Selected Topics In GIT Flashcards
Mention the parts of the GI tract
- Mouth
- Pharynx
- Oesophagus
- Stomach
- Small intestine
- Large intestine
Mention the accessory organs of the GIT
- Tongue
- Salivary gland
- Pancreas
- Liver
- Gall bladder
Explain the characteristics of GI smooth muscle?
- Slow waves: are slow undulating changes in the resting membrane potential. They occur rhythmically, having an intensity varying between 5 and 15millivolts
What are the electrical pacemakers for smooth muscles?
The electrical pacemakers are called interstitial cells of Cajal
Mention some factors that depolarise the membrane
- Stretching the muscle
- Stimulation by acetylcholine
- Stimulation by parasympathetic nerves that secrete acetylcholine at their endings
- Stimulation by several specific Gastrointestinal hormones
Talk about the submucosal plexus
- It is found in the inner wall of the intestine, specifically within the submucosa.
- It controls localised functions
- It regulates local absorption
- Manages contraction of submucosal muscles, influencing mucosal infolding
Mention factors that make muscle fibres less excitable
- Effect of Norepinephrine or epinephrine on fibre membrane
- Stimulation of the sympathetic nerves that secrete mainly Norepinephrine at their endings
What glands are responsible for saliva secretion.
Discuss?
The major glands are;
1. Parotid gland: secrete almost entirely the serous type of secretion.
2. Submandibular gland secrete both the serous and mucus.
3. Sublingual gland secretes mucus
4. Buccal glands secrete only mucus
The saliva has 2 types of protein secretion, what are they?
- A serious secretion (containing ptyalin)
- Mucus secretion (contains mucin)
What is the range for daily secretion of saliva?
Daily secretion of saliva normally ranges between 800ml-1500ml.
The average is 1000ml
Mention all the daily secretions of the GIT, their volume and pH?
- Saliva (1000ml daily, pH: 6.0-7.0)
- Gastric secretion (1500ml daily, pH: 1.0-3.5)
- Pancreatic secretion (1000ml, pH: 8.0-8.3
- Bile (1000ml, pH: 7.8)
- Small intestinal secretions (1800ml, pH: 7.5-8.0)
- Brunner’s gland secretion (200ml, pH: 8.0-8.9)
- Large intestinal secretion (200ml, pH: 7.5-8.0)
What is the total volume of daily secretions?
6700ml
What glands secrete saliva?
Saliva is secreted by
1. Parotid glands : secrete almost entirely the serous type of secretion.
2. Submandibular gland: secrete both serous and mucus
3. Sublingual gland: secretes mucus
4. Buccal gland: secrete only mucus
What is the pH of saliva?
Saliva has a pH of 6.0-7.0
Explain the mechanism of saliva secretion
Saliva secretion is a 2 stage operation.
1. Primary secretion: Saliva begins as an isotonic fluid (similar to plasma). Acinar is responsible for primary secretion. It also secrets different proteins and enzymes like amylase.
2. Ductal modification: as the primary secretion moves through the ducts system of the salivary glands, reabsorption of Na and Cl- ions from the primary fluid into ductal cells and then back to bloodstream, occurs.
What are the components of saliva?
Water: 97-99%
Other constituents are;
1. Salivary amylase(ptyalin)
2. Mucin
3. Kallikrein
4. Lysozyme
5. Inorganic constituents like; Bicarbonate (HCO3), Chlorine ion (Cl-), Phosphate (PO-4), sodium ion (Na+), potassium ion(K+) , calcium ion (Ca2+), magnesium ion(Mg)
Enumerate the functions of saliva
- Saliva helps to wash away Pathogenic bacteria as well as food particles.
- Saliva Contains lysosomes and thiocyanate ions. Lysosomes attack bacteria and also activate thiocyanate to become bactericidal.
- Saliva protects and prevents dental caries.
- Saliva Contains ptyalin which begins digestion of carbohydrates to maltose and iso-maltose.
- Saliva lubricated food for swallowing
- It aids in speech by facilitating movements of the lips and tongue
What are the components of saliva?
Water: 97-99%
Other constituents are;
1. Salivary amylase (also called ptyalin)
2. Mucin
3. Kallikrein
4. Lysozyme
5. Inorganic constituents like; bicarbonate (HCO3), chlorine(Cl-), sodium(Na+)
Briefly explain nervous regulation of salivary secretion
Salivary glands are controlled mainly by parasympathetic nervous signals from the superior and inferior salivary nuclei in the brainstem.
How does saliva control blood vessels?
Kallikrein, secreted by salivary cells, acts as an enzyme to the blood protein alpha 2-globulin, to form Bradykinin, a strong vasodilator.
What is mastication?
Mastication is also called chewing. It is a mechanical process through which the teeth grinds the food into small pieces, before it is rolled into bolus and swallowed through the residue for further digestion
Can you explain the control of mastication.?
Mastication involves both voluntary and involuntary control (chewing reflex).
The voluntary is primarily controlled by nuclei in the brainstem.
This nuclei controls the motor branch of the trigeminal nerve, which controls the muscles of mastication such as
1. Masseter
2. Buccinator
3. Temporalis
4. Pterygoid
Can you correctly list the order of movement in the GI tract?
- Mouth
- Pharynx
- Oesophagus
- Stomach
- Small intestine
- Large intestine
- Rectum
Swallowing is otherwise called?
Deglutition.
What are the stages of deglutition (swallowing)?
- Oral stage
- Pharyngeal stage
- Oesophageal stage
The pharyngeal stage is involuntary and comprises the passage of swallowed food from mouth to the esophagus.
Can you list the event cascade from deglutition?.
When food leaves the mouth for the pharynx, swallowing receptors are activated and the following happens;
1. The uvula is pulled upwards close to the posterior nares to block backflow of food into the nasal cavities
2. Palatopharyngeal folds are pulled towards the middle to narrow the space and allow passage of only properly chewed food.
3. The trachea and larynx are elevated and closed against the epiglottis.
4. The upper esophageal sphincter relaxed to allow movement of God from pharynx into the esophagus.
5. Sequential contraction of superior, middle and inferior constructor muscles of the pharynx to kickstart peristaltic waves.
Define deglutition apnea?
Deglutition apnea is the temporary cessation of breath when the epiglottis covers the trachea to prevent food from entering the respiratory tract.
What movement happens in the oesophagus?
Movement in the oesophagus is Peristalsis.
Peristalsis is the periodic/sequential contraction and relaxation of the oesophagus to convey bolus through to the stomach.
Briefly talk about nervous control of deglutition?
The swallowing centre is located at the nucleus of the tractus solitaries and nucleus ambiguous
Cranial nerve IX is concerned with pharyngeal stage of swallowing
Cranial nerve X is concerned with oesophageal stage
What is Achalasia?
Achalasia is the accumulation of food in the oesophagus. This results from failure of the gastroesophageal sphincter to relax properly to allow food pass normally
What is Chalasia
Chalasia is a condition where there is lower oesophageal sphincter incompetence, which easily allows reflux of gastric contents to the oesophagus.
It can be treated by avoiding intrusive food and taking anti-cholinergics.
What are anti-cholinergics?
Anti cholinergics are drugs that block the action of acetylcholine.
By inhibiting acetylcholine, these drugs can reduce involuntary muscle movements and secretions in various parts of the body.
What is enterogastric reflex
Entero- refers to the small intestine
Gastric- refers to the stomach.
Hence, enterogastric reflex refers to a reflex that regulates flow of chyme from the stomach into the small intestine.
Enterogastric reflex inhibits the flow of food into the intestine to prevent overloading
Mention some factors that promote enterogastric reflex
- Duodenal distension
- Irritation of duodenal mucosa
- Acidity
- Osmolality of chyme
What is gastrocolic reflex
Gastrocolic reflex is a reflex that increases the activity of the pyloric pump and relaxes the pyloric sphincter
What are some hormones that influence gastric emptying?
- Secretin
- CCK: Cholecystokinin
- VIP: Vasoactive inhibitory peptide
- GIP: Gastric inhibitory peptide
Explain emesis?
Emesis is also called Vomiting.
Vomiting is the abnormal reverse of gastric motility. It begins with antiperistalsis in the ileum.
Vomiting is caused by many different factors,such as;
1. Drug
2. Pregnancy
3. Irritating/nauseating sights
4. Doors
5. Tastes
There are 4 types of movement in the small intestine. List and explain them.
- Segmentation movement: also known as mixing movement.
- Peristaltic movement: also known as propulsive movement.
- Pendular movements: is the sweeping movement of the small intestine, like that of a pendulum.
This movement aids mixing of chyme with digestive juices. - Villous movement: is a movement of the small intestinal villi. It is usually initiated by the contraction and relaxation of the muscularis mucosa of the intestinal wall.
What is Defecation?
Defecation is the act of passing out faeces. It involves contraction and relaxation of internal and external anal sphincters.
What makes the stomach bulge out?
Vasovagal reflex.
It acts to adjust the muscle tone of the stomach wall, so it can bulge out.
The stomach does not digest itself, but sometimes it does. Explain this?
The stomach contains HCl, a very corrosive acid, which plays a vital role in the stomach.
Typically This HCl doesn’t do any damage to the stomach due to presence of
1. Gastric mucosa barrier
2. Tight junctions
3. Prostaglandins : which stimulate mucus and bicarbonate secretion and promote blood flow to the stomach lining
4. Epithelial cell renewal: this just means that cells renew every 3-7days.
What is autodigestion of the stomach?
Autodigestion occurs when protective mechanisms fail, allowing stomach acid and enzymes to damage the lining.
What are the causes of auto-digestion in the stomach?
- H. Pylori
- Overuse of NSAIDS
- Excessive acid secretion to illness (such as Zollinger-Ellison syndrome)
- Stress and lifestyle factors
- Bile reflux: disrupts the mucosal barrier, often causing inflammation and damage
- Delayed gastric emptying
What are the stages of gastric acid secretion?
There are 4 stages.
1. Basal
2. Cephalic
3. Gastric
4. Intestinal
What is Uremia?
Uremia is blood poisoning resulting from retention of waste products(usually urine)
What is Volvolus?
Volvolus is when the bowel is blocked because of a loop(twist) has occurred.
What are the risk factors for stress Ulceration?
- Shock
- Sepsis, especially peritonitis
- Respiratory failure
- Hepatic failure
What are some risk factors for gastric barrier disruption?
- Hypoadrenocorticism
- Liver disease
- Uremia
- Sepsis (endotoxemia)
- Renal failure
- Respiratory failure
- Hepatic failure
Mention some proteolytic enzymes (enzymes that digest proteins) from the pancreas.
- Trypsin
- Chymotrypsin
- Carboxypolypeptidase
What pancreatic enzyme digests carbohydrates?
Pancreatic amylase
What pancreatic secretions digest fats
- Pancreatic lipase
- Cholesterase
- Phospholipase
The pancreas produces and stores digestive enzymes, but it does not digest itself. Explain?
There’s presence of trypsin inhibitor,
Also enzymes are produced and stored in inactive form, e.g
Trypsinogen, chymotrypsinogen,… And only get activated when secreted into the intestine
Mention some hormones that regulate pancreatic secretions?
- Acetylcholine
- Cholecystokinin
- Secretin
What is Brunner’s gland and why is it important?
Brunner’s gland is located in the wall of the first few centimeters of the duodenum.
The Brunner’s gland protects the duodenal wall from digestion by highly acid gastric juice emptying from the stomach. It contains mucus containing large quantity of bicarbonate.
Give examples of monosaccharides?
- Glucose
- Fructose
- Galactose
Give examples of disaccharides.?
- Sucrose
- Lactose
Give examples of polysaccharides?
- Glycogen
- Starch
- Cellulose
- Amylose
- Amylopectin
- Dextrin
Can you explain the synthesis of HCl in the parietal cells of the stomach?
Co2 diffuses into parietal cells and combines with H20 (water), catalysed by carbonic anhydrase to form carbonic acid (H2Co3).
H2CO3 dissociates to H+ and HCO3(bicarbonate).
H+ is transported into stomach lumen via H+/K+ ATPase pump.
Cl- enters parietal cells via chloride-bicarbonate exchange and is secreted into the lumen through Cl- channels.
H+ and Cl- combine in the lumen to form HCl.
Define Gastroparesis?
Gastroparesis is delayed gastric emptying.
Talk about the Liver?
The liver is a vital organ
The second largest in the human body, involved in metabolism, protein synthesis and bile production.
The liver is surrounded by
1. Diaphragm above
2. The gall bladder below
3. The stomach beside
4. The kidney behind
Talk about the lobes of the liver.
Functionally the liver has 2 lobes,
1. Right lobe
2. Left lobe
Anatomically, the liver has 4 lobes..
3. Caudate lobe
4. Quadrate lobe
The right and left lobes of the liver are separated by?
Falciform ligament
Mention some metabolic functions of the liver
The liver has metabolic and non metabolic functions..
Some metabolic functions include:
1. Glycogenesis
2. Glycogenolysis
3. Gluconeogenesis
4. Conversation of galactose & fructose to Glucose.
- Synthesis of albumin
- Synthesis of clotting factors and urea
- Deamination
- Synthesis of cholesterol
- Synthesis of lipoproteins
- Synthesis of triglycerides
- Vitamin metabolism and storage, e.g Vit K is synthesized in the liver
Mention some non- Metabolic functions of the liver
- Detoxification and biotransformation
- Production of bile
- Immune function.
- Hemopoietic function
- Hemolytic function
- Hemolytic function
- Storage and Maintenance of fluid balance
The functional unit of the liver is?
Hepatic Lobule.
Each Lobule is a cylindrical structure made up to liver cells which are arranged in columns to form a hepatic plate.
Explain Liver Function tests?
Liver function tests are also called hepatic panel. They are blood tests to monitor liver function and damage.
When hepatocytes are injured, their contents including liver enzymes, leak into blood stream. The levels of these enzymes can be measured to ascertain the extent of the damage.
Mention 2 examples of such enzymes?
- Aspartate aminotransferase (AST)
- Alanine amino transferase (ALT)
What are some liver functions that can be tested for, when trying to diagnose a diseases liver?
- Synthetic function
- Extent of liver damage
- Bilirubin processing function
- Galactose tolerance test
- Hippuric acid test
- Bromsulphalein excretion test
Explain the Biliary system?
Biliary system refers to the production, secretion and release of bile. Bile is secreted by cholesterol synthesis by hepatocytes.
It contains 97.6% water and other solids which make up the other 2.4%.
The Biliary system is like plumbing network of your liver and gallbladder that handles bile.
What is bile?
Bile is a greenish-yellow fluid that the body uses to emulsify(digest) fats.
The digestive system has it’s own nervous system, called?
Enteric Nervous System.
Mention some characteristics of GI hormones.
- They are peptides
- They are not secreted by endocrine glands, but by individual entero-endocrine cells within the GIT .
- GI hormones support the function of the organ that release them. Their actions are mostly restricted to the GI tract, hence it is considered a local hormone
Examples of GI hormones?
- Gastrin
- Somato statin
- Secretin
- Cholecystokinin
- Gastric inhibitory peptide (GIP)
- Vasoactive intestinal peptide
- Glucagon
- Pancreatic polypeptide
- Peptide YY
- Neuropeptide Y
- Motilin
- Substance P
- Ghrelin
What are the possible causes of hyposalivation.?
- Fever
- Dehydration
- Absence of salivary glands, ⁴
- obstruction of salivary ducts (sialolithiasis)
- Bells palsy
What are some disorders of the mouth, pharynx and esophagus?
- Disorder of saliva secretion
- Dysphagia
- Achalasia
- Gastroesophageal reflux disease
- Vomiting
Explain Dysphagia
Dysphagia is difficulty swallowing.
It can be caused by mechanical obstruction of the esophagus, pharyngeal and esophageal muscular disorders or even decreased movement of the exodus for to neurological disorders
What is GERD
GERD means, Gastroesophageal Reflux Disease.
It is a disorder characterised by reflux of acidic contents from the stomach back to the esophagus..
This happens due to weakness of the lower esophageal sphincters(it can’t close properly).
The symptoms are heartburn, and esophagus
It can be treated using anticholinergics or surgery.
Mention some disorders of the stomach?
- Gastritis
- Peptic ulcer disease
- Gastric atrophy
- Zollinger-Ellison syndrome
- Gastroparesis
Mention some of the disorders of the small intestine?
- Malabsorption
- Sprue
- Crohn’s disease
- Celiac disease
Mention some disorders of the large intestine?
- Constipation
- Diarrhea
- Ulcerative colitis
- Appendicitis
Mention some disorders of accessory organs of digestion?
Gall bladder disorders e.g;
1. Gallstones
2. Cholecystitis
Liver disorders e.g;
1. Jaundice
2. Hepatitis
3. Liver cirrhosis
4. Alcohol liver doses
Pancreatic disorders e.g
1. Pancreatitis
