6 - Development of Intestine and Liver Flashcards
Where is the liver located in the human body
In the upper right quadrant of the abdomen, just below the diaphrag
What is the typical weight of the liver in adults
Approximately 1.3–1.5 kg
What type of blood supply does the liver have
Dual blood supply via the hepatic artery and hepatic portal vein
What are the four lobes of the liver
Right lobe (largest)
Left lobe
Caudate lobe (near inferior vena cava)
Quadrate lobe (near gallbladder)
Why is the liver a target for toxicity
It processes drugs, chemicals, and toxins
What embryonic structures form the pharynx
Branchial arches and pharyngeal pouches
What germ layers contribute to these structures
Endoderm, mesoderm, and ectoderm
What is the evolutionary significance of branchial arches
They are evolutionarily related to gills in fish
What are hepatocytes
The main functional cells of the liver, making up 70–80% of the liver’s cytoplasmic mass.
What are the key functions of hepatocytes
Metabolism, detoxification, bile production, storage, and immune function
What is glycogen storage in the liver used for
To store glucose and release it during fasting via glycogenolysis
What is stored in hepatic lipid droplets
Triglycerides and cholesterol
What vitamins are stored in the liver
Fat-soluble vitamins A, D, E, K, and vitamin B12
How is iron stored in the liver
As ferritin, for later use in red blood cell production
Are amino acids stored in the liver
No, but they are metabolized and used for protein synthesis (e.g., albumin, clotting factors)
What are Kupffer cells
Specialized macrophages located in the liver sinusoids
What is the function of Kupffer cells
Phagocytosis of old RBCs, bacteria, and detoxification of blood by removing endotoxins
Where are stellate cells found
In the perisinusoidal space of the liver
What is their main storage function
Store vitamin A as retinol esters
What is the function of fenestrae in LSECs
Facilitate nutrient/waste exchange and enhance filtration of large molecules
How do they support liver detoxification
By allowing hepatocytes to access substances in the blood and aiding Kupffer cell function
What germ layers contribute to gut tube formation
Endoderm and mesoderm
What does visceral mesoderm form
The organs of the gut
What does parietal mesoderm form
The peritoneum and abdominal wall
What role do Hox genes play in the digestive tract
They regulate regionalization of the gut
What induces posterior Hox gene expression
Sonic Hedgehog (Shh) from the hindgut endoderm
What happens to excess amino acids
They are catabolized in the liver via transamination
What enzyme is key in this process
Transaminases (aminotransferases)
What is glycolysis
The breakdown of glucose to pyruvate, generating ATP and NADH
What is glycogenesis
The synthesis of glycogen from glucose, regulated by insulin
What is glycogenolysis
The breakdown of glycogen into glucose during fasting
What is gluconeogenesis
The synthesis of glucose from non-carbohydrate sources (e.g., amino acids, lactate, glycerol)
What is the function of bile acids in digestion
Emulsify fat globules, increasing surface area for enzyme action
What are micelles
Lipid aggregates formed by bile acids to transport fats and fat-soluble vitamins in water
Where does the liver originate from
The ventral foregut endoderm (hepatic diverticulum or liver bud)
What defines the hepatogenic region
The presence of transcription factors like FoxA1/2 and GATA4/6 that confer competence
What tissues provide inductive signals for liver development
The cardiac mesoderm (via FGF and BMP)
What tissues inhibit liver formation dorsally
The notochord and neural tube, through signals like Chordin, Lefty, and Noggin
What experimental evidence supports this
Placing ectoderm or notochord next to competent endoderm prevents liver formation
How does the liver detoxify drugs like acetaminophen
Through glucuronidation, adding glucuronate to the drug to make it water-soluble
Why is glucuronidation important
facilitates excretion of xenobiotics via urine or bile
