exam 2 class 16 Flashcards
Simply smelling, seeing, or even thinking about food: create long reflexes that begin in brain create a feedforward response known as the?
cephalic phase of digestion
complex hypoosmotic fluid, has water, ions, mucus, and proteins such as enzymes and immunoglobulins
Saliva:
Three pairs of salivary glands produce ~
1.5 liters of saliva/ day
Salivary glands are composed of?
exocrine glands, with
secretory epithelium arranged in
grapelike clusters of cells called acini
Saliva production is a two-step process:
(1) Acinar cells’ secreted fluid: an isotonic NaCl solution.
(2) Epithelial cells along duct reabsorb NaCl and secrete K+ and bicarbonate ion
Apical membranes of duct cells have very low water permeability called?
hypoosmotic saliva
functions of saliva
soften and moisten food
digestion of starch
taste
defense
lubricate food to make it easier to swallow
Soften and moisten food:
has salivary amylase. Amylase breaks starch
into maltose
Digestion of starch:
Saliva dissolves food so that we can taste it
Taste:
Lysozyme is an antibacterial salivary enzyme, and salivary immunoglobulins disable bacteria and viruses
Defense:
reflex action that pushes a bolus of food or
liquid into esophagus
swallowing, or deglutition:
swallowing center in medulla oblongata
glossopharyngeal nerve :
(1) Acinar cells’ secreted fluid:
an isotonic NaCl solution.
(2) Epithelial cells along duct reabsorb?
NaCl and secrete K+ and bicarbonate ion
separates lower end of the esophagus
separated from the stomach
Lower esophageal sphincter
one the most common digestive disorder
Gastroesophageal reflux disorder or GERD:
gastric acid and pepsin irritate lining of esophagus
heartburn:
During inspiration, when intrapleural pressure falls, what happens?
sub-atmospheric pressure in esophageal lumen and can suck acidic contents out of stomach if sphincter is relaxed
3 functions of the stomach
storage
digestion
defense
stores food and regulates its passage into the small intestine
Storage: in stomach
chemically and mechanically digests food into the soupy mixture called chyme
Digestion: in stomach
destroys bacteria and other pathogens that are swallowed with food
Defense: in stomach
before food arrives what reflex occurs
vagal reflex
distension of stomach and presence of peptides or amino acids in lumen activate endocrine cells and enteric neurons
gastric phase reflexes
influence motility and secretion
Hormones, neurotransmitters, and
paracrine molecules
When food arrives from the esophagus, the stomach relaxes and expands to hold the increased volume:
receptive relaxation
the lower stomach is where what occurs
digestion
Peristaltic waves pushes the food down toward the ________, mixing food with acid and digestive enzymes
pylorus
Lumen of stomach is lined with ?
mucus-producing
epithelium punctuated by
the openings of gastric pits.
The pits lead to gastric
glands deep within the
mucosal layer
first part of intestine
duodenum.
secrete hormone gastrin into the blood
G cells:
gastrin release is stimulated by presence of amino acids and peptides in the stomach/ by distension of stomach/ ENS neurotransmitter called gastrin-releasing peptide (GRP)
In short reflexes:
parasympathetic neurons from vagus nerve stimulate G cells to release gastrin into blood
in cephalic reflexes:
(1) directly acts on parietal cells
(2) indirectly by stimulating histamine release
Gastrin’s primary action is to promote acid release
secrete gastric acid (HCl) into the lumen of
the stomach
Parietal cells:
Acid secretion in the stomach
averages ?
1–3 liters per day,
(1) Causes release and activation of pepsin: enzyme that digests proteins.
(2) Triggers somatostatin release from D cells.
(3) Denatures proteins by breaking disulfide and hydrogen bonds that hold
the protein in its tertiary structure (more accessible to digestion by pepsin).
(4) Helps kill bacteria and other ingested microorganisms.
(5) Inactivates salivary amylase, stopping carbohydrate digestion that began
in mouth
Gastric acid has multiple functions:
H+ from water inside parietal cell is pumped
into stomach lumen by H+-K+-ATPase in
exchange for?
K+ entering cell
Cl- moves through?
open chloride channels
Net result is
secretion of HCl by cell
drugs to treat over secretion of gastric acid, block activity of H+-K+ ATPase
Proton pump inhibitors (PPIs):
what is absorbed into the blood in the parietal pathway of acid secretion in the stomach
HCO3-
The buffering action of makes blood leaving
the stomach less acidic, creating an ?
alkaline tide
Chief cells produce two enzymes:
pepsin and gastric lipase
inactive form- pepsinogen activated by H+ ( HCl from parietal cells) protein digestion
Pepsin:
break down triglycerides.
< 1/3rd of fat digestion takes place in
stomach
Gastric lipase:
secreted by ECL cells in
response to gastrin or acetylcholine
stimulation
Histamine:
protein secreted by
parietal cells, complexes with B12 vitamin
(for its absorption in the intestine).
Intrinsic factor:
also known as
hypothalamic growth hormone-inhibiting
hormone, is secreted by D cells
somatostatin (SS),
-physical barrier,
-chemical buffer
Mucus:
Bicarbonate:
- Zollinger-Ellison syndrome:
- Peptic ulcers:
Pathologies:
excessive gastrin (gastrinoma)
Zollinger-Ellison syndrome:
acid and pepsin destroy mucosa, creating holes that extend into submucosa and muscularis of stomach
Peptic ulcers:
Ibuprofen, aspirin
NSAIDS:
NSAIDs inhibit the enzyme
____________________, which is responsible for
converting AA into prostaglandins
cyclooxygenase (COX)
