Skeletal System

Chapter  7  

Objectives

1.  Iden/fy  the  different  structures  and  fuc/ons  of  the  Skeletal  system.  

2.  Label  a  long  bone  and  internal  structures  of  bone.  

3.  Explain  bone  development  and  growth.  4.  Apply  knowledge  of  homeosta/c  

mechanisms  to  explain  the  regula/on  of  blood  calcium  levels.    

Introduction

•  Bones  are  very  ac/ve  /ssues  •  Each  bone  is  made  up  of  several  types  of  /ssues  and  is  an  organ  

Skeletal System Components •  Bone  •  Tendons-­‐  connect  bones  to  muscle  

•  Ligaments-­‐  connect  bones  to  bones  

Functions

•  Muscle  aJachment  •  Protec/on  •  Contain  blood-­‐producing  cells  

•  Storage  of  inorganic  salts  •  Passageway  for  nerves  &  blood  vessels  

Types of Bone Tissue

•  Compact  bone:  homogeneous  •  Spongy  bone:  small  needle-­‐like  pieces  of  bone;  many  open  spaces    

Classification of Bones

Long Bones •  Characteris/cs:  Typically  longer  than  they  are  wide,  have  a  shaQ  with  heads  at  both  ends  

•  Structure:  contain  mostly  compact  bone  

•  Examples:    –  Humerus,  Femur,  Ulna,  Radius,  Clavicle,  Phalanges  

Short Bones •  Characteris/cs:  Generally  cube-­‐shaped  

•  Structure:  contain  mostly  spongy  bone  

•  Examples:    – Wrist  bones  –  Foot  bones  

Flat Bones •  Characteris/cs:  thin,  flaJened,  and  usually  curved  

•  Structure:  two  thin  layers  of  compact  bone  surrounding  a  layer  of  spongy  bone  

•  Example:  –  Scapula    –  Sternum  

Irregular Bones •  Characteris/cs:  irregular  shape,  do  not  fit  into  other  bone  classifica/on  categories  

•  Example:  –  Pelvis  –  vertebra  

Bone Classification

•  Sesmoid  

Long Bone Anatomy

Bone Structure •  Bones  differ  in  size  and  shape,  yet  are  similar  in  several  ways  

•  Parts  of  a  long  bone  – Epiphysis  –  expanded  ends  of  bones  that  form  joints  with  adjacent  bones  

– Ar/cular  car/lage  (hyaline  car/lage)  –  covers  the  epiphysis  

– Diaphysis  –  the  shaQ  of  the  bone  – Periosteum  –  a  tough  layer  of  vascular  connec/ve  /ssue  that  covers  the  bone  and  is  con/nuous  with  ligaments  and  tendons    

Parts of a long bone •  A  bone’s  shape  makes  possible  its  func/on  •  Bony  processes  or  grooves  indicate  places  of  aJachment  for  muscles  

•  Compact  bone  makes  up  the  wall  of  the  diaphysis  

•  The  epiphyses  are  filled  with  spongy  bone  to  reduce  the  weight  of  the  skeleton  

•  The  diaphysis  contains  a  hollow  medullary  cavity  that  is  filled  with  marrow  

Microscopic Structure •  Compact  (Cor4cal)  Bone:  osteocytes  and  layers  of  ECM  are  concentrically  clustered  around  a  Haversian  Canal  (Osteon).    – Haversian  Canals  contain  blood  vessels  and  nerve  fibers  which  nourish  the  bone  cells.  

Microscopic structure

•  Osteocytes  –  bone  cells  that  are  located  within  lacunae  that  lie  in  concentric  circles  around  osteonic  canals  

•  Intercellular  material  consists  of  collagen  and  inorganic  salts  

•  In  compact  bone,  osteocytes  and  intercellular  material  are  organized  into  osteons  that  are  cemented  together.    

Microscopic structure  

•  Osteonic  canals  contain  blood  vessels  and  nerve  fibers  and  extend  longitudinally  through  bone.  

•  Osteonic  canals  are  interconnected  by  transverse  perfora/on  canals.  

•  Unlike  compact  bone,  the  osteocytes  and  intercellular  material  in  spongy  bone  are  not  arranged  around  osteonic  canals.    

Microscopic structure  

Microscopic Structure

Bone Growth and Development

•  Osteoclasts  –  break  down  car/lage  and  bone  •  Osteoblasts  –  bone-­‐building  cells  •  Osteocytes  –  bone  cells  

Bone Development •  Intramembranous  Bones:  – Originate  between  sheetlike  layers  of  connec/ve  /ssue.  

•  Endochondral  Bones:  – Begin  as  masses  of  car/lage  that  bone  /ssue  replaces.  

Bone Development •  Intramembranous  Ossifica4on:  

1.  Connec/ve  /ssue  appears  at  the  sites  of  future  bones.    2.  Connec/ve  /ssue  cells  differen/ate  into  osteoblasts.  3.  Osteoblasts  deposit  bony  material  around  themselves  and  form  spongy  bone.  4.  Membranous  /ssue  cells  give  rise  to  the  periosteum.  5.  Osteoblasts  inside  the  periosteum  form  compact  bone.  

Intramembranous Bones

Bone Development •  Endochondral  Ossifica4on  (Condensed  Version):    

1.  Car/lage  breaks  down  in  the  center  of  the  diaphysis.  (primary  ossifica/on  center)  

2.  Periosteum  forms  around  the  developing  dipahysis  from  connec/ve  /ssue.  

3.  Blood  vessels  and  osteoblasts  from  periosteum  invade  the  car/lage  and  form  spongy  bone.  

4.  Epiphysis  remain  car/laginous  and  later  secondary  ossifica/on  centers  appear  and  form  spongy  bone.  

5.  Epiphyseal  plate  undergoes  mitosis  and  produces  new  cells  which  enlarge  ,  while  calcium  salts  accumulate  in  the  extracellular  matrix,  they  calcify,  and  the  car/lage  cells  die.  

6.  Osteoclasts  secrete  acid  that  dissolves  part  of  the  calcified  matrix  and  osteoblasts  deposit  new  bone  /ssue  in  place  of  the  calcified  car/lage.  

7.  Bone  con/nues  to  grow  at  the  epiphyseal  plate  un/l  adulthood.  

Endochondral Ossification

Objectives

•  To  explain  the  different  func/ons  of  bone  in  detail.  

•  To  apply  your  knowledge  of  homeostasis  and  nega/ve  feedback  loops  to  explain  hormonal  regula/on  of  bone  calcium  resorp/on  and  deposi/on.  

Bone Functions

•  Support  and  Protec/on  – Bones  give  shape  to  the  head,  thorax,  and  limbs  – The  pelvis  and  lower  limbs  provide  support  for  the  body  

– Bones  of  the  skull  protect  the  brain,  ears  and  eyes  •  Movement  – Muscles  aJach  to  bones  – Push  and  pull  bones  for  movement  

Bone Functions •  Blood  cell  Forma/on  – Two  kinds  of  marrow  occupy  the  medullary  cavi/es  of  bone  •  Red  marrow  –  forma/on  of  red  blood  cells,  white  blood  cells  and  platelets  

•  Yellow  marrow  –  stores  fat  

•  Storage  of  Inorganic  Salts  – Bone  stores  inorganic  mineral  salts  in  the  form  of  calcium  phosphate  

– Calcium  in  bone  is  a  reservoir  for  body  calcium  • When  blood  levels  of  calcium  are  low,  osteoclasts  release  calcium  from  bone.  

•  Calcium  is  stored  in  bone  under  the  influence  of  calcitonin  when  blood  levels  of  calcium  are  high.  

Hematopoiesis •  Hematopoeiesis=Red  blood  cell  forma/on  •  RBC’s  form  in  the  liver,  spleen,  and  bone  marrow  –  Red  Marrow:    

•  Found  in  infants  as  well  as  in  spongy  bone  of  skull,  ribs,  sternum,  clavicles,  vertebrae,  and  hip  bones  of  adults  

•  Produces  red  blood  cells  (erythrocytes),  white  blood  cells  (leukocytes),  and  platelets.  

–  Yellow  Marrow:  •  In  adults  •  Stores  fat  •  *doesn’t  produce  RBC’s  

Inorganic Salt Storage

•  ECM  of  bone  is  rich  in  calcium  •  Calcium  is  required  for  muscle  contrac/on,  nerve  impulse  conduc/on,  blood  clohng,  and  other  physiological  processes.  

•  Our  bodies  must  maintain  a  sufficient  blood-­‐calcium  level  using  a  homeosta/c  mechanism.  

Calcium Regulation

Low calcium levels

•  Causes  Parathyroid  Hormone  (PTH)  to  be  released  – PTH  causes  stored  calcium  in  bone  to  be  released  – PTH  causes  calcium  reabsorp/on  in  the  kidney  (not  excreted  in  urine)  

– PTH  causes  the  synthesis  of  Vit.  D.  which  increases  Ca+  absorp/on  in  the  small  intes/nes.  

High calcium levels

•  Causes  the  release  of  calcitonin  from  the  thyroid  gland  – Calcitonin  Inhibits  Ca2+  absorp/on  by  the  intes/nes  

–  Inhibits  osteoclast  ac/vity  in  bones  –  Inhibits  renal  tubular  cell  reabsorp/on  of  Ca2+  allowing  it  to  be  excreted  in  the  urine  

Hypo vs. Hypercalcemia

•  Hypocalcemia:  can  cause  muscle  s/ffness  and  seizures  

•  Hypercalcemia:  too  much  calcium,  causes  kidney  stones  or  even  kidney  failure,  could  cause  heart  problems  

Bone Fractures

•  Defini/on:  break  in  a  bone  •  Types  of  bone  fractures  – Closed  (simple)  fracture  –  break  that  does  not  penetrate  the  skin  

– Open  (compound)  fracture  –  broken  bone  penetrates  through  the  skin  

•  Treatment:  reduc/on  and  immobiliza/on    

Common types of Fractures

Repair of Bone fractures

•  Steps  in  repair  of  bone  fractures    1.  Hematoma:  blood-­‐filled  swelling  is  formed  2.  Fibrocar/lage  callus:  break  is  connected  by  

fibrocar/lage  3.  Bony  Callus:  fibrocar/lage  replaced  by  

spongy  bone  4.  Bone  remodeling:  permanent  healing  

Repair of Bone fractures  

Hematoma External callus

Bony callus of spongy bone

Healed fracture

New blood vessels

Internal callus (fibrous tissue and cartilage)

Spongy bone trabecula

Hematoma formation

Fibrocartilage callus formation

Bony callus formation

Bone remodeling

Curve of the Spine

•  The  spine  has  a  normal  curvature  •  Primary  curvatures:  curvatures  of  the  thoracic  and  sacral  regions  – Present  from  birth  

•  Secondary  curvatures:  spinal  curvatures  of  the  cervical  and  lumbar  regions  – Develop  aQer  birth    

 

Skeletal changes throughout life  

•  Osteoporosis  – Bone-­‐thinning  disease  afflic/ng    

•  50%  of  women  over  age  65  •  20%  of  men  over  age  70  

– Disease  makes  bones  fragile  and  bones  can  easily  fracture  

– Vertebral  collapse  results  in  kyphosis  (also  known  as  dowager’s  hump)  

– Estrogen  aids  in  health  and  normal  density  of  a  female  skelton    

Skeletal changes throughout life  

Skeletal changes throughout life  

Objectives

•  To  Iden/fy  the  major  bones  of  the  skull.    •  To  label  the  major  features  of  the  bones  of  the  skull.  

Skeletal Organization

•  Axial  Skeleton  – Consists  of  the  skull,  hyoid  bone,  vertebral  column  and  thorax  (ribs  and  sternum)  

•  Appendicular  Skeleton  – Consists  of  the  pectoral  girdle  (scapula  and  clavicle),  upper  limbs,  pelvic  girdle  (coxal  bones)  and  lower  limbs  

Skeletal Organization  

The Skull!!

•  Structure:  made  up  of  two  sets  of  bones  – Cranium  – Facial  bones    

•  Bones  are  joined  by  sutures  

Human Skull, Lateral View

Human Skull, Superior View

Human Skull, Inferior View

Human Skull, Anterior View

Paranasal Sinuses

•  Structure:  hollow  por/ons  of  bones  surrounding  the  nasal  cavity  

•  Func/ons:  – Lighten  the  skull  – Amplify  voice  

Paranasal Sinuses  

The Vertebral Column

•  Structure:  24  single  vertebral  bones  separated  by  intervertebral  discs  – Cervical  vertebrae:  7  in  neck  – Thoracic  vertebrae:  12  in  chest  region  – Lumbar  vertebrae:  5  in  lower  back  – Sacrum  and  coccyx:  9  fused  vertebrae  in  gluteal  region    

The Vertebral Column

Superior view of vertebrae

Atlas and Axis

•  Structure:  most  superior  vertebrae  – Atlas:  C1  – Axis:  C2  

•  Func/on:  form  joint  connec/ng  skull  and  spine;  allow  for  movement  of  head    

Regional characteristics of vertebrae

Regional characteristics of vertebrae  

Regional characteristics of vertebrae  

Regional characteristics of vertebrae  

Sacrum and coccyx

The Bony Thorax

•  Structure:  made  of  three  parts  1.  Sternum  2.  Ribs  •  True  ribs  (pairs  1-­‐7)  •  False  ribs  (pairs  8-­‐12)  •  Floa/ng  ribs  (pairs  11-­‐12)  

3.  Thoracic  vertebrae    •  Func/on:  forms  a  cage  to  protect  major  organs  

The Bony Thorax  

Male and Female Pelvis •  Differences  in  male  and  female  pelvis  aid  in  childbirth  –  Female  inlet  is  larger  and  more  cicular  –  Female  pelvis  as  a  whole  is  shallower  and  the  bones  are  lighter  and  thinner  

–  Female  ilia  flare  more  laterally  –  Female  sacrum  is  shorter  and  less  curved  –  Female  ischial  spines  are  shorter  and  further  apart  –  Female  pubic  arch  is  more  founded  because  the  angle  of  the  pubic  arch  is  greater    

Joints

•  The  func/onal  junc/ons  (ar/cula/ons)  between  bones  

•  Enable  a  wide  variety  of  body  movements  •  Can  be  classified  according  to  the  degree  of  movement  possible:  –  Immovable  – Slightly  movable  – Freely  movable  

Joints  

•  Can  also  be  classified  according  to  the  type  of  /ssue  that  binds  them  together:  – Fibrous  – Car/laginous  – Synovial  

Fibrous Joints •  Held  together  by  dense  connec/ve  /ssue  

•  Immovable  or  only  slightly  moveable  –  Examples:  •  Sutures  of  the  skull  (immovable)  

•  Joint  between  the  distal  /bia  and  fibula  (slightly  movable)  

Cartilaginous Joints •  Hyaline  car/lage  or  discs  of  fibrocar/lage  unite  the  bones  in  car/laginous  joints  –  Example:  intervertebral  disks  

Synovial Joints •  Makes  up  most  joints  of  the  skeletal  •  More  complex  than  fibrous  or  car/laginous  joints  

•  Ar/cular  ends  of  bone  in  a  synovial  joint  are  covered  with  hyaline  car/lage  

•  Ar/cula/ng  surfaces  within  the  joint  are  lubricated  with  synovial  fluid  

•  Are  classified  (and  named)  based  on  the  shapes  of  their  parts  and  the  movements  they  permit  

Ball and Socket Joint •  Consists  of  a  bone  with  a  globular  or  egg-­‐shaped  head  ar/cula/ng  with  the  cup  shaped  cavity  of  another  bone  

•  Permits  a  very  wide  range  of  mo/on  

•  Examples:  –  Hip  and  Shoulder  Joints    

Condyloid Joint •  Consists  of  an  ovoid  condyle  fihng  into  an  ellip/cal  cavity  

•  Permits  a  wide  variety  of  mo/ons  

•  Example:  –  Joint  between  a  metacarpal  and  a  phalange    

Gliding Joints •  Occur  where  ar/cula/ng  surfaces  are  nearly  flat  or  slightly  curved  

•  Permits  a  “back  and  forth”  mo/on    

•  Example:  –  Joints  of  the  wrist  and  ankle  

Hinge Joint •  Occurs  where  a  convex  surface  fits  into  a  concave  surface  

•  Movement  is  in  one  plane  only  

•  Example:  –  Elbow  and  phalange  joints  

Pivot Joint •  Occurs  where  a  cylindrical  surface  rotates  within  a  ring  of  bone  and  fibrous  /ssue  

•  Example:  –  Joint  between  the  proximal  ends  of  the  radius  and  ulna    

Saddle Joint •  Forms  where  ar/cula/ng  surfaces  have  both  concave  and  convex  areas  

•  Permits  a  wide  range  of  movements  

•  Example:  –  The  metacarpal  of  the  thumb    

Inflammatory Disorders of the Joints

•  Bursi/s:  inflamma/on  of  bursa  (synovial  membrane);  water  on  the  knee    

Inflammatory Disorders of the Joints

•  Sprain  – Ligaments  or  tendons  reinforcing  joint  are  damaged  by  excessive  stretching  or  are  torn  away  from  bone  

– Slow  to  heal  because  of  poor  blood  supply  •  Disloca/on  – When  a  bone  is  forced  out  of  normal  posi/on  in  the  joint  cavity  

Inflammatory Disorders of the Joints

•  Arthri/s  – Most  widespread,  crippling  disease  in  the  U.S.  – 1  in  7  Americans  suffer  with  it  –  Ini/al  symptoms:  Pain,  s/ffness,  and  swelling  of  the  joint  

– Acute  and  Chronic  forms  of  Arthri/s    

Inflammatory Disorders of the Joints  

•  Acute  Arthri/s  – Result  from  bacterial  invasion  – Treated  with  an/bio/c  – Synovial  membrane  thickens  and  fluid  produc/on  decreases,  leading  to  increased  fric/on  and  pain  

Inflammatory Disorders of the Joints  

•  Chronic  Arthri/s    –  Osteoarthri/s    

•  Most  common  form  •  Degenera/ve  condi/on,  usually  affects  the  aged  •  Wear  and  tear  affects  •  Can  cause  bone  spurs  which  restrict  joint  movement    

–  Rheumatoid  arthri/s  •  Occurs  between  40-­‐50  years  of,  but  can  occur  at  any  age  •  Affects  more  women  than  men  •  Many  joints  affected  at  the  same  /me  and  usually  in  symmetrical  manner  (leQ  elbow  then  right  elbow)  

•  Marked  by  remission  (goes  away)  and  flare  ups  (comes  back)  •  Autoimmune  disease  –  body  aJacks  its  own  /ssues    

–  Gouty  arthri/s