types of bone, structure of bones

1. Bone Structure and
Types
Sukhbir Kaur

2. Introduction:
• Bone: It is a rigid organ that constitutes part of the vertebrate
skeleton.
• Function: To support and protect the various organs of the body.
• Bones come in a variety of shapes and sizes and have a complex
internal and external structure.
• They are lightweight yet strong and hard, and serve
multiple functions.
• In the human body at birth, there are over 270 bones , but many
of these fuse together during development, leaving a total of 206
separate bones in the adult not counting numerous
small sesamoid bones.
• The largest bone in the body is the femur or thigh-bone, and the
smallest is the stapes in the middle ear.
• Bone tissue is a hard tissue, a type of dense connective tissue. It
has a honeycomb-like matrix internally, which helps to give the
bone rigidity.

3. Bone Structure
Ø Matrix: It is made up of (90 and
95%) collagen fibers , and the ground
substance. It is composed of organic and
inorganic matter.
v Inorganic component is made up
of hydroxyapatite crystals (this is the bone
mineral that gives bones their rigidity and
tensile strength) and
v Organic component collagen, an elastic
protein which gives compressive strength.
The collagen of bone is known as ossein.
Ø Bone is formed by the hardening of this
matrix around entrapped cells.

4. Bone Tissue and Composition
• Bone tissue, or osseous tissue, is the
major structural and
supportive connective tissue of the
body.
• Bone tissue forms the rigid part of
the bones that make up the skeleton.
• Bone tissue refers specifically to
the bone mineral matrix that forms the
rigid sections of the organ, and the
bone cells within it.
• There are three types of bone tissue:
cortical bone, cancellous bone and
subchondral bone.

5. Types of Bone Tissue
1.Cortical Bone
• The hard outer layer of bones
composed of cortical bone also
called COMPACT BONE.
• Cortical referring to the outer
(cortex) layer. The hard outer layer
gives bone its smooth, white, and
solid appearance, and accounts for
80% of the total bone mass of an
adult human skeleton.

6. Also known as trabecular or
spongy bone tissue, is the internal
tissue of the skeletal bone and is
open cell porous network. Thin
formations of osteoblasts covered
in endosteum create an irregular
network of
spaces, known as trabeculae.
Within these spaces are bone
marrow and stem cells that give
rise to platelets, RBC’s and
WBC’s.
2.Cancellous Bone

7. 3.Subchondral bone/tissue
• Subchondral bone” is bone that sits
underneath cartilage in a joint.
Subchondral bone is found in large
joints like the knees and hips, as well
as in small joints like those of the
hands and feet.
• This is the smooth tissue at the ends of
bones, which is covered with another
type of tissue called cartilage.
• The function of the subchondral bone
is to attenuate forces generated
through locomotion, with the
compact subchondral bone plate
providing firm support and the
subchondral trabecular component
providing elasticity for shock
absorption during joint loading.

8. Osteon and Structure Of Cortical Bone
• Cortical bone consists of multiple
microscopic columns, each called
an osteon.
• It consists of concentric rings called
lamellae which are formed by the
osteoblasts that eventually differentiate
into osteocytes. These osteocytes are
located along the lamellae in spaces
called Lacunae.
• In the centre of the osteon is a canal
called the Haversian canal. This contains
the blood vessels, lymph vessels and
neurons.

9. • Bone contains many of these
individual osteons. The adjacent
Haversian canals of these
osteons are connected by
Volkmann’s canals.
• The columns are metabolically
active, and as bone is
reabsorbed and created, the
nature and location of the cells
within the osteon will change.

10. Bone marrow is the flexible tissue in the interior
of bones. In humans, red blood cells are produced by
cores of bone marrow in the heads of long bones in a
process known as haematopoiesis.
Bone marrow is also a key component of
the lymphatic system, producing the lymphocytes that
support the body’s immune system.
• The two types of bone
marrow are "red
marrow“, which consists
mainly
of haematopoeitic tissue
and "yellow marrow“,
which is mainly made up
of fat cells.
RBC’s, platelets, and
most white blood cells
arise in red marrow. Both
types of bone marrow
contain numerous blood
vessels and capillaries.
Bone marrow

11. Bone Marrow
• Also known as myeloid tissue, red
bone marrow, can be found in almost
any bone that holds cancellous tissue.
• In new-borns, all such bones are
filled exclusively with red marrow
or haematopoietic marrow.
• In adults, red marrow is found
mainly in the flat bones, such as
the pelvis, sternum,
cranium, ribs, vertebrae and scapula,
and in the cancellous material at
the epiphyseal ends of long bones
such as the femur and humerus.

12. At birth, all bone marrows are red. With age, more and more of it is converted to the yellow
type; only around half of adult bone marrow is red.
Yellow marrow is found in the medullary cavity, the hollow interior of the middle portion of
long bones.
In cases of severe blood loss, the body can convert yellow marrow back to red marrow to
increase blood cell production.

13. Function of the Bone cells is to work in harmony to
maintain a balance between bone formation and
resorption, ultimately to control bone structure and
function. They are responsible for the growing, shaping, and
maintenance of bones.
4 types:
• Osteoblast: It is found in the growing portions of bone,
including endosteum and periosteum and is responsible
for forming new bone.
• Osteoclast: Osteoclasts are the cells responsible for bone
resorption, thus they break down bone. Osteoclasts are
large cells with multiple nuclei located on bone surfaces.
• Osteocyte: Maintain mineral concentration of matrix.
• Osteoprogenitor cells: Develop into osteoblasts.
Bone is constantly remodelled by the resorption of
osteoclasts and created by osteoblasts.
Types of Bone Cells and their functions

14. Bone Cells :^I
• Bone is a metabolically active tissue composed of several types
of cells.
• Osteoblasts are mononucleate bone-forming cells. They are
located on the surface of osteon seams and make a protein mixture
known as osteoid, which mineralizes to become bone.
• Osteocytes are mostly inactive
osteoblast.They originate from
osteoblasts that have migrated
into and become trapped and
surrounded by bone matrix that
they themselves produced. The
spaces they occupy are known
as lacunae.

15. There are five types of bones in the human body: Long, Short, Flat, Irregular, and Sesamoid.
TYPES OF BONES

16. Types of Bones
1.Long bones are much longer than
they are wide. They consist of 3
different sections
• Epiphysis- contains spongy bone or
cancellous bone and also contain red
bone marrow that synthesise RBC’s.
• Metaphysis- contains an important
section i.e. Epiphyseal plate
responsible for lengthening and
elongating long bone as organism
actually grows.
• Diaphysis- long, curved shaft that
contains compact bone that is
responsible for giving bone, its
strongness.

17. They are capable of resisting very
high tensile and compressive forces
due to which long bones support
majority of our body’s weight. We
have many different types of long
bones in our body.
Example : i) Clavicle (collar bone)
ii) Humerus, radius, ulna (arm)
iii) Femur, tibia, fibula (leg)
iv) Metacarpals
Long Bone (cont...)

18. 2.Short bones are roughly cube-shaped, and have only a
thin layer of compact bone surrounding a spongy interior.
They are as long as wide. They function by providing
support as well as stability to other bones. They are located
at the wrist (carpals) and ankle (tarsals).
3.Flat bones are thin and generally curved, with two
parallel layers of compact bones sandwiching a layer of
spongy bone. They have a large surface area.
They : a) protect our internal organs and tissue
b) Serve as attachment point for muscle because of their
large surface area.
Example : i) Skull (cranium)- flat bones fuse here to protect
our brain.
ii) Rib cage and Sternum- this acts not only as attachment
point of muscle but also protect heart, lungs and vascular
tissue in this region.
iii) Scapula (shoulder blade bone)
iv) Pelvis (hip bone)

19. 4.Sesamoid bones are bones embedded in
tendons. This bone is in shape of sesame seed.
Example of sesamoid bone is Patella (knee cap).
5.Irregular bones do not fit into the above
categories. They consist of thin layers of compact
bone surrounding a spongy interior. As implied by
the name, their shapes are irregular and
complicated. Thus, they have a unique shape and
function. They help in protection and support of
body.
Example : i) Maxilla (upper jaw bone) and
Mandible (lower jaw bone)- they help to eat and
ingest food.
ii) Sacrum
iii) Vertebrae (cervical and lumbar)- they are
responsible for protecting our spinal cord.

20. Bones consist of living cells embedded in a mineralized organic matrix.
This matrix consists of organic components, mainly Type I Collagen –
"organic" referring to materials produced as a result of the human body –
and inorganic components, primarily hydroxyapatite and other salts
of calcium and phosphate. The collagen fibers give bone its tensile strength,
and the interspersed crystals of hydroxyapatite give bone its compressive
strength.
Collagen consists of strands of repeating units, which give bone tensile
strength, and are arranged in an overlapping fashion that prevents shear
stress. The function of ground substance is not fully known.
Two types of bone can be identified microscopically according to the
arrangement of collagen:
Woven and lamellar.

21. Woven Bone
Woven bone, (also known
as fibrous bone) which is
characterized by a haphazard
organization of collagen fibers that
occurs initially in all fetal bones. It
is mechanically weaker, with a
smaller number of randomly
oriented collagen fibers, but forms
quickly; it is for this appearance of
the fibrous matrix that the bone is
termed woven. It is soon replaced
by lamellar bone.
After a fracture, woven bone forms
initially and is gradually replaced by
lamellar bone during a process known
as "bony substitution." Compared to
woven bone, lamellar bone formation
takes place more slowly.

22. It has a regular parallel alignment of
collagen into sheets ("lamellae") and
is mechanically strong. It is highly
organized in concentric sheets with a
much lower proportion of osteocytes
to surrounding tissue. It makes its
first appearance in humans in
the fetus during the third trimester, is
stronger and filled with many
collagen fibers parallel to other
fibers in the same layer (these
parallel columns are called osteons).
Lamellar Bone

23. Thank you