Anatomy of Small and Large Intestines Flashcards
The small intestine is divided into?
- duodenum 2. jejunum 3. ileum
Describe the duodenum?
- C-shaped 2. retroperitoneal - except near stomach
What is the extent of the duodenum?
pyloric sphincter - duodenojejunal flexure
The duodenum is characterised by?
tubular Brunners glands in submucosa that secrete mucous
What is the primary function of the duodenum?
food digestion + absorption
What are the parts of the duodenum?
- superior 2. descending 3. horizontal 4. ascending
Describe the superior (first) part?
- related to the pylorus 2. intraperitoneal - found in the hepatoduodenal ligament : freely mobile
What are the posterior relations of the first part?
- bile duct 2. gastrodudenal art 3. portal vein
What condition is found mostly in the first part?
duodenal ulcers - 95%
Describe the consequence of the perforation of ulcers?
- erode gastroduodenal art - haemorrhage 2. duodenal contents cause abdominal peritonitis
Describe the descending (second) part?
- retroperitoneal 2. Bile duct and main pancreatic duct join to form hepatopancreatic ampulla on the posteromedial surface of the second part
What is the major duodenal papilla (of Vater)?
a round projection in the duodenum into which the common bile duct and pancreatic duct drain - the primary mechanism for the secretion of bile and other enzymes that facilitate digestion
Describe the relations of the second part of the duodenum?
- Fundus & body of gallbladder 2. right kidney 3. transverse colon 4. head of pancreas
Describe the horizontal (third) part?
- Retroperitoneal 2. crosses vertebral column at L3
The third part is related to?
- psoas major muscle 2. IVC and aorta 3. right ureter 4. gonadal vessels 5. superior mesenteric vessels
Describe the ascending (fourth) part?
- Retroperitoneal 2. ascends to the level of L2 3. contains the duodenojejunal flexure
What is the duodenojejunal flexure suported by?
suspensory ligament of Treitz
What is the clinical importance of the ligament of Treitz?
- Lig of Treitz used to locate duodenojejunal flexure
- Clinical dividing line between upper and lower gastrointestinal tracts
- Most gastrointestinal hemorrhage is above the ligament of Treitz, coming from esophagus, stomach
Describe the arterial supply of the duodenum?
- Supraduodenal art - can be used to identify the first part of the duodenum
- sup & inf pancreaticoduodenal arts with their ant & post branches that form arcades
- Right gastric art
- Gastroduodenal art
Describe the venous drainage?
Duodenal veins draining into the portal vein
Describe the lymphatic drainage of the duodenum?
- Ant lymphatic vessels drain into pancreaticoduodenal nodes, pyloric lymph nodes
- Post lymphatic vessels drain into sup mesenteric lymph nodes
- celiac lymph nodes
Describe the innervation?
- vagus nerve 2. Celiac & sup mesenteric plexuses
What is the extent of the jejunum?
duodenum - ileum
Describe the jejunum?
- intraperitoneal
- Most of it lies in left upper quadrant
- Lumen slightly larger than ileum; wall thicker than ileum
- More mucosal folds than ileum - plicae circulare & villi
- Deeper red with greater vascularity
- Long straright arteries - vasa recta
Describe the ileum?
- terminal portion of the small intestine 2. lies in right lowe quadrant 3. has shorter straight arteries than jejunum 4. has abundant lymph nodules - Peyers patches or Mesenteric patched : GALT
Describe the extent of the ileum?
ends at ileocecal junction and joins cecum medially through ileocecal valve
What is Meckels Diverticulum?
a remnant of the connection between gut tube & yolk sac that Projects from the ileum about 60cm from ileocaecal junction in about 2% of people
What may the Meckels Diverticulum contain?
pancreatic + gastric mucosa
Consequence of diverticulum mucosa ?
- can erode intestinal mucosa causing bleeding 2. presents a pain distribution similar to that of appendicitis
Describe the mesentery associated withjejunum and ileum?
attached to posterior abdominal by mesentery
Describe the exent of the root of mesentery?
duodenojejunal junction - ileocolic junction
The root of the mesentery crosses?
- ascending and horizontal duodenum 2. abdominal aorta and IVC 3. right ureter + right psoas major 4. right testicular or ovarian vessels
Describe the arterial supply of the jeunum and ileum?
Superior mesenteric artery (SMA) - arterial arcades that give rise to vasa recta (straight arts) - end arteries
Consequence of occlusion?
occlusion - ischemia of intestines
What is the origin of the SMA?
SMA origin – Transpyloric plane (L1) together with gall bladder (Murphy’s point); pylorus, renal hilum
Describe the venous drainage of jejunum and ileum?
superior mesenteric vein
Describe the lymphatic drainage of the ileum and jejunum?
Lacteals, sup mesenteric lymph nodes, ileocolic lymph nodes
Describe the innervation jejunum and ileum?
- parasympathetic - vagus nerve 2. sympathetic - lesser splanchnic nerve 3. superior mesenteric plexus