Bones

hypocalcemic

decrease blood levels of calcium

Axial skeleton

skull, vertebral column, rib cage

organic matrix of bone (known as osteoid)

65% is inorganic matrix (minerals; ex. hydroxyapatite crystals) 35% is organic matrix (collagen fibers are most predominant). Helps to resist torsion (twisting) and tensile (pulling or stretching) forces. Helps with strength as well.

PTH (parathyroid hormone)

A peptide hormone that increases blood calcium concentrations and therefore is hypercalcemic.

bone deposition

Action of osteoblasts and calcitonin. *new bone is formed.

Osteoclasts

Bone-destroying cells, break down bone matrix for remodeling and the release of calcium.

Concentric lamellae

Circular layers of bone matrix that surround the central canal?

Canaliculi

Hairlike canals that connect lacunae to each other and the central canal

Trabeculae

Identify the highlighted structures.

hypercalcemic

Increases blood calcium level

spongy bone

Layer of bone tissue having many small spaces and found just inside the layer of compact bone.

Calcitonin

Lowers blood calcium levels, therefore is hypocalcemic. Secreted by thyroid gland. It increases bone deposition by stimulating osteoblasts and inhibiting osteoclasts.

Osteocytes in compact bone

Major, mature bone cells derived from osteoblasts that become buried in bone after it is formed. Function to maintain the matrix.

What are the major bone cells?

Osteoprogenitor cells Osteoblasts Osteocytes Osteoclasts

endochondral ossification

Process of transforming cartilage into bone.

Perforating (Volkman's) cannals or channels

Run perpendicular to the central canals. They help connect the blood vessels and nerves that pass through the central canals.

Lacunae

Small spaces between the lamellae which contain osteocytes

epiphyseal vessels

Supply nutrients to the cavities of the epiphysis

Central canal

The hollow center of an osteon, also known as a Haversian canal. The central canal contains blood vessels, lymphatic vessels, lymphatic vessels, and nerves. Bone is laid down around the central canal in concentric rings called lamellae.

appendicular skeleton

The portion of the skeleton that attaches to the axial skeleton and has the limbs attached to it

Osteon

The unit of combact bone, also called a Haversian system. Osteons are essentially long cylinders of bone; the hollow center is called the central canal, and is where blood vessels, nervs, and lymphatic vessels are found. Compact bone is laid down around the central canal in rings (lamellae).

Vitamin D effect of Calcium Homeostasis

Vitamin D acts mainly on the intestines, where it promotes calcium ion absorption, and on the kidneys, where it prevents loss of calcium ions to the urine. The net effect of vitamin D on bone is to increase bone deposition and bone mass. Vitamin D is a steroid synthesized by the body in response to exposure of the skin to UV light. Hypocalcemic

Osteocytes

a bone cell, formed when an osteoblast becomes embedded in the matrix it has secreted.

what is the source of the growth hormone

anterior pituitary gland

nutrient vessels

blood vessels that penetrate bone to supply it with nutrients

Osteoblasts

bone-building cells that secrete matrix

Insulin-like growth factors

during childhood, it promotes growth at epiphyseal plate; production stimulated by human growth hormone

name hormones involved in bone growth

growth hormone, IGF (Insulin like growth factor), Calcitonin, parathyroid, Vitamin D, Testosterone, Estrogen.

interstitial growth

growth in length

appositional growth

growth in width

how does growth hormone help bone growth?

increases rate of cell division, increases activity in osteogenic cells and directly stimulates osteoblasts

concentric lamellae

layers of bony matrix around a central canal

circumferential lamellae

located deep to periosteum and superficial to endosteum and extend around entire circumference of the diaphysis and resist twisting of long bone

Classification of bones

long, short, flat, irregular

bone cells

osteoblasts, osteocytes, osteoclasts

What triggers PTH release?

parathyroid gland cells detect a low blood Ca 2+ level.

intramembranous ossification

process by which bone forms directly from mesenchymal tissue

testosterone and estrogen

promote adolescent growth spurts, end growth by inducing epiphyseal plate closure. Testosterone increases appositional growth. Estrogen increases interstitial growth.

interstitial lamellae

remains of old osteons that broke down as bone grew and remodeled itself

osteoprogenitor cells

stem cells derived from mesenchyme

bone resorption

the breakdown of bone extracellular matrix by osteoclasts that is part of the normal development, maintenance, and repair of bone tissue. *old bone is destroyed.

Hydroxyapatite crystals

the chief crystal of bone, formed from calcium and phosphorus. Gives bone ist strength and ability to resist compression.