Canine GI Tract Flashcards
How does the GI tract process food?
Ingestion- prehension, mastication, deglutition (swallowing)
Absorption- compaction and peristalsis
Digestion- mechanical and chemical
Excretion- defecation
What is the digestive tract?
A tube from the mouth to the anus
Alimentary tract and accessory organs
Alimentary tract
Oral cavity
Pharynx
Esophagus
Stomach
Large intestine
Small intestine
Accessory organs
Teeth
Tongue
Salivary glands
Liver
Gallbladder
Pancreas
Where is the esophagus commonly obstructed?
Thoracic inlet
Base of the heart
Esophageal hiatus of the diaphragm
What is the function of the stomach?
Store food for churning and move chyme to the small intestine
Stomach position when it’s empty
Left side of the abdomen
Stomach position when it’s fully filled
Moved caudally contracting ventral body wall
Where are the cardia, fundus and body located?
Left of the midline
Angular notch
Indentation on the concave lesser curvature of the stomach
Pylorus
Sphincteric termination of the stomach
Right of the mid-line
Joins body to the descending duodenum
3 parts: pyloric antrum, p. canal and p. sphincter
Relatively fixed
Stomach in a healthy dog
Non-palpable but freely movable
Exterior of the stomach
Greater and lesser curvature
Interior of the stomach
Gastric mucosa made of cardiac (mucous), proper gastric (pepsin and HCL) and pyloric (mucous)
Rugae (empty mucosa and submucosa are thrown into folds)
Gastric Dilatation Volvulus
Occurs within 2 hours of eating
Dilation occurs with accumulation of gas, fluid and food within the stomach
What breeds is GDV most common in?
Most common in large deep chested dogs like great danes and german shepherd
What are the clinical signs of GDV?
Abdominal distention
Restlessness
Abdominal pain
Attempts to vomit (retching)
Hypersalivation
How does GDV affect the pyloris?
Pylorus rotates 90-360 degree clockwise direction from right to left over the fundus and body
What happens to the stomach with GDV?
Distended stomach compresses the cd. vena cava and portal vein to reduce the venous return to heart
Gastric contents ferments and stomach dilates
Attempts to vomit, usually unsuccessful
How is the duodenum affected by GDV?
Duodenum becomes trapped between distal esophagus and stomach
What are the affects of GDV?
Decreased cardiac output
Hypolemic shock and metabolic acidosis
Hypotension and tissue hypoxia
Liver can’t clear gram neg endotoxins–> endotoxemia
What are the treatments of GDV?
IVFs
Gastric decompression (orogastric tube)
Gastrocentesis (18 gauge needle, right side of the abdomen)
Small intestine
Major digestive organ and main site for absorption
Divided into duodenum, jejunum and ileum
How is the surface area of the small intestine increased?
Plicae cicularis (villi and microvilli)
Duodenum parts
Cr. duodenal flexure (r. side of midline)
Descending duodenum (r. side of midline)
Cd. duodenal flexure (near pelvic midline)
Duodenojejunal flexure
Mesoduodenum
Attaches the duodenum to abdominal roof/ abdominal wall
What is the function of the duodenum?
Enzymatic digestion and absorption
What are the lobes of the liver?
R. and l. medial
R. and l. lateral
Quadrate lobe
Caudate lobe- caudate and papillary process
Quadrate lobe
Between right and left medial lobes
Contact the gall bladder
Caudate lobe
Caudate process- renal impression of right kidney
Papillary process- lies along lesser curvature of stomach
Gall bladder
Temporary storage of bile
Located beween r. medial and quadrate lobes
Hepatic duct and cystic duct
Hepatic duct and cystic duct
Drains lobes into gall bladder
Inactive digestion
Common bile duct
Formed by union of cystic and hepatic ducts
Opens on major duodenal pailla
One duct in cats (80%)
What is the functional bile flow?
- Inactive digestion periods
- Active digestion periods
Inactive digestion periods
Papilla closed by smooth mm sphincter
Bile flow upward through cystic duct into gall bladder
Active digestion periods
Hormonal actions opens sphincter
Cystic contractions forces bile out of gall bladder
Active digestion periods
Hormonal actions opens sphincter
Cystic contractions forces bile out of gall bladder
What is the function of the pancreas?
Exocrine: digestive enzymes- lipase and amaylase
Endocrine: hormones, insulin, glucagon and gastrin
Pancreatic duct
Small, joins the bile duct and open via major duodenal papilla (dog)
Large in cats
Accessory ducts
Large in dogs
Usually absent in cats (no minor papilla)
Opens via minor duodenal papilla
Jejunum
Bulk of small intestine, long, mobile mesentery
Fills the space between the stomach and pelvic inlet
Mesojejunoileum
Forms root of mesentery
Contains cr. mesenteric artery
Long mesentery
Significance of the Mesojejunoileum
Freely movable and liable to herniate through epiploic foramen
What are the boundaries of the jejunum and ileum?
Dorsally: caudate lobe and cd. vena cava
Ventrally: portal vein
Cranially: liver
Ileum
Short terminal part of small intestine
Has anti-mesenteric blood vessels
Opens into large intestine at ileocolic orifice
Intussusception
Condition where the ileum slides into an adjacent part of the colon
Oral or aboral
Occurs in certain anatomical changes, peristaltic activity or due to 2 degree condition
What can venous obstruction lead to?
Necrosis
Where does Intussusception occur?
Young animals at ileocolic junction
Resection and anastomosis
Incise into the abdomen and inspect intussusception is found
Place intussusception site outside the abdomen on moistened lap sponges
Use absorbable suture
What is the clinical significance of the jejunum?
Common site of obstruction
A wide variety of foreign objects may be ingested (young dogs)
What are the parts of the large intestine?
Cecum
Colon (ascending, transverse, descending)
Rectum (anal canal)
Cecum
Right of median plane
Blind ended sac joined to ileum by ileocecal fold
Not much significance clinically
How does the cecum commincate with ascending colon?
Via cecocolic orifice
Shapes of cecum?
Dog- corkscrew
Cat- comma shape
Colon
Ascending- right of midline (r. colic flexure)
Transverse- cr. to root of mesentery (l. colic flexure)
Descending- l. of midline
Duodenocolic fold
Peritoneal fold
Connecting ascending duodenum to descending colon
What is the clinical significance of the Duodenocolic fold?
Don’t confuse with adhesion!!!
Rectum
Anal canal
Columnar zone
Intermediate zone
Cutaneous zone- paranal sinuses (opening of excretory duct)
Paraanal Sac
Located @ 4 and 8 o’clock position
Apocrine and sebaceous glands
How is anal continence controlled?
Internal anal sphincter (smooth)
External anal sphincter (striated)
What is the function of the paraanal sac?
Reservoirs of secretion
Anocutaneous junction
Compression of sac at defecation
Territorial scent marking
Where are anal sac disease most common?
Toy breeds like poodles and chihuahuas
Affects 10% of dogs
What are the signs of anal diseases?
Behavior changes (scooting, licking, biting at tailhead or anus)
Pain/tenderness with sitting
How do you treat anal diseases?
Expressing anal sacs regularly before a problem occurs
Add fiber to diet and irrigation with saline
How do you treat impacted anal sacs?
Anal saculectomy (surgical excision of the sac)
What are some different anal sac diseases?
Impaction
Infection (sacculitis)
Abscessation
Neoplasia
Cd. mesenteric artery
Provide blood supply to GIT
Cr. mesenteric artery
Common trunk
Middle colic artery
R. colic artery
Ileocolic
What makes up the aorta artery?
Celiac artery
Cr. mesenteric artery
Cd. mesenteric artery
Common hepatic artery
L. gastric artery
Splenic artery
Peritoneum
Serous (methothelium), lines abdominal and pelvic
Parietal Peritoneum
Lines wall of the abdominal cavity
Visceral peritoneum
Closely invests an organ surface
Connecting peritoneum
Between visceral and parietal (mesentery)
Double folds that connects things
Mesentery
Bowel to body wall (mesocolon)
Omentum
Stomach to something else (Great omentum)
Fold
Connects different parts of bowel (ileocecal fold)
Ligament
Connects organ other than bowl to body wall or to the bowl (broad ligament)
Peritoneum (embryogically) stomach and duodenum
Perimordia are attached to dorsal and ventral body wall by dorsal and ventral mesogastrium
Peritoneum (embryogically) liver
Primodrium grows ventrally and develops between layers of ventral mesogastrium
Falciform ligament
Part of the ventral mesogastrium between liver and body wall
Lesser Omentum
Part between stomach and liver
Lesser curvature of stomach to liver
Greater Omentum
Greater curvature to dorsal body wall with superficial and deep leaves
