerin into fat in our tissues for storage. To use the fat in
storage it is again broken down into fatty acids and glycerin for use by
the body. The action of lipase is reversible, it causes the spliting of
fats and the synthesis of the split products. Lipase works during the
metabolism or the storage of fat. Lipase is found in the blood and in
many tissues.
Bless you Bob Lee
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oozing on the muggy shore of the gulf coast
[email protected]
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