week 5: components of long bones + articulation and joints

components of long bone: diaphysis

long tubular shaft of bone

• internal medullary cavity surrounded by spongy bone 

  • external composed of compact bone 

components of long bone: epiphyses

proximal and distal extremities

• internal is primarily spongy bone

components of long bone: epiphyseal plate

disks of hyaline cartilage at diaphysis/epiphysis boundaries

• sites of bone growth → inc length

  • cartilage is later replaced with bone

components of long bone: epiphyseal line

remnant of the epiphyseal plate once bone growth stops

components of long bone: medullary (marrow) cavity

central core of long bone

• contains red marrow in children

• contains yellow (fat) marrow in adults

components of long bone: periosteum

double CT membrane layer casing outer bone surface

• outer layer = dense irregular 

• inner layer = ostoblasts/clasts 

• site of bone grown → inc diameter 

components of long bone: endosteum

CT membrane covering internal surface of the bone

• also contains osteoblasts/clasts

components of long bone: articular cartilage

thin smooth layer covering the joint surfaces of long bones → reduces friction

• no periosteum

articulations and joints: functional classification

based on degree of joint movement

• synanthrotic: immovable → sutures in skull

• amphiarthrotic: slightly moveable → pubic symphysis

• diarthrotic: freely moveable synovial joints → hip, knee, elbow

articulations and joints: structural classification

based on:

• presence or absence of joint cavity

• type of connecting tissue

articulations and joints: structural classification | fibrous joint 

• no joint cavity 

• fibrous CT binds bones together 

skull sutures 

articulations and joints: structural classification | cartilaginous

• no joint cavity

• cartilage connects adjacent bones

intervertebral disks, costal cartilage

articulations and joints: structural classification | synovial joint

• has a joint cavity

• held together by articular capsule and fibrous CT

ligaments → hip, knee, elbow, shoulder

structure of synovial joint

• articular (hyaline) cartilage of bone on the joint interfaces 

• joint cavity containing synovial fluid 

• articular/joint capsule: encloses cavity and unites the adjacent bones 

structure of synovial joint: articular/joint capsule layers 

• internal synovial membrane layer: secretes synovial fluid 

• external layer: fibrous capsule (dense irregular CT) continuous with the periosteum of adjacent bones 

• reinforcing ligaments: internal/external bands of CT that provide additional joint strength 

types of synovial joints: gliding (plane)

flat articular surfaces → allow only short gliding movements

• sacroiliac joint, carpals

types of synovial joints: hinge 

convex projection of a bone fits into concave depression of another 

• permits flexion/extension

• knee elbow 

types of synovial joints: pivot join

rounded end of one bone projects into ring or groove of another → permits unaxial rotation

• superior ulna/radius, atlas/axis

types of synovial joints: ball and socket joint 

spherical head of one bone articulates with socket of another → permits movement in all planes 

• femur, acetabulum