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Gastrointestinal System > 1. Broad Overview > Flashcards

1. Broad Overview Flashcards

1
Q

What is the order of the alimentary canal?

A
  • Mouth
  • Oesophagus
  • Stomach
  • (Pancreas)
  • Small intestine
    • Duodenum
    • Jejunum
    • Ileum
  • Large intestine
    • ​Cecum
    • Ascending colon
    • (Left colic/hepatic flexture)
    • Tranverse colon
    • (Right colic/hepatic flexture)
    • Descending colon
    • Sigmoid colon
  • Rectum
  • Anal sphincter
  • Anus
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2
Q

What is the broad function of the mouth in the alimentary canal?

A
  • Mainly mechanical disruption of macromolecules from mastication
  • Secretion of saliva and enzymes
    • minimal chemical breakdown
    • aids lubrication and swallowing
  • Infection control
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3
Q

What is the broad function of the oesophagus in the alimentary canal?

A
  • Rapid transport of bolus and peristalsis
  • Upper Oesophageal Sphincter: prevents air from entering the GI tract
  • Lower Oesophageal Sphincter: helps prevent reflux into the oesophagus
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4
Q

What is peristalsis?

A

The involuntary constriction and relaxation of the muscles of the intestine or another canal, creating wave-like movements which push the contents of the canal forward.

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5
Q

What is the broad function of the stomach?

A
  • Storage facility
  • Produces chyme
    • physical breakdown
    • chemical breakdown
    • digestion starts
  • Infection control (HCl)
  • Secretes intrinsic factor
    • vital for Vitamin B12 absorption
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6
Q

Draw out the anatomy of the stomach

A
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7
Q

What are the broad functions of the duodenum?

A
  • Start of small intestine, C-shaped
  • Neutralisation/osmotic stabilisation of chyme
    • HCO3 rich secretions
  • End of digestion
    • Pancreatic secretions
    • Bile is secreted
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8
Q

What are the broad functions of the jejunum and ileum?

A
  • Final stage of digestion

Jejunum

  • nutrient absorption

Ileum

  • Water and electrolyte absorption
  • Bile recirculation
  • B12 absorption in the terminal ileum
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9
Q

What is the broad function of the large bowel?

A
  • final stage of water absorption
  • temporary storage
  • final stage of electrolyte absorption
    • some bile salt absoprtion
    • production of short chain fatty acids
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10
Q

What is the function of the rectum and anus?

A

Defaecation

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11
Q

How is the gut controlled?

A
  • Autonomic nervous system
    • parasympathetic
    • sympathetic
  • Enteric nervous system
  • Hormones and paracine substances
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12
Q

Where do the cell bodies reside in the autonomic nervous system?

A

CNS

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13
Q

Where do preganglionic fibres synapse?

A

Outside the CNS

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14
Q

Where do post ganglionic fibres synapse?

A

Peripheral effector organs

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15
Q

What neurotransmitter does preganglionic fibres release?

A

Acetylcholine (cholinergic)

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16
Q

What neurotransmitters do post ganglionic fibres release?

A

Acetylcholine, neuropeptides or norepinephrine

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17
Q

What is a ganglion?

A

A collection of cell bodies outside the nervous system

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18
Q

Which neurones have a short preganglionic and long postganlionic neurone?

A

Sympathetic neurones

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19
Q

Which neurones have a long postganglionic and short preganglionic neurone?

A

Parasympathetic neurones

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20
Q

What feature do preganglionic neurones have that post ganglionic don’t?

A

They are myelinated

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21
Q

What does the enteric nervous system control?

A
  • Motor functions of the gut
  • Local blood flow
  • Secretions and transport along the mucosa
  • Immune function
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22
Q

Which muscles are involved in peristalsis?

A

Muscularis externa :

  • inner circular layer
    • contracts and constricts behind food
  • outer longitudinal layer
    • relaxes and lengthens pulling food forward
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23
Q

What are the four major layers of the gastrointestinal tract?

A
  • Adventita or Serosa
    • adventita = thick fibrous connective tissue
    • serosa = slippery serous membrane
  • Myenteric Plexus (Auerbach’s Plexus)
    • smooth muscle relaxation on activation
  • Muscularis Externa
  • Submucosa
    • ​contains Submucous plexus/meissner’s plexus
      • ​controls size of blood vessels and secretion of digestive fluids
  • Mucosa
    • ​muscularis mucosa: smooth muscle helps with break down of food
    • lamina propria: contains blood vessels and lymph
    • epithelial layer: absorbs and secretes mucus and digestive enzymes
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24
Q

What is the enteric nervous system made up of?

A
  • Submucosal/ Meissner’s plexus
  • Myenteric/ Auerbach’s plexus
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25
Q

What is another name for the submucosal plexus?

A

Meissner’s Plexus

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26
Q

Where is Meissner’s plexus found?

A

Inbetween the mucosa and submucosa

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27
Q

What is another name for the myenteric plexus?

A

Auerbach’s plexus

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28
Q

Where is Auerbach’s plexus found?

A

Within muscularis propria inbetween circular muscle and longitudinal muscle.

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29
Q

How is the gut controlled by the nervous system?

A
  • Enteric nervous system
  • Parasympathetic
  • Sympathetic
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30
Q

How does the parasympathetics act on the GI system?

A
  • Normally in the ‘on’ state; (rest and digest)
  • Craniosacral outflow
    • Vagus nerve (CNX)
      • supplies oesophagus - splenic flexure of large colon
      • stimulates smooth muscle contraction and secretions
    • Pelvic splanchnic nerves (S2-4)
      • peristalsis and contractions of bladder/rectum
31
Q

What do postganglionic fibres of the parasympathetic neurones release in the stomach?

A
  • Acetylcholine
  • Peptides
    • Gastrin releasing peptide
    • Vaso-inhibitory peptide
32
Q

Where do parasympathetic preganglionic fibres synapse?

A

Walls of the viscera

33
Q

What do parasympathetic neurones innervate?

A
  • Smooth muscle
  • Endocrine cells
  • Secretory cells
34
Q

How does the sympathetic nervous system act on the GI system?

A
  • Generally in the ‘off’ state (fight or flight)
  • Supplied by thoracolumbar region
    • T5-L2
  • Mainly innervates blood vessels but also inhibits peristalsis and secretions
35
Q

Where do the abdominopelvic presynaptic splanchnic nerves arise from?

A
  • Greater = T5-9
  • Lesser = T10-11
  • Least = T12
36
Q

Where do the splanchnic nerves synapse with?

A

Prevertebral ganglia; coeliac, renal, superior mesenteric and inferior mesenteric

37
Q

What is the pathways of the sympathetic preganglionic fibres?

A
  1. Thoracolumbar outflow
  2. Sympathetic chain (do not synapse within chain)
  3. Join with other preganglionic fibres to form splanchnic nerves
  4. Splanchnic nerves synapse on prevertebral ganglia
    • coeliac, superior mesenteric and inferior mesenteric
38
Q

Where do sympathetic postganglionic fibres extend from and to?

A

From prevertebral ganglia to viscera; myenteric and submucosal plexuses i.e. the enteric nervous system

39
Q

What is the enteric nervous system?

A

A division of the nervous system that has the ability to operate independantly but has extensive connections with the autonomic nervous system. It extends from the oesophagus to the anus and consists of two main plexuses; Meissner’s and Auerbach’s.

40
Q

How does enteric system communicate with other nervous systems?

A
  • Parasympathetic
    • vagus
    • pelvis nerves
  • Sympathetics
    • prevertebral ganglia
41
Q

What is the peritoneum?

A

Potential space between the parietal and visceral peritoneum.

42
Q

What lines the peritoneum?

A

Mesothelium; flatted simple squamous epithelium, basement membrane and dense irregular connective tissue.

43
Q

What are retroperitoneal viscera defined as?

A

Viscera that are not enveloped and lie posterior to peritoneal cavity.

44
Q

What are the retroperitoneal organs?

A

Suprarenal glands

Aorta/ inferior vena cava

Duodenum (2nd and 3rd segments)

Pancreas

Ureters

Colon (ascending and descending)

Kidneys

Eosophagus

Rectum

SAD PUCKER

45
Q

What is a mesentry?

A

A double fold of peritoneal tissue that suspends the large and small intestine from the posterior abdominal wall providing a conduit for vessels to reach organs.

46
Q

What does the peritoneal cavity normally contain?

A

A small smouth of serous fluid to aid with lubrication

47
Q

What are the two major divisions of the peritoneal cavity?

A

Greater and lesser peritoneal sacs

48
Q

What is the connection between the greater and lesser peritoneal sacs called?

A

Epiploic foramen of Winslow

49
Q

What are the boundaries of the lesser sac?

A

Anterior: Stomach and Greater omentum

Posterior: Parietal perintoneum, left kidney and pancreas

50
Q

Which peritoneal pouches in males can fluid accumulate in?

A

Rectovesical pouch and heptaorenal recess

51
Q

Which peritoneal pouches in females can fluid accumulate in?

A

Rectovesical, vesicouterine and hepatorenal pouch

52
Q

What are the signs and symptoms of peritonitis?

A
  • Sudden stomach pain worse on palpatation
  • Pyrexia
  • Tachycardia
  • Passing small amounts of urine or less frequently
  • Lack of appetite
  • Nausea
  • Swollen abdomen
53
Q

What is the basic layout of the parasympathetic nervous system and how does it relate to the gastrointestinal tract?

A
  • Normally activated = rest and digest
  • Craniosacral outflow
    • Vagus (CNX): controls contractions and secretions
    • S2, S3, S4: controls contractions and secretions
  • Preganglionic neurone is long and synapses with the postganglionic in the wall of the viscera
  • Ach and GRP are the postganglionic transmitters
  • Communicates with the enteric nervous system
54
Q

Which thoracic nerves from the greater splanchnic nerve and what part of the GI tract does it supply?

A

T5-T9

Feeds into the two coeliac ganglia which supply the foregut: stomach, liver gallbladder, pancreas and suprarenal glands

55
Q

What organs are found in the foregut?

A
  • Stomach
  • Liver
  • Pancreas
  • Suprarenal glands
  • Gallbladder
56
Q

Which thoracic nerves from the lesser splanchnic nerve and what does it supply?

A

T10-T11

Feeds into the aorticorenal ganglia which supplies the kidneys and ureters

57
Q

Which thoracic nerves form the least splanchic nerve and what does it supply?

A

T12, feeds into the renal plexus which partly supplies the kidneys and ureters

58
Q

How do the splanchnic nerves enter the abdomen?

A

Passes through the crus of the diaphragm

59
Q

What is the enteric nervous system?

A

A division of the nervous system that can operate independantly from the AND but has extensive connections to it.

60
Q

What are the two main plexuses of the enteric nervous system?

A
  • Meissener’s plexus (submucosal)
  • Aurbach’s plexus (myenteric)
    • inbetween circular and longitudinal muscle of muscularis propria
61
Q

What is the location of the enteric plexuses?

A

From the oesophagus to the anus

62
Q

What is the function of the enteric plexuses?

A
  • Submucosal - regulates blood flow and secretion
  • Myenteric - controls motility
63
Q

What is the relationship between the autonomic nervous system and the enteric nervous system?

A

Communications theough parasympathetic and sympathetic through;

  • vagus and pelvic nerves for parasympathetic
  • prevertebral ganglia for sympathetic
64
Q

In what section of the GI tract is the appendix located?

A

Caecum

65
Q

What is the major function of the colon?

A

Water absorption yet most of the water will have already been removed by the small intestine.

66
Q

What is the longest section of the GI tract?

A

Ileum

67
Q

Where is the digestive tract are digestive enzymes first secreted?

A

Oral cavity - salivary amylase and and lipase

68
Q

How do you identify the internal oblique muscle?

A

Fibres pass superiorly and medially and lies directly under the external oblique.

69
Q

What are the flat muscles of the abdominal wall?

A
  • External obliques
  • Internal obliques
  • Tranversus Abdominus
70
Q

Where do the majority of digestive enzymes enter the gastrointestinal tract?

A

Produced by the pancreas and released into the duodenum

71
Q

Where in the gut is vitamin B12 absorbed?

A

Terminal ileum

72
Q

Where do the parasympathetic pre-ganglionic fibres synapse in the gut?

A

Synapse in the wall of the innervated viscera, followed by a short post ganglionic neurone which sits within the wall of the viscera.

73
Q

Where do the sympathetic nerve fibres synapse for the gut?

A

The sympathetic outflow of the gut passes through the sympathetic chainh and then synapses with one of the pre-vertebral ganglia. Post ganglionic fibres are longer and extend to the walls of the viscera to innervate them.

74
Q

The term ‘cranio-scaral outflow’ refers to which part of the nerve supply to the gut?

A

Parasympathetic system. Comprised of; vagus nerve CNX and sacral nerves (S2-4)

Gastrointestinal System (3 decks)

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