Download Muscle Fiber

Muscle Anatomy
Outer part of skeletal muscle:
• Tendon:
– At the end of muscle
fibers.
– Attach the muscle to the
bone.
• Fascia:
– Dense connective tissue
covering entire muscle.
– Fascia is a continuation of
the tendon.
Muscle
Bone
Tendon
Fascia
(covering muscle)
The various bundles of muscle:
• Each muscle is made of
individual bundles of muscle
sections.
– This is in order from the
smallest section to the largest.
Muscle
Fascicles
• Myofibrils:
– Contractile fibers within muscle
cells.
– Play a fundamental role in the
muscle contraction mechanism.
Muscle fibers (cells)
Myofibrils
• Muscle Fiber:
– Several Myofibrils bundled
together.
Fascicle
Myofibril
• Fascicles:
– Several Muscle Fibers bundled
together.
– Every muscle in the body is
made up of several fascicles
bundled together.
Muscle fiber
Layers of connective tissue:
• Epimysium:
– Most superficial layer of
connective tissue.
– Surrounds all of the fascicles
(or the entire muscle).
– Located under fascia.
Muscle
Fascicles
Muscle fibers (cells)
• Perimysium:
Myofibrils
Epimysium
– Middle layer of connective
tissue.
– Surrounds each fascicle (or
several muscle fibers).
Perimysium
• Endomysium:
– Deepest layer of connective
tissue.
– Surround each muscle fiber (or
several myofibrils).
Endomysium
Muscles Fibers are Cells!!!
• Muscles are made of cells.
• The Muscle Fibers section of
a muscle are the cells.
– This is one of the 260 different
types of specialized cells.
Nucleus
• Thus they have the same
properties as cells.
• Sarcoplasm:
– Another term for cytoplasm
inside muscle cells.
• Contains nuclei and
mitochondria.
• As you can see, muscles
have A LOT of mitochondria.
Why?
– NEED ATP!!!
Mitochondria
Sarcoplasm
Anatomy of Muscle Fibers (cells):
• Sarcolemma:
– Cell membrane
surrounding several
myofibrils.
Muscle
Fascicles
Muscle fibers (cells)
• Sarcoplasmic Reticulum:
Myofibrils
– Membranous network of
channels and tubules with
muscle fiber.
• Myofibrils:
– Contractile units.
Sarcoplasmic
reticulum
Muscle fiber
Sarcolemma
Myofibril
Sarcoplasmic Reticulum:
• Transverse tubules (T-tubules):
– Membranous channel that extends inward.
• Cisterna:
– Enlarged portion of the sarcoplasmic reticulum.
• Triad = Three structures: T-tubules and Cisterna
Cisterna
Triad
Transverse
tubule
Sarcoplasmic
reticulum
Openings into
transverse tubules
Anatomy of Myofibrils:
• Sarcomeres (very important!!!)
– Structural and functional unit of a myofibril, where the
contraction actually happens.
– Myofibrils are actually sarcomeres joined end to end.
Sarcoplasmic Reticulum
Myofibril
Sarcomere
Muscle Structure Flowchart:
Muscle
Surrounded by Fascia
Surrounded by Epimysium (deep to Fascia)
Fascicles
Each one is surrounded by Perimysium
Muscle Fibers (a.k.a. muscle cells)
Each one is surrounded by Endomysium
Myofibrils
Sarcomeres (contractile units, IMPORTANT)
Muscle Fibers (a.k.a. muscle
cells) Flowchart:
Muscle Fibers (a.k.a. muscle cells)
Each one is surrounded by Endomysium
Sarcolemma
(cell membrane)
Sarcoplasm
(cytoplasm)
Nuclei
Mitochondria
(has a lot to make
a lot of ATP)
Sarcoplasmic Reticulum
(houses calcium)
Myofibrils
Key: Sarcomeres make up myofibrils
The sarcomere is the contractile unit.
Very important!!!