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Flashcards in Musculoskeletal Development and Adaptation Deck (40)
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What are somites

Precursor cells that differentiate into dermis (dermatome), skeletal muscle (myotome), and vertebrae (sclerotome)

• Sclerotome differentiates first because vertebre develops very early on in development

• Dermomyotome then forms primary and secondary myotubes (GMs directly correlate to when they get innervated)

• Primary –5-7 weeks GA, Type I fibers (corresponds to spontaneous movements)

• Secondary –30 weeks gestation, Type II fibers later on

(do not need to know Gestational age)


Describe early muscle cells and what should we keep in mind?

Early on there is a lot of interstitial fluid in muscle cells (60% to 20% by 36 weeks)

you have to think about what happens when a baby is born prematurely - what is going on with their muscle fibers, does it relate to strength


Explain what happens to muscles from birth to childhood

1st year after birth muscle fibers divide from existing cells

through childhood muscles increase in length and girth with addition of sarcomeres


What are mononucleated satellite cells and what happens if there is a problem with them?

They are helper muscle cells that hang out next to muscle cells. If muscle cell gets damaged they respon and regenerate damaged cells.

If there is a problem with these cells then this would lead to significant weakness


How are type 1 and type2 muscle fibers distributed

random in a mosaic pattern


how would steroid use, malnourishment and spasticity affect muscle fibers

Steroid use –atrophy of type II

–Malnourishment –conversion of type II to I

–Spasticity leads to structural changes


Muscle Growth is Influenced By?

• Tension of bony growth for length stretches muscle and sarcomeres added so growth is at similar rate to bone

• Active stress of exercise –provides thickness (when working with kids you want to add bulk. also look at the symmetry)

• Strength through use!
-this influences muscles and boney development


Why would you want to cast someone in a lengthen position?

lengthen position will increase sarcomeres while a shortened on will decrease them

After 4 weeks this will revert unless you continue to use the length. This kids will need neuro re-education to keep the length


What are the hip stabilizers and what do they do

Loading stance leg with hip external rotators strengthening, as glut max and TFL couple with IT Band to decelerate lateral weight shift and maintain pelvic alignment

Stance leg goes into relative IR and External rotators help from collapsing. Babies who do not really walk you will see it band anterior and extensors will be lateral. This will also help with the development of greater trochanter and torsion of our bones

- lateral muscle shift laterally and torsion of the bone happens bc of ER force from the muscle


What are growing pains

pains caused by the muscle trying to keep up with the bone growth, bc bone grows first


Consideration with hypertonicity and children

If you have a hypertonic muscle and the kid has a growth spurt then that muscle get even tighter. this will directly affect ROM.

You need to stay ahead of growth spurts


Muscle concerns with CP

- muscle growth is even slower than normal

-sarcomere stretch but there is dec. force production

-inc. risk of injure

-muscle is replaced by collagen

-inc. stiffness at every level (muscle and connective tissue)

while these kids are growing you have to maintain length and strength


What are the 2 processes of bone formation

–Endochondral (intracartilaginous) ossification

–Intramembranous ossification (clavicle, mandible, skull)


Intramembranous ossification

Ossification occurs directly on mesenchymal model


Endochondral (intracartilaginous) ossification

Think long bones

• Mesenchymal models----collagenous and elastic fibers deposited-----cartilaginous models----bone minerals deposited--replace cartilage via ossification


When and where does primary ossification start?

Primary ossification in center of diaphysis starts at 8th week of gestation


When are most bones ossified by (age)

20 years


When are children prone to injury?

There is a growth and ossification hasn't caught up yet


Why would a full term baby bone be stronger than a premature baby bone?

Because ossification happens throughout gestation. So preemies will come out a bit osteopenic


What type of forces lead to bone growth

Loading forces - growth and thickness
intermittent forces lead to bone growth and sustained forces lead to limited growth

Tension - (muscle) provides raised surfaces to the bones (ie: tubercles)

Shearing forces - twisting of bones


Most change to skeletal modeling can be made in the first _____ years



Joint formation

• Begins with cartilaginous models (similar to long bones) with differentiation for joints

• Basic structures formed during 6-8th week gestation, development continues throughout early childhood


Hip joint development

during gestation acetabulum covers femoral head

at birth half of the femoral head covered

coverage inc. until age 10


How do we regain coverage of hip joint?

What happens to children who are NWB

ABduction forces and WBing. Pushes trochanter into acetabulum

children who are not weight bearing will end up with shallow hip joints putting them at risk for dislocation


Heuter-Volkmann Principle

–Reaction to excessive static loading is decreased bone mineralization, decreased integrity and strength of bone


Describe knee joint development

Asymmetric forces lead to asymmetric growth

0-18mo - varus (plum line medial and medial growth more and leg straightens out

18-30mo - straight (but we have an overshoot)

3-4yrs - valgus (plum line lateral and now lateral condyle get intermittent compression)

8-10 yrs - straight

it takes longer to go from valgus to straight bc we are less plastic


What is stapling and describe what is done for a LLD and excessive atypical varus

• LLD -stapling of longer leg at the growth plate so shorter leg can catch up

• Excessive atypical varus –asymmetrical stapling.
-In varus we get more growth of medial condyles, so to encourage even more lateral condyles are stapled


Describe foot and ankle posture

early on: 0-18 months more WBing laterally (protects medial arch)


Femoral Torsion is

Max torsion is and happens at

When does femur de-rotate and what is the degrees

The relationship of the femoral neck and the long bone of the femur

–At birth max antetorsion (medial torsion) of 30 –40 degrees

–Femur de-rotates to 16 degrees by 14-16 years


Femoral Version is

Max version is and happens at

Version in adults is

The relative position of the greater trochanter in the acetabulum
-babies are born in ER
-(IR - retroversion and ER - anteversion)
-regardless of how much torsion they will have the same about of version. They are mutually exclusive

–At birth, max anteversion of 60 degrees

–ER position of thigh

–12 degrees of version as adult


Impact on Alignment for Early Walking:
Birth to 9 months

At birth babies have good amount of twist of long bones relative to the femoral neck. if you have a lot of twist of long bone that means the bone will be medially twisted in. Babies are born with a lot of antetorsion.

•Hip flexion ‘contractures’, hip ER>IR
•Femoral anteversion and antetorsion present
•Knees in genu varum


Impact on Alignment for Early Walking:
9-15 months

9-15 months
•Hip Abduction, flexion, slight ER


Impact on Alignment for Early Walking:
18 to 24 months

•Varum resolved


Developmental changes of the rib cage

Intercostals are shortened and that is why they are obligatory diaphragmatic breathers

Babies rib cage is more splade

Adults have more dome like diaphragm

adult diaphragm is more efficient than a babies


Describe the thorax of a newborn

• Triangular shaped thorax with ribs horizontal
• Tight anterior chest wall
• Diaphragmatic breather
• High RR/low tidal volume


Describe the thorax of a 3-6 month old baby

• Increased UE movement and extensor tone with improved chest expansion
–Tummy time!!

• Improved tidal volume, still diaphragmatic breather


Describe the thorax of a 6 - 12 month old baby

• Upright posture vs. gravity and developing abdominal muscles pull rib cage down and rotated inwards
–Diaphragm in a better position for excursion
–Abdominals stabilize ribs, provide diaphragm with visceral support, promote pressures
–Intercostals expand and can now stabilize chest wall with inspiration, assist with chest expansion and compression

• Thoracic cage height and volume continue to change with development
–Volume is 6% at birth, 30% at 5 and 50% at 10

• Early thoracic cage development is related to lung development!

Sitting allows abdominals and obliques to start to pull down rib cage.

A baby that is not sitting you would expect that the ribcage is flaring


Describe Mary Massery’s Soda-Pop Can Model

Created model to explain the overlapping roles of ventilation muscles, postural control muscles, pressure regulators

What is the core?
All muscles from glottus to pelvic floor

bc it makes a closed system that is responsible for regulating our internal pressures.

This internal pressure is needed for moving limbs, talking, posture

• Positive pressures create functional strength for weak skeletal cage
• Vocal cords---diaphragm (major pressure regulator)---pelvic floor

• Intrathoracic pressure (glottis to diaphragm) and intra abdominal (diaphragm to pelvic floor) pressure

• High pressure always chases the low pressure!
(intraabdominal is higher than intrathoracic pressure. abdominal pressure modulates intrathoracic pressure)


Role of Glottis

Eccentric control of diaphragm for speech production. if you work on core with babies it will help with speech production.

• Pressure regulator for ITP • At rest is open
• When closed, increased ITP, provides more support –isometric contractions
–Practice engaging glottis

• Midrange during speech
• Massery (2013) found that CoP (postural control) control improved with midrange glottal control.


Normal Development of Breathing Patterns

• Newborn: diaphragmatic

• By 12 months: accesses all breathing muscles for chest and diaphragmatic patterns

• Over 12 months: refines skill –speech!