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An in-depth exploration of the colon's functions, absorption and secretion processes, types of motility, and innervation. It covers the roles of different colon regions, such as the ascending, transverse, descending, and sigmoid colon, as well as the rectosigmoid region, anal canal, and pelvic floor musculature. The document also discusses the neural control of colonic motility and the defecation reflex.
What you will learn
Typology: Lecture notes
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Contents
COLON FUNCTIONS:
4
3
Secretions of the Large Intestine:
Lieberkühn.
adherent medium for holding fecal matter together).
1 from the spinal cord
can cause:
o marked increase in mucus secretion.
o This occurs along with increase in peristaltic motility
of the colon.
mucus can be secreted into the large intestine that the
person has a bowel movement of ropy
2 mucus as often as
every 30 minutes; this mucus often contains little or no
fecal material. 1: considered a part of parasympathetic in large intestine.
2: resembling a rope in being long, strong, and fibrous
3: anatomical division.
ILEOCECAL VALVE
It prevents backflow of contents
from colon into small intestine.
It remains closed and open only
when an intestinal peristaltic wave
reaches it.
Gastrin, CCK, B
adrenergic
Distension of the
cecum, Secretin,
Ach, alpha
adrenergic
CONT.
7
and dehydration of feces.
removal of water and electrolytes and the storage of
feces.
st
transverse and sigmoid colon.ātransportationā
about 24 hours after the label is instilled in the cecum
that is involved in defecation reflex.
maintains fecal continence (the ability to voluntarily control urinary and fecal discharge).
1 .
maintain continence.
shaped sling (physiological valve)*
1: 25% of 500ml in sigmoid can trigger defecation.
ABSORPTION AND SECRETION:
(physiological division)
10
1 - Mixing movements
(Haustrations)
ļ§Ring-like contractions (about 2.5 cm) of
the circular muscle divide the colon into
pockets
3 called haustra.
ļ§The contracting segment and receiving
segment on either side remain in their
respective state for longer periods.
ļ§In addition, there is uniform repetition of
the haustra along the colon.
ļ§Net forward propulsion occurs when
sequential
1 migration of haustra occurs
along the length of the bowel.
ļ§The motor events in the transverse and
descending colon.
ļ§May be triggered by the increased delivery
of ileal chyme into ascending colon
following a meal ( gastrocolic reflex
2 ).
ļ§Irritants, e.g., castor oil, threatening
agents such as parasites and enterotoxins
can initiate mass movement.
ļ§ Start at the middle of transverse colon
and is preceded by relaxation of the
circular muscle and the downstream
disappearance of haustral contractions.
2 - Propulsive movements
( Mass Movements )
TYPES OF MOVEMENTS:
At: Ascending + 1
st part of transverse
At: Descending + rest part of transverse
3 : pocket haustra means two fingers contraction in between them space which called pocket.
CONT.
11
3 - Antiperistalsis
RECTUM & DEF. REFLEX:
13
The Rectum
1
Distension of the rectum.
A. Increased local peristalsis.
B. Relaxation of internal anal sphincter and contraction of
external anal sphincter.
A. Short reflex: Stimulation of myenteric plexus in
sigmoid colon and rectum.
B. Long reflex: stimulation of parasympathetic
2 motor
neurons in sacral spinal cord.
C. stimulation of somatic motor neurons.
1
2
3
4
1 : external sphincter is important in voluntary continence specially at high volume in sigmoid.
2: for increasing peristaltic movement.
ADDITIONAL SLIDE DEFECATION REFELX :
Summary
Summary
transverse ,descending , sigmoid , rectum and finally anus.
secretion
fermentation of CHO are absorbed.
colon.
secretin.
19
MCQs
1 - which one of the following is secreted in colon:
A. Sodium.
B. Water.
C. Bicarbonate.
D. Chlor.
2 - Neurotransmitter that stimulate the motility of colon:
D. Substance P.
3 - Iliocecal valve can contracted by:
B. Gastrin.
C. Secretin.
D. B-Adrenergic.
4 - what is can cause fecal incontinence:
A. Diarrheal Condition.
B. Obesity.
C. Genetic.
D. Powerful of EAS.
5 - In Defecation Reflex, The Short Reflex Stimulate:
A. Myenteric Plexus.
B. Submucosal Plexus.
C. Vagus.
D. Pelvic Plexus.
6 - Antiperistalsis Movement start at:
A. Between Transverse and descending colons.
B. Between Caecum and ascending colons.
C. Between Ascending and transverse colons.
D. Between Descending and sigmoid Colons.
7 - the muscle that is U-Shaped:
C. Puborectalis.
D. Psoas Major.
8 - Ring-like contractions (about 2.5 cm) of the circular
muscle divide the colon into pockets:
A. Propulsive Movement.
B. Mixing contraction (Haustration).
C. Antiperistalsis Movement.
D. Rush Movement.
SAQs
Ans:
1 - Mixing (Haustration).
2 - Propulsive movement.
3 - Antiperistalsis.
Ans: Water, Sodium, Chlor and Bile salt.
Ans:
1 - Puborectalis
2 - Internal Anal Sphincter
3 - External Anal Sphincter
Ans: Vitamin K and Thiamine (B1).