Download - Liver Function 3

7/28/2019 Liver Function 3

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Liver Physiology, Larry Frolich, Yavapai College, March 10, 2006

The Liver

To get there, we need to1. Get it situated (ANATOMY)

2. Get it a blood supply with all the stuffin the blood that it needs to do its work(PHYSIOLOGY or organ-levelfunction)

3. See the micro-structure of the liver(HISTOLOGY)

4. Marvel at the wonder of hepatocytes,or liver cellsare they perhaps themost intelligent entities on the planet?(CELL BIOLOGY)

The Challenge: In 20 minutes,

can we at least startto find outwhat the liver has to do withcholesterol levels in our body?


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Liver Brainstorm

Largest solid-mass

organ of the body

Perhaps least

understood, bothpopularly and

scientifically?

Brainstorm: 30 seconds

and three adjectives or

phrases (good to do in

previous class or on-line)

Liver Brainstormtake

30 seconds to write

what comes outtop of

your headAdjective/phrase 1:

Adjective/phrase 2:

Adjective/phrase 3:


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Locate your liver

Upper right quadrantdeep to inferior ribs

Dome of liver abutsaganst inferiordiaphragm surface

Left/right lobes Gall bladder is thin

muscular sac on inferiorsurface where bile

collects (1 above)1. ANATOMY


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Measuring liver span by percussion: variation in liver spanVariation in liver span according to the vertical plane of examination. Since there isvariability in where clinicians determine the mid-clavicular line to be, the inevitableconsequence is that liver span may also vary even if multiple observers are

perfectly accurate in measuring it.

Percuss your liver

Easiest organ topercuss

Dense tissue givesrock-solid sound/feelon percussion

Mid-clavicular linemoving inferiorly frommid-chest to lowerright quadrant


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What does the liver do?

Temporary nutrient storage (glucose-glycogen)

Remove toxins from blood

Remove old/damaged RBCs

Regulate nutrient or metabolite levelsin bloodkeep constant supply ofsugars, fats, amino acids, nucleotides(including cholesterol)

Secrete bile via bile ducts and gall

bladder into small intestines.

2. PHYSIOLOGY

Multi-function, blood-processing factory

Needs blood supply laden with stuff to process


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Dual blood supply to liver:

1. Hepatic portal system (review)

Main drainage of

blood from gutwhy

to liver?

Why does liver need

another blood supply?

What does this blood

NOT have that liver(and any organ)

needs?


7/17Liver Physiology, Larry Frolich, Yavapai College, March 10, 2006

Primary branch from celiacartery which is one of the threemain visceral branches of aorta(review from circulation)

Brings oxygen-rich blood

Within liver lobules, bloodmixes:

Nutrient-rich, toxin-laden,oxygen-poor blood from gut viahepatic portal vein

Oxygen-rich blood from hepaticportal artery

Dual blood supply to liver

2. Hepatic artery (review)

Wh d th t bl d li i ?



Where do the two blood supplies mix?

Triads: Branches of three vessels: hepaticportal vein, hepatic artery, along with biledrainage ductiles all run together to infiltrateall parts of liver.

Sinusoidsspecial liver capillaries whereblood mixes and liver cells actby-productsleave as bile in caniliculi which merge to form

bile ducts3. HISTOLOGY



Hepatocytes at work

4. CELL BIOLOGY

Metabolic map of liverPDF link

Hepatocytes are incredible chemical transformationfactories

Just deep to epithelial lining of sinusoids

Able to convert from one type of organic substrate (sugar,protein, fat, nucleotide) to another

Produce bile

Kuppfer cellimmune function
http://faculty.ccri.edu/lmfrolich/Yavapai/MetabolicMapLiver.pdfhttp://faculty.ccri.edu/lmfrolich/Yavapai/MetabolicMapLiver.pdf



What is bile?

Bile composed of water, ions, bileacids, organic molecules (includingcholesterol, phospholipids, bilirubin)

Gallstones are mostly cholesterol

Acids and salts emulsify fats for

absorption across wall of smallintestines into lacteal lymph capillaries(review)

Contains waste products from RBC

breakdown and other metabolicprocessing (color of feces frombilirubin in bile)(review)

Ions buffer chyme from stomach(review)



Great bile page with entero-

hepatic recirculation animation

(from Colorado State University)

Bile processing and recycling

Hepatocytes initially secrete

bile into canaliculi, carried to

gall bladder via hepatic ducts

Gall bladder stores bile untilneeded in gut when secreted

out cystic duct to common

bile duct to duodenum

95% of the bile produced bythe liver is recycledoften

2 or 3 times during the

digestion of a single meal
http://www.vivo.colostate.edu/hbooks/pathphys/digestion/liver/bile.htmlhttp://www.vivo.colostate.edu/hbooks/pathphys/digestion/liver/bile.htmlhttp://www.vivo.colostate.edu/hbooks/pathphys/digestion/liver/bile.htmlhttp://www.vivo.colostate.edu/hbooks/pathphys/digestion/liver/bile.htmlhttp://www.vivo.colostate.edu/hbooks/pathphys/digestion/liver/bile.htmlhttp://www.vivo.colostate.edu/hbooks/pathphys/digestion/liver/bile.html



Cholesterolone example of liver processing

Our body needs cholesterol for Cell membranes

Vitamin D

Hormonesprogesterone and testosterone

Myelin (neuron axonal wrapping)

Component of bile salts

85% of cholesterol in our blood is endogenousor manufactured by our own cells (mostly liver)

15% comes from the food we eat

So, is zero-cholesterol goodor even healthy?



Cholesterol in the liver:

Wheres it from? Wheres it go?

Liver constantly manufactures cholesterol

using acetyl-CoA as substrate

Some cholesterol to gut via bile for

emulsification of dietary fats

Some cholesterol to blood for cell

membranes, myelin, hormones, vitamins



Good and bad cholesterol

Two ways cholesterol is packed LDLlow density lipo-proteins (bad)

HDLhigh density lipo-proteins (good)

LDL is component of arterial plaques that can lead to blockedarteries

HDL can help to clear LDL from arterial walls

Packing of cholesterol and interactions with other dietaryand liver-produced fats maybe more important than

cholesterol levels alone Trans and saturated fats (especially artificially hydrogenated

fats) may be most culpable element of diet in raising LDLlevels

Mono-unsaturated fats (such as olive oil, canola oil) alongwith dietary fiber raise HDL levels



Cholesterol processing in liver and relation to

cardio-vascular disease and arterial plaques


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Other liver cell functions

Red blood cell decomposition and

recycling of components

Toxin neutralization

Conversion of substrates: altering amino

acids, amino acids to sugars, sugars to

amino acids, etc.to insure adequate

supply of necessary molecules of life.


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Summary

ANATOMY: Locate liver by percussing upper rightquadrant of abdomen

PHYSIOLOGY: Liver is blood processing organ with dualblood supply.

HISTOLOGY: Blood mixes in sinusoids where hepatocytesdo their magic

CELL BIOLOGY: Multiple functions for hepatocytes.Manufacture cholesterol for use and recycling in digestion(via bile) and delivery to cells of body via circulatory system

(via central vein of liver lobules). Cholesterol is necessary for many normal metabolic processes

High levels of LDL cholesterol may contribute to plaque formation inarteries

HDL cholesterol may help to break down plaques