Musculoskeletal system

Components of skeletal system

bone, cartilage and ligaments

functions of the skeletal system

support, protection, leverage, stores minerals, and produces blood cells

ligament

a sheer or band of tough fibrous tissues that connects two bones together

components of muscular system 

muscle, tendons, motor unit (neurons that go to the inner parts of the skeleton)

functions of muscles

produces skeletal movements, maintains body posture and position, regulates opening and closing of bodily orifices, maintains body temp and generates heat

tendon

tough, flexible cord like, fibrous connective tissue that connects muscle to bone

axial skeleton 

skull, vertebral column, ribs and sternum

appendicular skeleton

pectoral and pelvis girdle and bones of the upper and lower limbs

long bones

long, slender and tubular (ex. humurous or femur)

short bones

short and cuboid (ex. carpal bones)

flat bones

two plates of compact bones that are separated by spongy bone (ex. skull bones)

irregular bones

complex shapes, notched or rigid surfaces (ex. vertebrae)

sesamoid bones

round / oval, develop in tendons (ex. patella holds bones in place rather than other bones through ligaments)

epiphysis

compact bone surrounding spongey bone where blood is produced (red marrow)

metaphysis

compact bone

diaphysis (shaft)

medullary canal (marrow cavity)

yellow marrow

fatty network / fat storage

endochondral ossification

bone replaces hyaline cartilage; allows for lengthwise growth, articular cartilage remains along side the epiphyses to support bone to bone articulation and diaphysis and epiphysis fuse when bone growth is done (transitioning from epiphyseal plate to epiphyseal lone)

Intramembranous ossification

bone develops from a fibrous membrane; occurs in bones of skulls and clavicles

bone remodeling

bone mass is constantly recycled (5-7% / week). spongy bone is replaced every 3-4 years and compact bone is replaced every 10 years

cycle of bone remodeling

osteoclasts reabsorb old / damaged bone, osteoblasts lay down new bone with the help of osteocytes and osteogeneic cells help with stem cells

control of bone growth

mechanical stress, hormone aspects (too much thyroid can increase the rate of bone absorption)

osteoporosis

bones are weak and brittle. potential treatments = Ca2+, vitamin d and hormone replacement therapy

fractured bones and healing steps

1) hematoma

2) Fabrocartiliginous hematoma 

3) bony cartilage froms

4) bone remodelling occurs

joint / arthrosis

a site where two skeletal elements come together (articulation)

solid joints

fibrous solid joint: syndesomosis (ulna), gomphosis (teeth) and suture (skull)

cartiliginous solid joints: synchondrosis (allows ribs to attach to sternum)  and symphysis (cartiliginous disc between two bones ex. holds pubic bones in the pubic symphysis in place) and intervertebral discs (vertebrae)

synovial joints

synovial cavity is filled with synovial fluid. synovial and fibrous membrane are in a joint capsule and articular cartilage

Common associated structures (not found in all synovial joints)

articular discs, fat pads, bursae and tendinous synovial sheaths 

myology

the study of muscles

epimysium

dense connective tissue surrounding the entire muscle organ

perimysium

connective tissue surrounding skeletal muscle fascicles (bundle of muscle fibres)

endomysium

connective tissue surrounding individual muscle fibres (myofiber)

sarcomeres

repeating, contractile units of a skeletal muscle fibres

myosin 

thick filaments that are contractile

actin

thin filaments

contraction

increase in myofilament overlap and decrease in sarcomere length 

lengthening

decrease in myofilament overlap and increase in sarcomere length (lengthens the muscles)

muscle building

increase in muscle size = increase in myofiber diameter

flexibility

increase in muscle length = increase in the number of  sarcomeres along the myofibril

Phasic contractions

isometric or isotonic ( concentric or eccentric) contraction

Isometric contraction 

load applied without changing joint angle and no change in muscle length 

concentric contraction

decrease in muscle length and joint angle 

eccentric contraction 

increase in muscle length and joint angle 

skeletal muscle attachements

the importance of understanding muscle origin and insertion attachments

agonist

prime mover, concentric contraction

antagonist

controls, slows, or resists the agonist movement, eccentric contraction 

synergist

additional muscles that assist in agonist function 

ex. elbow flexion

biceps = agonist, triceps = antagonist, brachialis = synergist 

ex. elbow extension

biceps = antagonist, triceps = agonist 

muscle nomenclature

shape= rhomboid, size = rhomboid major or minor, action = levator scapulae or supinator, points of attachment = coracobrachialis, number of divisions = biceps brachii  

ex. trapezius

upper fibres = elevation of scapula, middle fibres = retraction of scapula, lower fibres = depression of scapula

muscle attachements

origin = most proximal, fixed attachment (least movement)

insertion = most distal, moveable attachment

uniaxial synovial joints

pivot or hinge joints that flex or extend

biaxial synovial joint 

saddle or condyloid (ellipsoid) that flexes, extends, abducts or adducts

multiaxial synovial joint

ball and socket joint that flexes, extends, abducts, adducts, rotates and circumducts

the skull

22 bones

viscercranium

facial skeleton and bones of jaw = ~14 bones: Palatine (2), Nasal (2), Lacrimal (2), Zygomatic (2), Inferior nasal conchae (2), maxilla (2), mandible (1), vomer (1)

neurocranium

protects the brain, has 8 bones: Frontal (1), Pariteal (2), Occipital (1), Temporal (2), Ethmoid (1), Sphenoid (1) 

sutures of neurocranium

solid, fibrous joints, calvaria = skull cap

the zygomatic arch

arch between temporal process of zygomatic bone and the zygomatic process of the temporal bone 

Mandible

look at image

the temporomandibular joint

modified synovial hinge joint

look at image

the neonatal skull 

small viscerocranium, large neurocranium, obtuse angle of the mandible, underdeveloped mastoid process

fontanelles

soft spot

posterior fontanelles

closes within ~2 months of age

anterior fontanelles

closes within ~7-18 months of age

The vertebral column 

consist of ~33 vertebrae (ranges form 32-33)

7 cervical (CI-CVII)

12 Thoracic (TI-TXII)

5 Lumbar (LI-LV)

Sacrum (5 fused sacral vertebrae I-V)

Coccyx (3-5 coccygeal vertebrae I-IV)

curvatures of the spine

primary: concave anteriorly = kyphotic

secondary: concave posteriorly = lordotic

secondary curvatures mature throughout early development and growth

C= 2 degrees

T= 1 degree

L=2 degrees

S = 1 degree

abnormal curvatures of the spine 

cervical / thoracic kyphosis (curves posteriorly), lumbar lordosis (curves anteriorly) or scoliosis  

Typical Features of Vertebral Bones

vertebral body, vertebral foramen, transverse process, spinous process, vertebral / neural arch, inferior / superior articular process and inferior / superior vertebral notch 

cervical vertebrae

large triangular vertebral foramen, transverse foramina, and contains the vertebral artery

thoracic vertebrae

circular vertebral foramen, heart-shaped vertebral body, has surface for rib attachments and long, narrow and sloped spinous process

lumbar vertebrae

smaller triangular vertebral foramen, kidney shaped vertebral body, short and wide spinous process

the atlas (C1)

supports the head and has an articular surface for the skull and anterior arch

the axis (CII)

helps the skull rotate and has the dens process

atlanto-occipital joint

nods head ‘yes’ (flexion and extension of head). Synovial hinge joint

atlantoaxial joint

turns head ‘no’ (rotation). Synovial pivot joint

transverse ligament hugs the dens axis

intervertebral disc

annulus fibrous (fibrocartilage) has an inner and outer ring (symphysis joint)

clinical considerations

movements of vertebral column

cervical and lumbar: extension and flexion, lateral extension and flexion

Cervical and thoracic: rotation of the head, neck, and upper trunk

ligaments of vertebral column

Anterior and posterior longitudinal ligament runs the length of the vertebral column and is on either side of vertebral bodies. limits hyperextension and hyperflexion of vertebral column (ex. whiplash)