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my phase 1 > Gastro > Flashcards

Gastro Flashcards

1
Q

how many salivary glands and their names

A

3 major pairs contribute to 80% of flow
parotid
submandibular
sublingual
- also minor glands located in the in the submucosa of cheeks, lips, tongue and soft and hard palate - contribute to 20% of flow.

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2
Q

which salivary glands are continuously active

A
  • sublingual
  • submandibular
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3
Q

where are the sublingual glands located

A

on the floor of the mouth between the mylohyoid muscles and the oral mucosa

and more anterior than the submandibular glands

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4
Q

structure and innervation of the sublingual gland

A

smaller than sublingual

  • saliva passes through Wharton’s duct

parasympathetic innervation by the chorda tympani branch of the facial nerve

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5
Q

role of para/sympathetic innervation in the salivary glands

A
  • Stimulation of parasympathetic nerves causes the production of a copious flow of saliva
  • sympathetic stimulation selectively causes secretion of protein and glycoprotein
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6
Q

structure and innervation of the submandibular glands

A
  • 2 lobes separated by the mylohyoid mucosa
    • larger superficial lobe and smaller deep lobe
  • saliva passes through Wharton’s duct
  • parasympathetic innervation by the chorda tympani branch of the facial nerve
  • sympathetic innervation from superior cervical ganglia
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7
Q

structure and innervation of the parotid glands

A
  • triangular gland located superficially between the zygomatic arch (cheekbone), sternocleidomastoid and ramus of the mandible.
  • drains into the parotid duct AKA stenson’s duct
  • enters oral cavity near the 2nd upper molar
  • parasympathetic innervation from CN9
  • sympathetic innervation from sympathetic ganglia, including the superior cervical ganglia.
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8
Q

what structures pass through the parotid gland

A
  • external carotid artery and its terminal branches
  • the retromandibular vein
  • the facial nerve and its 5 branches of the muscle of facial expression
    • temporal, zygomatic, buccal mandibular and cervical
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9
Q

where are minor glands found and how do they drain into the oral cavity

A
  • found in the submucosa of the Buccal labial, palatal and lingual regions of the mouth. Also found at:
    • superior pole of tonsils (Weber’s glands),
    • tonsillar pillars
    • base of the tongue (von Ebner’s glands - underlying circumvallate papillae).
  • they don’t have a branching network of draining ducts so each one has a simple duct.
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10
Q

which nerves are responsible for taste

A
  • facial nerve CN7 = anterior ⅔ of the tongue
  • glossopharyngeal CN9 = posterior ⅓ of tongue
  • Vagus nerve CN10 = pharynx
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11
Q

what types of secretions are there

A
  • mucous: mucins for lubrication of mucosal surfaces
  • serous: for α amylase secretions to break down starch
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12
Q

where is the main flow of saliva from

A
  • when unstimulated main flow of saliva comes from submandibular gland
  • when stimulated, parotid gland = main source of saliva
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13
Q

what type of saliva does each gland produce

A
  • parotid = serous
  • sublingual = mucous
  • submandibular = mixed
  • minor glands = All minor salivary glands are mucous except serous glands of von Ebner.
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14
Q

which gland is shown in each row

A
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15
Q

what are the main defences in the oral cavity

A
  1. saliva glands wash away particles which viruses and bacteria could feed on
  2. palatine tonsils provide immunological surveillance and resistance via
    • Lymphocyte subsets
    • Dendritic cells.
  3. mucosa provides a physical barrier
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16
Q

factors affecting the composition and amount of saliva produced

A
  • diet
  • drugs
  • age gender
  • duration of stimulus
  • circadian rhythm
  • type and size of gland
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17
Q

ideal pH and pH range in the mouth

A
  • Maintains pH at ~ 7.2 using a bicarbonate/carbonate buffer system to rapidly neutralise acids.
    • pH ranges from 6.2 – 7.4
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18
Q

components of whole saliva

A
  • Whole saliva = salivary gland secretions, blood, oral tissues, microorganisms and food remnants
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19
Q

what types of acini are these

A
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20
Q

two types of salivary ducts

A

intralobular

main excretory

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21
Q

3 main cell types within an intralobular duct

A

acinar cells

intercalated duct cell

striated cell

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22
Q

structure and function of the 2 main areas in an intralobular duct

A
  • Acini
    • Secretory cells
  • intercalated duct
    • these cells are cuboidal and attach the acini to the striated duct
  • striated duct
    • Microvilli – highly folded for active transport of HCO3- against the conc. gradient
    • Mitochondria → energy for active transport
    • HCO3- and K+ secreted
    • Na+ and Cl- absorbed
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23
Q

what is primary saliva

A

NaCl rich isotonic plasma like fluid secreted by the acini.

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24
Q

functions of saliva

A
  1. A lubricant for mastication, swallowing and speech.
  2. Oral hygiene by:
    • Physically washing the mouth
    • Having antibacterial, antiviral and antifungal properties.
  3. Maintains pH at ~ 7.2 using a bicarbonate/carbonate buffer system to rapidly neutralise acids.
  4. Begin digestion by carrying enzymes.
  5. Assists with taste as an aqueous solvent is needed.
  6. Dysfunction associated with oral pain, infections and ­ risk of caries.
  7. Production of secretions:
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25
Q

what are the main stages of swallowing

A
  1. oral = chewing and movement into pharynx
  2. pharyngeal = movement from pharnx into oesdophagus
  3. oesophageal = movement into oesohpagus and stomach
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26
Q

describe the stages of swallowing

A
  1. oral phase - voluntary
    1. prep: mastication and food mixes with saliva to form a bolus
    2. transfer:
      • Food is compressed against the roof of the mouth and is pushed to the oropharynx by the tongue.
  2. pharyngeal phase - involuntary
    • tongue seals off the oropharynx so food doesn’t reenter the mouth
    • The nasopharynx closes off due to soft palate elevation.
    • The trachea is closed off by the epiglottis.
    • the larynx is covered by the arytenoids
    • Elevation of the hyoid bone shortens and widens the pharynx.[suprahyoids]
  3. oesophageal phase: - involuntary
    • The pharyngeal constrictor muscles sequentially contract producing peristaltic waves.
    • This propels the bolus of food down the Oesophagus.
    • This is followed by depression of the hyoid bone [infrahyoids]
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27
Q

key muscles involved with swallowing

A
  • pharyngeal constrictor muscles: superior, middle and inferior.
    • constrict one after the other to push food down thepharynx and into the oesophagus
  • smooth muscle of the digestive tract responsible for peristalsis
  • suprahyoid muscles and longitudinal pharyngeal muscles:
    • lift the larynx to meet the epiglottis and close the trachea opening.
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28
Q

nerves involved in swallowing

A
  • vagus
  • hypoglossal
  • glossopharyngeal
  • accessory
  • trigeminal
  • facial
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29
Q

what is the rectus sheath formed from

A

the aponeurosis of the external oblique, internal oblique and transversus abdominis

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30
Q

name the muscles of the abdomen

A
  • rectus abdominis
  • internal oblique
  • external oblique
  • transversus abdominis
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31
Q

what are the bony landmarks of the abdomen

A
  1. xiphoid process
  2. ASIS
  3. pubic symphisis
  4. iliac crest
  5. costal margin
  6. pubic tubercle
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32
Q

name the 9 regions of the abdomen

A

suprapubic = hypogastric

lumbar = flank = loin

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33
Q

where/what is McBurney’s point

A
  • ⅔ of the way along a line joining the umbilicus to the right ASIS
  • this is the usual site of the base of the appendix and can be used to guide the position of the caecum in a clinical exam.
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34
Q

where/ what is the transpyloric plane of addison

A
  • the first horizontal plane dividing the top 2 rows of the 9 abdominal regions.
  • reaches the tip of the 9th costal cartilage and at the most lateral point of the rectus sheath.
  • at the level of L1
  • 4 structures lie on this plane:
    • the pancreas
    • the gall bladder
    • the pylorus of the stomach
    • the duodeno-jejunal flexure
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35
Q

what is the intertubercular plane and what does it mark

A

the plane at the level of the iliac crests.

marks the bifurcation of the abdominal aorta

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36
Q

what does the abdominal aorta divide into

A

the left and right common iliac arteries and the median sacral artery

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37
Q

where/ what is the intercristal plane

A

the plane lying at the highest point of the pelvis on the back.

cannot be palpated

used examinations and procedures on the back. [intertubercular is used for the front]

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38
Q

what is the surface marking of the abdominal aorta bifurcation

A

intertubercular plane - lying on the iliac crests

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39
Q

in which region of the abdomen is pain from the 3 parts of the bowel felt

A
  • foregut pain = the epigastrium - the midline at the level of T5-T9
  • midgut pain = periumbilical region
  • hindgut pain = supra pubic area

essentially pain is felt at the midline at the level of the gut region’s innervation.

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40
Q

describe the anatomy os a 6 pack

A
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41
Q

what is the upper boundary of the abdomen

A

the diaphragm

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42
Q

what covers the abdomen

A

the peritoneum

  • 2 continuous layers:
    • visceral: covers the organs
    • parietal covers the abdomen wall
  • the potential space between the 2 layers = the peritoneal cavity
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43
Q

what is the peritoneal cavity

A

the potential space between the parietal and visceral peritoneum

contains a layer of mucous to allow the viscera to slide freely over eachother

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44
Q

what is ascites

A

distension of the abdomen caused by fluid in the peritoneal cavity

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45
Q

main difference between the parietal and visceral peritoneum - other than what they cover

A
  • their nerve supplies particularly for pain perception
    • visceral receives the same autonomic innervation as the viscera it covers and has poorly localised pain and is mostly sensitive to stretch.
    • parietal receives the same somatic nerve supply as the area of abdomen it covers. Therefore pain is well localised
      *
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46
Q

functions of the colon

A
  • Absorption of water and electrolytes
  • Production of vitamins via fermentation of complex polysaccharides by the guts microbiota.
    • The vitamins produced are non-essential.
  • passage of waste for excretion
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47
Q

what are the ligaments of the liver and what are they made of

A

made of double layer of peritoneum

  • falciform ligament
  • right triangular ligament
  • left triangular ligament
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48
Q

can the liver be palpated trans-abdominally in a healthy pt

A

the left lobe of the liver lies above the costal margin so no

the right lobe runs parallel to the costal margin so may be palpated in slim pts only on deep inspiration.

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49
Q

what is ligamentum teres

A

a remnant of the umbilical vein. found on the free edge of the falciform ligament

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50
Q

what is the falciform ligament where does it attach to and what does it demarcate

A

a double layer of peritoneum

attaches the anterior surface of the liver to the anterior abdominal wall

position on the liver demarcates the anatomical right and left lobes of the lover

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51
Q

what lies deep to the left lobe of the liver and inferior to the right lobe

A
  • the stomach lies deep to the left lobe
  • the gall bladder is inferior to the right lobe
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52
Q

what is the lesser omentum made of, what does it carry and where is it located

A
  • thin fatty sheet of peritoneum
  • contains blood vessels and nerves
  • attaches the liver to the lesser curve of the stomach
  • extends from the diaphragm, next to the oesophagus to the first part of the duodenum -
    • free edge = the porta hepatis [portal triad]
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53
Q

what is the portal triad and where is it found

A

3 major vessels

  • portal triad
  • hepatic artery
  • bile duct

found in the free edge of the lesser omentum

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54
Q

what is the porta hepatis

A
  • this is a fissure running into the liver carrying the portal triad
    • the portal vein
    • the hepatic artery
    • bile duct
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55
Q

where is the spleen located

A

far left above the ribcage and lateral to the stomach

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56
Q

can the spleen be palpated in healthy pts

A

no as it lies above the costal margin

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57
Q

what is the spleen attached to and what attaches it

A
  • the greater curve of the stomach and the posterior abdominal wall
  • the greater omentum
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58
Q

what is the greater omentum, where does it attach and what is its function

A
  • fatty double fold of peritoneum
  • attaches from the greater curve of the stomach and the proximal duodenum and extends down and folds posteriorly then ascends to attach to the under surface of the diaphragm + retro-peritoneum
  • helps prevents the parietal and visceral peritoneum from attaching to eachother
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59
Q

what is the greater sac

A

the main peritoneal cavity

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60
Q

what is the lesser sac and how is it accessed

A

a peritoneal space that lies directly behind the stomach accessed via the epiploic foramen

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61
Q

what is mesentery and whats it made of

A

The mesentery is an organ that attaches the intestines to the posterior abdominal wall in and is formed by the double fold of peritoneum

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62
Q

which parts of the bowel have mesentery

A

the small bowel - jejunum and ileum

the transverse colon

the sigmoid colon

appendix

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63
Q

what is the function of mesentery

A
  • it suspends the the SI and parts of the colon from the posterior abdominal wall and anchors them in place - allows some movement of some organs.
    • the mesentery of the small intestine, transverse colon and sigmoid colon and appendix completely suspend these organs in the peritoneum thus they are intraperitoneal and mobile
    • the ascending and descending colon are are only covered by visceral peritoneum on their anterior surface so a retroperitoneal.
  • provides a passageway for blood vessels lymph vessels and nerves
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64
Q

which organs are mobile and which are fixed to the posterior wall

A
  • mobile
    • transverse colon
    • sigmoid colon
    • appendix
    • small intestines
  • fixed
    • ascending colon
    • descending colon
    • rectum
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65
Q

describe the order of the intestines and colon

A

duodenum → jejunum →ileum → ileo-caecal sac → [appendix on lower part of caecum] → caecum → ascending colon → hepatic flexure → transverse colon → splenic flexure → descending colon → sigmoid colon → rectum.

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66
Q

where does bacteria tend to gravitate to in the abdomen

A

the lowest space in the abdomen

  • behind the right lobe of the liver when lying flat
  • into the pelvis when upright
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67
Q

what is peritoneal dialysis and how is it possible

A

this is filtration of waste products out of the blood through the peritoneum

possible because the peritoneum is semi-permeable and doesnt allopw large molecules through such as proteins

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68
Q

which parts of the adomen are mobile

A
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69
Q

what is the function of mesentery

A
  • it suspends the the SI and LI from the posterior abdominal wall and anchors them in place - allows some movement of some organs.
  • provides a passageway for blood vessels
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70
Q

what does the lesser omentum carry

A

the portal triad vessels

hepatic artery, portal vein and bile duct

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71
Q

where is the pancreas located

A

behind the stomach and the lesser sac, retroperitoneal

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72
Q

what makes up the gastric bed and where is it located?

A
  • pancreas, splenic artery and part of the duodenum
  • located behind the lesser sac of the omentum
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73
Q

how might a stomach tumour spread

A
  • via the lymphatics around the coeliac axis
  • via the veins passing to the liver
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74
Q

what is a peptic ulcer

A

a breach in the mucosa and gastric wall of the stomach

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75
Q

which artery supplies the fore gut

A

the coeliac trunk

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76
Q

where does the coeliac trunk branch off and what structures does it supply

A
  • branches at the anterior of the aorta just below the diaphragm
  • supplies:
    • the lower ⅓ of the oesophagus
    • the stomach
    • the first and second parts of the duodenum
    • the liver
    • the pancreas
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77
Q

describe the innervation of the foregut

A
  • sympathetic innervation from the greater splanchnic - T5-T9
  • parasympathetic innervation from anterior and posterior vagal trunks
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78
Q

draw and name the parts of the stomach

A
  • fundus
  • antrum
  • body
  • pylorus
  • cardia
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79
Q

how are the portal triad vessels arranged

A

the hepatic artery has the bile duct to the right of it and the portal vein behind them

80
Q

describe the inner membrane of the stomach

A

rugae

81
Q

name a common site for peptic ulcers to occur and what is the consequence

A

the posterior wall of the first part of the duodenum

if the ulcers erodes through it can rupture part of the gastroduodenal artery → brisk bleed

82
Q

what are the borders of the lesser sac

A

the greater and lesser omentum AND the caudate lobe of the liver.

83
Q

at what vertebral level does the oesophagus pass through the diaphragm and what structures pass with it

A

T10 -

I 8 10 EGGS AT 12

I 8 - IVC crosses the diaphragh at the level of T8

10 EGGs - EsophaGus + vaGus cross the diaphragh at the level of T10

AT 12 - Aorta + Azygos vein + Thoracic duct cross the diaphragm at the level of T12

84
Q

what is a porto-systemic anastomosis

A

communication between the portal venous system and the systemic venous system, via the veins of the oesophagus and bypassing the liver

85
Q

what are the boundaries of the foregut, midgut and hind gut,

  • their arterial supply
  • venous drainage
  • innervation
A
  • foregut = lower ⅓ of the oeasophagus → proximal half of duodenum
    • coeliac trunk
    • splenic vein
    • Greater splanchnic nerve sympathetic T5-T9
      • vagus sympathetic
  • mid gut = distal half of duodenum → ⅔ of the transverse colon
    • superior mesenteric artery
    • superior mesenteric vein
    • lesser splanchnic sympathetic T10-T11
      • vagus sympathetic
  • the hind gut = the distal third of the transverse colon → upper third of the anal canal
    • inferior mesenteric artery
    • inferior mesenteric vein
    • least splanchnic para T12
      • pelvic splanchnic sympathetic
86
Q

name the 3 main branches of the coeliac trunk and what they supply

A
  • left gastric artery
    • lesser curve of the stomach
    • lower third of the oesophagus
  • common hepatic artery
    • liver
    • gall bladder
    • stomach
    • duodenum
    • pancreas
  • splenic artery
    • spleen
    • stomach
    • pancreas
87
Q

which organs are retroperitoneal

A
  • supra-renal adrenal glands
  • aorta and IVC
  • duodenum - first third
  • pancreas
  • ureters
  • colon - ascending and descending
  • kidneys
  • oesophagus
  • rectum
88
Q

draw and label the coeliac axis

A
89
Q

what level is the coeliac trunk located

A

T12

90
Q

describe the parts of the pancreas

A
  • Head – the widest part of the pancreas. It lies within the C-shaped curve created by the duodenum and is connected to it by connective tissue.
  • Uncinate process – a projection arising from the lower part of the head and extending medially to lie beneath the body of the pancreas. It lies posterior to the superior mesenteric vessels.
  • Neck – located between the head and the body of the pancreas. It overlies the superior mesenteric vessels which form a groove in its posterior aspect.
  • Body – centrally located, crossing the midline of the human body to lie behind the stomach and to the left of the superior mesenteric vessels.
  • Tail – the left end of the pancreas that lies within close proximity to the hilum of the spleen. This is the only part of the pancreas that is intraperitoneal.
91
Q

is the duodenal mucosa smooth or folded?

A

the very first part is smooth and the rest is folded in circular folds - plicae circularis

92
Q

what is the sphincter of oddi what does it do and where is it found

A
  • its a muscular valve surrounding the duodenal papilla found half way down the duodenum
  • it controls the entry of enzymes and bile into the duodenum
    • the enzymes and bile travel in the ampulla of vater.
93
Q

where can gall stones lodge and what effect does this have

A
  • bile duct
    • causes a build up of bilirubin → jaundice and can progress to liver failure
  • pancreatic duct
    • causes high pressure within the pancreas → leakage of enzymes out of the duct → digestion of the pancreas itself = pancreatitis [potentially fatal]
      • in pts that survive, the pancreas can leak → pseudocyst as fluid fills the lesser sac and compresses the stomach
  • both
94
Q

what is pancreatitis

A

leakage of pancreatic enzymes → digestion of the pancreas

95
Q

what is a pseudocyst

A

a cyst with mesothelial lining rather than epithelial

leakage of fluid from the pancreas into the lesser sac, compressing the stomach and making pt feel full.

96
Q

what structures join and form the common bile duct and what is its course

A
  • hepatic bile duct and cystic bile duct join together → CBD
  • CBD passes down through the head of the pancreas and joins the pancreatic duct to form the ampulla of vater
    • together they pass into the duodenum via the duodenal papilla
97
Q

which artery lies behind the first part of the duodenum

A

gastroduodenal artery

98
Q

what lies behind the pancreas and the stomach

A

lesser sac

99
Q

how many pancreatic ducts are there and what is the embryological significance of this

A

normally 1 duct but 2 parts of pancreas fuse together in utero

  • In the early weeks of gestation, the ventral pancreas and dorsal pancreas form
  • Between week 6 and 7 the pancreas starts to rotate around the gut till they meet and fuse
100
Q

describe the mucosa of the small intestine and how it differs between the ileum and jejunum

A
  • highly folded with circular folds - plicae circularis and villi
    • each epithelial cell also has microvilli
  • plicae circularis are more pronounced in the jejunum than the ileum
    • less need for the folds as the majority of nutrients are absorbed in the jejunum
101
Q

how is the ileum defined from the jejunum

A

the appearance of large submucosal lymph nodules called Peyer’s patches - elongated thickened areas, and their surface is free of villi

also seen histologically

102
Q

how does the mesentery of the jejunum and ileum differ

A

more fat is deposited in the mesentery of the ileum than the jejunum

103
Q

what is the superior mesenteric artery a branch of and where

A

the aorta just below the coeliac trunk

104
Q

how is the mesenteric blood supply arranged

A

in arterial arcades with vasa rectae

105
Q

what marks the start of the large intestine and where is it located

A

the ileo-caecal valve in the right iliac fossa

106
Q

which parts of the large intesting are mobile and which are retroperitoneal/fixed

A
  • mobile
    • transverse colon
    • sigmoid colon
  • fixed
    • ascending colon
    • descending colon
107
Q

describe the arrangement of muscles in the large intestine

A
  • an outer longitudinal layer of muscle made up of 3 bands of muscle - taeniae coli.
    • these fuse to 1 continuous muscle at the recto-sigmoid junction to become the internal anal sphincter
  • the inner layer is made of repeated circular muscles → the formation of haustrations
108
Q

where is the appendix located

A

at the base of the caecum

McBurneys point -⅔ distance between umbilicus and right ASIS

109
Q

what are appendices epiploica

A
  • small pouches of peritoneum, filled with fat.
110
Q

what does the inferior mesenteric artery arise from and where does it branch from

A

the lower abdominal aorta

branches off just before the bifurcation

111
Q

what foodstuff is absorbed through the lymphatic system

A

fat and fat soluble vitamins

112
Q

name 4 anatomical features that provide a high surface area for absorption

A
  1. villi
  2. microvilli
  3. plicae circularis
  4. long length folded and held together by mesentery
113
Q

how do you distinguish a loop of SI from LI

A
  • appendices epiploica
  • haustrum
  • LI is wider than SI
114
Q

what are the parts of the duodenum and which is retroperitoneal

A
  1. superior - the first part of the superior section is intraperitoneal, the rest is retro
  2. descending
  3. inferior
  4. ascending
115
Q

function of the stomach

A
  1. Store and mix food
  2. Dissolve and continue digestion
  3. Kill microbes
  4. Secrete intrinsic factor – important for vitamin B12.
  5. Regulates emptying into the duodenum.
  6. Secrete proteases
  7. Activates proteases
  8. Lubrication to prevent damage from material within it.
  9. Mucosal protection
116
Q

describe the gastric muscosa

A

surface of the stomach is flat with invaginations known as gastric pits where the cells of the stomach are found

117
Q

what cells are found in gastric pits

A
  • chief cells
  • parietal cells
  • ECL cells Enterochromaffin like cells
  • enteroendocrine cells
    • D cells
    • G cells
118
Q

what does each cell of the stomach produce

A
  • chief cells = gastic acid and intrinsic factor
  • parietal cells = pepsinogen and gastric lipase
  • ECL cells Enterochromaffin like cells = histamine
  • enteroendocrine cells
    • D cells = somatostatin
    • G cells = gastrin
    • S cells = secretin
    • I cells = CCK
119
Q

what are ECL cells,

where are they found

and what do they make

A
  • Enterochromaffin-like cells
  • found in the lamina propria of the stomach, beneath the epithelia
  • histamine
120
Q

how is gastric acid secretion regulated

A

regulated partly by the brain and partly by hormones and chemical messengers

121
Q

what is gastric acid and where is it produced

A

HCl

produced in gastric pits by parietal cells

122
Q

how is gastric acid produced

A

in the parietal cells

  • Cl- ions are brought into the parietal cells via the Chloride bicarbonate pump.
    • the Cl- ion than passes into the stomach lumen passively through a channel
  • a hydrogen potassium pump transports H+ ions in the lumen of the stomach using ATP as this is going against its conc. gradient
    • K+ions are transported into the cell to maintain electrical neutrality. it passes out of the cell passively down the e- gradient via a channel
  • H+ ions are generated by H2O + CO2 → H2CO3 →HCO3- + H+
    • Carbonic anhydrase mediates the formation of carbonic acid.
  • H+ is used to regenerate H2O
123
Q

what are the phases of gastric acid secretion

A
  • cephalic phase
    • triggered by sight, smell, taste or thought of food
    • stimulates stomach secretory activity
  • gastric phase
    • occurs once food has reached the stomach
    • increases stomach secretory activity
  • intestinal phase
    • regulates enterogastrones to stop secretory activity in the stomach
    • chyme is passed from the stomach into the duodenum
124
Q

what happens during the cephalic phase and how is it mediated

A

during the cephalic phase

  • the sight, smell, taste, thought or chewing of food → hypothalamus acting on the medulla → stimulation of the stomach via vagus nerve → ACh release [stimulatory NTransmitter]
    • Ach stimulates the upregulation of proton pumps in parietal cells for HCl secretion
    • ACh stimulates release of gastrin from G cells
    • ACh stimulates release of histamine from ECL cells
      • Gastrin and histamin act on parietal cells to stimulate HCl release
    • ACh also stimulates chief cells to secrete pepsinogen and gastric lipase

mediated by the parasympathetic nervous system

125
Q

what happens during the gastric phase and how is it mediated

A
  • distention of the stomach → stimulation of vagovagal and local reflexes which both → stimulation of secretory cells
  • elevated pH → activation of chemoreceptors → stimulation of G cells to release more gastrin to increase gastric acid secretion from parietal cells directly and indirectly by also stimulating ECL cells to release histamine
  • Increased pH reduces somatostatin secretion (lessens its inhibition of parietal cells)
    • overall effect = increased gastric acid secretion

mediated parasympathetically [vagus] and

126
Q

what happens during the intestinal phase

A

overall secretory activity in the stomach ⇣ as inhibition takes place while the stomach empties

  1. The stomach will pass the chime through to the duodenum →
    • Duodenum distension
    • Low luminal pH
    • Hypertonic luminal contents
    • Presence of amino acids and fatty acids
  2. the duodenal stretch receptors and chemoreceptors trigger the enterogastric reflex which reduces vagal parasympathetic stimulation of the gastric secretory activity
  3. Low pH and presence of lipids and AAs release of→
    • CCK by I cells
      • stimulates and regulates movement of the stomach
      • stimulates release of bile from the gall bladder
    • secretin by S cells
      • promotes release of somatostatin
      • inhibits gastrin release
    • GIP by K cells
127
Q

how is the gastric phase stopped

A
  • A low pH in the lumen of the stomach [acidic]
    • Directly inhibits gastrin secretion
    • Indirectly inhibits histamine release, via gastrin inhibition
    • Stimulates D cells to release somatostatin which inhibits parietal cell activity.
128
Q

summarise the key players in the phases of digestion

A
  • Regulation of gastric acid secretion is controlled by brain, stomach (on) and duodenum (off)
  • 1 Parasympathetic neurotransmitter = ACh
  • 1 Hormone = gastrin
    • secreted by G cells
  • 2 Paracrine factors = histamine (stimulatory) and somatostatin (inhibitory)
    • ECL cells secrete histamine
    • D cells secrete somatostatin
  • 2 key Enterogastrones = secretin and CCK (both inhibitory)
    • S cells secrete secretin
    • I cells secrete CCK
129
Q

what is a peptic ulcer,

what causes one

examples

A

a breach in the mucosa of the stomach

caused by increased attack on the mucosa OR decreased defence

  • causes:
    • H pylori
    • Meds: NSAIDs
    • Gastrinoma: unregulated hypersecretion of acid -rare
    • chemical irritants: alcohol bile salts
130
Q

how does the gastric mucosa protect itself from acid

A
  1. alkaline mucous
  2. tight junctions in the epithelia
  3. regulated gastric secretion via feedback loops
  4. replacement of damaged cells as they’re lost to maintain the barrier
131
Q

how do NSAIDs increase risk of peptic ulcer

A
  • NSAIDs inhibit COX1 enzymes needed for prostaglandin synthesis.
  • Prostaglandins also stimulate the production of gastric mucous, as well as mediating inflammation  ¯mucosal defence.
    • Treated with misoprostol – PG analogue
    • Treated with PPI or H2 agonist to ¯ gastric secretion.
132
Q

how does H pylori infection increase risk of peptic ulcer

A
  1. h pylori lives in the mucous of the stomach and secretes urease
    • urease breaks urea down → ammonia + CO2
      • Ammonia + H+ = ammonium
        • ammonium removes the bicarbonate protective layer of of the mucous
    • the bacteria also secretes cytotoxin A, proteases and phospholipases which damage the epithelia and reduce mucosal defence
133
Q

what is the tongue attached to

A

the posterior of the ramus of the mandible

134
Q

decribe the innervation of the tongue

A
  • anterior ⅔ of the tongue innervated by:
    • V3 of the trigeminal nerve for general sensation
    • facial nerve for taste
  • posterior ⅓ of the tongue innervated by:
    • glossopharyngeal nerve for general sensation AND taste
  • motor innervation supplied by:
    • hypoglossal nerve
135
Q

what are the palatine tonsils and their function

A
  • a consolidation of lymphoid tissue
  • sample organisms that may enter the body though the mouth or nose
136
Q

which cell secretes protease

and what stimulates its relese

A

chief cells secrete pepsinogen [zymogen]

stimulated by ACh from parasympathetic innervation AND HCl secretion from parietal cells

137
Q

why is pepsinogen secreted alongside HCl

A

pepsinogen is a zymogen, so it must be cleaved to form pepsin -active enzyme

HCl cleaves pepsinogen in the lumen of the stomach → pepsin

138
Q

how is pepsin inactivated

A

by HCO3- in the small intestine - duodenum

139
Q

pepsin is the most important enzyme for protein digestions

T/F

A

False

  • pepsin accelerates protein breakdown but is not essential
    • it helps break the protein down into smaller pieces to increase the surface area for further digestion
  • proteins are broken down further in the small intestine by pancreatic enzyme trypsin and chymotrypsin
140
Q

how is the conversion of pepsin regulated and what mediates this

A

by a +ve feedback loop

mediated/catalysed by pepsin

141
Q

what feature of the stomach allows it to expand without increasing the luminal pressure

A

receptive relaxation

  • the smooth muscle in the fundus and the body relax
  • mediated by the parasympathetic branch of the vagus nerve acting on the enteric nerve plexus
  • Nitric oxide and serotonin released by enteric nerves mediate relaxation in response to stretching of the stomach
142
Q

describe the process of peristalsis

A
  1. the arrival of food = stimulus for peristaltic waves
  2. waves begin in the gastric body
    • these waves are weak and little mixing occurs here
  3. more powerful contractions occur in the antrum
  4. the pyloric sphincter closes as the wave reaches the pylorus
    • this limits the amount of chyme passing into the duodenum
  5. the contents are forced back towards the body to continue mixing
  6. the sphincter eventually relaxes allowing chyme to pass through to the duodenum
143
Q

how is peristalsis regulated

A
  • by the pacemaker cells of the stomach interstital cells of cajal
    • located in the muscularis propria - longitudinal smooth muscles of the stomach
  • waves are constant ∼ 3 waves/minute
144
Q

describe the electrical rhythm of the Cajal cells

A
  • they undergo slow depolarisation and repolarisation
    • waves of depolarisation pass through the gap junctions in adjacent smooth muscle cells
  • when empty there is little contraction as there is little additional stimulus to enable the to reach the threshold potential
145
Q

what factors affect the strength of contraction

A
  • Strength of peristaltic contractions is ­­­increased by:
    • Gastrin
    • gastric distension [detected by mechanoreceptors]
  • Strength of peristaltic contractions is ­­­decreased by:
    • Duodenal distention
    • increased ­duodenal osmolarity
    • ­increased duodenal fat
    • ­increased sympathetic stimulation
    • decreased parasympathetic stimulation
    • decreased duodenal luminal pH
146
Q

which has a greater capacity - the stomach or the duodenum

A

the stomach

147
Q

what causes dumping syndrome

A

overfilling of the duodenum with a hypertonic solution

148
Q

what is an enterogastrone

A

a hormone secreted by the duodenum

149
Q

what stimulates release of enterogastrones

A

within the duodenum:

  1. increased acidity
  2. increased amino acids
  3. increased pH
  4. distension
  5. hypertonicity
150
Q

what is the effect of released enterogastrones

A

increased plasma enterogastrones → reduced gastric emptying

151
Q

what are the main functions of the the small intestine

A
  • absorption of water and nutrients
  • secretion of electrolytes
152
Q

what causes gastroparesis

A
  • This is delayed gastric emptying
153
Q

where does the majority of water absorption take place

A

the small intestine

154
Q

what are paneth cell’s function

where are they located

A
  • Paneth cells are involved in anti-microbial function by modulating the microbial composition of the SI.
  • located in the SI crypt cells
155
Q

what are the main sections in villi structure

what are their function

A

villi increase the surface area for absorption

crypts increase the surface area for secretion

156
Q

how many layers of muscles in the stomach

A

3 - inside → out

  1. oblique muscle
  2. circular muscle
  3. longitudinal muscle
157
Q

what does each region of the stomach secrete

A
158
Q

what are chemical irritants of the stomach lining

A
  • bile salts
    • duodenal-gastric reflux
  • alcohol
159
Q

mechanisms of absorption

A
  • simple diffusion
  • active transport
  • facilitate diffusion
  • paracellular transport
  • endocytosis
160
Q

how is water absorbed in the small intestines

A

water moves out of the lumen into the enterocytes by osmosis

161
Q

what factors influence absorption and secretion

A
  • absorption
    • blood flow
    • nutrient intake
    • GI motility
    • number and structure of enterocytes
  • secretion
    • irritants
    • bile
    • bacterial toxins
162
Q

what cells produce secretin

what causes its release

what is its function

A
  • S cells
  • released due to chyme arriving in the duodenum and due to the low pH of the chyme
  • secretin has 3 main functions
    • Inhibits gastrin release → lack of stimulus for HCl release
    • Promotes somatostatin release → inhibition of parietal cells
    • promotes HCO3- secretion from the pancreas
163
Q

what cells produce CCK

what does CCK stand for

what causes its release

what is its function

A
  • cholecystokinin is produced by I cells in the duodenum and jejunum
  • its release is stimulated by the presence of fat in the SI
  • functions
    • Triggers contraction of the gall bladder to release bile and the secretion of enzymes through the pancreatic duct
    • sphincter of oddi relaxation
    • delays gastric emptying
    • inhibition of gastric acid secretion
164
Q

what are the broad functions of the pancreas

A

endocrine and exocrine secretions

165
Q

which pancreatic cell produces HCO3-

summarise process

A

duct cells

  • Na+ and Cl- diffuse into the cell slowly
  • H2O + CO2 → HCO3- + H+
  • HCO3- is exchanged for Cl-
166
Q

roughly how much bicarbonate is produced by the pancreas daily

A
  • 1L/day of bicarb is secreted from the pancreas.
167
Q

function of pancreatic bicarb secretion

A
  • Bicarb protects the duodenal mucosa by neutralising the acid from the stomach
  • Bicarb also buffers the contents of the duodenum so that the enzymes secreted from the pancreas have an optimal pH to digest food in
168
Q

which cells secrete bicarb

which secrete enzymes

A

acini cells secrete both

  • acinar cells = enzyme secretion
  • centrocinar cells = bicarb
    • duct cell = site of bicarb/Cl- exchange
169
Q

what are the stimuli of the pancreas

A
  • hormonal
    • secretin stimulated by chyme in the duodenum and low pH
      • causes release of bicarb
    • CCK stimulated by fats and protein in the duodenum
      • causes release of enzymes
  • neuronal
    • vagus inputs → release of enzymes
170
Q

what are the proteases secreted by the pancreas

A
  • trypsin and chymotrypsin
    • secreted as zymogens that are cleaved in the SI: trypsinogen and chymotrypsinogen
171
Q

how are the pancreatic zymogens cleaved

A

trypsin and chymotrypsin → trypsinogen and chymotrypsinogen via:

  • enterokinase: an enzyme found on the epithelial wall
  • trypsin: a positive feedback mechanism
172
Q

trypsin and chymotrypsin break peptides down to amino acids

T/F

A

False

  • they only break down proteins into smaller peptides
  • other proteases break peptides down into amino acids
173
Q

how do pancreatic lipases work

A

by breaking down triglycerides via hydrolysis → monoglycerides and free fatty acids

174
Q

what is dietary fat absorption dependent on

A

pancreatic and hepatic/cystic secretions

  • bile emulsifies fats into droplets that lipase then acts on
175
Q

what enzyme breaks down carbs

A
  • Amylase primarily
    • Amylase hydrolyses starch to maltose & dextrins
  • Gelatinase, elastase, ribonuclease, deoxyribonuclease
176
Q

what is the function of somatostatin in the GIT

A
  • Somatostatin is a powerful inhibitor of pancreatic exocrine secretion and gastric acid secretion through inhibition of CCK and secretin
177
Q

which cells produce somatostatin

A
  • D cells in the stomach
  • delta cells in the islets of langerhans
178
Q

where are fat siluble vitamins absorbed

A

in the ileum via fat micelles

179
Q

how is vitamin B12 absorbed

A
  • intrinsic factor secreted by parietal cells, binds to B12
  • in the terminal ileum, intrinsic factor binds to certain factors
  • B12 is taken up by endocytosis
180
Q

summarise the digestion and absorption of carbs

A
  • Starch in food Digestion begins in mouth
    • Alpha amylase at pH 6.7
  • 95% of digestion occurs in small intestine
    • Pancreatic alpha amylase – via pancreatic duct
    • Broken down into disaccharides e.g. maltose
  • Enzymes on luminal membranes of SI epithelial cells
    • Break down disaccharides into monosaccharides e.g. glucose
  • Monosaccharides are then absorbed into bloodstream
181
Q

give examples of disaccharides and their corresponding monosaccharides

A
182
Q

give 3 monosaccharides and how they are absorbed

A
  • Glucose and galactose
    • absorbed by active transport via the Sodium-glucose cotransporter
  • fructose
    • absorbed by facilitated diffusion
183
Q

Gastrin stimulus and cell targets

A
  • stimulus
    • stomach distension
    • vagus stimulation
    • presence of peptides in the stomach lumen
  • cell targets
    • parietal cells → HCl secretion
    • ECL cells →histamine release → parietal cells → HCl release
184
Q

summarise HCl production in parietal cells

A
  • the proton pump is responsible for the production of HCl
  1. H2O + CO2 => H2CO3 => HCO3- and H+
  2. H+ is pumped out of the cell into the stomach lumen in exchange for K+ via the proton pump.
    • H+ can also come from water split into OH- and H+
    • K+ diffuses back into the stomach lumen down the electrochemical gradient
  3. the HCO3- is exchanged into the blood for Cl- which then crosses into the lumen down a concentration gradient
185
Q

what factors stimulate and inhibit parietal cells

A
  • stimulate:
    • Gastrin
    • acetylecholine
    • histamin
  • inhibit
    • somatostatin
186
Q

where does the most water absorption take place

A

the jejunum

187
Q

how is the 9 anatomical regions of the abdomen divided

A
  • the right and left midclavicular lines vertically
  • the subcostal line and intertubercular line horizontally.
188
Q

where in the gut are iron, folate and B12 absorbed

A
  • iron = duodenum
  • Folate = jejunum
  • B12 = ileum

Dow Jones Index

Is Fucking Bad

189
Q

what are the boundaries of the foregut midgut and hind gut

A
  • Foregut = distal third of oesophagus → ½ way down the duodenum
  • midgut = ½ way down the duodenum → ⅔ way across transverse colon
  • hindgut = ⅔ way across transverse colon → rectum
190
Q

6 main differences between the ileum and jejunum

A
  1. ileum has peyers patches and jejunum doesn’t
  2. ileum has short vasa recta and disorganised arcades, jejunum has long vasa recta and organised arcades
  3. Jejunum has more plicae circularis than ileum thus its SA is larger
  4. jejunum has thicker walls than the ileum
  5. ileum is fatty and jejunum is lean
  6. ileum has pale pink mucosa while jejunum has deep red
191
Q

7 differences between small and large intestines

A
  1. LI has epiploic appendages SI doesn’t
  2. LI has haustra and taenia coli, SI doesn’t
  3. SI has villi, LI doesn’t
  4. SI is longer than the LI
  5. SI responsible for most absorption of nutrients and water, LI balances out water and K+ levels
  6. contents of SI are liquid and acidic, contents of LI are more solid and less acidic
  7. SI = 3cm diameter, LI = 6cm [caecum = 9cm]
192
Q

levels of branching of the SMA, IMA and coeliac trunk

A
  • Coelia = T12
  • SMA = L1
  • IMA = L3
193
Q

what is the arcuate line

A
  • The arcuate line is a curved line found posterior to the rectus abdominis muscle bilaterally, usually located at about one-third of the distance from the pubic crest to the umbilicus
  • it is a site of weakness in the abdominal wall through which abdominal hernias may form
194
Q

describe the layers above and below the arcuate line

A
  • both levels
    • skin
    • campers fascia
    • scarpas fascia
  • Above
    • external oblique
    • ½ internal oblique
    • rectus abd.
    • ½ internal oblique
    • transversus abd.
    • transversalis fascia
    • peritoneum
  • Below
    • EO
    • IO
    • TA
    • rectus abd.
    • transversalis fascia
    • peritoneum
195
Q

how is glucose absorbed in the GIT

A

Glucose is passively absorbed through a membrane transporter

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