Oral & Stomach Physiology/Biochemistry - Twining Flashcards Preview

M2 GI/Nutrition > Oral & Stomach Physiology/Biochemistry - Twining > Flashcards

Flashcards in Oral & Stomach Physiology/Biochemistry - Twining Deck (22):

Give the innervation for each of the following:

  • Parotid salivary gland
  • Submandibular salivary gland
  • Sublingual salivary gland

  • CN IX
  • CN VII
  • CN VII


Give the four major constituents of gastric juice (other than water)

  • intrinsic factor
  • hydrogen ions
  • pepsin
  • mucus


Give another name for ptyalin. What does it do?

Also known as alpha-amylase

Starts carbohydrate digestion in the mouth


As new saliva travels through the ducts of the salivary gland, which ions are reabsorbed? Which are secreted?

Reabsorbed: Na+ (active) and Cl- (passive)

Secreted: K+ (active) and HCO3- (passive)


Name the major saliva component directly involved in antibacterial and antifungal defense.

Broad spectrum or narrow spectrum?



'Narrow' spectrum - most involved in killing gram-positive bacteria

Mechanism: cleaves beta-1-4 linkages between NAM and NAG (gram positive cell wall peptidoglycans) or NAG in fungi cell wall chitodextrins


Name the saliva component responsible for each of the following bacterial defenses:

  • Binds iron and prevents bacterial and some fungal growth
  • Kills bacteria by producing reactive bromide and iodine molecules
  • Secreted immunoglobulin that recognizes and binds bacteria in order to produce an immune reaction
  • Polypeptides that form pore complexes on microbial cell membranes
  • Large, highly glycosylated proteins that modulate adhesion of bacteria to oral tissues (including teeth)

  • Lactoferrin
  • Peroxidase
  • IgA
  • Defensins
  • Mucins


Saliva is low in what two ions normally found in blood plasma?

Na+ and Cl-


Desribe how the following lead to xerostomia:

  • Cystic fibrosis
  • Sjogren's syndrome

  • Mutant chloride transporters lead to defective plasma secretions. Salivary mucus is thick and may clog salivary ducts, leading to xerostomia.
  • Autoantibodies to salivary gland proteins leads to the destruction of these tissues, resulting in deficient saliva production (xerostomia)


Name and describe the three phases of gastric secretion

  • Cephalic phase
    • Anticipation of food leads to vagal stimulation of the stomach, increasing production of acid and pepsin
  • Gastric phase
    • Food in the stomach excites (1) long vasovagal reflexes to/from the brain, (2) local enteric reflexes, and (3) gastrin-histamine stimulation
  • Intestinal phase
    • Presence of food in the duodenum causes small amounts of continued gastric secretion. Continued stimulation ultimately leads to inhibition of gastric secretion/emptying by an enterogastric reflex


Describe the substances released by the vagus nerve that influence acid secretion

  • ACh
    • stimulating action -> acts on parietal cells to release acid
    • stimulating action -> acts on ECL cells to release histamine
    • inhibitory action -> acts on D cells to inhibit secrtion of somatostatin
  • GRP
    • stimulating action -> acts on G cells to release gastrin


Describe the role of D cells in gastric secretion

D cells secrete somatostatin, which inhibits secretion of:

  • G cell gastrin
  • ECL cell histamine
  • Parietal cell HCl

D cells are acted upon by:

  • Stimulation - HCl from gastric parietal cells
  • Inhibition - ACh from the vagus nerve


Describe the role of G cells in gastric acid secretion

G cells release gastrin, which stimulates secretion of:

  • D cell somatostatin
  • ECL cell histamine
  • Parietal cell HCl

G cells are acted on by:

  • Stimulation - GRP from the vagus nerve
  • Inhibition - somatostatin from D cells


Describe the role of ECL cells in gastric acid secretion

ECL cells secrete histamine, which stimulates parietal cell HCl release

ECL cells are acted upon by:

  • Stimulation - ACh released from the vagus nerve
  • Inhibition - somatostatin released from D cells


Describe the role of parietal cells in gastric acid secretion

Parietal cells secrete HCl (gastric acid)

Parietal cells are acted upon by:

  • Stimulation - ACh from the vagus nerve
  • Stimulation - histamine from ECL cells
  • Stimulation - gastrin from G cells
  • Inhibition - somatostatin from D cells


What accounts for the observed drop in gastric [H+] after ingestion of food?

Approximately how long after ingestion of food does the rate of H+ secretion sharply increase?

Food buffers preexisting H+ in the stomach

H+ secretion rises sharply approximately 1 hours after food ingestion


Besides HCl, what else is secreted by gastric parietal cells? What is this important for?

Intrinsic Factor (IF)

IF is required for vitamin B12 absorption in the ileum


Where does fat digestion begin?

What is secreted in the stomach that aids with fat digestion? What type of cell secretes it?

The mouth - via lingual lipase released by the salivary glands

Gastric lipase - from chief cells

Note: only about 10% of fat digestion occurs due to lingual lipase. The vast majority of fat digestion occurs in the duodenum


What is pepsinogen?

What triggers its release?

What secretes it?

What activates it?

Enzyme released from gastric chief cells, responsible for protein digestion

Secretion induced by: ACH, gastrin, secretin, and cholecystokinin

Activated by HCl (or by pepsin)


Describe the composition of mucous

Mucins, phopholipids, electrolytes, and water


Appriximately how much chyme is released into the duodenum at a time?

a few milliliters


Describe the general regulation of stomach emptying

  • self-stimulation of stomach: gastrin and stretching of the stomach wall by food stimulates increased activity of the pylorus pump
  • inhibition from duodenum: inhibits stomach contractions and increases tone of the pyloric sphincter in response to distension, mucosal irritation, acidity and osmolality of the chyme


What part of the stomach contains ECL cells?

D cells?

G cells?

Corpus (body)