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ESA3 Harpreet :) > Gastrointestinal System > Flashcards

Gastrointestinal System Flashcards

1
Q

What is the composition of saliva? (5)

A
  • Mostly water in a hypotonic solution
  • Potassium and bicarbonate ions
  • Mucins
  • Digestive enzymes e.g. amylase, lingual lipase
  • Immune proteins e.g. lysozyme, lactoferrin
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2
Q

List 4 functions of saliva (4)

A
  • Lubrication and moistening of food to form a bolus
  • Solvent for taste molecules
  • Initiation of digestion of food
  • Oral hygiene (neutralises acidity on teeth)
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3
Q

Describe the appearance of the mouth of a patient with xerostomia (3)

A
  • Tongue appears red, swollen and sore
  • Mouth and lips appear dry
  • Poor oral hygiene
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4
Q

Where does the duct to the parotid salivary gland enter the oral cavity?

A

Opposite crown to the 2nd upper molar tooth

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5
Q

Describe the locations of the sublingual and submandibular salivary glands in relation to the floor of the mouth

A
  • Sublingual gland sits above the floor of the mouth

- Submandibular gland sits below the floor of the mouth

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6
Q

Which nerve innervates the parotid gland?

A

Glossopharyngeal nerve (cranial nerve IX)

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7
Q

Which nerve innervates the sublingual gland?

A

Facial nerve (cranial nerve VII)

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8
Q

Which nerve innervates the submandibular gland?

A

Facial nerve (cranial nerve VII)

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9
Q

Which gland can be affected by the mumps virus?

A

Parotid gland

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10
Q

What is a sialography and what is it used for?

A
  • Radiological investigation of salivary glands by means of injecting a contrast medium followed by X-ray
  • Used to investigate blockages by stones, presence of tumours etc.
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11
Q

Describe the events that occur in the oral preparatory phase of swallowing (2)

A
  • Voluntary manipulation of food into a bolus by the tongue (secretion of saliva helps to lubricate and moisten food)
  • Tongue pushes bolus towards the pharynx and pharyngeal phase begins
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12
Q

Describe the precautions taken in the pharyngeal phase of swallowing to ensure the bolus is sent down the correct passage (5)

A
  • Soft palate moves up to close off nasopharynx
  • Tongue moves up to block entrance to oral cavity
  • Pharyngeal sphincters constrict to push bolus down
  • Larynx moves up and epiglottis moves down to close of the glottis and entrance to the airways
  • Vocal chords close to close off airways
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13
Q

Describe the oesophageal phase of swallowing (2)

A
  • Opening of the upper oesophageal sphincter to allow bolus to enter oesophagus
  • Closure of sphincter and peristaltic waves allow bolus to be pushed down the oesophagus through contraction of the circular and longitudinal layers of the muscularis externa in the wall
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14
Q

Why can babies swallow and breathe at the same time?

A

Epiglottis extends up towards nasopharynx in babies allowing them to swallow and breathe whilst still protecting airways

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15
Q

Which 2 cranial nerves are involved in swallowing and the gag reflex? (2)

A
  • Glossopharyngeal nerve (IX)

- Vagus nerve (X)

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16
Q

What is dysphagia?

A

A condition in which the patient has difficultly swallowing

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17
Q

Give 3 possible causes of dysphagia (3)

A
  • Oesophageal tumour
  • Stroke
  • Bulbar palsy
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18
Q

Describe 3 ways in which gastro-oesophageal reflux is avoided (3)

A
  • Functional sphincter formed from the smooth muscle of the distal oesophagus to prevent acid reflux from stomach
  • Acute angle of entry of oesophagus into stomach makes reflux difficult and unlikely
  • Resting tone of diaphragm keeps oesophagus closed
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19
Q

Describe the structure of the oesophagus (5)

A
  • Upper oesophageal sphincter
  • 1/3 skeletal muscle
  • 1/3 skeletal and smooth muscle
  • 1/3 smooth muscle
  • Lower oesophageal sphincter
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20
Q

Describe the arterial blood supply to the stomach

A
  • Lesser curvature - left gastric (celiac trunk) and right gastric (common hepatic)
  • Greater curvature - left gastroepiploic (splenic) and right gastroepiploic (gastroduodenal)
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21
Q

Where is the arcuate line (Line of Douglas) positioned and what is its significance? (2)

A
  • 1/3 of the way down between umbilicus and symphysis pubis

- Site of Caesarian section

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22
Q

Describe the composition of the abdominal wall from external to internal

A

Skin/subcutaneous tissue; superficial and deep fascia; external oblique; internal oblique; transversalis abdominus; transversalis fascia; peritoneumw

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23
Q

Describe the sheathing of the rectus abdominus muscle

A
  • Above umbilicus: sheathed anteriorly and posteriorly

- Below umbilicus: sheathed anteriorly only

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24
Q

Describe the direction of the muscle fibres in the external oblique, internal oblique and transversalis abdominus muscles (3)

A
  • External oblique: fibres run inferiomedially
  • Internal oblique: fibres run superiomedially
  • Transversalis abdominus: fibres run anterioposteriorly
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25
Q

What is the main cause of a diavarication of recti?

A

Laxity of the linea alba (NOT A HERNIA)

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26
Q

Describe how you could test the strength of the rectus abdominus muscle

A

Ask patient to lie flat and lift head off the floor, then lift feet off the floor

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27
Q

Where is the main site for an appendicectomy located?

A
  • McBurney’s point

- 2/3 of the way between the umbilicus and the right ASIS

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28
Q

What is a gridiron incision?

A
  • Made at McBurney’s point for an appendicectomy
  • In the direction of the muscle fibres of the external oblique muscle (separate the muscle fibres and go in between them)
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29
Q

What is referred pain?

A

Pain perceived at a site distant from the site causing the pain

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30
Q

What is somatic referred pain?

A

Pain caused by a noxious stimulus to the proximal part of a somatic nerve which is perceived in the distal dermatome of the nerve

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31
Q

Name 4 causes of visceral pain in the abdomen (4)

A
  • Ischaemia
  • Abnormally strong muscle contractions
  • Inflammation
  • Stretch
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32
Q

Where is visceral pain normally distributed? (3)

A
  • Epigastric region (foregut)
  • Periumbilical region (midgut)
  • Suprapubic region (hindgut)
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33
Q

What is a hernia?

A

Protrusion of part of the abdominal contents beyond the normal confines of the abdominal wall/its containing cavity

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34
Q

What does a hernia consist of? (3)

A
  • The sac (peritoneum)
  • Coverings of the sac (layers of abdominal wall)
  • Contents of the sac (abdominal viscus)
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35
Q

What is the inguinal canal and what structures pass through it? (3)

A
  • Oblique passage through the lower part of the abdominal wall
  • Spermatic cord (M), round ligament of uterus (F) and ilioinguinal nerve pass through here, along with other structures
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36
Q

Where does the the round ligament of the uterus run in females?

A

From the uterine horns in the parametrium, it enters the pelvis via the deep inguinal ring, passes through the inguinal canal to the labia majora

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37
Q

Where does the inguinal ligament run in relation to the external oblique muscle?

A

Runs inferomedially from the ASIS to the pubic tubercle, forming the free edge of the external oblique muscle

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38
Q

What forms the superficial inguinal ring?

A

External oblique aponeurosis (thickened medially and laterally by crura)

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39
Q

What is the conjoint tendon?

A

Merged fibres of the internal oblique and transverse abdominus muscles at the pubic tubercle which reinforces the inguinal canal medially

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40
Q

What forms the deep inguinal ring?

A

Transversalis fascia at the midpoint of the inguinal ligament

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41
Q

What forms the floor of the inguinal canal?

A

Inguinal ligament (+ lacunar ligament medially)

42
Q

What forms the anterior wall of the inguinal canal?

A

External oblique aponeurosis

43
Q

What forms the posterior wall of the inguinal canal?

A

Transversalis fascia (+ conjoint tendon medially)

44
Q

What forms the roof of the inguinal canal?

A

Internal oblique and transverse abdominus muscle fibre arches + associated aponeuroses

45
Q

What is the most common type of abdominal hernia?

A

Indirect inguinal hernia (M>F 7:1), mainly right sided

46
Q

Describe the difference in the location of the deep inguinal ring and the femoral artery

A
  • Deep inguinal ring - midpoint of the inguinal ligament, between ASIS and pubic tubercle
  • Femoral artery - mid inguinal point, between the ASIS and the symphysis pubis
47
Q

Explain the significance of the inferior epigastric vessels as a landmark for inguinal hernias

A
  • Indirect inguinal hernias form LATERAL to the inferior epigastric artery and vein
  • Direct inguinal hernias form MEDIAL to the inferior epigastric artery and vein
48
Q

Describe the path of an indirect inguinal hernia

A
  • Enters inguinal canal through deep inguinal ring, lateral to the inferior epigastric vessels, and protrudes out of the superficial inguinal ring
  • Can progress to the scrotum depending on where the processus vaginalis was obliterated
49
Q

Describe the path of a direct inguinal hernia

A

Protrudes through HESSELBACH’S TRIANGLE, generally in the vicinity of the superficial inguinal ring, medial to the inferior epigastric vessels

50
Q

What are the borders of Hesselbach’s Triangle? (3)

A
  • Lateral: Rectus abdominus
  • Superomedial: inferior epigastric artery and vein
  • Inferomedial: inguinal ligament (+ lacunar ligament)
51
Q

Why does a direct inguinal hernia not usually progress to the scrotum?

A

Does not pass through the inguinal canal

52
Q

Why is a femoral hernia more common in females?

A

Angle of pelvis is wider than males (childbirth)

53
Q

Explain why a femoral hernia is more common to strangulation than other hernias

A

Borders of the femoral canal are tight (not lax) so can cut off blood supply to the section of herniated bowel

54
Q

Where does a femoral hernia pass?

A

Through the femoral ring and into the femoral canal, out through the saphenous opening (can get trapped beneath the inguinal ligament -> strangulated hernia)

55
Q

What is the difference between omphalocele and gastroschisis?

A
  • Both occur due to defects in the anterior abdominal wall resulting in abdominal contents herniating out of the body cavity
  • Omphalocele is similar to an umbilical hernia and bowel is usually covered with umbilical cord/visceral peritoneum, whereas in gastroschisis the bowel is uncovered
56
Q

Explain the difference between an infant and adult umbilical hernia

A
  • Infant: contents herniates through weakness in scar of umbilicus
  • Adult: contents herniates through weakness in the linea alba in the region of the umbilicus (para-umbilicus)
57
Q

Where does an epigastric hernia occur?

A

Through the linea alba between the xiphoid process and the umbilicus (usually fat, but chronic straining forces can eventually pull peritoneum through)

58
Q

What is meant by ‘reduction’ of a hernia?

A

Hernia can be pushed back into the containing body cavity

59
Q

When does a hernia become incarcerated and what is a possible consequence of this? (2)

A
  • Hernia becomes STUCK or is IRREDUCIBLE

- Can lead to STRAGULATION

60
Q

What is strangulation and what are its consequences?

A
  • Blood supply cut off to an incarcerated hernia leading to bowel ischaemia
  • Can eventually lead to necrosis (infarction) of herniated bowel
61
Q

What is the difference between a ‘sliding’ hiatus hernia and a ‘rolling’ hiatus hernia?

A
  • Sliding: gastro-oesophageal junction may slide through diaphragm into the chest cavity
  • Rolling: part of the fundus of the stomach may slide through diaphragm into the chest alongside the oesophagus
62
Q

What is the main predisposition to diaphragmatic hernias?

A

Developmental defects in the diaphragm muscle which allow any viscus to herniate into the chest cavity

63
Q

What is the blood supply to the fundus of the stomach?

A

Small gastric arteries which branch from the splenic artery

64
Q

Which arteries supply the lesser curvature of the stomach?

A
  • Right gastric (branch of common hepatic)

- Left gastric (branch of celiac trunk)

65
Q

Which arteries supply the greater curvature of the stomach?

A
  • Right gastroepiploic (branch of gastroduodenal)

- Left gastroepiploic (branch of the splenic)

66
Q

What is the function of rugae?

A

Non-permanent folds in the mucosa/submucosa which allow distension of the stomach so it can hold large volumes of food

67
Q

Describe the arrangement of the stomach glandular structures microscopically

A
  • GASTRIC PITS

- Continuous with gastric glands and contain specialised cells for the function of the stomach

68
Q

What is the function of the muscularis externa of the stomach?

A
  • Provides smooth contractions which mix and grind the contents of the stomach
  • Move contents of stomach along to the pyloric sphincter
69
Q

Describe how the contractions of the upper stomach aid in the transport of contents along the stomach (2)

A
  • Fundus produces sustained contractions

- Creates a basal tone so the general direction of flow continues down the tube

70
Q

Describe the muscular contractions of the lower stomach and how this helps in the transport of chyme into the duodenum (2)

A
  • Strong peristaltic waves (proximal to distal) in antrum and pylorus to accelerate contents towards pyloric sphincter in a coordinated movement
  • Large lumps get left behind so only small particles and water can pass through to the duodenum
71
Q

Explain how the shape of the stomach aids in its function (2)

A
  • Larger (proximal) to smaller (distal) so allows acceleration of contents along the tube to the pyloric sphincter
  • Large lumps are left behind and liquid chyme passes into duodenum ~3 times per min
72
Q

Explain the mechanisms by which the stomach is able to store food and the importance of this (3)

A
  • Receptive relaxation of the orad stomach as food enters fundus from oesophagus (stomach dilates to avoid rise in intragastric pressure)
  • Gastric mucosal folds (rugae) allow stomach distension
  • Maintenance of intragastric pressure prevents reflux of stomach contents during swallowing
73
Q

Give 3 reasons why the stomach contents needs to be acidic (3)

A
  • Allows unravelling/breakdown of proteins
  • Activation of proteases e.g. Pepsinogen
  • Disinfection (kills bacteria)
74
Q

Which cells secrete acid (HCl) into the stomach?

A

Parietal cells in the gastric pits

75
Q

Describe the mechanism by which parietal cells produce an acidic environment within the stomach (2)

A
  • Hydrolysis of water in mitochondria produces H+ and OH-

- OH- combines with CO2 to produce HCO3- which is secreted into the blood (alkaline tide) leaving H+ in the stomach

76
Q

Explain the role of the ‘alkaline tide’ (2)

A
  • HCO3- produced in the stomach is secreted into blood

- Re-secreted into the duodenum from the liver and pancreas to neutralise the acidic chyme leaving the stomach

77
Q

Name 3 substances that stimulate parietal cells to secrete acid

A
  • Gastrin
  • Acetylcholine
  • Histamine
78
Q

Where is histamine secreted from in the stomach and what is its main role? (2)

A
  • Released from enterochromaffin-like cells (ECL, mast cells)
  • Acts on H2 receptors on parietal cells to stimulate acid secretion
79
Q

What is the role of chief cells?

A

Release of protease Pepsinogen into stomach which is cleaved by HCl into PEPSIN - digestion of proteins into amino acids

80
Q

Describe the cell distribution through the stomach (3)

A
  • Cardia: predominantly mucus-secreting cells
  • Fundus/body: parietal cells, chief cells, mucous cells
  • Pylorus: G cells, D cells
81
Q

What is the role of G cells?

A

Release of gastrin hormone which stimulates acid secretion from parietal cells

82
Q

What is the role of D cells and where are they located? (2)

A
  • Release of somatostatin which inhibits acid secretion via negative feedback
  • Pyloric region of stomach
83
Q

Describe how gastrin acts in parietal cells to stimulate acid secretion

A

Released from G cells and acts on CCK receptors on parietal cells to stimulate release of H+ into stomach lumen

84
Q

Describe 3 ways parietal cells can be stimulated to secrete H+ (3)

A
  • Binding of Gastrin (from G cells) to CCK receptors
  • Binding of Histamine (from enterochromaffin-like cells) to H2 receptors
  • Binding of Ach (from parasympathetic nerves) to muscarinic (M1) receptors
85
Q

What stimulates gastrin secretion? (2)

A
  • Vagal stimulation (release of Ach and GRP)

- Presence of peptides/AA in stomach lumen

86
Q

How does somatostatin inhibit acid secretion? (3)

A
  • As stomach empties, pH drops which stimulates D cells in antrum to release somatostatin
  • Binds to S receptors on G cells inhibiting gastrin secretion and enterochromaffin-like cells inhibiting histamine secretion
  • Gastrin and histamine therefore cannot bind to parietal cells and stimulate H+ secretion
87
Q

Which channel do proton pump inhibitors act on?

A

H+/K+ ATPase on parietal cells, inhabiting acid secretion into stomach lumen

88
Q

Explain how HCl is formed in parietal cells (2)

A
  • Hydrolysis of water forms H+ and OH- ions
  • OH- + CO2 (catalysed by carbonic anhydride) makes HCO3- which is transported out of the cell into the blood in exchange for Cl- via an anion exchanger (alkaline tide)
  • (H+ + Cl- -> HCl)
89
Q

Explain what occurs during the cephalic phase of digestion (2)

A
  • Sight/smell/taste/swallowing of food stimulates vagus nerve
  • Parasympathetic stimulation triggers release of Acetylcholine and GRP which stimulates G cells
90
Q

Describe how food acts as a buffer during the gastric phase of digestion

A

Balances pH by buffering acidic conditions of the stomach thereby removing inhibition of gastrin secretion

91
Q

Describe the gastric phase of digestion (3)

A
  • Food buffers acidity of stomach thereby disinhibiting gastrin hormone secretion
  • Acids and proteases break down proteins into peptides/AA, the presence of which further stimulate gastrin secretion from G cells
  • Distension of the stomach stimulates vagus nerve via stretch receptors so increases parasympathetic stimulation
92
Q

Describe the intestinal phase of digestion (3)

A
  • Chyme detected in the duodenum signals for decrease in rate of digestion by inhibition of G cells (as food leaves pH drops)
  • Presence of lipids stimulates enterogastric reflex which reduces vagal stimulation to the stomach
  • Release of hormones from intestines such as CCK and GIP act to reduce acid secretion
93
Q

Name 2 defence mechanisms of the stomach to protect against its acidic conditions

A
  • Thick layer of alkaline mucus produced by mucus secreting cells which traps H+ ions and protects mucosa
  • HCO3- ions secreted from mucous cells reacts with H+ to neutralise acid
94
Q

Which hormone stimulates the stomach defences?

A

Prostaglandins

95
Q

Name 3 things which can disrupt the stomach’s defences and lead to gastritis/ulceration (3)

A
  • Alcohol (excess ingestion)
  • Helicobacter Pylori infection
  • NSAIDS
96
Q

Describe how NSAIDS may lead to gastritis

A
  • Inhibition of cyclo-oxygenase enzyme which is required for the production of prostaglandins
  • Prostaglandins are required for the defence of the stomach mucosa so lack of these can leave stomach vulnerable to damage from acid, leading to inflammation of the mucosa
97
Q

Describe 3 ways in which prostaglandins affect the stomach (3)

A
  • Inhibit acid secretion from parietal cells
  • Stimulate mucus and HCO3- secretion from mucus cells
  • Maintain mucosal blood flow to provide nutrients to mucosal cells
98
Q

What property of gastric mucosal cells can help in preventing gastric ulceration?

A

High cell turnover rate so rate of renewal exceeds rate of damaged, thereby preventing ulceration

99
Q

Describe how excess alcohol ingestion can lead to gastritis

A

Alcohol dissolves the mucus layer in the stomach leaving the mucosa vulnerable to the acidic conditions of the contents

100
Q

Describe how Helicobacter Pylori can lead to ulceration of the stomach mucosa

A

Causes CHRONIC active inflammation of the stomach mucosa leading to gastritis and potentially ulceration

101
Q

Name 2 drugs which can be used to reduce acid secretion in the stomach and state their action (2)

A
  • Cimetidine (H2 channel antagonist)

- Omeprazole (H+/K+ ATPase antagonist)

ESA3 Harpreet :) (5 decks)

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