1. Homeostasis in the
skeletal system

2. Homeostatis
Calcium levels in the blood must
be maintained within a certain
range or it can be dangerous to the
body.
Normal Range: 9.0–10.5 milligrams
of Ca+ per deciliter (mg/dL)

3. Homeostasis
Calcium levels in the blood are
controlled by the endocrine
system.
Two organs located in the neck
responsible for calcium regulation
are the thyroid and parathyroid.

5. Homeostasis
Ca+ regulation is controlled by
negative feedback systems.

6. Homeostasis
When blood calcium levels are too
low the parathyroid will release
parathyroid hormone (PTH) resulting
in:
1. Increased osteoclast activity
releasing Ca+ from the bone into
the blood(major way).

7. Homeostasis
2. kidneys will decrease the
amount of Ca+ released in the
urine.
3. Increased vitamin D
production in the skin which
will increase absorption of Ca+
from food.

8. Homeostasis
When levels of calcium have
increased or are too high osteoclast
activity is slowed by:
1. Less PTH being released
2. The thyroid secreting calcitonin
which decreases osteoclast activity
as well.

9. Homeostasis
Bone growth:
Regulated by Human Growth
Hormone (HGH) secreted by
anterior pituitary gland at the
base of the brain.

10. Homeostasis
Bone growth:
Dwarfism – a condition in which a
person is much smaller than an
average human due to too little HGH
production by pituitary gland as a
child.

11. Homeostasis Bone growth:
Gigantisms – a condition in which a
person is much larger than an
average human due to too much
HGH production by pituitary gland as
a child.

12. Homeostasis
Bone growth:
Gigantism
As an adult overproduction of HGH
will cause the epiphyseal line to
thicken, thicken the bones. Seen in
the eyebrows being very thick.

13. Homeostasis Bone growth:
Estrogen and testosterone are two
other hormones affecting bone
growth:
a. They will stimulate bone growth
resulting in a growth spurt at puberty.
b. Then they will stimulate the
epiphyseal plate to ossify stopping
bone growth after puberty.