6. • Skeletal muscles have muscular & tendinous
portions:
• Muscle - consists of skeletal muscle cells
(which, in turn, consist of myofibrils and
myofilaments)
• Tendons - extensions of a muscle's tough
connective tissue sheath (fascia & epimysium)
that anchor a muscle to its origin & insertion
7.
8. –Origin = site of attachment that is
relatively fixed
–Insertion = site of attachment that is
normally displaced by contraction of
the muscle
9. •Names of skeletal muscles are based on:
•direction of fibers (e.g., oblique(
•location or position (e.g., superficial(
•number of divisions (e.g., triceps(
•shape (e.g., deltoid(
•origin and/or insertion (e.g., iliocostalis(
•action (e.g., levator scapulae(
•size (e.g., major(
•or some combination of these
10.
11.
12.
13. Skeletal Muscle
• Myofilaments are proteins that result in
contraction within the myofibrils
–Actin – thin & has a receptor site for myosin
–Myosin – thick & has a receptor site for
actin and ATP
–Contraction – Myosin heads attach to actin
and with ATP perform a Power Stroke
18. Key Points
• Why is the sarcomere the functional unit of
contraction?
• Why does the power stroke result in
contraction?
• What would happen to contraction if you ran
out of ATP?
19. Motor Neurons
• Skeletal muscle cannot contract without
stimulation from a motor neuron
• Motor Unit = The motor neuron plus the
myofiber(s) it innervates
20.
21. Key Points
• Why would a spinal cord injury result in
paralysis?
22. Somatic Muscles
• All of the body’s skeletal muscles except the
branchiomeric muscles
• Voluntary
• Body wall & Appendage muscles
– Trunk and Tail
– Hypobranchial
– Tongue
– Extrinsic Eyeball
27. Somatic Muscles
• Red Fibers
– More blood supply for aerobic metabolism
– Myoglobin for oxygen storage
– Fatigue resistant
– Fish for cruising long distances, tetrapods for
posture
28. Somatic Muscles
• White fibers
– Less blood supply; geared for anaerobic
metabolism
– Fatiguable
– Fish for spurts of swimming
– Tetrapods for sprints
29. Key Points
• Why is the breast meat of the goose dark, but
the breast meat of the chicken is white?
30. Cardiac Muscle
• Striated with intercalated disks
• Involuntary
• Lateral plate mesoderm (hypomere) in origin
31.
32. Smooth Muscle
• Involuntary
• Lateral plate mesoderm in origin
• Regulates internal environment
• Innervated by Autonomic Nervous System
• Found in the wall of tubes and hollow organs
• Intrinsic Eye muscles
• Erectors of feathers and hairs
33.
34. Key Points
• Besides those mentioned, give a specific
example of where might you find smooth
muscle?
35. Gross features of skeletal muscle
• Origin, insertion
• Tendon
• Aponeurosis
• Fascia
47. • Axial Muscles:
• include the skeletal muscles of the trunk & tail
• extend forward beneath the pharynx as
hypobranchial muscles & muscles of the tongue
• are present in orbits as extrinsic eyeball muscles
(check slide 27 in this powerpoint presentation)
• are metameric (most evident in fish and aquatic
amphibians where the axial muscles are used in
locomotion; in other tetrapods, metamerism is
obscured due to presence of paired appendages
responsible for locomotion on land)
• are segmental because of their embryonic origin;
arise from segmental mesodermal somites
48.
49. •Trunk & tail muscles of fish:
•Axial musculature consists of a series
of segments (myomeres) separated by
myosepta
–Myosepta serve as origins & insertions
for segmented muscles
•Myomeres are divided into dorsal &
ventral masses by a horizontal septum
that extends between the transverse
processes of the vertebrae
51. • Trunk & tail muscles of tetrapods
• Tetrapods, like fish, have epaxial & hypaxial masses, & these
retain some evidence of metamerism even in the highest
tetrapods.
• Modifications:
• 1 - epaxials are elongated bundles that extend through many
body segments & that are located below the expanded
appendicular muscles required to operate the limbs
• 2 - hypaxials of the abdomen have no myosepta & form broad
sheets of muscle
• 3 - hypaxials are oriented into oblique, rectus, & transverse
bundles
52. • Epaxials of tetrapods:
• lie along vertebral column dorsal to transverse
processes & lateral to neural arches
• extend from base of the skull to tip of the tail
53. •Hypaxials of tetrapods:
•1-Muscles of lateral body wall:
–oblique (external & internal), transverse, &
rectus muscles
•2-Muscles that form longitudinal bands
in roof of body cavity (subvertebral
muscles(
54.
55. Rectus muscles:
•weakly developed in most fish; 'stronger'
in tetrapods
•support ventral body wall & aid in arching
the back
•in mammals - rectus abdominis (typically
extends from the anterior end of the
sternum to the pelvic girdle)
56.
57. Appendicular muscles - move fins or
limbs
•Extrinsic - originate on axial skeleton or
fascia or trunk & insert on girdles or limbs
•Intrinsic - originate on girdle or proximal
skeletal elements of appendage & insert on
more distal elements
58. Branchiomeric muscles:
1 - associated with the pharyngeal
arches
2 - series of skeletal & smooth
muscles
3 - adductors, constrictors, & levators
operate jaws plus successive gill
arches
59. Integumentary muscles:
Extrinsic integumentary muscles (e.g., platysma)
•originate (usually) on the skeleton & insert on the
underside of the dermis
•striated
•move skin of amniotes
Intrinsic integumentary muscles (arrector pili muscles)
•entirely within the dermis
•found in birds & mammals
mostly smooth muscles
63. Axial Muscles – Jawed Fish
• Horizontal or Lateral Septum
• Epaxial Muscles
– From myotomes in embryology
– Innervated from dorsal rami of spinal nerves
– Extend spine & some lateral bending
– Extrinsic eye muscles (innervated by cranial
nerves)
– Epibranchial muscles
64.
65.
66. Axial Muscles – Jawed Fish
•Hypaxial Muscles
•From Myotomes
–Innervated by ventral rami of spinal nerves
–Ventroflex and lateral bending
67.
68. Hypaxial Muscles – Jawed fish
•Hypobranchial muscles
•Located on floor of pharynx, pectoral girdle to
jaw
•Are hypaxial muscles that migrated forward
•Function in respiration & feeding
•E.g. Coracomandibularis, Coracohyoid
69.
70. Axial Muscles - Tetrapods
•Epaxial trunk muscles
•Dorsal muscles from skull to tail
•Dorsalis trunci in amphibians
•Longissimus – long dominant spine extensor in
amniotes
•Iliocostalis – most lateral epaxial spine muscle
important in reptiles
84. Extrinsic Eye muscles in tetrapods
• Voluntary
• Obliques – rotates eye along its transverse
axis
• Rectus – up, down, left, right
• Retractor in some