Accessory Digestive Organs
Terms in this set (130)
Where is the liver located?
In the abdominal cavity, below the diaphragm
What is Glisson's Capsule?
The thin connective tissue covering over the liver (thicker at the hilum)
What enters at the hilum?
The portal vein and hepatic artery
What exits at the hilum?
The hepatic ducts (bile) and lymphatics
What are the functions of the liver?
- Produces most of the plasma proteins
- Stores and converts several vitamins and iron
- Degrades drugs and toxins
- Metabolic pathways
- Bile production
- Endocrine-like functions
What plasma proteins are produced by the liver?
- Other clotting proteins
- Alpha- and beta-globulins
What vitamins are stored and converted by the liver?
- Vitamin A
- Vitamin D
- Vitmain K
What metabolic pathways is the liver involved in?
- Amino Acids
What type of amino acids are produced by the liver?
Non essential amino acids
What is the exocrine function of the liver?
What are the 3 main components of bile?
3. Bile salts
What are the functions of bile?
- Aids in absorption of lipids from intestine
- Disposal of conjugated/degraded waste products
What are the endocrine-like functions of the liver?
Modifies structure and function of many hormones
(Vitamin D, thyroxine, growth hormone, insulin, and glucagon)
Describe the blood supply to the liver.
Dual blood supply!
- Venous (portal) supply via the hepatic portal vein
- Arterial supply via the hepatic artery
Which blood supply makes up 75% of the blood supply to the liver?
The venous portal blood
- largely depleted of oxygen
Where does the blood come from that is found in the venous portal supply?
It is the blood that initially supplied the intestines, pancreas, and spleen
What is found in the portal blood?
- Nutrients and toxins that were absorbed in the intestines
- Blood cells and breakdown products of RBC from the spleen
- Endocrine secretions from the pancreas and GI tract
Arterial blood makes up what percentage of the blood supply to the liver?
What happens to the two blood supplies before they perfuse the hepatocytes?
They are mixed
Are hepatocytes exposed to fully oxygenated blood?
Never, bc the two blood supplies are first mixed
What is the parenchyma of the Liver?
The organized plates of hepatocytes
What is the connective tissue stroma continuous with?
With the fibrous capsule
What travels within the stroma?
Blood vessels, nerves, lymphatic vessels, and bile ducts
What are the sinusoidal capillaries?
- the vascular channels between plates of hepatocytes
What are the perisinusoidal spaces?
Spaces of Disse
- They lie between the sinusoidal endothelium and the hepatocytes
What are the 3 ways to describe the structure of the liver?
1. Classic lobule
2. Portal lobule
3. Liver acinus
What is the classic lobule based on?
The distribution of the branches of the portal vein, hepatic artery, and the direction of blood flow
What shape is the classic lobule?
What does the classic lobule consist of?
Stacks of anastomosing plates of hepatocytes separated by sinusoidal capillaries
What is the classic lobule centered on?
A terminal hepatic venule (central vein)
What do you find in the corners of a classic lobule?
Portal areas that contain the Portal Triads
What structure is emphasized in the portal lobule?
The flow of bile
(the exocrine function of the liver = bile production and secretion)
What shape is the portal lobule?
What is located in the center of the portal lobule?
The portal area containing the bile duct
What is located at the corners of a portal lobule?
The terminal hepatic venule (central veins)
In which direction does bile flow in the portal lobule?
It flows toward the bile duct in the portal area (so towards the center of the lobule)
Which structural unit provides the best correlation between blood perfusion, metabolic activity, and liver pathology?
The liver acinus
What shape is the liver acinus?
The short axis of the liver acinus extends between...
... two adjacent portal areas
The long axis of the liver acinus extends between...
... two terminal hepatic venules
What makes up the liver acinus?
Parts of two adjacent classic lobules
What is zonation?
Seen in the liver acinus
- It is important in the description and interpretation of patterns of degeneration, regeneration, and specific toxic effects
Describe Zone 1 Cells.
- First to receive oxygen, nutrients, and toxins from the blood
- First to show effects of bile duct obstruction
Describe Zone 2 Cells.
The intermediate zone between zone 1 and 3 cells
Describe Zone 3 Cells.
- First to show effects of reduced perfusion
- Last to respond to toxins and bile salts
Do blood and bile flow in the same direction within the liver?
NO they flow in opposite directions
What kind of endothelium is present in the hepatic sinusoids?
- there are large fenestrae without diaphragms within the endothelium
- large gaps between cells
Describe the basal lamina in the hepatic sinusoids.
It is also discontinuous
What are Kupffer cells?
Stellate sinusoidal macrophages of the liver
- regular part of the vessel lining
Where is the space of Disse located?
Between the basal surfaces of the hepatocytes and the basal surfaces of the endothelial/kupffer cells
What is the site of exchange of materials between the blood and liver cells?
The perisinusoidial space (space of Disse)
Is there a barrier between the blood plasma and the hepatocytes?
No significant barrier exists
Where are islands of blood forming cells located in the fetal liver?
In the space of Disse
Where are Ito cells located?
Space of Disse
What is the primary site of storage for hepatic vitamin A?
In the Ito cells (within cytoplasmic lipid droplets)
What happens to Ito cells when they lose their lipid droplets and ability to store vitamin A?
They differentiate into myofibroblasts
- play a role in hepatic fibrogenesis resulting from liver fibrosis
What happens to plasma that remains in the perisinusoidal space?
It drains to the periportal area and into the space of Mall
What happens to fluid in the space of Mall?
It enters the lymphatic capillaries located in the portal canals
Where do the lymph vessels that exit the hilum drain?
Mostly to the thoracic duct
A major portion of the thoracic duct lymph comes from where?
Under normal circumstances, do hepatocytes have a fast or slow turnover rate?
A relatively slow turn over rate
Do hepatocytes have a regenerative capacity?
Yes, they have a considerable regenerative capacity when hepatocytes are lost to toxins, disease, or surgery
What are the prominent features of hepatocytes?
Function of RER in liver.
Synthesis of plasma proteins
Function of golgi in liver.
Function of SER in liver.
(all required for inactivation and detoxification of substances before excretion)
Function of lysosomes in liver.
Turnover of intracellular organelles
Function of peroxisomes in liver.
- Oxidation of fatty acids
- Breakdown of purines
- Synthesis of cholesterol, bile acids, and myelin lipids
... bile into bile canaliculi
What is the bile canaliculi?
a small canal formed by apposed grooves in the surface of adjacent hepatocytes
In which direction does bile flow in hepatocytes?
From the region of the central vein toward the portal canal
What happens to the bile canaliculi near the portal canals?
They join to form the intrahepatic ductules (aka: Canals of Hering)
What lines the canals of hering?
They are partially lined by hepatocytes and partially by cholangiocytes
Canals of herring consist of...
... hepatic stem cells (possibly)
What do intrahepatic ducts drain into?
Interlobular bile ducts in the portal canals
Interlobular ducts eventually lead to what?
Extrahepatic bile ducts
Extrahepatic bile ducts deliver bile where?
To the gallbladder and duodenum
Where is the gallbladder located?
It is attached to the lower surface of the liver
What type of epithelium makes up the mucosa of the gallbladder?
Simple columnar epithelium
What do the walls of the gallbladder contain?
What does the mucosa of the gallbladder contain?
Abundant folds and epithelial cells that are rich in mitochondria
What is the main function of the gallbladder?
To store bile, concentrate it, and secrete it when necessary to the digestive tract
What induces contraction of the smooth wall of the gallbladder?
From where is CCK released?
From enteroendocrine cells of the small intestine
What signals enteroendocrine cells to secrete CCK?
The presence of dietary fats in the small intestine
What type of gland is the Pancreas?
A mixed gland - both endocrine and exocrine
Where is the exocrine portion of the Pancreas located?
Throughout the organ
Where is the endocrine portion of the pancreas located?
In the Islets of Langerhans, dispersed throughout the organ
How would you classify the exocrine portion of the pancreas?
As a compound acinar gland
What are the acini of the pancreas composed of?
Serous cells surrounding a lumen
What type of cells are the serous cells of the acini in the pancreas?
They typical protein secreting cells
Where are proenzymes stored and released?
In the acinar cells of the pancreas
What else is contained in acinar cells?
Zymogen granules (number varies according to digestive phase)
What do acini empty into?
What type of cells make up the intraacinar portion of the intercalated duct?
Centroacinar cells (characterized by a pale cytoplasm)
Intercalated ducts empty into...
Intralobular ducts form...
... Interlobular ducts
What lines interlobular ducts?
Columnar epithelium within connective tissue septae
What enzymes are produced by acinar cells?
- Proteolytic enzymes (trypsin, chymotrypsin)
How are enzymes stored in the secretory granules of acinar cells?
(they are activated in the lumen of the small intestine after secretion)
What cleaves trypsinogen?
Enterokinase (an intestinal enzyme)
What does trypsinogen get cleaved into?
What is the function of trypsin?
It activates the other proteolytic enzymes in a cascade
Why are enzymes stored as proenzymes?
To protect the pancreas from the active enzymes
What else protects the pancreas?
Protease inhibitors that are synthesized by acinar cells
What two hormones control pancreatic secretion?
2. Cholecystokinin (CCK)
What produces secretin and CCK?
Enteroendocrine cells of the intestinal mucosa (duodenum and jejunum)
What stimulates the release of secretin?
Gastric acid in the intestinal lumen
What is the function of secretin?
It causes duct cells to secrete a large volume of bicarbonate rich fluid that neutralizers the acid and allows pancreatic enzymes to function
What stimulates the release of CCK?
Fatty acids, gastric acid, and certain amino acid in the intestinal lumen
What is the function of CCK?
It causes acinar cells to secrete their proenzymes
What is the common function of secretion and CCK?
They act to cause a secretion of a large volume of protein-rich, alkaline, pancreatic fluid
What do the islets of langerhans consist of?
Cords of polygonal cells invested with a network of fenestrated capillaries
What are the 3 major cell types of the pancreas?
- B (beta) cells
- A (alpha) cells
- D (delta) cells
Where are B cells located?
Centrally in the pancreas
What do B cells secrete?
Where are A cells located?
In the periphery of the pancreas
What do A cells secrete?
Where are D cells located?
In the periphery of the pancreas
What do D cells secrete?
What major cell is most prominent?
What are the 3 minor cell types in the pancreas?
- PP Cells (F cells)
- D-1 Cells
- EC Cells
What do PP cells secrete?
What do D-1 cells secrete?
Vasoactive intestinal peptide (VIP)
What do EC cells secrete?
Secretin, motilin, substance P
What is the major function of the endocrine pancreas?
To regulate blood glucose levels
What is the major hormone secreted by the islets?
What is the function of insulin?
To decrease blood glucose levels
What is the function of glucagon?
To increase blood glucose levels (reciprocal to insulin)
What is the function of somatostatin?
To inhibit both insulin and glucagon secretion
YOU MIGHT ALSO LIKE...
DAT Survey of Natural Sciences | Kaplan Guide
Accessory Digestive Organs: Liver, Gallbladder, and Pancreas
Histology Quiz - Liver, Pancreas
GI Lecture 2
OTHER SETS BY THIS CREATOR
OMT Fast Facts
THIS SET IS OFTEN IN FOLDERS WITH...
Digestive System Development 1
B3-Cell (pkt 7): Accessory Digestive Organs Pt 1
Development of the Face