STRUCTURE AND COMPOSITION

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STRUCTURE AND COMPOSITION
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• The most abundant tissues in meat are
• Connective Tissue and Muscle
• A distant second are epithelial and nervous
  tissues

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• V. STRUCTURE OF MUSCLE TISSUE
• A. TYPES OF MUSCLE TISSUE
• 1. STRIATED OR SKELETAL MUSCLE VOLUNTARY
• 2. SMOOTH MUSCLE INVOLUNTARY
• 3. CARDIAC MUSCLE STRIATED INVOLUNTARY
• WHAT IS THE DIFFERENCE BETWEEN VOLUNTARY AND
  INVOLUNTARY MUSCLE?

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• B. SMOOTH MUSCLE FIBER AND FUNCTION
• 1. VERY SMALL PORTION OF MEAT
• 2. MAINLY LOCATED IN THE ARTERIAL WALLS AND LYMPH
  VESSELS
• 3. ALSO IN THE GASTROINTESTINAL AND REPRODUCTIVE
  TRACTS
• 4. VARY IN SIZE AND SHAPE RANGING FROM FLAT
  ELLIPSOIDS TO TRIANGLES
• 5. SARCOLEMMA FORM TIGHT MEMBRANE TO MEMBRANE
  JUNCTIONS THAT ALLOW FOR COMMUNICATION

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• 6. EACH CELL CONTAINS ONE NUCLEUS WHICH IS
  CENTERED IN MOST CELLS
• 7. SR IS MUCH LESS DEVELOPED
• 8. MYOFILAMENTS ARE LESS ORDERED ARRANGED IN
  PAIRS THAT RUN PARRALEL TO THE LONGITUDINAL AXIS
  OF THE FIBER
• 9. ACTIN LIKE MOLECULES ARE ASSOCIATED WITH
  FILAMENTS
• 10. MYOSIN IS PRESENT (ABUNDANT) BUT NOT
  ACCOUNTED FOR.

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• 11. MYOFILLAMENTS ARE ATTACHED TO THE DARK ZONES
  OF THE SARCOLEMMA Z DISKS THIS IS BECAUSE THE
  MOVE WITH THE OCCURING CONTRACTION
• 12. SMOOTH MUSCLE FIBERS CAN OCCUR EITHER SINGLY
  OR IN BUNDLES
• 13. CONNECTIVE TISSUE AIDS IN TRANSMITTING FORCE
  DURING CONTRACTION-LESS BLOOD SUPPLIED

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• C. CARDIAC MUSCLE
• 1. RHYTHMIC CONTRACTION
• 2. BRANCHED STRIATIONS AND MORE MITOCHONDRIA AND
  GLUCOSE GRANULES
• 3. RESEMBLES BOTH SKELETAL AND SMOOTH MUSCLE IN
  DESIGN
• SINGLE NUCLEATED LIKE SMOOTH MUSCLE BUT
• MORE ORGANIZED LIKE SKELETAL
• 4. STRUCTURE NOT NECESSARY FOR THIS CLASS

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• D. SKELETAL MUSCLE
• 1. CONSTITUTES 35 65 WT CARCASS
• 2. OVER 600 SEPARATE MUSCLES
• 3. SPECIFIC CHARACTERISTICS
• OF A GIVEN MUSCLE ARE
• DICTATED BY ITS FUNCTION
• OR LOCAL!
  
• EX. LONGISSIMUS DORSI

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• 4. MUSCLE IS COVERED BY CONNECTIVE TISSUE FROM
  THE OUTERMOST REGIONS TYING TO THE INNER MOST
  REGIONS
• 5. CONNECTIVE TISSUE SERVES AS THE CARRIER OF
  NERVE AND BLOOD VESSEL INNVERVATION

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• 6. SKELETAL MUSCLE TISSUE MYOFIBER/MUSCLE CELL
  OR MUSCLE FIBER
• 7. MUSCLE FIBER 75 TO 92
• 8. THE REMAINING IS CONNECTIVE TISSUE, BLOOD
  VESSELS, NERVE FIBERS AND EXTRACELLULAR FLUIDS
• 9. BOTH MAMMALIAN AND AVIAN
• LONG
• MULTI-NUCLEATED
• UNBRANCHED THREADLIKE CELLS
• TAPER AT BOTH ENDS

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• 10. FIBERS DO NOT EXTEND THE LENGTH OF THE MUSCLE
• 11. DIAMETER CAN RANGE FROM 10 TO 100 ?m

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• SARCOLEMMA MEMBRANE SURROUNDING THE MUSCLE
  FIBER
• STRUCTURE AND COMPOSITION SIMILAR TO THE
  PLASMALEMMA OF OTHER CELLS
• SARCOPLASM CYTOPLASM OF MUSCLE FIBERS
• 70-80 H2O, WITH LIPID, GLYCOGEN, RIBOSOMES,
  NUMEROUS PROTEIN AND NON PROTEIN NITROGEN, OTHER
  INORGANIC
• NUCLEI DUE TO LENGTH VARIATION THE NUMBER OF
  NUCLEI ARE NOT CONSTANT IN A MUSLCE FIBER
• ONE EVERY 5 ?m ALONG THE LENGTH OF THE FIBER

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• T- TUBULE SYSTEM INVAGINATIONS OF THE
  SARCOLEMMA
• WHY?
• MOTOR NERVE FIBER ENDINGS TERMINATE AT THE
  MYONEURAL JUNCTION CONNECT TO THE SARCOLEMMA

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MYONEURAL JUNCTION
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• MYOFIBRILS HOUSE THE SMALLEST CONTRACTILE UNIT
  IN MUSCLE
• BATHED IN SARCOPLASM AND EXTEND THE ENTIRE LENGTH
  OF THE MUSCLE FIBER
• MYOFILAMENTS THICK AND THIN FILAMNENT OF THE
  MYOFIBRIL
• THICK AND THIN FILAMENT DIFFER IN DIMENSION AND
  CHEM COMP, PROPERTIES AND POSITION
• THE TWO MAIN CONTRACTILE PROTEINS ARE
• ACTIN AND
• MYOSIN

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• I-BAND SINGLY REFRACTIVE - ISOTROPIC
• A-BAND DOUBLY REFRACTIVE - ANISOTROPIC
• Z-DISK SEPARATE AJOINING SARCOMERES THEY OFF
  SET THIN FILAMENT ATTACHMENTS
• SARCOMERE LENGTH IN RESTING MUSCLE 2.5?m
• H ZONE, PSEUDO H ZONE AND M LINE VARY
  DEPENDING ON CONTRACTION STATE

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Proteins of Muscle

• 20 DIFFERENT PROTEINS
• 6 ACCOUNT FOR 90 PERCENT OF THE MYOFIBRILLAR
  PROTEIN
• MYOSIN
• ACTIN
• TITIN
• TROPOMYOSIN
• TROPONIN
• AND NEBULIN

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• MYOFIBRILLAR PROTEINS ARE CLASSIFIED AS
• CONTRACTILE
• REGULATORY
• CYTOSKELETAL
• CONTRACTILE MYOSIN AND ACTIN
• REGULATORY TROPOMYOSIN AND TROPONIN
• CYTOSKELETAL TITIN AND NEBULIN

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• Actin 20 of MFP
• Globular shaped and referred to as G-actin
  (monomeric form)
• Fiborus form of actin is referred to as F-actin
  (G-actin polymerize)
• 2 strands of F-actin form a superhelix thin
  filament
• Myosin Fiborus protein 45 of MFP
• Elongated rod shape with a thick head at one end
• Head portion of myosin is doubled on each rod
• The head portion is the functional portion of the
  thick filament
• Form cross-bridges with actin that facilitate
  contraction
• During contraction the myosin heads bind to
  G-actin

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• Tropomyosin
• 5 MFP
• Close contact with the thin filament
• Troponin
• 5 MFP
• Present in the grooves of the thin filament
• Titin
• 10 MFP
• Extends from the m-line to the z-disk
• Believed to provide the scaffolding during
  sarcomere and myofibril formation
• Nebulin
• 4 MFP
• Parrallel to the thin filament
• Believed to play a role as scaffolding in the
  thin filament Development

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CL UCL 1 1 3 6 12 24 48
CL UCL 1 1 3 6 12 24 48
TNT 42kD 30kDa
CLPG
NML
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• Sarcoplasmic Reticulum Intracellular membrane
• Sytem of tubules and cisternae (reservoirs for
  calcium stores)

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• Sarcoplasmic Reticulum Intracellular membrane
• Sytem of tubules and cisternae (reservoirs for
  calcium stores)
• Forms a closely meshed net work around each
  myofibril

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• Sarcoplasmic Reticulum Intracellular membrane
• Sytem of tubules and cisternae (reservoirs for
  calcium stores)
• Forms a closely meshed net work around each
  myofibril
• H-zone longitudinal tubules converge
  Fenestrated collar

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• Sarcoplasmic Reticulum Intracellular membrane
• Sytem of tubules and cisternae (reservoirs for
  calcium stores)
• Forms a closely meshed net work around each
  myofibril
• H-zone longitudinal tubules converge
  Fenestrated collar
• Jxn of the A and I bands longitudinal tubules
  converge with terminal cisternae

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• Sarcoplasmic Reticulum Intracellular membrane
• Sytem of tubules and cisternae (reservoirs for
  calcium stores)
• Forms a closely meshed net work around each
  myofibril
• H-zone longitudinal tubules converge
  Fenestrated collar
• Jxn of the A and I bands longitudinal tubules
  converge with terminal cisternae
• A pair of terminal cisternae lie parallel to one
  another one traversing the I band the other the
  adjacent A band

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• Sarcoplasmic Reticulum Intracellular membrane
• Sytem of tubules and cisternae (reservoirs for
  calcium stores)
• Forms a closely meshed net work around each
  myofibril
• H-zone longitudinal tubules converge
  Fenestrated collar
• Jxn of the A and I bands longitudinal tubules
  converge with terminal cisternae
• A pair of terminal cisternae lie parrallel to one
  another one traversing the I band the other the
  adjacent A band
• A T-tubule also runs adjacent to the A-I band jxn

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• Sarcoplasmic Reticulum Intracellular membrane
• Sytem of tubules and cisternae (reservoirs for
  calcium stores)
• Forms a closely meshed net work around each
  myofibril
• H-zone longitudinal tubules converge
  Fenestrated collar
• Jxn of the A and I bands longitudinal tubules
  converge with terminal cisternae
• A pair of terminal cisternae lie parrallel to one
  another one traversing the I band the other the
  adjacent A band
• A T-tubule also runs adjacent to the A-I band jxn
• T-tubules sarcolemma
• This sarco-tubular system encircles each
  myofibril at the A-I band jxn of mammals, birds,
  and some fish
• Some species located at the z-disk

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• Mitochondria
• Oblong organelles
• Powerhouse of the cell
• Capture energy from carbo, lipid and protein
  metabolism and then provide the cell with
  chemical energy
• Lysosomes
• Small vesicles located in the sarcoplasm
• Cathepsins digest cell
• Golgi-Complex
• Sarcoplasm located near the nuclei
• Multinucleated so many golgi

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• Epithelial Cells
• Covers the surface of the body and organs
• Along with connective tissue contributes to
  crispness of fried chicken
• Nervous Tissue
• Peripheral or Central Nervous System
• Neuron comprises bulk of NT
• Polyhedral shaped body
• Nucleus in neuron body
• Long stxr axon
• Dendrites radiate from cell body
• Synapse is interdigitating dendrites
• Motor end plate deliver signal to muscle

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• Connective Tissue
• Binds everything together
• Acts as a barrier for the body
• Critically important in wound healing
• Varying densities Bone Cartlidge Adipose
  Tissue - blood
• Connective Tissue Proper
• Found in muscle Fiborus
• Ground substance stxrless mass called ground
  substance embedded cells extracellular fibers
• Extracellular Fibers
• Collagen
• Elastin

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• Collagen - most abundant protein
• Significantly affects meat tenderness
• 20 25 Total Body Protein
• Principle Structural Protein
• The older the animal the more insoluble it
  becomes?

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• Muscle Fiber Types
• Red and White
• Most muscles contain both
• Higher proportion of white in all muscles even
  though muscle is visibly red.

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