Skeletal integ (Part 1)

What are osteoblasts?

Cells within the bone tissue involved in bone production

What are osteoclasts?

Cells within the bone tissue involved in bone resorption

What are osteocytes?

A bone cell that gives bones their structure

How are bones produced?

Through osteoblasts differentiating into an osteocytes

How are bones resorbed (broken down)?

through osteoclasts destroying osteocytes

How does bone production begin?

Ca and P are transported from the blood vessel into to osteoblast

What happens once Ca and P are in the osteoblast?

Its used to make hydroxyapatite to make bones hard/strong and osteoid (aka collagen)

WHat happens once hydroxyapatite and osteoid are made?

They are transported out of the osteoblast and sit on top it, where they are mixed together and harden as a result (which is called calcification)

What happens after calcification occurs?

Osteoblasts differentiate and into an osteocyte (aka bone cells), which are incased in hydroxyapatite and osteoids as it’ll die if it isn't

How does bone resorption begin?

Enzymes and acid are released from an osteoclast where they breakdown/digest the osteoid and hydroxyapatite respectively, resulting in the osteocyte dying

What happens to hydroxyapatite and osteoid are broken down?

the osteocyte dies and Ca and P are released as result, which are then taken up by the blood vessel

What happens when Ca and P are transported out of the blood during bone production?

it results in the ca and p lvl decreasing in the blood

What happens when Ca and P are transported into of the blood during bone resorption?

it results in the ca and p lvl increasing in the blood

What happens when there is a high blood calcium/phosphate lvl?

• there is a decrease in the parathyroid hormone (PTH)

• which causes an:

  • increase in Osteoblast activity

  • decrease in Osteoclast activity

• resulting in bone production and the Ca/P lvl decreasing toward normal range

What happens when there is a low blood calcium/phosphate lvl?

• there is an increases in the parathyroid hormone (PTH)

  • which causes a

    • decrease in osteoblast activity

    • increase in osteoclast activity

  • resulting in bone resorption and Ca/P lvls increasing toward normal range

How does bone grow?

• bone grows in length and width

  • with long bones only growing in length while all other bones grow in width

Where does bone growth in the long bone occur?

Occur at the growth plate

What are the four zones in bone length growth?

• Zone of resting cartilage

• Zone of proliferation

• Zone of hypertrophy

• Zone of calcification

Why are long bones the only bones that grow in length?

Because they are the only bones with growth plates

What is the zone of resting cartilage?

A zone in bone growth that:

• Contains randomly arranged chondrocytes

• Functions to anchor the growth plate to the epiphysis

What is the zone of proliferation?

A zone in bone growth where Chondrocytes:

• Are arranged in columns

• Release collagen and proteoglycans

• Divide and are pushed into the zone of hypertrophy

What is the zone of hypertrophy?

A zone in bone growth where chondrocytes:

• Enlarge and mature

• Continue to release secrete collage and proteoglycans, along with Ca and P which are all mixed together

• Pushed into the zone of calcification

What is the zone of calcification?

A zone in bone growth where

• Chondrocytes die through phagocytosis by macrophages

  • which creates a voided space where osteoblasts differentiate

How does bone grow in width?

through the adding of osteons to the surface of the bone

What is hematopoiesis?

the process of red blood cell, white blood cell, and platelet production

Where does hematopoiesis occur?

It occurs in the red bone marrow