Lesson 14
1. Identify the function of bones.
Lever
o Upper and lower limbs push and pull
Calcium store
o 97% of body’s calcium is stored in bone
o Pregnancy and menopause leach the bone of calcium
Important to take calcium supplements
Protective
o Most external forces exceed the tolerance of bone
o Ex. skull protects brain
Marrow holder
o In cavities of unstressed bone
2. Compare and contrast the layers of bone and their functions.
Periosteum
o Adheres to surface of bone
o Two layers
Connective tissue
Dense membranes
o Contains nutrient blood vessels
o During growth and development it contributes to bone elongation
and modeling
o When the bone is injured, participates in its recovery
Cortical bone (compact)
o 80% of skeletal mass
o Slow turnover
o High resistance to bending and torsion → strength of bone
o Haversian canals
Tunnel with blood vessels, nerves and lymphatics
Concentric layers of mineralized bone
Trabecular bone (spongy)
o 20% of mass
o 80% of bone surface
o High turnover rate
o Composed of bundles of short and parallel stands
o Center contains marrow
3. List the parts of a synovial joint.
Synovial joint
o Sliding surfaces of bone covered with cartilage
o Joint cavity is sealed with synovial membrane which secretes
synovial fluid
, o Bursa is large area of synovial sac at ends of bone
o Joint cavity may also contain
Menisci
a thin fibrous cartilage between the surfaces of some
joints that acts as a shock absorber, ex. the knee
Discs of cartilage
4. Describe the process of bone remodeling, including factors that stimulate and
inhibit the process.
Bone remodeling is a continuous process
o Resorption → Reversal → Formation → Quiescence
o Resorption
Resorption occurs from osteoclastic breakdown of trabecular
bone via secretion of proteolytic enzymes; calcium is then
taken up by osteoclasts and released into circulation
Resorption exists for two reasons:
To liberate calcium and other ions
To clear out worn out pieces of skeleton and promote
the deposition of newer, better material.
, o Reversal
Mesenchymal stem cells, precursors to osteoblasts, appear
along the burrow where osteoclasts removed bone. These
cells then proliferate and differentiate into pre-osteoblasts
o Formation
Pre-osteoblasts mature into osteoblasts at the surface of the
burrow and release osteoid at the site, forming a new soft
non-mineralized matrix
New matrix is later mineralized with calcium and phosphorus
o Quiescence
Site of remodeling, containing resting lining cells, remains
dormant until the next cycle
Factors that stimulate bone remodeling
o Systemic Hormones
Parathyroid Hormone
Vitamin D
Parathyroid hormone
Growth Hormone
Thyroid Hormone
Sex hormones**
Stimulate bone turnover during skeletal growth, but
inhibit turnover during adulthood.
o Locally acting factors
Interleukin-1
Parathyroid hormone
Tumor necrosis factor
Insulin-like growth factors
Factors that inhibit bone remodeling
o Systemic Hormones
Sex hormones**
Calcitonin
o Locally acting factors
Mechanical Loading (weight bearing exercises)
Inhibits bone resorption, but stimulates formation
Interferon gamma
5. List the three types of muscle and if they are voluntary or involuntary.
Skeletal muscle
o Voluntarily move the body
o Generally attached to bone
o Organized in fibers rather than cells
o Vary in length
1mm to 60 cm
, Smooth muscle
o Involuntary
Can contract without nerve stimulation
o Found in internal organs, stomach, intestines, blood vessels
Contracts to move food, move blood, change pupil size
o Organized in spindles
o Surrounded by connective tissue
No tendons
Cardiac muscle
o Only found in the heart
o Striated, but involuntary
o Contract without stimulation by CNS
Sinoatrial node
o Spread the information through gaps in the muscle
o One muscle cell with one nucleus and branching fibers
6. Explain how muscle attaches to bone.
Muscles attach by
o Tendons
o Aponeurosis = Flat tendon
o Flesh
7. Discuss how muscle tone is maintained.
Muscles do not snap from relaxation to contraction
o Rather, some motor units or fibers are contracting, some relaxing
and some in stasis providing muscle tone
Muscle contraction is opposed by
o Passive internal resistance of the muscle or articular tissues
o Opposing muscle and soft tissue
o Inertia of whatever it is trying to move
o Load and gravity
8. Identify how actin and myosin cross link to cause muscle contraction in the
sarcomere.
The globular heads of myosin bind to actin, forming cross-bridges. The
motor activity of myosin moves its head groups along the actin filament.
This movement slides the actin filaments from both sides of the sarcomere
toward the center of the sarcomere, shortening the sarcomere and
resulting in muscle contraction
1. Identify the function of bones.
Lever
o Upper and lower limbs push and pull
Calcium store
o 97% of body’s calcium is stored in bone
o Pregnancy and menopause leach the bone of calcium
Important to take calcium supplements
Protective
o Most external forces exceed the tolerance of bone
o Ex. skull protects brain
Marrow holder
o In cavities of unstressed bone
2. Compare and contrast the layers of bone and their functions.
Periosteum
o Adheres to surface of bone
o Two layers
Connective tissue
Dense membranes
o Contains nutrient blood vessels
o During growth and development it contributes to bone elongation
and modeling
o When the bone is injured, participates in its recovery
Cortical bone (compact)
o 80% of skeletal mass
o Slow turnover
o High resistance to bending and torsion → strength of bone
o Haversian canals
Tunnel with blood vessels, nerves and lymphatics
Concentric layers of mineralized bone
Trabecular bone (spongy)
o 20% of mass
o 80% of bone surface
o High turnover rate
o Composed of bundles of short and parallel stands
o Center contains marrow
3. List the parts of a synovial joint.
Synovial joint
o Sliding surfaces of bone covered with cartilage
o Joint cavity is sealed with synovial membrane which secretes
synovial fluid
, o Bursa is large area of synovial sac at ends of bone
o Joint cavity may also contain
Menisci
a thin fibrous cartilage between the surfaces of some
joints that acts as a shock absorber, ex. the knee
Discs of cartilage
4. Describe the process of bone remodeling, including factors that stimulate and
inhibit the process.
Bone remodeling is a continuous process
o Resorption → Reversal → Formation → Quiescence
o Resorption
Resorption occurs from osteoclastic breakdown of trabecular
bone via secretion of proteolytic enzymes; calcium is then
taken up by osteoclasts and released into circulation
Resorption exists for two reasons:
To liberate calcium and other ions
To clear out worn out pieces of skeleton and promote
the deposition of newer, better material.
, o Reversal
Mesenchymal stem cells, precursors to osteoblasts, appear
along the burrow where osteoclasts removed bone. These
cells then proliferate and differentiate into pre-osteoblasts
o Formation
Pre-osteoblasts mature into osteoblasts at the surface of the
burrow and release osteoid at the site, forming a new soft
non-mineralized matrix
New matrix is later mineralized with calcium and phosphorus
o Quiescence
Site of remodeling, containing resting lining cells, remains
dormant until the next cycle
Factors that stimulate bone remodeling
o Systemic Hormones
Parathyroid Hormone
Vitamin D
Parathyroid hormone
Growth Hormone
Thyroid Hormone
Sex hormones**
Stimulate bone turnover during skeletal growth, but
inhibit turnover during adulthood.
o Locally acting factors
Interleukin-1
Parathyroid hormone
Tumor necrosis factor
Insulin-like growth factors
Factors that inhibit bone remodeling
o Systemic Hormones
Sex hormones**
Calcitonin
o Locally acting factors
Mechanical Loading (weight bearing exercises)
Inhibits bone resorption, but stimulates formation
Interferon gamma
5. List the three types of muscle and if they are voluntary or involuntary.
Skeletal muscle
o Voluntarily move the body
o Generally attached to bone
o Organized in fibers rather than cells
o Vary in length
1mm to 60 cm
, Smooth muscle
o Involuntary
Can contract without nerve stimulation
o Found in internal organs, stomach, intestines, blood vessels
Contracts to move food, move blood, change pupil size
o Organized in spindles
o Surrounded by connective tissue
No tendons
Cardiac muscle
o Only found in the heart
o Striated, but involuntary
o Contract without stimulation by CNS
Sinoatrial node
o Spread the information through gaps in the muscle
o One muscle cell with one nucleus and branching fibers
6. Explain how muscle attaches to bone.
Muscles attach by
o Tendons
o Aponeurosis = Flat tendon
o Flesh
7. Discuss how muscle tone is maintained.
Muscles do not snap from relaxation to contraction
o Rather, some motor units or fibers are contracting, some relaxing
and some in stasis providing muscle tone
Muscle contraction is opposed by
o Passive internal resistance of the muscle or articular tissues
o Opposing muscle and soft tissue
o Inertia of whatever it is trying to move
o Load and gravity
8. Identify how actin and myosin cross link to cause muscle contraction in the
sarcomere.
The globular heads of myosin bind to actin, forming cross-bridges. The
motor activity of myosin moves its head groups along the actin filament.
This movement slides the actin filaments from both sides of the sarcomere
toward the center of the sarcomere, shortening the sarcomere and
resulting in muscle contraction
