Gastro Flashcards
(195 cards)
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.
2
Q
which salivary glands are continuously active
A
- sublingual
- submandibular
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
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
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
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
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.
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
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.
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
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
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
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.
14
Q
which gland is shown in each row
A
15
Q
what are the main defences in the oral cavity
A
- saliva glands wash away particles which viruses and bacteria could feed on
- palatine tonsils provide immunological surveillance and resistance via
- Lymphocyte subsets
- Dendritic cells.
- mucosa provides a physical barrier
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
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
18
Q
components of whole saliva
A
- Whole saliva = salivary gland secretions, blood, oral tissues, microorganisms and food remnants
19
Q
what types of acini are these
A
20
Q
two types of salivary ducts
A
intralobular
main excretory
21
Q
3 main cell types within an intralobular duct
A
acinar cells
intercalated duct cell
striated cell
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
23
Q
what is primary saliva
A
NaCl rich isotonic plasma like fluid secreted by the acini.
24
Q
functions of saliva
A
- A lubricant for mastication, swallowing and speech.
- Oral hygiene by:
- Physically washing the mouth
- Having antibacterial, antiviral and antifungal properties.
- Maintains pH at ~ 7.2 using a bicarbonate/carbonate buffer system to rapidly neutralise acids.
- Begin digestion by carrying enzymes.
- Assists with taste as an aqueous solvent is needed.
- Dysfunction associated with oral pain, infections and risk of caries.
- Production of secretions:
25
what are the main stages of swallowing
1. oral = chewing and movement into pharynx
2. pharyngeal = movement from pharnx into oesdophagus
3. oesophageal = movement into oesohpagus and stomach
26
describe the stages of swallowing
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]
27
key muscles involved with swallowing
* 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.
28
nerves involved in swallowing
* vagus
* hypoglossal
* glossopharyngeal
* accessory
* trigeminal
* facial
29
what is the rectus sheath formed from
the aponeurosis of the external oblique, internal oblique and transversus abdominis
30
name the muscles of the abdomen
* rectus abdominis
* internal oblique
* external oblique
* transversus abdominis
31
what are the bony landmarks of the abdomen
1. xiphoid process
2. ASIS
3. pubic symphisis
4. iliac crest
5. costal margin
6. pubic tubercle
32
name the 9 regions of the abdomen
suprapubic = hypogastric
lumbar = flank = loin
33
where/what is McBurney's point
* 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.
34
where/ what is the transpyloric plane of addison
* 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
35
what is the intertubercular plane and what does it mark
the plane at the level of the iliac crests.
marks the bifurcation of the abdominal aorta
36
what does the abdominal aorta divide into
the left and right common iliac arteries and the median sacral artery
37
where/ what is the intercristal plane
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]
38
what is the surface marking of the abdominal aorta bifurcation
intertubercular plane - lying on the iliac crests
39
in which region of the abdomen is pain from the 3 parts of the bowel felt
* 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.
40
describe the anatomy os a 6 pack
41
what is the upper boundary of the abdomen
the diaphragm
42
what covers the abdomen
the peritoneum
* 2 continuous layers:
* visceral: covers the organs
* parietal covers the abdomen wall
* the potential space between the 2 layers = the peritoneal cavity
43
what is the peritoneal cavity
the potential space between the parietal and visceral peritoneum
contains a layer of mucous to allow the viscera to slide freely over eachother
44
what is ascites
distension of the abdomen caused by fluid in the peritoneal cavity
45
main difference between the parietal and visceral peritoneum - other than what they cover
* 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
*
46
functions of the colon
* 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
47
what are the ligaments of the liver and what are they made of
made of double layer of peritoneum
* falciform ligament
* right triangular ligament
* left triangular ligament
48
can the liver be palpated trans-abdominally in a healthy pt
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.
49
what is ligamentum teres
a remnant of the umbilical vein. found on the free edge of the falciform ligament
50
what is the falciform ligament where does it attach to and what does it demarcate
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
51
what lies deep to the left lobe of the liver and inferior to the right lobe
* the stomach lies deep to the left lobe
* the gall bladder is inferior to the right lobe
52
what is the lesser omentum made of, what does it carry and where is it located
* 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]
53
what is the portal triad and where is it found
3 major vessels
* portal triad
* hepatic artery
* bile duct
found in the free edge of the lesser omentum
54
what is the porta hepatis
* this is a fissure running into the liver carrying the portal triad
* the portal vein
* the hepatic artery
* bile duct
55
where is the spleen located
far left above the ribcage and lateral to the stomach
56
can the spleen be palpated in healthy pts
no as it lies above the costal margin
57
what is the spleen attached to and what attaches it
* the greater curve of the stomach and the posterior abdominal wall
* the greater omentum
58
what is the greater omentum, where does it attach and what is its function
* 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
59
what is the greater sac
the main peritoneal cavity
60
what is the lesser sac and how is it accessed
a peritoneal space that lies directly behind the stomach accessed via the epiploic foramen
61
what is mesentery and whats it made of
The ***mesentery*** is an organ that attaches the intestines to the posterior abdominal wall in and is formed by the double fold of peritoneum
62
which parts of the bowel have mesentery
the small bowel - jejunum and ileum
the transverse colon
the sigmoid colon
appendix
63
what is the function of mesentery
* 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
64
which organs are mobile and which are fixed to the posterior wall
* mobile
* transverse colon
* sigmoid colon
* appendix
* small intestines
* fixed
* ascending colon
* descending colon
* rectum
65
describe the order of the intestines and colon
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.
66
where does bacteria tend to gravitate to in the abdomen
the lowest space in the abdomen
* behind the right lobe of the liver when lying flat
* into the pelvis when upright
67
what is peritoneal dialysis and how is it possible
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
68
which parts of the adomen are mobile
69
what is the function of mesentery
* 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
70
what does the lesser omentum carry
the portal triad vessels
hepatic artery, portal vein and bile duct
71
where is the pancreas located
behind the stomach and the lesser sac, retroperitoneal
72
what makes up the gastric bed and where is it located?
* pancreas, splenic artery and part of the duodenum
* located behind the lesser sac of the omentum
73
how might a stomach tumour spread
* via the lymphatics around the coeliac axis
* via the veins passing to the liver
74
what is a peptic ulcer
a breach in the mucosa and gastric wall of the stomach
75
which artery supplies the fore gut
the coeliac trunk
76
where does the coeliac trunk branch off and what structures does it supply
* 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
77
describe the innervation of the foregut
* sympathetic innervation from the greater splanchnic - T5-T9
* parasympathetic innervation from anterior and posterior vagal trunks
78
draw and name the parts of the stomach
* fundus
* antrum
* body
* pylorus
* cardia
79
how are the portal triad vessels arranged
the hepatic artery has the bile duct to the right of it and the portal vein behind them
80
describe the inner membrane of the stomach
rugae
81
name a common site for peptic ulcers to occur and what is the consequence
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
what are the borders of the lesser sac
the greater and lesser omentum AND the caudate lobe of the liver.
83
at what vertebral level does the oesophagus pass through the diaphragm and what structures pass with it
T10 -
I 8 10 EGGS AT 12
I 8 - **I**VC crosses the diaphragh at the level of T**8**
10 EGGs - **E**sopha**G**us + va**G**us cross the diaphragh at the level of T**10**
AT 12 - **A**orta + **A**zygos vein + **T**horacic duct cross the diaphragm at the level of T**12**
84
what is a porto-systemic anastomosis
communication between the portal venous system and the systemic venous system, via the veins of the oesophagus and bypassing the liver
85
what are the boundaries of the foregut, midgut and hind gut,
* their arterial supply
* venous drainage
* innervation
* 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
name the 3 main branches of the coeliac trunk and what they supply
* 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
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87
which organs are retroperitoneal
* supra-renal adrenal glands
* aorta and IVC
* duodenum - first third
* pancreas
* ureters
* colon - ascending and descending
* kidneys
* oesophagus
* rectum
88
draw and label the coeliac axis
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89
what level is the coeliac trunk located
T12
90
describe the parts of the pancreas
* **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
is the duodenal mucosa smooth or folded?
the very first part is smooth and the rest is folded in circular folds - plicae circularis
92
what is the sphincter of oddi what does it do and where is it found
* 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
where can gall stones lodge and what effect does this have
* 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
what is pancreatitis
leakage of pancreatic enzymes → digestion of the pancreas
95
what is a pseudocyst
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
what structures join and form the common bile duct and what is its course
* 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
which artery lies behind the first part of the duodenum
gastroduodenal artery
98
what lies behind the pancreas and the stomach
lesser sac
99
how many pancreatic ducts are there and what is the embryological significance of this
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
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100
describe the mucosa of the small intestine and how it differs between the ileum and jejunum
* 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
how is the ileum defined from the jejunum
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
how does the mesentery of the jejunum and ileum differ
more fat is deposited in the mesentery of the ileum than the jejunum
103
what is the superior mesenteric artery a branch of and where
the aorta just below the coeliac trunk
104
how is the mesenteric blood supply arranged
in arterial arcades with vasa rectae
105
what marks the start of the large intestine and where is it located
the ileo-caecal valve in the right iliac fossa
106
which parts of the large intesting are mobile and which are retroperitoneal/fixed
* mobile
* transverse colon
* sigmoid colon
* fixed
* ascending colon
* descending colon
107
describe the arrangement of muscles in the large intestine
* 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
where is the appendix located
at the base of the caecum
McBurneys point -⅔ distance between umbilicus and right ASIS
109
what are appendices epiploica
* small pouches of peritoneum, filled with fat.
110
what does the inferior mesenteric artery arise from and where does it branch from
the lower abdominal aorta
branches off just before the bifurcation
111
what foodstuff is absorbed through the lymphatic system
fat and fat soluble vitamins
112
name 4 anatomical features that provide a high surface area for absorption
1. villi
2. microvilli
3. plicae circularis
4. long length folded and held together by mesentery
113
how do you distinguish a loop of SI from LI
* appendices epiploica
* haustrum
* LI is wider than SI
114
what are the parts of the duodenum and which is retroperitoneal
1. superior - the first part of the superior section is intraperitoneal, the rest is retro
2. descending
3. inferior
4. ascending
115
function of the stomach
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
describe the gastric muscosa
surface of the stomach is flat with invaginations known as gastric pits where the cells of the stomach are found
117
what cells are found in gastric pits
* chief cells
* parietal cells
* ECL cells Enterochromaffin like cells
* enteroendocrine cells
* D cells
* G cells
118
what does each cell of the stomach produce
* **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
what are ECL cells,
where are they found
and what do they make
* Enterochromaffin-like cells
* found in the lamina propria of the stomach, beneath the epithelia
* histamine
120
how is gastric acid secretion regulated
regulated partly by the brain and partly by hormones and chemical messengers
121
what is gastric acid and where is it produced
HCl
produced in gastric pits by parietal cells
122
how is gastric acid produced
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
what are the phases of gastric acid secretion
* **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
what happens during the cephalic phase and how is it mediated
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
what happens during the gastric phase and how is it mediated
* 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
what happens during the intestinal phase
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
how is the gastric phase stopped
* 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
summarise the key players in the phases of digestion
* 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
what is a peptic ulcer,
what causes one
examples
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
how does the gastric mucosa protect itself from acid
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
how do NSAIDs increase risk of peptic ulcer
* 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
how does H pylori infection increase risk of peptic ulcer
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
what is the tongue attached to
the posterior of the ramus of the mandible
134
decribe the innervation of the tongue
* 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
what are the palatine tonsils and their function
* a consolidation of lymphoid tissue
* sample organisms that may enter the body though the mouth or nose
136
which cell secretes protease
and what stimulates its relese
chief cells secrete pepsinogen [zymogen]
stimulated by ACh from parasympathetic innervation AND HCl secretion from parietal cells
137
why is pepsinogen secreted alongside HCl
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
how is pepsin inactivated
by HCO3- in the small intestine - duodenum
139
pepsin is the most important enzyme for protein digestions
T/F
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
how is the conversion of pepsin regulated and what mediates this
by a +ve feedback loop
mediated/catalysed by pepsin
* ![]()
141
what feature of the stomach allows it to expand without increasing the luminal pressure
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
describe the process of peristalsis
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
how is peristalsis regulated
* 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
describe the electrical rhythm of the Cajal cells
* 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
what factors affect the strength of contraction
* 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
which has a greater capacity - the stomach or the duodenum
the stomach
147
what causes dumping syndrome
overfilling of the duodenum with a hypertonic solution
148
what is an enterogastrone
a hormone secreted by the duodenum
149
what stimulates release of enterogastrones
within the duodenum:
1. increased acidity
2. increased amino acids
3. increased pH
4. distension
5. hypertonicity
150
what is the effect of released enterogastrones
increased plasma enterogastrones → reduced gastric emptying
151
what are the main functions of the the small intestine
* absorption of water and nutrients
* secretion of electrolytes
152
what causes gastroparesis
* This is delayed gastric emptying
153
where does the majority of water absorption take place
the small intestine
154
what are paneth cell's function
where are they located
* Paneth cells are involved in anti-microbial function by modulating the microbial composition of the SI.
* located in the SI crypt cells
155
what are the main sections in villi structure
what are their function
villi increase the surface area for absorption
crypts increase the surface area for secretion
156
how many layers of muscles in the stomach
3 - inside → out
1. oblique muscle
2. circular muscle
3. longitudinal muscle
157
what does each region of the stomach secrete
158
what are chemical irritants of the stomach lining
* bile salts
* duodenal-gastric reflux
* alcohol
159
mechanisms of absorption
* simple diffusion
* active transport
* facilitate diffusion
* paracellular transport
* endocytosis
160
how is water absorbed in the small intestines
water moves out of the lumen into the enterocytes by osmosis
161
what factors influence absorption and secretion
* absorption
* blood flow
* nutrient intake
* GI motility
* number and structure of enterocytes
* secretion
* irritants
* bile
* bacterial toxins
162
what cells produce secretin
what causes its release
what is its function
* 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
what cells produce CCK
what does CCK stand for
what causes its release
what is its function
* 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
what are the broad functions of the pancreas
endocrine and exocrine secretions
165
which pancreatic cell produces HCO3-
summarise process
duct cells
* Na+ and Cl- diffuse into the cell slowly
* H2O + CO2 → HCO3- + H+
* HCO3- is exchanged for Cl-
166
roughly how much bicarbonate is produced by the pancreas daily
* 1L/day of bicarb is secreted from the pancreas.
167
function of pancreatic bicarb secretion
* 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
which cells secrete bicarb
which secrete enzymes
acini cells secrete both
* acinar cells = enzyme secretion
* centrocinar cells = bicarb
* duct cell = site of bicarb/Cl- exchange
169
what are the stimuli of the pancreas
* 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
what are the proteases secreted by the pancreas
* trypsin and chymotrypsin
* secreted as zymogens that are cleaved in the SI: trypsinogen and chymotrypsinogen
171
how are the pancreatic zymogens cleaved
trypsin and chymotrypsin → trypsinogen and chymotrypsinogen **via:**
* **enterokinase:** an enzyme found on the epithelial wall
* **trypsin**: a positive feedback mechanism
172
trypsin and chymotrypsin break peptides down to amino acids
T/F
False
* they only break down proteins into smaller peptides
* other proteases break peptides down into amino acids
173
how do pancreatic lipases work
by breaking down triglycerides via hydrolysis → monoglycerides and free fatty acids
174
what is dietary fat absorption dependent on
pancreatic and hepatic/cystic secretions
* bile emulsifies fats into droplets that lipase then acts on
175
what enzyme breaks down carbs
* Amylase primarily
* Amylase hydrolyses starch to maltose & dextrins
* Gelatinase, **elastase**, ribonuclease, deoxyribonuclease
176
what is the function of somatostatin in the GIT
* Somatostatin is a powerful inhibitor of pancreatic exocrine secretion and gastric acid secretion through inhibition of CCK and secretin
177
which cells produce somatostatin
* D cells in the stomach
* delta cells in the islets of langerhans
178
where are fat siluble vitamins absorbed
in the ileum via fat micelles
179
how is vitamin B12 absorbed
* 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
summarise the digestion and absorption of carbs
* 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
give examples of disaccharides and their corresponding monosaccharides
182
give 3 monosaccharides and how they are absorbed
* Glucose and galactose
* absorbed by active transport via the Sodium-glucose cotransporter
* fructose
* absorbed by facilitated diffusion
183
Gastrin stimulus and cell targets
* 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
summarise HCl production in parietal cells
* 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
what factors stimulate and inhibit parietal cells
* stimulate:
* Gastrin
* acetylecholine
* histamin
* inhibit
* somatostatin
186
where does the most water absorption take place
the jejunum
187
how is the 9 anatomical regions of the abdomen divided
* the right and left midclavicular lines vertically
* the subcostal line and intertubercular line horizontally.
188
where in the gut are iron, folate and B12 absorbed
* iron = duodenum
* Folate = jejunum
* B12 = ileum
Dow Jones Index
Is Fucking Bad
189
what are the boundaries of the foregut midgut and hind gut
* 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
6 main differences between the ileum and jejunum
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
7 differences between small and large intestines
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
levels of branching of the SMA, IMA and coeliac trunk
* Coelia = T12
* SMA = L1
* IMA = L3
193
what is the arcuate line
* The [arcuate line](https://www.osmosis.org/learn/Anatomy_of_the_anterolateral_abdominal_wall) is a curved line found posterior to the [rectus abdominis muscle](https://www.osmosis.org/learn/Anatomy_of_the_anterolateral_abdominal_wall) 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](https://www.osmosis.org/learn/Abdominal_hernias) may form
194
describe the layers above and below the arcuate line
* 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
how is glucose absorbed in the GIT
Glucose is passively absorbed through a membrane transporter
