MORPHOLOGY OF THE GI TRACT Flashcards
what transports food from the pharynx to the stomach?
oesophagus
where does the oesophagus originate from?
inferior border of the cricoid cartilage C6
where does the oesophagus extend to?
cardiac orifice of the stomach T11
where does the oesophagus penetrate the diaphragm?
oesophageal hiatus in the central tendon at T10
how many sphincters present in the oesophagus?
two
names of sphincters and locations
upper oesophageal sphincter- at the junction between the pharynx and oesophagus
lower oesophageal sphincter- between the oesophagus and the stomach
what forms the upper sphincter?
cricopharyngeus muscle
where is the lower sphincter located? + spinal level
gastro-oesophageal junction at T11
what forms the lower sphincter?
oesophagus entering the stomach at an acute angle
walls of the intra abdominal section of the oesophagus are compressed
folds of mucosa occluding the lumen
right crus of diaphragm forming a pinch-cock effect
functions of the sphincters
prevent acid reflux
sections of the stomach
cardia- surrounds the superior opening of the stomach at T11
fundus- founded, gas filled portion superior to and to the left of the cardia
body- central large portion
pylorus- connects stomach to the duodenum
sections of the pyloris
pyloric antrum, pyloric canal and the pyloric sphincter
what does the pyloric sphincter demarcate + where?
transpyloric plane, L1
anatomical position of stomach
primarily in the epigastric and umbilical regions
anatomical relations
superior- oesophagus and left dome of the diaphragm
anterior- diaphragm, greater omentum, anterior abdominal wall, left lobe of liver, gall bladder
posterior- lesser sac, pancreas, left kidney, left adrenal gland, spleen, splenic artery, transverse mesocolon
function of pyloric sphincter
controls the exit of chyme from the stomach
how many layers in greater and lesser omenta?
two layers of double layered peritoneum, so 4 membrane layers
explain structure of greater omentum
hangs down from greater curvature of the stomach and folds back on itself where it attaches to the transverse colon
function of greater omentum
contains lymph nodes
lesser omentum structure
peritoneal fold arising from the lesser curvature and ascend to attach to the liver
function of lesser omentum
attach stomach and duodenum to the liver
what do the greater and lesser omentum divide the abdominal cavity into?
greater and lesser sac which communicate via the epiploic foramen
pyloric stenosis explained
narrowing of the opening from the stomach to the first part of the small intestine
occurs in babies
gastric ulceration explained
break in the inner lining of the stomach or the small intestine due to nSAIDS or bacteria
components of the small intestine
duodenum, ileum and jejunum
four parts of the duodenum
superior, descending, inferior and ascending
form the C shape
spinal level of superior section
L1
what is the superior section attached to?
liver via the hepatoduodenal ligament
descending structures
curves inferiorly around the head of the pancreas
marked by the major duodenal papilla
lies posteriorly to the transverse colon and anterior to the right kidney
inferior structures
travels laterally to the left
crosses over inferior vena cava and aorta
located inferiorly to the pancreas
posteriorly to the superior mesenteric artery and vein
ascencing structures
after the duodenum crosses the aorta it ascends and curves anteriorly to join the jejunum at the duodenojejunal flexure
is the duodenum intra or retroperitoneal?
retroperitoneal apart from the superior section
are the jejunum retro or intra peritoneal?
intraperitoneal
demarcation between the jejunum and ileum
there isn’t one
where does the ileum end?
ileocaecal junction
what does the major papilla demarcate?
change in blood supply from coeliac trunk to superior mesenteric artery (from foregut to midgut)
attachments
jejunum and ileum are connected to the posterior abdominal wall by mesentery
mesentery definition
double layer of peritoneum
four parts of the colon
ascending, transverse, descending and sigmoid
what is present before the ascending colon?
cecum
location of cecum
lies inferiorly to the ileocecal junction
is the cecum retro or intraperitoneal?
intraperitoneal
structure found on the cecum
appendix
appendix explained
narrow, blind ended tube attached to the cecum
highly variable positions
appendicitis explained
inflammation of the appendix
explain structure of colon
ascending colon- retroperitoneal. Meets right lobe of liver and turns right colic flexure/hepatic flexure
transverse colon starts, moves from right to left until left colic/splenic flexure- intraperitoneal
descending colon- moves inferiorly to pelvis- retroperitoneal (anterior to left kidney)
turns medially to form the sigmoid colon
next structure
rectum
where does the rectum begin?
S3
where does the rectum empty into?
anal canal
where is the anal canal located?
within the anal triangle of the perineum, between the right and left ischioanal fossae
how many sphincters in anus?
2
what sphincters + location? + type of muscle
internal anal sphincter- upper 2/3rds of anal canal- involuntary smooth muscle
external anal sphincter- lower 2/3rds- voluntary
