Supportive text for this material is in Kardong pgs & You will be responsible for this content… make sure you know the vocabulary Skeletal System

Functions: Support Protection Movement Storage Blood cell production 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 CartilageLigaments Tendons Are bones dead? What components comprise the skeletal system?

How does cartilage relate to the skeletal system?!? Origin, growth and repair depend on hyaline cartilage! ChondroblastsChondrocytes LacunaePerichondrium FibroblastsBlood 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 ~ Ca 10 (PO 4 ) 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 A No collagen B No minerals What are the histological features of bone?

Types of bone cells: (Most likely to have “osteo”) Osteogenic Cells from endosteum and inner periosteum Osteoblasts Cells forming matrix Osteocytes Cells “trapped” in matrix Osteoclasts Multinucleated cells “remodel” matrix What are the histological features of bone? Stem Cells Osteochondral 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 fontanels How 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?

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 growth Stimulates 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: Calcitonin minor 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 Calcitonin minor 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?