GI Tract Flashcards
The peritoneal cavity lies between what two layers of tissue?
Visceral and parietal peritoneum
The lesser omentum connects what two structures?
Stomach and liver
The greater omentum drapes over which structures and where is it attached?
Transverse colon, jejunum and ileum. Attaches to the greater curvature of the stomach and the posterior abdominal wall.
Omentum means what in Latin?
Apron
What are the two sections of the peritoneal cavity?
Greater sac and omental bursa
What double-fold of peritoneum connects the intestines to the posterior abdominal wall?
Mesentery
The transumbilical plane usually lies at around what vertebral level?
L3/L4, but can vary
The median plane lies between what two structures?
Xiphoid process and pubic symphysis
Point and name the 9 regions of the abdomen
Right hypochondrium, epigastric, left hypochondrium, left flank, umbilical, right flank, right groin, pubic, left groin
Describe the position of the transpyloric plane and why it is important
Horizontal plane half way between the jugular notch and pubic symphysis
Pylorus, pancreatic neck, colic flexures, origin of superior mesenteric artery and hepatic portal vein.
The bifurcation of the abdominal aorta occurs on what plane?
Supracristal plane (L4/5)
What are the two layers of superficial fascia in the abdomen?
Camper’s fascia and Scarpa’s fascia
What layer of fascia extends into the perineum and labia majora/penis and scrotum?
Scarpa’s fascia
What three muscle layers would you find in the lateral abdomen?
External oblique, internal oblique and transversus abdominis
What are the two deep layers of the abdominal fascia?
Transversalis and extraperitoneal fascia
What is the aponeurosis of the oblique muscles called?
Rectus sheath
Which part of the abdomen will you find the linea alba is created by an anterior AND posterior rectus sheath?
Upper 3/4
What is the linea alba?
Fibrous midline structure between the two rectus abdominis muscles, formed by the aponeurosis of the obliques (rectus sheath)
The inguinal ligament is continuous with what structure of the abdomen?
Aponeurosis of the external oblique
The quadratus lumborum and psoas major are separated from the paraspinal muscles by what layer of tissue?
Thoracolumbar fascia
The abdominal muscles are all supplied by the anterior rami of which spinal nerves?
T7-T12
The superior epigastric and subcostal arteries originate from which artery?
Subclavian
The femoral artery gives off what two branches to the abdomen?
Superficial epigastric and superficial circumflex ileac arteries
The inferior epigastric and deep circumflex ileac originate from which artery?
External ileac
Venous drainage from the abdomen ultimately drains into which two main veins?
Femoral or axillary veins
What skin and muscles are the only ones to be supplied by the posterior rami of spinal nerves?
Skin and deep muscles of the back
What dermatome lies roughly over the umbilicus?
T10
Which layer of the peritoneum will have well-localised pain and why?
Parietal layer because it is supplied by somatic fibres from spinal nerves
What nerves from the lumbar plexus supply the abdominal muscles?
Subcostal (T12), Iliohypogastric (L1), Ilioinguinal (L2), Genitofemoral (L1/2)
What type of incision is typically used for an open appendectomy?
Gridiron
What type of incision is typically used for an c-section?
Pfannenstiel
What type of incision is typically used for an open cholecystectomy?
Kocher’s
Which nerves may be damaged in surgical incisions, causing muscle weakness that can lead to a direct inguinal hernia?
Ileoinguinal and ileohypogastric nerves
Which type of hernia is more common?
Indirect hernia
Briefly describe the difference between an indirect and direct inguinal hernia
Indirect hernia protrude through the inguinal rings, lateral to the inferior epigastric vessels.
Direct hernias protrude through weaknesses in the abdominal wall at the conjoint tendon (medial to the inferior epigastric vessels)
What is the conjoint tendon?
The combined insertion of the transversus abdominis and internal oblique into the pubis
The superior surface of the tongue is covered in four types of lingual papillae, what are these called, what is their function and what innervates them?
Filiform papillae, general sensation, lingual branch of mandibular division of trigeminal (CN V3)
Fungiform and foliate papillae, taste buds, chorda tympani branch of facial nerve (CN VII)
Vallate papillae, larger taste buds (anterior to terminal sulcus), glossopharyngeal nerve (CN IX)
What nerve innervates the palatoglossus muscle?
Vagus (CN X)
What are sialolithiasis and what structure are they most associated with?
Calculi most common in the submandibular gland and duct.
Which phase of deglutition is voluntary?
Oral phase
What muscle relaxes to allow food into the oesophagus?
Cricopharyngeus
The elevation of the soft palate and closing of the epiglottis happen during which phase of deglutition?
Pharyngeal
What motion pushes the bolus of food down through the oesophagus?
Peristalsis
The oesophagus is divided into what three sections?
Cervical (C6-T1), thoracic (T1-10) and abdominal (T10-11).
The oesophageal hiatus is at what spinal level?
T10
The oesophageal arteries branch off what main artery?
Thoracic aorta
Describe the general innervation of the oesophagus
Parasympathetic- vagus (CN X)
Sympathetic- T6-9
Describe the general regions of the stomach
Cardia, fundus, body, pyloric antrum/canal/orifice.
The stomach receives blood supply from which branch of the abdominal aorta?
Coeliac trunk
Describe the lymph drainage from the stomach and the clinical importance of supraclavicular lymphadenopathy
Coeliac nodes -> cisterna chyli -> thoracic duct.
Virchow’s node- an enlarged left supraclavicular node, close to where the thoracic duct enters the systemic circulation. Can be a sign of metastatic gastric cancer.
Describe the venous drainage from the stomach
Splenic and superior mesenteric veins -> hepatic portal vein
What planes separate the nine regions of the abdomen?
Two midclavicular vertical planes. Two horizontal: subcostal and intertubercular planes.
Where is McBurney’s point?
1/3 of the way between the right ASIS and the umbilicus
Describe the layers of tissue in the abdomen, lateral to the rectus abdominis.
Skin, Camper’s fascia, Scarpa’s fascia, muscles/aponeurosis (rectus sheath), transversalis fascia, extraperitoneal fascia, parietal peritoneum
The superior epigastric artery is a branch of what artery?
Internal thoracic
The inferior epigastric artery is a branch of what artery?
External ileac
The duodenum curves around the head of which organ?
Pancreas
The oesophagus is lined with what type of epithelium?
Non-keratinising stratified squamous
The stomach is lined with what type of epithelium?
Simple columnar
What enzyme is important in liberating B12 from proteins?
Pepsinogen
What molecule helps with bicarbonate secretion, blood flow and cell membrane integrity in the stomach? What drug class can disrupt these processes?
Prostaglandins, NSAIDs
What is the function of bile?
Help absorb fat
H.Pylori will turn what colour under gram staining?
Red (negative)
Urea is a waste product of what process?
Protein lysis
How does H.Pylori affect the stomach lining?
Reduces thickness of mucosal layer, produces cytotoxins that weakness cellular junction and alters pH gradients.
What protects B12 from destruction by HCl in the stomach?
R protein released in saliva, binds to B12 and protects it
People with pernicious anaemia produce autoantibodies against what?
Intrinsic factor and parietal cells. Resulting in poor B12 absorption.
What are parietal cells?
Cells in the stomach lining that secrete HCl and intrinsic factor
What cells exist in the GI tract to lubricate the faecal material?
Goblet cells
What are enterocytes and what main structures in the GI tract do they line?
Columnar epithelial cells, specialised for absorption.
Small and large intestine
Draw the main branches of the arterial supply of the stomach
https://i.pinimg.com/originals/d5/a8/41/d5a8410c6619abaa2dd8d154d74461e0.png
What does the myenteric plexus mainly control?
Gastro-intestinal movements
What does the submucosal plexus mainly control?
Gastro-intestinal secretions and local blood flow
Describe the layers, from out to in, of a typical intestinal wall
Serosa, two layers of smooth muscle, submucosa, mucosa
Where in the layers of tissue does the myenteric plexus lie?
Between the longitudinal and circular smooth muscle layers
What are Brunner’s glands?
Groups of secreting and endocrine cells found predominantly in the first and second parts of the duodenum.
What sphincter lies between the small and large intestine?
Ileocecal
Where is the pyloric sphincter?
Between the stomach and duodenum
Where are Peyer’s patches found?
Ileum
What type of muscle exists in the first 1/3 of the oesophagus?
Skeletal
What type of muscle exists in the last 1/3 of the oesophagus?
Smooth
What condition is characterised by metaplasia of the oesophagus?
Barratt’s oesophagus
What cells exist in the isthmus, neck and base of a gastric pit?
Parietal cells
Endocrine cells secrete gastrin, what is this?
A hormone that stimulates gastric acid secretion from the parietal cells
What are the three sections of the small intestine?
Duodenum, jejunum and ileum
What structures are important in balancing the pH of the duodenum?
Brunner’s glands
What are the plicae circularis and where are they?
Transverse folds of mucosa.
Distal duodenum to the proximal ileus.
How can you remember the retroperitoneal structures?
SADPUCKER
S: suprarenal (adrenal) gland
A: aorta/IVC
D: duodenum (second, third and fourth parts)
P: pancreas (except tail)
U: ureters
C: colon (ascending and descending)
K: kidneys
E: (o)oesophagus
R: rectum
Do the kidneys have a visceral peritoneum?
No, it is retroperitoneal meaning it only has a parietal layer
What three ligaments make up the greater omentum?
Gastrophrenic, gastrosplenic and gastro colic
What two ligaments make up the lesser omentum?
Hepatogastric and hepatoduodenal
What is the portal triad and where is it?
Proper hepatic artery, common bile duct and hepatic portal vein.
Contained within the lesser omentum.
What are synonyms for the omental bursa?
Lesser sac or epiploic bursa
What lies anterior and posterior to the omental bursa?
Posterior- aorta and pancreas
Anterior- stomach and liver
What spaces lie laterally to the ascending and descending colon and connect the supracolic and infracolic compartments?
Paracolic gutters
What are the two compartments of the greater sac?
Supracolic and infracolic compartments
What space lies between the liver and diaphragm?
Subphrenic recess
What space lies between the liver and the kidney?
Hepatorenal recess
What structures make up the midgut?
Duodenum (3/4), jejunum, ileum, caecum, appendix, ascending colon and proximal 2/3 transverse colon.
What structures make up the hindgut?
Distal 1/3 transverse colon, descending colon, sigmoid colon, rectum and anal canal
What artery supplies the foregut, midgut and hindgut, respectively?
Foregut- coeliac trunk
Midgut- superior mesenteric,
Hindgut- inferior mesenteric
What part of the duodenum does the aorta and IVC run anterior to?
D3
There is no distinct boundary between the jejunum and ileum, how would you distinguish them in practice?
Proximal 2/5 jejunum and distal 3/5 ileum.
AND
Vessels in mesentery are different- jejunum has long vasa recta and less complex arterial arcades.
What is the falciform ligament and what is it continuous with at its free edge?
Ligament that divides the left and right lobes of the liver.
Continuous with the ligamentum teres which is a remnant of the left umbilical vein.
The liver receives blood from the GI tract via what vein?
Hepatic portal vein
The quadrate lobe of the liver can be found medial to what structure?
Gallbladder
The caudate lobe of the liver can be found medial to what structure?
IVC
What is the fissure called in the liver that contains the vessels?
Porta hepatis
Bile enters the gallbladder via where?
Cystic duct
What other duct joins the bile duct, what is the combination of the two called?
Main pancreatic duct.
Hepatopancreatic ampulla (ampulla of Vater)
What sphincter controls the flow of bile and pancreatic juice and where is it?
Sphincter of Oddi, D2 of duodenum.
What are the ligaments of the liver made from?
Simple squamous epithelium (mesothelium)
H Pylori converts what into what and why?
Urea into ammonia.
Ammonia neutralises stomach acid and makes it more hospitable for the bacteria.
What is a-amylase and where is it found?
Enzyme that breaks down starch into maltose and dextrin.
Found in saliva.
What is an SGLT1 and where are they?
Cotransporter, sodium moves down the concentration/electrochemical gradient into the cell and takes a molecule of glucose with it.
Small intestine.
Simply, why does pancreatic insufficiency lead to gastrointestinal problems?
Reduced pancreatic amylase and proteases, less catabolism of glucose and protein in the small intestine, large molecules are unable to be broken down, poor absorption.
What is a zymogen and why do they exist in the pancreas?
Inactive enzyme that can be activated by another enzyme.
To prevent autodigestion of the pancreas from its own enzymes.
The spleen is derived from which embryonic layer?
Mesoderm
What ligaments anchor the spleen in place?
Gastrosplenic and splenorenal ligaments
What is the flexure called where the ascending colon meets the transverse colon?
Hepatic flexure
What is the flexure called where the transverse colon meets the descending colon?
Splenic flexure
What are the teniae coli?
Thickened bands of smooth muscle on the surface of the large intestine.
This smooth muscle contracts and shortens the walls of the large intestine to propel faecal matter through the bowel.
What part of the bowel has omental appendices?
Large intestine/Colon
What region of the abdomen does the caecum sit?
RIF
Parasympathetic innervation of the internal anal sphincter has what effect?
Relaxation
Somatic innervation to the external anal sphincter comes from which nerve and spinal levels?
Pudendal nerve (S2-4)
What vessels are a common cause of haemorrhoids?
Internal rectal venous plexus
What is the pectinate line and why is it relevant?
Separates the embryonic hindgut from the ectoderm.
Below this line, the rectum is supplied by vessels of the pelvic region instead of the GI tract.
Epithelium also changes from non-keratinised to keratinised stratified squamous.
Which artery and vein lie directly posterior to the pancreatic neck and anterior to the distal duodenum?
Superior mesenteric
What vein does the splenic vein drain into?
Hepatic portal vein
What is Hirschsprung disease?
Congenital aganglionic megacolon. Segment of colon has no submucosal or myenteric plexus and thus fails to undergo coordinated peristaltic contraction.
What is the most common cause of bowel obstruction in children under 2 years old?
Intussuception
What is steatorrhea?
Excessive faecal fat and bulky, frothy, greasy, yellow or clay-coloured stools.
What are the four phases of nutrient absorption?
Intraluminal digestion, terminal digestion, transepithelial transport and lymphatic transport
What is gluten broken down into by luminal and brush border enzymes?
Gliadin
What cytokine is mentioned frequently as playing a role in the tissue destruction of Coeliac’s disease?
Interferon-gamma
What does the histological sample from the duodenum/jejunum of a person with Coeliac’s disease look like?
Crypt hyperplasia, villous atrophy and increased intraepithelial lymphocytes
What skin condition can develop with Coeliac’s disease?
dermatitis herpetiformis
What initial blood tests should be carried out in suspected Coeliac’s disease?
Anti-tTg and total IgA
Diverticula most commonly develop in which part of the colon and why?
Sigmoid, narrowest part of the colon and experiences highest pressures.
Describe the distribution and characteristics of ulcerative colitis
Affects mucosa and submucosa of the colon and rectum.
What are transmural inflammation and skip lesions what bowel disease are they most associated with?
Inflammation of all layers of the bowel wall.
A patchwork-like pattern of inflammation.
Chron’s disease
What is the most common cause of bacterial diarrhoea in the UK?
Campylobacter jejuni
What are the three major branches of the celiac artery?
Left gastric, splenic and common hepatic
The left gastro-omental artery follows which curvature of the stomach?
The greater curvature
The gastroduodenal artery branches off which artery?
Common hepatic
What vessel is most at risk of damage due to a duodenal ulcer?
Posterior branch of the superior pancreaticoduodenal artery
The right gastric artery branches off which artery?
Proper hepatic
Which artery supplies the gallbladder?
Cystic artery
What vertebral levels do the coeliac, superior mesenteric and inferior mesenteric arteries branch off the abdominal aorta?
T12, L1, L3
Which artery crosses over the left renal vein, causing “nutcracker syndrome”?
Superior mesenteric
Name some of the branches of the superior mesenteric artery that supply the ascending and transverse colon
Right, middle and ileocolic arteries
What artery ensures anastomoses between the arteries supplying the midgut and hindgut and is responsible for the vasa recta?
Marginal artery
The left colic artery branches off which artery?
Inferior mesenteric
What two main veins drain into the hepatic portal vein? What vertebral level does this happen?
Superior mesenteric and splenic
L1
The inferior mesenteric vein drains into which vein?
Splenic
How many hepatic segments are there?
8
Describe the venous drainage from the liver
Into the right, middle and left hepatic veins -> into the IVC
Oesophageal varices, anorectal varices and “Medusa’s head” of the umbilicus can be caused by what condition?
Portal hypertension- usually due to liver cirrhosis
What three sections are the pre-aortic lymph nodes divided into?
Coeliac, superior mesenteric and inferior mesenteric
What is the pathway of the pre-aortic lymph nodes into the systemic circulation?
Cisterna chyli -> thoracic duct -> left venous angle -> left brachiocephalic vein
Where is Virchow’s node (pronounced ‘virr-koff’) and what might lymphadenopathy here indicate?
Left supraclavicular, gastric cancer
Which ramus communicans are myelinated?
White ramus communicans
From the synapse in the sympathetic chain, where does a postganglionic neuron go?
Through the grey ramus communicans out into the dorsal or ventral root to the target organ
Preganglionic neurons for the GI tract viscera take what pathway from the CNS?
Straight through the sympathetic ganglion (without synapsing), down the splanchnic nerve to the target organ.
What neurons synapse in the paravertebral ganglia?
Preganglionic sympathetic neurons
The greater splanchnic nerves contain sympathetic preganglionic neurons from what vertebral levels and what general area do they supply?
T5-T9/10, foregut and midgut
The lesser splanchnic nerves contain sympathetic preganglionic neurons from what vertebral levels and what general area do they supply?
T9-T11, midgut
The lumbar splanchnic nerves contain sympathetic preganglionic neurons from what vertebral levels and what general area do they supply?
L1-L2/3, hindgut
What section of the autonomic nervous system to the pelvic splanchnic nerves belong to and what vertebral level do they come from?
Parasympathetic, S2-4
Parasympathetic innervation to the foregut and midgut comes from which nerve?
Vagus nerve (CNX)
Where is the superior hypogastric plexus found?
Anterior to the aortic bifurcation at L3/4
Where do visceral afferents have their cell bodies?
Dorsal root ganglia
Name the layers of the colon wall from in to out
Mucosa, muscularis mucosa, submucosa, muscularis propria, pericolic subcutaneous fat, visceral peritoneum
Colorectal cancer is caused by an accumulation of mutations in what genes?
Oncogenes and tumour suppressor genes
What is an oncogene?
A gene that has the potential to cause cancer
What is a tumour suppressor gene?
A gene that codes for proteins that suppress or regulate the cell cycle, preventing uncontrolled growth
Name two tumour suppressor genes
p53 and APC
Which location of colon cancer is more likely to cause obstruction?
Left-sided
What location of colon cancer is more likely to cause anaemia?
Right-sided
What type of cancer is colon cancer most likely to be?
Adenocarcinoma
