5.2 Ossification

Question 1

Prefix “os-“

Answer 1

Bone

Question 2

Ossification means

Answer 2

The production of bone

Question 3

Two types of ossification

Answer 3

Intramembranous & Endochondral

Question 4

Intramembranous ossification

Answer 4

• from Mesenchyme to bone tissue
• starts early fetal to age 2 yo
• Most bones in the skull (flat bones),
  & clavicles

Question 5

Fontanels

Answer 5

Soft spot after birth in skull (pliable)

Question 6

Endochondral ossification

Answer 6

• from Mesenchyme to cartilage (hyaline) then bone
• completes end of puperty

Question 7

Steps of Endochondral ossification

Answer 7

• plug of hyaline cartilage (mostly water with protein)
• becomes infiltrated from outside layer (periosteum) with osteocytes
• forms primary ossification center
• bone takes over, cartilage persists
• secondary ossification centers form

Question 8

Epiphyseal plate

Answer 8

• aka “growth plate” where we grow.
• the line where cartilage expands/persists as ossification expands with it.

Question 9

Endochondral ossification regulated by

Answer 9

Several hormones (endocrine system)
- growth hormone (GH) (expansion of cartilage and epiphyseal plates) from pituitary
- parathyroid hormone (PTH) removes extra bone tissue so they don’t get too thick (maintains proportions)
- sex horomones (last expansion) forming epiphyseal lines

Question 10

Short bones arise from

Answer 10

Single ossification center

Question 11

Irregular bones arise from

Answer 11

Distinct various ossification centers

Question 12

Long bones arise from

Answer 12

Primary and 1+ secondary ossification centers

Question 13

Osteoclasts

Answer 13

• stimulated by PTH cause osteoclasts to release HCl (which dissolves calcium/ bone tissue) aka resorption

Question 14

Resorption is

Answer 14

Process of removing bone tissue

Question 15

Blood calcium levels

Answer 15

• regulated by negative feedback loop
• if low, PTH released, tells kidneys to maintain Ca2+
• also triggers osteoclasts to produce HCl and release Calcium from bones

Question 16

Osteoporosis

Answer 16

• degradation from Ca deficit