Normal Anatomy (Pancreas & Liver) Flashcards
What region is the pancreas located in?
-the epigastric region, close to the midline
What happens to the pancreas with age?
- decreases in size
- increases echogenicity
What tissue is the pancreas composed of?
-exocrine and endocrine (mostly exocrine)
What are the functions of the pancreas?
Exocrine
- digestion
- secretes pancreatic juice
- breaks down fat, carbohydrates and proteins
Endocrine
- hormones (glucagon and insulin)
- maintain sugar and salt balance
Acini Cells
- exocrine
- 80% performs exocrine functions
- small grape like structures with endocrine tissue in between
What is pancreatic juice composed of?
- amylase (carbohydrates)
- lipase (fats)
- trypsin (protein)
- chymotrypsin (protein)
- carboxypepidase (protein)
- nucleases (nucleic acids)
- sodium bicarbonate (neutralize hypochlorite acid)
What do digestive hormones do?
- release is stimulated by partially digested food
- cause the production of pancreatic juices
What are the Pancreatic Digestive Hormones?
- cholecystokinin, gastrin and acetylcholine (stimulate acini cells to produce digestive enzymes)
- secretin (stimulates production of sodium bicarbonate)
What is the main pancreatic duct?
Duct of Wirsung
What is the accessory duct?
Duct of Santorini
How does digestion occur?
- pancreatic juice collects in the Duct of Wirsung, then moves into the duodenum through the Ampulla of Vater
- the Sphincter of Oddi relaxes to allow the passage of juices
Endocrine Function
-secretes hormones directly into blood stream
What does the Islets of Langerhans consist of?
- alpha cells
- beta cells
- delta cells
What are the 3 pancreatic hormones?
- insulin
- glucagon
- somatostanin
Insulin
-glucose to glycogen
Glucagon
-glycogen to glucose
Somatostanin
-alpha and beta inhibitor (inhibit insulin and glucagon production)
What does the pancreaticoduodenal artery supply?
-supplies pancreas head and part of the duodenum
What do the branches of the splenic artery supply and where are they located?
- body and tail of pancreas
- courses on the superior edge (before it enters spleen)
- tortuous
Venous (pancreas)
-tributaries of SMV and SV
Is the pancreas retroperitoneal of intraperitoneal?
retroperitoneal
What are the 3 key regions of the pancreas?
- head
- body
- tail
What is the 4th region of the pancreas?
-the neck
Where is the pancreas head located?
-more inferior to the body and tail
Where is the pancreas neck and body located?
-more superficial than head and tail
Where is the pancreas tail located?
- more superior
- towards the spleen
What is the echogenicity of the pancreas?
- usually isoechoic or hyperechoic to the liver
- increases in echogenicity with age
- uncinate process can appear hypoechoic to the rest of the pancreas
What is the echotexture of the pancreas?
-homogenous (can have a mottled appearance)
Size of Pancreas
- size is comparable between males and females
- head is usually largest in dimension
- neck is usually the smallest
- body and tail are slightly smaller than head
Pancreas Shape
-varies
Pancreas Contour
- usually smooth (occasionally lobulated)
- if increased in echogenicity with age it can blend into retroperitoneal fat, making it hard to tell true size and contour
Landmarks for the Pancreas Head
- gastroduodenal artery (GDA): anterior lateral aspect of pancreas head and the second part of the duodenum lies lateral to the GDA
- common bile duct (CBD): posterior lateral aspect of head
- inferior vena cava (IVC): posterior
Pancreas Neck Landmarks
-anterior to the SMV and portosplenic confluence
Pancreas Body Landmarks
- superior mesenteric artery (SMA): easiest to find
- splenic vein (SV)
- superior mesenteric vein (SMV)
- body is medial to the portosplenic confluence
Pancreas Tail Landmarks
- splenic vein lies posterior to the tail
- splenic artery is tortuous and travels adjacent to the splenic vein (seen in cross section)
Duct of Wirsung
- dumps secretions into the duodenum via major papilla (ampulla of Vater)
- usually merges with common bile duct before entering the duodenum at the major papilla or ampulla of Vater
What is the size of the duct of Wirsung?
3mm or less
How does the duct of Wirsung appear?
- linear structure in the pancreas body (echogenic walls if beam is 90 degrees)
- anechoic (fluid filled)
What are some windows used when scanning the pancreas?
- supine (most common)
- right anterior oblique and left later decubitus
- left coronal
What organs may create problems when viewing the pancreas?
- stomach
- bowel
What organs may help us see the pancreas?
-liver
Where does the GDA originate?
-common hepatic artery
Where does the splenic vein originate?
-spleen
Where does the SMV originate?
-small intestine
What are some maneuvers/techniques used to view the pancreas better?
- standing up
- taking a breath in
- pushing belly out
What are the 2 main functions of the pancreas?
1) exocrine- creates pancreatic juice (aids in digestion)
2) endocrine- produces insulin
Echogenicity of Pancreas
-hyperechoic
Echotexture of Pancreas
-homogeneous or heterogenous (depending on fat)
Size of Pancreas
13-17cm long and 3-5cm wide
Where does the pancreas lie in the body?
- epigastric region
- retroperitoneal
- abdominal cavity
Landmarks for Pancreas
- head: CBD, GDA
- neck: portal confluence
- body: aorta, SMA
- tail: splenic vein
How does the pancreas start?
-2 buds that join together (dorsal and ventral) that fuse at 6 to 8 weeks
Dorsal (cranial) forms…
-body and tail
Ventral (caudal) forms…
-head and uncinate process
Annular Pancreas
- ring of pancreatic tissue that encircles the duodenum
- can cause problems
Cysts
- epithelium lined true cysts, anomalous development of the pancreatic duct
- multiple cysts are associated with cystic disease, von hippie lindau
Agenesis
- congenital absence of the body and tail
- the head is typically larger
Pancreatic Divisum
- most common
- lack of fusion of the dorsal and ventral pancreatic buds
- the duct of Wirsung and Santorini don’t fuse (most of pancreas is drained through duct of Santorini and minor papilla)
Is ultrasound the best way to image the pancreas?
no
What are some other imaging modalities that could be used to image the pancreas?
- CT
- MRI
Pseudomasses (false masses)
- not real, but can fool you when scanning
- appear as bugles
- extend to the right of GDA
- anterior body where left lobe liver touches the pancreas
- same echogenicity and texture as normal pancreas
What is the liver covered by?
-Glisson’s Capsule (thin connective layer)
Where is Glisson’s Capsule thickest?
-around the IVC
Is the liver intraperitoneal or retroperitoneal?
-intraperionteal, except for the bare area
What region is the liver located in?
- RUQ
- extends into epigastric and Lt hypochondrium
- majority lies beneath right costal margin
What are the borders of the liver?
- superior: diaphragm
- posterior: lumbar region of posterior abdominal wall
- anterior: abdominal wall, ribs
- inferior: organs (pancreas, Rt kidney, duodenum, colon, GB, lesser curvature of stomach)
What are the 2 main surfaces of the liver?
- anterior (aka parietal)
- posterior/inferior (aka visceral)
What are the 3 fissures in the liver?
- main lobar fissure (median)
- left intersegmental fissure
- right intersegmental fissure
Hepatoduodenal Ligament
-covers the porta hepatis entrance to the liver
Gastrohepatic Ligament
-connects lesser stomach to liver
Coronary Ligament
-connects posterior liver to diaphragm
Right and Left Triangular Ligament
-connects liver to body wall
What is the bare area?
- located on posterior superior aspect of the liver
- direct contact with diaphragm
- only part of the liver not covered by peritoneum
What are the similarities between hepatic and portal veins?
- both located within the liver
- walls compare
- relatively the same size
Intersegmental
-definite division between borders (hepatic veins)
Intrasegmental
-unclear division between borders (portal veins)
What is the normal size of the liver? (measuring posterior/superior to anterior/inferior tip)
- 13 to 17cm (Rt lobe)
- variable (Lt lobe)
What is the echogenicity of the liver?
echogenic
What is the echo texture of the liver?
homogenous
How does the echogenicity of the liver compare to the kidney?
-liver is hyperechoic or isoechoic to the kidney
How does the echogenicity of the liver compare to the spleen?
-the liver is hyopechoic to the spleen
What is the contour of the liver?
-smooth
What is the shape of the liver?
- Lt lobe: triangular shape
- Rt lobe: varies
What are the scanning approaches for the liver?
- subcostal (under ribs)
- intercostal (between ribs)
What are the patient positions for scanning the liver?
- supine
- Lt lateral decubitus
