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Introduction to Muscle Anatomy

Types of Muscle 1. Skeletal

–  Elongated Cells –  Multi nucleated –  Striated – striped

appearance –  Voluntary –  Produces powerful

contractions –  Tires easily, needs rest

(fatigue). –  Covers bony skeleton

(motility) Cross Section

Notice nuclei around outside of cell.

Longitudinal View

Notice striations and nuclei around outside of cell.

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 visceral

organs (stomach, bladder, respiratory passages)

Cross Section Nucleus is in center of cell. Cells much smaller.

Smooth Muscle Composite Sketch

3. Cardiac (Heart) – Branched cell – Contain intercalated

discs – Single nucleus in each

cell – Striations –  Involuntary – Steady, constant

contractions – Never tires

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Cardiac Muscle Composite Sketch

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

Muscle Requirements

•  Demands continuous oxygen/nutrient supply. – Lots of arteries/capillaries to muscle.

•  Each muscle cell w/ its own nerve ending controlling its activity.

•  Produce much metabolic waste due to constant activity.

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Muscle Requirements

•  Demands continuous oxygen/nutrient supply. – Lots of arteries/capillaries to muscle.

•  Each muscle cell w/ its own nerve ending controlling its activity.

•  Produce much metabolic waste due to constant activity.

Motor end plate (terminus)

Axon of neuron

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

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Muscle Attachments •  Attachment types

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

Muscle Attachments •  Attachment types

1.  2.  Indirect: via tendon or aponeurosis (sheet-like

tendon) to connect to bone -  leaves bone markings such as tubercle

Agonist vs. Antagonist

•  If you do a bicep curl, how do you re-straighten your arm?

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