anatomy of the GI tract Flashcards
what is the anterior, lateral, and posterior walls of the abdomen are composed of?
skin, subcutaneous tissue and muscles and their associated aponeuroses (flat tendons)
what are the functions of the abdominal wall?
- protect the abdominal viscera
- increase intra-abdominal pressure (e.g. for defecation and childbirth)
- maintain posture and move the trunk
what is the name of the serous membrane that lines the internal abdominal wall?
parietal peritoneum
how is the abdominal region be split into 9 parts?
four imaginary lines:
* the right and left midclavicular lines
* the subcostal line: underneath the most inferior part of the costal margin
* the intertubercular line: a horizontal line drawn through the tubercles of the right and left iliac crests
what are the names of the 9 regions in which the abdomen can be split into?
superior right to left: right hypochondrium
middle right to left: right flank, umbilical region, left flank
inferior right to left: right iliac fossa, suprapubic region, left iliac fossa
where is the transpyloric plane?
lies halfway between the superior border of the manubrium and the pubic symphysis; a horizontal line that passes through the tips of the right and left ninth costal cartilage
what does the transpyloric plane transect?
the pylorus of the stomach, the gallbladder, the pancreas and the hila of the kidneys
where is the transumbilical plane?
going across the belly button (umbilicus)
where is the intercristal plane?
a horizontal line drawn between the highest points of the right and left iliac crests used to guide procedures on the back (e.g. lumbar puncture)
where is McBurney’s point?
lies two thirds of the way along a line drawn from the umbilicus to the right anterior superior iliac spine, and is the surface marking of the base of the appendix
what are the four pairs of muscles in the anterolateral abdominal wall?
- external oblique (diagonally orientated fibres)
- internal oblique (diagonally orientated fibres)
- transversus abdominis (horizontally orientated fibres)
- rectus abdominis (rectus = straight).
how do the fibres of the external obliques lie?
run medially and inferiorly, towards the midline
how do the fibres of the internal obliques lie?
are orientated perpendicular to those of EO (they run medially and superiorly)
where does the transversus abdominis lie and how are the fibres orientated??
deep to the internal oblique, horizontally
what happens when the muscles of the abdomen contact?
increase intra-abdominal pressure
what are the lateral flexors of the lumbar spine?
oblique muscles
what do the muscles of the abdomen become anteriorly?
a flat tendon aponeurotic forming a ‘white line’ called linea alba
what is the rectus sheath and what is it formed from?
encloses the rectus abdominis, formed from the aponeuroses of abdominal muscles
what forms the anterior wall of the rectus sheath?
the anterior layer of the internal oblique aponeurosis and the externa oblique
what forms the posterior wall of the rectus sheath?
posterior layer of the IO aponeurosis and the transversus abdominis aponeurosis
what lies deep to the transverse abdominis?
transversalis fascia
what lies deep to the transversalis fascia?
parietal peritoneum
what arteries supply the anterolateral abdominal wall>
- musculophrenic artery, a branch of the internal thoracic
- superior epigastric artery, which is the continuation of the internal thoracic artery. It descends in the rectus sheath
- inferior epigastric artery, a branch of the external iliac artery. It ascends in the rectus sheath and anastomoses with the superior epigastric.
what is the innervation of the anterior abdominal wall?
● thoraco-abdominal nerves T7 – T11. These are essentially the continuation of the intercostal nerves T7 – T11. These somatic nerves contain sensory and motor fibres.
● the subcostal nerve – this originates from the T12 spinal nerve (so called because it runs along the inferior border of the 12th rib).
● iliohypogastric and ilioinguinal nerves – both are branches of the L1 spinal nerve.
what is the inguinal canal?
an oblique passageway through the muscles of the anterior abdominal wall and lies superior to the medial half of the inguinal ligament. it passes through each layer of the abdominal wall as it travels medially and inferiorly
what is found in the anterior border of the inguinal canal?
● external oblique aponeurosis
● laterally only: internal oblique aponeurosis
what is found in the posterior border of the inguinal canal?
● transversalis fascia
● medially only: medial fibres of the aponeuroses of the internal oblique and transversus abdominis (which are together known as the conjoint tendon).
what is found in the roof of the inguinal canal?
● transversalis fascia
● arching fibres of the internal oblique and transversus abdominis.
what is found in the floor of the inguinal canal?
● inguinal ligament (the lower border of the external oblique aponeurosis).
what is a hernia?
an abnormal protrusion of tissues or organs from one region into another through an opening or defect
what is the peritoneum?
is a serous membrane that lines the abdominal wall and covers the viscera within it
where is the parietal peritoneum?
lines the abdominal wall, can be seen with a naked eye
what does pain to the parietal peritoneum feel like?
sharp, severe, and well localised to the abdominal wall
where is visceral peritoneum found?
covers the abdominal viscera, cannot be seen with a naked eye
what does pain from the visceral peritoneum feel like?
usually dull and diffuse (i.e. it cannot be pinpointed to a specific location), severe
where is the peritoneal cavity, what lies within it and what is its purpose?
between the parietal and visceral peritoneum
a thin film of peritoneal fluid lies in the peritoneal cavity
It allows the viscera to slide freely alongside each other
what does it mean when an abdominal viscera is described as intraperitoneal?
almost completely covered by peritoneum e.g. the stomach
what does it mean when an abdominal viscera is described as retro peritoneal?
posterior to the peritoneum, hence only covered by peritoneum on their anterior surface e.g. the pancreas and abdominal aorta
what are mesenteries?
folds of peritoneum that contain fat and suspend the small intestine and parts of the large intestine from the posterior abdominal wall
what is contained within the mesenteries?
arteries that supply the intestine (from the abdominal aorta) and veins that drain the gut (tributaries of the portal venous system
what are the folds of the peritoneum called?
greater and lesser omenta
where is the greater omentum?
hangs from the greater curvature of the stomach and lies superficial to the small intestine
where is the lesser omentum?
connects the stomach and duodenum (the first part of the small intestine) to the liver
what is contained within the lesser omentum?
hepatic artery, the hepatic portal vein, and the bile duct (the ‘portal triad’) are embedded within its free edge
what are ligaments within the peritoneum?
folds of peritoneum that connect organs to each other or to the abdominal wall
what are some examples of ligaments within the peritoneum and what do they connect?
- falciform ligament, which connects the anterior surface of the liver to the anterior abdominal wall
- the coronary and triangular ligaments, which connect the superior surface of the liver to the diaphragm.
what are peritoneal folds?
raised from the internal aspect of the lower abdominal wall and are created by the structures they overlie, like carpet running over a cable
what is the peritoneal cavity divided into?
the greater and lesser sacs
where is the smaller lesser sac of the peritoneal cavity?
a space that lies posterior to the stomach and anterior to the pancreas
how do the lesser and greater sacs of the peritoneal cavity communicate?
via a passageway that lies posterior to the free edge of the lesser omentum, the epiploic foramen (also called the omental foramen).
where does the gastrointestinal system develop within an embryo?
embryonic gut tube
what is peritonitis?
infection and inflammation of the peritoneum
what are peritoneal adhesions?
pathological fibrous connections between the parietal and visceral peritoneum. when the peritoneum is irritated (e.g. by infection) it produces fibrin which causes the parietal and visceral peritoneum to adhere to each other. these connections may become fibrous.
what are the symptoms of peritoneal adhesions?
chronic abdominal pain and they increase the risk of volvulus (twisting) of the intestine, because it can no longer move freely
what is ascites
an increased volume of peritoneal fluid
where does the foregut extend to?
oesophagus to halfway along the duodenum
where does the midgut extend to?
2/3 transverse colon
where does the hindgut extend to?
upper anal canal
what happens to the abdominal aorta at L4/L5?
bifurcates to the left and right iliac arteries
where does the celiac trunk form from and what do they supply?
T12, supplies the foregut
where does the superior mesenteric form from and what do they supply?
L1, supplies midgut
where does the inferior mesenteric form from and what do they supply?
L3 supplies hindgut
what branches from the coeliac trunk and what do they supply?
- left gastric
- sphlenic artery
- common hepatic artery
what is the name of the area where the oesophagus passes through the diaphragm called?
oesophageal hiatus, at around T10
how is food in the stomach prevented from re-entering the oesophagus?
the muscle around the oesophageal hiatus acts as a sphincter
what supplies the distil oesophagus with blood?
branches from the left gastric artery
what drains the distil oesophagus of blood?
towards the azygos
vein via the oesophageal
veins and to the portal venous system (via the gastric veins)
what is the most superior part of the stomach called?
the fundus
what is the largest part of the stomach called?
the body
what is distil to the body of the stomach?
the pyloric part
what is the pyloric part broken up into?
the body leads to the pyloric antrum, which leads to pyloric canal that contains the pyloric sphincter
what are the borders of the stomach called?
the right border is called the lesser curvature whereas the left border is called the greater curvature
which quadrant does the stomach lie in?
upper left quadrant
what covers the stomach
visceral peritoneum
where is the lesser omentum found?
in between the liver and the stomach
where is the grater omentum found?
hangs from the greater curvature of the stomach
what supplies blood to the stomach?
arteries that branch from the coeliac trunk
what is the foregut composed of?
the stomach, first half of the duodenum, the liver, gallbladder and pancreas
what does the coeliac trunk divide into?
left gastric artery, the common hepatic artery, and the splenic artery
where does the right gastric artery arise from?
either the common hepatic artery or the hepatic artery proper
what do the right and left gastric arteries do?
run along the lesser curvature of the stomach and anastomose with each other
what arteries run along the greater curvature of the stomach and what do they do?
run along the greater curvature of the stomach and anastomose with each other
where does the left gastro-omental artery arise from?
splenic artery
where does the right gastro-omental artery arise from?
gastroduodenal artery, a branch of the common hepatic artery
where do the veins of the stomach empty into?
hepatic portal vein
what is the hepatic portal
vein?
a large vein that carries nutrient-rich venous blood from the GI tract to the liver
what provides parasympathetic innervation to the stomach?
the vagus nerve
what are examples of parasympathetic stimulation in the stomach?
peristalsis and gastric secretion