Homeostasis in the

skeletal system

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)

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.

Homeostasis

Ca+ regulation is controlled by negative feedback systems.

Homeostasis

When blood calcium levels are too low the parathyroid will release parathyroid hormone (PTH) resulting in:

1. Increased osteoclast activityreleasing Ca+ from the bone intothe blood(major way).

Homeostasis

2. kidneys will decrease theamount of Ca+ released in theurine.

3. Increased vitamin Dproduction in the skin whichwill increase absorption of Ca+

from food.

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.

Homeostasis

Bone growth:

Regulated by Human Growth Hormone (HGH) secreted by anterior pituitary gland at the base of the brain.

HomeostasisBone 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.

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.

HomeostasisBone 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.

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.