Chapter 21: The Digestive System Flashcards
what are the folds in the small intestine called
Plicae
What are the folds in the stomach called
Rugae
What are the three layers of the inner lining of the gastrointestinal tract
mucosal epithelium, lamina propria, muscularis mucosae
Why is intestinal epithelium considered leaky
because some water and some solutes can be absorbed between the cells.
Where do nutrients enter the lymph and the blood
In the Lamina propria
What does absorption mean
movement of substances from lumen of GI tract to extracellular fluid.
What are the two meanings of the word secretion
- movement if water and ions from ECF to digestive tract lumen.
- The release of substances synthesized by GI epithelial cells into the lumen or the ECF
What three challenges does the digestive system face
- avoiding autodigestion: prevent the stomach from eating itself
- mass balance:
- defense: protection from foreign invaders
Are gastrointestinal cells polarized
yes
How are enzymes released
by exocytosis
What is a Zymogen
an inactivated enzyme
What are tonic contractions
sustained for minutes or hours. They occur in some smooth muscle sphincters and in the anterior portion of the stomach.
What are tonic contractions
sustained for minutes or hours. They occur in some smooth muscle sphincters and in the anterior portion of the stomach.
What are tonic contractions
sustained for minutes or hours. They occur in some smooth muscle sphincters and in the anterior portion of the stomach.
What are phasic contractions
lasting only a few seconds, in posterior region of stomach and small intestine
What are the interstitial cells of Cajal
act as an intermediary between neurons and smooth muscle. It functions as a pacemaker for slow wave activity in the GI tract
What are the interstitial cells of Cajal
act as an intermediary between neurons and smooth muscle. It functions as a pacemaker for slow wave activity in the GI tract
What happens when slow wave potential reach the threshold
voltage-gated Ca2+ channels in the muscle fiber open, CA2+ enters, and the cell fires one or more action potentials. Depolarization is due to the entry of Ca2+ into the cell. The entry also initiates muscle contracts
What happens if the duration of the slow wave is longer?
the more action potentials fire, the greater the concentration force in the muscle.
Contraction in the digestive system occur in 3 patterns. What are those patterns
- Migrating motor complex(sweeps food and bacteria into the large intestine)
- Peristalsis: moves bolus
- segmental contractions: short segments of the intestine alternately contract and relax. circular muscles contract while the longitudinal muscles relax.
What does the receptor GC-C used for, and what peptides activate it.
It is used to regulate fluid secretion in the intestine. It is activated by uroguaylin and guanylin
What is the difference between absorption and secretion
Absorption moves material from the GI luman into the ECF. Secretion moves substances from the cells or the ECF into the lumen
What are the 5 features the CNS shares with the ENS
- Intrinsic neurons
- neurotransmitters and neuromodulators
- Glial support cells
- Diffusion barrier
- integrating center
What are short reflexes
reflexes that originate within the enteric nerous system and are integrated there without outside input
What are long reflexes
digestive reflexes integrated into the CNS
What are the three families that gastric hormones divided into
Gastrin family, secretin family, gastric inhibitory pepside
What hormones are associated with the gastrin family
gastrin and CCK. Gastrin and CCk can bind to the same CCKB receptor
What hormones are associated with the secretin family
secretin, vasoactive intestinal peptide (VIP), a nonadrenergic-noncholonergic neurotransmitter, GIP, GLP-1
What do GIp and GLP-1 do
They work together to create a feed-forward signal for insulin release.
What does motilin do
increases in this secretion are associated with migrating motor complex
Where do anticipatory stimuli and stimulus of food activate neurons
In the medulla oblongata. It then sends a signal to the enteric nervous system. Secretion is then produced in anticipation of food.
Is saliva an exocrine or endocrine secretion
It is an exocrine secretion
How is saliva produced
It is secreted by the acini cells and then dumped into the ducts. This NaCL is isotonic and as it makes its way though the ducts, the NaCl is reaborbed while K and HCO3- is dumped into the lumen
How is the swallowing reflex activated
with the pressure of the bolus as the tongue pushes it against the soft pallet and the back of the mouth
What are the phases of digestion
the cephalic phase, the gastric phase, and the intestinal phase
What are the three functions of the stomach
It stores food and regulates its passage into the small intestine. The stomach chemically and mechanically digests food into chyme. It destroys bacteria that are swallowed
What starts the cephalic phase
the vagal reflex
What is receptive relaxation
When the stomach relaxes to hold increased volume. Helps the stomach regulate the amount of food entering it.
What does the lower stomach do during digestion
peristaltic waves push food towards the pyloric, mixing it with acid and digestive enzymes. Chyme is squirted into the duodenum.
What do G cells in the gastric glands do
They promote acid release bu acting on parietal cells and indirectly stimulating histamine release.
How is gastrin release stimulated
By the presence of amino acids and peptides in the stomach. Also triggered by neural reflexes 670
What is Gastrins role?
Gastric is released by G cells. Gastrin then activates parietal cells to create HCL. The accumulation of HCL activates the secretion of pepsinogen. Somoza ton is released in response to stop gastrin as a negative feedback response.
What are the functions of gastric acid
inactivates salivary amylase,kills bacteria, denatures protiens to make pepsin digestion more accessable, triggers D cells to release somatostatin, releases and activates pepsin
What is an alkaline tide
when the blood leaving the stomach is less acidic because of the buffer HCO3-
What is the function of PPI
They reduce the amount of acid in the stomach
Why does blood from the digestive tract go through the hepatic portal system first
It brings nutrients to the liver and picks up absorbed nutrients in the intestine.
Where does the most amount of digestion occur
The small intestine
How are protiens digested in the SI
How are carbs digested
How are lipids digested
How do the pancreas, gallbladder and the liver function
