Accessory Organs Flashcards
What ligament separates the liver into two lobes?
Falciform ligament
Purpose of hepatic ducts
Brings bile + bile salts from different liver lobes –> gallbladder
What is the porta hepatis? What is apart of it?
Where a lot of structures comes via inferior surface of liver
- Hepatic artery
- Hepatic portal vein
- Common hepatic duct: brings bile salt from liver –> S.I. (during meals) or gallbladder (storage)
Bile salts in-between meals
Travels from common hepatic duct –> gall bladder via cystic duct
What is the hepatopancreatic ampulla?
Common bile duct converges with pancreatic duct here
What is the Sphincter of Oddi?
- Duodenal papilla of the S.I.
- Goes to the duodenum
- Stays closed during meals
Dual blood supply of the liver
- Receives O2 rich blood from abdominal aorta via celiac trunk
- Mixes with the deoxy blood returning from GI tract
- All blood is drained by hepatic vein –> IVC –> RA
Cell types of the liver (x2)
Hepatocytes and Kupffer cells
Which liver cell makes up most of the liver cells?
Hepatocytes
Functions of hepatocytes
Synthesize proteins, store nutrients (glucose + lipids), detoxify drugs + metabolize Vit D
Functions of Kupffer cells
- 80% of body’s macrophages
- Exist in dilated spaces between hepatocytes
- Phagocytosis of microbes, toxins, damaged WBCs & RBCs
- Found in hepatic sinusoids
Hepatic sinusoids
- Formed by sinusoid capillaries (huge gaps + incomplete basement membrane)
- Allows proteins (albumin, clotting factors + complement proteins) made by hepatocytes to move through
Hepatic triad
- Bile duct
- Venule from hepatic portal vein
- Hepatic arteriole from hepatic a.
Flow of blood and bile
The direction of bile flow is opposite to the blood
Roles of the liver
- Process/store intestinal nutrients (amino acids, lipids + vitamins)
- Synthesis of serum proteins
- Process drugs & hormones
- Storage of iron & excretion of bilirubin
- Aids in digestion (bile)
Why can’t the liver store glucose?
Water follows glucose so hepatocytes would burst
This is why it has to be stored as glycogen
Role of glycogen
Liver stores glucose (monosaccharide) as glycogen (polysaccharide)
Breaks down into glucose during times of need (used by CNS)
What happens when the sugar capacity is full?
Liver converts glucose into fatty acids or triglycerides
Goes to adipose
Gluconeogenesis
Liver creates glucose from lactic acid (waste from anaerobic respiration), pyruvate & amino acids (broken down, use the C chains)
Can also be made from triglycerides (with glycerol backbone)
Why can’t you use the glycogen in skeletal muscle?
Because its been phosphorylated so its trapped in skeletal muscle and can’t be used by other systems
Processing of amino acids
Essential amino acids are used for protein synthesis (e.g. albumin)
The liver converts toxic ammonia to urea (water soluble; then excreted by kidneys)
- Ammonia is produced during the breakdown of amino acids in liver
What are chylomicrons?
The way in which breakdown products of fatty acids are packaged by the intestinal absorptive cell –> lacteal –> circulation
What are lipoproteins?
Lipids attached to proteins; makes them miscible in the watery matrix of blood
Lipoproteins (x3)
- VLDL: transports fats made by hepatocytes (liver) –> adipocytes
- LDL: transports cholesterol to tissues
- Excess of this accumulates under the endothelium in blood vessels
- Most cholesterol is generated by liver (not just from diet)
- HDL: returns excess cholesterol from tissues –> liver (puts it into bile salts)
NOTE: fibre can trap cholesterol + eliminate it (high fibre diet)
Vitamin A
Converted to retinyl esters (vision, rods for night vision)
Vitamin D
Used in bone metabolism
- Active form of Vit D (calcitrol) tells kidney not to pee out calcium
Can be synthesized (needs UV)
- UV activates precursors in skin –> liver –> kidney (controlled by PTH)
Vitamin E
Antioxidant
ROS reacts with proteins + DNA which results in aging
Vitamin E gets rid of ROS
Vitamin K
Utilized by hepatocytes to form functional coagulation factors
Synthesis of serum proteins
Liver synthesizes: albumin, coagulation factors, complement proteins and a & b globulins
Role of albumin
Provides colloid osmotic pressure that allows for fluid that escaped the capillary bed to come back into vascular space (so we don’t lose too much fluid to the tissues)
Acts as a taxi for hormones/cations/bilirubins etc.
Storage of iron
Liver stores iron via ferritin
Iron is bound to transferrin for transport in circulation
Heme from damaged RBCs return to the liver where iron is scavenged & the heme is discarded as bilirubin (bile)
Accumulation of bilirubin in tissues = jaundice
Functions of bile
- Lipid digestion
- Cholesterol metabolism
- Excretion of lipid soluble drugs
Composition of bile
- Bile salts (for emulsification)
- Cholesterol
- Bilirubin
- Electrolytes (sodium + chloride)
Bile storage + recycling
Stored in the gall bladder until needed
Recycled by the ileum (was dumped into duodenum to help w fat breakdown)
How to reduce cholesterol
Lots of fibre!
Reduces cholesterol + increased excretion of excess bile
3 F’s of developing gallstones
Female, 40 & fertile
Estrogen = more cholesterol and less water
Control of gallbladder function
Parasym input = very weak contractions during cephalic phase + tells liver to increase bile production
When fat enters duodenum, CCK and secretin are released
CCK gets gallbladder smooth muscle to contract + release bile
Secretin increases production of bicarb-rich bile secretions by hepatocytes
Exocrine functions; pancreas
Products of exocrine (juices/enzymes) enter the duodenum via hepatopancreatic ampulla
90% of pancreas
Gall stones at Sphincter of Oddi
Leads to pancreatitis
Pancreatic secretion backup: inflammatory enzymes can activate pancreatic enzymes –> autodigestion
Endocrine functions; pancreas
Endocrine products enter the BS
Occurs in Islets of Langerhans
- Secrete hormones (insulin + glycogen) that go into BS and regulate glucose
Regulation of pancreatic exocrine function
During cephalic phase, vagus n. activates pancreas to release bicarb-rich juice (weak activation)
Chyme enters duodenum –> CCK and secretin release
Pancreatic endocrine function (blood glucose homeostasis)
Glucagon is released from alpha cells of pancreatic islets
Insulin is released from beta cells
High blood sugar = increased insulin (tells tissues to store glucose)
- Liver turns glucose –> glycogen
Low blood sugar = increased glycogen
- Glucagon talks to liver to convert glycogen –> glucose
