Studied by 10 people
What’s the inner layer of the GIT?
mucosa
Name 2 types of mucosas and where they are found and why?
folded→ absorption / digestion
straight→ quick movement (oesophagus)
What’s over the mucosa?
Submucosa
What’s the enteric nervous system?
3rd division of nervous system
What’s in the submucosa?
Blood vessels + Nerves + Glands
What’s the function of the Meissner’s Plexus?
Determine vessels diamter/ secretions
→ control of submucos
What are the two layer of muscle ?
Inner= circular
Outer= longitutal
(inner part of the egg (zoltko) is a circular ball, outer is a long oval)
What’s the serosa?
smooth muscle layer
List the three phases of swallowing?
oral
pharyngeak (respiratory inhibited to prevent choking)
oesophageal
Where’s the swallowing centre?
Medulla
What receptors are in the pharynx?
Touch receptors
What are the 3 commands that the swallowing centre sends in the medulla?
soft palate blocks nasal and epiglottis and larynx blocks the trachea
upper oesophageal sphincter relaxes
peristakic wave
What cells line the oesophagus?
Squamous (flat cells)
What are the types of muscle that control the oesophagus?
1/3 skeletal
1/3 skeletal & smooth
1/3 smooth
Where’s the lower oesophageal spincter?
near the stomach to prevent reflux
In the stomach what does the mucosa contain?
Gastric glands that release gastric juices
What do goblet cell secrete?
mucus and HCO3-
(both protect the stomach from autodigestion)
What do pariental cells secrete?
HCl and intrinsic factor
What does intrinsic factor contain?
B12
Why is B12 needed?
To absorbe iron (pernicious anaemia)
What do enterochromaffin-like cells secrete?
Histamine and Serotonin
What does serotonin and histamine control?
Pancreas
What do chief cells secrete?
pepsinogen
What activates pepsinogen?
HCl
Name the 2 hormone secreting cells in the stomach?
G cells
D cells
What do G cells secrete?
Gastrin
What do D cells secrete?
Somatostatin
What are secretagogues?
They gauge out secretions (cause the secretion of an other substance)
What stimulates the release of HCl?
histamine
Acetylcholine
gastrin
How does the stomach churn?
Peristaltic waves
How is the gastric slow wave regulated?
by the pacemaker zone in the fundus
What’s stronger fundus& body or antrum?
Antrum at the bottom because that’s where most food is
What’s the pylorus?
Sphincter acting
→ prevents chyme in the duodeum
What nerves cause the contriction of the pylorus?
Sympathetic and Vagus
What does the vagus do to the pylorus?
constrict and relax
How does the antrum work with the duodeum?
contracts as a unit “ atral systole”
duodeum relax
a few ml of chybe → duodeum
What are the three regions of the duodeum?
Duodeum/ Jejunum/ Illeum
What are the functions of the jejunum and illeum?
reserve , most work happens in the duodeum
What’s the brush border?
Microvilin
What are the brush border enzymes?
sucrase , aminopeptidases
Where is the pacemaker for the small intestine?
Near bile duct
What does the dile duct do?
Deliver liver and pancreatic secretions
Does motility get faster or slower as yoi go down in the small intestine?
Slower
What segmentation?
Mixes chyme with enzymes and mucous
What cells generate the contraction pace in the SI?
Interstitial cells of Cajal
What kind of waves are produced by the interstitial cells of Cajall
slow
(faster at the proximal end)
What’s the function of the large intestine?
Absorb salt and water
What’s the haustra?
Folded outer surface of the large intestine
Order
sigmoid colon/ transverse colon/ descending colon and rectum
Transverse
Descending
Sigmoid
Rectum
What’s the valsalva manoeuvre?
Expiring against a closed glottis which raises vein pressure
Is digestion regulated?
No, only secretions and motility is
What regulates the GIT?
Hormones and neural control
What cells produce gastric acid?
Pariental cells
Why is gastric acid needed?
Pepsinogen→ pepsin
How do pariental cells generate protons?
CO2+ H20
(carbonic anhydrase)
H2CO3→ H+ + HCO3-
What happens to the H+ generated by pariental cells?
Pumped outside the cell into the gland duct by active transport
What happens to Cl- in the pariental cells?
Pumped against conc. gradient in the cell
this allows HCO3- to get out
no overall change in charge!
What ion is taken in when the proton leaves the pariental cell?
(anion exchange H+ & ____)
K+
What cells secrete pepsin
Chief cells
What stimulates pepsin?
gastrin , acetylcholine and acid
What cells make the mucous?
Gastric neck cells
What cells secrete bicarbonate?
Epithelial cells
What are the three phases of gastric acid regulation?
Cephalic (brain)
Gastric
Intestinal
How is the cephalic phase initiated?
Smell taste→ tells pariental cells stimulated
What nerve controls the cephalic phase response?
Vagus
What initiates the stimulatory gastric phase?
Food in stomach
amino acids released
G Cells release gastrin→ gastrin stimulates pariental cells→ HCl released
→ chief cells release pepsinogen
How is the gastric phase regulated?
If pH falls below 2 = negative feedback and parinetl cells stop producing HCl
What type of response is the intestinal phase?
Inhibitory
What mediates the intestinl phase?
chyme in duodeum= imhibition of more acid released
What three things are released in the inhibitatory intestinal phase?
Secretin
Gastric Inhibitatory Peptin
Cholecytokin CCK (stops motility and secretion)
What are peptic ulcers
erosion of mucous membrane
What two nerve thingies make up the enteric nervous system?
Meissner’s Plexus = control of secretions (sounds german and they love when sauerkraut secretes acidic juices)
Auerbach/ myenteric = control of muscles layers
What nerves supply the enteric nervous system?
para/ sympathetic?
Para and sympathetic
How does the ENS control the pacemaker cells in the GIT?
They can speed it up/down
not activate (will work regardless of ENS status)
What’s the gastroileal reflex?
gastric activity= illeal motility
How is the gatroileal reflex protectory?
If intestine stretches (ouch) = stomach will slow down
How do paracrine secretions act?
Locally
Where do paracrine secretions get released from
intestinal/ gastric mucosa
What does motilin do?
Stimulate contraction of stomach antrum and duodeum
Where do exocrine glands secrete?
Into ducts
What are the 3 pairs of salivatory glands?
Parotid
Submandibular
Sublingual
What are the 2 cell types in salivatory glands?
Serous acinar cells
Mucous acinar cells
What do mucous acinar cells do?
secrete glycoproteins
What do glycoproteins do?
Make mucin
What do serous acinar cells do?
secrete water, ionrganic salts and amylase
Compare plasma and saliva ion levels?
lower Na+ and Cl-
higher K+ and HCO3-
What’s the pH of saliva?
6.2
Is saliva hyper/ hypotonic?
Hypotonic
less ions than in plasma (plasma has more functions)
What is the first stage of saliva formation?
serous cells produce isotonic secretions
What does the isotonic secretion contain?
Amylase
What happens to the isotonic secretion?
Duct cells extract Na+ and Cl-
Add K+ and HCO3-
Which division of the nervous system controls the secretion?
Parasympathetic
(salivaring at icecream is very much not flight r fight)
But sometimes you have to fight for the icecream
a little sympathetic
Is the pancreas endocrine or exocrine?
both!
endo= insulin (that travels!)
exo= enzymes into ducts
What are the two compoments of the pancreatic juices?
enzymes
bicarbonate (neutralises chyme)
What stimulates the secretion of enzymes from the pancreas?
Secretin and ACh
What produces the aqueous component of pancreatic juice?
Epithelial cells lining the duct
Is the aqueous compoment hypotonic?
Nope
Isotonic
however HCO3- levels are increased due to the need to neutralise
How is bicarbonate produced in the epithelial cell of the duct?
water and carbon dioxide move into the cell
bicarbonate is made
H+ fucks off into the plasma and therefore Na+enters
HCO3- goes to do its job in the duct and Cl- goes in the cell to neutralise
So how is the primary aqueous secretion modified?
water addded
Na+ and HCO3- added
What inactive enzymes do acinar cells release?
Trypsin
Chymotripsin
Carboxypeptidase
Note
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