Anatomy Review

Question 1

Esophagus blood supply

Answer 1

Arterial - left gastric artery and left inferior phrenic artery

Venous -
Left gastric vein -> portal venous system
Esophageal veins -> azygos vein -> IVC (systemic)

Question 2

Esophagus innervation

Answer 2

Parasympathetic innervation via anterior and posterior gastric nerves (vagal trunks)

Sympathetic innervation via thoracic trunks of the greater splanchnic nerves

Question 3

Stomach blood supply

Answer 3

Lesser curvature
Right and left gastric arteries (from celiac trunk)

Greater curvature
Right and left gastro-omental (gastroepiploic) arteries (from gastroduodenal and splenic arteries respectively)

Fundus: short and posterior gastric arteries (from the splenic artery)

Question 4

Stomach innervation

Answer 4

Parasympathetic innervation via vagus nerve Sympathetic innervation via celiac plexus (from T6-T9)

Question 5

Esophagus histology and structural features

Answer 5

Mucosa: stratified squamous epithelium

Submucosa: connective tissue, lymphocytes, plasma cells, nerve cells

Muscularis propria (muscularis externa): inner circular, outer longitudinal muscle
Upper 1/3: striated muscle
Middle 1/3: transition zone
Lower 1/3: smooth muscle

Question 6

Stomach parts

Answer 6

Cardia 
Fundus 
Body 
Antrum 
Pylorus

Question 7

Duodenum function

Answer 7

Modulates enteral pH via secretin → decreased gastric acid secretion, increased bicarbonate secretion

Secretes CCK to stimulate bile secretion

Site of iron absorption

Question 8

Duodenum blood supply

Answer 8

Branches of celiac artery and superior mesenteric artery

Question 9

Duodenum innervation

Answer 9

Parasympathetic innervation via vagus nerve

Sympathetic innervation via greater and lesser splanchnic nerves

Question 10

Duodenum histology and structural features

Answer 10

4 parts 
Superior (5 cm) 
Descending (7-10 cm) 
Horizontal (6-8 cm) 
Ascending (5 cm) 

1st part is intraperitoneal; rest is retroperitoneal

Question 11

Esophagus function

Answer 11

Muscular tube approximately 40 cm long with a diameter of 2 cm Extends from pharynx to the stomach

Question 12

Stomach function

Answer 12

Delivers food to intestine for digestion and absorption

Secretes acid, probably to reduce enteric infections/pneumonia; facilitate digestion of protein/iron/B12

Secretes intrinsic factor to facilitate B12 absorption

Minor contribution to initial protein digestion via pepsin

Question 13

Jejunum function

Answer 13

Absorption of sodium, water, and nutrients (protein, carbohydrates, fat, folic acid, and vitamin A, B, C, D, E, K)

Question 14

Jejunum blood supply

Answer 14

Superior mesenteric artery

Question 15

Jejunum innervation

Answer 15

Parasympathetic innervation via fibres of the posterior vagal trunk

Sympathetic innervation via fibres of T8-T10

Question 16

Jejunum histology and structural features

Answer 16

Deep red colour

2-4 cm in thickness

Thick and heavy wall

Plicae circulares are large, tall, and closely packed

Has long vasa recta

Scant fat in mesentery

Scant Peyers patches

Question 17

Ileum function

Answer 17

Absorption of sodium, water, nutrients, soluble vitamins (only site of vitamin B12 absorption), and bile salts (entero-hepatic circulation)

Question 18

Ileum blood supply

Answer 18

Superior mesenteric artery

Question 19

Ileum innervation

Answer 19

same as jejunum

Question 20

Ileum histology and function

Answer 20

When compared to jejunum

Paler pink colour

2-3 cm in thickness

Thin and light walls

Plicae circulares are small and sparse

Contains more mesenteric fat

Many Peyer’s patches

Question 21

Large bowel function

Answer 21

Absorption of water (5-10% of total water)

Bacteria: further digestion of chyme and metabolism of undigested CHO to short chain fatty acids

Formation and storage of feces

Question 22

Large bowel blood supply

Answer 22

Branches of superior and inferior mesenteric arteries

Rectal blood supply: sigmoid, right pudendal, and rectal arteries

Question 23

Large bowel innervation

Answer 23

Parasympathetic innervation via vagus nerve

Sympathetic innervation via greater and lesser splanchnic nerves

Question 24

Large bowel histology and structure

Answer 24

Consists of cecum, colon (ascending, transverse, descending, and sigmoid), rectum and anal canal Features include teniae coli, haustra, and omental appendices

Question 25

Liver function

Answer 25

Glucose homeostasis Plasma protein synthesis Lipid and lipoprotein synthesis Bile acid synthesis and secretion Vitamin A, D, E, K, B12 storage Biotransformation, detoxification Excretion of compounds

Question 26

Liver blood supply

Answer 26

``` 2 sources Portal vein (75-80%) Hepatic artery (20-25%) ```

Question 27

Liver innervation

Answer 27

Parasympathetic innervation via fibres of the anterior and posterior vagal trunks Sympathetic innervation via fibres of the celiac plexus

Question 28

Liver histology and structure

Answer 28

Largest internal organ Composed of 4 lobes (left, right, caudate, quadrate) and divided into 8 segments

Question 29

Biliary tract function

Answer 29

Gallbladder functions to store and release bile that is produced in the liver Bile is used to emulsify fat and is composed of cholesterol, lecithin, bile acids, and bilirubin CCK stimulates gallbladder emptying while trypsin and chymotrypsin inhibit bile release

Question 30

Biliary tract blood supply

Answer 30

Cystic artery

Question 31

Biliary tract innervation

Answer 31

Parasympathetic innervation via vagus nerve Sympathetic and visceral innervation via celiac nerve plexus Somatic afferent fibres via ight phrenic nerve

Question 32

Biliary tract histology and structure

Answer 32

Consists of the hepatic ducts (intrahepatic, left, right and common), gallbladder, cystic duct, common bile duct, and ampulla of Vater

Question 33

Pancreas function

Answer 33

Endocrine function: islets of Langerhans produce glucagon, insulin, and somatostatin (from the α, β, and δ cells, respectively) Exocrine function: digestive enzymes are produced including amylase, lipase, trypsin, chymotrypsin, and carboxypeptidase

Question 34

Pancreas blood supply

Answer 34

Anterior superior pancreaticoduodenal artery (from the celiac trunk) Anterior inferior pancreaticoduodenal artery (from the superior mesenteric artery) Dorsal pancreatic artery (from the splenic artery) Pancreatic veins drain into the portal, splenic, and superior mesenteric veins

Question 35

Pancreas innervation

Answer 35

Parasympathetic innervation via vagus nerve Sympathetic innervation via abdominopelvic splanchnic nerves

Question 36

Pancreas structural and histology

Answer 36

4 parts of pancreas: head (includes uncinate process), neck, body, and tail (Major) pancreatic duct connecting to common bile duct prior to ampulla of Vater Accessory pancreatic duct connected directly to duodenum

Question 37

Retroperitoneal structures

Answer 37

SAD PUCKER ``` Suprarenal glands (adrenal glands) Aorta/IVC Duodenum (second to fourth segments) Pancreas (tail is intraperitoneal) Ureters Colon (only the ascending and descending branches) Kidneys Esophagus Rectum ```

Question 38

Where are Vitamin B12 and bile acids absorbed

Answer 38

Only the ileum and not jejunum

Question 39

Methods of visualizing the esophagus, stomach, duodenum and indications for each

Answer 39

OGD: best visualization of mucosa; also allows for therapeutic intervention (e.g. banding varices, thermal therapy/clipping/injecting bleeding ulcers, and dilatation e.g. treatment of esophageal strictures) ■ consider barium swallow first if dysphagia, decreased level of consciousness (increases risk of aspiration), inability to cooperate (increases risk of pharyngeal trauma during intubation), possibility of fistulas ■ endotracheal intubation first if massive upper GI bleed, acidemia, or inability to protect airway

Question 40

Small bowel types of imaging

Answer 40

* most difficult to visualize, especially if mucosal detail is needed * CT enterography more accurate than small bowel follow through, but both have low sensitivity • MRI small bowel imaging increasingly available, especially useful if radiation exposure is an issue (e.g. young patient, multiple radiological images already done) ■ note: MRI enteroclysis: luminal contrast administered by nasojejunal tube to dilate the small bowel – disliked by both radiologist and patient, but may improve sensitivity * “double balloon” enteroscopy (enteroscope with proximal and distal balloons to propel endoscope into jejunum from mouth or into jejunum/ileum or into ileus from anus) may be most sensitive but currently available only in selected centres; technically demanding * wireless endoscopy capsule (26 x 11 mm capsule is swallowed, transmits images to a computer; contraindicated in bowel obstruction) is also accurate in diagnosis but unable to provide any therapeutic intervention

Question 41

Colon and Terminal ileum imaging options

Answer 41

* colonoscopy, with biopsy if required; contraindicated in perforation, acute diverticulitis, and severe colitis (increased risk of perforation) * CT colonography (“virtual colonoscopy”) more accurate in diagnosing diverticulosis, extrinsic pressure on colon (e.g. ovarian cancer compressing sigmoid colon), and fistulae; increasing evidence for use in colorectal cancer screening, especially for assessment of right side of colon in cases where colonoscopy is less sensitive. Most often used when optical endoscopic colonoscopy is a risk (e.g. frail elderly) or unsuccessful (e.g. stricture) * most often used when optical endoscopic colonoscopy s a risk (e.g. frail elderly) or unsuccessful (e.g. stricture)

Question 42

Pancreatic/Biliary Duct imaging options

Answer 42

* MRCP almost as sensitive as ERCP in determining if bile duct obstruction present, but less accurate in determining cause of obstruction (tumour, stone, stricture) * ERCP if therapeutic intervention likely to be required: strong suspicion of stone, obstruction requiring stenting, or if tissue sampling required