The document is a comprehensive presentation on bones, covering their histological features, composition, and classification based on regions, structure, and development. Key topics include the living nature of bones, the role of bone cells, and the various types such as long, short, flat, and irregular bones. It also details the processes of ossification and the anatomical distinction between the axial and appendicular skeletons.

1. Made by:
Suman Shaikh
(Student of 3rd Year at College
of Physiotherapy, JPMC)
PRESENTATION ON BONES

2. Learning Objectives :
• To Explain, what actually bones are by giving a detail account on :
• The Histological Features of Bone
• Composition of Bone
• Classification of bones :
1. On the basis of regions and different shapes of bones
2. Structural classification of bones
3. Developmental classification
• Blood And Nerve supply of bone
• Functions of Bones.

3. Introduction of Bones
Q: What are bones??
 Bones are rigid bars, that are made up
of connective tissues.
These are living tissues that are capable
of growth and perform vast number of
functions.
These are the reservoirs of about 99% of
calcium of our body.

4. Bones, despite of their hardness, are very much a living
tissue.
They have greater regenerative power than any other tissue
of the body(except blood).
It can be subjected to disease, and can be fractured.
It can mould itself according to changes is stress and strain.
Introduction of Bones (continued)

5. Introduction of Bones (continued)
 The adult skeleton consists of 206 bones.
 When we are born, we have greater number of
bones, about 275.
 But as time passes, many bones fuse together, and
decrease in count.

6. • Also at birth, there is greater amount of cartilage,
which is afterwards replaced by bones.
Over a period of about 7 years, each bone in our body
is slowly replaced by a new bone.
This happens by a process called :
Cartilaginous ossification
(which will be described later)
Introduction (continued)

7. Histological Features of Bone
• Our skeleton consists of greater part of compact
bone(described later).
• This bone consists of large number of tree like
structures called Haversian systems or Osteon.
• Osteon is the functional unit of bones.

8. Lamellae :
• these are plate like structures
around the haversian canal.
Edged by Lacunae (small
spaces), where osteocytes
reside.
• Osteoblasts are bone cells
contained in lamellae of
bones( described later)
Haversian canal :
Here Nerve and blood supply is
present. Here O2 is supplied,
and CO2 is taken away.
Histological Features of Bone (cont…)

9. Composition of bones
• Bones are composed of :
1. Bone cells
2. Extracellular matrix
Osteoblast
Osteocytes
Osteoclasts
Osteoprogenitor cells
Collagen fibers
inorganic minerals.
Bone Cells
Extracellular
matrix

10. • Bones are living tissues, so
they contain metabolically
active cells.
Bone Cells
Composition of bones (continued)
Osteoblast
Osteocytes
Derived from
Osteoprogenitor
cells
Osteoclasts
Derived from the same cells
from which macrophages and
monocytes are formed

11. Bone Cells
Composition of bones (continued)

12. • Osteoblasts are bone forming cells. They
secrete bone matrix.
• They are responsible for mineralization the
bone tissue.
• When osteoblasts are trapped in the matrix
which they have secreted, then they become
osteocytes
Composition of bones (continued)
Osteocyte

13. Osteoclasts :
• Osteoclasts are bone
reabsorbing cells.
• Responsible for
demineralization of bone.
•
• Important role in re-
modeling of bone.
• Also recycle the matrix.
Composition of bones (continued)

14. • Extracellular matrix
It contains collagen fibers(organic substance) and
inorganic minerals embedded in it.
Q) What are collagen fibers?
Collagen fibers are the most abundant protein
in human body.
It is a kind of fibrous connective tissue.
 They function as a glue in the body, i.e. it holds
together all the body structures.
Composition of bones (continued)

15. Composition of bones (continued)
Histological Section of Fibrous connective tissue :

16. • About 60 % of the bones are
composed of inorganic minerals.
These include:
1. Calcium
2. Phosphorus
3. Magnesium
4. Potassium
5. Sodium
6. Citrate
 Major minerals are calcium and
phosphorus.
 Calcium is in the form of calcium
salt, mainly calcium phosphate
(CaP04) and partly calcium
carbonate (CaC03).
Inorganic minerals
Inorganic minerals
Organic substance
water
Composition of bones (continued)

17. % of Inorganic minerals
Composition of bones (continued)

18.  Inorganic mineral crystals form rod shaped crystals.
 These mineral crystals are responsible for hardness,
rigidity and great compressive strength of bone.
 In Strength, bone is comparable to iron and steel.
Significance of Inorganic Minerals
Composition of bones (continued)

19. • About 25 % of bone is composed of organic substances,
which includes:
1. Collagen fibers Mainly type I collagen
1. Ground substances
Organic substances
Glycoproteins
Mucopolysaccharides
Composition of bones (continued)

20. • Significance of organic substances
Composition of bones (continued)
 Provide strength and stability to our body.
 Make the bones tough
Provide flexibility, which can afford resistance
to tensile forces.

21. Final Summary of Composition of Bones

22. REGIONAL CLASSIFICATION OF BONES
 On regional basis,
human skeleton can be
divided in two major parts:
1)AXIAL SKELETON
2) APPENDICULAR
SKELETON

23. AXIAL SKELETON
Skull
Thoraic cage
Vertebral
column
• Axial skeleton consists
of skull, thoraic cage
and vertebral column
• It is of protective
nature. It protects our
vital organs such as
brain, spinal cord,
heart, lungs etc.

24. AXIAL (Part one)
Cranium: 8 Bones
Facial: 14 Bones
Auditory Ossicles:
6 Bones
Skull :
Cranium
Facial
bones
Mandible

25. Cranium
Cranium is also called
braincase or brain box,
because it encloses the
brain.
It has paired bones
which are parietal and
temporal bones.
And others are unpaired,
these are frontal, occipital,
sphenoid and ethmoid
Frontal
Bone
Parietal
bone
Occipital
boneTemporal
bone
Sphenoid
bone
Ethmoid

26. Facial Bones
• Nasal
• Zygomatic
• Maxilla
• Mandible
• Lacrimal
• Palatine
• Inferior
nasal
choncha
Bones of the
Face are:
These are 22 bones. In which the paired are: Nasal, Zygomatic,
Maxilla, Lacrimal, Palatine, and inferior nasal choncha
And the unpaired ones are: mandible and vomer bones.

27. Ribs
• There are 12 pairs of ribs.
• They form the thoraic cage
of our skeleton.
Ribs

28. Vertebral Column
• There are 26 vertebrae in
the human skeleton
• They are divided into 4
regions:
1. Cervical ( 8 )
2. Thoraic ( 12 )
3. Lumbar and ( 5 )
4. Sacral ( 5 )

29. Hyoid bone
• It is a single bone
present in the neck.
Sternum
Manuberum
Sternal body
Xiphoid
process
•Also called Chest
bone or breast bone.
•Present in the
midline of chest.

30. APPENDICULAR SKELETON
It consists of :
Shoulder girdle : Clavicles ( 2 )
Scapula ( 2 )
 Upper Extremities
Humerus ( 2 )
Radius ( 2 )
Ulna ( 2 )
Carpals (16 )
Meta Carpals ( 10 )
Phalanges ( 28 )
Pelvic girdle Hip bones ( 2 )
Lower Extremities
Femur : ( 2 )
Patella : ( 2 )
Fibula : ( 2 )
Tibia : ( 2 )
Tarsals : ( 14 )
Meta Tarsals : ( 10 )
Phalanges : ( 28 )

31. Shoulder Girdle
The pectoral
girdle or shoulder
girdle is formed by
the articulation of
scapula and
clavicle, along
with the head of
humerus on the
glenoid cavity of
scapula.

32. Upper limb
The humerus bone articulates
with the glenoid cavity of scapula
at its upper end.
Humerus forms the upper arm,
also called brachium.
At its lower end it articulate with
radius at elbow joint.
Radius and ulna bones form the
forearm, also called antibrachium.
Carpel bones form the wrist
Metacarpels form the palm
Phalanges form the digits.

33. Pelvic Girdle
The pelvic girdle
consists of the two hip
bones.
Each of the Hip bone is
also called In nominate
bone because it is fusion
of three bones namely,
Ilium, Ischium and pubis.

34. Lower Limb
The femur bone is the
largest and strongest of all
bone in the body.
It articulates with pelvic
girdle at its upper end, and
with tibia fibula at its lower
end.
The lower arm is formed by
tibia and fibula.
Tarsals and metatarsals
form the foot.
And phalanges form the
digits.
Tibia and
fibula
Foot

35. Summary of the topic

36. Classification Of Bones
On the basis of shape :
1.Long Bones
2.Short Bones
3.Flat Bones
4.Irregular Bones
5.Pneumatic Bones
6.Sesamoid Bones
7.Accessory (supernumerary ) Bones
8.Heterotopic Bones

37. Long Bones
 >"Long bones" are longer than they are wide,
i.e. length > diameter.
 They consist of a shaft - which is the main (long) part and
variable number of endings (extremities).
Long bones are usually somewhat curved - contributing to
their mechanical strength.

38. Types of Long Bones
• Typical Long Bones
They have an elongated shaft and two ends and are
represented by bones such as humerus, femur, radius, ulna,
tibia and fibula.
• Miniature Long Bones
They have only one epiphysis like metacarpals, metatarsals
and phalanges.
• Modified Long Bones
They have no medullary cavity like clavicle.

39. SHORT BONES
> "Short bones" can be approximately cube-shaped,
i.e. length is similar to width/depth/diameter.
The most obvious examples are the carpal bones (of the
hands/wrists) and the tarsal bones (of the feet/ankles)

40. FLAT BONES
• "Flat bones" have a thin shape and, in some cases,
provide mechanical protection to soft tissues
beneath or enclosed by the flat bone.
e.g. cranial bones that protect the brain.
Flat bones also have extensive surfaces for muscle
attachments e.g. scapula (shoulder) bones.

41. IRREGULAR BONES
• "Irregular bones" have complicated shapes that
cannot be classified as "long", "short" or "flat". Their
shapes are due to the functions they fulfill within the
body e.g. providing major mechanical support for the body
yet also protecting the spinal cord (in the case of the
vertebrae).

42. PNEUMATIC BONES
• A bone that is hollow or contains many air cells, such
as the mastoid process of the temporal bone.
Also called hollow bone.
• E.g; Maxilla, Sphenoid

43. Sesamoid Bones
• In anatomy , a sesamoid bone is a bone embedded
within a tendon or a muscle It is derived from the
Latin word "sesamum" (sesame seed), due to the
small size of most sesamoids.

44. Accessory (Supernumerary) Bones
• An accessory bone is
a bone which does not occur
frequently in the body but is still
present in a significantly large
number of people.
• E.g ; Examples of accessory bones
include the os trigonum ("accessory
talus") which if present in
the foot typically lies posterior to
the talus and the accessory navicular
bone.

45. Heterotopic Bones
• Bones sometimes develop in soft tissues. Horse
riders develop bones in adductor muscles (rider’s
bones).

46. Structural Classification of Bones
• On the basis of structure, there
are two levels by which we can
classify bones.
1. Macroscopic level
2. Microscopic level
Macroscopic level
Without using a microscope,
macroscopically
we can see :
1. Compact bone
2. Cancellous bone

47. • Also called cortical bone.
• It forms the outer shell (or
cortex) of the bones.
• It makes up 80 % of the
adult human skeleton.
• It is dense in texture, but is
also extremely porous.
Compact Bone
Compact
bone
Structural Classification of Bones (cont..)

48. • Structural unit of compact bone is the
osteon ( Haversian System )
•Compact bone has canals and passageways that serve
as routes for nerves, blood vessels and lymph vessels.
Structural Classification of Bones (cont..)

49. • Also called Spongy bone.
• Present inside the bone.
• It contains red bone marrow.
• It is open in texture and has
greater surface area.
• Cancellous bone is an
adaptation to compressive
forces.
Cancellous Bone
Cancellous
bone
Structural Classification of Bones (cont..)

50. Consists of trabeculae(rods and plates) which are positioned
where the bone is stressed.
Only a few layers thick, the trabeculae contain irregularly
arranged lamellae and osteocytes interconnected by canaliculi.
Structure :
Cancellous bone is made
up of a meshwork of
trabeculae between which
spaces of marrow are
present.
These meshwork are of
three main types :
1. Meshwork of rods
2. Meshwork of rods and
plates
3. Meshwork of plates
Structural Classification of Bones (cont..)

51. • There are two tissue layers,
lining our bones:
1. Periosteum
2. Endosteum
• Periosteum lines outside
surface of bones, to which
muscles attach with.
• Endosteum lines the
medullary cavity, which
contains bone marrow.
Tissue layers
Periosteum
Endosteum
Structural Classification of Bones (cont..)

52. • Microscopic level
Microscopically, bones are of five types.
• LAMELLAR BONE :
mature bones whether compact or cancellous
composed of thin boney plates called cancellous bones
but in concentric cylinders in a compact bone
• WOVEN BONE :
It is seen in fetal bone , fracture repair and in
cancer of bones
• FIBROUS BONE:
It is found in young fetal bone , but are common
in reptiles and amphibian
• DENTINE : occur in TEETH
• CEMENT ; TEETH
Structural Classification of Bones (cont..)

53. Structure of an Adult Long Bone
• A typical long bone has a shaft and two ends.
• Shaft consists of:
o Periosteum
o cortex
o medullary cavity
• Periosteum : is a fibrous thick membrane
covering the bones, except at their extremities.
It is made up of :
1. Outer fibrous layer
(containing a few fat cells)
2. Inner cellular layer (osteogenic
in nature)

54. Structure of an Adult Long Bone
(cont…)
• Cortex
It is made up of COMPACT BONE which gives its desired
strength to withstand all possible mechanical strains.
• Medullary cavity
The medullary cavity (medulla, innermost part) is the central
cavity of bone shafts where red bone marrow and/or yellow
bone marrow (adipose tissue) is stored.
Periosteum is permeated with nerves and blood
vessels that innervate and Nourish underlying bone.

55. Structure of an Adult Long Bone (cont…)

56. Developmental
Classification of Bones
1) Membranebones
2) Cartilaginous bones
3) Membrano-cartilaginous bones
Thereare three types of bones,on the
basis of developmentalpattern:

57.  In this process, calcium accumulation
occurs to help formation of bone tissue, process called
Calcification
 It begins at ossification centres.
 Involves the activity of osteoblasts which deposit inorganic
minerals in bone tissues.
SOME USEFUL TERMS
Ossification
[the process of mineralization of bones]

58. Ossification (continued)
• Ossification begins at pre-natal stage i.e. during fetal
development.
• It is of two types:
1.Intramembranous ossification
2.Endochondral ossification
• Membrane bones are formed by intramembranous
ossification
• Cartilaginous bones are formed by endochondral
ossification.

59. Intramembranous Ossification
•The bones ossifies in membranous tissues
•It begins at 8th week of development.
The bones are formed by the
condensation of mesenchymal
cells.
These cells proliferate and become
Osteoblasts.
Osteoblast function in calcification
of prebone matrix.
When these osteoblasts get trapped
in bone matrix, they become
Osteocytes.
Process Detail :

60. Lower jaw
Bones of skull
• Bones of the skull
• And facial bones
Membrane bones include :

61. Endochondral ossification
• Name indicates that the bones ossify in cartilage.
• First cartilaginous module is formed, which is then replaced
by bone.
• Begins 2nd month of development
Process Detail :
• Mesenchymal cells condense to form chondrocytes.
• Chondrocytes then undergo apoptosis at the diaphysis of
bone, where the primary ossification centre is formed.
• Here, calcification starts.
• Afterwards, secondary ossification centres are formed at the
epiphysis of bones.

62. Endochondral ossification (continued)

63. Primary ossification centre
form the Diaphysis (middle
section) of the bone.It is the
shaft of long bones.
Just after we are born,
Secondary ossification centers
are formed. Thesemake the
epiphysis (ends) of the long
bones.
Epiphysis
Diaphysis
Endochondral ossification (continued)

64. Endochondral Ossification (Continued)
Requires the presence of cartilage

65. • All the cartilage is
replaced by bone, except
that of epiphyseal plate
where growth take place.
• This plate continues to
grow new cartilage, which
is replaced by new bone.
Endochondral Ossification (Continued)

66. Cartilaginous bones include:
Scapula
Vertebra
Hip bone
• Long bones (bones of the limbs)
• Short bone (carpel and tarsal bones)
• Flat bones (ribs, sternum, scapula)
• Irregular bones (hip bone, vertebra)

67. Cartilaginous bones
include:

68. These include :
•Clavicle
•Mandible
•Occipital bone
•Temporal bone
•Sphenoid bone
Membrano-Cartilaginous bones :
Clavicle
Temporal
bone
Occipital
bone Mandible
These bones ossify partly in membrane
and partly in cartilage.

69. Blood Supply of Bones
• Blood is supplied to mature compact bone through the
Haversian canal (which was described earlier)
•A Haversian canal
generally contains one or
two capillaries.
•Volkmann's canals are
channels that assist with
blood and nerve supply
from the periosteum to the
Haversian canal

70. The sources of blood supply to a long Bone
Blood is supplied to long bones through
these arteries :
 Nutrient artery
 Periosteal artery
 Epiphyseal artery
 Metaphyseal artery
Blood Supply of Bones

71. Nutrient Artery
 It enters the shaft of bone, through the nutrient foramen.
 It is a single long artery, which is associated with one or two
veins.
 It has an ascending and descending branches in the medullary
cavity.
 Both these branches give off parallel branches which supply
the metaphysis and they also anastomose with epiphyseal
arteries.
 All these branches of nutrient artery supplies the inner two-
third of cortex(compact bone) and the entire medullary cavity.
Blood Supply of Bones

72. Blood Supply of Bones

73. Periosteal Artery
 They are small in size, but large in
number.
 They branch out of the periosteum
and supply outer one-third of the
cortex.
 They are numerous beneath the
muscle and ligamentous
attachements.
 They cover the entire bone length.
 So if the nutrient artery is damaged,
these vessels can temporarily serve
as primary blood supply
Blood Supply of Bones

74. Metaphysial Arteries
 Metaphysis of bone is a highly
vascular region of bone.
 Because too many blood vessels are
located here.
 The special blood vessels here, are
the metaphysial arteries
 These are end arteries i.e. they do
not anastomose with other arteries
 The characteristic feature of these
arteries is that they form hair pin
bends.
Blood Supply of Bones

75.  In these hair pin bends of metaphyseal
arteries, bacteria or emboli are trapped, and
cause osteomyelitis.
 Osteomyelitis : It is defined as the
inflammation of medullary cavity of bones
due to any bacterial infection
 mostly in children, because metaphysis is
found in the bones of children.
 In adults the metaphysial arteries
anastomose with the epiphysial arteries, so
adults do not have much chances of
osteomyelitis.
Blood Supply of Bones

76. Epiphysial Arteries
 In the epiphysis we have
periarticular vascular arcades.
 Defined as Blood vessels
around the joint.
 Found on the nonarticular
bony surfaces
 They supply the epiphysis.
 Some of these are arteries
and rest of them are venous
exists.
Blood Supply of Bones

77. Nerve Supply of Bones
• As with all other living
tissues, the bone is
innervated by peripheral
nerves so that it can co
ordinate with the central
nervous system .
• The important part of this
coordination is formed by the
sensory signals coming from
the bone .
• The brain reads these signals
and make necessary changes
to avoid any damage to
bones and other body tissues
.

78. Hilton’s Law
According to Hilton’s law,
“The nerve supplying the
muscle, also supply the joint
which assists in movement
caused by the muscle, and
also supply the skin above the
joint.”
Nerve Supply of Bones

79. “Nerves accompany the blood vessels”
 so if you have to find the specific nerve
supplying a specific bone, you will have to look for
nerves which accompany the arteries and veins of
a bone.
Most of the nerves coming to a bone are
sympathetic and vasomotor in function.
Some of the nerves are distributed to the
articular ends and periosteum of the different
bones.
COMMON FEATURES OE NERVE SUPPLY OF
BONES:
Nerve Supply of Bones

80. Functions of Bones
 The Skeleton provide a structural framework for the
attachment of soft tissues and organs.
 Provide protection. Ribs protect the heart and lungs, the
cranium protects the brain, the vertebrae encase the spinal
cord
 Bones are reservoirs of calcium and phosphate.They help to
maintain normal calcium and phosphate levels in the blood.
 Hematopoiesis occurs in the marrow of long bones.

81.  The bones of the skeleton store energy in the form of lipids in
areas of yellow bone marrow.
 Many bones have a role in translating the force generated by
skeletal muscle into mechanical leverage against other bones.
Functions of Bones

82. Some Interesting facts about bones
 Human bones are as strong as granite, in supporting weight. A block of bone
of the size of matchbox can support 9 tons. That is four times that of
concrete.
 The only born that is fully grown at the birth is in the ear, the stapes bone.
 Every second, our bone marrow produces two million red blood cells.
 More than half of the body’s bones are in the hands and feet.
 The only jointless bone in our body is the hyoid bone in our throat.
 Human and giraffes have the same number of bones in their neck.

83. REFFERENCES
• Study.com
• Wikipedia.org
• Webmd.com
• Teachmeanatomy.com
• Med-health.net
• And many others