Upper GI biochem Flashcards
What is saliva?
mixture of salivary gland secretions, microorganism products and soluble food products in the mouth
What are the main functions of saliva?
lubrication, digestion of food/enzymatic activity, growth factor prod. for epithelial cells, neutralizes bacterial acids, mediates taste sensations, defense again bacteria
What are the 3 major salivary glands?
parotid
submaxilary
sublingual
What are the 2 innervations of the salivary glands?
glossopharyngeal and facial nn.
What is contained the the primary secretion in the salivary glands?
ptyalin (alpha amylase)
mucus
extracellular fluid
lingual lipse
What ions are secreted into the saliva?
potassium & bicarb
What ions are absorbed from the saliva?
sodium and chloride
What does lysozyme do?
kills gram postive but not gram negative bacteria (cleaves beta 1,4 linkages of sugars in cell wall)
Function of peroxidase?
kills bacteria by producing reactive bromide and iodine
Function of lactoferrin?
binds iron and prevents bacterial and some fungal growth
Function of IgA?
recognizes and binds bacteria to induce immune reactions
Function of defensins?
antimicrobial polypeptides that form pore complexes on microbial cell membranes
Function of mucins?
modulate adhesion of baceria to oral tissues including teeth (antimicrobial), also lubricates
contains Oglycostylated specific glycoproteins
What does bicarb in the saliva do?
neutralizes bacterial produced acids (esp gram negative)
Which virusses are carried in the saliva?
herpes, HSV, EBV, mumps, rabies, HIV
How does CF causes xerostomia?
mutant chloride transports to plasma
How does Sjoegren’s syndrome cause xerostomia?
autoantibodies to salivary gland proteins
How much saliva is produced per day?
I liter
Where are endocrine like cells located in the gastric gland?
base
What are the 3 phases of gastric secretion?
cephalic-via vagus, PNS excites pepsin and acid prod.
gastric-local nervous secretory reflexes, vagal reflexes, gastrin-histamine stimulation
intestinal-nervous &hormonal mechanism
What two transmitters does the vagus nerve release? what is their effect?
ACh-stimulated secretion of parietal cell HCl and ECL histamine
Gastric releasing peptide-stimulated secretino of G cell gastrin
What do D cells secrete? what inhibits/stimulates its release? effect?
somatostatin-stimulated by HCl, inhibited by nerve cell ACh
-inhibits secretin of G celll gastrin, ECL histamine, parietal HCl
What do G cells secrete? What inhibits/stimulates its release? effect?
gastrin-stimulated by nerve cell GRP, inhibited by somatostatin
-stimulates secretion of D cell somatostatin, ECL histamine, Parietal cell HCl
What do ECL cells secrete? what inhibits/stimulates its release? effect?
Histamine-stimulated by nerve Ach, inhibited by D cell somatostatin
-stimulates scretion of parietal cell HCl
What do parietal cells secrete? what inhibits/stimulates this release? effect?
HCl-stimulated by nerve ACh, ECL cell histamine, G cell gastrin, inhibited by D cell somatostatin
Approximately how long after a meal does food buffer the pH of the stomach?
2hrs
Do oral cavity enzymes work in the stomach?
no, they are inactivated by the decrease in pH
What cell type secretes intrinsic factor?
parietal cells
What enzymes do fat digetion here?
lingual lipase
gastric lipase
What enzymes break down carbs here?
alpha amylase
What does protein digestion here?
pepsinogen (once converted to pepsin)
cleaves before hydrophobic AAs
What converts pepsinogen to pepsin?
HCl or Pepsin
What makes up gastric mucous?
mucins, phosphipids, electrolytes, water
What does gastric mucous do?
lube, protect (w/bicarb and mucins)
What are the key motor functions of the stomach?
storage
mixing and propulsion
emptying
What regulates stomach emptying?
in stomach-stretching stimulates myenteric reflex& gastrin stimulate pylorus pum
in duodenum-uses enteric nervous system, exrinsic & vagus nerves in parallel to inhibit stomach contractions and increase pyloric sphincter tone
Which endocrine cells are located in the body of hte stomach?
ECL
Which endocrine cells are located in the antrum of the stomach?
D & G cells
