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Skeletal and Muscular
Systems
Powerpoint #2
Unit 8 – Chapters 36
Working together to create movement
Skeletal System
Structures:
Bones
Cartilage
Ligaments
Functions
Supports body
Protects internal organs
Allows for movement
Stores mineral reserves
Provides a site for blood cell
formation
• How many bones in a human
Skeleton?
• 206
• How many in babies?
• ~ 300
• Axial Skeleton: spine, ribcage, skull
• Appendicular: arms, legs, pelvic girdle,
shoulders
• What are bones?
• A solid network of living cells and protein
fibers that are surrounded by deposits of
calcium salts
Bones: 3 Parts
Spongy bone
• Not soft or spongy
• Very strong
• Structure resembles the
supporting structure of
bridges.
• Strong but lightweight
Compact bone:
• Very dense (no spaces like
spongy bone)
• Outer portion of bone
• Contains Haversian canal
for veins and arteries to
run through
Haversian Canals
Bone Marrow:
• Soft tissue
• Found in bone cavities
• Yellow Marrow: fat cells
• Red marrow:
• makes red blood cells,
platelets and most white
blood cells
• ~1/2 red marrow turns into yellow
in adults
• If severe blood loss, some yellow
can turn back to red
Development of bone:
• Cartilage: Tough, elastic, connective tissue
• Found in: ears, between bones, larynx, and
other various places.
Development of Bone
• http://www.youtube.com/watch?v=78RBpWSOl08
• Ossification: cartilage replaced by bone
• Osteoblasts:cells that build bone
• Osteoclasts:cells that break down bone
• Growth Plates (epiphyseal plates): found in most
long bones (leg and arm bones) cartilage continues
to grow here until completely replaced by bone
during adolescence=stop growing
Types of Joints -Ball and socket
Types of Joints- Hinge
Types of Joints- Saddle
Types of Joints
• Pivot
Structure of Joints
• Ligaments: Connects Bone to Bone
• Tough, fibrous tissue
Anterior Cruciate Ligament
Fractures
Structure of Joints
• Bursa: small fluid-filled sac
• provides a cushion between bones and
tendons and/or muscles around a joint.
Bursitis
Arthritis
Arthritis
Rheumatoid arthritis
Osteoarthritis
Compare Osteoarthritis and
normal knee
Total Knee Replacement
Total Knee Replacements
Total Knee Replacement
Osteoporosis
29
Types of Muscle


The human body is comprised of ~640-850
muscles (sources varying regarding what is
defined as different parts of a single muscle or
as several muscles)
makes up 30-35% (in women) and 42-47% (in
men) of body mass.
Three types of muscle:
Skeletal muscle
Cardiac muscle
Smooth muscle
32
A. Skeletal (Striated) Muscle
 moves
various parts of the skeleton
 voluntary control
 Repeated activation of a skeletal muscle
can lead to fatigue
 Can have many nuclei
 Striated (striped appearance)
33
Skeletal Muscles work in PAIRS
Bending or straightening of elbow requires
the coordinated interplay of the biceps
and triceps muscles
34
B. Smooth Muscle

Located in the blood vessels, the
respiratory tract, the iris of the eye,
the gastro-intestinal tract

contractions are slow and uniform

Is fatigue resistant

Activation is involuntary

Has one nucleus
35
C. Cardiac Muscle

Functions to provide the contractile activity of the
heart

Activation is involuntary (like smooth muscle)

Can have 2 nuclei, usually has 1

Is very fatigue resistant
36
Components of skeletal muscle
myofibril
37
muscle fiber
muscle fiber bundle
Muscle Fibers: Cylinder-shaped cells that
make up skeletal muscle

Made of myofibrils which is made up of a
number of myofilaments

Two types of protein myofilaments:
- Actin:
thin filament
- Myosin: thick filament
 Divided into functional units called sarcomeres,
seperated by region called Z lines.

Group of fibers activated via same nerve: motor
unit
38
High microscope magnification of sarcomeres
within a myofibril
39
Muscle Contraction
Muscle Contraction Steps
1.
Myosin head attaches to binding site on actin
forming a cross bridge
1.
After the cross bridge is formed the myosin
head bends, called a power stroke, pulling on
the actin filaments and causing them to slide.
1.
Myosin attached to actin until another ATP
binds causing it to release (explains rigor mortis)
1.
Muscle contraction is a little like climbing a
rope. The cross bridge cycle is: grab -> pull ->
release, repeated over and over
Control of Muscle Contraction
(animation)
1.
2.
3.
4.
5.
Muscle cells are "shocked” by nerve impulses
from motor neurons.
Neurotransmitters (acetylcholine) are released by
neuron, stimulating muscle fiber to release Ca2+
When a muscle is relaxed, tropomyosin blocks
cross-bridges.
When Ca2+ high enough, it binds to troponin,
displacing tropomyosin, exposing myosin binding
sites on actin.
Myosin can now form crossbridge
Control of Muscle Contraction
(Neuromuscular junction)
Tendons
Connect Muscle to Bone
Tendon Ruptures
Terminology
 Sprain: when
a ligament is
stretched too much
 Strain: when
a muscle or tendon
is stretched too much