Digestion and Absorption Flashcards
What is the difference between Cavital digestion and membrane digestion?
Cavital digestion refers to digestion resulting form the action of enzymes secreted by the salivary glands, stomach, and pancreas.
Membrane digestion refers to hydrolysis by enzymes synthesized by epithelial cells.
What is folds of Kerckring?
The surface of the small intestinal longitudinal folds
What are the common cell types found in the intestinal epithelium?
- Enterocytes
- Goblet cells
- Paneth cells
Which intestinal cells is responsible for mucosal defense against infection by secreting agents that destroy bacteria and/or produce inflammatory response?
Paneth cells
Which cells of the intestinal mucosa are responsible for physical, mechanical and immunological defense?
goblet cells
True or false: The small intestine is resistant to adaptation.
False. Adaptation is key in several clinical scenarios like bowel resection, bypass and etc.
Which form of sugar is absorbed by the enterocytes?
monosaccharides.
Carbohydrates are broken down into what three simple sugar to absorption?
Glucose, galactose and fructose
Starch is broken down into what poly/disachs before it its broken down into it’s simplest form of glucose
Starch via a-amylase –> Dextrin, maltose , maltotriose. –> glucose
Lactose is broken down by lactase into what?
glucose and galactose
True or false. Glucose, galactose and fructose uses secondary active transport to get into enterocytes.
False. Only glucose and galactose uses secondary active transport. Fructose uses GLUT5 as facilitated diffusion.
What secondary active transports do Glucose and galactose use to get into enterocytes?
SGLT1
What transport mechanism do fructose use to get into the enterocytes?
GLUT5
What transport system fruc, glu, and gal use to get into the blood?
GLUT2 - faciliated diffusion
Osmotic diarrhea is a result of lack of what enzyme that which breaks down disarch?
Lactase
Pepsinogen is broken down into pepsin via what?
low pH
Where does trypsinogen get converted in trypsin and by what?
In the small intestine by enteropeptidase located on the brush border.
Trypsin helps break down what other enzymes?
chymotrypsinogen, proelastase, Procarboxypeptidase A and B.
What are some examples of endopeptidases?
pepsin, trypsin, chymotrypsin, and elastase
What are some exmaples of exopeptidases?
Carboxypeptidase A and B.
Describe the breakdown of protein starting in the stomach.
In the lumen of stomach proteins are broken down into aa and oligopeptides by pepsin. In the small intestine oligopeptides are further broken down by trypsin, chymotrypsin, elastase, carboxypeptidase A and B into aa, di and tripeptide. Remaining oligopeptides can be further broken down by peptidases found on the brush border.
How do AA get transported into enterocytes from the lumen?
AA uses Na-dependent cotransporter which uses a different transporter for differnt types of AA: neutral, basic, acidic, and imino aa.
Di and tripeptides are H+ dependent cotransporter.
How do AA get from enterocytes to the blood?
They use Facilitated diffusion which uses a different transporter for differnt types of AA like neutra, basic, acidic, and imino.
What are the two major causes of disorders of protein assimilation?
- Deficiency of pancreatic enzyme
2. Defect in transporterof the intestinal epithelial cells.
What transporter is missing in Cystinuria?
Na/Amino acid cotransporter. Transporter for Di basic, amino acid (cystine, lysine, arginine, and ornithine) are absent from the small intestine and kidney. Those aa are thus secreted in feces.
What is the cause of Hartup disease?
Cannot absorb neutral amino acids (like tryptophan) due to genetic mutation of SLC6A19 gene which is responsible for the neutral amino acid cotransporter.
Symptoms of what is similar to pellagra?
Hartup disease.
What are the symptoms associated with Hartnup disease
Diarrhea, Mood changes, neurological probelms, Dermatitis, photosensitivity, short stature, uncoordinated movements
Patient urine sample tested positive for typtophan and it’s by products. Patient also presents with dermatitis, diarrhea and mood changes. WHat is the likely dignosis?
Hartup disease
Mutation in what CFTR is associated with disturbance of transport of what ion?
Chloride ion
TG are broken down into what by what?
TG is broken down into MG and FA by lingual, gastric and pancreastic lipases.
Cholesterol esters are broken down into what, by what?
Broken down into Cholesterol and FA by cholesterol ester hydrolase
Phospholipids are broken down into what by what?
Broken down into lysolecithin and FA by Phospholipase A2
Lipids cannot readily enter the enterocytes, what must be done to them before they can enter enterocytes?
They have to be packaged into micelle.
There are no bile acids in the stomach, what performs the emulsifying action of lipid droplets in the stomach?
Dietary proteins
How does pancreatic lipase get activated in the intestine?
Colipase, which replaces biles from lipase and activates it.
Lack of ApoB proteins on chylomircons leads to what disease?
Abetalipoproteinemia.
What are some signs and symptoms you’d see with small intestinal bacterial overgrowth?
Bacteria can deconjugate bile salts and making them unable to form miscelle. they can so damage intestinal mucosa and cause gastric acid secretion inhibition and small intestinal dysmotility. Some signs you’d see are chronic diarrhea, weight loss, and malabsorption
How does the intestinal surface area change with tropical sprue?
Tropical sprue causes reduction in the # of intestinal epithelial cells which in turn reduces the microvillar surface area. This leads to lipid malabsorption.
What are some signs and symptomps of troical sprue?
- Nutritional deficiencies especially folate and vitamen B12
2- diarrhea - cramps, nausea, wieght loss, gass and ingestion
What are some treatment option for tropical sprue?
Tetracycline and folate for 6 months
What is the pathophysiology of celiac sprue?
It’s an autoimmune disorder where antibodies develop against a component of gluten -gliadin- that leads to destruction of the villi in the small intestine (atrophy) as well as hyperplasia of the intestinal crypts
What are the clinical manifestation of celiac sprue?
malabsorption related to deficiencies in vitamin B12, folate, iron, calcium, vitamin D, and vitamin A
What are some Gi symptoms of Celiac Sprue?
Abomdinal pain, constipation, diarrhea, unexplained weight loss, vomitting and nausea, steatorrhea. Other symptoms related to malsborption of nutrients: tingling or numbness in the hands feet, itchy skin with a rash, fatigue, sezires, easy brushing, bone fractures
How are water-soluble vitamins absorbed?
Na-dependent cotransport mechanism in the small bowel.
In the ileum what transporter brings B12 into the enterocytes?
Transcobalamin II
What is the cause of Pernicious anemia?
Stomach does not produce enough IF, decrease vitamin B12. Two causes: 1. atrophic gastritis = inflamation = loss of parietal cells.
2. Autoimmune attacks IF protein or gastric paritel cells (autoimmune metaplasstic atrophic gastritis)
What is the pathway of vitamin D activation starting from diet or sun?
7-dhydrocholesterol activated by sunlight to cholecalficerol (D3) which you can also get from diet. D3 then in the liver it is converted to 25 hydroxy D3. 25-hydroxy-D3 goes tot he kidney and via PTH, it is converted to 1a-hydroxylase to 1.25 dihydoxy D3 which is the active form of vit D.
What ions are inadequate due to malabsorption of vitamin D
Ca. lack of which can cause Rickets and osteomalacia.
