Download Musculoskeletal System

Musculoskeletal System
Sugito Wonodirekso, MS, Dr
Department of Histology
FMUI
Materials
 Skeletal muscle
 Joint
•
•
•
•
12/7/2008
Joint types
Bone
Cartilages
Supporting tissues
Musculoskeletal System
2
Objectives of the muscle tissue
 Identify skillfully the skeletal muscle structure
 Identify the structural and functional different between
3 major types of muscle tissue
 Comprehend the relationships between muscle
fascicles, muscle fibers, myofibrils, and myofilaments
 Explain the structure and function of T-tubule in
skeletal muscle
 Analyze the relationships between normal structure
and function of skeletal muscle
 Explain the regeneration process of skeletal muscle
12/7/2008
Musculoskeletal System
3
General features of muscle tissues
 Terminology
• Prefixes: Sarco- and or myo-
 Specialized for contraction
• Myofilaments: actin (thin) and myosin (thick)
 Mesodermal origin
• Exception: iris smooth muscle arise from ectoderm
 Cell shape
• May reach 4 cm long  called fibers (myofibers)
 Organization
• Works in groups or separately
 Two major types
• Smooth and striated
12/7/2008
Musculoskeletal System
4
Muscle types and characteristics
Features
Skeletal muscle
(Striated voluntary)
Cardiac muscle
(Striated, involuntary)
Smooth muscle
(Non-striated)
Cells
Thick, long, cylindric
unbranched
Branched, cylindric
Small, spindle-shape
Nuclei per cell Many, peripheral
One or two, central
One, central
Filament ratio 6 thin/1 thick
6 thin/1 thick
12 thin/1 thick
Sarcoplasmic Highly organized
reticulum and sarcoplasmic reticulum
surrounds myofibrils
myofibrils
Less organized
sarcoplasmic reticulum;
no distinc myofibrils
Poorly organized
sarcoplasmic reticulum;
no distinc myofibrils
T-tubules
At A-I junction; form
triads
At Z lines; form dyads
None
Motor endplates
Present
Absent
Absent
Involuntary
Involuntary
Intercalated disks at cellto-cell junctions
Abundant caveolae
Motor control Voluntary
Other
12/7/2008
Prominent fascicles
Thick perimysium and
Musculoskeletal System
epimysium
Cell overlap
5
Skeletal muscle (this is our concern now)
 Histogenesis
• Mesenchymal cells of mesodermal origin fuse to
each other to make
• Myoblasts which then fuse to make
• Myotubes which later
• Elongate by incorporating additional myoblasts
• Eventually accumulated myofilaments which are
organized into myofibrils and displaced nuclei and
other cytoplasmic components peripherally
12/7/2008
Musculoskeletal System
6
Skeletal muscle cells
 Mature skeletal muscle fibers:
•
•
•
•
•
Elongated
Unbranched
Cylindrical
Multinucleated
Flattened peripherally displaced nuclei, lie just under
sarcolemma (muscle cell plasma membrane)
• Most organelles and sarcoplasm (muscle cells cytoplasm)
are displaced near the nuclei’s poles
• Sarcoplasm contains mitochondria, glycogen granules, and
myoglobin (oxygen-binding protein). It accumulates
lipofuscin pigment with age
• Mature skeletal cell are end cells and cannot divide
12/7/2008
Musculoskeletal System
7
Skeletal muscle tissue
 Cross-cut of skeletal muscle to show
connective tissue partitioning of
muscle into groups or bundles of
fibers. Endomysium is very delicate
and lies between individual fibers,
while perimysium is more visible
and lies around a group of fibers.
Epimysium is not seen here but
ensheaths a whole muscle. In this
picture notice the presence of small
blood vessels in both perimysium
and endomysium. Notice also the
cross-cuts of myofibrils within the
muscle cells, making them look
grainy.
12/7/2008
Musculoskeletal System
8
Higher power of skeletal muscle for details of cross-striations.
Notice thin Z discs and heavy A bands. From one Z disc to the
next is a sarcomere, the unit of muscle contraction. In the upper
muscle cell notice shadowy myofibrils running longitudinally.
12/7/2008
Musculoskeletal System
9
Skeletal muscle cells (fibers), with crossstriations and peripheral nuclei.
12/7/2008
Musculoskeletal System
10
Muscle fibers organization
12/7/2008
Musculoskeletal System
11
Sarcomeres (contraction units)
12/7/2008
Musculoskeletal System
12
Sarcomere and the cross sections
12/7/2008
Musculoskeletal System
13
Myofilament
 Thin filaments (actin)
• Filamentous actin (F-actin) is polymeric chain of
globular actin (G-actin) monomer. Each thin filament
consist of 2 double helix wound F-actin strands
• Tropomyosin is long, thin, double-helical polipeptides
that wrap around the actin double helix, lies in
grooves on its surface, and spans 7 G-actin monomers
• Troponin is a complex of 3 globular proteins.
o TnT (Troponin T) attaches each complex to specific site on
each tropomyosin molecule,
o TnC binds calcium ions, and
o TnI inhibits the interaction between the thin and thick
filaments
12/7/2008
Musculoskeletal System
14
Actin filaments
12/7/2008
Musculoskeletal System
15
Myofilament
 Thick filaments (myosin):
• Long golf-club-shaped polypeptide
• A bundles of myosin molecules with their shafts pointing toward
and overlapping in the bundle’s middle and their heads
projecting from the bundle’s ends
• This arrangement leaves a headless region in the center of each
filament corresponding to the H band
• Treating myosin molecule with papain (a proteolytic enzyme)
cleaves them, at a point near head, into 2 pieces
• The piece containing most of the thin shaft is termed light
meromyosin; the head and the associated portion of the shaft
make up the heavy meromyosin
• The head portion of heavy meromyosin has an ATP-binding site
and an actin binding site, which are necessary for contraction
12/7/2008
Musculoskeletal System
16
Actin and myosin filaments relationship
12/7/2008
Musculoskeletal System
17
Myofilament
 Organization
• The banding pattern of skeletal muscle reflects the
grouping of myofilaments into parallel bundles of
thin and thick filaments called myofibrils. Each
muscle fiber may contain several myofibrils; the
number depending on its size.
• Take special attention on the appearance of
myofibrils in cross- and longitudinal section,
especially in EM images and its schematic version
12/7/2008
Musculoskeletal System
18
Sarcomere and muscle contraction
 Diagram of contraction of
skeletal muscle. On the left is
the view with light microscopy.
On the right are the thin actin
filaments and thick myosin
filaments seen in EM. Notice
that the total width of the A
band stays the same
throughout and that the
sliding in or out of the actin
filaments determines the
width of the H band. Consider
which filaments you would see
if you cut the muscle crosswise through the I band, A
band, or H band.
12/7/2008
Musculoskeletal System
19
T-tubules and the Triads
 Drawing of relationship (at EM level)
of myofibrils to sarcoplasmic
reticulum (smooth ER) and T-tubules
in skeletal muscle. In this drawing the
sarcoplasmic reticulum is labelled
"sarcotubules" and "terminal
cisternae". Notice that T-tubules are
extensions of the sarcolemma (cell
membrane, seen at right-hand edge),
so that depolarization can spread
along this part of the sarcolemma as
well. (See diagrams and further
explanation in your textbook.)
12/7/2008
Musculoskeletal System
20
The sarcomere and the diads


Same diagram, for cardiac muscle.
Note differences with skeletal muscle in:
•
•
•

12/7/2008
their amount and arrangement of sarcoplasmic
reticulum
the presence or near-absence of terminal cisterns
(next to the T-tubules)
the position of T-tubules in relation to the A, I, and
Z bands seen at the left.
A triad consists of two terminal cisterns with a
T-tubule in the middle. When the cisterns are
not well developed, a true triad does not exist.
A diad means two elements are together, as
with one T-tubule and a neighboring bit of
sarcoplasmic reticulum. NOTE: sarcoplasmic
reticulum is just a form of smooth endoplasmic
reticulum (SER). In muscle it is particularly
associated with the release of calcium ions
needed for contraction.
Musculoskeletal System
21
The sarcomere
 EM of several myofibrils running
longitudinally through skeletal
muscle cell. Between individual
myofibrils lie the mitochondria
(M) and glycogen (G) of the
cytoplasm. Within each myofibril
are the typical striations:
•
•
•
•
A= A band;
I= I band;
Z= Z line; and
H= H band.
 The banding is formed by the
arrangement of myosin and actin
filaments.
12/7/2008
Musculoskeletal System
22
Sarcomere and the contraction
12/7/2008
Musculoskeletal System
23
Skeletal muscle regeneration
12/7/2008
Musculoskeletal System
24
Skeletal muscle regeneration
12/7/2008
Musculoskeletal System
25
Skeletal muscle regeneration
12/7/2008
Musculoskeletal System
26
Contraction process-1
12/7/2008
Musculoskeletal System
27
Contraction process-2
12/7/2008
Musculoskeletal System
28
Contraction process-3
12/7/2008
Musculoskeletal System
29
Muscle fibers organization
12/7/2008
Musculoskeletal System
30
Joints
Basic joint
components are:
1. Bone
2. Hyaline Cartilage
3. Dense collagen
tissues
12/7/2008
Musculoskeletal System
31
Bone
Endochondral bone formation
12/7/2008
Musculoskeletal System
32
Bone
Endochondral bone formation
12/7/2008
Musculoskeletal System
33
Bone growth and remodelling
12/7/2008
Musculoskeletal System
34
Compact bone with Haversian system
12/7/2008
Musculoskeletal System
35
Haversian Lamelae and the remnant
12/7/2008
Musculoskeletal System
36
Osteocytes’ lacunae and its canaliculi
12/7/2008
Musculoskeletal System
37
Osteocyte and the canaliculi
12/7/2008
Musculoskeletal System
38
Osteocyte
EM. Osteocyte in its
lacuna. Notice the
pericellular space,
organell some of
which are globules
containing Calcium,
and the cell processes
12/7/2008
Musculoskeletal System
39
Tight junction between osteocytes’
processes in its canaliculus
12/7/2008
Musculoskeletal System
40
Muscle-bone attachment
12/7/2008
Musculoskeletal System
41
Younger compact bone tissue
12/7/2008
Musculoskeletal System
42
Bone dynamics
Appositional growth
12/7/2008
Bone vascular system
Musculoskeletal System
43
Bone
Osteocytes
12/7/2008
Compact bone tissue
Musculoskeletal System
44
Hyaline cartilage
12/7/2008
Musculoskeletal System
45
Cartilage
Chondrocyte
12/7/2008
Appositional growth
Musculoskeletal System
46
Cartilage
Hyalin cartilage
12/7/2008
Elastic cartilage
Musculoskeletal System
47
Cartilage
Elastic cartilage
12/7/2008
Fibrous cartilage
Musculoskeletal System
48
Cartilage
Hyalin cartilage
12/7/2008
Hyalin cartilage on the joint
surface
Musculoskeletal System
49
Joint
12/7/2008
Musculoskeletal System
50
Bone
 Highly vascularized
 Dynamic tissue
 Regenerate completely
12/7/2008
Musculoskeletal System
51
Cartilage
 Avascular
 Regenerate poorly
12/7/2008
Musculoskeletal System
52
Joint supporting tissues
 Mostly dens collagen connective tissues
 Regenerate fairly good but not as good as
bone
12/7/2008
Musculoskeletal System
53
How joints working
 Vertebrates move by application of the
principles of the lever. Levers amplify or
increase the force or velocity of motion. The
amount of amplification depends on the
length of the lever. There are three types of
skeletal system, all interact with muscles using
the lever.
12/7/2008
Musculoskeletal System
54