Ch.37 Large Colon Flashcards
Length of large ecolon
3 - 3.7meters
Average diameter of Large colon
20 - 25cm
Capacity of large colon
Double that of cecum
50 - 60L
Widest point of large colon
Right dorsal - ampulla coli 50cm
Describe the mesocolon
Two layers of peritoneum - extensions of the parietal and viscera peritoneum
10 - 12cm wide between RD and RV
Wider between LD and LV 15cm at pelvic flexure
Outer mesothelium produces a serous peritoneal fluid
Sacculations and bands of ventral colon
Plicae semilunaris coli (constrictions)
Haustra coli (sacculation)
4 tenial bands - (mostly elastic)
free lateral, free medial
lateral mesenteric (covered by mesocolon)
medial mesenteric (covered by lymph nodes and blood vessels)
Sacculations and bands of dorsal colon and pelvic flexure
No haustra
Dorsal - right - 3 tenia (mostly muscular)
PF - 1 Tenai - mesenteric - continues
ventral on left dorsal colon
Lateral free band of the right ventral colon attaches to what
Cecum - lateral cecal band
via
cecocolic lig
Where is the transverse colon attached
By the mesocolon to the:
- Ventral surface of the pancreas
dorsally - Cecal base laterally
- Diaphragm and liver indirectly
Blood supply to ventral colon
Colic branch of ileocolic a. (a branch of the cranial mesenteric a.)
On medial aspect
arteries branch from 2 colic vessels every 2cm and anastomose with adjacent vessels creating a rete before continuing to the submucosa where they form a plexus
Blood supply to dorsal colon
Right colic a. arises from short common trunk of right and middle colic aa. (branch of cranial mesenteric)
On medial aspect
arteries branch from 2 colic vessels every 2cm and anastomose with adjacent vessels creating a rete before continuing to the submucosa where they form a plexus
Venous drainage of large colon
Right colic v -> caudal mesenteric v ->portal v
Left colic v -> cranial mesenteric v ->portal v
Muscle layers
Inner circular
Outer longitudinal
Mucosa - epithelial type etc
Columnar epithelium with crypts or glands
Many goblet cells
No villi
Lamina propria is composed of
Loose connective tissue
Fibroblasts
Lymphocytes
Plasma cells
Macrophages
Eosinophilic leukocytes
Mast cells
Where is the Auerbach plexus (Myenteric plexus)
Between the circular and longitudinal muscle layers
Motor innervation to both layers
Primary function of the large colon
Hydrolysis of structural carbohydrates to soluble sugars - fermentation - production of volatile short chain fatty acids by colonic microbes
Acetate is used as the energy source for what
Peripheral tissues
and a precursor for lipogenesis
Where is propionate primarily used
Liver as a precursor for gluconeogenesis
What is the major energy source for colonic epithelial cells
Butyrate
How long does cellular digestion and fermentation take
48 - 72 hours
Capacity of RV colon and retention time
29 - 32L
3 hours
Main site of fibre digestion
Right ventral colon
Capacity and retention time of left dorsal colon
6 - 18L
1 hour
Capacity and retention time of right dorsal colon
30 -36L
4 hours
Why is the large colon a primary site for colic
Rapid passage of soluble carbohydrates
High lactic acid production
Death of pH sensitive mircobes
Dysbacteriosis
Predominant bacteria in the colon
Clostridia
Lachnospraceae
Ruminococcaceae Bothe degrade plant material with production of butyrate
Where is the Meissner plexus
Submucosa
Supply muscular mucosae
Provide secretomotor innervation to the mucosa
Which part of the colon is thought to have a pacemaker function?
a. Pelvic flexure
b. Right dorsal colon
c. Right ventral colon
d. Left dorsal colon
a. Pelvic flexure
long partially digested fibers are retained in the ventral colon for ongoing digestion by retropulsive peristaltic movement, and liquid and fine particles are moved aborally by propulsive motility
Which of the following statements is correct regarding the large colon
a. interstitial cells of Cajal (iCC) are pacemakers and mediators of neurotransmission in the gastrointestinal tract and responsible for increasing secretions from goblet cells
b. interstitial cells of Cajal (iCC) are pacemakers and mediators of neurotransmission in the gastrointestinal tract and generate a rhythmic pacemaker current that produces fast waves in intestinal smooth muscle
c. interstitial cells of Cajal (iCC) are pacemakers and mediators of neurotransmission in the gastrointestinal tract and generate a rhythmic pacemaker current that produces slow waves in intestinal smooth muscle
d. interstitial cells of Cajal (iCC) are pacemakers and mediators of neurotransmission in the gastrointestinal tract and responsible for decreasing secretions from goblet cells
c. interstitial cells of Cajal (iCC) are pacemakers and mediators of neurotransmission in the gastrointestinal tract and generate a rhythmic pacemaker current that produces slow waves in intestinal smooth muscle
Which of the following statements is correct regarding the large colon
a. Cholinomimetics cause a decrease in intestinal motility
b. Complete severance of the autonomic nervous system has little effect on intestinal motility
c. Complete severance of the autonomic nervous system has a profound effect on intestinal motility
d.α-adrenergic antagonists cause a decrease in intestinal motility
b. Complete severance of the autonomic nervous system has little effect on intestinal motility
Cholinomimetics promote intestinal motility
α-adrenergic agonists impair motility and
α-adrenergic antagonists enhance intestinal motility
Which of the following statements is correct regarding the large colon
a. ViP-reactive neurons can cause smooth muscle relaxation
b. There appears to be a decrease in neuronal ganglia density in the left dorsal colon
c. Parasympathetic hypoactivity causes an increase in motility and intestinal secretion.
d. Enteric smooth muscle generates fast waves (spontaneous oscillations of the membrane potential), which generate an action potential
a. ViP-reactive neurons can cause smooth muscle relaxation
There appears to be an increase in neuronal ganglia density in the left dorsal colon
Parasympathetic hypoactivity causes a decrease in motility and intestinal secretion
Enteric smooth muscle generates slow waves (spontaneous oscillations of the membrane potential), which are inadequate to generate an action potential
Which of the following statements is correct regarding the large colon
a. input from the enteric (intrinsic) and autonomic (extrinsic) nervous system, namely sympathetic (adrenergic) and parasympathetic (cholinergic, vagus), is required for sufficient depolarization to reach the threshold potential and generate an action potential
b. input from the enteric (extrinsic) and autonomic (intrinsic) nervous system, namely sympathetic (adrenergic) and parasympathetic (cholinergic, vagus), is required for sufficient depolarization to reach the threshold potential and generate an action potential
c. input from the enteric (intrinsic) and autonomic (extrinsic) nervous system, namely sympathetic (adrenergic) and parasympathetic (cholinergic, vagus), are insufficient to reach the threshold potential and cannot generate an action potential
d. input from the enteric (extrinsic) and autonomic (intrinsic) nervous system, namely sympathetic (adrenergic) and parasympathetic (cholinergic, vagus), are insufficient to reach the threshold potential and cannot generate an action potential
a. input from the enteric (intrinsic) and autonomic (extrinsic) nervous system, namely sympathetic (adrenergic) and parasympathetic (cholinergic, vagus), is required for sufficient depolarization to reach the threshold potential and generate an action potential
Which of the following statements is correct regarding the large colon
a. The enteric nervous system is unable to utilize neuropeptides as neurotransmitters
b. The autonomic nervous system uses neuropeptides including vasoactive intestinal peptide [ViP], methionine-enkephalin, calcitonin gene-related peptide, substance P, and other neurokinins and nitric oxide as neurotransmitters
c. The autonomic nervous system consists of ganglia in the myenteric (Auerbach) and submucosal (meissner) plexus
d. The enteric nervous system consists of ganglia in the myenteric (Auerbach) and submucosal (meissner) plexus
d. The enteric nervous system consists of ganglia in the myenteric (Auerbach) and submucosal (meissner) plexus
The enteric nervous system consists of ganglia in the myenteric (Auerbach) and submucosal (meissner) plexus and uses neuropeptides (including vasoactive intestinal peptide [ViP], methionine-enkephalin, calcitonin gene-related peptide, substance P, and other neurokinins) and nitric oxide as neurotransmitters.
Which of the following statements is correct regarding the large colon
a. More Proteobacteria are found in the colon compared to the duodenum and ileum.
b. Clostridia is the predominant bacterial class in the colon
c. Lachnospiraceae and ruminococcaceae (order Enterococcaceae) are important components of the intestinal microbiota and degrade plant material with the production of butyrate
d. Firmicutes are the predominant phylum throughout the gastrointestinal tract with the highest proportion in the colon
b. Clostridia is the predominant bacterial class in the colon
Fewer Proteobacteria are found in the colon compared to the duodenum and ileum
lachnospiraceae and ruminococcaceae (order Clostridiales) are important components of the intestinal microbiota and degrade plant material with the production of butyrate.
Firmicutes are the predominant phylum throughout the gastrointestinal tract with the highest proportion in the stomach and duodenum
Which of the following statements is correct regarding the large colon
a. The left dorsal colon has a relatively small capacity of 6 to 18 L and a retention time of at least 4 hours
b. The right dorsal colon has a large capacity of 30 to 36 L and a retention time of at least 1 hour
c. The right dorsal colon has a low capacity to digest fiber
d. The right ventral colon has a capacity of 6 to 8 L and a retention time of at least 3 hours
c. The right dorsal colon has a low capacity to digest fiber
The left dorsal colon has a relatively small capacity of 6 to 18 l and a short retention time of at least 1 hour
The right dorsal colon has a large capacity of 30 to 36 l and a long retention time of at least 4 hours
The right ventral colon has a capacity of 29 to 32 L and a retention time of at least 3 hours
Which of the following statements is correct regarding the large colon
a. Cellular digestion and terminal fermentation requires from 48 to 72 hours
b. The right dorsal colon has a capacity of 29 to 32 l and a retention time of at least 3 hours and appears to be the main site of fiber digestion
c. Propionate is the major respiratory fuel for colonic epithelial cells, improves mucosal barrier function by down regulating proinflammatory mediator gene expression, and maintains colonic epithelium homeostasis
d. Acetate is used as an energy source for peripheral tissues and as a precursor for gluconeogenesis
a. Cellular digestion and terminal fermentation requires from 48 to 72 hours
The right ventral colon has a capacity of 29 to 32 l and a retention time of at least 3 hours and appears to be the main site of fiber digestion
Butyrate is the major respiratory fuel for colonic epithelial cells, improves mucosal barrier function by down regulating proinflammatory mediator gene expression, and maintains colonic epithelium homeostasis
Acetate is used as an energy source for peripheral tissues and as a precursor for lipogenesis
Which of the following statements is correct regarding the large colon
a. The primary function of the equine large colon is water absorption, absorbing 10% of body weight daily
b. The nerves of the myenteric plexus are derived from the plexuses of parasympathetic nerves around the cranial mesenteric artery
c. Branches from the Meissner plexus perforate the circular muscle fibers to form the Myenteric (Auerbach) plexus.
d. The myenteric plexus provides parasympathetic input only
b. The nerves of the myenteric plexus are derived from the plexuses of parasympathetic nerves around the cranial mesenteric artery
The primary function of the equine large colon is hydrolysis of structural carbohydrates (dietary plant fiber) to soluble sugars that undergo anaerobic fermentation, leading to the production of volatile short-chain fatty acids by colonic microbes
It also absorbs large vols of water; 20-30% of body weight daily
Branches from the myenteric plexus perforate the circular muscle fibers to form the submucosal plexus
The myenteric plexus provides both parasympathetic and sympathetic input
Which of the following statements is correct regarding the large colon
a. The outer circular muscle layer is consistent throughout the large colon; however, the inner longitudinal smooth muscle layer is thin except where it forms tenial bands which also contain elastic fibers.
b. The inner circular muscle layer is consistent throughout the large colon; however, the outer longitudinal smooth muscle layer is thin except where it forms tenial bands which also contain elastic fibers.
c. The inner smooth muscle layer is consistent throughout the large colon; however, the outer circular muscle layer is thin except where it forms tenial bands which also contain elastic fibers.
d. The outer smooth muscle layer is consistent throughout the large colon; however, the inner circular muscle layer is thin except where it forms tenial bands which also contain elastic fibers.
b. The inner circular muscle layer is consistent throughout the large colon; however, the outer longitudinal smooth muscle layer is thin except where it forms tenial bands which also contain elastic fibers.
Which of the following statements is correct regarding the large colon
a. Small parasympathetic ganglia are scattered throughout the submucosal plexus (meissner plexus) where preganglionic parasympathetic neurons synapse with postganglionic nerve fibers that supply the muscularis mucosae and provide secretory innervation to the mucosa
b. The submucosa is composed of loose connective tissue and variable numbers of fibroblasts, lymphocytes, plasma cells, macrophages, eosinophilic leukocytes, and mast cells
c. The lamina propria of the mucosa into which the crypts invaginate is composed of dense connective tissue and contains blood vessels, lymphatic vessels, and nerves
d. The mucosa consists of columnar epithelium with crypts or glands. The crypts are straight with branches or coils. There are no villi. There are a large number of goblet cells interposed between the principle epithelial cells particularly within the crypts
d. The mucosa consists of columnar epithelium with crypts or glands. The crypts are straight with branches or coils. There are no villi. There are a large number of goblet cells interposed between the principle epithelial cells particularly within the crypts
Small parasympathetic ganglia are scattered throughout the submucosal plexus (meissner plexus) where preganglionic parasympathetic neurons synapse with postganglionic nerve fibers that supply the muscularis mucosae and provide motor and secretory innervation to the mucosa.
The submucosa is composed of dense connective tissue and contains blood vessels, lymphatic vessels, and nerves
The lamina propria of the mucosa into which the crypts invaginate is composed of loose connective tissue and variable numbers of fibroblasts, lymphocytes, plasma cells, macrophages, eosinophilic leukocytes, and mast cells
Which of the following statements is correct regarding the large colon
a. The right colic vein drains into the caudal mesenteric vein
b. The left colic vein drains into the caudal mesenteric vein
c. The right colic vein drains into the cranial mesenteric vein
d. The right and left colic veins drain directly into the portal vein
a. The right colic vein drains into the caudal mesenteric vein
The right colic vein drains into the caudal mesenteric vein and the left colic vein drains into the cranial mesenteric vein both of which drain into the portal veins.
Which of the following statements is correct regarding the large colon
a. The lymphatics drain to the colic lymph nodes in the mesocolon and from there directly into the cisterna chyli
b. The blood vessels are on the lateral aspect of the dorsal and ventral colons
c. The ventral colon is supplied by the colic branch of the ileocolic artery (a branch of the cranial mesenteric artery)
d. The dorsal colon is by supplied by the colic branch of the ileocolic artery (a branch of the cranial mesenteric artery)
c. The ventral colon is supplied by the colic branch of the ileocolic artery (a branch of the cranial mesenteric artery)
The lymphatics drain to the colic lymph nodes in the mesocolon, then into the cranial mesenteric lymph nodes, and then the cisterna chyli.
The blood vessels are on the medial aspect of the dorsal and ventral colons.
The dorsal colon is supplied by the right colic artery, which arises from a short common trunk of the right and middle colic arteries (also a branch of the cranial mesenteric artery
Which of the following statements is correct regarding the large colon
a. The dorsal colon is supplied by the right colic artery, which arises from a short common trunk of the right and middle colic arteries a branch of the cranial mesenteric artery
b. The dorsal colon is supplied by the right colic artery, which arises from a short common trunk of the right and middle colic arteries a branch of the caudal mesenteric artery
c. The dorsal colon is supplied by the colic branch of the ileocolic artery (a branch of the cranial mesenteric artery)
d. The dorsal colon is supplied by the left colic artery, which arises from a short common trunk of the right and middle colic arteries a branch of the caudal mesenteric artery
a. The dorsal colon is supplied by the right colic artery, which arises from a short common trunk of the right and middle colic arteries a branch of the cranial mesenteric artery
The ventral colon is supplied by the colic branch of the ileocolic artery (a branch of the cranial mesenteric artery)
The dorsal colon is supplied by the right colic artery, which arises from a short common trunk of the right and middle colic arteries also a branch of the cranial mesenteric artery
Which of the following statements is correct regarding the large colon
a. The ventral colon is supplied by the colic branch of the right colic artery a branch of the cranial mesenteric artery
b. The ventral colon is supplied by the right colic artery, which arises from a short common trunk of the right and middle colic arteries also a branch of the cranial mesenteric artery
c. The ventral colon is supplied by the colic branch of the ileocolic colic artery a branch of the cranial mesenteric artery
d. The ventral colon is supplied by the right colic artery, which arises from a short common trunk of the right and middle colic arteries also a branch of the caudal mesenteric artery
c. The ventral colon is supplied by the colic branch of the ileocolic colic artery a branch of the cranial mesenteric artery
Which of the following statements is correct regarding the large colon
a. The pelvic flexure has one mesenteric tenia which continues along the ventral surface of the left and right dorsal colon, splitting into two bands, ventral and dorsal, as it passes the diaphragmatic flexure.
b. The tenial bands are composed of smooth muscle and connective tissue rich in elastin and collagen, with the dorsal colon bands being primarily elastic and the ventral colon bands being primarily muscular.
c. The right ventral colon is attached to the cecum by the ileocolic ligament which attaches the lateral free (nonmesenteric) band of the right ventral colon to the lateral cecal band.
d. The transverse colon is attached by the mesocolon to the ventral surface of the pancreas dorsally, the cecal base laterally, and indirectly to the diaphragm and liver.
d. The transverse colon is attached by the mesocolon to the ventral surface of the pancreas dorsally, the cecal base laterally, and indirectly to the diaphragm and liver.
The pelvic flexure has one mesenteric tenia which continues along the ventral surface of the left dorsal colon. The right dorsal has three tenial bands.
The tenial bands are composed of smooth muscle and connective tissue rich in elastin and collagen, with the ventral colon bands being primarily elastic and the dorsal colon bands being primarily muscular.
The right ventral colon is attached to the cecum by the cecocolic ligament which attaches the lateral free (nonmesenteric) band of the right ventral colon to the lateral cecal band.
