Ch. 87-98 Digestive Flashcards
1
Q
What is the oral vestibule?
A
the real and potential space lateral to the teeth and inside the cheeks
the lateral boundaries are the lips and cheeks
2
Q
What provides motor innervation to the lips and cheeks?
A
facial nerve VII
3
Q
What provides sensory innervation to the outer and inner surfaces of the lips and cheeks?
A
trigeminal nerve V
4
Q
What is the vascular supply of the lip and cheek?
A
the facial artery supplies the lower lip and cheek
the infraorbital artery supplies the upper lip and cheek
5
Q
What muscles comprise the root of the tongue?
A
styloglossus (which has three subdivisions)
hyoglossus
genioglossus
They are all innervated by the hypoglossal nerve
6
Q
what is the origin and insertion of the hyoglossus muscle?
A
originates from the basihyoid and inserts on the caudal two thirds of the tongue
7
Q
what is the origin and insertion of the genioglossus?
A
originates from the medial aspect of each mandible caudal to the symphysis and separates into three bundles. The vertical bundle inserts on the rostral portion of the ventral tongue, the oblique bundle inserts on the ventral region of the caudal aspect of the tongue, and the straight bundle inserts on the caudal third of the tongue, basihyoid bone and ceratohyoid
8
Q
Describe the intrinsic muscles of the tongue
A
They course into one another and have no real borders. They are organized by their fibers which run longitudinally, deep longitudinal, transverse, and perpendicular. They are also controlled by the hypoglossal nerve
9
Q
What is the lyssa?
A
it is in the body of the tongue and may be a stretch receptor but nobody really knows what it is. Made of muscle, fat, and sometimes cartilage in a sheath of connective tissue
10
Q
What are the gustatory papillae of the tongue?
A
fungiform, vallate, foliate – all have tastebuds
11
Q
What are the non gustatory papillae of the tongue?
A
filiform and conical
conical papillae will facilitate grooming, especially in the cat
12
Q
What nerves are involved in taste, pain, heat, and sensation of the tongue?
A
branches of the trigeminal, facial, and glossopharyngeal
13
Q
What is the blood supply to the tongue?
A
Lingual artery (a branch of the external carotid) the right and left lingual arteries anastomose throughout the parenchyma of the tongue and therefore if you disrupt one, it will not disrupt blood supply to the tongue
14
Q
What are the boundaries of the oropharynx?
A
bound dorsally by the soft palate and ventrally by the root of the tongue
it is the space between the oral cavity proper and the laryngo and nasopharynx
15
Q
What are the muscles of the soft palate?
A
paired palatine, tensor and levator veli palatini, pterygopharygeal, and palatopharyngeal muscles covered in stratified squamous epithelium
The palatopharyngeal muscles extend laterally and make up the palatopharyngeal arches
16
Q
How does the soft palate help protect the nasopharynx during deglutition?
A
The palatopharyngeal muscles of the soft palate extend laterally and form the palatopharyngeal arches. Those arches make up the intrapharyngeal ostium and act as a sphincter. Additionally, the tensor and levator veli palatini become taut and then this results in the caudal free edge of the soft palate pressing on the pharyngeal wall
17
Q
what innervates the muscles of the soft palate?
A
cranial nerves glossopharyngeal (IX) and vagus (V)
18
Q
What is the blood supply of the soft palate?
A
maxillary artery which courses through the minor palatine foramine and makes the minor palatine artery
19
Q
What is the blood supply of the palatine tonsil?
A
tonsilar artery which comes off of the lingual artery
20
Q
What secret tonsils do cats and dogs have in addition to the palatine tonsil
A
they also have a lingual tonsil on the base of the tongue and a pharyngeal tonsil on the roof of the nasopharynx
cats also have paired paraepiglottic tonsils
21
Q
What are the phases of deglutition (swallowing)?
A
oropharyngeal
esophageal
gastroesophageal
22
Q
what are the subphases of the oropharyngeal phase of deglutition?
A
- Oral (formation of a food bolus by compressing food between tongue and palate, then the food is propelled to the pharynx. this is all voluntary)
- Pharyngeal (reflex - the tongue and pharyngeal constrictor muscles transport the food through the pharynx in a peristaltic like manner, the epiglottis covers the glottis and the soft palate presses against the pharyngeal wall to block the nasopharynx)
- Pharyngoesophageal (closure of the sphincter and relaxation of the pharyngeal constrictor muscles)
23
Q
What nerves are involved in the oral portion of the oropharyngeal phase of swallowing?
A
this is voluntary
Trigeminal (V), facial (VII), and hypoglossal (XII)
24
Q
What nerves are involved in the pharyngeal portion of the oropharyngeal phase of swallowing?
A
this is a reflex and therefore involuntary. It is controlled by nerves IX (glossopharyngeal) and X (vagus)
Nerves IX and X are considered in control of the “swallowing center”
25
What nerves are involved in the pharyngoesophageal portion of the oropharyngeal phase of swallowing?
this is a reflex and therefore involuntary. It is controlled by nerves IX (glossopharyngeal) and X (vagus)
Nerves IX and X are considered in control of the "swallowing center"
26
What are the four major salivary glands in dogs and cats?
parotid
mandibular
sublingual
zygomatic
27
What are the anatomical boundaries of the parotid salivary gland?
Superficial to the vertical ear canal
bordered rostrally by the masseter muscle and the TMJ
caudally by the sternomastoideus and cleidocervicalis muscles
ventrally by the mandibular salivary gland
superficially by the parotidauricularis and platysma muscles
its capsule is intimate with the facial nerve, maxillary/temporal arteries, internal maxillary vein
28
describe the path of the parotid duct
it is formed by two or three converging ductules on the ventrorostral border of the gland and travels over the lateral aspect and ventral third of the masseter muscle then opens into the oral cavity through a small papilla at the level of the upper fourth premolar
an accessory parotid gland is also commonly found dorsal to the duct
29
What is the blood supply of the parotid gland?
parotid artery, which is a branch of the external carotid
it can be identified on the medial aspect of the parotid gland in the region ventral to the external ear canal
venous return is via the superficial temporal and great auricular veins
30
What ducts drain the zygomatic salivary gland?
one major and up to four minor ducts
the major opens into the oral cavity at the caudolateral aspect of the last upper molar - usually the papilla is about 1 cm caudal to the parotid salivary papilla
31
What is the blood supply of the zygomatic salivary gland
branch of the infraorbital artery and drained by the deep facial
32
What make up the boundaries of the mandibular salivary gland
- lies on the medial aspect of the linguofacial and maxillary vein junction
- the mandibular lymph nodes lie on the ventral surface and the medial retropharyngeal lymph node and larynx on the medial surface
- cranially bordered by the primary portion of the sublingual salivary gland - they share the same capsule
33
what is the course of the mandibular salivary duct?
exits the gland on the medial surface and continues rostrally medial to the sublingual salivary gland and horizontal ramus of the mandible
under the oral mucosa, travels between the styloglossus and myelohyoideus msucles until it exits into the oral cavity at the sublingual caruncle lateral to the lingual frenulum
34
what is the blood supply to the mandibular salivary gland?
glandular branch of the facial artery and drains into a branch of the lingual vein
35
Where does the sublingual salivary gland empty?
caudal to the lingual nerve, it is monostomatic and empties into the sublingual duct
rostral to the lingual nerve is polystomatic tissue that empties into the oral cavity
*the major sublingual salivary duct and the mandibular duct course together and exit at the sublingual caruncle
36
What is the blood supply to the sublingual salivary gland?
like the mandibular, the glandular branch of the facial for the monostomatic but it also gets a sublingual branch of the lingual artery for the polystomatic
37
What are the minor salivary glands?
buccal, labial, lingual, tonsillar, palatine, molar
| molar is well developed in cats
38
What is the microscopic pathway of saliva?
The acinus produces saliva that travels to intercalated ducts --> from intercalated ducts, make intralobular ducts --> lobular ducts --> lobar ducts --> major excretory ducts
39
Salivary glands will contain serous and mucous producing cells. Which glands produce more of one than the other?
parotid and mandibular usually more serous
| sublingual and zygomatic usual more mucus
40
What phases does saliva encounter prior to excretion?
Phase 1: acinar cells absorb Na+ which helps make sodium rich saliva, then flows into the collecting ducts
Phase 2: in the intralobular duct epithelium by the columnar epithelial cells, there is active reabsorption of Na+ and secretion of HCO3- and K+
The end result is saliva that is rich in HCO3- and K
41
What is the innervation to the salivary glands?
- The autonomic nervous system provides the majority of nervous control of the salivary glands
- stimulation of the parasympathetic nervous system increases production of saliva by vasodilation of the blood supply and by stimulation of cGMP (cyclic guanosine monophosphate) which directly upregulates the activity of the acinar cell.
- Parasympathetic supply travels in facial and mandibular nerves
- Sympathetic stimulation causes inhibition of the salivary flow
42
What are the major muscles of mastication?
1. masseter (extends from the zygomatic arch to the lateral surfaces of the caudal body and ventral ramus)
2. temporalis (extends from the temporal region of the skull to the dorsal portion of the ramus)
3. pterygoideus (extends from the pterygoid, palatine, and sphenoid bones to the angular process of the ramus
4. digastricus (extends from the occipital region of the skull to the ventral border of the body of the mandible)
43
What is the blood supply of the mandible?
inferior alveolar artery which is a branch of the maxillary artery
44
What is the course of the inferior alveolar artery in the mandible?
Off of the maxillary artery, it enters the mandible at the mandibular foramen (medial surface of the angle of the mandible) and then courses rostrally in the cavity of the mandible until it exits laterally through the mental foramen caudal to the canine tooth
45
What provides sensory innervation to the mandible and lower teeth?
Mandibular nerve! zit is a branch of the trigeminal nerve and enters the mandibular canal via the mandibular foramen
in the canal, it is considered the inferior alveolar nerve and it exits laterally through the mental foramina as the mental nerves
46
What three bones make up the muzzle?
maxilla
incisive (also known as premaxilla)
nasal
47
What is the blood supply to the maxilla?
Two branches of the maxillary artery which are:
major palatine artery (courses through caudal nasal cavity, passes through the caudal portion of the hard palate via the caudal palatine foramen, and then courses rostrally ventral to the hard palate midway between the midline and the maxillary teeth)
infraorbital artery (courses through the caudal nasal cavity dorsal to the major palatine artery and passes through the maxillary foramen and infraorbital canal of the maxilla, exiting laterally through the infraorbital foramen at the level of the carnassial tooth)
48
What innervates the maxillary teeth?
infraorbital nerve (nerve of the maxillary nerve) which courses through the infraorbital canal
49
What is the adventitia of the esophagus?
This is the outer layer of the esophagus and blends with the deep cervical fascia in the neck, then is covered by pleura and peritoneum in the thorax and abdomen
It is loosely connected to the diaphragm by a phrenicoabdominal membrane
50
What is the muscularis layer of the esophagus?
The muscularis is striated muscle for the entire length of the esophagus in dogs
BUT
It is striated muscle in cats for most of it and then will become smooth muscle in the terminal esophagus
The muscular layer arises from the cricopharyngeus muscle and the cricoesophageal tendon which is connected to the medial dorsal crest of the cricoid cartilage and serves as the cranial attachment of the esophagus
For most of the length of the esophagus, the muscular layer is composed of two poorly defined coats whose individual fibers form left and right handed spirals
In the terminal esophagus, the coats blend - the inner becomes more transverse and the outer more longitudinal
51
What are the sphincters of the esophagus?
functional but not really anatomical
Upper: pharyngoesophageal junction has the thyropharyngeus and cricopharyngeus muscles acting as a sphincter
Lower: increase in thickening of the circumferential muscling at the gastroesophageal junction in dogs - may also be influenced by the diaphragmatic crural muscles
52
What is the submucosa layer of the esophagus?
loosely connects to the mucosa and muscularis such that the mucosa can move independently
contains blood vessels, nerves and mucous glands
53
What is the mucosal layer of the esophagus?
stratified squamous epithelium
| longitudinal folds but in cats, in the terminal esophagus there are some transversely folded mucosa
54
what is the blood supply to the cervical esophagus?
cranial and caudal thyroid arteries
55
What is the blood supply for the thoracic esophagus?
the cranial two thirds are by the bronchoesophageal artery and then the caudal is by the esophageal branches of the aorta or dorsal intercostal arteries
The very terminal portion is supplied by the left gastric artery
the vessels anastomose and course within the submucosa layer
56
what is the innervation to the esophagus??
paired pharyngoesophageal nerves
recurrent laryngeal and pararecurrent laryngeal
dorsal and ventral vagal trunks
57
What nerves coordinate the oropharyngeal phase of swallowing?
```
V - trigeminal
VII - facial
IX - glossopharyngeal
X - vagus
XII - hypoglossal
```
58
The cricopharyngeal, or sometimes called esophageal pharyngeal, portion of the oropharyngeal phase of swallowing involves what?
relaxation of the thyropharyngeus and cricopharyngeus muscles so that the bolus can be delivered into the cranial cervical esophagus
59
Describe the esophageal phase of swallowing
Initiated by delivery of a food bolus into the cranial cervical esophagus
A primary peristaltic wave is initiated which propels the bolus aborally to the gastroesophageal junction
Initiation of a primary peristaltic wave depends on a sufficiently large bolus distending the cervical esophagus
In normal animals, there should be no significant amount of food in the esophagus at the end of eating
60
Describe the gastroesophageal phase of swallowing
As the peristaltic wave carries the bolus along the esophagus, the muscularis relaxes ahead of the bolus and the bolus is propelled through the gastroesophageal junction into the stomach
In dogs, the bolus of food sometimes stops in front of the gastroesophageal junction and then enters the stomach in the next bolus
61
What are the esophageal transit times of dogs in sternal versus right lateral recumbency for liquid and kibble?
sternal: 2.58 cm/s liquid and 4.44 cm/s kibble
| lateral recumbency: 7.23 cm/s liquid and 8.92 cm/s kibble
62
What are the three types of causes of dysfunction of the esophageal phase of swallowing?
mechanical (anatomical)
functional (neuromuscular)
inflammatory
63
What factors may contribute to the high complication rate associated with esophageal surgery?
lack of serosa, segmental blood supply, lack of omentum, constant motion caused by swallowing and respiration, tension
64
What is the incisura angularis?
Angular notch
Produces an intraluminal protrusion of tissue at approximately the midpoint of the lesser curvature that separates the antrum and the body
65
What are the portions of the greater omentum?
Bursal (attaches along the greater curvature except on the left where it runs obliquely across the dorsal surface of the stomach and joins the lesser omentum to close the bursa)
Splenic (forms the gastrospenic ligament)
Veil
66
What comprises the lesser omentum?
the hepatogastric ligament that passes from the liver to the stomach
67
What is the arterial blood supply of the stomach?
The celiac artery divides into the splenic, hepatic, and left gastric - all supply the stomach
The splenic gives off tributaries to the left limb of the pancreas and the spleen and then becomes the left gastroepiploic artery (supplies greater curvature of the stomach)
The hepatic artery gives off liver and gallbladder branches and then becomes the right gastric artery (supplies the blood to the pylorus and pyloric antrum)
The left gastric (supplies the fundus and small branches to the caudal esophagus)
68
What artery supplies the fundus of the stomach?
The left gastric
69
What supplies the lesser curvature of the stomach?
The left gastric artery and its anastomosis with the right gastric artery
70
What supplies the greater curvature of the stomach?
the left gastroepiploic artery and its anastomosis with the right gastroepiploic artery
71
What supplies the pylorus and pyloric antrum
the right gastric artery, which comes off the hepatic before it continues as the gastroduodenal artery
72
What is the course of the gastroduodenal artery?
The celiac branches into hepatic. Hepatic will give off branches to the liver, gallbladder, and right gastric and then it becomes the gastroduodenal. The gastroduodenal artery will go to the duodenum where its cranial pancreaticoduodeal branch supplies the right pancreatic limb and the right gastroepiploic branch supples the greater curvature of the stomach
73
what is the venous drainage of the stomach
splenic vein on the left and gastroduodenal vein on the right into the portal vein
74
What is the lymphatic drainage of the stomach?
gastric and splenic lymph nodes to the hepatic lymph nodes
75
What is the innervation of the stomach
parasympathetic fibers of the vagus nerves and sympathetic fibers of the celiac plexus
The ventral vagal trunk passes through the esophageal hiatus and then sends small branches to the pylorus, liver, and lesser curvature of the stomach
The dorsal vagal trunk sends branches to the lesser curvature and ventral wall of the stomach and then continues across the celiac plexus to follow branches of the celiac and cranial mesenteric arteries
Sympathetic fibers arise from the celiacomesenteric plexus and follow gastric branches of the celiac artery
76
What are the muscular layers of the stomach?
- longitudinal fibers on the greater curvature which pass longitudinally from the esophagus to the duodenum
- inner circular layer begins at the cardia where it forms part of the gastroesophageal sphincter and extends through the greater curvature where it blendes with oblique fibers and facilitates the grinding function of the antrum, not present in the fundus
- the oblique muscles are mostly over the body and fundic areas begin near the cardiac orifice and extend towards the pylorus and greater curvature
77
Where are the gastric glands located?
fundus and body
78
Where are the parietal cells located in the stomach and what do they secrete?
body
acids and intrinsic factor
they are also called oxyntic cells
1. they produce acid by pumping hydrogen ions into the gastric lumen
2. they produce intrinsic factor which is a mucoprotein that binds to B12 to permit its absorption later in the intestines
79
Where are chief cells located and what do they produce?
body of the stomach
| produce pepsinogen, which gets converted to pepsin in low pH and that breaks down proteins
80
Where are mucous neck cells located?
in the body and antrum of the stomach and they make mucus
81
What do the surface epithelium cells do in the stomach?
they are diffusely located in the stomach and will make mucus and bicarb
82
What do the gastric endocrine cells do?
they are located in the body of the stomach and make gastrin, histamine, and serotonin
83
How is gastric motility controlled?
swallowing initiates a receptive relaxation that decreases fundic motor activity and pressure
as the pressure in the fundus builds, gastric accommodation occurs and relaxes the fundus
surgical resection of the fundus will increase the rate of gastric emptying because of a resultant increase in pressure with the same change in volume
84
How does only liquid enter the duodenum?
Food is churned in the antrum and the pattern of motility forces ingesta aborally into the pylorus. The pylorus then closes before completion of the antral contraction and that leads to the remaining gastric contents greater than 2 mm being forced retrograde
It is called "contractile retropulsion"
This also therefore means that the gastric emptying rate for solid food is impacted by the coordinated contraction but then for liquids, its more about fundic motility
85
What is an injury that extends into the submucosal layer from the mucosa in the stomach?
an ulcer
| has a fibrotic repair process
86
how long should you withhold food to ensure an empty stomach
8-12 hours
| but longer fasting times lead to decreased pH and then higher incidence of gastroesophageal reflux
87
What pre-anesthetic could be given to decrease gastric secretions?
atropine or glycopyrrolate (anti cholinergics)
88
Where is the root of the mesentery attached?
attaches to the abdominal wall opposite the second lumbar vertebra
89
What is the duodenocolic fold?
Also called the duodenocolic ligament, it is the triangular fold created by two layers of the mesodudoenum and mesocolon
90
What does the root of the mesentery contain?
cranial mesenteric artery, intestinal lymphatics, large mesenteric plexus of nerves
91
What is the course of the cranial mesenteric artery?
off the aorta, it arises beneath the first lumbar vertebra and anastomose proximally with a branch of the celiac along with the descending duodenum and distally with a branch of the caudal mesenteric artery along the descending colon. From the root of the mesentery, the cranial mesenteric artery divides into 12-15 major branches
92
What innervates the small intestines?
the nerve fibers to the mesenteric portion of the small intestine come from the vagus and splanchnic nerves by way of the celiac and cranial mesenteric plexuses
Branches of the vagus and splanchnic nerves intermingle around the major abdominal arteries to form nerve plexuses on the arteries
The cranial mesenteric ganglion is located on the sides and caudal surface of the cranial mesenteric artery
Its nerves travel distally on the cranial mesenteric artery as the cranial mesenteric plexus
93
Describe the mucosa of the small intestines
Folded into villi such that the surface area is increased 8 times in a dog and 15 times in a cat
Single layered surface cells are either columnar (aid in absorption) or goblet (mucus-producing)
Epithelium covers the villi crypts
Deeper mucosa has the intestinal glands which are diffuse lymphoid tissue
94
How are cells produced in the intestinal crypts?
they pass onto the villi and are shed from the apex with a total replacement of the villus epithelium every 2-6 days
95
How is the submucosa arranged?
left and right spiraling fibers that provide support while still allowing the intestine to dilate
small blood vessels, lymphatics, and submucosal nerve plexus are located in the submucosal layer
96
How is the small intestinal muscular layer arranged?
thin outer longitudinal layer and a thicker inner circular layer
97
What is segmental contraction in the gut?
one of two types of gut motility
rhythmic segmentation is a random contraction of small areas of intestinal smooth muscle which slows down the forward motion of food and mizes it
It allows more effective digestion and absorption
Stimulated by local stretch reflexes and the vagus nerve --> only occurs when the intestine is full
98
What is peristalsis?
One of two types of gut motility (segmental vs peristaltic)
An organized wave of contraction to propel food aborally
Intestinal smooth muscle exhibits migrating myoelectric complexes between meals
These contractions will sweep residual undigested material through the intestinal tract
cycle recurs every 1.5 to 2 hours
The pylorus remains open during the peristaltic contractions
Controlled by the submucosal nerve plexus and myenteric plexus between the circular and longitudinal muscles
99
What is the functional unit of the small intestines?
villus with its crypts
Cells at the base of the villus are dividing and as these cells mature into enterocytes, they pass up the crypt
The base of the villus will be involved in fluid secretion and as they work up, they will lose their secretory capacity
100
Why do water soluble compounds such as amino acids and monosacharides require membrane carriers to be absorbed in the small intestines?
tight intercellular junctions between the epithelial cells are a mucosal barrier to bacteria and macromolecules - amino acids and monosacharides will need a carrier
101
How are carbohydrates transported across the mucosa of the small intestine?
glucose - Na glucose cotransport
galactose - Na galactose cotransport
fructose - facilitated diffusion
102
Which nutrients are absorbed in the ileum and not the small intestines?
cobalamin (B12) by intrinsic factor
| bile salts by Na bile salt cotransport
103
How are proteins absorbed in the small intestines?
amino acids - Na amino acid co transport
dipeptides - H dipeptide cotransport
Tripeptide - H tripeptide co transport
104
How are lipids absorbed in the small intestines?
fatty acids - bile salts form micelles
monoglycerides - diffusion
glycerol - re-esterification in the cell
105
How are fat soluble vitamins absorbed in the small intestines?
micelles form with bile salts
106
How are water soluble vitamins absorbed in the small intestines?
Na dependent cotransport
107
How is calcium absorbed in the small intestines
Ca binding protein
108
How is Fe+2 absorbed in the small intestines
binds to apoferritin in the cells
109
How is water absorbed in the small intestines
passive process because it follows the transport of solutes across the intestinal epithelium
50% of the fluid presented to it is absorbed in the jejunum and 75% in the ileum
The ileum is more effective at absorbing because of the enterocyte pore size, membrane potential difference, and type of transport process used
110
Where does most chemical digestion occur?
duodenum
Bile from the gallbladder and enzymes from the pancreas and intestinal wall combine with chyme to begin the final part of digestion
111
What hormone stimulates the release of enzymes in the small intestines?
cholecystokinin (produced int eh small intestines)
112
What does secretin do?
causes bicarb to be released into the small intestine from the pancrease to neutralize acid from the stomach
113
What do trypsin and chymotrypsin do and where do they come from?
they are proteolytic enzymes produced by the pancreas and they cleave proteins into smaller peptides
114
What does carboxypeptidase do and where does it come from?
it is a pancreatic brush border enzyme and it splits one amino acid at a time
115
What do aminopeptidase and dipeptidase do?
free the end amino acid products
116
What enzyme breaks down carbohydrates into oligosaccharides?
amylase, which is released by the pancreas
117
What is SGLUT 1?
Glucose and galactose are taken into the enterocyte by cotransport with sodium via the sodium dependent glucose transporter known as SGLUT 1
118
What is GLUT 2
fructose enters the cell from the intestinal lumen via facilitated diffusion using the transporter GLUT 2
119
what does lipase do?
pancreatic lipase breaks down triglycerides into free fatty acids and monoglycerids with the help of bile acids
Micelle formation is necessary because these enzyme are not fat soluble
120
How do bile acids help fatty acid absorption?
bile acids increase the surface area of the oil water interfaces, which aids access by pancreatic lipase
121
What are chylomicrons?
Inside the enterocyte, fatty acids and monoglycerides are used to synthesize triglycerides which are packaged with cholesterol, lipoproteins, and other lips into chylomicrons
Chylomicrons undergo exocytosis and are transported into the lacteal that is associated with each villus
122
Why do animals with ileus develop hyponatremia, hypokalemia, and hypchloremia?
with ileus/obstruction, secretion of fluid into the lumen of the small intestine is increased and the absorption of water and electrolytes is decreased
123
What is the volume of saline required to achieve normal peristaltic intraluminal pressure in a 10 cm segment of bowel for small and medium sized dogs?
16-19 ml with digital occlusion and 12-15 ml with doyens
124
Where is the cecocolic orifice located in relation to the ileocolic orifice?
In dogs, the cecocolic orifice is 1 cm distal to the ileocolic orifice
In cats, they are adjacent to each other
125
Borders of the ascending colon?
Ascending colon extends 5 cm cranially from the ileocolic orifice to the right colic flexure
Ventrally, it is covered by small intestine
Bounded by the descending duodenum on the right and lies ventral to the right limb of the pancreas, mesoduodenum, and right kidney
126
What is the blood supply of the colon?
mostly the cranial mesenteric artery which the colic artery branches off
the cecum is supplied byt the ileocolic artery
the ascending colon is supplied by the ileocolic artery proximally and the right colic artery distally
the transverse colon is supplied by the right colic artery proximally and the middle colic artery
the proximal half of the descending colon is spplied by the middle colic artery
the distal half of the descending colon is supplied by the left colic branch of the caudal mesenteric artery
**the colon has a subserosal and mural arterial network
127
Describe the colonic mucosa
Made up of columnar and cuboidal epithelial cells arranged in parallel crypts and interspersed with goblet cells
5% of the cells of the colonic mucoa are enterochromaffin cells
There are no villi nor lymph nodules but tthere are elevated solitary lymphoglandular complexes that are 3 mm in diameter
These lymphoglandular complexes are only in the cecum of cats
128
What products does the colonic mucosa absorb?
water, Na, Cl, short chain fatty acids, byproduct of bacterial fermentation
Performed by surface and crypt cells which can perform secretory and absorptive functions
129
What does the colon secrete?
K, HCO3, and mucus
130
How are solutes absorbed in the colon?
electrogenic via sodium channels or electroneutral via Na/H and Cl/HCO3 exchange
the majority of salts are absorbed via electroneutral exchange
131
What Na/H exchanger is in the basolateral membrane of the colon?
Na/H exchanger 1
132
What Na/H exchanger is in the apical membrane of the colon?
Na/H exchanger 2 and 3
133
What is the driving force for Na uptake in the colon
enhanced Na uptake is via the electrogenic route and it is enhanced by aldosterone and can be modulated with the cystic fibrosis transmembrane regulator channel
Na uptake is mirrored by Cl absorption through the apical Cl channels and via paracellular transport
134
How is water moved across the colon?
active absorption and secretion occurs via paracellular and transepithelial routes
aquaporins will help transport water
135
What is the role of the Na+ 2Cl K cotransporter type 1 protein in the basolateral membrane?
- goblet and columnar epithelial cells secrete mucus. Maintaining the mucus secretion requires ion uptake by the basolateral membrane
this ion channel has its enhanced activity triggered by lowered intracellular Cl as a result of secretion of Cl at the apical border
The majority of the apical border Cl efflux is via the cystic fibrosis transmembrane regulator channel and messengers such as adenosine monophosphate, protein kinase A, protein kinase C, calcium/calmodulin dependent kinase, cyclic guanosine monophosphate-dependent kinase increase its activity
136
What influences potassium secretion in the colon?
Potassium ions are secreted via two types of channel in the apical membrane and channel activity is increased by aldosterone and glucocorticoids
137
How are short chain fatty acids absorbed in the colon?
these are products of colonic bacterial fermentation of dietary fiber and are absorbed in parallel with NaCl
Include butyrate, acetate, and proprionate
They will also stimulate Na absorption by a combo of acidification and activation of apical membrane Na/H transporter
ALso stimulate HCO3 production which leads to Cl absorption
Finally, also aid in preventing colonic irritation by reducing ionization of bile acids and long chaing fatty acids
138
What controls the motility of the colon?
Dependent on the colonic wall intrinsic plexuses which are located between the longitudinal and circular muscle layers (myenteric, aka Auerbach) or in the colonic submucosa (submucous, aka Meissner plexus_
Parasympathetic innervation via pre ganglionic vagal and pelvic fibers stimulate colonic motility
Sympathetic innervation via the mesenteric plexus, interior mesenteric, and hypogastric plexus will inhibit motility
139
Describe microfold, or M cells
M cells move protein, viruses, bacteria, and non infectious particles transepithelially to the subepithelial lymphoid cells
They have an invagination at the basolatearl membrane which forms an intraepithelial pocket where memory T cells interact with naive and memory B cells and D cells interact with M cells
140
What is an intraepithelial lymphocyte?
A cell in the colonic immune system
lymphocytes that have migrated to above the basement membrane and are found between colonocytes
mostly effector memory cells
They can express CD8alphaalpha
thought to play a role in epithelial homeostasis, cancer surveillance, defense against pathogens
141
What type of collagen is predominant in the proliferative phase of colonic wound healing?
type III accounts for 30-40% of the granulation tissue
142
what types of collagen are in the submucosa of normal colon?
type I - 68%
type III - 20%
type V - 12%
**collagen is produced by the submucosa AND smooth muscl cells
143
What bacterial products will worsen wound healing in the colon?
E coli makes endotoxin lipopolysaccharide (LPS) and that induces collagenase synthesis
144
What are the borders of the rectum?
the recutm is attached dorsally to the ventral surface of the sacrum by the mesorectum, which becomes progressively shorter caudally and ends at the second or third caudal vertebra
The peritoneal surface of the mesorectum continues dorsally and laterally along the sides of the pelvis as pareital peritoneum
the visceral peritoneum along the distal rectum reflects cranially to blend with the parietal peritoneum
Caudal to the point of the mesorectal reflection, the rectum is retroperitoneal
Muscle wise, the rectum is bounded dorsally by the right and left ventral sacrocaudal muscles, laterally by the levator ani muscle, and ventrally by the vagina/cervix or the urethra in the male
145
What are the layers of the rectum
mucosa, submucosa, and muscularis
| there is a serosa layer in the intraoperitoneal region of the rectum but not the retroperitoneal portion
146
what is the blood supply to the rectum?
CRANIAL rectal artery
the middle and caudal rectal arteries supply insignificant amounts
The intrapelvic rectum has a poorer blood supply than the proximal rexctum so the cranial rectal artery should be preserved, though this is less important in cats
147
How is the mucosa of the anal canal divided, cranial to caudal?
columnar, intermediate, and cutaneous zones
148
Describe the columnar zones of the anal canal
contains longitudinal or oblique ridges known as anal columns which extend caudally for 7 mm
149
describe the intermediate zone of the anal canal
irregular sharp edged fold less than 1 mm wide that unites with the anal columns
divided into four scalloped arches and contain anal sinuses
the anocutaneous line is the boundary between the mucous membrane and the skin but it cannot be differentiated from the intermediate zone - it is also stratified squamous epithelium
150
describe the cutaneous zone of the anal canal mucosa
internal - anus - external
the internal portion is 4 mm wide and has a moist surface, the duct from the anal sac opens up here
the external portion is hairless and actually outside the anal canal - the circumanal glands are here and their size makes the width of this area vary from dog to dog
151
What is the blood supply of the anal canal mucosa and sphincter?
the caudal rectal arteries which are branches of the internal pudendal
152
Where are the anal sacs located/
crosses the caudal border of the internal anal sphincter and usually opens within the inner cutaneous zone of the anal canal
in cats, the origice of the anal sac duct opens on a pyramidal prominence 0.25 cm lateral to the anus
153
What makes up the pelvic diaphragm?
the pelvic fascia along with the coccygeus and levator ani muscles
154
What makes up the pelvic fascia?
attached to the dorsomedial surface of the internal sacrotuberous ligament and superficial gluteal muscle fascia
in male dogs, the fascia is adhered to the ischiourethralis, ischiocavernosus, and bulbospongiosus and retractor penis
in females, the fascia incorporates the constrictor vulva muscles
155
What are the isciorectal fossae?
bilateral, deep, pyramidal depressions lateral to the tail and anus
bounded medially by the external anal sphincter, constrictor vulvae or retractor penis, levator ani, coccygeous muscles and the superficial gluteal and sacrotuberous ligament
156
What do the anal glands produce?
They have tubuloalveolar glands that produce fatty secretions in the dog. secretory epithelium in the anal glands produce large amounts of neutral glycoproteins that have various terminal sugars like alpha L fucose residue
This sugar is hydrophobic and may contribute to the viscoelastic properties of the anal gland mucus
Paranala sinus glands are in the wall of the anal sac and are what produce the serous to pasty foul selling liquid
157
What makes up the internal anal sphincter?
```
smooth muscle (therefore involuntary)
formed by a caudal thickening of the circular coat of the anal canal
inner surface is lined by submucosa and separated from the external anal sphincter externally by a thin layer of fascia
```
158
What makes up the external anal sphincter?
It is a circular band of striated muscle
In a craniocaudal direction, its dorsal aspect is wider than the ventral aspect
Fibers of the external anal sphincter decussate ventrally and blend with the urethral muscle and constrictor vulvae or bulbospongiosus muscle
Laterally, fascia unites the cranial border of the external anal sphincter with the caudal borders of the levator ani
Dorsally, the muscle widens and attaches to the fascia ventral to the third caudal vertebra
159
What muscles aid in peristalsis of the anal canal and rectum and also prevents them from being pulled cranially in a peristaltic wave?
rectococcygeus muscles, which are an accumulation of outer longitudinal fibers from each side of the rectum
160
What does the pelvic plexus innervate?
The nerve fibers that innervate the rectum, internal anal sphincter, and the rectococcygeus muscles
The pelvic nerves have the parasympathetic fibers from the first, second, and third sacral nerves -- these are excitatory to the rectum and inhibitory to the internal anal sphincter
The hypogastric nerves have the sympathetic fibers and are from the caudal mesenteric ganglion - inhibitory to the rectum and excitatory to the internal anal sphincter
161
What is the innervation of the external anal sphincter
voluntary motor by the caudal rectal branch (off of the pudendal nerve)
sensation from the perineal branch
162
What determines smooth muscle membrane potential in the GI tract?
resting membrane potential in the GI is not constant! it oscillates overtime as dictated by the pacemaker cells - the interstitial cells of Cajal
163
What are the attachments of the liver?
the vena cava
coronary ligament - attaches liver to diaphragm
triangular ligaments - com from the coronary, usually two right sided ones and a left
hepatorenal ligament - attaches the caudate lobe to the right kidney
lesser omentum - between the porta hepatis and the lesser curvature of the stomach (aka the hepatogastric ligament)
proximal duodenum - hepatoduodenal ligament
164
What makes the blood supply to the liver?
20% of the blood volume and 50% of the oxygen are from the hepatic artery (branch of the celiac)
80% of the blood volume and 50% of the oxygen are from the portal vein
165
What is the path of the hepatic artery?
From the celiac, the hepatic artery comes off. At the porta hepatis, the hepatic artery will divide into two to five branches that penetrate the different lobes of the liver
Usually, a right lateral branch supplies the caudal and right lateral lobes. A right middle branch supplies the right medial lobe, the dorsal part of the quadrate, and a part of the left medial lobe. The left branch supplies the left lateral lobe, part of the quadrate, and the left medial lobe
The cystic artery to the gallbladder comes off the left branch
166
Branches of the portal vein
after entering the liver, the canine portal vein divides into right branch - supplying the caudate process and right lateral lobe - and the left lateral, left medial, and quadrate branches
167
What drains the liver of venous blood
usually 6-8 hepatic veins drain into the caudal vena cava
168
describe the flow of bile
within the liver, canaliculi drain bile into interlobular ducts --> lobar ducts --> hepatic ducts --> exit the liver parenchyma and form the extrahepatic biliary tract
hepatic ducts usually 2-8 in number and will converge to form the common bile duct
the point at which the first hepatic duct joins the cystic duct is when the common bile duct commences
169
How does the common bile duct enter the duodenum in the dog?
enters at the major duodenal papilla adjacent to, but not conjoined, with the pancreatic duct
smooth muscle fibers surround the two ducts and make a sphincter, called the sphincter of Oddi
the accessory pancreatic duct in the dog is the larger duct and enters at the minor duodenal papilla about 2 cm aboral
170
How does the common bile duct enter the duodenum in the cat
CBD and the pancreatic duct joint just before their entry into the duodenum at the major duodenal papilla
only about 20% of cats have an accessory duct at the minor papilla and therefore, any diease at the major duct has the potential to affect the entire exocrine pancreatic secretion process
171
What is the liver's role in protein metabolism?
Produces 20% of the body's total protein production including albumin, alpha/beta/gamma globulins as well as coag proteins and enzymes
All albumin is made in the liver! A decrease in albumin is not seen until 70-80% of liver mass is lost
172
what is the liver's role in carbohydrate metabolism?
maintains plasma glucose concentration through gluconeogenesis and glycogenolysis
hypoglycemia can result from severe hepatic disease but it usually also only occurs after 70-80% of function is lost
173
what is the liver's role in cholesterol production?
makes cholesterol from chylomicrons and lipoproteins in the plasma and stores lipids in the form of triglycerides that are produced from fatty acids
174
What coagulation factors are not produced by the liver?
factor VIII and vWF which are mostly made by the vascular endothelium
175
What are the vitamin K dependent clotting factors?
II, VII, IX, X
| the liver carboxylates vitamin K
176
How does the liver contribute to the body's reticuloendothelial function?
the liver contributes the largest portion in the body
it is part of the immune system responsible for phagocytosis of harmful endogenous and foreign substances
Kupffer cells are hepatic macrophages distributed through the hepatic sinusoids
177
What is the course of bile in the liver?
bilirubin becomes bound to albumin in the circulation and is transported to the liver
in the hepatocyte, bilirubin gets conjugated to glucuronic acid and is then excreted into bile canaliculi
bile acids are made in the liver from cholesterol and then conjugated with taurine (or in dogs, may also be to glycin)
After excretion by the hepatocyte, conjugated bilirubin and bile acids are transported through the hepatic ducts and stored in the gallbladder
When digested food enters the duodenum, cholecystokinin is released from the cells in the mucosal surface of the small intestine and the gallbladder contracts
178
What is the hepatic buffer response?
Disruption in portal perfusion to the liver results in increased hepatic artieral perfusion because of an intrinsic regulatory mechanism in the liver called the hepatic buffer response. This is believed to occur secondary to ta lack of washout of adenosine (a vasodilator) via the portal circulation, which then triggers a compensatory increase in arterial perfusion.
During partial hepatectomy, splanchnic blood flow remains constant through the portal system, with perfusion through the remaining portal branches increased and then a resulting hypertrophy of the remaining parenchyma
179
Name the tributaries of the portal vein from caudal to cranial
cranial mesenteric vein, caudal mesenteric vein, splenic vein, left gastric vein, and in dogs - the gastroduodenal vein
The cranial mesenteric is the largest tributary
180
What are the branches of the portal vein once they enter the liver
divide into left and right portal veins
The left is bigger
The right portal vein is short and supplies the caudate process of the caudate lobe and the right lateral lobe
The left portal vein branches into right ventral lateral branch (the central portal vein and suppies the right medial lobe and a small papillary branch) and then the quadrate, left medial, and left lateral branches
181
Describe the course of the hepatic veins
Blood from the portal vein and hepatic artery branches mix within the hepatic sinusoids then collect in central veins and then merge into hepatic veins
Usually dogs have 5-8 hepatic veins that form a partial spiral around the caudal vena cava
The left hepatic vein is the biggest! it terminates on the left lateral aspect of the vena cava and is encompassed by hepatic parenchyma
The quadrate and right medial hepatic veins usually converge to form a single terminus that joins the left hepatic vein
182
What embryologic vessel becomes the hepatic portion of the caudal vena cava?
the cranial segment of the right vitelline vein. The left will atrophy
Originally, the right and left vitelline veins carry blood form the yolk sac to the sinus venosus
183
What embryologic vessels become the portal vein
the caudal segments of the left and right vitelline veins will anastomose and portions of the anastomoses and their associated vitelline segments atrophy and reform to become the portal vein
184
What are the three categories of liver vascular disease?
1. congenital portosystemic shunt
2. portal vein hypoplasia (may be with or without portal hypertension)
3. disturbances in portal outflow
185
What percentage of portosystemic shunts in dogs and cats are extrahepatic?
66-75% are extrahepatic
186
What are the most common cause of acquired portosystemic shunts?
hepatic fibrosis (cirrhosis), portal vein hypoplasia with portal hypertension, and hepatic arteriovenous malformations
187
What is idiopathic noncirrhotic portal hypertension>
this is primary portal vein hypoplasia with portal hypertension
characterized by intrabdominal portal hypertension, patent portal vein, lack of cirrhosis
188
what is microvascular dysplasia?
this is the old term for primary hypoplasia of the portal vein withOUT hypertension
characterized by small intrahepatic portal vessels, portal endothelial hyperplasia, portal vein dilatation, random juvenile intralobular blood vessels, and central venous hypertrophy
Can occur alone or with congenital PSS (may be 58% of dogs and 87% of cats with PVH/MVD also have PSS)
189
How much liver function must be lost for hepatic encephalopathy to occur?
70%
190
Presence of a hypercoagulable state was found to be ---- times more likely when a patient has clinical signs of hepatic encephalopathy
40 times
191
How does ammonia cause hepatic encephalopathy?
increases brain tryptophan and glutamine, decreases ATP availability, increases neuronal and cellular excitability, increases glycolysis, can cause brain edema, decreases microsomal Na, K-ATPase in the brain
192
How do aromatic amino acids cause hepatic encephalopathy?
decrease DPOA neurotransmitter synthesis, alter neuroreceptors, increase production of false neurotransmitters
193
How do bile acids cause hepatic encephalopathy?
membranocytolytic effects alter cell membrane permeability, make blood brain barrier more permable to other hepatic encephalopathic toxins, and impair cellular metabolism because of cytotoxicity
194
how does descreased alpha ketoglutaramate cause hepatic encephalopathy
diversion from krebs cycle for ammonia detoxification, decreased ATP availability
195
how do endogenous benzodiazepines cause hepatic encephalopathy
neural inhibition through yperpolarization of neuronal membrane
196
how does tyrosine converted to octopamine cause hepatic encephalopathy
impairs norepinephrine action
197
how does phenylalanine to phenylethylamine cause hepatic encephalopathy
synergistic with ammonia and SCFA
198
How does methionine to mercaptans cause hepatic encephalopathy
decreases ammonia detoxification in the brain urea cycle, derived from the GI tract, decreases microsomal NaK ATPase
199
how does GABA relate to hepatic encephalopathy
neural inhibition by hyperpolarizing neuronal membrane and increasing blood brain barrier permeability to GABA
200
how does glutamine cause hepatic encephalopathy
alters blood brain barrier amino acid transport
201
how does phenol (from phenylalanine and tyrosine) cause hepatic encephalopathy
synergistic with other toxins, decreases cellular enxymes, is both neurotoxic and hepatotoxic
202
how do SCFAs (short chain fatty acids) cause hepatic encephalopathy
decrease microsomal na/k ATPase in brain, uncople oxidative phsophorylation, impair oxygen utilization, displace tryptophan from albumin which causes increased tryptophan
203
How does tryptophan cause hepatic encephalopathy
directly neurotoxic, increases serotonin through neuroinhibition
204
What is the equation for RER
RER in kcal/d = 70 x kg^0.75
205
How much water does a normal cat or dog need a day to maintain hydration
50-100 ml/kg/day
| Olie, for example, needs about 1.5 to 3 liters a day
206
What is the initial feeding volume for a bolus of liquid food in a feeding tube? Other than the guideline of 1/3 RER divided into several meals
start at 3-5 ml/kg q2-4 hours
| then can increase to 15 ml/kg over time but many dogs and cats can do up to 22-30 ml/kg in a single feeding
207
What happens when you feed an emaciated animal that causes refeeding syndrome?
in an emaciated animal, intracellular cations are depleted even though plasma levels are normal. When refeeding resumes, plasma cations radiply shift into the cells and this leads to decreases in potassium, phosphorus, and magnesium concentrations
Clinical signs are usually seen within four days and include weakness, fluid retention, ECG abnormalities, dyspnea, vomiting, diarrhea, ileus, renal dysfunction, and tetany
208
What percent of the total pancreatic mass is formed by the exocrine portion and its associated vessels, nerves, and ducts?
98%
| That means only 2% is dedicated to the endocrine portion
209
How is the endocrine portion of the pancreas organized?
It has islands of polygonal cells known as ilest of Langerhans that form anastomosing cords nestled in the pancreatic lobules and intimately associated with the acinar cells
Within the islets are four cell types - alpha, beta, delta and F (or PP) cells
210
what do the alpha cells of the pancreas produce
glucagon
211
what do the beta cells of the pancreas produce
insulin
212
what do the delta cells of the pancreas produce
somatostatin
213
what do the F or PP cells of the pancrease produce
pancreatic polypeptide
214
What is the blood supply of the pancreas
celiac artery via the splenic and hepatic arteries
the splenic is the primary supply to the left limb
the hepatic terminates as the cranial pancreaticoduodenal artery and enters the body of the panceas and goes into the right limb of the pancreas
the caudal pancreaticoduodneal artery supplies the distal right limb and is from the cranial mesenteric
215
what is the innervation of the pancreas
it is by the enteric nervous system and branches of the vagus nerve
the pancreatic blood vessels are innervated by celiac and superior mesenteric plexuses and acinar and islet cells are innervated by cholinergic neurons that synapse with vagal fibers
pancreatic juice secretion is stimulated by parasympathetic activity and inhibited by sympathetic activity
216
What percent of dogs have the transport of pancreatic secretions through a single duct from each limb of the pancreas
68%
The ducts form a Y and the tail of the Y makes the accessory pancreatic duct which is also called the duct of Santorini
The second duct is the duct of Wirsung which emerges from the main duct of either the right or left lobe and enters the duodenum adhacent to the bile duct at the major duodenal papilla
217
What do acinar cells of the pancreas produce
aid in the function of digestion
Secrete digestive enzymes like alpha amylase and lipase, bicarb, absorption factors, and inactive zymogens like trypsinogen, chymotrypsinogen, proelastase, procarboxypeptidase, prophospholipase
218
Where does intrinsic factor get made and what does it help do?
made by the pancreas and aids in B12 absorption in the distal ileum
219
How does trypsin get activated?
enteropeptidase (made by the enterocytes of the duodenal mucosa) cleaves trypsinogen to trypsin
220
What is the role of trypsin in stimulating digestion?
Trypsin, cleaved by enteropeptidase from trypsinogen, will cleave activation peptides from other zymogens to make chymotrypsin, elastase, carboxypeptidase, and phospholipase
221
What does lipase with colipase do?
hydrolyzes ester bonds in triglycerides and alpha amylase hydrolyzes starches
222
What mechanisms prevent the autodigestion of the pancreas?
1. proteolytic and phospholipolytic enzymes are stored as inactive zymogens
2. segregated storage of the zymogens will have then packaged as membrane bound granules within the rough endoplasmic reticulum of the pancreas
3. acinar cells synthesize pancreatic secretory trypsin inhibitor which is stored with the digestive enzymes to prevent premature activation of the zymogens
223
What stimulates the secretion of pancreatic enzymes?
- vagal stimulation from smell or anticipation of food
- movement of partially digested food into the duodenum
- duodenal mucosal cells releasing and secreting secretin and cholecystokinin into the blood, which then go to the pancreas and stimulates large volumes of bicarb fluid secretion (secretin) and digestive enzymes (cholecystokinin)
This is a biphasic response - first phase is rich in pancreatic enzymes at 1-2 hours after eating and the second is more bicarb heavy and peaks at 8-11 hours after eating
224
What anesthestic drug should be avoided in patients with hypoglycemia?
alpha 2 agonist cause hypoinsulinemia and hyperglycemia. For some reaosn, tobias thinks this will make a hypoglycemic patient be unpredictable
225
What is the function of amylases?
digest starch and glycogen in the duodenal lumen via hydrolysis
the final product is glucose
226
What other factors do the active lipases phospholipase A2, lipase, and carboxylesterase require to hydrolyze triglyceride molecules?
bile salts and colipase
