Muscle is one of the four basic tissues of the body. There are three main types of muscle: skeletal muscle which is voluntary and controls movement, cardiac muscle which is involuntary and found only in the heart, and smooth muscle which is involuntary and found in organs and blood vessels. Muscles are attached to bones via tendons and contract when stimulated by nerves to cause movement. The microscopic structure of muscles allows them to shorten through interactions between thin actin and thick myosin filaments.

1. Muscles
VTT 235 Anatomy & Physiology

2. Muscle…
 Muscle is one of the four basic tissues of
the body.
 It is made up of cells that can shorten or
contract.
 Skeletal muscle is voluntary and is
responsible for movement of the bones.
 Cardiac muscle is involuntary and is found
only in the heart.
 Smooth muscle is involuntary and is found
all over the body including blood vessels,
the bladder, and the intestines.

3. SKELETAL MUSCLE

4. Muscle Attachments
 Most muscles are attached to bones
at both ends by tendons.
 A few muscles are attached to bones
or to other muscles by aponeuroses.
 The most prominent aponeurosis is the
linea alba.

5. Muscle Attachments…
 Origin:
 Site of muscle attachment that is more
stable.
 The origin has the least amount of
movement during muscle contraction.
 Insertion:
 The site of muscle attachment that
undergoes the most movement during
contraction.

6. Muscle Actions
 When stimulated by a nerve impulse,
a muscle contracts.
 It shortens by pulling on its attachment
sites to produce movement.
 A prime mover (agonist) is a muscle
that produces a desired movement.
 An antagonist opposes the action of a
prime mover.

7. Muscle Actions…
 A synergist is a muscle that contracts
at the same time as a prime mover
and assists it in carrying out its
action.
 Fixator muscles stabilize joints to
allow other movements to take place.

8. Muscle Names
 Muscles are often named for physical
characteristics such as:
 Action- names can be related to a
muscles function (flexors).
 Shape
 Location
 Direction of fibers
 Number or heads or divisions
 Attachment sites

9. Microscopic Anatomy of Skeletal
Muscle
 Skeletal muscle cells are huge.
 They are not very wide, but they are
very long and thin.
 They are usually referred to as skeletal
muscle fibers because of their length.
 They have many nuclei located just
beneath the sarcolemma (muscle cell
membrane).

10. Microscopic Anatomy of Skeletal
Muscle…
 Most of the volume of skeletal muscle
fiber is made up of thousands of myofibrils
packed together lengthwise.
 Myofibrils are composed of thousands of even
tinier contractile protein filaments.
 The two primary proteins that make up the
filaments are:
 Thin actin filaments.
 Thick myosin filaments.

11. Skeletal Muscle Contraction
 When a muscle fiber is relaxed, the actin
and myosin filaments overlap a little.
 When a muscle is stimulated to contract,
small levers on the myosin filaments called
cross bridges, ratchet back and forth and
pull the actin filaments on either side of
the myosin filaments towards the center of
the myosin filaments.
 This causes the filaments to slide over
each other and shorten the sarcomere.

12. Myosin
Actin

13. Skeletal Muscle Contraction…
 Muscle fibers store glucose as glycogen
and oxygen as myoglobin.
 Muscles utilize aerobic metabolism as long
as the oxygen supply is adequate to keep up
with the energy needs of the fiber.
 The maximum amount of energy is extracted
from each glucose molecule.

14. Skeletal Muscle Contraction…
 When the oxygen runs out, muscles switch
to anaerobic metabolism.
 Its not as efficient.
 Results in lactic acid formation as a byproduct
of incomplete glucose breakdown.
 Lactic acid accumulates in muscles and makes
them sore.
 It diffuses back into the blood and goes to the
liver, where it is converted back into glucose.

15. Heat Production
 A considerable amount of energy
from muscles is produced in the form
of heat.
 Under cold conditions, muscles can
produce heat by shivering.

16. CARDIAC MUSCLE

17. Gross Anatomy
 Forms most of the volume of the
heart & makes up the majority of the
walls of the cardiac chambers.
 Cardiac muscle cells form elaborate
networks around the cardiac
chambers.

18. Microscopic Anatomy
 Cardiac muscle cells are much smaller than
skeletal muscle cells.
 They only have one nucleus per cell.
 They are longer then they are wide and
often have multiple branches.
 The firm end-to-end attachments between
cardiac muscle cells are visible under the
microscope as dark, transverse lines
between cells (fig. 7-1).

19. Microscopic Anatomy…
 These attachment sites are called
interclated disks.
 The interclated disks securely fasten
the cells together & also transmit
impulses from cell to cell to allow large
groups of cells to contract in a
coordinated manner.

20. Physiology…
 Rather than large numbers of muscle cells
contracting at the same time, as in skeletal
muscle, cardiac muscle cells contract in a
rapid, wavelike fashion.
 The impulse that coordinates the
contractions spreads from cell to cell
across the interclated disks like a wave.
 That rapid, wavelike contraction
effectively squeezes blood out of the
cardiac chambers.

21. Physiology…
 For blood to move through the chambers of
the heart, these contractions must be
carefully initiated and controlled.
 That is the job of the heart’s internal
impulse conduction system.
 This system consists entirely of cardiac muscle
cells.
 The impulse that starts each heartbeat begins
in the heart’s “pacemaker” the SA node.

22. SMOOTH MUSCLE

23. Gross Anatomy
 Smooth muscle is found all over the
body in two main forms:
 As large sheets in the walls of some
hollow organs called visceral smooth
muscle.
 As small, discrete groups of cells called
multiunit smooth muscle.

24. Microscopic Anatomy
 Smooth muscle cells are small and spindle shaped
with a single nucleus center.
 Because their contractile units are not organized
into regular, parallel sarcomeres, individual smooth
muscle cells can shorten to a greater extent than
the other types of muscle cells.

25. Physiology- Visceral Smooth Muscle
 Visceral smooth muscle is found in the walls
of many soft internal organs.
 Contractions occur in large, rhythmic
waves.
 These contractions can be very strong for
example:
 Peristaltic contractions
 Uterine contractions

26. Physiology- Multiunit Smooth Muscle
 Multiunit smooth muscle is small and
delicate.
 It is found where delicate
contractions are needed:
 Iris & ciliary body of the eye.
 Walls of small blood vessels.
 Air passages in the lungs.

27. SELECTED SKELETAL
MUSCLES
Muscles you will need to identify
for your lab practical

28. Muscles of the Face
 Masseter- closes
the jaw

29. Thoracic Limb Muscles
 Extrinsic Shoulder-
1. Trapezius- elevates
the scapula.
2. **Latissimus dorsi-
flexes the shoulder.
3. **Brachiocephalicus-
advances the limb or
draws the head
laterally.

30. Thoracic Limb Muscles
 Extrinsic Shoulder-
4. Serratus ventralis-
supports the trunk.
5. Superficial pectoral-
adducts and advances
the limb.
6. Deep pectoral- draws
the limb caudally
(flexes the shoulder).

31. Thoracic Limb Muscles
 Intrinsic shoulder-
7. Deltoid- flexes the
shoulder.
8. Brachialis- flexes the
elbow.

32. Thoracic Limb Muscles
 Intrinsic shoulder-
9. Biceps brachii-
extends the shoulder
and flexes the elbow.
10. **Triceps brachii-
extends the elbow, the
long head flexes the
shoulder.

33. Forearm Muscles
 11.) Extensors-
 A-Extensor Carpi
Radialis- extends the
carpus, flexes the
elbow.
 B- Common Digital
Extensor- extends
the digits & carpus.
 C- Lateral Digital
Extensor- extends
the digits & carpus.
 D- Extensor Carpi
Ulnaris- flexes the
carpus.

34. Thoracic Limb Muscles
 12.) Flexors-
 A- Flexor Carpi
Radialis- flexes the
carpus.
 B- Flexor Carpi
Ulnaris- flexes the
carpus.
 C- Superficial Digital
Flexor- flexes the
carpus & digits.
 D- Deep Digital
Flexor- flexes the
carpus & digits.

36. Thorax Muscles
 Intercostals- involved in respiration
 Diaphragm- separates the thoracic
and abdominal cavities, main muscle of
respiration.

37. Trunk Muscles
 13. Epaxials-
 Lies above the
vertebral column.
 supports the spine.
 14. Hypaxials-
 Lies below the
vertebral column.
 They flex the neck &
tail contributes to the
flexion of the
vertebral coloumn.

38. Pelvic Limb Muscles
 15.) **Superficial
Gluteal- abducts the
limb.
 Middle Gluteal-
Extends the thigh.
 Deep Gluteal-
extends the limb.

39. Pelvic Limb Muscles
 Hamstring Group-
extends the hip, stifle, &
tarsus, flexes the stifle.
 All originate from the
ischiatic tuberosity,
 16.) Biceps femoris-
 Inserts into the patella.
 17.) **Semitendinosus-
 Inserts into the tibia.
 18.) **Semimembranosus-
 Inserts into the femur &
tibia.

42. Pelvic Limb Muscles
 19.) **Gracialis-
 Originates in the
pelvic symphysis.
 Inserts into the
medial side of the
stifle.
 Adducts the limb.
 20.) **Sartorius-
 Originates in the ilium.
 Inserts into the
medial side of the
stifle.
 Flexes the hip & stifle.

43. Pelvic Limb Muscles
 21.) Quadriceps femoris-
 Rectus femoris-
 Originates in the ilium.
 Inserts into the patella.
 Flexes the hip, extends the
stifle.
 Vastus: lateralis,
medialis, intermedius-
 Originates in the proximal
femur.
 Inserts into the patella.
 Extends the stifle.

44. Pelvic Limb Muscles
 22.) Adductor-
 Originates in the ventral
surface of the hip bones.
 Inserts into the femur.
 Adducts the limb.
 23.) **Gastrocnemius-
 Originates in the caudal
surface of the femur.
 Inserts into the
calcanean tuberosity.
 Extends the tarsus,
flexes the stifle.

45. Abdominal Muscles
 24.) Obliques:
 External- extends from the ribs to the ventral
midline.
 Internal- muscle fibers run obliquely and cross with
the external oblique.
 25.) Transversus abdominus- the deepest
abdominal muscle terminating at the linea alba.
 26.) Rectus abdominus- two long, straight
muscles extending from the sternum along the
ventral abdomen.
 27.) **Linea Alba- the fibrous cord formed by
the joining of the abdominal muscles.

47. THE END