Eric Harwell
Growth and Development
ANSC 590
Fall 2008
 Serves several purposes:
 Basis of all movement of the body.
 Examples:
 Locomotion
 Digestion
 Vision
 Circulation
 And many other biological activities
 These are accomplished by the ability of muscle to
contract and relax.
 In the body, two vital functions include:
 Conversion of chemical energy into mechanical.
 (not very efficient, ≥75% lost as heat)
 Maintenance of body temperature.
 Other functions of muscle in the body include:
 Communication
 via voice related structures
 Various body gestures and movements
 Muscle is converted to meat.
 Excellent source of protein and many other nutrients
 In developing countries, meat animals contribute
significantly to the quality of the human diet.
 Optimizing muscle growth for meat production is a major
goal of the meat industry.
 Although many other animal tissues are used for
consumption, skeletal muscle is the most significant
component of animal production.
 Three types
 Classified by their microstructure and means in which they
are stimulated.
 Tissues contain unique set of proteins capable of interacting
by sliding past each other (contraction)
 Smooth, Involuntary
 Arteries, veins, gastrointestinal tract
 Striated, Involuntary
 Cardiac muscle
 Striated, Voluntary
 Skeletal muscle
 Skeletal Muscle
 Cardiac Muscle
 Smooth Muscle
 Many shapes and sizes
 Examples:
 Semimembranosus is one of the largest muscles in the
animal.
 Lower leg flexor muscles are 10,000 times lighter than
semimembranosus.
 Semitendonosis muscle is long cylindrical muscle.
 Massater muscle in jaw is circular shape.
 Large cells bundled together in large network of
connective tissue.
 Merge with each other to transmit greater contractile
force to provide movement.
 Connective Tissue:
 Basis of all structural integrity of muscles.
 Several layers :
 Epimysium: outer most layer of connective tissue.
 Seperates muscles into distinct units.
 Provides avenues for nerves and blood vessels to enter/exit
muscles.
 Connective Tissue:
 Perimysium: contain a number of smaller muscle fiber
bundles.
 Several bundles encased within the epimysium layer.
 **intramuscular fat, marbling, is deposited between these
bundles.
 Connective Tissue:
 Endomysium: surrounds muscle fibers within each
perymisial bundle.
 Considered the major component of meat tenderness and
changes with age.
 Lies adjacent to the muscle cell membrane.
 Encased in the endomysium layer.
 Multinucleated fiber is the basic cellular structure of
muscle or meat.
 May extend the entire or partial length of the muscle.
 Cell Membrane
 Sarcolemma
 Similar functions to other cell membranes of other cell types.
 Unique to sarcolemma:
 Small invaginations spaced along surface of the cell which act as
communication channels.
 The “inner making” of the skeletal muscle cell.
 Unique microfilamentous organelles of muscle fibers.
 Highly organized structures running entire length of
the cell.
 Bathed in cytoplasm, which is rich in protein.
 Muscle cells contain 1,000-2,000 myofibrils.
 Smallest contractile unit of the muscle.
 Repeated structure represents the organization of
myofibrils.
 made of many proteins
 that are directly involved in contraction.
 that regulate interactions of filaments
 that are required to stabalize the lattice work structure
of the cell.
 A sarcomere is measure from Z-line to Z- line and
mark the boundary or adjacent sarcomeres. ~~ 10,000
sarcomeres make up a myofibril.
 Aligned across entire muscle fiber, altering light and
dark banding patterns are readily apparent
microscopically.
 Straited appearance is the hallmark of skeletal and
cardiac muscle.
 Length of sarcomere is related to tenderness
 Shorter= greater overlap of thick and thin filaments=
tougher meat.
 Longer= less overlap of thick and thin filaments= tender
meat.
 Illustrated Structure of a sarcomere:
 A- Band: Dense area in the middle, where thick
filaments are located.
 H- Zone: small area within the A-band where thin
filaments terminate from each half of the sarcomere,
and only thick filaments are present.
 I- Band: consists of Z-line and thin filaments from
adjacent sarcomeres.
 Shortens during contraction as a result of sliding filaments.
 Actin and myosin
 Myosin:
 Most abundant contractile protein.
 Occupies 80-87% of volume of muscle fibers.
 Is the “real” power component of muscle contraction because
its unique structure allows it to pull actin filaments together.
 Actin:
 Second most abundant contractile protein.
 Consists of nearly 20% of total myofibrillar protein.
 broken down is made of G-actin and F-actin.
 binds to myosin to form actomyosin and contract.
ACTIN
MYOSIN