Supportive text for this material is in Kardong pgs.

145-152&

177-186

You will be responsible for this content… make sure you know the vocabulary

Skeletal System

Functions:

• Support

• Protection

• Movement

• Storage

• Blood cell

production

http://www.art.net/~rebecca/LifeDrawing2.html

What types of animals DON’T have osseous skeletons?

List some examples of organs protected… Do all movements rely on skeletal system?

What types of elements are most likely stored in bone?

What does the skeletal system have to do with blood cells?

Skeletal System

Bones

Cartilage Ligaments

Tendons

Are bones dead?

What components comprise the skeletal system?

http://www.art.net/~rebecca/LifeDrawing2.html

How does cartilage relate to the skeletal system?!?

Origin, growth and repair depend on hyaline cartilage!

Chondroblasts Chondrocytes

Lacunae Perichondrium

Fibroblasts Blood vessels

Cartilage growth occurs in 2 regions…

1) Periphery via perichondrial cell division and matrix deposition

Appositional growth

Interstitial growth

2) Internally via chondrocyte division and matrix deposition

Mary, Mary quite contrary how does your cartilage grow?!?

Explain why damaged cartilage takes a long time to heal. Why doesn’t articular cartilage have a perichondrium, blood vessels, or nerves?

Take 5!!!

Discuss with your neighbor and predict

an answer.

Consist of 2 primary regions

Epiphyses

Diaphysis

The ends of longs bones, primarily cancellous bone

The shaft of long bones, primarily compact bone

What are the anatomical structures of long bones?

Cartilage (hyaline) plate between 2 regions plays special role!!!

Epiphyseal plate

The cartilage grows and becomes osseous tissue.

Why wouldn’t you want growth here as an adult?

What are the anatomical structures of long bones?

What is a good term for the membrane “around” the “bone” ?

Periosteum

2 layers, contains blood vessels & nerves

Single layer of cells lining medullary cavity and cancellous spaces

Endosteum

What are the anatomical structures of long bones?

Marrow

Types:Red

Yellow

Distribution:Flat bones

Long bones

Site of blood cell formation

Mostly lipids, energy storage

Location of red marrow

Location of yellow marrow

What are the anatomical structures of long bones?

Flat

Short

Irregular

“Cancellous sandwich”

no “dia” or “epi” physes

Would you expect diaphysis?

No diaphysis, small epiphyses possible

What are the anatomical features of flat, short and irregular bones?

Looking at this tissue… it is mostly matrix

Mostly (65%) inorganic Hydroxyapatite~ Ca10(PO4)6(OH)2

Organics are collagen and proteoglycans (35%)

What are the histological features of bone?

Of the 2 components: fibers (=1) vs. Crystals (=2) Which type are missing from these bone A?

Which type are missing from B?

Normal long bone

ANo collagen

BNo minerals

What are the histological features of bone?

Types of bone cells:(Most likely to have “osteo”)

OsteogenicCells from endosteum and inner periosteum

OsteoblastsCells forming matrix

OsteocytesCells “trapped” in matrix

OsteoclastsMultinucleated cells “remodel” matrix

What are the histological features of bone?

Stem CellsOsteochondral progenitor cells

Bone is classified depending on the arrangement of cells and matrix.

Woven ~ Collagen fibers are randomly arranged

Lamellar ~ Collagen fibers are arranged parallel

What are the other categories of bone besides the shapes (ex. Long, irregular etc.)?

Types:

Cancellous (spongy)

~ Network of mineralized bone (Trabeculae) with many spaces

~ Marrow fills up these spaces in life

What are the other categories of bone besides the shapes (ex. Long, irregular etc.)?

Types:

Referring back to our discussion of striae and collagen fibers, what direction do you suppose the trabeculae align in relation to stress?

Types:

Cancellous (spongy)

Compact ~ Dense lamellar bone that is mineralized (mature) with numerous units (osteons) arranged around blood vessels

Compare this photomicrograph to

the diagram and locate the listed structures

What are the other categories of bone besides the shapes (ex. Long, irregular etc.)?

Types:

Compact bone has a specialized canal system for the transport of nutrients and waste products. Why isn’t such a system necessary in cancellous bone? Why not hyaline cartilage?

Take 5!!!

Discuss with your neighbor and predict

an answer.

2 patterns of ossification:

Intramembranously

Endochondrally

Note: Both types start as woven bone, which is remodeled as it matures into lamellar bone

Originally connective tissue membrane

Originally cartilage that is ossified

How does your bone grow?

Intramembranous Ossification

• Occurs during fetal development and “finishes” by 2 years of age

• Woven bone fibers connect and thicken forming trabeculae (cancellous bone)

• Outer layer of osteoblasts create outer layer of compact bone

fontanelsHow does your bone grow?

Endochondral Ossification

How does your bone grow?

• Occurs during fetal development and “finishes” by “20-something”• Hyaline cartilage model formed• Presence of blood vessels on periphery stimulates osteochondral progenitor cells to become “osteos” rather than “chondros”• Internal chondrocytes die and are replaced by vessels and osteo cells

• Hyaline cartilage model formed… everything is “chondro”

• Blood vessels invading perichondrium stimulate osteogenic cells to become osteoblasts

• Perichondrium now becomes periosteum

• New osteoblasts form bone collar

How does your bone grow?Endochondral Ossification

• Buds of connective tissue from periosteum invade cartilage model. Bring in osteogenic cells.

• Osteoblasts form bone as medullary cavity enlarges

Then what happens?

• Bone growth progresses towards the ends medullary cavity enlarges

How does your bone grow?

• Osteoblasts form bone in Secondary ossification center, beginning of epiphysis

How does your bone grow?

• When bone is mature epiphyseal plate is ossified and becomes epiphyseal line

How does your bone grow?

During endochondral ossification, calcification of cartilage results in the death of chondrocytes. Later in the process, ossification of the bone matrix does not result in the death of osteocytes. Why is this so?

Take 5!!!

Discuss with your neighbor and predict

an answer.

We’ve talked about bone growth in length… what about diameter?

Can bone display interstitial growth?

• Appositional deposition and resorption

How does your bone grow?

How does your bone grow?

Factors affecting bone growth:

• Nutrition Proteins Vitamins D & C

• Hormones Growth hormone Thyroid hormone Sex hormones

Needed for organic portion of matrix

Needed for Ca absorption and Collagen formation

Stimulates overall growthStimulates bone growth and works with GH

Stimulates bone growth BUT also closure of epiphyseal plate

How does your bone grow?

Ca and P homeostasis

Calcium: needed for nerve cell action, muscle contraction, blood clotting and more

Phosphorus: needed as a component of ATP, DNA and RNA

Why are these elements important?

How does the Skeletal System regulate Ca & P?

Ca and P homeostasis regulated in part via 2 hormones:

Calcitoninminor role… secreted by thyroid gland

PTH (parathyroid hormone)comes from parathyroid glands

How does the Skeletal System regulate Ca & P?

PTH+PTH = +blood Ca

via bone, intestine and kidney activities

Calcitoninminor role…

+Calcitonin = -blood Ca

How does the Skeletal System regulate Ca & P?

Which “osteo” cells do you suppose this hormone stimulates to cause a reduction in blood Ca levels?