Week 2 HG&D

Components of the skeletal system

• Bony Skeleton

• Cartilage

Purpose of the bony skeleton

• Protection and support

• Structure for muscles to work

Purpose of cartilage

Shock absorber and protects joint surfaces

When does cartilage first appear?

During the 5th week

How does cartilage develop?

Interstitial and appositional growth

Three types of cartilage

• Hyaline

• Fibrocartilage

• Elastic

Hyaline (articular cartilage)

• Most abundant & rigid

  • e.g. articular surfaces, trachea, bronchi

Fibrocartilage

• More pliable

  • e.g. acetabulum, intervertebral discs, menisci, tendinous intersections, hip/shoulder labrum

Elastic

• Most pliable

  • e.g. ear & epiglottis

Types of bone cells

• Osteoclasts

• Osteoblasts

• Osteocytes

Function of osteoclasts

Resorption

Function of osteoblasts

Formation

Function of osteocytes

bone maintenance, nutrition

Two types of bone

• Cancellous

• Compact

Characteristics of cancellous bone

• Trabecular bone/spongy bone

• Loose woven strands of bone

• Located at the ends of the long bone

• Houses bone marrow, minerals, vessels

• Flexible

Characteristics of compact bone

• Hard, dense, stiff bone

• Makes up the shaft of the long bone and provides a covering for cancellous bone

Intramembranous Ossification

• Mesenchyme cells differentiate into osteoblasts

• Forms the skull, mandible, and part of the clavicle

Endochondral ossification

Seen in long bones, vertebrae, & pelvis to increase length

Divisions of the skeletal system

(1) Axial and (2) Appendicular

Axial division

Skull, vertebral column, ribs, and sternum

Appendicular division

Pectoral and pelvic girdles and limb bones

Is the skull formed via endochondral or intramembranous ossification?

Both

Skull joint

Sutures ~ fibrous joints

Frontanelles

“soft spots” where several sutures meet

Molding

Change of shape during birth

Calvaria

Frontal, parietal, occipital bones

• Larger than facial region

• Growth greatest during the first 2 years and continues until 16 years

Plagiocephaly

Early fusing of the skull bones causing unilateral and flat head shapes

Parts of the bone (1/4) - Epiphysis

Ends of long bones, secondary centers of ossification

Parts of the bone (2/4) - Epiphyseal plate

Growth plate zone, hyaline cartilage

Parts of the bone (3/4) - Metaphysis

Wide portion of the bone connected to epiphyseal plate

Parts of the bone (4/4) - Diaphysis

Shaft, primary center of ossification

Site of Growth (1/3) - Epiphyseal plate

Site of longitudinal bone growth ~ “growth plate”

(Review slide 37)

Site of Growth (2/3) - Appositional growth

Growth in width

(Review slide 39)

Site of Growth (3/3) - Traction epiphyses

Sites of muscular attachment

(Review slide 40)

After birth, progressive external rotation of tibia and femur until _______ years of age

8 -10

Femoral anteversion

Born with the femur facing anteriorly to the acetabulum (40-60 degrees)

Femoral Remodeling

Femur internally rotates (10-15 degrees); reduce him flexion ~ muscle action from standing

Newborn femoral anteversion magnitude

40-60 degrees

Toddlers (age 3) femoral anteversion magnitude

30 degrees

Preschooler (age 8) femoral anteversion mangitude

10-15 degrees (close to adult norm)

Anteversion vs Retroversion

Anteversion = “toe in”

Retroversion = “toe out”

Torsion

nromal amount of twist present in the long bone

Femoral Torsion

The measure of anterior angulation of the femur head/neck in relation to the condyle alignment; transverse plane

Tibial Torsion

Norms:

• Birth: -15 to -15 degrees (internal tibial torsion)

• 3 to 5 years: 0 degrees (neutral)

• >5 years: 0 to +10 degrees (external tibial torsion)

• Adult: 0 to 30 degrees (external tibial torsion

Internal vs External tibial torsion

Internal: “in-toeing”

External: “out-toeing”

Flat feet

Normal in young children ~ starts to develops after 5 years

Foot alignment (varus)

supinated or inverted

Foot alignment (valgus)

pronation or eversion

Coxa Vara

• Angle of inclination is less than 120 degrees

• Results in shortened leg on that side

• Waddling or Tredelenburg gait

• Limited hip abduction/hip internal rotation ROM

Coxa Valga

• Angle of inclination is greater than 135 degrees

• Can be congenital or acquired

• Acquired

  • Fracture of femoral neck, Ricket’s, Pelvic osteomyelitis, Osteogenesis Imperfecta, Paget’s disease

• (See slide 70 for more)

Normal development in toddlers

• Genu Varum (resolves 24 months)

• Internal tibial torsion (1 to 3 years old)

• Femoral anteversion (30 degrees around age 3)

• Flat feet

Normal development in preschoolers

• Genu valgum (peak 3 to 4 years old)

• Femoral anteversion (gradually diminishes around age 8)

• Flat feet - arches start to develop around 5 years old