Transcript Bone Formation, Growth and Remodeling

HORMONE REVIEW
Calcitonin
Gland?
Stimulus?
Cell Activated?
Result?
 1.
 2.
Parathyroid Hormone
Gland?
Stimulus?
Cell Activated?
Result?
 1.
 2.
 3.
HORMONE REVIEW
Calcitonin
THYROID GLAND
High blood Calcium
OsteoBLAST
Result?
 1. Release Calcium in
Urine
 2. Store Calcium in
Bones
Parathyroid Hormone
PARATHYROID GLAND
Low Blood Calcium
OsteoCLAST
Result?
 1. Retain calcium in
Kidneys, do not release
in urine
 2. Absorb calcium from
food in Digestive System
 3. Digest bony matrix to
release stored calcium
in bone
BONE FORMATION,
GROWTH, AND
REMODELING
Ms.Giraldo
BONE FORMATION
 The skeleton is formed from two of the strongest
connective tissues in the body – Cartilage and
Bone.
 Bone formation, also known as ossification,
happens in two stages:
1. Bone matrix completely covers hyaline cartilage
skeleton by bone forming cells called osteoblasts.
2. Hyaline cartilage is then digested away, opening up a
medullary cavity within the newly formed bone.
BONE GROWTH
 By the time of birth most baby’s hyaline cartilage
models have been converted to bone with the
exception of two places-articular cartilages (cover
bone ends) and epiphyseal plates.
 Can anyone assume why these sites stay as cartilage?
 Bone growth is an ongoing active process. Bones
cells are constantly being rebuilt and destroyed by
2 bone cell types:
 Osteoclasts break down bone.
 Osteoblasts form new bone cells in these areas.
BONE GROWTH AND REMODELING
BONE GROWTH
Long Bone Growth
Bone lengthening
Controlled by
 Growth hormones
 Sex hormones during
puberty
Ends during
adolescence.
Appositional Growth
Bone widening
Controlled by
 Activity levels
 Nutrition
 Changes in Exercise
Continues throughout
life
BONE GROWTH AND REMODELING
BONE REMODELING
 Bones are CONSTANTLY remodeling themselves.
Bone is a very active tissue. Osteoclasts and
osteoblasts are always at work.
 Bones must remodel themselves in order to retain
normal proportions as the body grows increasing
in size and weight.
 Bones remodel and change their appearance in
response to changes in 2 factors:
1. Calcium levels in blood
2. The pull of gravity and muscles on the skeleton