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