View
227
Download
0
Category
Preview:
Citation preview
Chapter 6: The Skeletal System
http://www.accessexcellence.org/RC/VL/xrays/
FYE: Your Bones…
Bones aren’t just pieces of your skeleton They are a connective tissue impregnated with minerals! Bones aren’t dead!
They have cells, bloody supply & nerves (feelings!) Bones are strong!
Standing still the force on hip = 3x bodyweight (muscle pull) & a running man exerts a dead wt force of ~590 lbs!
The Skeletal System
Parts of the skeletal system
Some Vocab…• BONE = Osseous Tissue• Osteology = Study of bones• Arthrology = Study of joints• Kinesiology = Study of movement
Bones Cartilage
Ligaments (connect bone to bone) Tendons (connect muscle to bone)
Functions of the Skeletal System
Support For wt of entire body Framework for attachment
Leverage for muscle action Protection of internal organs
Storage Calcium & Phosphate Fat cells (in yellow marrow!)
Blood cell production = Hemopoiesis Red marrow makes cells Found in: pelvis, ribs, clavicle, vertebra, skull, ends of long bones
Bone Shapes
Figure 6-1
Femur, Phalanges & metacarpals Tarsals
Sternum, scapula, ribs
Clavicle, patella
The Structure of Bone
Figure 6-2
Features in a Long Bone Diaphysis (shaft)
Compact bone Marrow cavity
Epiphyses (ends) Spongy bone
Articular cartilage
Periosteum (covering)
Endosteum (lining)
The Structure of Bone
Bone (Osseous Tissue) Specialized cells
2% of bone wt Calcium Phosphate crystals
67% of bone wt
Collagen fibers
Two types: Compact & Spongy
Bone Tissue
Compact Bone Layers of compact cover all bone surfaces, except at joints
Found where stresses occur Osteon = basic functional unit of compact bone
Osteocytes surrounded by rings of matrix with a central canal
Bone Tissue
Spongy Bone Network of bony rods (trabeculae) Found in center & in epiphysis Lighter to decrease wt of skeleton Spaces filled with marrow
Microscopic Structure of Bone
Figure 6-3(a)
Microscopic Structure of Bone
Figure 6-3(b)
BONE CELLS
1. Osteocytes Mature bone cells in osteons & trabeculae
Most abundant cell Maintain normal structure by recycling Ca in matrix
2. Osteoblasts Cells that make new bone (osteogenesis)
3. Osteoclasts Bone eaters - secrete acid that dissolves matrix (osteolysis) to release stored minerals
Regulate Ca & Phosphate in blood
= Found in Endosteum & Periosteum
Bone Formation and Growth
• Begins ~6wks after fertilization - embryo is ~12mm long
• Continues until 18-25 yrs
• Ossification = process of replacing connective tissue & cartilage with bone
1. Intramembranous Ossification
• Stem cells in connective tissue (usually deep dermis) turn into osteoblasts & secrete matrix
• When matrix calcifies osteoblasts turn into osteocytes
• Ossification Center = where ossification 1st occurred, forms osteons of compact bone over time
• Flat bones of skull, lower jaw, clavicles form this way!
1. Endochondral Ossification
• Cartilage model replaced by bone
• Most bones form this way - especially long bones
Figure 6-52 of 6
Enlargingchondrocytes within
calcifying matrix
Chondrocytes at the center of the growing cartilage model enlarge and then die as the matrix calicifies.
Cartilagemodel
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 6-53 of 6
Enlargingchondrocytes within
calcifying matrix
Chondrocytes at the center of the growing cartilage model enlarge and then die as the matrix calicifies.
Newly derived osteoblasts cover the shaft of the cartilage in a thin layer of bone.
Cartilagemodel
Boneformation
Epiphysis
Diaphysis
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 6-54 of 6
Enlargingchondrocytes within
calcifying matrix
Chondrocytes at the center of the growing cartilage model enlarge and then die as the matrix calicifies.
Newly derived osteoblasts cover the shaft of the cartilage in a thin layer of bone.
Blood vessels penetrate the cartilage. New osteoblasts form a primary ossification center.
Cartilagemodel
Boneformation
Epiphysis
Diaphysis Marrowcavity
Primaryossificationcenter
Bloodvessel
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 6-55 of 6
Enlargingchondrocytes within
calcifying matrix
Chondrocytes at the center of the growing cartilage model enlarge and then die as the matrix calicifies.
Newly derived osteoblasts cover the shaft of the cartilage in a thin layer of bone.
Blood vessels penetrate the cartilage. New osteoblasts form a primary ossification center.
The bone of the shaft thickens, and the cartilage near each epiphysis is replaced by shafts of bone.
Cartilagemodel
Boneformation
Epiphysis
Diaphysis Marrowcavity
Primaryossificationcenter
Bloodvessel
Marrowcavity
Bloodvessel
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Enlargingchondrocytes within
calcifying matrix
Chondrocytes at the center of the growing cartilage model enlarge and then die as the matrix calicifies.
Newly derived osteoblasts cover the shaft of the cartilage in a thin layer of bone.
Blood vessels penetrate the cartilage. New osteoblasts form a primary ossification center.
The bone of the shaft thickens, and the cartilage near each epiphysis is replaced by shafts of bone.
Blood vessels invade the epiphyses and osteo-blasts form secondary centers of ossification.
Cartilagemodel
Boneformation
Epiphysis
Diaphysis Marrowcavity
Primaryossificationcenter
Bloodvessel
Marrowcavity
Bloodvessel
Secondaryossificationcenter
Epiphysealcartilage
Articularcartilage
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
http://commons.bcit.ca/biology/ossification/files/ossification2.html
Appositional Bone Growth
Figure 6-6
Requirements For Normal Bone Growth
Hormones Growth Hormone Sex hormones, thyroid hormone, others
MineralsCalcium, phosphate
VitaminsVitamin D3
Vitamin CVitamin A
Bone Remodeling/Homeostasis
• Remodeling - Continuous breakdown and reforming of bone tissue - 18% turned over/year
enables skeleton to adapt to new stresses
inactivity = degenerationFYE: Cast on leg for 6 wks - leg loses 1/3 bone mass!
FYE: your oldest bones are ~7 yrs!
needed for Ca regulation - bones store 2-4 lbs hormones control release into blood & storage
Disorders in Bone Growth & Remodeling
• Osteoporosis = bone mass reduced, can happen at any age
inactivity low Ca age (males - lose 3%/decade starting in 30’s, females lose 8%)
Disorders in Bone Growth & Remodeling
• Osteomalacia (Rickets) = Soft Bones from lack of Vit.D causes low Ca
Disorders in Bone Growth & Remodeling
• Osteogenesis Imperfecta = Genetic disorder affecting collagen fiber formation (1 in 20,000)
Disorders in Bone Growth & Remodeling
• Achondroplasia (Dwarfism) = Genetic disorder affecting cartilage formation mainly at epiphyses
Disorders in Bone Growth & Remodeling
• Acromegaly (Giantism) = Excess growth hormone - most often after epiphyseal plates closed
Disorders in Bone Growth & Remodeling
• Marfan’s Syndrome = Defective CT - excess cartilage at epiphyseal plates
An Overview of the Skeleton
Figure 6-8(a)
An Overview of the Skeleton
Figure 6-8(b)
An Overview of the Skeleton
Figure 6-9
The Axial Division: The Skull
Figure 6-10
The Axial Division: The Skull
Figure 6-11(a)
The Axial Division: The Skull
Figure 6-11(b)
Recommended