Bones provide structure and support to the body. They originally evolved from cartilage and first appeared as exoskeletons in invertebrates like snails. Over time, bones developed into endoskeletons in vertebrates. Bone tissue is a hard connective tissue composed of an organic bone matrix and mineral deposits. Bones can be classified as compact or cancellous, and bone formation occurs through two processes - intramembranous and endochondral ossification. Fractures disrupt the continuity of bones, and healing restores integrity through primary or secondary methods involving callus formation. Skeletonization is the final stage of decomposition where only bones remain.

1. BONES
-A.SABITH MEERAN

2. • A BONE IS A RIGID ORGAN THAT CONSTITUTES PART OF THE VERTEBRATE
SKELETON.
• IT PROVIDES SUPPORT AND MOBILITY AND GIVES SHAPE TO THE BODY.
• IT ALSO HARBORS BONE MARROW FROM WHICH RBCS AND WBCS ARE
PRODUCED.
• THE WORD ARISES FROM THE GERMAN WORD - BEIN
NEANDERTHAL - skull

3. EVOLUTION OF BONES
• BONE ORIGINALLY EVOLVED FROM CARTILAGE
• IN CASE OF INVERTEBRATES IT INITIALLY AS EXOSKELETONS AND FIRST ARISED
AS SHELLS ON MOLLUSCANS LIKE SNAILS AT 500 MILLION YEARS
AGO[CAMBRIAN PERIOD]
• THEN ARISED IN ARTHROPODAS AS EXOSKELETON LIKE IN COCKROACHES ,
CRUSTACEANS ETC
Cowrie shellsSnail shell

4. • THEN IN VERTEBRATES FIRST IT OCCURRED AS SHIELDS(ARMOURS) AROUND THE
FISH SURFACES.
• THEN ALL SHIELDED FISH WENT EXTINCT{ ARANDASPIS , PLACODERMS ,
OSTRACODERMS} DURING 470 MILLION YEARS AGO IN DEVONIAN MASS
EXTINCTION , THEN CARTILAGINOUS FISH LIKE SHARKS DOMINATED THE
OCEANS
• AFTER ALL THESE EFFORTS BONE THUS BECAME AS ENDOSKELETON
arandaspids
ostracoderms placoderms

5. BONE TISSUE - HISTOLOGY
• IT IS A HARD TYPE OF CONNECTIVE TISSUE WITH HONEYCOMB MATRIX .
• OSTEOBLASTS AND OSTEOCYTES – BONE FORMATION AND MINERALIZATION
• OSTEOCLASTS – BONE RESORPTION
• MINERALIZED MATRIX OF BONE TISSUE = OSSEIN + BONE MINERALS (VARIOUS SALTS)
• IT ALSO HAS CORTICAL BONES AND CANCELLOUS BONES AS WELL AS BONE MARROW
, NERVES , BLOOD VESSELS AND CARTILAGES .
• THE INORGANIC COMPONENT IS CALCIUM HYDROXYLAPATITE {CALCIUM
PHOSPHATE}

6. HISTOLOGY –COMPACT BONE

7. OSSIFICATION
• IT OCCURS DURING FETAL STAGE OF DEVELOPMENT
• INTRAMEMBRANOUS OSSIFICATION – FORMATION OF BONE FROM
MESENCHYMAL TISSUES , EG : FLAT BONES OF SKULL , MAXILLA , MANDIBLE ,
CLAVICLE.
• ENDOCHONDRAL OSSIFICATION – FORMATION OF BONE FROM CARTILAGE
EG: LONG BONES .
• LAW OF OSSIFICATION

8. BONE FRACTURE
• IT IS THE PARTIAL OR COMPLETE BREAK IN THE CONTINUITY OF BONE
• TRAUMATIC FRACTURES – RTA , ASSAULT ETC
• PATHOLOGICAL – OSTEOPENIA , OSTEOPOROSIS ,
OSTEOGENESIS IMPERFECTICA ,OSTEOSARCOMA ETC
• OPEN AND CLOSED TYPE OF FRACTURES AND
GREEN SICK FRACTURE
Ankle fracture

9. BONE HEALING
• PRIMARY HEALING {BY DIRECT UNION} – CONTACT AND GAP HEALING
• CONTACT HEALING –WHEN THE GAP BETWEEN BONE IS LESS THAN 0.01MM.
• GAP HEALING – WHEN THE GAP BETWEEN FRACTURED END IS 800UM TO 1MM.
• LAMELLAR BONE FORMATION OCCURS WITHOUT CALLUS FORMATION
Healed tibia

10. SECONDARY HEALING{INDIRECT HEALING}

11. TREATMENT OF NON UNION
Illizarov apparatus can be used to
stimulate delayed union

12. SKELETONIZATION
• SKELETONIZATION REFERS TO THE FINAL STAGE OF DECOMPOSITION, DURING
WHICH THE LAST VESTIGES OF THE SOFT TISSUES OF A CORPSE OR CARCASS
HAVE DECAYED OR DRIED TO THE POINT THAT THE SKELETON IS EXPOSED. BY
THE END OF THE SKELETONIZATION PROCESS, ALL SOFT TISSUE WILL HAVE BEEN
ELIMINATED, LEAVING ONLY DISARTICULATED BONES ( 3 WEEKS TO SEVERAL
YEARS).

13. • AFTER SKELETONIZATION, IF SCAVENGING ANIMALS DO NOT DESTROY OR
REMOVE THE BONES, ACIDS IN MANY FERTILE SOILS TAKE ABOUT 20 YEARS TO
COMPLETELY DISSOLVE THE SKELETON OF MID- TO LARGE-SIZE MAMMALS,
SUCH AS HUMANS, LEAVING NO TRACE OF THE ORGANISM.
• IN NEUTRAL-PH SOIL OR SAND, THE SKELETON CAN PERSIST FOR HUNDREDS OF
YEARS BEFORE IT FINALLY DISINTEGRATES. ALTERNATELY, ESPECIALLY IN VERY
FINE, DRY, SALTY, ANOXIC, OR MILDLY ALKALINE SOILS, BONES MAY
UNDERGO FOSSILIZATION, CONVERTING INTO MINERALS THAT MAY PERSIST
INDEFINITELY .
Old oracle bone excavated in china Fossils of trilobytes

14. IDENTIFICATION OF SEX FROM SKELETONS
• GENERAL SIZE , LONG BONES , SHAFT , ARTICULAR SURFACE , META CARPAL
BONES AND WEIGHT
• SKULLS – CAPACITY, ARCHITECTURE , ORBITS , SUPRAORBITAL RIDGES AND
MASTOID PROCESS
• MANDIBLE – CHIN , MENTAL TUBERCLES

15. PELVIS BONE
• PELVIC INLET , SUBPUBIC ANGLE , SACRUM AND PELVIC CAVITY

16. IDENTIFICATION OF AGE
• TEETH ERUPTION AND OSSIFICATION OF BONE
• DECIDUOUS TEETH – 20 [ 4I , 2 C , 4M] IN EACH JAW
• PERMANENT TEETH – 32 [ 4I , 2C , 4P , 6M]
• IN YEAR 6 OR 7 FIRST PERMANENT TEETH OCCURS.
• IF THIRD MOLARS ARE FULLY ERUPTED THEN THE INDIVIDUAL IS ABOVE 17 YEARS
• AGE ABOVE 21 YEARS CAN BE IDENTIFIED BY
• GUSTAFSON’S METHOD , BOYDE’S METHOD , STACK’S METHOD
orthopantogram

17. IDENTIFICATION OF RACE
• CEPHALIC INDEX = MAX. BREADTH OF SKULL/MAX. LENGTH *100
• DOLICO – CEPHALIC [LONG HEADED] {70-75}, MESATI CEPHALIC[ MEDIUM
HEADED]{75-80}
BRACY CEPHALIC[SHORT HEADED]{80-85}

18. ARTIFICIAL CRANIAL DEFORMATION