Lecture 9 - Pancreas and the small intestine Flashcards
The pancreas: what is it, what is it located between, and what are its relations?
Exocrine and endocrine organ
Lies between the duodenum and spleen
Relations of the pancreas:
* Retroperitoneal
* Located in the epigastrium and left hypochondrium
* Lies transversely across the posterior abdominal wall
* Is posterior to the stomach
The pancreas: the regions
Tail - leftmost part, near the spleen
Body - between tail and neck
Neck - right next to aorta and IVC
Head - touching the duodenum
Uncinate process - bottom part of the pancreas, where the blood connects
Pancreatic exocrine functions
Tubuloacinar glands containing pyramid-shaped acinar cells that secrete digestive enzymes as pancreatic juice which is secreted into the duodenum via intralobular and then pancreatic ducts
Pancreatic ducts
Main pancreatic duct:
* Accessory pancreatic duct - minor duodenal papilla
* Hepatopancreatic ampulla - Major dupodenal papilla
Sphincters - sphincters are found at the beginning of the MDP and the HA/BD joining to the MDP
Pancreatic endocrine functions
Contain Islets of Langerhans which secrete:
* Glucagon into the blood - using α cells
* Insulin into the blood - using β cells
* Somatostatin into the blood - using δ cells
* cholecystokinin
* and secretin
Glucagon: what does it do and what secretes it?
Promotes the conversion of glycogen into glucose to raise blood glucose levels
α cells in the Islets of Langerhans
Insulin: what does it do and what secretes it?
Promotes the conversion of glucose into glycogen to lower blood glucose levels
β cells in the Islets of Langerhans
Insulin: what does it do and what secretes it?
Also known as the growth hormone inhibiting hormone, inhibits the release of other pancreatic hormones
δ cells in the Islets of Langerhans
Cholecystokinin: what does it do and what secretes it?
Stimulates the secretion of digestive enzyme
I-cells of the upper small intestine in response to fat, protein, and some nonnutrients
Secretin: what does it do and what secretes it?
Stimulates the secretion of bicarbonate-rich pancreatic fluid
S cells in the duodenum
Pancreatic blood supply: how are the neck, body, and tail supplied, how is the head supplied, how is the uncinate process supplied, and what anastomosis occurs?
Coeliac trunk, splenic artery - subdivides into the greater pancreatic artery: supplies the neck, body, and tail of the pancreas
Coeliac trunk, gastroduodenal artery - subdivides into the anterior/posterior superior pancreaticoduodenal artery which supplies the head of the pancreas
Superior mesenteric artery - branches into the anterior/posterior inferior pancreaticoduodenal arteries which supply the uncinate process
Superior mesenteric artery and coeliac artery anastomose through the connection between the anterior/posterior inferior pancreaticoduodenal and anterior/posterior superior pancreaticoduodenal arteries
Pancreatic venous drainage: how are the neck, body, and tail drained, how is the head drained, how is the uncinate process drained, and what is the final drainage?
Pancreatic veins take blood from the neck, body, and tail, and drain into the splenic vein
The superior pancreaticoduodenal vein takes blood from the head and drains blood into the superior mesenteric vein
The inferior pancreaticoduodenal vein takes blood from the uncinate process and drains blood into the superior mesenteric vein
The IMV drains into the splenic vein and drains into the hepatic portal vein, the SMV also drains into the hepatic portal vein
Pancreatic innervation
Sympathetic:
* Abdominopelvic splanchnic nerves
* sympathetic chain
Parasympathetic:
* Vagus nerve
Plexuses:
* Coeliac plexus
* Superior mesenteric plexus
Pancreas: lymphatic drainage
Pancreaticosplenic nodes or pyloric nodes → superior mesenteric nodes or coeliac nodes → Chysterna chyli and thoracic duct
The duodenum: peritoneum, location
Mostly retroperitoneal but contains intraperitoneal parts in the superior part
The descending part in the foregut and the horizontal and ascending parts in the midgut
Duodenum blood supply
Coeliac trunk, gastroduodenal artery - subdivides into the anterior/posterior superior pancreaticoduodenal artery which supplies the superior parts of the duodenum
Superior mesenteric artery - branches into the anterior/posterior inferior pancreaticoduodenal arteries which supply the duodenum
Superior mesenteric artery and coeliac artery anastomose through the connection between the anterior/posterior inferior pancreaticoduodenal and anterior/posterior superior pancreaticoduodenal arteries
Duodenum venous drainage
The superior pancreaticoduodenal vein takes blood from the duodenum and drains blood into the superior mesenteric vein
The inferior pancreaticoduodenal vein takes blood from the duodenum and drains blood into the superior mesenteric vein
SMV drains into the hepatic vein - liver filtration occurs
Duodenum histology: what are the cells, and what is special with the mucosa and the submucosa?
Simple columnar epithelium with goblet cells - produce mucus, trap bacteria, and have a lubricating factor
Mucosa layer - contains villi/microvilli (increase SA:V)
Submucosa - contains Brunner’s glands (secrete a thin, watery, alkaline mucus to counteract the acids entering the duodenum)
11.19/ 19/30
29:30
Jejunum and Ileum
Mesenteries: what are they and what examples of free mesenteries are there?
A double fold of peritoneum that attaches part of the intestines to the posterior abdominal wall
- Mesoappendix
- The mesentery
- Transverse mesocolon
- Sigmoid mesocolon
The mesentery: what does it do and where is it found?
The root of the mesentery allows entry and exit
of blood and lymph vessels, and nerves
?? watch leccy/google
Jejunum and ileum blood supply
Arterial supply:
Superior mesenteric artery -> jejunal arteries, arterial arcades, ileal arteries, vasa recta, Ileocolic arteries, ileal branch
Venous drainage:
jejunal veins, venous arcades, ileal veins, vasa recta (??), Ileocolic veins, ileal branch(???) (???) -> superior mesenteric vein -> portal system
??? innervation
Parasympathetic:
* posterior vagal trunks
Sympathetic:
* T8 to T10 then abdominopelvic splanchnic nerves then superior mesenteric ganglion
Visceral afferent:
* T8 to T10
11.24
Jejunum histology
- Simple columnar epithelium with goblet cells
- Plicae circulares
- Each villus has a core of lamina propria
- Few Peyer’s patches
Ileum histology
11.26
- Many Peyer’s patches
- Villi/Mucosa as the outer layer
- Peyer’s patches below the surface
- Plica circulares - stick-shaped projections that the outer layer covers
- Muscularis mucosa - separates the mucosa and submucosa/plica circulares
- Submocsa - layer underneath the muscularis mucosa
- Circular muscle
- Longitudinal muscle
Villus: what are they, what do they do, how are they supplied/innervated, and what other key features are they involved with?
Projections within the GI tract composed of simple columnar epithelium
Used in food absorption, carries nutrients into the hepatic portal circulation
Lamina propria - contains an extensive capillary network
- Lacteals - transport lipids into the lymphatic system
- Microvilli - cover villi surfaces to increase SA:V for absorption
Lymphatic drainage
- Ileocolic lymph nodes (ileum/lower LI (?))
- Juxta-intestinal lymph nodes (J/L?) -> mesenteric lymph nodes (J)
- ILN/MLN -> superior central lymph nodes (?) -> superior mesenteric lymph nodes -> intestinal lymphatic trunk -> coeliac trunk
Check this is right tho
