Flashcards in Gastrointestinal Physiology - Theoretical Questions Deck (127)
Where can we find the Interstitial Cajal Cells?
Myenteric Plexus, Part of the ENS (Intrinsic)
What is the cause of the Phasic contractions in the GI tract?
Phasic contractions or Peristalsis are caused by Gq mechanisms of Muscarinic Ach receptors (M1/3/5) that cause Ca2+ channels to open and form an AP on top of the Slow wave electrical amplitude. (Extrinsic NS)
What are the Phases of Swallowing?
Muscles involved and Reflexes
Masseter, Medial Pterygoid and Temporalis are responsible for Opening mouth and Lateral Pterygoid for closing it. The Masseteric reflex (V3) coordinates and Senses the voluntary movement (proprioception)
What happens in the Oral phase of Swallowing?
Voluntary movement of the Tongue - Tip goes forwards and Base goes backwards. This pushes the Food bolus backwards to the Oropharynx.
What happens in the Sensory Part of Pharyngeal phase of Swallowing?
Esophageal, Palatal and Pharyngeal Mechano- and Thermo - and Taste receptors detect the bolus and send via V3+IX+X the information to Swallowing center in the Medulla oblongata .
What happens in the Motor Part of Pharyngeal phase of Swallowing?
This is a Involuntary directed by the Medulla Oblongata center - 3 muscle actions: 1) Soft palate elevation 2) Epiglottis depression 3) Upper esophageal sphincter relaxes.
What happens in the Esophageal phase of Swallowing?
The vagovagal reflexes cause of the tube distension cause release of VIP to the SMCs of the Esophagus guide the bolus way to the Lower Esophageal sphincter.
How long does it take for Solid and Liquid foods to reach the stomach?
Solid - 10 sec
Liquid - 1 Sec
What is the Receptive Relaxation ?
Vagovagal reflex allowing the relaxation of the Lower Esophageal Sphincter and Orad part of Stomach. Destination causes the reflex and VIP is the Neurotransmitter (Like in rest of esophagus)
What is the Intraesophageal pressure equal to?
It is Equal to the Intrathoracic pressure
What happens if the Primary peristaltic wave doesn't push all the bolus to below?
Vagovagal Reflex cause Secondary Peristaltic reflex
What is the names of the Proximal and Distal parts of the stomach (Not Pyloric Antrum/Body/Fundus)
Proximal - Orad Part
Distal - Caudad Part
What is the name of the digested food that leaves the stomach?
What are the cell kinds on the different positions of the Mucosa of the stomach?
Fundus - Parietal cells
Body - Chief cells
Pyloric Antrum - Mucus and G cells
What extra lamina are in the inner part of the Muscularis externa?
What are the Particle size of chyme able to pass through the Pylorus? What happens if they are bigger?
1 mm particles can go through the Pylorus, if they are smaller they get pushed back (Repulsion) for further mechanical and chemical breakdown.
What is the muscular part responsible for the mechanical breakdown in the stomach? although the rhythm is pretty (constant 3 per min ) what elevates the contraction forces?
Cauded part is a strong contraction area which is further increased upon Gastrin stimulation (AP -f higher) when there is Amino acids or Peptides present, and is decreased by Secretin and GIP action.
What determines the length of stomach emptying time? Generally how long does it take?
1)Liquids travel faster
2)Volume of the food
3)Very Fatty or Acidic Chyme will empty more slowly.
How will Very Fatty or Acidic Chyme will empty more slowly?
High Fat will cause CCK release (Duodenum - I cells) that decreases Gastric Motility (SMC relaxation).
Acidic Chyme will cause Secretin (Duodenum - S cells) and Sympathetic action to also decrease Gastric Motility ( SMC relaxation)
Why is Acidic chyme slowing down stomach emptying?
More time for the Bicarbonate secretion of Pancreas to build up and neutralize the Acid later in the duodenum
What are the two patterns of contractions that occur in the small intestine?
Segmental contractions - Pinching Chyme in the middle
Peristaltic contractions - Propelling the Chyme forward
How are the Peristaltic Contractions propel the chyme forward? How are the contractions coordinated?
1) Contraction behind chyme 2) Relaxation infront of chyme allow 3) Repetition - creates a wavy motion of chyme forward.
The Inner circular and Outer longitudinal layers contract RECIPROCALLY one layer at the time for this .
"Larger Hole" + "Shorter tube" and vice versa.
What is the Paracrine mediator that causes the Peristalsis in the Small intestines? What are the other substances aiding here?
Enterochromaffin cells secrete Serotonin which activates the Peristaltic movements locally. Neuropeptide Y, Substance P and Ach are also released behind the chyme (Not Paracrine) for also stimulating contractions.
What happens in Vomiting ?
What happens in Retching ?
Lower esophageal sphincter opens, Acidic reflux passes.
What are the unique arrangement of contractions in the Colon?
Segmental contractions go according to the Haustra
How many times a day there are mass movements in the colon?
1-3 times a day
What happens in the Rectosphincteric Reflex?
When 25% of Rectum is Filled, SMC on wall contract, Inner Anal sphincter relaxes and Outer Anal sphincter relaxes on command (Skeletal Muscle).