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GI > 1 - Overview of GI > Flashcards

1 - Overview of GI Flashcards

1
Q

What are the functions of the gut?

A 
Provide a port of entry for food into the body
Mechanically disrupt food 
Temporarily store food
Chemically digest food 
Kill pathogens in food 
Move food along GI tract 
Absorb nutrients from resulting solution 
Eliminate residual waste material
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2
Q

What are the accessory organs of the GI tract?

A

Salivary glands
Liver
Gallbladder
Pancreas

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3
Q

What is the order food passes through the GI tract in?

A 
Mouth
Stomach
Duodenum 
Jejunum
Ileum 
Cecum 
Anus
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4
Q

How does the stomach turn food into chyme?

A

Upper area creates basal tone through slow and sustained contractions
Lower area has powerful peristaltic contractions that grind food, via thick layer of muscle distally
These together liquify food into chyme

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5
Q

How does the stomach act as an effective storage facility?

A

Rugae allows stomach to distend when full, and fold up when empty
Receptive reflex - gastric fundus (upper stomach) dilates when food passes the oesophagus so intraluminal pressures don’t increase so much

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6
Q

How is food chemically digested?

A

Saliva - Amylase (starch) and lipase (fats)
Stomach - HCl and pepsin (protein)
Duodenum/jejunum - Bile and exocrine pancreas hormones

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7
Q

What defence mechanisms does the GI system have against pathogens?

A

Saliva
HCL
Liver - kupffer cells
Peyers patches - organised into lymphoid follicles, in the submucosa in terminal ileum and distal jejunum

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8
Q

What types of movement occur in the GI tract?

A

Peristalsis
Segmentation
Haustral shuttling
Mass movements

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9
Q

What structural features of the gut aid in absorption?

A

Length of the gut
Folds
Microvilli
Increase SA

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10
Q

What is the function of the mouth?

A

Physical breakdown of food
Initial digestive enzymes released
Infection control

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11
Q

What is the function of the oesophagus?

A

Rapid transport of bolus to stomach through thorax
Upper: Prevents air from entering GI tract
Lower: Prevents reflux into oesophagus

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12
Q

What is the function of the stomach?

A

Storage facility
Produce chyme (physical/chemical breakdown/start digestion)
Infection control
Secretion of intrinsic factor (for vit B12 absorption)

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13
Q

What is the function of the duodenum?

A

Neutralisation of chyme (via HCO3 secretion)

More digestion of chyme (bile and pancreatic secretions)

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14
Q

What is the function of jejunum/ileum?

A 
Finish digestion 
Nutrient absorption - mostly jejunum 
Water/electrolyte absorption - mostly ileum
Bile recirculation - ileum
B12 absorption - terminal ileum
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15
Q

What is the function of the large bowel?

A

Final electrolyte and water absorption (via AQP channels against con gradient)

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16
Q

What is the function of the rectum?

A

Defaecation

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17
Q

What is the peritoneal cavity?

A

Potential space found between the parietal and visceral peritoneum

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18
Q

What is contained in the peritoneal cavity and what is its function?

A

Peritoneal fluid

Acts a lubricant, enabling free movement of abdominal viscera and contains antibodies that fight infection

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19
Q

Why is the peritoneal cavity considered a potential space?

A

Normally very thin but excess fluid can accumulate, causing ascites

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20
Q

What are the causes of ascites?

A 
Portal hypertension, secondary to liver cirrhosis 
Peritonitis 
Infection
GI malignancies 
malnutrition
Right sided heart failure
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21
Q

Define peritonitis

A

Infection and inflammation of the peritoneum, fluid is secreted into the peritoneal cavity

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22
Q

What are the causes of peritonitis?

A

Secondary to infection elsewhere in the GI tract eg
Burst appendix
Acute pancreatitis
Gastric ulcer eroding through wall of stomach
Bacterial contamination during a laparotomy (surgical incision of the peritoneum)

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23
Q

What is guarding and when does it occur?

A

When the anterolateral abdominal muscles contract to protect the viscera, during peritonitis

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24
Q

Why do patients with peritonitis lie with their knees flexed?

A

In an effort to relax the contracting anterolateral abdominal wall muscles

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25
Q

Why is generalised peritonitis a problem?

A

Can result in sepsis

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26
Q

Why are patients with ascites encouraged to sit upright?

A

Encourages the flow of ascitic fluid into the pelvis via the paracolic gutters, where toxins are absorbed more slowly

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27
Q

When are the paracolic gutters involved in spreading disease?

A

Provide a route for the spread of intraperitoneal infections and cancer metastases

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28
Q

What are the paracolic gutters?

A

Peritoneal recesses on the posterior abdominal wall, next to ascending or descending colon

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29
Q

How is the peritoneal cavity divided?

A

Into greater and lesser peritoneal sacs

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30
Q

How is the greater sac divided?

A

Split in two by the mesentery of the transverse colon
Supracolic compartment: Contains stomach, liver and spleen
Infracolic compartment: Contains small intestine, ascending and descending colon. Split into left and right infracolic spaces by the mesentery of the small intestine

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31
Q

What connects the supra and infracolic compartments?

A

The paracolic gutters

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32
Q

What are the subphrenic spaces?

A

Recesses in the greater sac of the peritoneal cavity between diaphragmatic surface of the liver and the diaphragm

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33
Q

How are the subphrenic spaces separated?

A

Separated into right and left subphrenic spaces by the falciform ligament of the liver

34
Q

When and where do subphrenic abscesses occur?

A

When pus accumulates as a result of peritonitis, can occur in right or left subphrenic space but more commonly the right due to appendicitis and ruptured duodenal ulcers

35
Q

How are the greater and lesser sacs connected?

A

Via the epiploic foramen, an opening in the lesser sac posterior the free edge of the lesser omentum - the hepatoduodenal ligament

36
Q

What is the function of the lesser sac?

A

Allows the stomach to move freely against structures posterior and inferior to it

37
Q

Where is the lesser sac located?

A

Posterior to the stomach and lesser omentum

38
Q

Describe the structure of the peritoneal cavity in the male pelvis

A

Retrovesical pouch is a double folding of peritoneum between rectum and bladder, is completely closed.

39
Q

Describe the structure of the peritoneal cavity in the female pelvis

A

Rectouterine pouch is a double folding of peritoneum between rectum and posterior wall of uterus.
Anterior to this, the vesicouterine pouch is a double folding of peritoneum between the anterior surface of uterus and bladder.
Peritoneal cavity is not completely closed as the abdominal ostia (distal opening) of uterine tubes open into it.

40
Q

What is an oesophagogastroduodenoscopy? (OGD)

A

An endoscope that can visualise the oesophagus, stomach and proximal duodenum

41
Q

Using an OGD, what common oesophageal problems can be seen?

A

Damage from acid reflux
Strictures
Outgrowths from mucosal surface (eg cancer)

42
Q

Using and OGD, what common stomach problems can be seen?

A

Ulcerations (often on lesser curve)

Outgrowths from the mucosal surface

43
Q

What is the main landmark visible in the oesophagus?

A

The oesophagogastric mucosal junction, where pale pink squamous oesophageal mucosa meets dark red gastric mucosa

44
Q

What is Barrett’s oesophagus?

A

Chronic inflammation from chronic acid exposure leading to reflux oesophagitis, causing metaplasia of lower oesophageal squamous epithelium (pink) to gastric columnar epithelium (red) which contain goblet cells

45
Q

Where does the oesaphagus pass through the diaphragm?

A

The oesphageal hiatus (hole in diaphragm) which is around the oesophagogastric mucosal junction

46
Q

When can the relationship between the oesophagus and diaphragm be affected?

A

In a hiatus hernia: Weakness in oesophageal hiatus allows cardia and fundus of stomach to herniate into the thorax

47
Q

Describe the arterial blood supply to the oesophagus

A

Upper 2/3: Inferior thyroid and aortic branches

Lower 1/3: Left gastric branch of celiac trunk and left inferior phrenic artery

48
Q

Describe the venous drainage of the oesophagus

A

Upper 2/3: Drains directly into systemic circulation via inferior thyroid branches and azygos branches
Lower 1/3: Drains into portal system via left gastric vein

49
Q

What are oesophageal varices?

A

Very dilated sub-mucosal veins in the lower third of the oesophagus, usually as a consequence of portal hypertension due to cirrhosis

50
Q

What are the mechanisms preventing reflux?

A

Lower oesophageal sphincter
Acute angle of entry of oesophagus into stomach
Mucosal folds at oesophagogastric junction that act as a valve
Positive intra-abdominal pressure compresses the walls of intra-abdominal oesophagus

51
Q

What are the divisions of the stomach?

A 
Cardia
Fundus 
Body 
Pyloric antrum 
(CFBP - Cats frequently bring prey)
52
Q

Where does chyme pass after the pyloric antrum?

A

Plyoric antrum narrows to form pyloric canal

Distal end of the pyloric canal muscle thickens to form pyloric sphincter, which controls passage into duodenum

53
Q

How do gallstones affect the duodenum?

A

Gallstones can cause erosion from gallbladder to superior (1st) part of duodenum
Cholecysto-duodenal fistula forms, allows gallstones into the bowel and gas into the billary tree
Gallstone can get stuck at distal ileum, leading to gallstone ileus

54
Q

What can ulcers in the duodenum lead to?

A

Anterior ulcer - perforation causes peritonitis
Posterior ulcer - erode into gastroduodenal artery, causing massive haemorrhage due to profuse arterial network in the region. Or into pancreas, causing severe pain that radiates to the lumbar region.

55
Q

Describe the layout of the duodenum

A

C shape that wraps around the head of the pancreas, divided into 4 sections

56
Q

Describe the superior duodenum

A

L1
Ascends upwards from the pylorus
Connected the liver by the hepatoduodenal ligament
Initial part covered by visceral peritoneum, rest is retroperitoneal (only covered anteriorly)

57
Q

Describe the descending duodenum

A

L1-L3
Curves inferiorly around the head of the pancreas
Anterior to right kidney
Posterior to transverse colon

58
Q

What is the duodenal papilla and where is it found?

A

An opening for bile and pancreatic secretions from the ampulla of Vater to enter the descending duodenum, guarded by the sphincter of Oddi

59
Q

Where is the transition from embryonic foregut to midgut and what is the significance of this?

A

Occurs at duodenal papilla
Means the duodenum has blood supplies from the celiac access (foregut, branch of abdominal aorta) and the superior mesenteric artery (midgut)

60
Q

What does an ulcer in the descending duodenum suggest?

A

Pancreatic disease

Zollinger-Ellison syndrome (tumour secreting gastrin)

61
Q

Describe the inferior duodenum

A

L3
Anterior to IVC and aorta
Inferior to pancreas
Posterior to superior mesenteric artery and vein

62
Q

What is significant about the proximity of the aorta and the descending duodenum?

A

Inflammation of aorta/duodenum can lead to fistula forming, presenting as an upper GI haemorrhage

63
Q

Describe the ascending duodenum

A

L3-L2
Curves anteriorly to join the jejunum at the duodenojejunal flexure (sharp turn)
Has mesentery, becomes intraperitoneal

64
Q

Define mesentery

A

Double folds of peritoneum that suspend the gut from the abdominal wall

65
Q

Define omentum

A

Specialised region of peritoneum

66
Q

What is the suspensory muscle of the duodenum?

A

Slip of muscle at the duodenal junction, contraction of it widens the angle of flexion, aiding in movement of intestinal contents into the jejunum

67
Q

Why do infections in the vagina rarely lead to peritonitis despite the open peritoneal cavity providing a pathway?

A

Mucous plug in external os (opening) of uterus prevent pathogens from entering uterus

68
Q

Where does the jejunum begin?

A

The duodenojejunal flexure

69
Q

Where does the ileum end?

A

Ileocecal junction

70
Q

How is reflux from the cecum back to ileum prevented?

A

The ileocecal valve, where the ileum invaginates into the cecum

71
Q

What are the differences between the jejunum and the ileum?

A

J: Located upper left quadrant I:Lower right quadrant
J:Thick intestinal wall I:Thin intestinal wall
J:Long vasa recta I:Short vasa recta
J: Less arcades (arterial loops) I: More arcades
J: Red I:Pink

72
Q

Describe the development of the oesophagus

A

4 weeks - respiratory diverticulum appears at ventral wall of foregut
Tracheoesophageal septum divides diverticulum into ventral (respiratory primordium) and dorsal parts (oesophagus)

73
Q

What causes congenital hiatial hernias?

A

Oesophagus fails to lengthen and stomach is pulled into oesophageal hiatus through diaphragm

74
Q

What are the consequences of oesophageal atresia?

A

Normal passing of amniotic fluid prevented, accumulation of excess fluid in amniotic sac

75
Q

What causes oesophageal atresia and tracheoesophageal fistula?

A

Posterior deviation of tracheoesophageal septum, resulting in proximal oesophagus having a blind ending and distal o. is connectd to trachea by a narrow canal above bifurcation

76
Q

What are the consequences of the first rotation of the stomach?

A

Left side now anterior, right posterior
So L vagus nerve now innervates anterior wall
Original posterior wall, now right, grows much faster than anterior, forming greater and lesser curves
Dorsal mesogastrium pulled left, leaving space behind stomach - omental bursa forms from ventral mesogastrium
Ventral mesogastrium pulled right
Duodenum forms C shape and swings right

77
Q

What are the consequences of the second rotation of the stomach?

A

Pyloric part moves right and upwards
Cardiac part moves left and downward
Dorsal mesogastrium bulges down to form greater omentum

78
Q

Describe what derives from ventral mesogastrium

A

Peritoneum of liver
Falciform ligament, as liver grows into septum transversum - containing umbilical vein which after birth becomes round ligament
Lesser omentum and hepatoduodenal ligament (containing portal traid - hepatic artery, portal vein and bile duct). Also forms roof of epiploic foramen of Winslow

79
Q

What is the epiploic foramen of Winslow?

A

Opening connecting omentral bursa with rest of peritoneal cavity

80
Q

What are the borders of the epiploic foramen of Winslow?

A

Anterior: Lesser omentum free edge -duodenohepatic ligament containing portal triad
Posterior: IVC
Superior: Caudate lobe
Inferior: Duodenum

81
Q

Are the duodenum and head of the pancreas peritoneal or retroperitoneal?

A

Retroperitoneal
As stomach rotates, pushed against dorsal wall which fuses with their peritoneum
Duodenal cap is peritoneal

82
Q

What is a Meckel’s diverticulum?

A

A diverticulum (bulge) in small intestine due to incomplete obliteration of vitelline duct

GI (12 decks)

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