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Phase 1 GI > Session 2: The Stomach and the Small and Large intestine > Flashcards

Session 2: The Stomach and the Small and Large intestine Flashcards

1
Q

Where does the oesophagus pass through the diaphragm?

A

At the oesophageal hiatus in the diaphragm at the level of T10.

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2
Q

What supplies the distal oesophagus?

A

by branches from the left gastric artery.

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3
Q

What does the stomach do?

A

The stomach chemically and mechanically breaks down food into chyme.

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4
Q

How is the stomach structured?

A
  • cardia of the stomach.
  • fundus
  • body.
  • pyloric antrum
  • pyloric canal
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5
Q

Where is the stomach? Covered by?

A

The stomach lies in the left upper quadrant. It is covered with visceral peritoneum.

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6
Q

What is the blood supply of the stomach?

A
  • supplied by arteries that branch from the coeliac trunk.
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7
Q

What does the coeliac trunk divide into?

A

it divides into
1. Left gastric artery
2. Common hepatic artery
3. Splenic artery

Lies close to the aorta.

  • left gastric is smaller vessel than the common hepatic and splenic arteries.
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8
Q

Where are the gastric arteries?

A

The left and right gastric arteries run along the lesser curvature of the stomach and anastomose with each other.

  • Left gastric artery - from coeliac trunk
  • Right gastric artery - from either common hepatic artery or hepatic artery proper.
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9
Q

Where are the gastro-mental arteries?

A

The left and right gastro-omental (gastroepiploic) arteries run along the greater curvature of the stomach and anastomose with each other.

  • The left gastro-omental artery arises from the splenic artery.
  • The right gastro-omental artery arises from the gastroduodenal artery, a branch of the common hepatic artery.
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10
Q

What do the gastric veins do?

A

Right and left gastric veins and right and left gastro-omental veins accompany their respective arteries.

They ultimately drain into the hepatic portal vein (HPV). The hepatic portal vein is a large vein that carries nutrient-rich venous blood from the GI tract to the liver.

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11
Q

What is the stomach innervated by?

A

The vagus nerve conveys parasympathetic fibres to the stomach. Promotes peristalsis and gastric secretion.

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12
Q

What is a hiatus hernia?

A

When the abdominal oesophagus and upper part of the stomach may herniate through the oesophageal hiatus into the thorax.

Patients may experience heartburn and acid reflux.

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13
Q

What causes a gastric ulcer?

A

Mucous lines the internal wall of the stomach and protects the mucosa from the acidic stomach contents.

A gastric ulcer develops when the mucosal lining of the stomach breaks down.

This is normally due to infection with Helicobacter pylori, which erodes the mucosal lining, exposing the muscular wall to gastric acid and enzymes.

Erosion through the wall and into nearby blood vessels can result in catastrophic intra-abdominal bleeding.

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14
Q

What is gastric cancer?

A

Primary cancer of the stomach may present late as some of the symptoms are non- specific.

Symptoms include abdominal discomfort, early satiety (feeling full quickly), loss of appetite, nausea, weight loss, difficulty swallowing and indigestion.

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15
Q

Where does the small intestine lie?

A

The small intestine lies centrally in the abdomen and has three ‘parts’ that are continuous with each other; the duodenum, the jejunum, and the ileum.

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16
Q

Where is the duodenum?

A

The duodenum is continuous with the pylorus of the stomach. Curved into a C-shape around the head of the pancreas. Most of the length of the duodenum is retroperitoneal.

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17
Q

How does the duodenum develop?

A

The first half of the duodenum develops from the embryological foregut and is supplied by arterial branches from the coeliac trunk. The second half of the duodenum develops from the embryological midgut and is supplied by branches from the artery of the midgut – the superior mesenteric artery.

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18
Q

Where is the jejunum and ileum?

A

The jejunum is continuous with the duodenum.
Both are intraperitoneal and are ‘suspended’ from the posterior abdominal wall by the mesentery of the small intestine.

The jejunum lying in the left upper region and the ileum lying in the right lower region. Both the jejunum and ileum are derived from the embryological midgut.

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19
Q

What does the large intestine do?

A

The large intestine reabsorbs water from faecal material to form semi-solid faeces.

  • lies peripherally in the abdomen
    composed of the caecum, appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anal canal.
  • Some segments are retroperitoneal, and some are intraperitoneal.
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20
Q

What is the caecum?

A

The caecum is the first part of the large intestine. It is a distended, blind-ended ‘pouch’. The caecum is covered by peritoneum but does not have a mesentery.

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21
Q

What is the ascending colon?

A

The ascending colon is continuous with the caecum. It runs vertically on the right side of the posterior abdominal wall in the right paracolic gutter. It is retroperitoneal (it is an example of a secondarily retroperitoneal organ).

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22
Q

What is the transverse colon?

A

The transverse colon is continuous with the ascending colon. It runs horizontally in the upper abdomen but often hangs inferiorly. It is intraperitoneal and is suspended from the posterior abdominal wall by the transverse mesocolon.

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23
Q

What is the descending colon?

A

Descending Colon
The descending colon is continuous with the transverse colon superiorly and the sigmoid colon inferiorly. It runs vertically on the left side of the posterior abdominal wall in the left paracolic gutter. It is retroperitoneal (also secondarily retroperitoneal).

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24
Q

What is sigmoid colon?

A
  • lies in the left lower quadrant
  • named because of its sinuous shape
  • continuous with the descending colon superiorly and the rectum inferiorly
  • As the sigmoid approaches the midline, it makes a 90 degree turn inferiorly into the pelvis
  • this ‘bend’ is the rectosigmoid junction
  • The sigmoid colon has a mesentery - the sigmoid mesocolon - and is therefore intraperitoneal.
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25
Q

Where is the rectum and anal canal?

A

The rectum lies in the pelvis and is retroperitoneal. It is continuous superiorly with the rectosigmoid junction (at the level of S3) and inferiorly with the anal canal. The rectum stores faeces until it is convenient to defecate.

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26
Q

Where does the coeliac trunk leave the aorta?

A

We looked at the coeliac trunk when we looked at the stomach. It leaves the aorta at the level of T12 and gives rise to branches that supply the foregut – the oesophagus, stomach, first half of the duodenum, liver, gallbladder, bile ducts, pancreas and spleen.

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27
Q

Where is the superior mesenteric artery?

A
  • artery of the midgut
  • leaves the aorta at the level of L1
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28
Q

What are the major branches of the SMA?

A

supply the midgut. Major branches are:
* Jejunal branches – several branches to the jejunum
* Ileal branches – several branches to the ileum
* Ileocolic artery – supplies the caecum, appendix, and ascending colon
* Right colic artery – supplies the ascending colon
* Middle colic artery – supplies the transverse colon.

29
Q

What does the muscle around the oesophageal hiatus function as?

A

As a sphincter that prevents reflux of stomach contents into the oesophagus. The abdominal segment of the oesophagus is less than 2 centimetres long.

30
Q

Venous drainage of oesophagus?

A

towards both the systemic system of veins (via oesophageal veins that drain into the azygos vein) and to the portal venous system (via the left gastric veins). The distal oesophagus is thus a site of portosystemic anastomoses, which are clinically important.

31
Q

What is in the pyloric canal?

A

contains the pyloric sphincter. The sphincter is a formed of circular smooth muscle. It regulates the passage of chyme into the duodenum.

32
Q

What are the borders of the stomach like?

A

The right border of the stomach is the lesser curvature. The longer left border is the greater curvature.

33
Q

What is the stomachs anterior and posterior surface related to?

A
  • Stomachs anterior surface is related to anterior abdominal wall, diaphragm, and left lobe of the liver.
  • Posterior surface forms the anterior wall of the lesser sac.
34
Q

What other structures form the lesser sac?

A
  • The lesser sac and the structures that form its posterior wall lie posterior to the stomach: these include the pancreas, left kidney and spleen.
35
Q

What does the lesser omentum and greater ommentum connect and hang from?

A
  • The lesser omentum connects the lesser curvature to the liver.
  • The greater omentum hangs from the greater curvature.
36
Q

What does the free edge contain and what is posterior to it?

A
  • The free edge of the lesser omentum contains the hepatic artery, hepatic portal vein and the bile duct.
  • Posterior to the free edge is the entrance to the lesser sac.
37
Q

What is the coeliac trunk?

A

The coeliac trunk is one of three large unpaired vessels that leave the anterior aspect of the abdominal aorta (at the level of T12) to supply the abdominal viscera that are derived from the embryological foregut.

38
Q

What comprises the foregut?

A

The foregut comprises the stomach, the first half of the duodenum, the liver, gallbladder, and pancreas. The spleen develops in the dorsal mesentery, and is supplied by the coeliac trunk, but it is mesodermal in origin.

39
Q

What is pyloric stenosis

A
40
Q

What is the other innervation of the stomach?

A

Sympathetic fibres conveyed via greater splanchnic nerve.

The postganglionic fibres travel to the stomach and inhibit peristalsis and secretion.

41
Q

How are sympathetic fibres conveyed to the stomach?

A

The greater splanchnic nerve is formed of preganglionic sympathetic fibres that leave spinal cord segments T5-T9 and pass through the sympathetic trunk without synapsing. The fibres synapse in prevertebral ganglia around the coeliac trunk.

The postganglionic fibres travel to the stomach and inhibit peristalsis and secretion.

42
Q

Where is the major duodenal papilla?

A

Approximately halfway along the internal wall of the duodenum is the major duodenal papilla. This is the opening of the bile duct and the main pancreatic duct into the duodenum.

43
Q

Which blood vessels are embedded within the mesentery?

A

Blood vessels that supply the small intestine (from the superior mesenteric artery) are embedded within the mesentery.

44
Q

How are the jejunum and ileum adapted for function?

A

The jejunum and ileum are the sites of nutrient absorption, so have a vast surface area: the small intestine is long, the mucosa is folded (plicae circulares), the mucosal folds bear villi and there are microvilli on the luminal surface of each epithelial cell.

However, there are some internal differences. The plicae are more pronounced in the jejunum. The internal ileum is characterised by Peyer’s patches, which are large submucosal lymph nodules.

In some people, the ileum bears a blind-ended diverticulum approximately one metre from its termination called a Meckel’s diverticulum. It is the embryological remnant of the connection that was present between the midgut loop to the yolk sac. If it becomes inflamed, it may mimic an appendicitis (inflammation of the appendix).

45
Q

Where is the terminal ileum?

A

The terminal ileum is continuous with the caecum - the first part of the large intestine – at the ileocaecal junction in the right iliac fossa.

46
Q

How is the LI distinguished in the cadaver?

A

It is peripherally located, and larger calibre.
- The outer longitudinal muscle layer is organised into three bands – the taeniae coli.
- The inner circular muscle layer forms ‘bulges’ called haustra (or haustrations).
- The large intestine bears fatty tags called epiploic appendages (appendices epiploicae)

47
Q

What do epiploic appendages of the LI mark?

A

that mark the point at which blood vessels penetrate the intestinal wall

48
Q

What is the appendix?

A

The appendix is a small diverticulum that arises from the caecum and contains lymphoid tissue. The surface marking of the base of the appendix is McBurney’s point. The appendix varies in length and the position of its tip is variable. The appendix is connected to the caecum by a small mesentery, the mesoappendix.

49
Q

What is the hepatic flexure?

A

The ascending colon makes a 90 degree turn left in the right upper quadrant, becoming continuous with the transverse colon. The ‘bend’ in the colon here is the hepatic flexure (sometimes called the right colic flexure).

50
Q

What is the splenic flexure?

A

The transverse colon makes a 90 degree turn inferiorly in the left upper quadrant, becoming continuous with the descending colon. The ‘bend’ in the colon here is the splenic flexure (sometimes called the left colic flexure). The splenic flexure is tethered to the diaphragm by the phrenicocolic ligament.

51
Q

What does the transverse colon mark embryologically?

A

The transverse colon marks the transition point between the embryological midgut and embryological hindgut. The proximal (first) two thirds develop from the embryological midgut, whilst the distal (last) third develops from the embryological hindgut. This means that these two parts of the transverse colon are supplied by different blood vessels and nerves. We will learn more about this later.

52
Q

Where does the SMA supply?

A

branches supply the midgut structures: the second half of the duodenum, the small intestine, and the large intestine as far as (and including) the first two thirds of the transverse colon.
- Branches also supply parts of the pancreas.

53
Q

What are arcades? Run?

A

The jejunal and ileal branches are embedded in the mesentery of the small intestine. They anastomose with each other, forming ‘loops’ of arteries called arcades.

From these arcades run the vasa recta (‘straight’ vessels), which supply the intestinal wall.

54
Q

What is the IMA?

A
  • artery of the hindgut.
  • leaves aorta - L3
  • It is a smaller calibre vessel than the coeliac trunk and SMA.

Major branches are:
• Left colic artery – supplies the transverse colon and the descending colon
• Sigmoid branches – supply the sigmoid colon
• Superior rectal artery – the terminal branch of the IMA, which supplies the rectum.

55
Q

What structures does the IMA supply?

A

Its branches supply the hindgut structures: the distal third of the transverse colon, the descending and sigmoid colon, the rectum, and the upper part of the anal canal. The IMA gives rise to several major branches that supply the hindgut.

56
Q

What forms the marginal artery?

A

Branches of the middle colic artery (from the SMA) and left colic artery anastomose along the distal third of the transverse colon and the splenic flexure forming the marginal artery. Branches of the left colic and sigmoid arteries also anastomose.

57
Q

What supplies the rectum?

A

The rectum is also supplied by middle and inferior rectal arteries which branch from the internal iliac arteries in the pelvis. The middle and inferior rectal arteries anastomose with branches of the superior rectal arteries.

58
Q

Where does venous drainage from gut go?

A

Venous blood from the gut ultimately reaches the inferior vena cava (IVC) and is returned to the heart. However, venous blood from the gut contains absorbed nutrients, so it first enters the liver via the portal venous system before being returned to the heart via the IVC.

59
Q

What drains the hindgut, midgut and liver?

A
  1. IMV - splenic vein (from spleen)
  2. SMV - splenic vein - hepatic portal vein
  3. Hepatic portal vein - small hepatic veins - IVC
60
Q

What drain rectum venous blood/

A

Venous blood from the rectum drains into both the portal system (via the IMA) and into the systemic system (via the internal iliac veins).

61
Q

What are the innervation for midgut and hindgut?

A

Parasympathetic fibres:
Midgut Via vagus
Hindgut via pelvic splanchnic nerves

62
Q

What is the sympathetic innervation of the small and large intestines?

A

T5-T12 - Greater5-9, lesser 10-11 and least splanchnic nerves 12
Inhibit function

63
Q

What also innervates the gut?

A

The gut is also innervated by visceral sensory fibres which convey visceral sensory information from the gut to the CNS. Such information usually does not reach consciousness, but painful sensations caused by ischaemia, distension or spasm do reach our conscious perception.

As a rule, visceral sensory fibres that travel with sympathetic nerves convey painful sensations, whereas visceral sensory fibres that travel with parasympathetic nerves convey information that maintains the internal environment and elicits reflex responses.

64
Q

How does pain relate to sympathetic fibres?

A

• foregut - T5 – T9 info = upper abdomen and epigastrium
• midgut - T10 – T11 info = the umbilical region
• hindgut - T12 info = the suprapubic region

Pain from the abdominal viscera is referred to the body wall:
• epigastric pain suggests foregut pathology
• central abdominal / umbilical pain suggests midgut pathology
• lower abdominal / suprapubic pain suggests hindgut pathology.

65
Q

What is appendicitis?

A

Inflammation of the appendix is appendicitis and is a common acute surgical presentation. The pain of appendicitis typically begins in the umbilical region and is poorly localised. This is the result of irritation of the visceral peritoneum (visceral sensory afferents returning to spinal cord segment T10). As inflammation progresses, the adjacent parietal peritoneum becomes involved. This causes severe, well localised pain in the right iliac fossa (which is conveyed to the CNS via somatic nerves that innervate the body wall). Therefore the history is of diffuse umbilical pain that ‘moves’ to the right iliac fossa. Symptoms can vary, depending on where the tip of the appendix lies. Tenderness is maximal over McBurney’s point. Rupture of the appendix can lead to peritonitis. Removal of the appendix (appendicectomy) is usually performed via laparoscopy (‘keyhole’ surgery).

66
Q

What is mesenteric ischaemia?

A

Just like the coronary arteries, the mesenteric vessels may be occluded by a thrombus. This results in ischaemia of the intestine which may progress to infarction. Acute mesenteric ischaemia is a surgical emergency. The gut must be revascularized and any sections of necrotic intestine must be removed. Mortality is high, even when the condition is recognised and treated.

67
Q

What is inflammatory bowel disease?

A

Crohn’s disease and ulcerative colitis are two types of inflammatory bowel disease.
Crohn’s disease is characterised by inflammation of the gut mucosa. It can affect any part of the GI tract but typically affects the small intestine. Patients suffer with symptoms including abdominal pain, diarrhoea, bloody stools, weight loss and tiredness. Ulcerative colitis affects the colon and rectum. The mucosa becomes inflamed and ulcerated. Patients suffer with abdominal pain, bloody diarrhoea, weight loss and tiredness. Flare-ups of both diseases can be serious and may lead to life-threatening complications. If medications fail to control symptoms, the affected part of the gut may be removed.

68
Q

What is colon cancer?

A

Cancer of the colon (often called bowel cancer) is common in the UK. The main symptoms of colon cancer are a change in bowel habit, blood in the stools and abdominal pain or bloating. Colonoscopy allows visualisation of the colon and biopsies can be taken if a mass is seen.

69
Q

What is volvulus?

A

Volvulus is twisting of the gut. It affects parts of the gut that are mobile (i.e. have a mesentery) and is most common at the sigmoid colon. Twisting obstructs the passage of faeces and may cause ischaemia and infarction of the affected part of the gut.

Phase 1 GI (3 decks)

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