G.I Flashcards
During the fasting state what movements occur in the stomach and what induces them and how regular are they?
Migratory Motor Complex
Motilin
every 90 -120mins
What are the Enterogastrones that reduce acid secretion?
Secretin
CCK
GIP
Peptide YY
What are the main mechanisms that allow the stomach to accomodate more food?
Vagas Vagal Reflex
Entero - Gastric Reflex
What is the muscle contractions that happen in the stomach to force chyme through the pyloric sphincter?
Pyloric Pump Contractions - 20% of the Basic Electrical Rate
What is the term for the electrical activity that occurs in the stomach when food is present that helps mix?
Basic Electrical Rate
Where does Secretin come from and how does it work to inhibit HCl?
S cells of the dudoneum
Increases:
- somatostatin
- Reduces Gastrin
- Directly inhibits Parietal cells
What are the stages of Migratory Motor Complex?
Stage I: Quiescence
Stage II: Increased frequency of contraction
Stage III: Peak electrical and mechanical activity
Stage IV: Decline in activity leading to stage I
What are the movements in the Large intestines?
Mass movements
Haustra movements
Segmental propulsion
Main action is to mix the content well
What is the reflex that stimulates mass movement? can be triggered by intake of food.
Gastro- Coelic reflex
How do D cells work to control acid secretion?
If the pH drops they release somatostatin which acts directly on the G cells and parietal cells
When HCO3 is produced from HCl production, how is it transported out of the cell?
Cl- transporters. The Cl- which comes in is then used to make the HCl.
During swallowing what substances cause relaxation of the esophagus?
Nitric oxide
Vaso active peptide
During swallowing what substances cause constriction of the esophagus?
ACh
Substance P
How long does swallowing take?
8 - 10 seconds
What cranial nerves are involved in afferent stimulation of swallowing?
Trigeminal : V
Glossopharangeal : IX
What cranial nerves are involved in efferent stimulation of swallowing?
Trigeminal: V
Glossopharangeal: IX
Vagus: X
Hypoglossol : XII
What is the enzyme that converts Non Heme (Fe3+) into Heme Iron (Fe2+)
Duodenal Cytochrome B
Which transporter moves Fe2+ out of the lumen and into the cell and what cell is this?
Divalent Metal Transporter - 1
Enterocyte
What is the Transporter that moves Fe2+ out of the enterocyte and into the blood?
Ferroportin -1
What hormone released by the liver inhibits the movement of Fe2+ from the enterocytes into the blood and what transporter does it work on?
Hepcidin
Ferroportin - 1
What is the fate of Fe2+ when it enters the enterocyte?
Transported out of the cell into blood via ferroportin- 1
stored as:
Hemosiderin
Ferritin
What is the transporter of Fe2+ in the blood, and what happens if the levels of Fe2+ are sensed to be higher? and what if sensed to be lower?
Transferrin
if high levels of Fe2+ , the synthesis of transferrin decreases
if levels are sensed to be low then synthesis of transferrin increases
What are the two major movements of the small intestines?
Segmentation
Peristalsis
What controls peristalsis with brief overview
Myenteric plexus
Ascending: circular constriction - ACh and Substance P
Descending - dilation and longitudinal - NO and VIP
What is the electrical activity that governs the contractions in the small intestines?
Basic Electrical Rhythm
What is the BER in the small intestines?
Duodenum: 12/ min
Jejunum: 10/ min
Ileum: 9/ min
What are the folds in the Intestine called?
Plicae Circularis / Valves of Kerkring
What is at the bases of the Villi and where are they most prominent?
Intestinal Glands
Most commonly seen in Jejunum
What cells are found in the intestinal Glands?
Stem Cells
Entero - endocrine cells
Panath cells
What do Entero - endocrine cells release?
CCK
Secretin
5 - hydroxytryptamine - serotonin
In the ileum what defensive structure is found in the submucossa and what cells are present?
Peyer’s patch’s
M - cells
Dentritic cells
lymphocytes
What is the most potent stimulation for pancreatic enzyme release?
CCK - stimulation of pancreatic enzymes release
Secretin - stimulation of Bicarbonate
VIP - relaxation of ampulla of vater
What is the stimulator for bicarbonate secretion from the pancreas?
Secretin
and
Vagus reflex
What cells in the pancreas produce Bicarbonate?
Intercalated duct cells
What Can be a useful distinguishing feature of duodenum?
Lack of mesentery
What nerve controls the external anal sphincter?
Pudendal Nerve
What is the transporter than secretes Cl- into the lumen called?
Cystic Fibrosis Transmembrane Regulator
At the intestinal glands Cl- is secreted, with Na2+ and H2O following. These are then reabsorbed with more. what is the process of secretion and re absorption called?
Fluid Circuit Hypothesis
For the absorption of di and tri peptide chains - what is the driving force?
H+ ions which were pumped out in order to create a gradient to allow their absorption
Single amino acids are co-absorbed with?
Na2+
What is the protein that regulates Cl- secretion in the G.I system?
Cystic fibrosis trans-membrane regulator
What GLUT receptors are present on the small intestines? and what does each transport?
GLUT 1:
co transporter with NA2+ and glucose
GLUT 5:
Fructose
GLUT 2:
on basal lateral aspect. transports glucose etc into blood
What is the functions of the greater omentum?
- Fat disposition
- infection and wound localisation control
- Immune contribution
Can be used during surgery of pelvic cavity to reduce spread of infection
What do the I cells release?
CCK
What is the normal LOS pressure?
10-15mmHg
How long is the normal oesphagus?
~25cm long
What receptor does Gastrin on the parietal cells stimulate?
Cholecytokinin - 2 receptor
What type of protease is pepsin and trypsin?
Endopepsidases
What glucose transporter found in the small intestines?
SGLT-1
Through which intracellular processes does ACh and Gastrin produces HCl?
Activation of Phospholipase C > IP3 and DAG > Protein kinase > activation of tubular vesicles
Through which intracellular processes does Histamine Activate HCl production?
Adenly cyclase > cAMP > Protein kinase A
What hormone is related to Gastrin?
CCK
What cells release CCK?
I cells of the duodenum
Where does GIP come from?
K cells of the duodenum
Outwith reducing reducing the stomach activity, what else will GIP do, and why?
Stimulate insulin from pancreas.
this is because it is an incretin.
What are the layer’s of the external muscle of the stomach from inside to outside?
Oblique > circular > longitudinal
Name some disease which cause unconjugated bilirubin in the blood.
Anemia haemloylsis - malaria
Gilbert’s syndrome
Viral Hepatitis
Yellow fever
What protects the stomach from acid?
Mucus production
tight junctions
bicarbonate release
What are the non-proteolytic enzymes from the pancreas?
Lipases
Amylase
Ribonucleases
Deoxyribosnucleases
How much Iron is needed to be absorbed per day?
20mg
With regard to the muscle, how does peristalsis work?
First: Circular contract behind bolus
Second: longitudinal contract in front shortening the tube