Flashcards in Lecture 16: GI Secretory Functions, Digestion, and Absorption Deck (142)
What are the 4 different types of glands in the GI system?
- Unicellular mucous
- Crypts of Lieberkuhn
- Tubular glands
- Complex glands
List 3 examples of where complex glands are found in the body.
- Salivary glands
List the 4 different mechanisms that stimulate glands in the GI system.
- Food contact and local epithelial stimulation.
- Autonomic stimulation (mostly parasympathetic).
- Higher brain centers.
- Hormonal stimulation.
What are the functions of secreted mucous?
> Adheres to food and other particles.
> Spreads thin film over surfaces.
> Coats wall of gut, preventing actual contact of food.
> Causes fecal particles to adhere to one another.
> Resistant to digestion by GI enzymes.
> Has amphoteric properties making it useful for buffering small amounts of acids and bases.
What are the functions of saliva?
> Initial starch digestion (alpha-amylase) and initial triglyceride digestion (lingual lipase).
> Lubrication of food and protection of mouth and esophagus.
Which enzyme starts initial starch digestion in the mouth?
Which enzyme is responsible for initial triglyceride digestion in the mouth?
What is the composition of saliva?
> High potassium ion and bicarbonate concentrations.
> Low sodium and chloride ion concentrations.
> Presence of alpha-amylase, lingual lipase, and kallikrein.
What are the characteristics of saliva that has the lowest flow rate?
- Lowest osmolarity.
- Lowest sodium, chloride, and bicarbonate ion concentrations.
- Highest potassium ion concentration.
Does saliva composition of a high or low flow rate have a higher potassium concentrations?
Lowest flow rate saliva has the highest potassium ion concentration.
Is the saliva secretions of the parotid gland mixed or serous?
Almost entirely serous.
Is the saliva secretions of the submandibular and sublingual glands serous or mixed?
Where does the first stage of salivary secretion of ions occur?
What enzyme does the first stage of salivary secretion of ions contain?
Is the composition of the first stage of salivary secretion of ions isotonic, hypotonic, or hypertonic?
Isotonic, with ionic concentration similar to plasma.
Where does the second stage of salivary secretion of ions occur?
In the second stage of salivary secretion of ions, what happens to sodium ions?
During the second stage of salivary secretion of ions, are potassium ions actively secreted r reabsorbed?
Active secretion of potassium ions.
During the second stage of salivary secretion of ions, are bicarbonate ions secreted or reabsorbed?
Active/Passive secretion of bicarbonate ions.
During the second stage of salivary secretion of ions, are chloride ions secreted or reabsorbed?
Passive reabsorption of chloride ions due to -70 mV in ducts.
What is saliva production controlled by?
Mostly parasympathetic system, but also by sympathetic system - BOTH result in increase in saliva production.
True or False:
Both the parasympathetic and sympathetic system result in the increase of saliva production.
Which cranial nerves are involved in the regulation of salivary secretion?
CN 7 and 9
Which type of receptor, found on both the acini and ducts, signal parasympathetic function in the regulation of salivary secretion?
muscarinic cholinergic receptor
What is the second messenger in parasympathetic activation in the regulation of salivary secretion?
> inositol 1,4,5-triphosphate (IP3)
> increased [Ca2+]
Which receptor is involved in the sympathetic signaling in the regulation of salivary secretion?
What is the second messenger in sympathetic activation in the regulation of salivary secretion?
List factors that increase saliva production.
- food in mouth (via parasympathetic activation)
- conditioned reflexes
You know that food in the mouth increases saliva production, but is this regulated by parasympathetic or sympathetic activation?