Extra Mural Digestive System Flashcards
What do the associated glands of the extra mural system consist of? ( 4 glands)
Salivary glands
Pancreas
Liver
Gallbladder
Provide a description of salivary glands. What do they produce, wha the the three major pairs of glands?
These are a type of exocrine gland. Salivary glands produce saliva, a digestive and lubricating/protective function.
Three major pairs:
-parotid
-submandibular (submaxillary)
Sublingual
With regards to salivary glands, what are septas?
Septa is a type of CT that divides the parenchyma into lobules. CT surrounds each gland.
With regards to salivary glands, what is acini?
Acini are the arraignment of parenchyma within each gland, these are secretory units
With regards to salivary glands, what are acinus’?
These are a blind sac (spherical unit) composed of secretory cells
What are the three types of acini? (Don’t describe)
Serous Acini
Mucous acini
Mixed acini
Provide a description of Serous Acini
These contain only serous cells (secrete protein)
The cells are pyramidal in shape, round nasal nucleus
Describe mucous acini
This contains only mucous cells
The cells are in pyramidal shape, somewhat columnar in shape
These are also have apical granules which contain mucins (lubricating properties)
Describe mixed acini
This contains both serous and mucous cells
These have caps of serous cells called serous demilunes
What are the three sequential enlargement segments of ducts systems within glands?
Intercalated ducts
- leads from the acinus
- lined by low cuboidal epithelium
Striated ducts (intralobular)
- lined by simple columnar epithelium
- modifies electrolytes components of saliva
Excretory ducts
- large ducts that empty into oral cavity
- epithelium begins as simple columnar but. transitions to stratified cuboidal or columnar
What are myoepithelial cells?
These are small flattened contractile cells that lie between the basal plasma membrane of the epithelium cells of the acini and the basal lamina
These extend contractile processes around the acini and duct
What are parotid glands? Where are they located and what do they contain and produce?
Location:
- below and in front of ear
Contents:
- only serous acini
Production:
- abundant Alpha amylase
What is alpha amylase?
This initiates hydrolysis of CHO, and proline rich proteins with antimicrobial and other protective properties
What are submandibular glands? Where are they located and what do they contain and produce?
Location:
- under either side of the floor of mouth close to the mandible
Contents:
- this has a mixed gland, serous acid intermixed with many mucous acini with serious caps (CALLED SEROUS DEMILUNES)
Production:
- produces lysozyme
What is lysozyme?
This is secreted visa submandibular glands and helps with the hydrolysis of bacterial walls
What are sublingual glands? Where are they located and what do they contain and produce?
Location:
-floor of the mouth anterior to submandibular gland
Contents:
- mixed glands, mostly mucous acini, the main product is mucus
Production:
- produces mucus, adds both alpha amylase and lysozyme
What is the pancreas? What are the components of it, what are its two functions?
The pancreas is an elongated glad grossly divided into three components/regions:
Head—> expanded portion lies in C shaped curve of duodenum
Body—> narrow portion in centre
Tail—> extends to the left towards hilum of spleen
Functions as:
Exocrine
Endocrine
Describe exocrine function of the pancreas
This is when the pancreas synthesizes and secretes digestive enzymes into duodenum, it takes up most of the parenchymal tissue space
Describe the endocrine function of the pancreas
This is when the pancreas synthesizes and secrete insulin and glucagon into blood.
What is a distinct cell cluster that the pancreas secretes via endocrine?
Islets of langerhan. These are randomly dispersed among the exocrine pancreas tissue
With regards to the exocrine portion of the pancreas, what are their secretory units?
The units are serous acini formed by simple epithelium of pyramidal shaped cells
With regards to the exocrine portion of the pancreas, what are zymogen granules?
These are the round nucleated secretory base of the cell
With regards to the exocrine portion of the pancreas, how does the initial intercalated ducts begin?
These begin within the acinus as well as centroacinar cells
With regards to the exocrine portion of the pancreas, what is the purpose of intercalated ducks and centroaciner cells?
These secrete bicarbonate to neutralize acidic chyme entering the duodenum from the stomach. Optimizing the pH for enzyme activity
What are the three types of pancreatic digestive enzymes that are found in zymogen granules of acinus cells?
Proteases: trypsinogen, chymotrypsinogen (these are digestive proteins)
Amylase (alpha amylase): these digest carbohydrates
Lipase: these digest lipids
How is pancreatic exocrine secretion regulated?
This is regulated via hormonal control. Mainly by two hormones (secretin and cholecystokinin) secreted by enteroendocrine cells of the small intestines
What is the purpose of of secretin within the pancreatic exocrine glads?
This promotes water and bicarbonate, the secretion buy the pancreatic ducts epithelial cells
What is the purpose of cholecystokinin (CKK) within the pancreatic exocrine glands?
These stimulate enzyme secrete by the pancreatic acinar cells
What is the overall purpose of the endocrine pancreas?
Regulate blood glucose
What are the five components of the endocrine pancreas?
Islets of langerhans A cells B cells D cells PP cells
With regards to the endocrine pancreas, what are islets of langerhan?
These are scattered throughout the pancreas and secrete hormones that regulate blood glucose levels and have a rich network of fenstrated capillaries
With regards to the endocrine pancreas, what are A cells?
These secrete glucagon, they stimulate the release of glucose into the blood (15020% of islets)
With regards to the endocrine pancreas, what are B cells?
These secrete insulin, they stimulate the uptake of glucose from the blood ( 70% located centrally)
With regards to the endocrine pancreas, what are D cells?
These secrete somatostatin, they inhibit insulin and glucagon secrete (5-10% of islet cells)
With regards to the endocrine pancreas, what are PP cells?
These secrete pancreatic polypeptides that stimulate gastric chief cells and inhibit boiler and exocrine pancreatic secretion
What is the overall structure of the liver? What is it covered in?
This is the largest internal organ, covered by a connective tissue capsule and extends septa (trabeculae) of CT that divides parachyma into lobules
Explain the capsule and hilum of the liver. What entres and what exits? Where does this occur?
The ports hepatis is located on the inferior side of the liver.
The liver contains a duel blood supply:
Hepatic portal veins, hepatic artery ENTRE
Hepatic veins, lymphatics, and common bile duct EXIT
Where is the major blood supply located within the liver? How mach?
Major supply from the hepatic portal vein (75%) the hepatic artery is 25%
What is the main parenchymal cell within the liver? What type of cell is it?
The hepatocyte! This is an epithelial cells with apical microvilli
How is liver parenchyma organized?
Thousands of hepatic lobes in which hepatocytes form hundreds of plates surrounding a central vein
The classic hepatic lobule contains a portal triad. Name the three components of this triad.
- Branch of bile duct
- Branch of hepatic portal vein
- branch of hepatic artery
With regards to the portal triad of the liver, describe the branch of the bile duct, what does it contain?
This is lined with cubodial epithelium, it is part of the bile conducting system
With regards to the portal triad of the liver, describe the branch of hepatic arteries
This supplies less blood but the most O2
With regards to the portal triad of the liver, describe the branch of the hepatic portal vein
This is rich in nutrients, low in O2
With regards to the portal triad of the liver, what is the space of Mall?
This is a periportal space around the portal triad where lymph originates in the liver
With regards to the portal triad of the liver, what are sinusoids?
These are discontinuous and fenestrated capillaries where arterial and venous blood mix
Where does blood exit within the hepatic lobule?
It will exit or leave at the central vein
How are physiological functions of the liver performed?
Via hepatocytes
What are some physiological functions of the liver?
- produce bile (exocrine release into bile caniculi)
- produce plasma proteins
- releases coagualtion proteins and transferrin (endocrine releases into sinusoids)
- stores glucose
- stores vitamin A D and K
- modifies thyroxine (T4)
What is the Billary Tree (in simple terms, its location)
Bile canaliculli—>canals of hering—> bile ductles
What do hepatocytes produce?
These produce bile, a fluid for excretion of bilirubin
What is bilirubin?
This is a byproduct of hemoglobin (RBC) breakdown
What is an important role in bile with regards to absorption?
Bile is involved in the absorption of fats in the gut
What do apical hepatocytes form?
Bile canaliculi, exocrine secretion of bile from the hepatocytes initially enter these structures
What do bile canaliculi empty into?
These empty into the canals of hering, these are composed of epithelial cells called cholangiocytes
What do canals of hering merge into?
These merge into the bile ductules
The sinusoids of the hepatocytes have 3 structures/cells associated with them. Name them
Space of disse
Kupffer cells
Hepatic stellate cells (Ito cells)
With regards to the sinusoids, what are the space of disse?
These are spaces that lie between surface of hepatocytes. These are the site of exchange of material between the blood and liver cells
With regards to the sinusoids, what are Kupffer cells?
These are macrophages found within the sinusoidal lining. The APCs remove bacteria and debris
With regards to the sinusoids, what are the hepatic stellate cells?
These store vitamin A and other fat soluble vitamins can synthesize ECM
What are the three structures of the hepatic lobule?
- Classic hepatic lobule
- Portal lobule
- Hepatic acinus
With regards to the structure of the hepatic lobule, explain what the classic hepatic lobule is
This is when blood flows past hepatocytes from portal areas to central veins. There is an emphasis on endocrine function
With regards to the structure of the hepatic lobule, explain what the portal lobule is
This emphasizes the biliary tree with bile flow moving opposite of blood flow
With regards to the structure of the hepatic lobule, explain what the hepatic acinus is and its three zones
This emphasizes blood flow and oxygen gradients from hepatic artery to central veins
Zone 1—> hepatocyte closest to hepatic artery (most O2 and nutrients)
Zone 2 —> intermediate
Zone 3—> hepatocyte closest to central vein (least O2 and nutrients, most prone to ischemic injury)
What is the overall structure and function of the gallbladder? Wha are some important aspects to it?
Structure:
- hollow pear shaped sac
- mucosa lined with simple columnar and apical microvilli (increasing SA)
- no true submucosal layer
Function:
-concentrates and stores pile
Has rokitantsky aschoff sinuses (RA sinus) which are deep diverticula of mucosa
What happens in the gallbladder when the muscularis externa contracts?
The contraction itself is induced by cholecystokinin (CCK) which sends bile to the duodenum where it emulsifies fat
