skeletal system: bone minerals, growth and joints Flashcards
what is a common injury
ligament or tendon tear
when do bones grow
fetal development, growing up, bone remodeling, fracture repair, yearly replacement (5-10% of bones)
in an embryo the skeleton starts as what
hyaline cartilage and fibrous connective tissue
what is intramembranous ossification
when cells of fibrous connective tissue differentiate into various bone forming cells
what are the 2 types of bone growth
longitudinal and appositional
how does longitudinal growth work
- chondrocytes just under the side of the epiphyseal plate form the proliferation zone + divide rapidly, new cells being formed push the epiphysis away from the diaphysis
- older chondrocytes die off and the extracellular matrix calcifies + degrades, blood vessels invade the place
- osteoblasts + osteoclasts work to replace the former cartilage tissue w/ new bone
how does appositional growth work
- osteoblasts found in the periosteum lay down more extracellular matrix on the outer surface of the bone (called bone deposition)
- osteoblasts breakdown some bone on the inside of the medullary cavity (called bone resorption)
- a deposition will outpace resorption so bone grows outwards
what is bone remodelling
constantly replacing older bone with new bone tissue, balance between bone resorption and bone deposition
what are the 2 reasons for bone remodelling
- calcium homeostasis: the body needs a constant concentration of ca in the blood to keep cellular processes working
- maintaining bone strength: extracellular matrix of old bone tissue is more brittle and needs to be replaced, forces applied to bones may require bones to be strengthened
how is bone remodeling regulated
by hormones and mechanical forces acting on the bone
what do hormones determine in bone remodeling regulation
whether remodeling happens and when it happens
what does mechanical stress determine in bone remodeling regulation
where it happens
what is the process of hormonal regulation for Ca homeostasis when Ca levels are decreased
- Ca levels drop
- chemoreceptors detect the drop in Ca
- the parathyroid gland secretes parathyroid hormone (PTH) into the blood
- PTH stimulates osteoclasts to resorb bone
- Ca is released into the blood
what is the process of hormonal regulation for Ca homeostasis when Ca levels are increased
- Ca levels increase
- chemoreceptors detect the increase in Ca
- the thyroid gland secretes calcitonin into the blood and kidneys excrete Ca
- calcitonin inhibits osteoclast bone resorption
- Ca levels decrease
what is wolff’s law
a bone grows or remodels wherever it needs to in order t compensate for the stresses placed on it
what is a bone stress
gravity (weight), muscle pull
what is the function of a joint
to connect bones together
what are the 3 types of joints
fibrous, cartilaginous, synovial
what are fibrous joints
bones connected by collagen fibers
what is the function for fibrous joints
allows for very little or no movement
what are cartilaginous joints
bones connected my cartilage
what is the function of cartilaginous joints
provides little or no movement
what is a synovial joint
a joint with a cavity that separates connected bones, the cavity is filled with synovial fluid, most joints in the body are synovial joints
what is the function of a synovial joint
allows for lots of movement
what are the 6 structural features of a synovial joint, explain each one
- cartilage: on the ends of the 2 bones where they come in contact
- joint capsule: covering where 2 bones meet , made of fibrous connective tissue, keeps bones from separating, lined with synovial membrane
- synovial fluid: lubricates to reduce cartilage degradation from friction
- joint cavity: holds synovial fluid
- ligament: attaches bone to bone
- nerves + blood vessels: nerves monitor pain and stretch and blood vessels nourish the synovial membrane
what is a synovial membrane
what secretes the synovial fluid
what is a bursae
flat bags made of synovial membrane, contains synovial fluid, the function is to reduce friction
what is a tendon sheath
like a bursae but wrapped around a tendon, contains synovial fluid, the function is to reduce friction
what is a tendon
attaches muscle to bone
