Anatomy (Gastrointestinal) Flashcards
What are the 4 functions of the upper GI tract?
Mastication (chewing), taste, deglutition (swallowing) and salivation.
What is the buccinator?
The muscle of the cheek, contraction causes food to move medially.
What of the 8 teeth are which types?
Incisor - 1+2. Canine - 3. Premolars - 4+5. Molars - 6, 7 and 8.
What bone is the head of the condylar process found on?
The mandible.
In the temperomandibular joint (TMJ), where is the head of the condylar process found?
In the mandibular fossa of the temporal bone.
What are the parts of the temporal bone involved in the TMJ?
Mandibular fossa and the articular tubercle.
What nerve supplies the muscle of mastication?
The mandibular division of the trigeminal nerve (CN V3).
What are the 4 muscles of mastication?
Close: temporalis, masseter and medial pterygoid. Open: lateral pterygoid.
What are the attachments of the temporalis muscle?
Coronoid process of mandible to temporal fossa.
What are the attachments of the masseter?
Angle of mandible to zygomatic arch.
What are the attachments of the medial pterygoid?
Angle of mandible (medial side) to pterygoid plates of sphenoid bone.
What are the attachments of the lateral pterygoid?
Condyle of mandible to pterygoid plates of sphenoid bone.
What are the 2 cavities of the TMJs divided by?
An articular disc.
What movements are the inferior and superior cavity for?
Inferior - rotation.
Superior - translation.
What type of nerve fibres does the mandibular division of the trigeminal nerve contain?
Sensory and motor.
What is the course of the mandibular division of the trigeminal nerve?
From pons through foramen ovale to muscle of mastication and sensory area.
What cranial nerve supplied the posterior third of the tongue?
CNIX (glossopharyngeal). Taste and general sensation.
What cranial nerves supply the anterior 2/3rds of the tongue?
Facial CNVII (taste) and V3 (general sensory).
What divides the anterior and posterior tongue?
The terminal sulcus.
What are the papillae with taste buds?
Foliate (folds), vallate (from V shape), fungiform (looks like fungus).
What are the papillae that sense touch and temperature?
Filiform papillae.
What is the course of the facial nerve and what does it supply?
From pontomedullary junction, travels through temporal bone via internal acoustic meatus then stylomastoid foramen. Taste anterior 2/3rds of tongue, muscles of facial expression, glands in floor of mouth.
What is the chorda tympani and what nerve does it connect to?
A branch of the facial nerve. Connects to the lingual nerve (CNV3).
What nerve types does the facial nerve supply the submandibular and sublingual salivary glands with?
Parasympathetic axons .
What cranial nerve supplies general sensation to the superior half of the oral cavity?
CN V2.
What cranial nerve supplies general sensation to the inferior half of the oral cavity?
CN V3.
What cranial nerve carries the sensory part of the gag reflex?
CN IX.
What cranial nerves carry the motor part of the gag reflex?
IX and X.
What happens to the pharynx in the gag reflex?
It is constricted.
What is the course of cranial nerve V2?
From pons through foramen rotundum to sensory area (mid-face).
What is the course of cranial nerve IX (glossopharyngeal)?
From medulla through jugular foramen to posterior wall of oropharynx (sensory), parotid gland (secretomotor) and posterior 1/3rd of tongue (sensation and taste).
What is the surface anatomy of the parotid and submandibular glands?
Parotid: inferoanterior to ear.
Submandibular: below posterior part of mandible.
Where do the ducts of the parotid and submandibular glands go?
Parotid: crosses face, secretes into mouth by upper 2nd molar.
Submandibular: enters floor of mouth and secretes via lingual caruncle.
Where is the sublingual gland and where does it secrete?
In floor of mouth, secretes via several ducts superiorly.
What cranial nerves supply each salivary gland?
Parotid: CNIX. Submandibular and sublingual: CNVII.
What are the names of the 4 pairs of extrinsic muscles of the tongue?
Palatoglossus, styloglossus, hyoglossus, genioglossus.
Where do the extrinsic muscles of the tongue attach other than the tongue?
Palatoglossus - soft palate.
Styloglossus - styloid process.
Hyoglossus - hyoid bone.
Genioglossus - mandible.
What cranial nerve are the tongue muscles innervated by?
CN XII (hypoglossal). Except palatoglossus.
Where are the intrinsic muscles of the tongue mainly located?
Dorsally/posteriorly.
What nerve fibres does the hypoglossal nerve have?
Motor only.
What is the course of the hypoglossal nerve?
From medulla through hypoglossal canal to extrinsic and instrinsic muscles of the tongue
What are the 2 layers of muscle of the pharynx?
An outer layer of circular muscle, an inner layer of longitudinal muscle.
What are the circular muscles of the pharynx called?
Superior, middle and inferior constrictor muscles of the pharynx.
What cranial nerve supplies the circular muscles of the pharynx?
CN X (vagus).
What nerves supply the longitudinal pharyngeal muscles?
CN X and IX.
What is the function of the longitudinal muscles of the pharynx specifically?
They elevate the larynx to close over the laryngeal inlet.
Describe the stages of swallowing.
- tongue pushes bolus of food towards oropharynx (voluntary).
- Soft palate and larynx elevated (involuntary).
- Circular layer of pharyngeal constrictor muscles contracts.
- Bolus of food enters oesophagus and travels inferiorly by peristalsis.
What study can be used to see the shape of the pharynx and oesophagus?
Barium swallow study.
Where does the oesophagus begin?
Inferior edge of cricopharyngeus muscle (vertebral level C6).
What nerve supply does the oesophagus get?
The oesophgeal plexus.
What nerve fibres does the oesophageal plexus contain?
Parasympathetic nerve fibres (vagal trunks) and sympathetic nerve fibres.
What do the nerve fibres in the oesophageal plexus do to change the rate of peristalsis?
They influence the enteric nervous system.
What are the 3 constrictions of the oesophagus?
Cervical constriction (cricopharyngeus muscle), thoracic constriction(s) (arch of aorta, left main bronchus) and diaphragmatic constriction (lower oesophageal sphincter).
Is the lower oesophageal sphincter physiological or anatomical?
Physiological.
What factors produce the sphincter effect?
- Contraction of diaphragm.
- Intrabdominal pressure slightly higher than intragastric pressure.
- Oblique angle at which oesophagus enters the cardia of stomach.
What is the function of the lower oesophageal sphincter?
Reduces occurrence of reflux.
What will reduce the effectiveness of the lower oesophageal sphincter?
A hiatus hernia.
Where is the lower oesophageal sphincter?
Immediately superior to gastro-oesophageal junction.
What is the Z-line?
An abrupt change in type of mucosa lining the wall.
What are rugae?
Folds in the stomach.
In what regions does the stomach lies when the patient is supine?
Left hypochondrium, epigastric and umbilical regions.
What are the 4 main parts of the stomach?
Cardia (just after oesophagus), fundus (superior part), body (most of it) and pyloric antrum (the part near the pylorus/pyloric sphincter).
What organs make up the foregut, midgut and hindgut?
Foregut: oesophagus to mid-duodenum, liver and gall-bladder, spleen, 1/2 of pancreas.
Midgut: mid-duodenum to proximal 2/3rds of transverse colon. 1/2 of pancreas.
Hindgut: distal 1/3rd of transverse colon to proximal 1/2 of anal canal.
What are the 2 transverse planes dividing up the abdominal regions?
Subcostal and transtubecular plane.
From superior to inferior, what are the central regions of the abdomen?
Epigastric, umbilical, pubic.
What are the left and right regions of the abdomen?
Hypochondrium, lumbar, inguinal.
In what condition is there guarding of the anterolateral abdominal wall muscles?
Peritonitis.
What does the peritoneum line?
The walls of the abdominopelvic cavity and organs.
What is the peritoneal cavity between?
The visceral and parietal layers.
What does the peritoneal vacity contain and why?
A small amount of lubricating fluid as the gut moves a lot.
What can blood, pus or faeces in the peritoneal cavity cause?
Peritonitis (severe, painful inflammation of the peritoneum).
What are the 3 classes of organs within the peritoneal cavity?
Intraperitoneal, retroperitoneal or organs with a mesentery (technically intraperitoneal).
How mobile are intraperitoneal organs?
Minimally mobile.
Where does the mesentery suspend an organ from and how mobile does this make them?
The posterior abdominal wall. Very mobile.
Where are retroperitoneal organs located and what surface does visceral peritoneum cover?
The retroperitoneum, its anterior surface.
What are the intraperitoneal organs?
Liver and gall bladder, stomach, spleen, parts of small intestine, transverse colon.
What are the retroperitoneal organs?
Kidneys, adrenal gland, pancreas, ascending colon, descending colon.
What are the 3 types of peritoneal formations?
- Mesentery.
- Omentum (greater and lesser).
- Peritoneal ligaments.
What are peritoneal ligaments?
Double layer of peritoneum connecting organs to one another or body wall.
What is contained in the core of the mesentery?
Blood and lymph vessels, nerve, lymph nodes and fat.
What are the 3 mesenteries?
- Mesentery proper (small intestine).
- Transverse and sigmoid mesocolon.
- Mesoappendix.
How many layers does the greater omentum have and what does it attach to?
4, attaches to greater curvature of the stomach to the transverse colon.
How many layers does the lesser omentum have and where does it attach?
2, runs between lesser curvature of stomach and duodenum to liver.
What divides the peritoneal cavity into a greater and lesser sac?
The omenta.
What is the gap between the 2 sacs called and where is it?
Omental foramen (foramen of Winslow). Free edge of the lesser omentum.
What are the 2 ligaments in the lesser omentum?
Hepatogastric ligament, hepatoduodenal ligament (free edge).
What are the ligaments that connect to the spleen?
Gastrosplenic ligament, splenorenal ligament.
What is the pouch in the male formed by the draping of peritoneum over the pelvic organs?
The rectovesical pouch.
What are the pouches in females?
Vesico-uterine pouch and the rector-uterine pouch (pouch of Douglas).
What is a common cause of ascites?
Liver disease (cirrhosis leads to portal hypertension, similar mechanism to pulmonary oedema).
What is the procedure called where ascitic fluid is drained by the peritoneum?
Paracentesis (abdominocentesis).
Where must the needle be places in paracentesis and why?
Lateral to the rectus sheath to avoid the inferior epigastric artery (ascends in anterior abdominal wall deep to rectus abdominus).
Where does the inferior epigastric artery arise from?
The external iliac artery medial to the deep inguinal ring.
What is often used to guide a paracentesis?
Ultrasound.
What are the 4 main questions to ask in abdominal pain?
- Location?
- Character?
- Timing?
- Pain referral pattern?
What is colicky pain and what does it indicate?
Pain which comes and goes, peristalsis comes in waves so may indicate a GI tract obstruction.
What nerves supply the organs within the abdominal cavity (including visceral peritoneum)?
Visceral afferents, the enteric nervous system, autonomic motor nerves (influence enteric nervous system).
What nerves supply the abdominal wall (skin through to parietal peritoneum)?
Somatic sensory nerves, somatic motor nerves and sympathetic nerve fibres.
At what vertebral levels do the sympathetics supplying the abdominal organs leave at?
T5-L2.
Where do the sympathetics supplying the abdominal organs synapse?
At the prevertebral ganaglia (anterior to the aorta at the exit points of the major branches of the abdominal aorta).
After the ganglia, where do the sympathetic nerves supplying the abdominal organs go?
Onto the surface of the arterial branches leaving the abdominal aorta.
What nerve plexuses are on the arterial branches of the abdominal aorta and what nerve fibres are found in them?
Sympathetics, parasympathetics and visceral afferents.
Where do sympathetic nerve fibres for the adrenal gland leave the spinal cord?
At T10-L1 vertebrae.
What is the path of a sympathetic nerve supplying the adrenal gland after leaving the spinal cord?
Enter abdominopelvic splanchnic nerves, don’t synapse at prevertebral ganglia, are carried with periarterial plexuses to the adrenal gland, synapse directly onto cells.
What part of the GI tract is parasympathetically innervated by the vagus nerve?
From start to distal end of transverse colon.
What parasympathetically innervates the rest of the GI tract?
The pelvic splanchnic nerves (S2, 3, 4).
Where does pain in the foregut, midgut and hindgut tend to be felt?
Foregut: epigastric.
Midgut: umbilical.
Hindgut: pubic.
What are the levels at which foregut, midgut and hindgut structures enter the spinal cord?
Foregut: T6-T9.
Midgut: T8-T12.
Hindgut: T10-L2.
Where may pain be felt other than the areas where the organs are (referred pain)?
In the dermatomes of the levels at which they enter the spinal cord.
What intercostal nerves become the thoracoabdominal nerves?
7th-11th intercostal nerves.
Between what muscle layers do the thoracoabdominal muscles travel?
The internal oblique and the transversus abdominus.
Other than the thoracoabdominal nerves, what are the other nerves that innervate the abdominal wall and where do they come from?
Subcostal nerve (T12 anterior ramus), iliohypogastric nerve (half of L1 anterior ramus), ilioinguinal nerve (other half of L1 anterior ramus).
Where is pain first felt in appendicitis and what type of pain?
The umbilical region, visceral.
When appendicitis worsens, where is pain then felt, what type of pain and why?
In the right iliac fossa, somatic pain, the parietal peritoneum becomes irritated which is part of the soma.
What is another name for jaundice?
Icterus.
What causes jaundice?
Increase in blood levels of bilirubin.
What process and organ produces bilirubin?
Break down of RBCs, mainly occurs in spleen.
Where is bile formed?
The liver.
What is the biliary tree?
A set of tubes connecting the liver to the 2nd part of the duodenum.
What is the function of bile in the small intestine?
Needed for the normal absorption of fats.
Where does the pancreas excrete digestive enzymes into?
The 2nd part of the duodenum.
What ribs protect the liver?
Ribs 7-11.
How many anatomical and functional lobes are there in the liver?
4 anatomical, 8 functional (related to vasculature and bile drainage).
What is the site of entrance for portal triad structures and what anatomical lobes is it between?
The site of entrance for portal triad structures. Inferior to caudate lobe, superior to quadrate lobe.
What are the 4 anatomical lobes and in what view can you see them all?
Right, left, caudate and quadrate. Posterior view.
Describe the 2 ligaments on the liver.
- Falciform (peritoneal formation).
2. Round ligament of liver (remnant of umbilical vein).
What is the orientation of the functional segments of the liver?
Clockwise orientation.
Describe the vessels that supply each lobe of the liver.
- Branch of hepatic artery.
- Branch of hepatic portal vein.
- Bile drainage (to bile duct).
- Venous drainage (to IVC).
Why is an increase in central venous pressure directed to the liver?
As the IVC and hepatic veins lack valves.
How many veins do the hepatic veins come together to joint before entering the IVC?
3 veins.
What ligament does the portal triad run within?
The hepatoduodenal ligament.
What makes up the portal triad (from anterior to posterior)?
- Bile duct.
- Hepatic artery proper.
- Hepatic portal vein.
What are the branches when the coeliac trunk bifurcates?
Splenic artery, left gastric artery, common hepatic artery.
What are the 2 left side branches of the coeliac trunk?
Splenic artery and left gastric artery.
What does the common hepatic artery bifurcate into?
The hepatic artery proper and the gastroduodenal artery.
What artery supplies the lesser curvature of the stomach and the lesser omentum?
The left and right gastric arteries (right comes from hepatic artery proper). They anastomose.
Describe the course of the splenic artery.
Tortuous.
Is the spleen intraperitoneal or retroperitoneal and what region does it lie in?
Intraperitoneal, the left hypochondrium.
What ribs protect the spleen?
Ribs 9-11.
What could pierce the spleen and what could this lead to?
A rib fracture, substantial internal bleeding.
Why do the spleen and liver move with respiration?
They are anatomically related to the diaphragm.
What arteries supply the greater curvature of the stomach?
The right (from gastto-duodenal artery) and left (from splenic proper) gastro-omental arteries. They anastomose together.
What minor arteries also supply the stomach?
Posterior gastric arteries, short gastric arteries.
What is another name for the gastro-omental arteries?
Gastro-epiploeic arteries.
What does the hepatic artery proper bifurcate into?
The right and left hepatic arteries.
What percentage of the blood the liver receives is from the hepatic arteries?
20-25%.
What is the dual blood supply of the liver.
The hepatic arteries and the hepatic portal vein.
What is another name for the hepatorenal recess?
Morison’s pouch.
What are the 2 recesses associated with the liver?
Hepatorenal recess and the sub-phrenic recess.
What sac are the recesses within?
The greater sac.
What can lead to a collection of pus in these recesses and what can this lead to?
Peritonitis, abscess formation.
Where will pus from an abscess in the sub-phrenic recess drain if a patient is bedridden?
The hepatorenal recess.
What 2 veins from the hepatic portal vein and what areas of the GI tract do they drain?
Splenic vein (foregut) and superior mesenteric vein (hindgut).
Where does the inferior mesenteric vein drain blood from and into?
From the hindgut, into the splenic vein.
Is the IVC intra or retroperitoneal?
Retro.
Describe where the gall bladder lies in relation to the duodenum and the liver.
Anterior to duodenum, posterior aspect of liver.
What is the function of the gallbladder?
Stores and concentrates bile in between meals.
How does bile flow into and out of the gall bladder?
Via the cystic duct.
What is the blood supply of the gall bladder and what artery is this a branch of?
Cystic artery, branch of right hepatic artery.
What forms the cystohepatic triangle (of Calot)?
The cystic artery at the top, the cystic duct and common hepatic duct at the sides.
What can cause gallbladder pain?
Inflammation of the gallbladder or cystic duct following irritation from or impaction of a gallstone.
As the gallbladder is a foregut organ, where do the visceral afferents enter the spinal cord?
Between T6-T9.
In what region will early gallbladder pain present?
In the epigastric region.
Where else can gallbladder pain present and why?
Right hypocondrium with possible referral to right shoulder. Result of anterior diaphragm irritation.
What is a surgical removal of the bladder called?
A cholecystectomy.
What structures need to be identified to perform a cholecystectomy and why may this be a problem?
Cystic duct and cystic artery. Variation can occur in both of these structures.
What part of the duodenum does the bile duct leak into?
2nd part (descending).
What is the arterial supply of the gall bladder?
The cystic artery.
What are the 4 parts of the duodenum?
- Superior (duodenal cap).
- Descending
- Horizontal
- Ascending
What parts of the duodenum are intraperitoneal and what parts are retroperitoneal?
Superior is intraperitoneal, the rest is retroperitoneal.
Where does the duodenum end?
The duodenojejunal flexure.
What effect does CKK have on bile release?
It causes bile to come down the biliary tree and into the duodenum.
Where does pain from a duodenal ulcer tend to present?
The epigastric region.
What are the parts of the pancreas?
Head (with uncinate process), neck, body and tail.
What does uncinate mean?
Horn.
Where does the tail of the spleen lie closely to?
The hilum of the spleen.
Is the stomach posterior or anterior to the pancreas?
Anterior.
What part of the autonomic nervous system innervates acinar cells in the pancreas?
Parasympathetic (like most glands).
Describe the path of the bile duct before it enters the duodenum.
Travels posterior to 1st part of duodenum -> into groove on posterior aspect of pancreas -> joins with main pancreatic duct to form the hepatopancreatic ampulla (of Vater) -> major duodenal papilla.
What are the 3 anatomical sphincters at the hepatopancreatic ampulla (of Vater)?
Bile duct sphincter, pancreatic duct sphincter, sphincter of Oddi.
Where is the sphincter of Oddi located?
At the major pancreatic ampulla.
If it was present, where would an accessory pancreatic duct drain into?
A minor duodenal papilla.
What is ERCP?
Endoscopic retrograde cholangiopancreatography.
Describe how ERCP is carried out.
Endoscope inserted through oral cavity into duodenum, cannula place into major duodenal papilla and radio-opaque dye injected back into biliary tree. Radiographic images are then taken.
Describe the shape of the cystic duct.
It is a spiral.
What 2 things can cause an obstruction of the biliary tree?
Gallstones, carcinoma at head of pancreas.
How can obstruction of the biliary tree cause jaundice?
Flow of bile back up to liver leads to overspill of its constituents into blood including bilirubin.
What is jaundice caused by obstruction of the biliary tree known as?
Post-hepatic jaundice (caused by extra-hepatic obstructive causes).
What 2 arteries anastomose around the pancreas and what branches of the abdominal aorta do they come from?
The superior pancreaticoduodenal artery (from coeliac trunk) and the inferior pancreaticoduodenal artery (from superior mesenteric artery).
Name a cause of pancreatitis.
Blockage of the ampulla by a gallstone (bile then diverted to pancreas causing irritation and inflammation).
Why can pancreatic pain present in both the epigastric and the umbilical region?
The pancreas is both a foregut and midgut organ.
Where can pancreatic pain radiate to?
Through to the patient’s back.
In acute pancreatitis caused by gallstone obstruction, what is an advanced complication?
Vascular haemorrhage.
What can vascular haemorrhage in acute pancreatitis present as?
Blood/fluid accumulation in the retroperitoneal space. Grey-Turner’s sign is blood in the right or left flanks, Cullen’s sign is around the umbilicus via falciform ligament.
What parts of the duodenum are foregut organs?
1st and 2nd parts.
Where does the jejunum begin?
At the duodenaljejunal flexure.
Where does the ileum end?
The ileocaecal junction.
What is the difference in colour between the duodenum and ileum?
Jejunum is deep red, ileum is lighter pink (due to jejunum having better blood supply).
What is the differences in the jejnunal and ileal wall?
Jejunu is thicker and heavy, ileum is thinner and lighter.
What is the difference in the vasculature of the jejunum and ileum?
Jejunum is more vascular than the jejunum.
What is the difference between the mesenteric fat of the jejunum and ileum?
Jejunum has less, ileum has more.
What are the differences between the folds of the jejunum and ileum?
Jejunum has large, tall and closely packed folds. Ileum has low and sparse folds (absent distally).
Are Peyer’s patches present in the duodenum or the ileum?
The ileum.
What arteries supply the duodenum and ileum?
Jejunal and ileal arteries from the superior mesenteric artery.
What is the venous drainage of the jejunum and ileum?
Jejunal and ileal veins.
What is the path of the superior mesenteric artery?
Leaves aorta at L1 -> posterior to neck of pancreas -> inferiorly anterior to uncinate process of pancreas to enter the mesentery proper.
What 3 structures are located at L1 level and what is this plane called?
Superior mesenteric artery, neck of pancreas and pylorus. Trans-pyloric plane.
Where do chylomicrons drain from the intestinal cells?
Lacteals (lymphatic vessels).
What are the 4 main groups of lymph nodes draining the abdominal organs and what organs do they drain?
- Coeliac (foregut).
- Superior mesenteric (midgut).
- Inferior mesenteric (hindgut).
- Lumbar (kidneys, posterior abdominal wall, pelvis and lower limbs).
What is the large intestine made up of?
Colon (caecum, appendix, ascending, transverse, descending, sigmoid), rectum, anal canal, anus.
What are the 3 functions of the large intestine?
Defence (commensal bacteria), absorption (H20 and electrolytes), excretion (formed stool).
What parts of the colon are intraperitoneal?
Caecum, transverse (own mesentery), sigmoid (own mesentery).
Where are the 2 paracolic gutters?
Between lateral edge of ascending and descending colon and abdominal wall.
What sac of the peritoneal cavity are the paracolic gutters located in?
Greater sac.
What are the 3 distinguishing features of the colon?
Omental appendices (small fatty projections only found on colon), teniae coli (longitudinal muscles), haustra (folds formed by tonic contractions of teniae coli).
Where is the appendix most commonly found (64% of the time)?
Retrocaecal.
What surrounds the ileocaecal orifice?
Upper and lower lips.
Describe the ileocaecal orifice and valve.
Orifice invaginates slightly and has small amount of smooth muscle to form the valve (is not great at stopping stool moving back through).
What is the name of the mesentery of the sigmoid colon?
The sigmoid mesocolon.
What is the downside of the sigmoid colon having a good range of movement?
It is at risk of twisting around itself (sigmoid volvulus).
What does sigmoid volvulus result in?
Bowel obstruction and infarction if untreated.
At what vertebral levels do the coeliac trunk, the SMA and the IMA branch from the abdominal aorta?
Coeliac - T12, SMA - L1, LMA - L3.
What do the lateral branches of the abdominal aorta supply?
Kidneys/adrenal glands (renal artery), gonads (gonadal artery), posterolateral body wall (lumbar arteries).
At what levels do the renal and gonadal arteries leave the abdominal aorta?
Renal - L1. Gonadal - L2.
Where does the aorta bifurcate into the iliacs and what do they then bifurcate into?
L4 (top of iliac crest), internal and external iliacs.
What are the branches of the superior mesenteric artery supplying the intestines from proximal to distal?
Jejunal and ileal, appendicular, ileocolic (terminal ileum and caecum), right colic, middle colic (transverse colon).
What are the differences between the jejunal and ileal arteries?
Jejunal - longer vasa rectae (straight arteries), larger and fewer arcades (arches). Ileum - shorter vasa rectae, smaller and many arcades (usually piled up).
What are the branches of the inferior mesenteric artery from proximal to distal?
Left colic (supplies descending colon), sigmoid arteries (multiple), superior rectal artery.
What is the marginal artery of drummond?
An arterial anastomoses betweem the branches of SMA and IMA.
What does the ability of the anastomoses between the SMA and IMA to prevent ischaemia depend on?
The health of the anastomotic vessels and the speed at which obstruction of a vessel occurs.
Where does the blood supply by the superior rectal artery stop?
Halfway down the anal canal (the pectinate line).
What supplies the remained of the GI tract?
The internal iliac artery (anastomoses between vessels of superior rectal and internal iliac).
Are there valves in the veins where there are portal-systemic anastomoses?
No.
Where are the 3 clinically important sites of portal-systemic anastomoses?
- Skin around umbilicus.
- Distal end of oesophagous.
- Rectum/anal canal.
What are the veins that are connected around the skin of the umbilicus and what systems does each drain into?
Para-umbilical veins (to hepatic portal vein along round ligament), epigastric veins (caval system).
What parts of the distal end of the oesophagus drain into the portal and systemic venous systems?
Inferior to portal, superior to systemic.
What parts of the rectal/anal canal drain into where?
Rectum and superior anal canal - inferior mesenteric veins. Inferior - internal iliacs.
Where do the superior, middle and inferior rectal veins drain into?
Superior - inferior mesenteric veins. Middle and inferior - internal iliac veins.
What are the 3 vascular clinical presentations of portal hypertension?
- Iesophageal varices.
- Caput medusae (dilated para-umbilical and epigastric veins).
- Rectal varices (internal or external).
