Structure of Bone By,M. Thiru murugan Structure of bone: The basic structure of bones is bone matrix, which makes up the underlying rigid framework of bones, composed of both compact bone and spongy bone. The bone matrix consists of tough protein fibers, mainly collagen, that become hard and rigid due to mineralization with calcium crystals. Bone matrix is crossed by blood vessels and nerves and also contains specialized bone cells that are actively involved in metabolic processes. Bone matrix provides bones with their basic structure. Notice the spongy bone in the middle, and the compact bone towards the outer region. The osteon is the functional unit of compact bone. The microscopic structural unit of compact bone is called an osteon, or Haversian system. Each osteon is composed of concentric rings of calcified matrix called lamellae (singular = lamella). Running down the center of each osteon is the central canal, or Haversian canal, which contains blood vessels, nerves, and lymphatic vessels. These vessels and nerves branch off at right angles through a perforating canal, also known as Volkmann’s canals, to extend to the periosteum and endosteum Bone Cells: Bones are made of four main kinds of cells: Osteoblasts Osteocytes Osteoclasts Lining cells. Osteoblasts: are responsible for making new bone as your body grows. They also rebuild existing bones when they are broken. To make new bone, many osteoblasts come together in one spot then begin making a flexible material called osteoid. Minerals are then added to osteoid, making it strong and hard. When osteoblasts are finished making bone, they become either lining cells or osteocytes. Osteocytes: Mature bone cells are called osteocytes Osteoclasts: Bone-destroying cells & Break down bone matrix for remodelling and release of calcium Lining cells: are very flat bone cells. These cover the outside surface of all bones and are also formed from osteoblasts that have finished creating bone material. These cells play an important role in controlling the movement of molecules in and out of the bone Bone Tissues: Bones consist of different types of tissue, including periosteum, compact bone, spongy bone, and bone marrow. Periosteum. Cortical, or Compact Bone. Cancellous, or Spongy Bone. Bone Marrow. 1.Periosteum: The periosteum is a tough membrane that covers and protects the outside of the bone. 2.Compact bone: Below the periosteum, compact bone is white, hard, and smooth. It provides structural support and protection. 3.Spongy bone: The core, inner layer of the bone is softer than compact bone. It has small holes called pores to store marrow 4. Bone Marrow: The inside bones are filled with a soft tissue called marrow. There are 2 types of bone marrow: red and yellow. Red bone marrow is where all new RBC, WBC, and platelets are produced. Red bone marrow is found in the center of flat bones such as your scapula and ribs. Yellow marrow is made mostly of fat and is found in th

1. Structure of Bone

2. • Structure of bone:
• The basic structure of bones is bone matrix, which makes up the
underlying rigid framework of bones, composed of both compact
bone and spongy bone.
• The bone matrix consists of tough protein fibers, mainly collagen,
that become hard and rigid due to mineralization with calcium
crystals.
• Bone matrix is crossed by blood vessels and nerves and also contains
specialized bone cells that are actively involved in metabolic
processes.
• Bone matrix provides bones with their basic structure. Notice the
spongy bone in the middle, and the compact bone towards the outer
region. The osteon is the functional unit of compact bone.

3. • The microscopic structural unit of compact bone is called
an osteon, or Haversian system.
• Each osteon is composed of concentric rings of calcified
matrix called lamellae (singular = lamella).
• Running down the center of each osteon is the central
canal, or Haversian canal, which contains blood vessels,
nerves, and lymphatic vessels.
• These vessels and nerves branch off at right angles
through a perforating canal, also known as Volkmann’s
canals, to extend to the periosteum and endosteum

4. • Bone Cells: Bones are made of four main kinds of cells:
1. Osteoblasts
2. Osteocytes
3. Osteoclasts
4. Lining cells.
• Osteoblasts: are responsible for making new bone as your body
grows.
• They also rebuild existing bones when they are broken. To make new
bone, many osteoblasts come together in one spot then begin making a
flexible material called osteoid.
• Minerals are then added to osteoid, making it strong and hard. When
osteoblasts are finished making bone, they become either lining cells or
osteocytes.

5. • Osteocytes: Mature bone cells are called osteocytes
• Osteoclasts: Bone-destroying cells & Break down bone
matrix for remodelling and release of calcium
• Lining cells: are very flat bone cells.
• These cover the outside surface of all bones and are also
formed from osteoblasts that have finished creating bone
material.
• These cells play an important role in controlling the
movement of molecules in and out of the bone

7. • Bone Tissues:
• Bones consist of different types of tissue,
including periosteum, compact bone, spongy
bone, and bone marrow.
1.Periosteum.
2.Cortical, or Compact Bone.
3.Cancellous, or Spongy Bone.
4.Bone Marrow.

9. 1.Periosteum: The periosteum is a tough membrane that covers
and protects the outside of the bone.
2.Compact bone: Below the periosteum, compact bone is white,
hard, and smooth. It provides structural support and protection.
3.Spongy bone: The core, inner layer of the bone is softer than
compact bone. It has small holes called pores to store marrow
4. Bone Marrow: The inside bones are filled with a soft tissue
called marrow.
• There are 2 types of bone marrow: red and yellow.
• Red bone marrow is where all new RBC, WBC, and platelets
are produced.

10. • Red bone marrow is found in the center of flat bones
such as your scapula and ribs.
• Yellow marrow is made mostly of fat and is found in
the hollow centers of long bones, such as the femur
bones.
• Yellow bone marrow does not make blood cells & helps
to store fat.
• Both yellow and red bone marrow have many small and
large blood vessels and veins running through them to
let nutrients and waste in and out of the bone.

11. • At birth, all the marrow in body
was red marrow, which made
lots and lots of blood cells to
help the body to grow bigger.
• As you got older, more and
more of the red marrow was
replaced with yellow marrow.
• The bone marrow of full grown
adults is about half red and half
yellow.

12. Bone Marrow

13. Structure of a Long Bone:
• Diaphysis: Shaft & Composed of compact bone
• Epiphysis: Ends of the bone & Composed mostly
of spongy bone
• Periosteum: Outside covering of the diaphysis &
Fibrous connective tissue membrane
• Endosteum: inner layer of bone
• Arteries: Supply bone cells with nutrients

14. • Articular cartilage: Covers
the external surface of the
epiphyses
• Made of hyaline cartilage
• Medullary cavity: Cavity of
the shaft
• Contains yellow marrow
(mostly fat)
• Contains red marrow (for
blood cell formation)