Anatomy of the Anatomy of the Muscular SystemMuscular System

A Few Facts…A Few Facts…

There are more than 600 skeletal muscles There are more than 600 skeletal muscles in the bodyin the body

They constitute 40-50% of our body weightThey constitute 40-50% of our body weight

Along with the skeleton they determine the Along with the skeleton they determine the form and contours of our bodyform and contours of our body

Skeletal Muscle Skeletal Muscle StructureStructure

Connective Tissue ComponentsConnective Tissue ComponentsMuscles cells (fibers) are covered by a Muscles cells (fibers) are covered by a delicate connective tissue membrane delicate connective tissue membrane called the called the endomysiumendomysium..

Groups of skeletal muscle fibers are called Groups of skeletal muscle fibers are called fascicles, and bound together by a tougher fascicles, and bound together by a tougher connective tissue envelope called the connective tissue envelope called the perimysiumperimysium..

The muscle as a whole is covered by a The muscle as a whole is covered by a course sheath called the course sheath called the epimysiumepimysium..

Skeletal Muscle StructureSkeletal Muscle Structure

Tendon – bands or cords of fibrous Tendon – bands or cords of fibrous connective tissue that attach a muscle to a connective tissue that attach a muscle to a bone or other structure bone or other structure

Aponeurosis – broad, flat sheet of Aponeurosis – broad, flat sheet of connective tissue connective tissue

Fascia – surrounds the muscle organ and Fascia – surrounds the muscle organ and outside the epimysium outside the epimysium Superficial Superficial Deep Deep

Size, Shape, and Fiber Size, Shape, and Fiber ArrangementArrangement

Skeletal muscles are organsSkeletal muscles are organs

Vary widely in size and shapeVary widely in size and shape

Muscle fiber arrangement differsMuscle fiber arrangement differs Parallel to the long axis of the muscleParallel to the long axis of the muscle Converge to a narrow attachmentConverge to a narrow attachment Oblique and pennate (like a feather pen)Oblique and pennate (like a feather pen) Bipennate (double-feathered)Bipennate (double-feathered) Curved -- sphincterCurved -- sphincter

Fiber ArrangementFiber Arrangement

A.A. Parallel Parallel

B.B. ConvergentConvergent

C.C. PennatePennate

D.D. Bipennate Bipennate

E.E. SphincterSphincter

Attachment of Skeletal MuscleAttachment of Skeletal MuscleMost muscles span at least one joint and Most muscles span at least one joint and attach to both articulating bones attach to both articulating bones

Origin – attachment of a muscle to the Origin – attachment of a muscle to the bone, which does not move when bone, which does not move when contraction occurscontraction occurs

Insertion – attachment of a muscle to the Insertion – attachment of a muscle to the bone that it moves when conctraction bone that it moves when conctraction occurs occurs

Muscle AttachmentMuscle Attachment

Muscle Actions Muscle Actions Most muscles act in groups and not alone—Most muscles act in groups and not alone—some contract while others relaxsome contract while others relax

Agonist (prime mover) – used to describe a Agonist (prime mover) – used to describe a muscle or group of muscles that directly muscle or group of muscles that directly performs a specific movement. Example: performs a specific movement. Example: biceps brachii is the prime mover in the flexion of biceps brachii is the prime mover in the flexion of the forearm.the forearm.

Antagonists – muscles that, when contracting, Antagonists – muscles that, when contracting, directly oppose prime movers – they relax while directly oppose prime movers – they relax while the prime mover is contractingthe prime mover is contracting

Synergists – muscles that contract at the same Synergists – muscles that contract at the same time as the prime movertime as the prime mover

Fixator muscles – generally function as joint Fixator muscles – generally function as joint stabilizersstabilizers

Most muscles function not only as prime movers Most muscles function not only as prime movers but also as antagonists, synergists, and fixators. but also as antagonists, synergists, and fixators. A prime mover in a particular movement , such A prime mover in a particular movement , such as flexion, may be an antagonist during as flexion, may be an antagonist during extensionextension

Lever SystemsLever Systems

A lever is any rigid bar free to turn about a A lever is any rigid bar free to turn about a fixed point called its fulcrum.fixed point called its fulcrum.

Bones serve as levers and joints serve as Bones serve as levers and joints serve as fulcrumsfulcrums

First Class Lever First Class Lever

Second Class LeverSecond Class Lever

Third Class LeverThird Class Lever

How Muscles are NamedHow Muscles are Named

Most are Latin in origin (some Greek)Most are Latin in origin (some Greek)

Location (Location (gluteusgluteus = buttock) = buttock)

Function (Function (adductoradductor))

Shape (Shape (deltoiddeltoid = triangular) = triangular)

Muscle Naming Continued…Muscle Naming Continued…

Direction of fibers (Direction of fibers (rectusrectus = straight) = straight)

Number of heads of divisions (Number of heads of divisions (bicepsbiceps = two = two points of origin)points of origin)

Points of attachment (Points of attachment (sternocleidomastoidsternocleidomastoid = = origin on the sternum and clavicle and inserts on origin on the sternum and clavicle and inserts on the mastoid process)the mastoid process)

Size of muscle (maximus = largest)Size of muscle (maximus = largest)