PL7 - Secretions of Small & Large Intestines

State 3 factors which increase the secretion of Brunner's gland.

1. Vagus stimulation. 2. Direct tactile stimulation or irritation of duodenal mucosa. 3. Secretin.

Absorption of amino acids is faster in duodenum and jejunum and slower in ileum. True or False.

True!

Appendices epiploicae which is the small peritoneal bags of fat project from the colonic mucosa. True or False.

True!

Out of 7 to 10 liters of GI gases, average amount expelled as flatus is about 0.6 liter. The remainder is absorbed into the blood and expelled through lungs. True or False.

True!

Brown color of feces is caused by?

stercobilin and urobilin (derivatives of bilirubin)

State the function of: 1. Goblet cells 2. Argentaffin cells 3. Zymogen cells or Paneth cells 4. Duodenal glands of Brunner

1. Goblet cells: secrete mucus. 2. Argentaffin cells: secrete 5-hydroxytryptamine (5-HT, serotonin) 3. Zymogen cells or Paneth cells: produce lysozyme which destroys bacteria. 4. Duodenal glands of Brunner: secrete HCO3- & mucus.

State 3 sources of gastrointestinal gases (flatus).

1) Swallowed air in stomach -mixtures of nitrogen and oxygen, expelled by belching. 2) Gases formed as a result of bacterial action in the large intestine - include carbon dioxide, methane, and hydrogen. 3) Gases that diffuse from the blood into GIT.

State 3 features of the mucosa of large intestine.

1. Absence of Plica circulares & villi. 2. Thrown into folds opposite to the contraction - sacculations. 3. Crypts of Lieberkuhn lined by simple columnar epithelial cells with large number of goblet cells which secretes mucus are the special features of mucosa of large intestine. 4. Epithelial cells contain no enzymes

Name 4 type of epithelial cells in the mucous membrane & intestinal glands of small intestine

1. Absorptive columnar cells (enterocytes). 2. Undifferentiated columnar epithelial cells. 3. Goblet cells. 4. Argentaffin cells. 5. Zymogen cells or Paneth cells. 6. Duodenal glands of Brunner.

State 2 features of the bacterial flora.

1. At birth colon is sterile , becomes established early in life. 2. Harmless bacteria such as E- coli & Enterobacter aerogenes. 3. Potentially dangerous bacteria such as bacteroides fragilis, various type of cocci & gas gangrene bacilli. 4. Produces various gases that contribute to flatus in the colon.

Large intestinal bacterial activity can be grouped as?

1. Beneficial 2. Indifferent 3. Detrimental

Name 2 component which secrete the mucus in the small intestine.

1. Brunner's Glands- secrete thick alkaline mucoid secretion, play protective role. 2. Goblet cells - which secretes lot of mucus which protects the intestinal mucosa & lubricates the chyme.

Aminoacids, dipeptides and tripeptides are absorbed through the luminal epithelium by separate transporters (carriers) present for the absorption of basic, acidic and neutral amino acids. Describe.

1. By binding of amino acids and Na+ to carrier protein. 2. By creation of electrochemical gradient across the epithelial cells by Na+ -K + ATPase; movement of Na+ and amino acids towards the inside of the cells.

State 2 detrimental (harmful) bacterial activity of large intestine.

1. Consumption of nutrients like Vit C ,B12 & choline by some bacteria lead to deficiency symptoms. 2. Production of ammonia by bacteria is absorbed by blood & normally detoxified quickly by liver.

State 3 beneficial bacterial activity in the large intestine.

1. Digests small amounts of cellulose, providing a few calories. 2. Synthesis vitamin K, vitamin B12, thiamine, riboflavin 3. Trophic effect of colon mucosa. 4. Decreases the plasma cholesterol & LDL levels

Name 2 actual odoriferous products of faeces

1. Indole 2. Skatole 3. Mercaptans 4. Hydrogen sulfide

State the cause & result of lipid malabsorption.

1. Lipid malabsorption is much more common than carbohydrate and protein malabsorption. 2. Because of deficiency of pancreatic lipase as in pancreatic diseases. 3. Steatorrhoea, increased amount of fat in the stools is a common manifestation of fat malabsorption.

Name 3 regulation of small intestinal secretions.

1. Local stimuli: Mechanical distension or irritation by chemicals via local myenteric reflexes, increases the volume & total enzyme output of the small intestine. 2. Role of vasoactive intestinal peptide (VIP): increases the secretion. 3. Secretion Of Brunner's Gland.

Large intestinal secretion consist of enormous amount mucus secreted by the goblet cells. State the function of mucus.

1. Lubricate the fecal matters. 2. Prevent the mucosa of large intestine from mechanical & chemical injuries.

State the unique characteristic of longitudinal muscle layer of colon

1. Most of the fibers collected to form three thick bands, Taenia coli. 2. Taenia coli is shorter in length than the other walls of the colon. 3. Production of sacculations (haustrations) on the wall of the colon.

Brush border of small intestine contains a large number of intracellular digestive enzymes. Name 3 enzymes.

1. Peptidases (proteolytic enzymes). 2. Disaccharidases. 3. Intestinal lipase. 4. Enterokinase.

State 3 indifferent bacterial activities of large intestine.

1. Production of intestinal gases - 7 to 10 L /day. 2. Formation of organic acids - acidic reaction of the stools. 3. Substance for odor of faeces - indole, skatole & mercaptans. 4. Potentially toxic amines like histamines & tyramines. 5. Pigments for the color of the stool.

State the mechanism of secretion of aqueous component in the secretion of small intestine.

Active secretion of HCO3 - & Cl- & diffusion of Na+ . All these ions causes the osmotic movement of water. + Total amount : two liters per day ; pH 7.6 - 8.6

State the result of absorption of sodium and chloride ions in the large intestine.

Causes absorption of water due to osmotic gradient across the large intestinal mucosa

A congenital defect in the transport of basic amino acids.

Cystinuria.

State the composition of faeces

Faeces contains ¾th water and 1/4th solid matter composed : 1. dead bacteria 2. fat 3. inorganic matter 4. protein 5. undigested roughage

Malabsorption of neutral amino acids due to lack of specific carrier protein.

Hartnup disease.

State the structure at luminal surface of enterocytes

Microvilli. 1. Increases the surface area to some 30 fold and microvilli covered by mucus - glucocalyx. 2. Enzymes such as small peptides & disaccharides are associated with microvilli.

What is succus entericus?

Secretions of small intestine which consist of Aqueous component (water &electrolyte), intestinal enzymes & mucus.

What is lactose intolerance?

The inability to fully digest sugar (lactose) in dairy products.