Lecture 3: The Skeleton Flashcards
Axial skeleton
skull, spine, ribcage
supports what is necessary for life (can survive w/ ONLY axial skeleton)
Appendicular skeleton
upper extremities, lower extermities, pelvis
pelvis can be axial
The Spine
5 sections:
Cervical spine (7)
Thoracic spine (12)
Lumbar spine (5)
Sacrum
Coccyx
Has lordortic (fwd) and kyphotic (bwd) curves
- weak point of skeleton b/c of lots of motion + lots of loading
Cervical spine
(7) - Neck
- flexion/extension (nodding) + rotation (shaking head)
- lordotic
Thoracic spine
(12) - Ribcage
- protects heart and lungs
- does NOT twist
- kyphotic
Lumbar spine
(5) - low back
- can twist
- lordotic
Sacrum
part of pelvis
5 separate vertebrae as fetus THEN fused by birth
Coccyx
Tail bone
- anchor for many connextive tissues that make up pelvic floor
NOT vestigial
Hardest bone in body
Teeth then sternum
Functions of skeleton
- attachment for muscles
- leverage for applying torque to jts.
- protects vital organs (brain, lungs, heart)
- support soft tissue
- making new RBCs (long bones have bone marrow)
- reservoir for calcium and phosphate
Wolff’s Law of Bone
Use it or lose it (remodeling)
Bone is laid down in areas of high stress, bone is lost in areas of low stress
Osteoblasts lay down bone continuously
Osteoclasts break down bone continuously
Stress adjusts the balance btwn both
Stress shielding
stiff metal implant offloads the surrounding bone so the bone resorbs
Charnley hip replacement
included a phalange on stem implanted
- under phalange, there is no bone after a few months b/c metal is stronger then bone
- load goes through metal and not bone = osteoclasts work and causes loosening of jt.
Today’s hip replacement
metal implants have thinner stems w/ less metal = more load goes into bones
Types of bones
Long
Short
Flat
Irregular
Function is related to shape
Long bones
Usually in extremities (app. skeleton)
- Act as levers for muscles about jts.
- Larger in legs than arms
- hollow, rigid, long, light
Ex. femur, tibia, humerus, radius, ulna
Short bones
- tightly packed
- provide SHOCK ABSORPTION and FLEXIBILITY of movement
Ex. carpals, tarsals
Flat bones
Provide PROTECTION to underlying organs
Ex. cranium of skull, ilium of pelvis
Irregular bones
- fulfill multiple roles
- protection and flexibility of motion
- multiple attachments
- often weaknesses (jack of all trades = master of none) –> ex. shoulder
Ex. vertebra, scapula
Superior/inferior
refer to axial skeleton ONLY
superior = closer to head
inferior = closer to pelvis
Medial/lateral
refer to axial skeleton
Proximal/distal
Refer to ONLY appendicular skeleton
proximal = closer to axial skeleton
distal = further to axial skeleton
Anterior/posterior
Refer to BOTH appendicular and axial skeleton
Condyle
A rounded process of a bone that articulates w/ another bone
Epicondyle
a small condyle
Facet
small, flat, smooth surface of a bone that is usually a bearing surface
AXIAL ONLY (2 superior + 2 inferior facets)
Foramen
Hole in a bone through which nerves pass
Fossa
Shallow depression in a bone, usually space for another bone
ex. glenoid fossa in scapula
Process/tuberosity
Raised section of bone, usually for the attachment of a ligament or tendon
Diaphysis
shaft of long bone made of hard cortical bone
Architecture of long bone
- diaphysis
- periosteum: outer lining
- endosteum: inner lining
- medullary canal: hollow middle
- metaphysis
Metaphysis
ends of long bone made of spongy trabecular bone
separated from diaphysis vis an epiphyseal plate of cortical bone
Architecture of short bones
tend to be more like a metaphysis
made of spongy trabecular bone
Architecture of flat bones
tend to be more like a diaphysis
mostly cortical bone with a layer of trabecular bone
Architecture of irregular bones
combo of cortical bone in parts and trabecular bone in other parts
Tension
Muscle pull on bones
