Chapter 6: Skeletal System

Chapter 6: Skeletal System • Support • Protection • Movement • Storage • minerals • Blood cell production • Bone marrow – makes blood cells/platelets Functions of the Skeletal System

Figure 6.1 Bones = Connective Tissue

Bone, cartilage, tendons, ligaments • 3 parts (extracellular matrix) • Collagen • Ground substance (proteoglycans) • water Connective Tissue

Bone Composition • Hydroxyapatite = Calcium and phosphate crystals • hard • collagen • Flexible • strong Connective Tissue Are bones flexible??

Makes bones hard! • Apatite is a group of phosphate minerals in crystal form. Hydroxyapatite = phosphorous and calcium bone matrix

1. What would a bone be like if all mineral was removed? 2. What would it be like if all of the collagen was removed? Any diseases come to mind??

1. What would a bone be like if all mineral was removed? 2. What would it be like if all of the collagen was removed? Any diseases come to mind?? Osteoperosis Brittle Bone Disease: Autosomal dominant collagen disorder.

Case in Point: Osteogenesis Imperfecta • May Trix – 10 yr girl – history of broken bones • Child abuse? • No – has imperfect bone formation • Short for her age • Limbs are short, bowed • Curved vertebral column Brittle Bone Disease (rare) -not enough collagen/poor collagen -decreased flexibility of bones -easily broken bones

Osteogenesis imperfecta

Cells • Osteoblasts – cells that build bone • Osteocytes – cells that maintain bone • Osteoclasts – cells that breakdown bone Connective Tissue

General Bone Features • 2 types of bone • Compact (dense) • Cancellous (spongy)

Compact Bone = dense • Location • diaphysis (long bones) • Thin surface (others) • Blood vessels in compact bone • Nutrients/wastes • Connected to periosteum blood vessels

Cancellous Bone = spongy • Location • Most – epiphyses (long bones) • Interior (others) • Delicate connected rods/plates = trabeculae • Strength without weight • Each trabeculae made of many lamellae with osteocytes • no blood vessels

General Bone Features • Long bones = longer than they are wide • Short = approx. as broad as they are long • Flat = thin, flattened shape • Irregular = shapes that don’t fit into other categories

General Bone Features • Long bone • Diaphysis (shaft) • Medullary cavity - hollow • Epiphysis (ends) • articular cartilage covers ends (lowers friction) • Epiphyseal plate (growth plate) • Cartilage • Between epiphysis and diaphysis • Replaced by bone with age and called epiphyseal line

General Bone Features • Cavities • Medullary cavity (long bone) • Filled with red or yellow marrow • Marrow = soft tissue • Red – more blood forming cells • Kids have more • Yellow marrow – fatty • Adults have more

Figure 6.2a

Figure 6.2b

General Bone Features Outside/Inside of bones • Most of outer surface of bones covered by periosteum • Connective tissue • Contain blood vessels/nerves/osteoblasts • Endosteum – covers inside of cavities • Contain osteoblasts

General Bone Features Structure • Bone is formed in thin sheets of extracellular matrix = lamellae • Osteocytes in small places between sheets (lacunae) • Canaliculi - tunnels connect cell • Cell processes take place in canaliculi

Seville Giants -tallest man in history Shoe size = 37 @ 22 = 8 ft 11 in “when he was thirteen and became the largest Boy Scout in history – he was seven feet, one inch and weighed 340 pounds. “ *What causes this???? *What part of the bone is affected?

Giantism • Gland secretes too much growth hormone • Continues to stimulate growth plates (osteoblasts)

Child growth • occurs in growth plate (epiphyseal plate) • Cartilage • More red marrow • Osteoblasts • Stimulated by growth hormone • Adult • Growth stops (epiphyseal lines) • Cartilage turns to bone • More yellow marrow Bone Growth - Length

Bone Growth • Length • Osteoblasts on epiphyseal plate • Osteoblast on diaphysis side of plate • Diameter • Osteoblasts surround pre-existing bone inside of periosteum

Bone Ossification • Ossification – is the formation of bone by osteoblasts. • Increase cells and extracellular matrix • Deposition of minerals

Figure 6.4b In which direction is this bone growing?

Bone = red • Cartilage = blue

Figure 6.2

Figure 6.7c

Bone Remodeling • Removal/deposition of bone • osteoclasts/osteoblasts • Purpose? • Change shape, adjustement to stress, etc. • Building too much? • Bone spurs, lumps • Not enough removal? • Compact bone too thick

On what part of the bone is this tumor located?

What are the osteoblasts doing? Acromegaly

Bone Repair Broken Bones • blood clot forms • Fibrous cartilage forms (callus) • Osteoblasts enter callus • Cancellous bone remodeled to form compact • Osteoblasts – form compact bone • Osteocytes – form cavity, shape sides

Figure 6.8

Figure 6.8a

Figure 6.8b

Figure 6.8c

Figure 6.8d

Titanium implants? How do your osteoblasts react? Research?

What Gives Bones Strength?? • Researchers have discovered that the structure of human bones is vastly different than previously believed -- findings which will have implications for how some debilitating bone disorders are treated. (Credit: iStockphoto)

Engineers Developing New Cements To Heal Spinal Fractures — New research could offer hope for victims of the most devastating spinal injuries - typically those caused in car crashes. Car Crash?? Spinal Injury??

The growth factor G-CSF, often used during cancer treatments, caused bone tumors to increase in size and intensity in laboratory mice. The mouse on the left did not receive G-CSF. The mouse on the right did, and it's bone tumor shows increased intensity in this special scan. (Image courtesy of Washington University School of Medicine) Bone Growth After Radiation

Healing broken bones with stem cells? • Broken bones: New methods to boost cell survival after transplant could help heal severe fractures.

'Bone Quality' Is An Empty Term, Say Researchers

Chapter 6: Skeletal System