Secretions of the small intestine, liver, gall bladder, and pancreas Flashcards
Where does the majority of chemical digestion and absorption of nutrients, electrolytes and water take place in the GIT?
- small intestines
What are ther 3 parts of the small intestines called from top to bottom?
1 - duodenum
2 - jejunum
3 - ileum
What is the name of the spincter that facilitates movement from the stomach into the duodenum
- pyloric sphincter
What are the 3 main secretions into the duodenum of the small intestines?
- intestinal juice (mucus/HCO3-)
- pancreatic juice (digestive enzymes)
- bile (fat emulsifier)
In addition to pancreatic juice, bile salts and intestinal juice, hormones can be secreted into the duodenum. What are the endocrine enzymes that are secreted that we need to know about?
- secretin
- cholecystokinin [CCK]
- glucose dependent insulinotrophic peptide [GIP]
The secretion of endrocrine secretions secretin, cholecystokinin [CCK] and glucose dependent insulinotrophic peptide [GIP] have an important functions in the duodenum. What 2 main secretions do they regulate in the duodenum?
- regulate bile and pancreatic secretions
Secretin is secreted by endocrine cells in the small intestines, which cells in the duodenum secrete it and what is the role of this hormone?
- peptide hormone secreted by S cells in duodenum
- regulates water homeostasis and pH
- regulates pH by secretions in the stomach, pancreas, and liver
Is secretin secreted into the lumen of the small intestines or into the blood stream?
- can be both
What is cholecystokinin and what is its main function?
- a peptide hormone
- secreted by enteroendocrine cells of te duodenum
- stimulates digestive enzymes and bile to be released
- can also act as a hunger supressant
What cells secrete glucose dependent insulinotrophic peptide (GIP) and what is the function for GIP?
- K cells in duodenum (hormone)
- trophic means to secrete and insulin tells you what
- inhibits gastric acid secretion
Cells at the tip of the microvilli are called enterocytes, what are they primarily involved in?
- absorption
What are goblet cells?
- cells in small intestines that secrete mucous
What are enteroendocrine cells?
- specialized cells found within the GIT stomach and pancreas
- able to secrete hormones when stimulated
Enteroendocrine cells are able to secrete hormones. They can secrete locally or systematicall, how do they do this and what are the different effects?
- local secretion = local messenger
- blood secretion = systemic effects
What are paneth cells that can be found in the epithelium of the small intestines?
- highly specialized secretory epithelial cells
- produce dense granules containing antimicrobial peptides and immunomodulating proteins
- main role immunotherpay
What are Brunners glands and where is the only place they can be found?
- glands are located in the submucosa of the duodenum
Brunners glands can only be found in the duodenum, what is their purpoose?
- secrete HCO3- and mucus
- increase pH and protect mucus
What cell in the walls of the GIT differentiate into different epithelial cells and drive shedding of epithelail cells?
- stem cells
Epithelial cells of the GIT have a high turnover, how often do they generally shed?
- 3-6 days
As the epithelial cells have a high regenerative capacity, what are they susceptible to in relation to a specific type of treatment?
- cancer treatment
- X-rays
- chemotherapy
Do paneth cells come from stem cells?
- no
- they come from daughter cells
- migrate downwards instead of upwards
What is intestinal juice, and what is it made up of?
- solution that facilitates digestion in the small intestines
- enterocytes secrete water containing electrolytes
- paneth cells secrete lysozyme to degrade bacteria
- goblet cells secrete mucus
- brunners glands secrete alkaline mucus
What is the main role of bile in the small intestines?
- fat emulsification
What is pancreatic juice?
- composed of digestive enzymes and bicarbonate
- eznymes are screted by acinar cells in pancrease
- bicarbonate is secreted from the epithelial cells lining small pancreatic ducts
The pancreas is classed as both exocrine and endocrine, why is this?
- exocrine = digestive enzymes
- endocrine = insulin and glucagon
Typically, what is the pH of the pancreatic juice secreted by the pancreas?
- pH 8
- crucial for neutrilising the acid contents from the stomach
Which large nerve provides parasympathetic control in stiumlating the pancreas?
- vagal nerve (cranial nerve X or 10)
In addition to neural innervation of the pancreas, there is hormonal control, which 3 hormones influence pancreatic secretions?
1 - cholecystokinin
2 - secretin
3 - gastrin
The pancreas is composed of exocrine and endocrine epithelial clusters. What are the 2 types of clusters, and which makes up the majority of these clusters?
- acinar clusters (exocrine) and islets of langerhans (endocrine)
- 99% are acinar clusters
- secrete pancreatic juice (water, electrolytes, sodium bicarbonate and pro-enzymes)
The pancreas is composed of glandular epithelial clusters. What makes up a small but very important proportion of these clusters?
- 1%- endocrine pancreatic islets (Islets of Langerhans)
The pancreas is composed of glandular epithelial clusters. 1% of these clusters are endocrine clusters, of which there are 4 types, what are they?
1 - alpha cells (glucagon)
2 - beta cells (insulin)
3 - delta cells (somatostatin)
4 - F cells (pancreatic polypeptide)
What does acinar relate to?
- berry
- group of cells resembling a berry