Anatomy - The Small and Large Bowels Flashcards
(92 cards)
1
Q
What are the 3 divisions of the small intestine called?
A
- Duodenum. 2. Jejunum. 3. Ileum.
2
Q
What is the principle function of the small intestine?
A
Digestion and absorption of food.
3
Q
What are the folds of mucosa inside the small intestine called?
A
Plicae circulares.
4
Q
What are Peyer’s patches?
A
Large, sub-mucosal, lymph nodules.
5
Q
Where in the small intestine would you find Peyer’s patches?
A
Ileum.
6
Q
Is the duodenum intraperitoneal or retroperitoneal?
A
Retroperitoneal.
7
Q
The first part of the duodenum is prone to peptic ulceration. What artery can this affect?
A
The gastro-duodenal artery. This artery lies in direct contact with the posterior wall of the first part of the duodenum.
8
Q
Would you describe the jejunum and ileum as intraperitoneal or retroperitoneal?
A
Intraperitoneal.
9
Q
What part(s) of the small intestine can become twisted? This results in strangulation and ischaemia.
A
Jejunum and ileum.
10
Q
Which has a thicker intestinal wall, the jejunum or the ileum?
A
Jejunum.
11
Q
Describe 5 characteristics of the Jejunum.
A
- Thick intestinal walls. 2. Longer vasa recta. 3. Less arterial arcades. 4. Pronounced plicae circulares. 5. Red in colour.
12
Q
Describe 5 characteristics of the Ileum.
A
- Thin intestinal walls. 2. Shorter vasa recta. 3. More arterial arcades. 4. Peyer’s patches. 5. Pink in colour.
13
Q
Where might you find Meckel’s diverticulum?
A
1 meter from the termination of the ileum.
14
Q
What is Meckel’s diverticulum an embryonic remnant of?
A
The attachment of the mid-gut to the yolk sac.
15
Q
Where does the mid-gut begin and end?
A
3rd part of duodenum to 2/3 along the transverse colon.
16
Q
What is the blood supply to the midgut?
A
Superior mesenteric artery (L1).
17
Q
What is the first branch of the SMA?
A
Inferior pancreaticoduodenal artery?
18
Q
Name 3 major branches of the SMA.
A
- Ileo-colic. 2. Right colic. 3. Middle colic.
19
Q
What does the right colic artery supply?
A
The ascending colon.
20
Q
What does the middle colic artery supply?
A
The transverse colon.
21
Q
Into which vein does blood from the jejunum and ileum drain and what is the final destination of the blood?
A
Drains into the superior mesenteric vein. This vein combines with the splenic vein to form the hepatic portal vein which then goes on to the liver.
22
Q
Which foodstuffs are absorbed through the lymphatic system?
A
Fats.
23
Q
What is the innervation of the small intestine?
A
Sympathetic: Lesser splanchnic (T10-11). Parasympathetic: Vagus. No somatic innervation.
24
Q
Name 4 mechanisms that ensure a high surface area for absorption of nutrients in the intestine.
A
- Pliae circularis. 2. Coiled length. 3. Villi. 4. Microvilli.
25
What is the main function of the large intestine?
Water absorption and the formation of faeces.
26
State whether the caecum is intraperitoneal or retroperitoneal and describe the blood supply and venous drainage.
- Intraperitoneal. - Ileocolic artery. - Ileocolic vein; drains into superior mesenteric vein.
27
State whether the ascending colon is intraperitoneal or retroperitoneal and describe the blood supply and venous drainage.
- Retroperitoneal. - Ileocolic and right colic arteries. - Ileocolic and right colic veins.
28
State whether the transverse colon is intraperitoneal or retroperitoneal and describe the blood supply and venous drainage.
- Intraperitoneal. - Middle colic artery. - Superior mesenteric vein.
29
State whether the descending colon is intraperitoneal or retroperitoneal and describe the blood supply and venous drainage.
- Retroperitoneal. - Left colic and superior sigmoid arteries. - Inferior mesenteric vein.
30
State whether the sigmoid colon is intraperitoneal or retroperitoneal and describe the blood supply and venous drainage.
- Intraperitoneal. - Sigmoid arteries. - Inferior mesenteric vein.
31
What is the marginal artery of Drummond?
An artery that forms important anastomosis between SMA and IMA. It extends the length of the colon.
32
What vertebral level is the inferior mesenteric artery found at?
L3.
33
Name 3 characteristic features of the large intestine that allow it to be distinguished from other abdominal organs.
1. Haustrations. 2. Tenia coli. 3. Appendices epiploicae.
34
What are appendices epiploicae?
Small pouches of peritoneum filled with fat. They mark where blood vessels enter the bowel to supply the mucosa.
35
What are tenia coli?
3 strips of longitudinally running muscle on the outer surface of the large intestine.
36
What are haustrations?
Sacculations produced from where the tenia coli contract to shorten the wall of the bowel.
37
Where does the hind gut begin and end?
Distal 1/3 of the transverse colon to the anal canal.
38
What is the innervation of the hind gut?
Sympathetic: least splanchnic nerve (T12). Parasympathetic: S2-4. No somatic innervation.
39
What artery normally supplies the descending colon?
The left colic artery.
40
What is the importance of the marginal artery of Drummond?
If there is an occlusion to the IMA, blood can still be supplied to the large intestine via the SMA through this artery.
41
Give 4 locations where the distal end of the appendix may lie.
1. In the pouch of Douglas. 2. Behind the caecum. 3. Behind the umbilicus. 4. Below the liver.
42
Name the intraperitoneal parts of the large intestine.
Caecum, transverse colon, sigmoid colon.
43
Describe the anatomy of the duodenum?
* most proximal portion of the small intestines
* runs from the pylorus of the stomach to the duodenojejunal junction
* Can be divided into four parts: superior, descending, inferior, and Ascending
* forms a C shape, 25cm, wraps around the head of the pancreas
44
Describe the superior section of the duodenum?
* known as the cap
* Ascends upwards from the pylorus of the stomach
* Connected to the liver by the hepato-duodenal ligament
* Most common site of duodenal ulceration
* initial 3cm is covered by the visceral peritoneum, and the remainder is retroperitoneal
45
Describe the descending section of the duodenum?
* curves inferiorly around the head of the pancreas
* lies posterior lead to the transverse colon and interiorly to the right kidney
* internally marked by the major duodenal papilla - where bile and pancreatic secretions enter the ampulla of Vater
46
Describe the inferior section of the duodenum?
* travels laterally to the left, crossing over the inferior vena cava and aorta
* located inferiorly to the pancreas and posteriorly to the superior mesenteric artery and vein
47
Describe the ascending section of the duodenum?
* after crossing the aorta, it ascends and curves anteriorly
* joins jejunum at sharp turn known as the duodenojejunal flexure
48
How does the duodenojejunal junction work?
* the suspensory muscle of the duodenum contracts
* widens the angle of the flexure
* Leads movement of the intestinal contents into the jejunum
49
How are the jejunum and ileum Related to the posterior abdominal wall?
* intraperitoneal
* attached to the posterior abdominal wall by mesentery ( double layer peritoneum)
50
Describe the anatomy of the jejunum and ileum?
* jejunum begins at the duodenojejunal flexure
* there is no clear external demarcation between them, but they are microscopically different
* The ileum ends at the ileocecal junction
51
Describe the ileocecal junction's anatomy?
* The ileum invaginates into the caecum To form the ileocecal valve
* it can only prevent reflux material back into the ileum
52
What are the five things that you are able to distinguish between the jejunum and ileum during surgery?
* jejunum located in the upper left quadrant, ileum Located in the lower right quadrant
* jejunum has thick intestinal walls, ileum has thinner intestinal wall
* jejunum has longer Vasa recta, ileum has shorter Vasa recta
* jejunum has less arcades (Arterial loops), has more arcades
* jejunum is red in colour, ileum is pink in colour
53
What are the two arterial sources that supply the duodenum?
* Proximal to the major duodenal papilla - gastroduodenal Artery ( branch of the common hepatic artery from the coeliac trunk)
* Distal to the major duodenal papilla - inferior pancreaticoduodenal artery (branch of the superior mesenteric artery)
* Marks a change of foregut to the midgut
54
Where the veins of the duodenum drain into?
hepatic portal vein
55
Where does the lymphatic drainage of the duodenal drain in to?
pancreatoduodenal and superior mesenteric nodes
56
Describes the arterial supply to the jejunum and ileum?
* superior mesenteric artery
* arises from the aorta at L1, immediately inferior to the coeliac trunk
* splits into 20 branches, forming loops called arcades
* long straight arteries arise called vasa recta
57
Where does the venous drainage of the jejunum and ileum drain into?
* via the superior mesenteric vein
* unites with the splenic vein at the neck of the pancreas to form the hepatic portal vein
58
Where does the lymphatic drainage of the jejunum and ileum drain into?
superior mesenteric nodes
59
Describe the major duodenal papillae?
* nipple shaped lump on the inside of the duodenum, where the common bile duct and pancreatic duct open
* between the second and third parts of the duodenum
* marks the end of the Foregut and the start of the midgut
60
Describe the ampulla of Vater?
* Small channel formed inside the major duodenal papilla
* where the common bile duct and pancreatic duct merge, just before they release their juices into the duodenum
61
Describe the sphincter of Oddi?
* controls the release of bile and pancreatic juices from the ampulla of Vater into the duodenum
62
Describe plicae circularis? Where are they most pronounced?
* Internal folds of the mucosa, increase the surface area
* also known as valavulae conniventes
* Most pronounced in the jejunum
63
Name the large submucosal lymph nodes found in the ileum?
Peyer's patches
64
What is Meckel's diverticulum?
* blind-ended diverticulum about 1m from ilium termination
* Embryonic remnant of the attachment of the midgut loop to the yolk sac
65
Where is there more fat deposited in the mesentery?
* Increasing amounts towards ilium end
66
What 4 anatomical features ensure the small bowel has a high surface area for absorption of nutrients?
Length, mucosal folds (plicae circularis), villi and micro-villi
67
Name and describe the first part of the colon?
* Ascending colon
* the retroperitoneal structure which ascends superiorly from the cecum
* Turns the right colic flexure (or hepatic flexure) the right lobe of the liver
* marks the start of the transverse colon
68
Name and describe the second part of the colon?
* the transverse colon
* extends from the right colic flexure to the spleen
* turns 90° to point inferiorly, known as the left colic flexure (or splenic flexure)
* Least fixed part of the colon, variable in position
69
How is the transverse colon attached to the diaphragm?
phrenicocolic ligament
70
How does the transverse colon differ from the ascending and descending colon in terms of it's positioning?
It is intraperitoneal and is enclosed by the transverse mesocolon
71
Describe the descending colon?
* moves inferiorly towards pelvis
* retroperitoneal, but is located anteriorly to the left kidney passing over its lateral border
* when it turns medially it becomes a sigmoid colon
72
Describe the location of the sigmoid colon?
* located in the lower left quadrant of the abdomen
* extending from the left iliac fossa to the level of the S3 vertebrae
73
How does the sigmoid colon attach the posterior pelvic wall?
* via the sigmoid mesentery
* The long length of the mesentery allows it to be particularly mobile
74
What are the Paracolic gutters?
* Two spaces between the ascending and descending colon and the postero-lateral abdominal wall
* Allow material that is been released from inflamed or infected abdominal organs to accumulate elsewhere in the abdomen
75
What are omental appendices?
small pouches of peritoneum filled with fat
76
What are the teniae coli? name them? What do they cause?
* Muscles longitudinally running along the surface of the colon
* mesocolic, free and omental coli
* produces sacculations called haustra
* Play a role in peristalsis
* broadened out to form a continuous layer at the recto sigmoid junction
77
What part of the colon is part of the midgut and what is its arterial supply?
* ascending colon, and proximal two-thirds of the transverse colon
* supplied by the superior mesenteric artery
* 3 branches called the ileocolic, middle and right colic artery
78
What part of the colon is part of the hindgut and what is its arterial supply?
* Distal one third of the transverse colon, descending colon and sigmoid colon
* supplied by a single branch of the inferior mesenteric artery - the left colic artery and superior rectal arteries
* sigmoid colon receives arterial supply via the sigmoid arteries
79
Describe the venous drainage of the Midgut and hindgut?
* midgut - superior mesentery vein
* hindgut - inferior mesentery vein, drains into the splenic vein
* both empty into the hepatic portal vein, allows toxins to be absorbed from the colon to be processed by the liver for detoxification
80
How is the midgut innervated?
Sympathetic, parasympathetic and censoring supply via nerves from the superior mesenteric plexus
81
How is the hindgut innervated?
* Sympathetic, parasympathetic and sensory supply via the inferior mesenteric plexus (Sacral nerves 2,4,5)
* parasympathetic via pelvic splanchnic nerves
* sympathetic via the lumbar splanchnic nerves
82
How is the Lymphatics of the midgut drained?
* into the superior mesenteric nodes
* passes into the intestinal lymph trunks, and into the cisterna chyli and thoracic duct
83
How is the lymphatics of the hindgut drained?
* inferior mesenteric nodes
* passes into the intestinal lymph trunks, and into the cisterna chyli
84
What protrudes from the external wall of the caecum inferiorly?
the appendix
85
What is the mesorectum?
perirectal fat that surrounds the rectum
86
What are the 3 major branches of the Coeliac trunk?
The left gastric, the splenic and the common hepatic.
87
What does the left gastric artery supply?
The lesser curvature of the stomach and lower oesophagus.
88
What branches does the splenic artery give off?
- The short gastric arteries. - The pancreatic arteries. - The left gastroepiploic artery. - 5 branches just before it reaches the Spleen.
89
What do the short gastric arteries supply?
The greater curvature of the stomach.
90
What does the left gastroepiploic artery supply? What does anastomose with?
It supplies the greater curvature of the stomach. It anastomoses with the right gastroepiploic artery.
91
Name the 2 branches of the common hepatic artery.
1. Proper hepatic artery. 2. Gastroduodenal artery.
92
What is the appendicular artery a branch of?
The ileocolic artery (branch of SMA).
