The document outlines the skeletal system's structure, functions, and classifications, summarizing key learning objectives related to bones, including their definitions, composition, gross structure, and blood supply. It details the axial and appendicular skeletons, describing various categories of bones based on shape, development, and structural characteristics. Additionally, it covers the periosteum, endosteum, and the processes of bone development and ossification.

1. SKELETON SYSTEM
DR. DEEPANSHU SHUKLA
-Assistant Professor

2. LEARNING OBJECTIVES=
1. Introduction
2. Divisions of the skeletal system
3. Definition and composition of bones
4. Functions of bones
5. Classification of bones
6. Gross structure of an adult long bone
7. Parts of a young growing bone
8. Blood supply of bones
9. Nerve supply of bones
10.Development and ossification of bones

3. INTRODUCTION
• Skeleton is composed of bones and cartilages.
• Skeleton forms the main supportive
framework of the body.
• Designed for a more effective production of
movements by the attached muscles.
• It provides protection to viscera.

5. Divisions Of The Skeletal System

6. BONES OF AXIAL SKELETON
AXIAL SKELETON
Cranial Bones 8
Facial Bones 14
Hyoid Bone 1
Ear ossicles (3 in each
ear)
6
Vertebral Bones 26
Sternum 1
Ribs 24
Total 80

7. BONES OF APPENDICULAR SKELETON
APPENDICULAR SKELETON
Clavicle 2
Scapula 2
Humerus 2
Ulna 2
Radius 2
Carpals 16
Metacarpals 10
Phalanges 28
Hip Bone 2
Femur 2
Fibula 2
Tibia 2
Petella 2
Tarsals 14
Metatarsals 10
Phalanges 28
Total 12
6

8. Definition of Bone
• Synonyms- 1. Os (L), 2. Osteon (G).
• Bones are the hard structures, which forms the rigid
framework of the body.
• Bone is a highly vascular mineralized connective tissue.
• Composed of organic and inorganic materials.
• The inorganic salt calcium hydroxy apatite is removed
by putting the bone in acid, it becomes flexible and can
be tied as a “knot”.
• If organic tissue is removed by burning, the bone
crumples into small pieces.

9. FUNCTIONS OF BONES
• Provide shape and support of the body.
• Provide surface for the attachment of muscles, tendons,
ligaments.
• Serve as levers for muscles to bring about a movement.
• Protect certain viscera, e.g. brain, spinal cord, heart,
lungs, liver, bladder, etc.
• Contain marrow which is factory of blood cells, e.g.
W.B.Cs, R.B.Cs and platelets.
• Store 97% of the body calcium and phosphorus.

10. COMPOSITION OF BONES

11. Microscopic Structure Of Bones

12. Microscopic Structure Of Bones

13. Microscopic Structure Of Bones

14. Classification Of Bones

15. (A) According to Shape
1. Long Bones
2. Short Bones
3. Flat Bones
4. Irregular Bones
5. Pneumatic Bones
6. Sesamoid bones
7. Accessory ( supernumerary ) Bones

16. 1. LONG BONES

17. Typical Long Bone

18. Miniature Long Bone

19. Miniature Long Bone

20. 2. SHORT BONES

22. 3. FLAT BONES

24. 4. IRREGULAR BONES

25. 5.* PNEUMATIC BONES *

26. 5. PNEUMATIC BONES

27. 6.* SESAMOID BONES *

30. 6. SESAMOID BONES
FABELLA

31. 7. ACCESSORY BONES

32. WORMIAN BONE

33. OS TRIGONUM

34. OS VESALIANUM

35. PATELLA CUBITI

36. (B) Developmental Classification
1. Membranous Bones- membranous ossification.
eg.- bones of cranial vault, Facial bones.
2. Cartilagenous Bones- endochondral
ossification. eg.- ribs, sternum, vertebrae, bones
of limbs.
3. Membrano-cartilaginous Bones- by both
membranous and endochondral ossification. eg.-
mandible, clavicle, occipital bone, temporal
bone, sphenoid bone.

37. (C) Regional Classification
1. Axial Skeleton
2. Appendicular Skeleton

38. (D) Structural Classification
Macroscopically :
1. Compact Bone
2. Cancellous ( Spongy/Trabecular ) Bone
Microscopically :
3. Lamellar bone
4. Woven bone
5. Fibrous bone
6. Dentine
7. Cement

39. MACROSCOPICALLY

40. COMPACT BONE
The texture of compact bone is
dense, ivory- like with no visible
spaces on naked eye
examination. The compact bone
consists of:
a) Lamellae of collagenous
sheets,
b) Haversian system or osteons.

41. COMPACT BONE

42. COMPACT BONE

43. COMPACT BONE

44. HAVERSIAN SYSTEM ( OSTEON)

45. HAVERSIAN SYSTEM ( OSTEON)
•Each haversian system consists of
a haversian canal ( or central
canal), surrounded by concentric
lamellae of bone.
•Haversian canal are lined by
endosteum.
•Haversian canals communicate
with each other, with the
medullary cavity and with the
surface of bone by numerous
Volkmann’s canal.
•The volkmann’s canal run
perpendicular to the long axis of
the bone.
•The blood vessels from the
periosteum or endosteum enter the
bone through Volkmann’s canal.

46. HAVERSIAN SYSTEM ( OSTEON)

47. CANCELLOUS (SPONGY) BONE

48. CANCELLOUS (SPONGY) BONE

49. MICROSCOPICALLY

51. WOVEN BONE

52. DENTINE & CEMENT

53. GROSS STRUCTURE OF AN ADULT
LONG BONE
1. Shaft (diphysis)
2. Two ends (epiphysis):
• Upper end
• Lower end

54. Shaft:
•It is elongated part between the two expanded ends.
•It is made of an outer thick shell of compact bone enclosing a
cavity called medullary cavity.
Ends:
•The ends are knobby (expanded) and largely made up of
cancellous bone covered by a thin shell of a compact bone.
•The ends of long bone are covered by an articular hyline
cartilage and take part in the formation of joints.

56. PERIOSTEUM & ENDOSTEUM
•The outer surfaces of all the bones are
covered by a thick fibrous membrane
called periosteum,
•Whereas their inner surfaces are lined
by a thin fibrous membrane called
endosteum.
•Both periosteum and endosteum
contain osteoprogenitor cells,
osteoblasts and osteoclasts which are
essential for formation, remodeling and
repair of bone.
•The periosteum is a thick fibrous
membrane covering the entire surface
of bone except at the areas covered by
an articular cartilage.
•At the articular margin, the periosteum
is continous with the joint capsule.

57. FUNCTIONS OF PERIOSTEUM
• Protects and maintains the shape of the
bone.
• Provides attachment to ligaments, tendon,
muscles and intermuscular septa.
• Provides regenerative capability to the bone.

58. PARTS OF A YOUNG GROWING BONE
1. Epiphysis
2. Diaphysis
3. Metaphysis
4. Epiphysial plate of cartilage

59. EPIPHYSIS
Types of Epiphysis:
a. Pressure epiphysis
b. Traction epiphysis
c. Atavistic epiphysis
d. Aberrant epiphysis

62. EPIPHYSEAL PLATE

64. METAPHYSIS

65. BLOOD SUPPLY OF BONES
Arterial supply
Young Long Bones
a. Nutrient artery
b. Periosteal arteries
c. Epiphysial arteries
d. Metaphyseal arteries

66. BLOOD SUPPLY OF BONES

67. BLOOD SUPPLY OF BONES

69. DEVELOPMENT AND OSSIFICATION
OF BONES
• All the bones develop from a mesenchyme (mesodermal
embryonic tissue) by a process called ossification.
Types Of Ossification=

70. • Flat bones of skull, viz. frontal, parietal,
occipital, clavicle, etc. are ossified by
intramembranous ossification.
• All the long bones of limbs are ossified by
intracartilagenous ossification.

71. INTRAMEMBRANOUS OSSIFICATION

72. INTRAMEMBRANOUS OSSIFICATION

73. INTRACARTILAGINOUS
OSSIFICATION

74. INTRACARTILAGINOUS
OSSIFICATION

75. INTRACARTILAGINOUS
OSSIFICATION

76. OSSIFICATION (GROWTH) OF A
LONG BONE

78. Ossification Centers

80. Growing End Of The Long Bone

81. LAW OF OSSIFICATION

82. • Write short notes on
1. Ossification.
2. Pneumatic bone.
3. Cartilage.
4. Epiphysis.
5. Sesamoid bone.
6. Haversian system or osteon
QUESTIONS