D.2 Digestion Flashcards
(120 cards)
Diagram of digestive system
What kind of mechanisms control the secretion of digestive juices?
-Mechanical
-Nervous
-Hormonals
What actions can trigger the secretion of saliva and gastric juice?
-Not only will the presence or smell of food stimulate the digestive system, but also thinking about it will make your body secrete saliva and gastric juice.
-This would prepare the body for the future intake of food.
The nervous control is mainly provided by the ___
Autonomic nervous system.
What is the autonomic nervous system divided into?
The sympathetic and parasympathetic systems.
What does the sympathetic system control?
Processes involved in responses to danger
What does the parasympathetic system control?
Homeostasis and processes related to rest and digestion.
What are the functions of the parasympathetic and sympathetic systems in digestion?
The parasympathetic system speeds up digestion when food is ingested, while the sympathetic slows it down when there is no food available.
Diagram showing the control of the digestive processes
What does having food in your mouth and gut induce?
The presence of food in your moth will induce the secretion of saliva and the presence of food in the gut will induce the secretion of gastric juice (especially after eating proteins), intestinal juice, pancreatic juice and bile (especially if you have eaten fats).
What are the hormones involved in the chemical control of digestion?
-Gastrin
-Secretin
-Cholecystokinin (CCK)
How are the hormones involved in the chemical control of digestion secreted and how do they travel?
They are secreted in the digestive system and travel through the blood to the target organs.
How is gastrin produced?
It is produced by special cells (called G cells) in the stomach, duodenum, and pancreas, in response to physical stimulation due to the presence of food, as well as to chemical stimulation by protein
What is stimulated when gastrin is released?
When gastrin is released, it stimulates the production of gastric juice by the parietal cells in the gastric glands.
What is gastric juice made up of?
A mixture of water, hydrochloric acid, and other inorganic ions, enzymes (pepsin, rennin), mucus, various polypeptides, and intrinsic factor.
What is intrinsic factor necessary for?
For absorbing vitamin B12.
What is the effect of gastric juice on the food content?
It changes the pH of the food content from 6.7 to 2, providing acidic conditions that will enhance digestion.
What will happen when there is sufficient gastric juice present (around 1 to 1.5 liters)?
The production of gastrin will stop and therefore so will the secretion of gastric juice.
Hormonal control of digestion
- Gastrin is secreted into the bloodstream from the gastric pits of the stomach and stimulates the release of stomach acids
- If stomach pH drops too low (becomes too acidic), gastrin secretion is inhibited by gut hormones (secretin and somatostatin)
- When digested food (chyme) passes into the small intestine, the duodenum also releases digestive hormones:
- Secretin and cholecystokinin (CCK) stimulate the pancreas and liver to release digestive juices
- Pancreatic juices contain bicarbonate ions which neutralize stomach acids, while the liver produces bile to emulsify fats
Give an example of an inhibitory hormone
Somatostatin
How is acid secretion regulated?
-By the nervous system, which causes direct stimulation of the parietal cells to secrete acid, and indirect stimulation by decreasing somatostatin secretion.
-In addition, a regulatory feedback mechanism exists whereby the presence of acid in the lumen of the stomach stimulates somatostatin secretion, which in turn slows down acid secretion.
What are exocrine glands?
They are glands that have ducts that carry their secretory product to the surface of the body or the lumen of the gut.
Give examples of exocrine glands
The sweat, sebaceous, and mammary glands and the glands that secrete digestive enzymes.
Diagram showing the development of an exocrine gland