MUSCLE TISSUE

Question 1

• Walls of the digestive tract from the middle of the esophagus to the inner anal sphincter
• Walls of the respiratory tract from the trachea to the alveolar ducts
• Walls of blood vessels
• Walls of ducts of glands
• Arrector pili muscle found in the hair bulb of skin
• Areola of mammary glands
• Subcutaneous tissue of the scrotum
• Urinary bladder
• Uterus

Answer 1

LOCATION OF SMOOTH MUSCLES

Question 2

SMOOTH MUSCLE FIBER
 3 kinds of filaments

Answer 2

thin actin, thicker myosin and intermediate filaments

Question 3

4-8 nm in diameter
o F-actin and calmodulin insert into dense bodies (contain α-actinin)

Answer 3

 thin actin filaments

Question 4

15 nm

Answer 4

o thicker myosin filaments

Question 5

10 nm, generally are
desmin

Answer 5

intermediate filaments

Question 6

 Fusiform or spindle-shaped
 Elongated nucleus situated in their widest
central portion
 Vary in their length in the different organs
(20 u – 500 u)

Answer 6

SMOOTH MUSCLE FIBER

Question 7

 Non-striated and involuntary
 Capable of slow, sustained, resistant to
fatigue contraction
 Muscle fiber is the structural and functional
unit

Answer 7

SMOOTH MUSCLE

Question 8

 Elongated and oriented parallel to its
direction of action
 Cell membrane is known as sarcolemma
 Nucleus is elongated and is parallel to the
long axis of the muscle fiber

Answer 8

GENERAL CHARACTERISTICS OF MUSCLE
FIBER

Question 9

Cytoplasm is known as sarcoplasm
 strongly acidophilic due to its myoglobin
pigment
 Contractility is its fundamental property
 contraction generates heat

Answer 9

GENERAL CHARACTERISTICS OF MUSCLE
FIBER

Question 10

 Movements
 Locomotion
 Maintenance of body posture

Answer 10

FUNCTIONS OF MUSCLES

Question 11

• under the control of the CNS

Answer 11

 Voluntary

Question 12

• contract in response to stimulation of the autonomic nervous system

Answer 12

 Involuntary

Question 13

• presence of transverse or cross-striations known as dark and light bands

Answer 13

Striated

Question 14

• no cross-striations but with longitudinal striations

Answer 14

Smooth

Question 15

 Striated and voluntary
 Forms the main bulk of the body musculature
 Generally attached to the bone except for the intrinsic muscles of the tongue, upper esophagus and some of the facial expression muscles

Answer 15

SKELETAL MUSCLE

Question 16

 Long cylindrical and multinucleated cells
 10-100 u
 Myoblasts; satellite cells
 Muscle fibers do not branch

Answer 16

SKELETAL MUSCLE FIBER

Question 17

 On cross-section
* fibers appear almost equal in size
* nuclei are located at the periphery or beneath the sarcolemma and may be more than 2

Answer 17

SKELETAL MUSCLE FIBER

Question 18

• the dense CT surrounding the whole muscle

Answer 18

Epimysium

Question 19

• the thin septa that extend to surround each fascicle

Answer 19

Perimysium

Question 20

• the thin septa that extend to surround each fascicle

Answer 20

Perimysium

Question 21

• the delicate reticulum surrounding individual fibers

Answer 21

Endomysium

Question 22

 Fine longitudinal striations and cross-striations are detectable and both are due to the arrangement of myofibril
 Longitudinal sections show heavily stained dark bands alternating with relatively pale bands are seen

Answer 22

SKELETAL MUSCLE FIBER

Question 23

 Dark bands are designated A-bands (myosin)

Answer 23

• H band

Question 24

 Lighter staining bands are I-bands (actin)

Answer 24

• Z line

Question 25

 Structural and functional unit of the skeletal muscle  The segments of myofibrils between successive Z-lines  Includes an A-band and half of the 2 contiguous I-bands

Answer 25

SARCOMERE

Question 26

* free ends are attached to the Z-line, then towards the A-band up to the edge of the H-zone

Answer 26

ACTIN (THIN) MYOFILAMENTS

Question 27

* occupy the entire A-band

Answer 27

MYOSIN (THICK) MYOFILAMENTS

Question 28

* Composed of F-actin, tropomyosin and troponin complex (TnT, TnC, TnI) * Attached to the α-actinin of the Z disc

Answer 28

MYOSIN (THICK) MYOFILAMENTS

Question 29

* Bound to proteins of M line and to the Z disc by a large protein called titin (with spring-like domains) * Consists of many myosin bundled together along their rod-like tails with their heads exposed and directed towards thin filaments

Answer 29

MYOSIN (THICK) MYOFILAMENTS

Question 30

 Actin filaments slide past the myosin filaments towards the center of the sarcomere  H zone becomes narrow and may be obliterated  I-band also becomes narrow  A-band remains constant during relaxation and contraction

Answer 30

SLIDING FILAMENT MECHANISM

Question 31

 Corresponds to the endoplasmic reticulum of other cell types  Consists of membrane-bound sarcotubules that forms a canalicular network around each myofibril

Answer 31

SARCOPLASMIC RETICULUM

Question 32

 Devoid of ribosomes  Site of sequestration of calcium during muscle relaxation and for release into the sarcoplasm of free calcium ions that trigger contraction in response to a nerve impulse.

Answer 32

SARCOPLASMIC RETICULUM

Question 33

 Many mitochondria; abundant myoglobin  Oxidative phosphorylation of fatty acids  continuous contraction for prolonged periods such as postural muscles at the back

Answer 33

TYPE I OR SLOW, RED OXIDATIVE FIBERS

Question 34

 Many mitochondria, myoglobin and glycogen  Both oxidative and anaerobic glycolysis  For rapid contraction and short burst of activity such as in athletes

Answer 34

TYPE IIA OR FAST, INTERMEDIATE OXIDATIVE-GLYCOLYTIC FIBERS

Question 35

* maintain firm cohesion of successive cellular units of the myocardium * transmits the pull of one contractile unit to the next cellular unit along the long axis of the myofibrils

Answer 35

 Intercalated discs functions

Question 36

 Modified cardiac muscle fibers that are specialized for impulse conduction

Answer 36

PURKINJE MYOCYTES

Question 37

 Located in the sinoatrial node at the junction of the superior vena cava with the right atrium  Atrioventricular node at the lower part of the interatrial septum  Internodal tracts and bundle of His

Answer 37

LOCATION OF PURKINJE MYOCYTES

Question 38

 Striated and involuntary  Thickest layer of the heart, the myocardium  Branching and anastomosing fiber

Answer 38

Cardiac Muscles

Question 39

 Generally have single nucleus per cell  Ovoid nucleus  nucleus are centrally located unlike the skeletal muscle  Cross-section show moderate variation in the size of muscle fiber Each cell is joined end to end by a surface specialization called intercalated discs

Answer 39

Cardiac Muscles

Question 40

 Fine longitudinal striations and transverse striations are also found  Sarcomere is also the structural and functional unit  The component fibers have inherent automicity and rhythmicity

Answer 40

Cardiac Muscles

Question 41

Myofibrils closely resemble those of the skeletal muscle  Sarcoplasmic reticulum is present but not as highly developed as skeletal muscle

Answer 41

Cardiac Muscles

Question 42

individual fibers are off set such that the wide portion of the cells are adjacent to the thin tapering end of neighboring cells

Answer 42

Smooth Muscle Fiber  When in bundles or in extensive layers

Question 43

appear as a mosaic of irregular polygons of varying sizes  with nuclei found only in larger crosssections

Answer 43

Smooth Muscle Fiber So in transverse sections