Skeletal System, Part 1, Calcium Homeostasis, Locklin

Hematopoiesis

Blood production takes place in the red bone marrow. There are two kinds of production, erythropoiesis and leukopoiesis.

Hydroxyapatite

Bone salts form a crystalline pattern or structure. It makes the bones very hard and rigid.

Bones

206 bones in the body that can be put into 1 of 4 categories based on shape.

Bone salts

85% calcium phosphate Ca3(PO4)2, 10% calcium carbonate CaCO3 and then about 5% are going to be other materials in small quantities. They form a crystalline pattern of structure called hydroxyapatite.

Endosteum

A membrane inside of bones, a single layer of cells that includes osteoblast and osteoclast. It is found in a tissue called reticular tissue and it makes up the membrane that lines the medullary cavity, spongy bone in that cavity is inside of this membrane.

PTH action 1

After it is released from the Parathyroid glands, it binds to receptors located on cells called stromal cells. Stromal cells respond by producing a molecule called RANKL. RANKL then binds to receptors on the surface of an osteoclast precursor which stimulates it to become a full blown osteoclast. That osteoclast is going to remove calcium from the skeletal system and put it into the blood when blood calcium levels go low, hypocalcemia.

Compact

All bone is __________ on the outside. It has the haversian systems for the osteons. It is very dense and it is very protective and it is very hard to break. On the inside is spongy bone.

Ca functions

Ca ions initiate muscle contractions and play a role in stopping contractions.

2.2 to 4.4

How many lbs. of calcium that a typical human body contains, 99% of that amount is being stored in the skeletal system.

RANKL

It is a molecule that binds to a receptor on the surface of an osteoclast precursor which stimulates it to become a full blown osteoclast. Receptor for the Activation of Nuclear factor Kappa b Ligand.

Ca functions

It is involved in releasing neurotransmitters from neurons. Neurotransmitters are how neurons communicate with each other.

Calcitonin

It is released from the thyroid gland when the blood level of calcium is too high. It is a hormone that is going to decrease the osteoclast activities by binding to their membranes, so it basically inhibits their activity so bone breakdown is going to decrease. This hormone also increases calcium uptake by the bones and it accelerates calcium deposition into these bones.

Epiphysis

is the head of the bone, the end of the bone.

Bone types

Long bones, flat bones, short bones and irregular bones.

Parathyroid hormone

PTH, It is released from the Parathyroid glands when blood calcium drop below 9 mg. 1. After it is released it binds to receptors located on cells called stromal stem cells that then produce RANKL which work to stimulate creation of osteoclasts. 2. It also acts on kidneys to decrease Ca loss in the urine. 3. It stimulates the formation of a hormone called calcitrol. Calcitrol produced in the kidneys and it promotes the absorption of calcium in the small intestines.

Ca functions

Plays major role in initiating action potentials or nerve impulses.

Diaphysis

Shaft of the bone.

Skeletal functions

Support, protection, movement, hematopoiesis, and storage.

Collagen fibers

These are also found in the bone matrix and they also give the bones their toughness and a little bit of elasticity. This allows the bones to break and not shatter.

PTH action 2

This hormone is going to act on the kidneys to decrease the loss of calcium in the urine so that more calcium is retained in the blood when blood calcium levels go low, hypocalcemia.

PTH action 3

This hormone is going to stimulate the formation of a hormone called calcitrol. Calcitrol is a hormone that is produced in the kidneys and promotes the absorption of calcium in the small intestines to remedy low levels of calcium in the blood.

Epiphyseal plate

This is the growth plate, this is how bones get longer.

Parathyroid

When blood calcium levels drop below the set point then PTH is released from this gland.

Storage

a function of the skeletal system, nutrients, tissues, bone salts and fats are in medullary cavity in long bones.

Calcium Homeostasis

blood level calcium needs to be maintained between 9 to 11 mg of calcium per 100 ml of blood. set point.

Short bones

bones in the wrist or hand as an example. These bones are cube shaped. They are about as wide as they are long. Good location for a lot of hematopoiesis on the inside, lots of spongy bone inside. carpals and tarsals are short bones, phalanges are long bones.

Flat bones

bones of the skull, the occipital bone, the parietal bone, and the frontal bone. There is spongy bone between layers of compact bone. They are relatively broad, they are flat and they have a thin area of spongy bone surrounded by thin layers of compact bone.

Wormian bones

bones that some people have that begin extremely small and grow together, small bones in the sutures at the back of the skull. These are highly genetic.

Osteoclasts

breakdown bone tissues, calcium is removed from the bone and put into the blood.

Osteoblast

builds bones, they build bone tissue and calcium is added to the bone and removed from the blood.

Ca functions

enzymes require it additional for enzymatic reactions to take place.

Long bones

have long central axis. They are longer than they are wide. They have epiphysis and diaphysis, periosteum, endosteum, medullary cavity, articular cartilage and epiphyseal plate.

Articular cartilage

hyaline cartilage, it is called _________ cartilage because there is a bone on the outside of the end of that bone rotating or moving around it. It allows for a pad of cartilage between bones that acts as a shock absorber, prevents bone to bone contact.

Calcium

important for bone growth and bone development, bone health. It is being stored in the skeletal system but not necessarily just to make the bones stronger. If the body needs it for other reasons, it can take it out and use it in those other places.

Ca levels

in the blood have to be closely maintained to prevent damage to essential physiological systems. ex. Ca ions play an important role in muscle contractions.

Ca ions

initiate muscle contractions and play a role in stopping contractions.

Calcium movement

into and out of the bone is what regulates calcium blood levels, it is what keeps it at its particular range.

Calcitrol

is a hormone produced by the kidneys and it promotes the absorption of calcium in the small intestines.

Medullary cavity

is in the diaphysis of the long bone. It is surrounded by spongy bone. This cavity is full of adipose tissue and fat. It makes the bone a lot lighter. It is lined by endosteum.

Periosteum

is the dense irregular connective tissue, it is shown as the outer cover of the bone.

Erythropoiesis

is the production of red blood cells.

Leukopoiesis

is the production of white blood cells.

Skeletal System

it includes bones, and tissues and cartilages, ligaments, joints, lots of organs and tissues in this particular system.

Hypercalcemia

it is where there is too much calcium in the blood, when it is above 11 mg for the set point.

Axial skeleton

it would include the skull, the thoracic cavity like the ribs and the vertebral column, everything down the main axis down to coccyx. It doesn't include the pelvic or scapula and clavicle.

Hypocalcemia

low blood calcium levels

Stromal stem cells

produce a molecule called RANKL after PTH binds to these cells receptors or membrane.

Irregular bones

shape of sphenoid bone, vertebrae, mandibles or ethmoid bones in the skull as well.

Sesamoid bones

these are rounded smooth bones that fit into joints and usually aid some way in movement. These develop in tendons where a lot of friction, a lot of tension, a lot of stress takes place. They are seen sometimes in the hands or the feet. Sometimes they do not completely turn into bone. Patella is one of these.