Physiology - gastrointestinal tract A Flashcards
What us the role of Gastrin?
Stimulate gastric acid secretion and growth of gastric mucosa
Where is gastrin produce and what triggers the production?
In G cells of stomach in responce to ingestion of food and protein
What is the role of Cholecystokinin CCK
Contract gallbladder and inhibit stomach contractions
Where is CCK produce and when?
Duodenum and jejunum in response to fat, fatty acids and monoglycerides
What is the role of secretin?
Promotes pancreatic secreation of bicarbonate to neutralize acid in small intestine
Where is secretin secreated from and when?
By S cells in mucosa of duodenum in response to acidic gastric juice
What is the role of Gastric inhibitory peptide (GIP)?
Reduce motor activity of stomach (also stimulate insulin secretion)
Where is GIP secreted and in response to what?
By mucosa of the upper small intestine in response to fatty acids, amino acids and to some extent carbohydrates
Where are digestive enzymes secreted?
From most areas of alimentary tract
What is the role of mucus in alimentary tract?
Lubrication and protection
What affect the type of enzyme and the quantity?
The amount of food and the composition
Where are single-cell mucus glands located?
On surface of epithelium in most part of gastrointestinal tract. Called mucous glands
What do single-cell musuc glads do?
Excrude mucus directly onto epithelium surface to act as a lubricant. Responds to local irritation.
What do gastric pits do?
Small pores called gastric pits contain many exocrine cells that secrete digestive enzymes and hydrochloric acid into the lumen, or hollow region, of the stomach.
Invaginations of the epithelium into submucosa
Where are the tubular glands?
In the stomach and upper part duodenum
What are glands?
a collection of cells or an organ responsible for secretions and excretions
What makes the shape of tubular glands?
cells of a consistant shape that form a uniform tubular lumen
What is secreted from tubular glands?
Acid and pepsinogens
What are some roles of salivary glands, pancreas and liver?
Provide secretion for digestion and emulsification of food
What stimulate the production of mucus ?
When food touch the surface
Connection between gastric pits and gastric glands?
The glands themselves are in the lamina propria of the mucous membrane and they open into the bases of the gastric pits formed by the epithelium
How is the enteric nervous system stimulated by local epithelial stimulation?
- Tactile stimulation
- Chemical irritation
- Distention of the gut wall
Where are the glands most affected by parasympathic nervs?
upper portion of the tract (salivary glands, esophageal glands, gastric glands and pancreas)
How does parasympathic nerves stimulate alimentary tract?
Increases rate of alimentary glandular secretion
How does sympathic nerves stimulate alimentary glands?
Cause slight to moderate increase by some of the local glands - short
But at the same time also shrink the blood vessle flow so long term it reduces the production of the glands
What happens if there is a copious secretion by the glands as a response to parasympathic or horminal stimulation?
Superimposed sympathic stimulation usually reduces secretion
Where are hormones liberated and when?
From the gastrointestinal mucusa in response of food in lumen
Where are the hormones absorbed ?
Absorbed into blood and carries to glands where they stimulate secretion
When is it important to increase the output of gastric juice and pancreatic juice
when food enters the stomach or duodenum
What is mucus?
Water, electrolytes, and a mixture of several glycoproteins that are composed of large polysaccharides bound with much smaller quantities of protein
What does mucus inhibit/provide?
the ability to allow easy slippage of food along the gastrointestinal tract and to prevent excoriative or chemical damage to the epithelium
What is beneficial about glycoproteins of mucus?
have amphoteric properties, which means that they are capable of buffering small amounts of either acids or alkalies
How does mucus neutralize acids?
Often contains moderate quantities of bicarbonate ions, which specifically neutralize acids.
What’s beneficial about adherant quality of mucus?
make it adhere tightly to the food or other particles and to spread as a thin film over the surfaces.
Also causes fecal particles to adhere to one another to form the feces
Saliva contains two major types of protein secretion, which?
- ptyalian (an alpha-amylase) which is an enzyme digesting starches
2- mucus secretion that containes mucin for lubrication and for surface protective purposes