Lecture 14: Anatomy Flashcards
The greater omentum is attached to which part of the large intestine?
Transverse colon
Describe the attachments of the greater omentum?
- Its a double sheet of peritoneum (ie. made up of 4 layers in total)
- It descends from the greater curvature of the stomach
- Hangs freely over the intestines.
- Double backs and attaches to the anterior surface of the transverse colon
Describe the Transverse mesocolon?
Broad, meso-fold of peritoneum, which connects the transverse colon to the posterior wall of the abdomen
Name these parts?
- Greater omentum (turned up)
- Transverse colon (turned up)
- Right colic (hepatic) flexure
- Small intestine (jejunum and ileum)
- Ascending colon
- Cecum
- Urinary bladder
Which parts of the large intestine have mesentery?
Appendix: mesentery is called mesoappendix
Transverse colon: mesentery is called transverse mesocolon
Sigmoid colon: mesentery is called sigmoid mesocolon
Describe how the greater omentum attaches the stomach to the posterior abdominal wall?
- The greater omentum descends from the greater curvature of the stomach.
- Hangs over the intestine and folds back posteriorly attaching to the anterior suface of the transverse colon.
- The transverse colon has the transverse mesocolon attached (a fold of peritoneum), that attached it to the posterior wall of the abdomen.
- Hence the indirect attachment of the stomach to the posterior wall
Which parts of the large intestine is retroperitoneal?
All the parts, except caecum, that does not contain mesentry.
Retroperitoneal: Ascending colon, descending colon, rectum and anal canal.
The cecum does not have its own mesentery but is covered in all aspects by?
Peritoneum
The peritoneum is comprised of which epithelium?
Simple squamous epithelial cells called mesothelium.
Mnemonic SAD PUCKER is used to recall which abdominal viscera are retroperitoneal.
What does SAD PUCKER stand for
Suprarenal (adrenal) glands
Aorta
Duodenum (except the initial part)
Pancreas (Except the tail)
Ureters
Colon (ascending, descending)
Kidneys
Esophagus (oesphagus)
Rectum and anal canal
What are the intraperitoneal organs?
Use the mnemonic:
Sick Individuals Judge The Seriously Supportive Dads.
Spleen
Ileum
Jejunum
Transverse colon
Stomach
Sigmoid colon
Duodenum (proximal part)
How long is the small intestine and why does it appear longer in dissection?
3 metres in length
The SI is relaxed in dissection so may be longer
Describe “The mesentry”?
The mesentry is the mesentry of the small intestine
(REMEMBER the “THE” part)
Double fold of peritoneal tissue that suspends the small intestine from the posterior wall
Fans out from the posterior wall to the small intestine.
Carries vessels to support the small intestine
What indicates the start of the large intestine?
The ileocecal valve
Sphincter muscle that separates the small intestine and the large intestine
What are the two flexures of the large intestine?
Right colic flexure also known as the hepatic flexure.
Left colic flexure aka the splenic flexure
Sharp bend of the large intestine
Describe the right colic flexure?
- Also known as the hepatic flexure (due to its close proximity to the liver)
- Sharp bend between the ascending colon and the transverse colon
- Lies in the right hypochondrium region
Describe the left colic flexure?
- Also known as the splenic flexure (due to its close proximity to the spleen)
- Sharp bend between the transverse colon and the descending colon
- Lies in the left hypochondrium region
Describe the direction of the transverse colon
After the hepatic flexure, the large intestine crosses to the left hand side of the body and also moves superiorly.
Towards the spleen, it then has a sharp bend and becomes the descending colon
At what point of the large intestine does it leave the abdominal cavity?
At the sigmoid colon level
What are the different parts of the large intestine
Caecum
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
Name these parts of the large intestine?
Explain how the ascending, descending colon and rectum are retroperitoneum despite that these anatomical regions are very anterior
The peritoneum buldges forward over these regions and then returns back.
What are the differences between the lumen of the large and small intesitne?
The lumen tends to be larger in the large intestine however can vary considerably and be as small as the small intestine.
What are the 3 anatomical characteristics of the large intestine (that distinguish it from the small intestine)?
- Appendices epeploicae
- Haustrations
- Taenia coli
Describe appendices epeploicae?
- Unique anatomical characteristic of the large intestine
- They are little fatty tags along the large intestine that are covered with peritoneum.
Name these unique characteristics of the large intestine?
Describe haustrations?
- Singular haustra
- Also known as sacculations
- Unique characteristic of the large intestine
- These are the small pouches caused by sacculation
- The sacculations are caused by the contraction of taeniae coli
Describe how the taenia coli forms the sacculation of the large intestine?
The taenia coli run the length of the large intestine. Because the taenia coli are shorter than the large bowel itself, the colon becomes sacculated, forming the haustrations
Describe taenia coli?
- Three bands of smooth muscle
- Thickened area of smooth muscle
- Located on the outside of the ascending, transverse, descending and sigmoid colons
- Can only see one ribbon of smooth muscle at the time due to the location (each located at different edges of the large intestine)
Describe the appendix?
- Not involved in digestion
- Contains a small amount of mucosa-associated lymphoid tissue which gives it an undetermined role in immunity
- Most often it hangs freely from the abdominal cavity
- Sometimes it can be retrocecal (localized behind the cecum)
The ascending colon includes?
The caecum and appendix
What are paracolic gutters?
Spaces between the colon and the abdominal wall
What is a key histological characteristic of the appendix?
Large number of lymph tissue (due to its undetermined role in immunity)
If the appendix burst, where does the fecal material tend to go in bed-bound patients?
Tend to go into the pelvic cavity
Describe the Morison’s pouch?
- Also known as the hepatorenal recess
- Deepest recess in the abdominal cavity
- Potential space that separates the liver from the right kidney
- Normal physiological conditions, it is not filled with fluid
When the appendix burst, where does the faecal matter run towards in patients lying down?
Towards the hepatorenal recess and rectrouterine pouch.
These are the two deepest recesses of the abdominal cavity.
Describe the Rectouterine pouch?
- Also known as the Pouch of Douglas
- An extension of the peritoneal cavity between the rectum and back wall of the uterus (in the female body)
- Note the rectouterine pouch is deeper than the vesicouterine pounch (space between bladder and uterus)
What is the significancy of the paracolic gutters in a burst appendix patient?
The fecal material can run down the right paracolic gutter and run into deeper recesses.
Describe the superior mesenteric artery?
- Major artery of the abdomen.
- It arises from the abdominal aorta, and supplies arterial blood to the organs of the midgut
- which spans from the major duodenal papilla (of the duodenum) to the proximal 2/3 of the transverse colon.
- Arises immediately inferior to the origin of the coeliac trunk
What are the three major anterior branches of the abdominal aorta?
Superior mesenteric artery
Inferior mesenteric artery
Coeliac trunk
Name these branches of the superior mesenteric artery?
The inferior pancreatoduodenal artery arises more proximally, and is not visible on this illustration
Describe the Inferior Pancreaticoduodenal Artery
- First branch of the superior mesenteric artery
- Forms anterior and posterior vessels
- Anastomose with branches of the superior pancreaticoduodenal artery
Describe the jejunal and ileal arteries branches?
- Numerous arteries that supply the jejunum and ileum.
- The arteries pass between the layers of the mesentery and form anastomotic arcades
- from which smaller, straight arteries arise to supply the organs
Describe the differences between the ileal and jejunal arteries (branches from the superior mesenteric artery)
The jejunal blood supply is characterised by a smaller number of arterial arcades, but longer vasa recta.
In contrast, the ileal blood supply is marked by more arterial arcades with shorter vasa recta
Describe anastomotic arcades?
Arcades are a series of anastomosing arterial arches between the arterial branches of the jejunum and ileum
More in the ilieal branches than the jejunal branches.
What does the Middle colic artery supply?
Supplies the transverse colon
What does the right colic artery supply?
Ascending colon
Describe the vasa recta?
the straight arterioles coming off from arcades in the mesentery of the jejunum and ileum, and heading toward the intestines
What does the ileocolic artery supply?
It is the final major branch of the superior mesenteric artery.
It passes inferiorly and to the right, giving rise to branches to the ascending colon, appendix, cecum, and ileum
Describe the blood supply to the splenic flexure?
Dual blood supply from the terminal branches of the superior mesenteric artery and the inferior mesenteric artery
Prone to ischemic damage in cases of low blood pressure because it does not have its own primary source of blood
The superior rectal artery is a continuation of which artery?
Inferior mesenteric artery
The superior rectal artery supplies which areas of the GI tract?
Rectum and anal canal
