Bone metabolism disorders

1. Structure
and types
of bone

2. Bone and its composition
• Bone is specialized dense connective
tissue, where the matrix is impregnated
with calcium salts
• High amount of calcium salts making it
rigid and hard .
• Organic material like collagen fibers make
the bone tough and resilient
• Highly vascular and have greater power of
regeneration.

3. Divisions of the skeletal system
 The scientific study of bones is known as Osteology.
Total axial bone - 80 Total appendicular bone - 126
60
60

4. • Functions of bone:
• 1. Support- framework that supports
body & cradles organs
• 2. Protection- skull, vertebra, thorax
• 3. Movement- gives space for muscles
attachment for movement
• 4. Mineral storage- calcium and phosphorus
• 5. Hematopoiesis- blood cell formation

5. Classification of bone
A. According to shape
B. According to development
C. According to region of body
D.According to structure of bone.

7. Classification of Bones
7. Accessory bone

8. B
C

9. D

10. A. On the basis of shape :
1. Long bones:
 A long bone is one that is cylindrical in shape, being
longer than its width and thickness.
 Found in
arms (humerus, ulna, radius)
legs (femur, tibia, fibula),
fingers (metacarpals, phalanges)
toes (metatarsals, phalanges).
Note – long bones are also grouped under -
a. Typical long bone : Humerus, Radius, Ulna & Femur
etc.
b. Miniature long bones: Metacarpals, Metatarsals &
Phalanges.
c. Modified long bones: Clavicle & body of Vertebra.

11.  note – the clavicle is the only long bone which
lies horizontally, ossify mainly in membrane
and doesn’t contain medullary cavity
extra

13. 2. Short bone:
• A short bone is one that is
cuboidal in shape, being
approximately equal in length,
width, and thickness.
• Example of short bone are carpal
and tarsal bone.

14. 3. Flat bones
• A “flat bone” is typically thin, shallow plate like and
often curved.
• Examples include the cranial (skull) bones, the
scapulae (shoulder blades), the sternum, and the
ribs.
• Flat bones form boundaries of certain body cavities
like cranium, thoracic cavity

15. 4. Irregular bone
• An irregular bone is one that does not have any easily
characterized shape and therefore does not fit any
other classification.
• Vertebra, hip bone and bone at the base of skull.

16. 5. Sesamoid bones
• is a small, round bone that, as the name suggests,
is shaped like a sesame seed.
• These bones form in tendons and joint capsule.
• The function of a sesamoid bone is to reduce
friction on the tendon;
• it can also alter the direction of pull of a tendon.
• e.g. patella, pisiform ,fabella.

17. extra

18. extra

19. 6. Pneumatic bone:
• Those irregular bones which has presence
of large air spaces in their bones which
make them light in weight
• Pneumatic bone forms the major portion of
skull
• Eg. Maxilla ,sphenoid, ethmoid etc.

20. 7. Accessory bone:
• These bones are not generally present in the body.
• If present, do not cause any harm and may confuse it with a
fractured bone.
• May appear as extra ossification centre in the skull sutures viz.
sutural or wormian bone.
• May be due to nonfusion of an epiphysis of the bone like os
trigonium in talus, in navicular etc.

22. B. Developmental classification
• Membrane bones: ossify in membrane, derived from
mesenchymal condensations. Eg. Bones of vault of skull
and facial bones.
• Cartilaginous bones: ossify in cartilage and derived from
the preformed cartilaginous models. Eg. Bones of limbs,
vertebral column and thoracic cage
• Membrano-cartilaginous bones: partly in membrane and
partly in cartilage. e.g clavicle, mandible, occipital,
temporal, sphenoid.

23. C. On the basis of Region
• Axial skeleton-
skull, vertebral
column and ribs
and sternum
• Appendicular
skeleton- bones of
the limbs.

24. D. On the basis of Structure
• Macroscopically-
a. Compact/cortical bone -
 dense in texture.
 Found where stresses are limited in
direction
 Compact bone covers spongy part
of bone.
 Example – in the cortex of long
bones .
B. Spongy/cancellous/trabecular
bone -
 The part of bone where there is
more empty space and less bone
tissue
 Found where stresses are weaker
or multi-directional.
 Spongy bone part is surrounded by
compact bone.
 Eg. The inner part of Long Bones
Note – All bones of body consists of both
compact and spongy bone except inferior
nasal concha which consists of only
spongy bone.

25. D. On the basis of Structure
Microscopically-
a. fibrous bone-
– These have more fibers in them and Also known as
immature bones eg. Fetus bone.
a.lamellar bone – all mature bones of human.
b.Woven bone – bones created after fracture.
c.dentine – Cementum is a specialized calcified
substance covering the root of a tooth. It hardens to act as
an adhesive glue.
D. Cement - one of the hard tissues of the teeth which
constitutes most of its bulk

28. 1. Shaft (diaphysis) :
– long, cylindrical elongated
middle part
– have thick shell of compact
bone enclosing medullary
cavity.
2. Ends (Epiphysis) –
– Upper and lower ends are
often knobby (expanded)
– largely made up of
cancellous bone covered by
a thin shell of compact
bone.
– Ends of long bone are
covered by an articular
Parts of a typical adult long bone:
 Consists of a Shaft and two ends.

29. • Parts of growing young
bone
• Epiphysis: two ends (proximal
and distal) of bone
• Diaphysis: shaft of long bone
ossify
• Metaphysis: epiphysial end of
diaphysis, zone of active
growth.
• Epiphysial plate of cartilage
separate epiphysis from
metaphysis. it causes increased
length of bone.

30. General structure of bones
1. Periosteum –
• Is an outer thick sheath of
dense regular connective tissue
covering of the bone except
articular surface.
• Two layers –
– Outer fibrous layer
– Inner cellular layer
(osteoprogenic)
2. Endosteum –
 inner thin cellular membrane
that lines the medullary cavity
of the shaft.
 Single layer and have
osteoblasts and
Osteoprogenitor cells.

31. General structure of bones
3. Cortex
 made up of compact bone
that provides strength.
4. Medullary cavity
 Is filled with the red
marrow or yellow marrow.

32. • Blood supply of bones:
For long bone,
• Epiphysial artery
• Metaphysial artery
• Periosteal artery
• Nutrient artery

33. - composed of cells, ground substance and fibers
- The ground substance and fibers together form
the bone matrix
Cells
Bone Matrix
-Osteoprogenitor
-Osteoblast
-Osteocyte
-Osteoclast
Organic matter Inorganic matter
-Collagen Type I
-Proteoglycan
-Glycoprotein
-Ca & P in the form of
calcium hydroxyapatite
Arranged in lamella
Bone
Bone

35. • Osteoprogenitor Cells
– Pluripotent cell located in mesenchyme, periosteum and
endosteum
– Can proliferate and convert into osteoblasts whenever there
is need for bone formation.
• Osteoblast
– Immature cells; bone forming cells .
• Osteocyte
– are cells of mature bone and found in cavities (lacunae and
canaliculi) within the matrix
• Osteoclast
– They are bone removing cell which is essential for
maintaining the proper shape of growing bone thus
involved in the resorption and remodeling of bone tissue.

37. Histology of Bone Tissue

38. Histology of Compact Bone
• Compact bone consists of
– Lamellae of collagenous sheets
– Haversian system or osteons
• Lamellae –
– A. Concentric lamellae surround the
Haversian canal
– B. Interstitial lamellae lie between osteons.
These are remnants of old outer
circumferential lamellae or old haversian
system.

39. Histology of Compact Bone
• Haversian system (osteon)
• Compact bone is arranged in repeating units called osteons
or Haversian systems.
• It consists of –
– a central canal k/a Haversian canal which contain blood
vessels, lymphatic vessels, nerves & runs parallel to the
axis of the bone.
– Surrounding this canal are concentric rings of lamellae
(4-20 in number) along with the calcified matrix.
• The osteocytes are located between the lamellar rings in
lacunae
• The lacunae communicates with one another in between &
across the lamellae, and with the central canal by numerous
radiating canaliculi.

40. Compact Bone

43. No true Osteons.
Spongy Bone
• Spongy (cancellous) bone does not contain osteons. It
consists of trabeculae surrounding many red marrow
filled spaces.
• It forms most of the structure of short, flat, and
irregular bones, and the epiphyses of long bones.
• Spongy bone tissue is light and supports and protects
the red bone marrow.

44. ossification
Ossification is the process of formation of bone.
Principle of Ossification
Primary ossification center –before birth
Secondary ossification center- after birth
Rule 1 - Ossification center which appears first is usually
last to fuse except for Fibula.
Rule 2 - If epiphysis develops from more than one centers
the various centers coalesce before union occurs with the
diaphysis.
Rule 3 - When epiphysis fuses with the diaphysis the
growth ceases.
Rule 4- the direction of nutrient artery is always away from
the growing end.

45. THANK YOU!!!