Gastrointestinal Anatomy Flashcards
What separates abdominal cavity from thorax?
Diaphragm
GI Tract organs found in abdominal cavity
Stomach, small intestine, large intestine
Hepatobiliary system organs found in the abdominal cavity
liver and gallbladder
Urinary system organs found in the abdominal cavity
kidneys and ureters
Endocrine system organs found in abdominal cavity
pancreas and adrenal glands
What are the abdominal walls composed of?
Anterior, lateral and posterior walls compose skin, subcutaneous tissue and muscles and associated aponeuroses (flat tendons)
3 abdominal wall functions
protect abdominal viscera
Increase intra-abdominal pressure (for defecation and childbirth)
Maintain posture and move trunk
Internal abdominal wall lined with…
Parietal peritoneum (serous membrane like the internal thoracic wall is lined with parietal pleura)
How are the 4 quadrants named and divided?
RUQ, RLQ, LUQ, LLQ
Vertically down midline of lower sternum, umbilicus and pubic symphysis
Horizontally at the level of the umbilicus
How are the 9 regions divided horizontally?
-Subcostal line (through
inferior most parts of L
and R costal margins
through 10th costal
cartilage)
-Intertubercular line (drawn through the tubercles of the R and L iliac crests and the body of L5)
How are the 9 regions divided vertically?
R and L midclavicular lines which extend vertically from the midclavicular point to the mid-inguinal point
What is the mid-inguinal point?
Halfway between anterior superior iliac spine and the pubic tubercle
Name the 9 regions of the abdominal cavity
(First left to right then top to bottom)
Left hypochondriac region
Epigastric region
Right hypochondriac region
Left lumbar region
Umbilical region
Right lumbar region
Left iliac fossa (region)
Hypogastric region
Right iliac fossa (region)
Where is the transumbilical plane?
Transverse plane at L3 but can vary dependent on amount of subcutaneous fat in an individual
The 4 muscle pairs that comprise the anterolateral abdominal wall
External obliques (diagonally orientated fibres)
Internal oblique (diagonally orientated fibres)
Transversus abdominis (horizontally orientated fibres)
Rectus abdominis (rectus = stright, vertical)
Rectus abdominis position and attachments (this is the 6 pack, the other 3 abdomen muscles are lateral to it)
R and L rectus abdominis muscles lie either side of midline attaching to sternum and costal margin superiorly and pubis* inferiorly
It’s surrounded by an aponeurotic rectus sheath
External oblique (EO) fibre orientation
Medially and inferiorly towards the midline
Internal Oblique (IO) fibre orientation (lies deep to EO)
Medially and superiorly towards midline (perpendicular to EO)
Transverse abdominis fibre orientation (lies deep to IO)
Horizontal orientation
Aponeurosis is…
Flat tendons found associated with the abdominal muscles (aponeuroses of the rectus abdominis form the rectus sheath)
Linea alba
Tough midline seam formed by fusion of aponeuroses on both sides of the rectus abdominis
Rectus abdominis lies within rectus sheath. Rectus sheath anterior and posterior walls are formed by…
Aponeuroses of EO, IO and transversus abdominis
-Approaching the
midline, aponeurosis of
the IO splits into
anterior and posterior
layers
-EO aponeurosis and
anterior layer of IO
aponeurosis form
anterior wall of rectus
sheath
-Posterior layer of IO
aponeurosis and
transversus abdominis
aponeurosis form
posterior wall of rectus
sheath
Transversalis fascia lies ____ to transversus abdominis. Deep to the fascia lies _____
Deep
The Parietal Peritoneum
Most inferior part of EO aponeurosis is attached to _____ laterally and _____ medially forming the _____
Anterior superior iliac spine
Pubic tubercle
Inguinal ligament
3 arteries that supply anterolateral abdominal wall (these vessels are accompanied by deep veins and an extensive network of superficial veins is found in anterolateral abdominal wall)
Musculophrenic artery (branch of internal thoracic)
Superior epigastric artery (continuation of internal thoracic and descends through rectus sheath)
Inferior epigastric artery (branch of external iliac artery. Ascends in rectus sheath and anastomoses with superior epigastric)
Muscles/skin of anterolateral abdominal wall innervated by…
-Thoraco-abdominal nerves (T7-T11) (somatic nerves containing sensory and motor fibres)
-Subcostal nerve (T12 so called as it runs along inferior border of 12th rib)
-Iliohypogastric and ilioguinal nerves - both L1
Parietal Peritoneum (lines abdominal wall) innervation
Innervated by somatic nerves that supply overlying muscles and skin of abdominal wall (so pain is usually sharp, severe and well localised)
Visceral Peritoneum (covers abdominal viscera) innervation
Innervated by visceral sensory nerves which convey painful sensations back to CNS along path of sympathetic nerves that innervate the organ it covers (pain usually dull, diffuse, can’t be pinpointed)
Why is pain from visceral peritoneum referred but pain from parietal is not?
Visceral afferents enter spinal cord at T5-T9 same point as nerves from others parts of abdomen so pain often felt in those sections instead
What is found between the parietal and visceral peritoneum?
The peritoneal cavity containing a thin film of peritoneal fluid allowing viscera to slide freely alongside each other
Abdominal viscera are intraperitoneal if they’re…
Almost completely covered by peritoneum (stomach)
Abdominal viscera are retroperitoneal if they’re…
Posterior to peritoneum so only covered on their anterior surface (pancreas and abdominal aorta)
Secondarily retroperitoneal organs
Originally intraperitoneal in early development but came to be “stuck down” onto the posterior abdominal wall
What are mesenteries?
Folds of peritoneum that contain fat and suspend small intestine and parts of large intestine from posterior abdominal wall. Arteries supplying intestine (from abdominal aorta) and veins that drain gut (tributaries of portal venous system) are embedded in tributaries
Greater omentum
Mesentery, usually fatty, hanging form greater curvature of stomach and lies superficial to small intestine
Lesser omentum
Mesentery, usually fatty, that connects stomach and duodenum to the liver
The portal triad (hepatic artery, hepatic portal vein and bile duct) are embedded within its free edge
Falciform ligament
Connects anterior surface of liver to abdominal wall
What connects the superior surface of the liver to the diaphragm?
The coronary and triangular ligaments
How does the shape of peritoneal folds arise?
They’re raised from the internal aspect of the lower abdominal wall and created by the structures they overlie (like a carpet running over cable)
What is the median umbilical fold?(peritoneal fold)
Lies on midline and is the remnant of the urachus (embryological structure connecting bladder to umbilicus)
What folds are lateral to median umbilical fold?
The medial umbilical folds which are remnants of paired umbilical arteries (return venous blood to placenta in foetal life)
What are folds are lateral to the medial umbilical folds? What is contained within them?
Lateral umbilical folds (inferior epigastric arteries lie deep to these peritoneal folds which supply anterior abdominal wall)
Peritoneal cavity is divided into 2 regions of unequal size called…
Lesser Sac - Space that lies posterior to stomach and anterior to pancreas
Greater Sac - Remaining part of cavity
How do the greater and lesser sacs of peritoneal cavity communicate?
Through a passageway posterior to the free edge of the greater omentum called the epiploic foramen
GI system develops from the…
Embryonic gut tube which lies in the midline and is suspended from the posterior abdominal wall by the dorsal mesentery
What connects stomach to anterior abdominal wall?
Ventral mesentery
The liver develops within the _____ _____
As it develops, the anterior part of the ___ ___ becomes the ____ ___ and the posterior part becomes the ___ ___
Ventral Mesentery
Ventral Mesentery
Falciform Ligament
Lesser Omentum
Oesophagus passes through oseophageal hiatus in diaphragm at the level of…
Role of Muscles around the hiatus?
How long is abdominal segment of oesophagus?
T10
Act as a sphincter preventing reflux of stomach contents into oesophagus
Less than 2cm
Blood supply of distal oesophagus?
Branches of L gastric artery
Venous drainage of distal oesophagus? (site of portosystemic anastomoses)
-Systemic system of veins (via oesophageal veins draining into azygos veins)
-Portal venous system (left gastric veins)
Stomach breaks down food into…
Chyme
What is contained within the fundus of the stomach?
Usually filled with gas as it’s superior to level of entry of oesophagus
Where is the pyloric sphincter?
What is it’s role?
Pyloric Canal
Formed of circular smooth muscle and regulates passage of chyme into duodenum
Stomach surface covered in…
Visceral peritoneum