Flashcards in Equine Deck (66):
How is the cecum anchored in the abdomen?
The cecal base is attached dorsally to the ventral surface of the right kidney, to the right lobe of the pancreas, and to a part of the abdominal wall caudal to these structures. The cecal base is attached medially to the transverse colon and the root of the mesentery, from which the vascular supply reaches the cecum.
How many bands does the cecum have? Which ones travel all the way to the apex?
4; dorsal and medial bands (the ventral band usually joins the medial band near the apex, and the lateral band may extend to the apex or fade out before reaching the apex)
The ileocecal fold runs from the antimesenteric border of the ileum to the _____ cecal band.
The cecocolic fold (ligament) runs from the ________ cecal band to the _________ free band of the right _______ colon.
lateral; lateral; ventral
From where does the cecum derive its blood supply?
the cecal artery (a branch of the ileocecal artery)
Which cecal bands contain blood vessels?
the medial and lateral cecal bands contain the medial and lateral cecal arteries.
Which artery is the main source of blood supply to the cecal apex?
the medial cecal artery
In regard to cecal motility patterns, describe the directions of movement and the associated functions of each.
Pattern I: begins at the cecal apex and travels toward the base; mixing of cecal ingesta
Pattern II: begins at the caudal cecal base and travels to the apex; mixing of cecal ingesta
Pattern III: begins at the cranial cecal base and travels to the apex; mixing of cecal ingesta
Pattern IV: begins at the cecal apex and is conducted through the cecal base and cecocolic orifice and into the right ventral colon, progressive pattern that moves ingesta into the RVC.
Which drugs have been shown to depress progressive motility patterns, prolonging cecal emptying, and prolong the inhibition of spike bursts in the cecum when used in combination?
Xylazine and butorphanol
What drugs have been shown to increase the rate of cecal emptying?
Neostigmine methylsulfate, bethanechol chloride, and erythromycin lactobionate
How many bands (teniae) does the ventral colon have?
4; two ventral bands that are free, and two dorsal bands that are associated with the mesentery
Which colonic band is associated with vasculature?
the medial dorsal band
How many bands does the pelvic flexure have?
How many bands does the left dorsal colon have?
How many bands does the right dorsal colon have?
T/F: The teniae coli are composed of smooth muscle and collagen in varying proportions; The roles of the teniae coli are to provide mechanical support to the colon, to maintain orientation of the colon within the abdomen, and to allow distention and contraction of the intestinal segments depending on the degree of ongoing fermentation.
True; In the ventral colon, the site of bacterial fermentation, the teniae have a greater proportion of elastin than in the dorsal colon. In the right dorsal colon, the site of transport and regulation of ingesta through the transverse colon, smooth muscle cells are present in greater proportion.
From where is the blood supply to the ascending colon derived?
overall from the cranial mesenteric artery; the colic branch of the ileocecocolic artery supplies the ventral colon to the pelvic flexure, where it joins the right colic artery, another branch of the cranial mesenteric artery
From where is the blood supply to the transverse colon derived?
The middle colic artery, also a branch of the cranial mesenteric artery, provides blood supply to the transverse colon and to the initial part of the small colon
T/F: The principal mechanism for delay in transit is the retropulsive activity initiated in a pacemaker region near the pelvic flexure (approximately 30 cm (12 inches) aboral to the termination of the medial and lateral free teniae of the left ventral colon).
True; The coordinated contractions originating at the pelvic flexure pacemaker promote physical separation of small, well-digested particles, which are propelled aborally, and of coarser particles, which are propelled orally for further digestion.
How is the transverse colon anchored to the abdomen?
It is connected dorsally to the pancreas, to the dorsal aspect of the abdominal cavity, and by a short transverse mesocolon to the root of the mesentery.
T/F: The small colon is attached to the terminal duodenum by the duodenal colic fold
From where is the blood supply of the small colon derived?
The vascular supply to the small colon is derived from the caudal mesenteric artery with anastomoses cranially from the cranial mesenteric artery and caudally from the middle and caudal rectal arteries. The caudal mesenteric artery divides into two major branches, the left colic artery and the cranial rectal artery, with the left colic artery supplying the proximal three fourths of the descending colon and the cranial rectal, the distal one fourth.
T/F: In true hernias, the protrusion occurs through a normal aperture in the abdomen and contains a complete peritoneal sac (inguinal or scrotal hernia). These hernias are sometimes referred to as indirect hernias.
T/F: In false hernias, the protrusion does not arise through a normal aperture in the abdomen. False hernias do not initially contain a complete peritoneal sac and are usually created by trauma to the abdomen or develop after breakdown of a surgical entry (incisional hernias). These are also referred to as direct hernias.
From where is the blood supply to the small intestine derived?
the cranial mesenteric artery supplying the jejunal arteries and the ileocecal artery (supplies the ileum)
T/F: Digestion and absorption of nutrients take place predominantly in the lower half of the small intestine.
False; Digestion and absorption of nutrients take place predominantly in the upper half of the small intestine
Unique to the small intestine in adults are fingerlike projections of the epithelial surface called _____, and each _______ is surrounded by approximately six to nine _________ __ ______________.
villi; villus; crypts of Lieberkühn
What is the predominant cell type of the small intestinal epithelial cells?
Columnar absorptive cells or enterocytes constitute about 90% of the small intestinal epithelial cells, and the remainder are mucous (goblet) cells, enteroendocrine cells, Paneth cells, and undifferentiated columnar cells.
T/F: After at least two divisions within the crypt, the columnar cells migrate onto the villus as mature absorptive cells, and they are finally extruded at the villous tip, usually with a turnover time of 2 to 3 days.
On what part of the villi does the majority of digestion and nutrient active transport occur?
Cells in the upper third of the villi are capable of surface digestion of nutrients and active transport of digestion products
T/F: Dietary carbohydrates, fats, and proteins are broken down by pancreatic enzymes in the small intestine, and their breakdown products are hydrolyzed further by brush border enzymes.
What triggers the release of secretin from S-cells?
Hydrogen ions in the duodenum
What triggers the release of cholecystokinin (CCK) from I-cells?
Protein and fat in the duodenum
What is the function of CCK?
Protein and fat in the duodenum stimulate the release of cholecystokinin (CCK) from I-cells, and CCK causes the pancreas to secrete enzymes for the digestion of carbohydrates (amylase), fat (lipase), and protein (trypsin, chymotrypsin, carboxypeptidase, and elastase), as well as cofactors (colipase) that aid in enzymatic digestion.
T/F: Trypsinogen, the precursor form (or zymogen) of trypsin, must reach the large intestine to be activated by the brush border enzyme enterokinase.
False; Trypsinogen, the precursor form (or zymogen) of trypsin, must reach the small intestine to be activated by the brush border enzyme enterokinase. Other enzymes that are secreted as zymogens can be activated only by trypsin
In the liver, cholic acid and chenodeoxycholic acid combine with glycine and taurine to form __________ _____ ______.
conjugated bile salts
What is enterohepatic circulation of bile?
A process by which approximately 94% of bile salts are reabsorbed by the small intestinal mucosa, pass to the liver, and are then resecreted.
Bile absorption in the jejunum is (active/passive)?
Bile absorption in the ileum is (active/passive)?
active transport by a Na+ dependent process
What part of the small intestine absorbs the most water?
the distal third of the small intestine, however the bulk of water is absorbed by the large intestine.
At the level of the cervical vertebrae, what are the layers of the esophagus from outer to inner?
fibrous layer (tunica adventitia), muscular layers (tunicae muscularis), a submucosal layer (tela submucosa), and a mucous membrane (tunica mucosa)
T/F: The muscular layers are striated from the pharynx to the base of the heart, where they gradually blend into smooth muscle.
T/F: The lumen of the esophagus gets smaller as it travels orally.
True; the muscular layers increase in thickness, whereas the lumen diminishes
T/F: Except at the lower esophageal sphincter, the two muscular layers are arranged spirally and elliptically.
False; Except at the upper esophageal sphincter, the two muscular layers are arranged spirally and elliptically
T/F: The elastic inner layer, composed of mucosa and submucosa, is freely movable within the relatively inelastic outer muscular layer and adventitia.
What is the layer of strength in the esophagus?
The mucosa; it provides the greatest tensile strength on closure of an esophageal incision.
The mucosa of the esophagus is covered with __________ ___________ __________ and lies in ___________ folds that obliterate the lumen except during __________.
stratified squamous epithelium; longitudinal; deglutition.
T/F: The esophageal mucosa is heavily colonized by facultative and obligate anaerobic bacteria.
From where is the blood supply to the equine esophagus derived?
The arterial supply to the cervical part of the esophagus originates from the carotid arteries. The thoracic and relatively short abdominal esophagus is supplied by the bronchoesophageal and gastric arteries.
Innervation of the esophagus is derived from the ___ and ___ cranial nerves and the _________ trunk, as well as mesenteric ganglion cells within the _______ layers.
9th and 10th; sympathetic; muscle
T/F: Food boluses move more quickly through the distal third of the esophagus.
False; the propagation speed of the equine esophagus is about 9.4 cm/sec in the proximal two thirds but only 4.6 cm/sec in the distal one third.
With obstruction of the distal esophagus, odynophagia and retching may occur 10 to 12 seconds after swallowing. With proximal esophageal obstruction, the signs may be evident immediately.
Flow where is the blood supply to the equine stomach derived?
the celiac artery; Venous drainage from the stomach is via gastric veins to the portal vein.
The cardia is attached to the diaphragm by the __________ ligament. This ligament is a continuation of the __________ ligament and the _________ ligament on the left side of the abdomen. The ______ _________ attaches along the greater curvature of the stomach, and it blends into the gastrophrenic ligament.
gastrophrenic; phrenicosplenic; gastrosplenic; greater omentum
The greater omentum forms the ________ _____. The entrance to this bursa is the epiploic foramen, which is located between the _________ ________ of the liver and the ______ lobe of the pancreas.
omental bursa; caudate process; right
The epiploic foramen is bordered dorsally by the ____________ and ventrally by the _____________.
caudal vena cava; portal vein
The _______ ______, which connects the stomach and duodenum to the liver, consists of the ________ and _________ ligaments.
lesser omentum; hepatogastric and hepatoduodenal
Which cells in the glandular mucosa of the stomach secrete HCl?
Which cells in the glandular mucosa of the stomach secrete pepsinogen? what is the role of pepsinogen?
zymogen cells (aka chief or peptic cells); begin break down of proteins
Which cells in the glandular mucosa of the stomach secrete histamine?
enterochromaffin-like (ECL) cells secrete histamine in response to various stimuli, which in turn amplifies HCl secretion by the parietal cells.
Which cells in the pyloric mucosa of the stomach secrete gastrin? what is the role of gastrin?
G-cells; enhance gastric acid secretion
Which cells in the pyloric mucosa of the stomach secrete somatostatin? what is the role of somatostatin? what other part of the equine stomach has been shown to have cells that secrete somatostatin?
D-cells; reduce gastric acid secretion; cardiac epithelium
What is the predominant cell type in the nonglandular portion of the equine stomach?
nonglandular stratified squamous epithelium
What are the layers of the stratified squamous epithelium?
. The stratified squamous epithelium consists of four layers:
the outer stratum corneum,
the stratum transitionale,
the stratum spinosum, and
the basal stratum germinativum.
Which layers of the stratified squamous epithelium contribute to the barrier function?
Interepithelial tight junctions in the stratum corneum and muco-substances secreted by the stratum spinosum are mainly responsible for barrier function.
How is the glandular mucosa of the stomach protected from acid injury?
high transepithelial electrical resistance helps to prevent back diffusion of H+ ions; gastric mucosa secretes mucus and bicarbonate, forming an H3CO- containing gel that titrates acid before it reaches the lumen; acid (H+) that does diffuse back to into the gastric mucosa is expelled via Na+/H+ exchangers, once the cell reaches a critical pH.