Anatomy & Phys Of Digestive Tract (1A) Flashcards
Describe the digestion of food starting in the mouth to the esophagus. What enzymes are secreted in the mouth and what do they break down? What mechanical digestion happens in the mouth and esophagus to bring food to stomach?
Mouth, teeth, tongue, and throat contribute to mechanical digestion of food, preparing a food bolus by biting, chewing, and swallowing. The teeth grind and crush food into small pieces, saliva moistens food and exposes it to salivary enzymes including large amounts of salivary amylase (carb hydrolyzing) and small amounts of salivary lipase (lipid hydrolyzing).
Food goes down esophagus, which is a tube running from mouth to stomach, that provides peristaltic wave like contractions. Regurgitation of food back to throat is prevented by the upper and lower esophageal sphincters. This function is performed primarily by the lower esophageal sphincter (LES) - a valve at the lower end of the esophagus that opens to allow food to pass into stomach and then closes to prevent retrograde movement of partially digested food when the stomach contracts
Stomach in digestion - Name the cells and enzymes in the stomach involved in digestion
Gastrin is secreted by gastric endocrine cells and is triggered by presence of protein. Gastrin acts on parietal and chief cells to stimulate HCl and pepsinogen. It also stimulates peristalsis and maintains the proliferation of gastric parietal cells. Increasing intragastric acidity inhibits continued Gastrin secretion
Chief cells secrete lipase (breaks down TG —> FFA and diacylglyerides) and pepsinogen (which is converted to pepsin, pepsin initiates hydrolysis of proteins)
Parietal cells secrete HCl and IF (small protein required for absorption of b12)
Mucus cells secrete mucus containing glycoproteins and bicarbonate that protects gastric mucosa from acid damage and auto digestion
What is the major anatomical site of food digestion and nutrient absorption?
The small intestine
Describe the brush border in the SI
The luminal surface of the SI which is composed of microvilli that dramatically increases the available absorptive surface area of the small intestine
Distinguish what takes place in the duodenum, jejunum, and ileum
Duodenum - chemical degradation of partially digested food into individual nutrients begins
Jejunum and ileum are major sites of nutrient absorption
Distal ileum transfers any undigested food materials into the large intestine
What is the primary role of the liver?
Excretion of bile for food digestion and nutrient absorption
What is bile made of?
Cholic acid, chenodeoycholic acid, taurine, glycine, cholesterol, electrolytes, and water (6-7 L/d on average in adults)
What are bile salts and what’s their job?
Organic and mineral components of bile FORM bile salts.
Bile salts emulsify the fine lipid droplets reaching the intestine from the stomach. Emulsification of fats in needed for pancreatic lipase and collapse to be effective
Factors that preserve intestinal barrier function
Antibacterial and antiviral secretions of nonpathogeneic micro flora
Mucus secretion
“Tight junctions”
Intestinal epithelial secretion of lectins and anti-adhesion glycoproteins
Peristalsis
___ _____ may occur when food components or bacterial antigens share a common antigenic determinant (epitope) with both a virus or other pathogenic microorganisms to which the host has been exposed previously and a host cell membrane component
Autoimmune-like disease
Ways to restore intestinal barrier function
Reduce the amount of proteinaceous residue reaching the ileum (via digestive enzymes), increase epithelial integrity (via maintaining adequate intraepithelial glutamine concentration), or support the GALT
What amino acid is the required primary fuel source for enterocytes?
Glutamine
Why would glutamine be diverted away from the enterocytes and towards the immune system?
Stress, trauma, illness
Glutamine inadequacy does what to the small intestine?
Thins villi with decreased digestive function
Decreased absorptive function
Loss of intestinal barrier integrity
Increased translocation of antigens and pathogens
The colon gets __% of it’s nutrients from the digests
70%
Why is butyrate especially important to human colonocytes?
It’s metabolized to acetyl CoA which is the primary energy source for coloncytes, and is needed for the formation and maintenance of intracellular tight junctions
