Development, Gross Anatomy and Functional Histology of the Pancreas Flashcards
What are the structures of the digestive tract? (5)
Oral cavity
Esophagus
Stomach
Small and large intestine
Rectum and anus
What is the purpose of the associated glands?
Help with the digestion process
What are examples of the associated glands?
Salivary glands
Liver
Pancreas
What are the different types of salary glands found?
Submandibular
Parotid
Sublingual
What are the functions of the salivary glands?
They wet and lubricate
Initiate the digestion
Secrete germicidal protective substances
Synthesis of blood proteins
What are the functions of the liver?
Produces bile
Metabolism and inactivation
Synthesis of blood proteins
What are examples of blood proteins produced by the liver?
Albumin, transferin etc
What are the functions of the pancreas?
Produces digestive enzymes
Secretes hormones (endocrine function)
What is the function of the gallbladder?
Stores & concentrates bile
What is the boundary between the foregut and the midgut?
The opening of the small bile duct
Where does the pancreas develop from?
It is an outgrowth of endoderm near the distal end of the foregut
What influences the development of the pancreas?
The fibroblast growth factors from the cardiac mesoderm
Which structures of the pancreas are derived from the dorsal mesentery?
The dorsal pancreatic bud
Which structures of the pancreas are derived from the ventral mesentery?
Ventral pancreatic bud
Liver
Gallbladder
What does the ventral pancreatic bud end up becoming?
Uncinate process
What happens to the ventral pancreatic bud during the rotation?
During the rotation it will approach the dorsal pancreatic bud and eventually merge to form the pancreas
What happens to the dorsal pancreatic bud during the rotation?
Nothing, it remains fixed in place since it is attached to the dorsal mesentery
When does the mesoderm septum transversum thin out and why?
As the proliferating endoderm cells that will form the liver tissue extend into the septum transversum
What is the mesoderm of the septum transversum eventually reduced to?
Hepatic sinusoids and stroma
Capsule of the liver
Lesser omentum
The falciform, triangular and coronary ligaments
Where do the dorsal and ventral ducts merge together?
Near the opening of the common bile duct
Which structures form the main pancreatic duct?
The distal part of the dorsal pancreatic bud and the whole of the vernal pancreatic bud
What happens to the proximal part of the dorsal pancreatic bud?
It either disappears or it becomes the accessory pancreatic duct
Where does the accessory pancreatic duct drain?
Minor duodenal papilla
What happens if the proximal part of the dorsal pancreatic bud just disappears and does not develop into the accessory duct?
There are no consequences, the accessory pancreatic duct is just an alternative and extra part of the duct system.
What is the sphincter of Oddi and where is it found?
It is the smooth muscle around the major duodenal papilla
Which duct drains into the major duodenal papilla?
Common bile duct and main pancreatic duct
What kind of structure is the pancreas? (intraperitoneal, retroperitoneal or sub peritoneal)
Secondary retroperitoneal, because initially part of it was attached to the mesentery and then during the rotation it detached
What are the variation in union of bile and pancreatic ducts? Explain them
Short common channel, both of them join together through the same channel
No common channel, they enter as separate structures
Long common channel, the pancreatic duct attaches to the common bile duct and they then enter through the same channel
Which mesocolon structure is anterior to the pancreas?
Transverse mesocolon
What is an annular pancreas?
A rare condition in which the second part of the duodenum is surrounded by a ring of pancreatic tissue continuous with the head of the pancreas
How does an annular pancreas occur?
Part of the pancreas will rotate to one side, whilst the other part will rotate from the other side
What is the main complication of an annular pancreas?
The portion of the pancreas that has rotated in the wrong direction can constrict the duodenum and block or impair the flow of blood to the rest of the intestines
What are the different parts of the pancreas?
Head
Neck
Body
Tail
Where is the splenic artery located in regards to the parts of the pancreas? What is its characteristic feature?
The splenic artery is located above the head and it is identified by the spiral character of it
Where is the pancreas located?
Within the c-loop of the duodenum
What is the pancreas surrounded by?
Thin fibrous connective tissue
What does the connective tissue septa divide the pancreas into?
Lobules
Which structure is the tail of the pancreas attached to?
Attached to the hilum of the spleen
Which blood vessels form the portal vein?
The superior mesenteric and the splenic artery
Where is the portal vein located?
Behind the neck of the pancreas
What is the Uncinate process? How do you differentiate it?
It has the same functional cells as the rest of the pancreas; part of the pancreas. Derived from the ventral pancreatic bud.
The superior mesenteric trunk is anterior to it
Where is the superior mesentery trunk located?
Anterior to the 3rd part of the duodenum and Uncinate process
What ligament / pancreatic reflection may the tail of pancreas run along?
The splenorenal ligament, splenic artery also reaches the hilum from the same ligament
What are the blood vessels anteriorly and posteriorly to the uncinate process and the 3rd part of the duodenum?
Superior mesenteric vessels anteriorly
Aorta and portal vein posteriorly
Which artery is the pancreatic artery a branch of?
The splenic artery
Where are the anterior and posterior SUPERIOR pancreaticoduodenal arteries derived from?
Branches of the gastroduodenal
Where are the anterior and posterior INFERIOR pancreaticoduodenal arteries derived from?
Branches of the superior mesenteric artery
What are the veins of the pancreas like?
The veins correspond to the arteries and flow into the portal vein
Where is the lymph from the body and tail of the pancreas emptied?
The pancreaticosplenic lymph nodes which are located along the splenic artery, emptied via the lymphatic vessels
Where do the vessels of the head of the pancreas empty their lymph?
Pyloric lymph nodes
Where is the lymph then transported to?
Superior mesenteric lymph nodes and celiac lymph nodes
What are the components of the pancreas?
Exocrine and endocrine
What is the pancreas covered by?
A thin capsule of connective tissue
What do the connective tissue septa house and how is that significant?
It houses capillary networks, it is significant in tumor metastases
What are the structures involved in the exocrine component of the pancreas?
Serous acini
What is the difference between serous acini and mucous ones?
Mucous ones are found in the submucosa of the esophagus and the duodenum and their function is for protection.
Serous acini are used for secretion
What do serous acini secrete?
Water
Ions
Proteases
Amylase
Lipases
Phospholipase A2
Nucleases
What are the proteases secreted by the serous acini?
Chemotrepsinogen
Trepsinogen
What are chymotrypsinogen and trypsinogen converted into?
Chemotrepsin and trepsin
Why are chemotrepsin and trespsin not directly secreted but instead they have to be converted into?
It would lead to auto-digestion of the pancreas, in the case that there is activation of those enzymes in the pancreas and not the duodenum –> acute pancreatitis
What is the volume of daily secretions by the pancreas?
1.5 to 3.0L of daily alkaline secretions that neutralise the acid gastric chyme
Which hormones secreted by the enteroendocrine cells of the small intestine regulate pancreatic secretions?
CCK and Secretin
What is the function of CCK in regards to pancreatic secretion?
Stimulate acinar cells to secrete enzyme-rich fluid
What is the function of Secretin in regards to pancreatic secretions?
Stimulate centrocinar cells to secrete alkaline fluid rich in electrolytes and poor in enzyme activity
What are the characteristics of serous acini?
Round basal nuclei
Polarised
Apical zymogen granules
Where are centrocinar cells located, what do they secrete, and what are they connected by?
They are located close to the lumen, they secrete water and electrolytes and are connected by intercalated ducts
Why are intercalated ducts vital?
In order to reach the duodenum
How are zymogen granules secreted?
Through exocytosis
What are secretory acini made up of?
40 to 50 serous cells
What are acini surrounded by?
Basal lamina
What are acini supported by?
Sheath of reticular fibers that house blood capillaries
What is the pathway that exocrine hormones follow?
Serous acini
Centroacinar cells
Intercalated duct
Intralobular duct
Interlobular duct
What is the histology of intralobular ductule?
Squamous
What is the histology of interlobular duct?
CuboidalW
What is the histology of the main pancreatic duct?
Columnar
What are centrocinar cells like?
They are pale, simple squamous to ow cuboidal cells
What are centrocinar cells responsible for?
Secretion of bicarbonate-rich fluid
When do cells become columnar?
Just before reaching the main pancreatic duct
What are histological components of the endocrine part of the pancreas?
Islets of Langerhans
How many islets are there in the pancreas?
About 1 million of them
What is the function of Islets of Langerhans?
They secrete insulin, glucagon, and other minor hormones like somatostatin and pancreatic polypeptide
What volume of the liver do the Islets make up?
About 1 to 2%
What are islets of langerhans?
Spherical ovoid masses, 100 to 200μm in diameter
What are pancreatic islets made out of?
Rounded or polygonal cells
What are the cells of the islets like?
Smaller and more lightly stained than the acinar cells
What do routine stains or trichrome stains allow recognition of?
Acidophils (glucagon) and basophils (insulin)
Why do the vessels of the islets have fenestrations?
In order to take up hormones since there is no duct system
What is the structure of A cells like?
They have regular granules with a dense core surrounded by a clear region bounded by a membrane
What is the structure of B cells like?
They have irregular granules with a core formed of irregular crystals of insulin in a complex with zinc
What is the % quantity of A cells?
20%
Where are A cells usually found?
In the periphery
What is the hormone produced by A cells?
Glucagon
What is the hormonal function of A cells?
Acts on several tissues to make energy stored in glycogen and fat available through glycogenolysis and lipolysis; increased blood glucose content
What is the % quantity of B cells?
70%
Where are B cells found?
Central region
What hormone do the B cells produce?
Insulin
What is the hormonal function of B cells?
Acts on several tissues to cause entry of glucose into cells and promotes decrease of blood-glucose content
What is the % quantity of D cells?
< 5%
Where are D cells located?
Their position varies
What hormone do D cells produce?
Somatostatin
What is the hormonal function of D cells?
Inhibits release of other islet cell hormones through local paracrine action
What is % quantity of F cells?
Rare
What is the position of F cells?
Variable
What hormone do F cells produce?
Pancreatic polypeptide
What is the hormonal function of F cells?
Control of gastric secretion
Control of secretion of the exocrine pancreas
What is none-rotation of the midgut?
Occurs when the midgut rotates only 90o countreclockwise
What is the normal rotation of the midgut?
270o counterclockwise
What happens during the none-rotation of the midgut?
Caudal loop returns to abdomen first
What is the result of the none-rotation?
Large intestine on the left side (left-sided colon)
Small intestine on right side
What could none-rotation be complicated with?
Volovlus
What is the reversed rotation?
90o counterclockwise and 180o clockwise
What is the result of the reversed rotation?
Duodenum lies anterior to superior mesenteric artery
Transverse colon lies posteriorly to superior mesenteric artery
What is the complication of the reversed rotation?
Colon might be obstructed by the superior mesenteric artery
What is the mixed rotation and volvulus?
Failure to complete the final 90o
What causes the mixed rotation and volvulus?
Terminal part of the ileum returns to the abdomen first
What are the results of the mixed rotation and volvulus?
Cecum just inferior to pylorus
Cecum is fixed by bands of peritoneum
Mesentery of cecum pass by duodenum and may cause obstruction –> leads to strangulation
What is volvulus? What causes it?
Due to extreme mobility, the colon some times may rotate around its mesentery
What is the most common site of volvulus to occur?
The sigmoid colon
What is the prognosis of volvulus?
It may correct itself spontaneously or the rotation may centime until the blood supply to the gut is cut off completely
What is congenital omphalocele?
Intestines are covered with translucent amniotic membrane that covers the cord
What causes congenital omphalocele?
Failure of body walls to fuse at the umbilical ring
Due to defective growth of mesenchyme
Persistence of herniation of abdominal contents into umbilicus
What causes an umbilical hernia?
Intestines and part of greater omentum herniate through imperfectly closed umbilicus
What is an umbilical hernia?
Intestine covered by subcutaneous tissue and skin
When does the hernia protrude?
During crying, straining or coughing
What causes Gastroschisis?
Rupture in the anterior body wall, usually on the right hand side of the umbilical cord
What is Gatsroschisis?
The intestines are not covered and float freely in the amniotic fluid
What is the prognosis of Gastroschisis?
Good prognosis, it is not associated with any other conditions
What are the consequences of obstruction?
Distention proximal to the level of obstruction
General abdominal distention from obstruction to the abdominal parts of the bowel
Reduced stool output
What does forceful vomiting at the time of feeding indicate?
Upper obstruction
What could lead to an obstruction in the bowel?
Failure in the recanalization process
Vascular accident, embolus or thrombosis
What does less forceful vomiting with delayed onset suggest?
Obstruction of more distal segment
