BGZ2004
Problem 3
1. How is the stool normally regulated?
Mouth
You break ood into smaller pieces by chewing, salivary amylase breaks down
starch into smaller molecules. Saliva and other fluids blend with the food to form
a bolus, a chewed, moistened lump of food that is soft and easy to swallow. The
bolus moves after swallowing through the esophagus to the stomach, there it will
be digested further.
Stomach
The bolus enters the stomach through the esophageal sphincter.
- Hydrochloric acid makes trhe stomach acidic. Mucus is secreted.
Hydrochloric acid:
o Breakes down proteins
o Converts pepsinogen into pepsin
- Gastric lipase: digestion of lipids
- Gastric: stimulates gastric secretion and motility
- Intrinsic factor
The stomach releases the cchyme through the pyloric sphincter into the small
intestine.
Large intestine; here the food comes eventually.
Absorption in the large intestine: formation of feces
About 1500 ml of chime comes into the large intestine every day. Most of the
water and electrolytes are absorbed in the colon in feces is usually less than
100 ml of fluid excreted. Only 1-5 milliequivalents of Na+ and Cl- ions are lost in
feces, the rest of ions is absorbed.
Most of the absorption occurs in the proximal half of the colon: absorbing
colon. The distal colon functions principally for feces storage until it is time for
feces exretion: storage colon.
The mucosa of the large intestine has a high capacity for active absorption of
sodium, which also causes chloride absorption.
The tight junctions between the cells in the epithelial are tighter in the large
intestinal. This prevents back-diffusion of ions through the junctions. Here by,
sodium ions can be absorbed better and against a higher concentration gradient
than in the small intestine. The mucosa secretes bicarbonate ions while it
absorbs chloride ions. It neutralizes the acidic products of bacterial action. By
sodium and chloride absorption, an osmotic gradient is created across the large
intestinal mucosa, which causes absorption of water.
The large intestine can absorb max 5-8 liters of fluid and electrolytes each day.
When the total quantity entering the large intestine secretion exceeds this, it
appears as diarrhea. Toxins from cholera or other bacterial infections often cause
the crypts in the terminal ileum and in the large intestine to secrete 10 or more
liters each day.
Bacterial action in colon
Bacteria can digest small amounts of cellulose. This provides some energy, which
is significant.
As result of bacterial activity are also other substances formed, such as vitamine
K, B12, thiamine, riboflavin and gases that contribute to flatus in the colon
(carbon dioxide, hydrogen gas, methane).
Composition of the feces
They are normally about ¾ water and ¼ solid matter that itself is composed of
about 30% bacteria, 10-20% fat, 10-20% inorganic matter, 2-3% protein and 30%
,undigested roughade from digestive juices (bile pigment and sloughed epithelial
cells). The brown color is caused by stercobilin and urobilin, derivatives of
bilirubin. The odor is caused by products of bacterial action, which vary from
person to person. This depends on the food eaten and on the person’s colonic
bacterial flora. The odoriferous products are: indole, skatole, mercaptans and
hydrogen sulfide.
The principal functions of the colon are:
- Absorption of water and electrolytes from the chime to form solid feces
mostly the proximal half
- Storage of fecal matter until it can be expelled mostly the distal half
Mixing movements: large circular constrictions occur, about 2,5 cm of the circular
muscle contracts. Also the longitudinal muscle contracts. These contractions
cause haustrations: baglike sacs.
The fecal material is dug into and rolled over, all material is gradually exposed to
the mucosal surface or the large intestine, and fluids and dissolved substances
are absorbed until only 80-200 millimeters of feces are expelled each day.
Propulsive movements:
Much of the propulsion in the cecum and ascending colon results from the slow
but persistent haustral contractions, requiring 8-15 hours to move the chime from
the ileocecal valve through the colon. The chime becomes fecal: a semisolid slush
instead of semifluid.
From the cecum to the sigmoid, mass movements can take over the propulsive
role, mostly 15 minutes during first hour after breakfast. This is a modified type
of peristalsis:
- First, a constrictive ring occurs in the transverse colon
- The 20 or more cm distal to the ring lose their haustrations and contract as
a unit
Mass movements after meals is facilitated by gastrolic and duodenocolic reflexes.
The reflexes are transmitted by way of the autonomic nervous system.
Most of the time, the rectum is empty of feces. A weak sphincter exists about 20
cm from the anus at the juncture between the sigmoid colon and the rectum. This
gives resistance to filling of the rectum. When a mass movement forces feces
, into the rectum, the desire for defecation occurs; reflex contraction of the rectum
and relaxation of anal sphincters occurs.
Continuous flowing of feces through the anus is prevented by constriction of:
- An internal anal sphincter: circular smooth muscle that lies immediately
inside the anus
- An external anal sphincter; striated muscle. This is controlled by nerve
fibers in the pudendal nerve, which is part of the somatic nervous system
and therefore is under voluntary, subconscious control. (subconsious: it is
always kept constricted unless conscious signals inhibit the constriction).
2. What happens when you have diarrhea and how can you cure
it?(causes)
Diarrhea results from rapid movement of fecal matter through the large intestine.
Several causes of diarrhea are:
- Enteritis: This means inflammation caused either by a virus or by bacteria
in the intestinal tract.
o Production of toxins
o Damage
In usual infectious diarrhea, the infection is in the large intestine and the distal
end of the ileum. The mucosa (where infection is present), becomes very
irritated and its rate of secretion becomes greatly enhanced. Motility of
intestinal wall increases. The result is that large quantities of fluid are made
available for washing the infectious agent towards the anus, also strong
propulsive movements bring this fluid forward.
o Diarrhea caused by cholera is of special interest, this toxin directly
stimulates excessive secretion of electrolytes and fluid is the distal
ileum and colon. This can go to 10-12 liters per day. Several days
can ensure death. Therapy: replace fluid and electrolytes as rapidly
as they are lost, by giving solutions (oplossingen met electrolyten).
- Psychogenic emotional diarrhea: during periods of nervous tension. This is
caused by excessive stimulation of the parasympathic nervous system,
which excites motility and excess secretion of mucus in the distal colon.
This can cause diarrhea.
- Ulcerative colitis: areas of the walls of the large intestine become inflamed
and ulcerated. Motility of colon is to great, mass movements occur to
often. The secretions of the colon also are enhanced. Repeated diarrheal
bowel movements. The cause is unknown, but there’s a strong hereditary
tendency for susceptibility.
Peristaltic rush (irritation of the intestinal mucosa powerful and rapid
peristalsis) can cause serious diarrhea.
For cure, also ORS or medicines are important.
3. What happens when you have constipation, what causes it and
how can you cure it?
Constipation: slow movement of feces through the large intestine, large amount
of dry, hard feces in the descending colon that accumulates because of over-
absorption of fluid. Any pathology that obstructs movement of intestinal
contents, can cause constipation. A frequent cause is irregular bowel habits (in
going to toilet) that develop through a lifetime of inhibition of normal defecation
reflexes. If one does not allow these natural reflexes to occur, the reflexes
become less strong and the colon becomes atonic.
Problem 3
1. How is the stool normally regulated?
Mouth
You break ood into smaller pieces by chewing, salivary amylase breaks down
starch into smaller molecules. Saliva and other fluids blend with the food to form
a bolus, a chewed, moistened lump of food that is soft and easy to swallow. The
bolus moves after swallowing through the esophagus to the stomach, there it will
be digested further.
Stomach
The bolus enters the stomach through the esophageal sphincter.
- Hydrochloric acid makes trhe stomach acidic. Mucus is secreted.
Hydrochloric acid:
o Breakes down proteins
o Converts pepsinogen into pepsin
- Gastric lipase: digestion of lipids
- Gastric: stimulates gastric secretion and motility
- Intrinsic factor
The stomach releases the cchyme through the pyloric sphincter into the small
intestine.
Large intestine; here the food comes eventually.
Absorption in the large intestine: formation of feces
About 1500 ml of chime comes into the large intestine every day. Most of the
water and electrolytes are absorbed in the colon in feces is usually less than
100 ml of fluid excreted. Only 1-5 milliequivalents of Na+ and Cl- ions are lost in
feces, the rest of ions is absorbed.
Most of the absorption occurs in the proximal half of the colon: absorbing
colon. The distal colon functions principally for feces storage until it is time for
feces exretion: storage colon.
The mucosa of the large intestine has a high capacity for active absorption of
sodium, which also causes chloride absorption.
The tight junctions between the cells in the epithelial are tighter in the large
intestinal. This prevents back-diffusion of ions through the junctions. Here by,
sodium ions can be absorbed better and against a higher concentration gradient
than in the small intestine. The mucosa secretes bicarbonate ions while it
absorbs chloride ions. It neutralizes the acidic products of bacterial action. By
sodium and chloride absorption, an osmotic gradient is created across the large
intestinal mucosa, which causes absorption of water.
The large intestine can absorb max 5-8 liters of fluid and electrolytes each day.
When the total quantity entering the large intestine secretion exceeds this, it
appears as diarrhea. Toxins from cholera or other bacterial infections often cause
the crypts in the terminal ileum and in the large intestine to secrete 10 or more
liters each day.
Bacterial action in colon
Bacteria can digest small amounts of cellulose. This provides some energy, which
is significant.
As result of bacterial activity are also other substances formed, such as vitamine
K, B12, thiamine, riboflavin and gases that contribute to flatus in the colon
(carbon dioxide, hydrogen gas, methane).
Composition of the feces
They are normally about ¾ water and ¼ solid matter that itself is composed of
about 30% bacteria, 10-20% fat, 10-20% inorganic matter, 2-3% protein and 30%
,undigested roughade from digestive juices (bile pigment and sloughed epithelial
cells). The brown color is caused by stercobilin and urobilin, derivatives of
bilirubin. The odor is caused by products of bacterial action, which vary from
person to person. This depends on the food eaten and on the person’s colonic
bacterial flora. The odoriferous products are: indole, skatole, mercaptans and
hydrogen sulfide.
The principal functions of the colon are:
- Absorption of water and electrolytes from the chime to form solid feces
mostly the proximal half
- Storage of fecal matter until it can be expelled mostly the distal half
Mixing movements: large circular constrictions occur, about 2,5 cm of the circular
muscle contracts. Also the longitudinal muscle contracts. These contractions
cause haustrations: baglike sacs.
The fecal material is dug into and rolled over, all material is gradually exposed to
the mucosal surface or the large intestine, and fluids and dissolved substances
are absorbed until only 80-200 millimeters of feces are expelled each day.
Propulsive movements:
Much of the propulsion in the cecum and ascending colon results from the slow
but persistent haustral contractions, requiring 8-15 hours to move the chime from
the ileocecal valve through the colon. The chime becomes fecal: a semisolid slush
instead of semifluid.
From the cecum to the sigmoid, mass movements can take over the propulsive
role, mostly 15 minutes during first hour after breakfast. This is a modified type
of peristalsis:
- First, a constrictive ring occurs in the transverse colon
- The 20 or more cm distal to the ring lose their haustrations and contract as
a unit
Mass movements after meals is facilitated by gastrolic and duodenocolic reflexes.
The reflexes are transmitted by way of the autonomic nervous system.
Most of the time, the rectum is empty of feces. A weak sphincter exists about 20
cm from the anus at the juncture between the sigmoid colon and the rectum. This
gives resistance to filling of the rectum. When a mass movement forces feces
, into the rectum, the desire for defecation occurs; reflex contraction of the rectum
and relaxation of anal sphincters occurs.
Continuous flowing of feces through the anus is prevented by constriction of:
- An internal anal sphincter: circular smooth muscle that lies immediately
inside the anus
- An external anal sphincter; striated muscle. This is controlled by nerve
fibers in the pudendal nerve, which is part of the somatic nervous system
and therefore is under voluntary, subconscious control. (subconsious: it is
always kept constricted unless conscious signals inhibit the constriction).
2. What happens when you have diarrhea and how can you cure
it?(causes)
Diarrhea results from rapid movement of fecal matter through the large intestine.
Several causes of diarrhea are:
- Enteritis: This means inflammation caused either by a virus or by bacteria
in the intestinal tract.
o Production of toxins
o Damage
In usual infectious diarrhea, the infection is in the large intestine and the distal
end of the ileum. The mucosa (where infection is present), becomes very
irritated and its rate of secretion becomes greatly enhanced. Motility of
intestinal wall increases. The result is that large quantities of fluid are made
available for washing the infectious agent towards the anus, also strong
propulsive movements bring this fluid forward.
o Diarrhea caused by cholera is of special interest, this toxin directly
stimulates excessive secretion of electrolytes and fluid is the distal
ileum and colon. This can go to 10-12 liters per day. Several days
can ensure death. Therapy: replace fluid and electrolytes as rapidly
as they are lost, by giving solutions (oplossingen met electrolyten).
- Psychogenic emotional diarrhea: during periods of nervous tension. This is
caused by excessive stimulation of the parasympathic nervous system,
which excites motility and excess secretion of mucus in the distal colon.
This can cause diarrhea.
- Ulcerative colitis: areas of the walls of the large intestine become inflamed
and ulcerated. Motility of colon is to great, mass movements occur to
often. The secretions of the colon also are enhanced. Repeated diarrheal
bowel movements. The cause is unknown, but there’s a strong hereditary
tendency for susceptibility.
Peristaltic rush (irritation of the intestinal mucosa powerful and rapid
peristalsis) can cause serious diarrhea.
For cure, also ORS or medicines are important.
3. What happens when you have constipation, what causes it and
how can you cure it?
Constipation: slow movement of feces through the large intestine, large amount
of dry, hard feces in the descending colon that accumulates because of over-
absorption of fluid. Any pathology that obstructs movement of intestinal
contents, can cause constipation. A frequent cause is irregular bowel habits (in
going to toilet) that develop through a lifetime of inhibition of normal defecation
reflexes. If one does not allow these natural reflexes to occur, the reflexes
become less strong and the colon becomes atonic.
