2. The Structural and Functional
Organization of Muscles
• About 600 human skeletal muscles
• Constitute about half of our body weight
• Three kinds of muscle tissue
– Skeletal, cardiac, smooth
• Specialized for one major purpose
– Converting the chemical energy in ATP into the mechanical
energy of motion
• Myology—the study of the muscular system
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3. The Functions of Muscles
• Movement
– Move from place to place, movement of body parts and
body contents in breathing, circulation, feeding and
digestion, defecation, urination, and childbirth
– Role in communication: speech, writing, nonverbal
communications
• Stability
– Maintain posture by preventing unwanted movements
– Antigravity muscles: resist pull of gravity and prevent us
from falling or slumping over
– Stabilize joints
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4. The Functions of Muscles
• Control of openings and passageways
– Sphincters: internal muscular rings that control the
movement of food, bile, blood, and other materials within
the body
• Heat production by skeletal muscles
– As much as 85% of our body heat
• Glycemic control
– Regulation of blood glucose concentrations within its normal
range
10-4
6. Connective Tissues and Fascicles
• Endomysium
– Thin sleeve of loose connective tissue surrounding each muscle
fiber
– Allows room for capillaries and nerve fibers to reach each
muscle fiber
– Provides extracellular chemical environment for the muscle
fiber and its associated nerve ending
• Perimysium
– Slightly thicker layer of connective tissue
– Fascicles: bundles of muscle fibers wrapped in perimysium
– Carry larger nerves and blood vessels, and stretch receptors
10-6
7. Connective Tissues and Fascicles
• Epimysium
– Fibrous sheath surrounding the entire muscle
– Outer surface grades into the fascia
– Inner surface sends projections between fascicles to form
perimysium
• Fascia
– Sheet of connective tissue that separates neighboring muscles
or muscle groups from each other and the subcutaneous tissue
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10. Muscle Attachments
• Indirect attachment to bone
– Tendons bridge the gap between muscle ends and bony
attachment
• Collagen fibers of the endo-, peri-, and epimysium continue
into the tendon
• From there into the periosteum and the matrix of bone
• Very strong structural continuity from muscle to bone
• Biceps brachii, Achilles tendon
• Aponeurosis—tendon is a broad, flat sheet (palmar
aponeurosis)
• Retinaculum—connective tissue band that tendons from
separate muscles pass under
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13. Muscle Origin and Insertions
• Also can be determined by proximal or distal or
superior and inferior attachments, especially on
limbs (nontraditional)
• Some muscles insert not on bone but on the fascia or
tendon of another muscle or on collagen fibers of
the dermis
– Distal tendon of the biceps brachii inserts on the fascia of
the forearm
– Facial muscles insert in the skin
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14. Functional Groups of Muscles
• Action—the effects produced by a muscle
– To produce or prevent movement
• Four categories depending on action
– Prime mover (agonist)
• Muscle that produces most of force during a joint action
– Synergist: muscle that aids the prime mover
• Stabilizes the nearby joint
• Modifies the direction of movement
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15. Functional Groups of Muscles
Cont.
– Antagonist: opposes the prime mover
• Relaxes to give prime mover control over an action
• Preventing excessive movement and injury
• Antagonistic pairs—muscles that act on opposite sides of a
joint
– Fixator: muscle that prevents movement of bone
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18. Muscle Innervation
• Innervation of a muscle—refers to the identity of the
nerve that stimulates it
– Enables the diagnosis of nerve, spinal cord, and brainstem
injuries from their effects on muscle function
• Spinal nerves arise from the spinal cord
– Emerge through intervertebral foramina
– Immediately branch into a posterior and anterior ramus
– Innervate muscles below the neck
– Plexus: weblike network of spinal nerves adjacent to the
vertebral column
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19. Neuromuscular Junction
High Magnification
Skeletal muscle fiber Axon of motor nerve Motor end plate
20. Muscle Innervation
• Cranial nerves arise from the base of the brain
– Emerge through skull foramina
– Innervate the muscles of the head and neck
– Numbered CN I to CN XII
10-20
21. Blood Supply
• Muscular system receives about 1.24 L of blood per
minute at rest (one-quarter of the blood pumped by
the heart)
• During heavy exercise total cardiac output rises and
the muscular system’s share is more than three-
quarters (11.6 L/min)
• Capillaries branch extensively through the
endomysium to reach every muscle fiber
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23. The Human Muscular System
Please view the photographs of the human muscular system in
the slides beyond this point. Look for muscles you have
identified in the cat. Compare the anatomy of the human with
the anatomy of the cat. Think about how they compare. How
are they the same? How are they different? What is the
reason for these differences?
You will not be tested on the photographs.
158. Muscles Acting on the
Knee
Posterior (flexor)
Hamstring
Compartment Group
Long head of Semimembranosus
Biceps femoris m. m.
Semitendinosus m. Short head of Biceps
femoris m.
159. Muscles Acting on the Knee
Posterior (flexor) Compartment
Biceps
Semitendinosus Semimembranosus
femoris
short long
head head
160. Muscles Acting on the Knee
Posterior (flexor) Compartment
Biceps
insertion
femoris
origin long
short
head head
161. Muscles Acting on the Knee
Posterior (flexor) Compartment
Semimembranosus insertion
origin
162. Muscles Acting on the Knee
Posterior (flexor) Compartment
Semitendinosus insertion
origin
163. Muscles Acting on the Knee
Posterior (flexor) Compartment
insertion
Popliteus
164. Muscles Acting on the Foot
Anterior Compartment
origin
Extensor
digitorum
longus
insertion
165. Muscles Acting on the Foot
Anterior Compartment
origin
Extensor
hallicus insertion
longus
166. Muscles Acting on the Foot
Anterior Compartment
tendon
origin
Tibialis anterior
insertion
167. Muscles Acting on the Foot
Posterior Compartment – sup.
Gastrocnemius
origins
medial lateral
head head
Achilles
tendon
insertion
168. Muscles Acting on the Foot
Posterior Compartment – sup.
origin
Soleus
Achilles
tendon
insertion
169. Muscles Acting on the Foot
Posterior Compartment – sup.
Plantaris
insertion
Calcaneus origin
170. Muscles Acting on the Foot
Posterior Compartment – deep
Flexor origin
digitorum
longus
insertion
tendon
tendon
171. Muscles Acting on the Foot
Posterior Compartment – deep
origin
Tibialis
insertion
posterior
tendon
172. Muscles Acting on the Foot
Lateral (fibular) Compartment
origin
Fibularis
(peroneus)
longus & tendon
insertion
brevis
173. Intrinsic Muscles of the Foot
Dorsal Aspect
Extensor digitorum brevis
origin insertion
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174. Intrinsic Muscles of the Foot
Ventral Layer 1 – most superficial
Flexor digitorum brevis
origin insertion
10-174
175. Intrinsic Muscles of the Foot
Ventral Layer 1 – most superficial
Abductor digiti minimi
origin insertion
10-175
176. Intrinsic Muscles of the Foot
Ventral Layer 1 – most superficial
Abductor hallucis
origin insertion
10-176
177. Intrinsic Muscles of the Foot
Ventral Layer 2
Quadratus plantae
origin insertion
10-177