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Embed code for: 9. Bones - An Intro
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Bones have 5 main functions:
-Blood cell formation
Bones serve as a series of supports to hold the body together.
ex: Pelvis holds in organs
ex: Legs act as pillars to support weight
The skeleton provides support for vital organs.
Brain - Skull
Heart - Rib cage
Spinal Cord - Spine
-Bones serve as levers pulled
-Each muscle has one or
more sites where it
attaches to bones/tendons
Ex: Supinator attaches to lateral
epicondyle of humerus
Storage - 1
Bone matrix is made of hydroxyapatite (Formula :Ca10(PO4)6(OH)2)
Calcium PhosphorousNote: over 99% of body’s
Calcium ions must be found in blood in small amounts to help nervous system maintain charges in cells
-Bones store extra calcium, release it as necessary
calcium is found in bones
Storage - 2
Chief cells in parathyroid have receptors to detect serum (blood) calcium levels. Normal: 9-10 mg/dL
When there’s not enough calcium in blood (hypocalcemia), chief cells’ receptors detect this and trigger production and release of a hormone called parathyroid hormone (PTH).
When there is enough calcium or there is too much calcium (hypercalcemia), chief cells’ receptors detect this and trigger the halt of PTH production.
This is a negative feedback loop.
Storage - 3
PTH has many functions:
a. it leads to the stimulation of osteoclast activity.
Osteoclasts are bone cells that break down bone matrix (hydroxyapatite), which releases calcium into blood
b. it leads to the inhibition of osteoblast activity.
Osteoblasts are bone cells that build up bone matrix.
c. it leads to the upregulation of an enzyme called of a molecule
called 25-Hydroxyvitamin D3 1-alpha-hydroxylase (don’t learn that), which turns calcidiol into calcitriol (Vitamin D). Vitamin D causes your small intestine to absorb more calcium than normal.
Blood Cell Formation
Production of blood: Hematopoiesis
Red marrow: Produces mostly erythrocytes (red blood cells)
-found mostly in head of long bone
White marrow: Produces mostly leukocytes (white blood cells)
-found mostly in shaft of long bone
All blood cells stem from a cell line called hematopoietic stem cells, which
can partially regenerate.
The skeleton has
two main parts:
runs down the middle
skull, vertebral column, thorax
branches off the middle
limbs, pelvic girdle, shoulder girdle
We will look closer at these bones next lecture!
Negative Feedback Loop- when everything goes back to normal and the PTH production is stopped
c. Take the dna and turn it to rna and then take rna and make it a protein but the process is happening way much faster
25-Hydroxyvitamin D3 1-alpha-hydroxylase BONUS QUESTION
Vitamin D causes the si to absorb more calcium than normal when the body is low on calcium and is in need of every calcium provided
Bomes are responsible for forming blood
Bones are hollow and are formed of two marrows: red marrow, and white marrow
Red Marrow produce red blood cells, and are found in the head bc long bones there
White Marrow: produce white blood cells, shaft of long bone
Cells have to turn into some kind of blood cells