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oozing on the muggy shore of the gulf coast
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Greetings auspicious practitioners of the CS art,
LARGE INTESTINE, con`t
The large or thick intestine extends from the ileum to the anus.
Recall that the small intestine is divided into three portions: the
duodenum (about ten inches long), the jejunum (about seven feet long),
and the ileum (about thirteen to fifteen feet long). The iluem connects
to the side of the large intestine. The large intestine is divided into
four parts: the cecum with the veriform appendix,colon,rectum, and anal
canal. The small intestine opens into the side wall of the large
intestine about two and a half inches from the beginning of the large
intestine. This short section is called the cecum. At one time in the
distant past its purpose was the digestion of cellulose, but not in our
present day. The opening from the iluem into the large intestine is
provided with two large projecting lips of mucous membrane forming the
colic or ileoceal valve, which allows passage of material into the large
intestine and prevents passage back into the small intestine, a one way
valve.
The colon, although one continous tube, is subdivided into the
*ascending*,*transverse* or *mesial*, *descending*, and *sigmoid colon*.
The ascending portion ascends on the right side of the abdomen and then
bends to the left (right colic or hepatic flexure), continues across the
abdomen as the transverse colon until reaching the left side. It then
curves beneath the lower end of the spleen (left colic or splenic
flexure) and passes downward as the decending colon. Reaching the left
iliac region on a level with the margin of the crest of the ileum, it
makes a curve like the letter S - hence its name of sigmoid - and
finally ends in the rectum.
The rectum is about five to seven inches long and is continous with
the sigmoid colon and the anul canal. From its origin at the third
sacral vertebra it decends downward and forward along the curve of the
sacrum and coccyx and finally bends sharply backward into the anal
canal.
The anal canal is the terminal portion of the large intestine and is
about one and a half to two inches in length. The external aperture,
called the anus, is guarded by an internal and external sphincter. It is
kept closed except during defecation.
The condition known as *piles* or *hemorrhoids* is brought about by
enlargement of the veins of the anal canal. Piles may be external,
wherein enlargement is of the veins just outside the anal orfice, or
internal, wherein the enlargement is of the veins within the canal.
The construction of the large intestine is the usual four layers,
serous,muscular,submucous areolar, and mucous membrane. The serous layer
does not cover all of the large intestine and not at all at the anal
canal. The muscular layer is two layers of muscle fibers, the external
arranged longitudinally and the internal circularly. The longitudinal
muscles are thicker in some regions than others. The thick areas form
three seperate bands, the *teniae coli*, which extend from the cecum to
the beginning of the rectum, where they spread out and form a
longitudinal layer which encircles this portion. Because these bands are
shorter than the tube they cause it to pucker up into numerous
*sacculations*. The third layer ,the submucous areolar tissue is where
the blood becomes interstitial fluid and the lymph system begins. The
inner most layer, the mucous membrane, does not possess villi and no
circular folds. It contains intestinal glands and solitary lymph nodules
which closely resemble those of the small intestine.
Nerves and blood vessels;
Fibers from both divisions of the autonomic system reach the large
intestine, nerves from the mesenteric and hypogastric plexuses being
distributed in a way similar to that found in the small intestine. The
arteries are derived mainly from the superior and inferior mesenteric
arteries. Branches from the superior mesenteric artery supply the
cecum,appendix, ascending and transverse colon. Branches of the inferior
mesenteric artery supply the desending colon and the rectum. The rectum
also receives branches from the hypogastric arteries. Blood from the
large intestine is returned via the superior and inferior mesenteric
veins, blood from the rectum is returned via the superior rectal, which
join the internal iliac vein.
The process of digestion is continued due to the digestive fluids with
which the food became mixed with in the small intestine. The process of
absorption is continued and the waste products are removed from the
body. Twenty to thirty-six hours are required for the passage of
ingested food material through the gastrointestinal tract of adults who
are on a mixed diet.
The opening from the small intestine into the large is controlled by
the colic valve and the colic sphincter, which is normally in a state of
tone. As food passes the colic valve, the cecum becomes filled, and
gradually the accumulation reaches higher and higher levels in the
ascending colon. The contents of the ascending colon are soft and
semisolid, but in the distal end of the transverse colon they attain the
consistency of feces.
Bless you Bob Lee
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oozing on the muggy shore of the gulf coast
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