The Skeletal The Skeletal SystemSystem

Bone as a Living TissueBone as a Living Tissue

Functions of BonesFunctions of Bones

1. Support1. Support 2. Protection2. Protection 3. Movement3. Movement 4. Storage 4. Storage

(Minerals, medullary cavity stores (Minerals, medullary cavity stores marrow)marrow)

5. Blood cell formation5. Blood cell formation Hematopoiesis Hematopoiesis

Bone CompositionBone Composition

Cortical bone – dense outer layer; Cortical bone – dense outer layer; looks smooth & solidlooks smooth & solid

Trabecular (Spongy) bone – inner Trabecular (Spongy) bone – inner framework of small needle-like/flat framework of small needle-like/flat pieces of bone (trabeculae) that have pieces of bone (trabeculae) that have spaces in betweenspaces in between Spaces between filled with red or Spaces between filled with red or

yellow bone marrowyellow bone marrow

Spongy Spongy BoneBone

Shape Categories of BonesShape Categories of Bones

1. 1. Long bonesLong bones All limb bones (except kneecap, wrist, & All limb bones (except kneecap, wrist, &

ankle bones) are long bonesankle bones) are long bones

Long Bone StructureLong Bone Structure

1. Diaphysis – shaft of bone; cortical bone and 1. Diaphysis – shaft of bone; cortical bone and medullary cavity with yellow bone marrow medullary cavity with yellow bone marrow (fat)(fat)

2. Epiphyses – bone ends; covered in layer of 2. Epiphyses – bone ends; covered in layer of articular cartilage, red bone marrowarticular cartilage, red bone marrow

3. Membranes – 3. Membranes – a. periosteum – double-layered a. periosteum – double-layered

membrane that covers external surface membrane that covers external surface of bone of bone

b. endosteum – lines medullary cavityb. endosteum – lines medullary cavity

Shape Categories of BonesShape Categories of Bones

2. 2. Short bonesShort bones – cube shaped – cube shaped Wrist and ankle bonesWrist and ankle bones

3. 3. Flat bones Flat bones – thin, somewhat – thin, somewhat

curvedcurved Ribs, scapulaRibs, scapula

Shape Categories of BonesShape Categories of Bones

4. 4. Irregular bonesIrregular bones – have – have complicated shape that does not fit complicated shape that does not fit in other 3 categoriesin other 3 categories Vertebrae, hip bones are irregular Vertebrae, hip bones are irregular

Short BoneShort Bone

Composition of BoneComposition of Bone

Osteocyte= mature bone cellOsteocyte= mature bone cell

Osteon (aka Haversian system) – column Osteon (aka Haversian system) – column parallel to long axis of boneparallel to long axis of bone Haversian canal – run length of bone; osteocytes Haversian canal – run length of bone; osteocytes

here here

Lamella – hollow tubes of bone matrix; make Lamella – hollow tubes of bone matrix; make up osteons; like rings on tree trunkup osteons; like rings on tree trunk

Microscopic Anatomy of Microscopic Anatomy of Compact BoneCompact Bone

Lacunae – small cavities in bonesLacunae – small cavities in bones

Volkmann’s canal – perforating canal; Volkmann’s canal – perforating canal; runs sideways, connects blood/nerve runs sideways, connects blood/nerve to central canalsto central canals

Canaliculi – small sideways canals Canaliculi – small sideways canals connecting lacunae and central canal; tie connecting lacunae and central canal; tie all osteocytes in an osteonall osteocytes in an osteon

OsteonOsteon

Bone Growth & Bone Growth & DevelopmentDevelopment

Bone deposition, build bone – osteoblasts

Remove/remodel – osteoclast

Epiphyseal plate = growth plate

Ossification – Bone Ossification – Bone DevelopmentDevelopment

Aka osteogenesisAka osteogenesis

1. Formation of bony skeleton1. Formation of bony skeleton 2. Bone growth2. Bone growth

length length width (with stress)width (with stress)

Hypertrophy vs. atrophyHypertrophy vs. atrophy 3. Remodeling3. Remodeling

OssificationOssification

Factors Affecting Bone Factors Affecting Bone Development, Growth & Development, Growth &

RepairRepair Deficiency of Vitamins:

Vitamin A - slows bone development, Vita C – fragile bones, Vita D – rickets

Insufficient or Excessive GH: dwarfism or Gigantism

Sex Hormones – promote bone formation; stimulate ossification of epiphyseal plates

Physical Stress – stimulates bone growth

Axial SkeletonAxial Skeleton