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

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

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

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

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

    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?

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    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 ?

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    8/17Liver Physiology, Larry Frolich, Yavapai College, March 10, 2006

    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

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    9/17Liver Physiology, Larry Frolich, Yavapai College, March 10, 2006

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

    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)

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    11/17Liver Physiology, Larry Frolich, Yavapai College, March 10, 2006

    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
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    12/17Liver Physiology, Larry Frolich, Yavapai College, March 10, 2006

    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?

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    13/17Liver Physiology, Larry Frolich, Yavapai College, March 10, 2006

    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

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    14/17Liver Physiology, Larry Frolich, Yavapai College, March 10, 2006

    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

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    15/17Liver Physiology, Larry Frolich, Yavapai College, March 10, 2006

    Cholesterol processing in liver and relation to

    cardio-vascular disease and arterial plaques

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

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

    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