introduction to muscle anatomy

8/10/2019 Introduction to Muscle Anatomy

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Introduction to

Muscle Anatomy


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Types of Muscle

1. Skeletal Elongated Cells

Multi nucleated

Striatedstriped

appearance Voluntary

Produces powerfulcontractions

Tires easily, needs rest(fatigue).

Covers bony skeleton(motility)

Cross Section

Notice nuclei

around outside

of cell.

Longitudinal

View

Notice striations

and nuclei

around outsideof cell.


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Skeletal Muscle Composite Sketch


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2. Smooth

Spindle-shaped Cell Single nucleus in each

cell

No Striations

Involuntary

Slow, sustained

contractions

In hollow visceralorgans (stomach,

bladder, respiratory

passages)

Cross Section

Nucleus is in center

of cell. Cells much

smaller.


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Smooth Muscle Composite Sketch


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3. Cardiac (Heart)

Branched cell Contain intercalated

discs

Single nucleus in eachcell

Striations

Involuntary

Steady, constantcontractions

Never tires


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Cardiac Muscle Composite Sketch


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Muscle Functions Produce movement

locomotion & manipulation

Help blood move through veins & food

thru small intestines Maintain posture

Stabilize joints

Body temp homeostasis

Shivering: movement produces heat

energy


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Muscle Attachments

Most muscles span joints Attaches to bone in two places: (video)

1.Insertion: the moveable bone Bicep insertion is the radius

2.Origin: the stationary bone bicep originates in two different places in scapula

Attachment types

1. Direct: attaches right onto bone- ex. intercostal muscles of ribs

2. Indirect: via tendon or aponeurosis (sheet-liketendon) to connect to bone

- leaves bone markings such as tubercle
http://www.youtube.com/watch?v=6pK5wYIXTrchttp://www.youtube.com/watch?v=6pK5wYIXTrc


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Muscle Organization

Muscles are complex bundledstructures: fibers within fibers


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Muscle

organization

Muscle

(organ)

Fascicle

Muscle fiber (cell)

Myofibril

Sarcomere

Myofilaments:

Actin & Myosin


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Muscle Fibers

A Muscle Fiber = Muscle Cell HUGE cell:

10 - 100m in diameter can be hundreds of centimeters long (created by cytoplasmic

fusion of multiple embryonic cells)

extends the length of the muscle

Main content: bundles of proteins (actin

and myosin) Multinucleated

to maintain high rate of protein synthesis.

Muscle fiber nucleus = myonucleus


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Insulation of Muscles

Muscle cells must be insulated

from one another by specialized

membranes Muscle cells work electrically

if not insulated, nerves cannotcontrol individual muscles.


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myofibril

sarcolemma

T-tubule

Sarcoplasmic

Reticulum

Myosin (red) and

Actin (blue)


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Microstructures

Each muscle fiber (muscle cell), iscomposed of many myofibrils.

Organized system of cytoskeleton filaments of

actin and myosin proteins that do the actualcontracting

Myofibrils are NOT CELLS

A sarcomere is one segment of a myofibril

(muscle segments). The series of sarcomeres produce the striated

appearance of muscles


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Muscle Fiber

Sarcomere


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Sarcomere organization

Myofibril composed of repeating series of

sarcomeres with dark A and light I bands.

I bands intersected by Z discs mark the

outer edges of each sarcomere.

Contraction happens within one

sarcomere.


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Sarcomere Banding Pattern


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Lets sketch the sarcomere

together and discuss thesliding filament model of

muscle contraction

How do muscle contract?

introduction to muscle anatomy

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