Bone Physiology
What are the steps if blood calcium levels decrease?
1. Stimulus - blood calcium level decreases 2. Receptors - Parathyroid gland cells sense the decrease in blood calcium 3. Control Center - Parathyroid glands release parathyroid hormone 4. Effectors - Osteoclasts break down bone to release calcium
What are the steps if blood calcium levels increase?
1. Stimulus - blood calcium level increases 2. receptors - cells in the thyroid gland sense the increase in blood calcium 3. Control Center - Thyroid gland releases calcitonin 4. Effectors - osteoblasts deposit calcium in bones
Sunlight contacting the epidermis converts ____________ to vitamin D₃, otherwise known as cholecalciferol.
7- dehydrocholestrol
In the kidneys, PTH also promotes the formation of active vitamin ____________ .
D
Articular cartilage, found on the ends of long bones, consists of
hyaline cartilage
Lack of sunlight will directly affect the formation of
Vitamin D3 (cholecalciferol).
The storage or release of buffering compounds works to aid the body in ____________ .
acid base balance
endochondral ossification
begins with a hyaline cartilage model
contained within the spongy sections of bones, marrow is responsible for _______
blood formation
bone modeling is important for
bone growth, changes in body shape, and adjustment to physical stress
Mineralization is a process that extracts ____________ from the blood plasma and deposits it into bone.
both calcium and phosphate
Parathyroid hormone increases the renal conversion of ____________ , which secondarily works to increase calcium levels in the blood.
calcidiol to calcitriol
Osteoclasts are inhibited by ____________
calcitonin
what decreases blood calcium levels?
calcitonin, osteoblastic activity and increased use of sunblock
Calcidiol returns to the blood once again where transport to the kidneys then allows the final conversion to
calcitriol
Active vitamin D increases ____________ absorption from the small intestine.
calcium
Depositions of collagen and fibrocartilage will then turn the tissue into a soft ____________ .
callus
Transported via the blood to the liver, ____________ is converted to calcidiol.
cholecalciferol
the organic part of the matrix of bone
collagen, glycosaminoglycans, proteoglycans, and glycoproteins
The decline in bone breakdown and increased mineralization causes blood calcium to ____________ back to normal levels.
decrease
When levels of blood calcium ____________ , parathyroid hormone is released from the four nodular parathyroid glands located on the posterior thyroid.
decrease
Elongation of bones through endochondral ossification requires the zone of reserve cartilage where normal ____________ cartilage persists in the metaphysis.
hyaline
Minerals can be stored in the skeleton which acts as a reservoir, storing or releasing minerals as needed to maintain ____________ throughout the body
electrolyte balance
Calcitonin
encourages calcium deposition from blood into bone
Any break in a bone is called a ____________ and repair is done in stages by the body.
fracture
The anterior pituitary gland secretes ____________, which stimulates the formation of _______________
growth hormone; somatomedin
A ____________ will form and will turn into granulation tissue at the site of injury.
hematoma
inorganic part of bone
hydroxyapatite crystals, calcium phosphate salts, calcium carbonate salts, other salts, magnesium, fluoride
As a result of direct actions on the target cells of the bone and kidneys along with an indirect action on the small intestine (calcitriol), parathyroid hormone works to ____________ blood calcium levels.
increase
Now in the most active form, calcitriol acts to ______ blood calcium by acting on three target organs: 1) small intestines 2) skeleton, and 3) kidneys
increase
The effects on osteoclasts cause a decrease in bone resorption and a concurrent ____________ in bone deposition due to osteoblasts.
increase
When levels of blood calcium ____________ , calcitonin is released from the C cells of the thyroid gland.
increase in children
In the kidneys, PTH ____________ calcium reabsorption from the urine.
increases
Mechanical stress applied to bone __________ osteoblast activity in bone tissue, and the removal of mechanical stress __________ osteoblast activity
increases ; decreases
thyroid hormone
influences the basal metabolic rate of bone cells
This circulating calcitonin ____________ within minutes.
inhibits osteoxlasts and stimulates osteoblasts
The ____________ of the entire skeleton or skeletal elements utilizes the anchoring of muscles to attachment sites on the bones which then serve as levers.
movement
intramembranous ossification
ossification that develops from mesenchyme
A temporary bony collar is deposited by ____________ around the fracture while ossification occurs.
osteoblasts
Bone cells that remove calcium from the blood to make bone are ____________ .
osteoblasts
During the healing of a bone fracture, a hard callus is formed by
osteoblasts
Inhibition of ____________ by parathyroid hormone occurs as a result of a decreased production of organic matrix.
osteoblasts
What increases blood calcium levels?
osteoclastic activity, calcitrol, parathyroid hormone, and increased bone resorption
Parathyroid hormone causes an increase in the number of ______ and greater rates of bone resorption.
osteoclasts
bone remodeling
osteoclasts are involved, Bone remodeling is a combination of bone deposition and resorption. Bones are remodeled to accommodate the stresses put on them.
The hormone that indirectly stimulates osteoclasts to break down bone and release calcium into the blood is ____________ hormone.
parathyroid
The skull, pelvis, ribs, vertebral column, and sternum provide ____________ to many delicate organs of the body by encasing them in hardened shell-like or caged structures.
protection
At the level of the kidney, parathyroid hormone will decrease the amount of calcium excreted by increasing ____________ from the kidney tubules.
reabsorption
The process finishes with bone ____________ converting spongy to compact bone.
remodeling
Bone remodeling is important for all of the following reasons except
sodium ion regulation
parathyroid hormone
stimulates osteoclasts to resorb bone and increase blood calcium
The bones of the skeleton provide structure to the body and serve as a ____________ to hold up the body and maintain proper positioning of some organs.
support
Mineralization of the cartilaginous walls between lacunae provides a temporary framework in the ____________ by which the final stages of ossification will take place
zone of calcification
The ____________ demonstrates the area where the chondrocytes die and are replaced by blood vessels and osteoblasts, which then form the final trabeculae and osteoclasts that refine the distal contours of the medullary chamber.
zone of deposition
The next layer is the ____________ where the existing, columnar chondrocytes enlarge and thus force the separations between lacunae to become very thin
zone of hypertrophy
Nearer to the medullary cavity, the ____________ is marked by an expansive production of chondrocytes that align in rows in order to replenish those undergoing calcification.
zone of proliferation