Stomach 1 & 2 Flashcards
What is deglutition?
Swallowing: propulsion of food from oral cavity -> osephogus
What is food molded into by the tongue before being moved up and back to the pharynx?
Bolus
When pressure sensory cells are stimulated, the swallowing reflex is stimulated. Where is the swallowing centre in the brain?
Medulla
What temporarily closes off the trachea whilst swallowing?
Epiglottis
What are some deglutition disorders?
Failure of epiglottis
Soft palette
Pharyngeal paralysis
Botulism (clostridial toxins block AcetylCh release)
What is myasthenia gravis?
The body produces antibodies against Acetylcholine receptors, so the swallowing reflex does not work
Why are animals starved before anaesthesia?
Inhalation pneumonia
Anaesthesia induces vomiting - leads to inhalation
What are the 4 layers of the oesophagus?
Mucosal layer
Submucosal layer
Muscular layer
Serosal layer
What happens when the bolus reaches the oesophagus?
Upper oesophageal sphincter closes behind food bolus
Epiglottis opens to allow respiration
Peristaltic contractions force bolus down
Lower oesophageal sphincter opens to allow food to pass to stomach
What is the lower oesophageal sphincter also known as? What is its function?
Cardiac sphincter
Prevent regurgitation
What is the scientific word for vomitting?
Emesis
What is an anti-emetic drug?
A drug which prevents vomitting
Why is there deep inspiration before emesis?
To increase intrathoracic pressure
Whilst taking a deep inspiration, which parts of the digestive system close?
Trachea
Nasal cavity
Which muscles contract during emesis
Abdominal muscles
NOT gastric
Emesis is controlled by the medulla. What stimulates emesis?
Pharyngeal or gastric distension/irritation
Which two species do not vomit? What happens to them if they are unable to vomit?
Horses and rats
Stomach ruptures
What is gastric torsion? Which breeds are most prone to it?
The twisting of the stomach around its on axis
Any horses/dogs with a wide chest - more room for stomach to move
Why does gastric torsion prevent vomiting?
It seals off the cardiac sphincter
Gastric torsion may compromise blood supply. What does this lead to?
Oedema
Hypoxic stomach
Eventually leads to necrosis
During gastric torsion, the stomach may dilate. This may lead to emergency surgery. Why?
Stomach impairs venous return to the heart
Causes hypovolaemic shock
What are the functions of the stomach?
Digestion (continuation of starch, initiation of protein)
Protect rest of GI tract by killing bacteria
Storage (wild animals)
Mechanical breakdown and mixing
What are the 4 regions of the adult stomach? What sphincters are at the start and end of the stomach?
Cardia Fundus Corpus Pylorus Eosphogeal sphinter, pyloric sphincter
Is the oesophageal region of the stomach glandular or non-glandular?
Non - glandular
What is the purpose of motility?
To prepare stomach for meal
Mix and breakdown chyme
Empty stomach
Prevent regurgitation
What actually is ‘heart burn’?
Regurgitation of chyme into the oesophagus
What is receptive relaxation?
The process of the stomach relaxing to accommodate for food as a meal is eaten
Where is receptive relaxation regulated, and via which nerve? What is the neurotransmitter?
Swallowing centre (medulla)
Vagus nerve
VIP
Regulation of stomach emptying is hormonal or neural. When may the regulation by neural?
When in pain
When might the duodenum inhibit gastric contractions (therefore gastric emptying)?
If too much chyme is present in the duodenum
If pH is too high
What is the pH of the stomach?
2 - 2.5
What is amylase a polysaccharide of? What is the bond present?
Alpha glucose
1, 4 glycosidic bond
What is amylopectin a polysaccharide of? What is the bond present?
Alpha glucose
1,6 glycosidic bond
Starch is broken down by amylase, which is only active at pH > 6. Protein is broken down by pepsin, which is only active at a lower pH. How does the stomach deal with this?
Acid is released from stomach walls
Newly swallowed food goes to the centre
Starch is broken down in the centre (lower pH) and protein is broke down by edges of stomach (higher pH)
Why do carnivores and ruminants have no amylase in their saliva?
They have a low starch diet
Where is amylase produced?
The mouth Exocrine pancreas (back up)
Why do humans have such a high level of salivary amylase in comparison to pigs/horses?
Human stomach cannot digest starch as well as pigs and horses
What is gastric juice mainly composed of?
Hydrochloric acid
Pepsinogen (inactive pepsin, activated by stomach acid)
Why does pepsinogen need to be inactive?
Organs are made up of protein
Pepsin would digest them
Stomach mucosa is resistant to digestion. Failure of this leads to..?
Stomach ulceration
Why is HCl needed in gastric juice?
Kill microorganisms
Active pepsinogen and provide environment for pepsin to work
Degrade large chunks of CT & MT into smaller pieces
How does the duodenum cope with the acidic chyme released from the stomach?
The pancreas secretes HCO3- into the duodenum which neutralises the acid
What is the alkaline tide?
After eating, pH of blood increases due to stomach parietal cells secreting H+ into the stomach and HCO3- into the blood
Where is pepsinogen synthesised and stored?
Chief/peptic cells
Pepsin can act as an auto catalyst. What does this mean?
Pepsin can activate more pepsinogen
What are the three phases of digestion? And what happens? (In terms of gastric juice secretion and what stimulates it)
Cephalic & gastric phase - stimulates gastric juice secretion directly via acetylcholine and indirectly via gastrin in blood
Intestinal phase - inhibits gastric secretion until intestines ready fro more. Stimulated via cholinergic transmitters and gastrin/CCK
If stomach pH is less than 2, gastric juice secretion is inhibited to protect mucosa. What is responsible for this?
Hormone gastrin
The duodenum inhibits motility and gastric juice secretion by which nerve, and which 3 hormones
Vagus nerve
Secretin, CCK, GIP
How often is stomach mucosa epithelium replaced?
Every 2-3 days
When there is increased acid in the duodenum, there are decreased protective functions by the stomach. Damaged cells produce what, which leads to more acid production?
Histamine
What is the treatment for a too low pH in the stomach?
Increase HCO3 and decrease H+
Treat with antacids, antihistamines
