5.1 Digestive System Components Flashcards
Describe the superor/inferior boundaries of the anterolateral abdominal wall
Superior: xiphoid process + costal margins
Inferior: Iliac crest, down to ASIS, down to pubic symphysis
What’s the surface anatomical landmark used to palpate the fundus of the gallbladder?
Tip of the 9th costal cartilage, right side.
Describe the four lines that pass through the abdomen to form the 3x3 grid of sections
- Iliac crests (horiz)
- Subcostal border (horiz)
- Midclavicular lines (vert_
Recall the 9 regions of the anterolateral abdominal wall
Top: R/L hypochondriac + epigastric
Middle: R/L Lumbar + Umbilical
Lower: R/L Inguinal + Hypogastric
The transpyloric line is the midpoint between the…
Jugular notch and superior border of pubic symphysis
What GI structures does the transpyloric plane transect?
- Pylorus of stomach
- Fundus of gallbladder
- Neck of pancreas
- Renal hila
What characterises digestive accessory structures? Give 4 examples
- These are structures that aid in digestion, but are not part of the digestive tract itself.
- Examples include salivary glands, the gall bladder, the pancreas, and the liver
Why are accessory digestive organs important?
- Digestive efficiency (absorbable components)
- Storage of nutrients (e.g. liver)
- Homeostasis regulation (pancreas, bile composition)
Liver surface landmarks/quadrant
- Start at right costal margin, push upwards
- RUQ
Stomach surface landmarks/quadrant
- Start at left costal margin, extends centrally
- LUQ
Peritoneal position of liver
Intraperitoneal
Peritoneal position of gallbladder
Intraperitoneal
Peritoneal position of stomach
Intraperitoneal
Peritoneal position of the parts of the duodenum
First part is intra. Remaining three are retro.
(Starts in, then leaves the system)
Peritoneal position of ileum and jejunum
Entirely intraperitoneal
Peritoneal position of all parts of the colon
- Only the transverse is intraperitoneal
- The remaining (asc, desc, sigmoid, rectum) are retroperitoneal; after all, don’t want shit in the peritoneum
Peritoneal position of pancreas
- Tail is intra
- Rest is retro
(Tried to escape the system, but got it’s tail caught in the door)
Peritoneal position of spleen
- Intra (w/ the tail of the pancreas; makes sense)
Peritoneal position of kidneys/adrenals
Retroperitoneal
The peritoneum is a serous cavity. The tissue that lines serous cavities is called…
Mesothelium
Parietal vs visceral peritoneum
Parietal: adheres to abdominal wall
Visceral: adheres to organs
What is the mesothelial structure between the parietal and visceral peritoneum? What travels in it?
- Mesentery
- Double membrane; vessels, arteries, nerves, and lymphatics run through the middle
Too much peritoneal fluid is known as…
Ascites
What are the two sacs of the peritoneal cavity? Where are they? What separates them?
- Lesser sac (area deep to stomach)
- Greater sac (everything except area deep to stomach)
- Separated by epicloic window
What is the greater omentum comprised of? Where does it attach?
- Comprised of peritoneum; drapes down like apron
- Attaches to transverse colon and to stomach
What is the lesser omentum? Where does it run from? What are its two parts, and why is this important?
- Runs from duodenum/lesser curve of stomach to liver
- Parts are hepatogastric and hepatoduodenal
- Hepatoduodenal houses portal triad (hepatic portal vein, hepatic artery, bile duct)
What are the names of the vessels that run on the lesser and greater curvature of the stomach? How to remember this?
- Lesser: gastric arteries and veins (lesser = shorter name)
- Greater: gastro-omental arteries and veins (greater = longer name)
Organs are retroperitoneal if…
They only have peritoneum on their anterior side (if within the balloon, this is intra)
What is the level of the coeliac artery? What are the three branches?
- T12/L1
- Coeliacs are hippies; they hate SLS = Spleen (splenic artery), Liver (hepatic artery) and Stomach (left gastric artery)
Where does the left gastro-omental artery arise from?
End of splenic artery, near the tail of the pancreas (does a U turn)
Describe the branches of the common hepatic artery
- Gastroduodenal (r. gastro-omental, sup. pancreaticoduodenal)
- Hepatic proper (L/R hepatic, cystic)
- r. Gastric
Level of sup. mesenteric artery? What other arteries are at this level?
- L1 (very close to coeliac)
- Renal arteries also at this level
Describe the branches of the superior mesenteric artery
- Inf. pancreaticoduodenal
- Mesenteric branches to ileum and jejunum
- Ileococlic to coecum
- Right/middle colic to ascending and 2/3 of transverse colon
Level/branches of inf. mesenteric artery
- Level: L3
- Left colic to 1/3 transverse and descending colon
- Sigmoid branch to sigmoid colon
- Superior rectal artery to rectum (until pectinate line)
What are the two tributaries of the portal vein?
- Splenic vein
- Sup. mesenteric vein
Which veins can act as backups in the case of portal hTn? How does this explain caput medusae?
- Paraumbuillical (medusae)
- Colic
- Oesophageal
Describe the relationship between the three arms of the autonomic nervous system…
- 3 parts are para, sympa, and enteric
- Enteric is modulated by para and sympa
Describe the three groups of nerves that extrinsically innervate the gut
- Parasympathetic (vagus)
- Sympathetic (prevertebral ganglia)
- Sensory (dorsal root ganglia, sensory portion of vagus)
Where do the post-ganglionic sympathetic fibres that innervate the GI tract arise from? Name these regions
- Arise from prevertebral ganglia
- Sup. mesenteric, inf. mesenteric, coeliac, aorticorenal ganglia
Which arm of the autonomic nervous system can be found in splanchnic nerves (pre or post ganglionic)? What are the names of the four splanchnic nerves?
(Preganglionic sympathetic nerves)
- Greater splanchnic
- Lesser splanchnic
- Least splanchnic
- Lumbar splanchnic nerves
Ganglion vs plexus
Ganglion: group of neuronal cell bodies outside CNS
Plexus: cell bodies + surrounding nerve fibres
What are the two kinds of sympathetic neurons that act on the GI tract? What are their effects?
- Vasomotor (vasoconstriction)
- Visceromotor (reduced secretion, absorption, and motility {sphincters closed})
B-SAM, like beta SAM for MI meds
How does the sympathetic nervous system affect parasympathetic innervation of the GI tract, at a molecular level?
Can directly inhibit Ach release from parasympathetic neurons.
Describe afferent innervation of the GI tract
- Vagal innervation carried to the NTS
- Spinal afferents carry information via the DRG into the CNS (these are the only afferent supply to the lower GIT)
What are the effects of vagal efferents on the GI tract?
- Relaxation in the anal direction
- Contraction in the oral direction
Effect of sympa/parasympa on hepatic glucose control
Sympa: inc. gluconeogenesis, dec. glycogenesis
Parasympa: dec. gluconeogenesis, inc. glycogenesis
