Anatomy: Oesophagus to Mouth Flashcards
What are the 9 regions of the abdomen?
Left hypochondrium Right hypochondrium Epigastric region Left lumbar Right lumbar Umbilical region Left iliac Right iliac Hypogastric
Which organ would you find in the right hypochondrium?
Liver
From superficial to deep, what are the three anterolateral muscle layers that comprise the anterior abdominal wall?
External oblique, internal oblique and transversus abdominis muscle
What is the external oblique? What happens at its inferior border?
External oblique has fibres which run in an anterior inferior direction (as if you were putting your hands in your pockets).
Look at the inferior border of external oblique. It forms the inguinal ligament between ASIS and the pubic tubercle.
What is the internal oblique?
Internal oblique has fibres which run in an posterior inferior direction (the opposite to external oblique).
What is the transversus abdominis?
Transversus abdominis has fibres which run in a transverse direction.
What is the rectus abdominis?
There is a FOURTH anterior vertical muscle: rectus abdominis.
Bands of tendons – tendinous intersections – divide the rectus abdominis muscle horizontally to give the characteristic ‘six pack’. The vertical midline tendinous intersection is called the linea alba (‘white line).
What is the inguinal ligament?
The free inferior border of external oblique runs between ASIS and the pubic tubercle. This border is called the inguinal ligament.
What is the linea alba?
The central tendinous band in the rectus abdominis is called the linea alba
Where does food reach after the oesophagus?
The food then reaches the stomach, which secretes highly acidic contents and has a variety of different muscular layers to help to churn contents and pass them through to the next part of the GI tract.
What does the stomach feed into? What does this allow for?
The stomach feeds into the pyloric sphincter which opens to allow contents through into the small intestine.
What are the three parts of the intestine?
The small intestine has 3 main parts:
- Duodenum
- Jejenum
- Ileum
Where does the ileum feed into the colon?
The ileum then feeds into the first part of the large intestine at the ileocaecal juntion.
What are the 9 parts of the colon?
- Caecum (note the small extension coming off of the caecum, this is the appendix!)
- Ascending colon
- Hepatic flexure
- Transverse colon
- Splenic flexure
- Descending colon
- Sigmoid colon
- Rectum
- Anal canal
What anatomical relationship does the pancreas have to the stomach?
Posterior
What anatomical relationship does the greater omentum have to the stomach?
Inferior
The greater omentum hangs down from the greater curvature of the stomach to lie anterior to the small intestines.
What artery supplies the foregut?
Coeliac trunk
What artery supplies the midgut?
Superior mesenteric artery
What artery supplies the foregut?
Inferior mesenteric artery
At which vertebral level does the oesophagus pass through the diaphragm?
T10
What region is the stomach found in? What is its function?
It is a muscular sac which acts to churn food and mix it with stomach acid.
What are the parts of the stomach from top to bottom?
Fundus
Body of stomach
Antrum
Phyloric sphincter (a thick smooth muscle sphincter which guards the entrance to the duodenum)
Lesser curvature (top curve of stomach shape)
Greater curvature (bottom curve)
In a normal chest x-ray which part of the stomach can be visualised?
Fundus
An air bubble within the fundus of the stomach can often be seen underneath the left hemi-diaphragm.
What are the features of the duodenum?
The duodenum is largely retroperitoneal, and found on the posterior abdominal wall. It is a short c-shaped section of small intestine which curls around the head of the pancreas.
Both the pancreas and bile ducts drain into the duodenum.
What are the 4 part of the duodenum?
Superior
Descending region (has the bile ducts and pancreatic ducts draining into it - end of the foregut)
Horizontal
Ascending
Which structures drain their contents into the duodenum?
Stomach
Gall bladder
Pancreas
Which structure helps to prevent heartburn?
Lower oesophageal sphincter
Heartburn is experienced when stomach acid enters the lower part of the oesophagus.
The lower oesophageal sphincter is a physiological sphincter, not an anatomical sphincter. Which anatomical structures help to reinforce this sphincter?
Diaphragm
The oesophagus passes through the diaphragm at the level of T10, before terminating in the stomach. The diaphragm is a muscular sheet and its contraction helps to reinforce the LOS.
If pressure within the abdomen increased which part of the stomach would be most likely to be pushed superiorly through the oesophageal hiatus?
Fundus
Decreased abdominal muscle tone and increased pressure within the abdominal cavity could lead to the development of a hiatal hernia.
Thus, people who are obese and women who are pregnant may be at an increased risk for developing a hiatal hernia.
A hiatus hernia is when the fundus of the stomach passes through the oesophageal hiatus so stomach acid can pass into the oesophagus.
Which organs are located in the foregut?
Liver
Stomach
Which organs are located in the midgut?
Jejunum
Ileum
Appendix
Ascending colon
Which organs are located in the hindgut?
Descending colon
Sigmoid colon
Rectum
Which arterial branch from the aorta supplies the midgut?
Superior mesenteric artery
What is the main function of the small intestine? What features allow for this? Which part of the small intestine is best for its function?
The main function of the small intestine is absorption of the products of digestion. To do this it has a very large surface area.
The jejunum is the site of maximum absorption. The ileum has less absorption occurring, but features oval groups of lymphoid tissue, called peyers patches in its wall.
What are the endoscopic features of each part of the small intestine?
Duodenum has neither many plicae circulares or Peyer’s Patches
Jejunum has numerous plicae circulares (inwards folds of mucosal lining)
Ileum has few plicae circulares but does have Peyer’s Patches
What is the appendix and where is it found?
The appendix is a blind ended pouch which is attached to the caecum.
Its position is variable but it is usually found behind the caecum, in a retrocaecal position.
What is the caecum?
The caecum is the first part of the colon and is a dilated region of the colon.
What is the ascending colon?
The ascending colon runs along the right border of the abdomen. It is fixed in place.
What is the hepatic flexure?
The ascending colon abruptly turns to become the transverse colon.
This angulation is called the hepatic flexure as it is close to the liver.
What is the transverse colon? What is surprising about it?
The transverse colon is the end of the midgut and the beginning of the hindgut.
This part of the colon is surprisingly mobile.
What is the splenic flexure?
The transverse colon abruptly turns to become the descending colon.
This angulation is called the splenic flexure as it is close to the spleen.
What is the descending colon?
The descending colon runs along the left border of the abdomen. It is fixed in place.
What is the sigmoid colon?
The sigmoid colon is S-shaped
What is the rectum?
The rectum is located within the pelvis
What is the anal canal?
The anal canal is the terminal part of the gut. It is surrounded by the internal and external anal sphincters.
How would you describe the usual position of the appendix?
Retrocaecal
The position of the appendix varies, but it is usually found behind the caecum (the diagram above has brought it inferior to show the structure).
Which branch of the abdominal aorta supplies the hindgut?
Inferior mesenteric artery
Where does the hindgut begin and where does it end?
The hindgut begins 2/3 of the way along the transverse colon. It ends at the anus.
The nerve supply to the gut is both sympathetic and parasympathetic. Which nerve provides parasympathetic innervation to the foregut and the midgut?
The Vagus nerve provides parasympathetic innervation to the midgut and the hindgut.
Which nerve provides parasympathetic innervation to the hindgut?
Pelvic sphlanchic nerves (S2-S4)
What are the features of the sigmoid colon?
The descending colon is retroperitoneal and runs along the left side of the abdomen.
Where is the sigmoid colon located?
The sigmoid colon starts anterior to the pelvic brim. Below it is continuous with the rectum, which commences anterior to the 3rd sacral vertebra. It is an S-shaped region of the colon.
Is the sigmoid colon intraperitoneal or retroperitoneal?
Intraperitoneal
What are the features of the rectum?
The rectum follows the curve of the sacrum and coccyx, and ends at the tip of the coccyx by piercing the pelvic diaphragm and becoming continuous with the anal canal. The puborectalis portion of the levator ani muscle forms a sling at the junction of the rectum with the anal canal and pulls this part of the bowel forward producing the anorectal angle.
The rectum has a dense blood supply.
Which artery does the superior rectal artery branch from?
Inferior mesenteric artery
Which artery does the middle rectal artery branch from?
Internal iliac artery
Which artery does the inferior rectal artery branch from?
Pudendal artery
Which rectal veins drain to which main veins? What does this mean?
The venous drainage follows the same pattern as the arteries:
Superior rectal vein -> Inferior mesenteric vein
Middle rectal vein -> Internal iliac vein
Inferior rectal vein -> Pudendal vein
The rectum and anus are therefore a site of portosystemic anastomoses.
How many plexi are there in the anal canal?
Note there are 2 venous plexi in the anal canal, and internal plexus and an external plexus (bulges on the diagram).
What is the peritoneum? How can it be conceptualised? How is it divided?
The peritoneum is the serous membrane lining the abdomen and covering its organs.
It can be conceptualised by imagining a fist in the side of a balloon. The balloon covers the fist, and then folds back to be continuous with the rest of the balloon.
It can be divided into a parietal layer which lines the abdominal wall and the visceral layer which covers the organs.
Why is the peritoneum more confusing than other pleura?
The peritoneum is substantially more confusing than the similar pleura in the thorax, due to the number of organs in the abdomen.
The organs within the abdomen have differing relationships with the peritoneum.
Some are plastered to the posterior abdominal wall by the peritonuem, these organs are described as retroperitoneal.
Other organs are surrounded by peritoneum, these are described as intraperitoneal.
Which organs are intraperitoneal?
Transverse colon Stomach Ileum Jejunum Spleen Liver Caecum
Which organs are retroperitoneal?
Descending colon Aorta Ureter Kidneys Inferior vena cava Ascending colon
Which organs are both retroperitoneal and intraperitoneal?
Duodenum
Pancreas
What are the different folds of the peritoneum?
Falciform ligament
Greater omentum
Transverse mesocolon
The mesentary
What organs is the lesser omentum associated with?
Liver to the lesser curvature of the stomach
What organs is the greater omentum associated with?
Greater curvature of the stomach
What organs is the mesentary associated with?
Jejunum and ileum
What organs is the mesocolon associated with?
Transverse colon
What organs is the falciform ligament associated with?
Dividing the liver into left and right lobes
What is inflammation of the peritoneum called?
Peritonitis/peritinitis
What are the three unpaired arteries that arise from the anterior aspect of the abdominal aorta and that supply the organs within the abdomen?
Coeliac trunk
Superior mesenteric artery
Inferior mesenteric artery
What are the three main branches of the coeliac trunk?
The three main branches of the coeliac trunk are the left gastric artery, common hepatic artery and splenic artery. Each of these branches gives off more branches that supply the liver, gall bladder, stomach, lower oesophagus, spleen and proximal duodenum. The coeliac trunk is the artery that supplies the FOREGUT.
What does the superior mesenteric artery (SMA) branch into?
The superior mesenteric artery (SMA) branches into jejunal, ileocolic, right colic and middle colic arteries. The SMA is the artery that supplies the MIDGUT.
What does the inferior mesenteric artery (IMA) branch into?
The inferior mesenteric artery (IMA) branches into left colic, sigmoidal and superior rectal arteries. The IMA is the artery that supplies the HINDGUT.
At which vertebral level does the superior mesenteric artery branch from the aorta?
L1
At which vertebral level does the inferior mesenteric artery branch from the aorta?
L3
At which vertebral level does the coeliac trunk branch from the aorta?
T12
What are the three main branches that the coeliac trunk splits into?
It is worth noting that the coeliac trunk itself is very short and almost immediately divides into its three main branches:
- splenic artery
- left gastric artery
- common hepatic artery
What are the arcades and how are they different in the jejunum and ileum?
The arcades are arch-like loops of arteries
In the jejunum they are fewer and the vasa recta longer compared to the ileum, which has larger arcades and shorter vasa recta.
Which organs receives blood supply from the coeliac trunk?
Lower oesophagus Liver Gallbladder Spleen Stomach Proximal duodenum
Which organs receives blood supply from the SMA?
Distal duodenum Jejunum Ileum Caecum Ascending colon Transverse colon
Which organs receives blood supply from the IMA?
Descending colon
Sigmoid colon
Rectum
Which vein does the gut drain its venous blood towards?
Hepatic portal vein
Venous blood from the gut drains towards the hepatic portal vein towards the Liver. It is then filtered through the Liver before being returned to the IVC.
What is the hepatic portal vein? What is it formed by? Where does it drain to?
The hepatic portal vein (HPV) is the vessel that nutrient-rich, oxygen-poor blood from the gut travels in to get to the liver. It is formed by the union of the splenic vein and the superior mesenteric vein. Note the inferior mesenteric vein (of the hindgut) draining into the splenic vein. At the liver the HPV splits into left and right. Hepatic veins drain the liver into the inferior vena cava.
What vein is the inferior mesenteric vein received by?
The splenic vein receives the inferior mesenteric vein
What is the pancreas, where is it situated and what does it consist of?
The pancreas is a gland. It has both exocrine and endocrine functions.
It is mainly retroperitoneal and consists of an uncinate process, head, neck, body and tail. The head of the pancreas is found in the C-shape of the duodenum. The pancreas crosses the midline with its tail extending to the splenic hilum on the left.
Is the pancreas intra or retroperitoneal?
The pancreas has both intraperitoneal and retroperitoneal portions.
The head, neck and body are retroperitoneal and the tail is intraperitoneal.
What are the components of the biliary tree?
Common hepatic duct
Cystic duct
Ampulla of Vater/Hepatop ancreatic ampulla
Common bile duct
