Download NAME: ADEBAYO TEMITOPE DEPARTMENT: MEDICINE AND

NAME: ADEBAYO TEMITOPE
DEPARTMENT: MEDICINE AND SURGERY
COURSE: ANA 203
LEVEL: 200L
MATRIC NO: 14/MHS01/004
HISTOLOGY OF HAVERSIAN SYSTEM
The term “ HAVERSIAN SYSTEM” refers to the arrangement of cylindrical-shaped
structural units called” OSTEONS” in compact bones, this inturn forms the substantial
part of the structure of the long bones of the human body. The osteons are closely packed
with osteocytes lined up in a concentric rings. This imparts a hard and dense texture to
the compact bones.
Cross Section of a haversian system
STRUCTURE OF A LONG BONE
Only compact bones have osteons as a basic structural; Spongy bones don’t have osteons
with the exception of the kneecap, wrist, and ankle bones, all the bones of the limbs are
long bones. They are called long bones as their length is more than their width. They are
composed of a shaft and two ends. The osteons run parallel to the long axis of a bone.
Structure of a long bone
HAVERSIAN SYSTEM STRUCTURE AND FUNCTION
The osteon comprises several channels which facilitate waste disposal, as well as
the supply of nutrients. These canaliculi also help the cells stay connected, as they
can make contact with the cytoplasmic processes of other osteocytes through the
canaliculi. Thus, the main function of this system is to facilitate the supply of
oxygen, as well as nutrients to the bone cells. It is the central canal that is
responsible for the nerve supply, as well as the vascular supply to the bone.
COMPONENTS OF A HAVERSIAN SYSTEM
An osteon comprises a long, hollow central canal that is surrounded by concentric
layers called “ LAMELLAE”. This central canal is reffered to as the
“HAVERSIAN CANAL” . The long axis of the osteon is parallel to the long axis of
the bone .Each osteon has a cylindrical structure that consists of the following
components:
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Haversian canals are located at the center. Small blood vessels that are
present in the central canal perform the function of supplying blood to the
osteocytes. The central canal also contains nerve filaments. These canals are
connected to each other by volkmann’s canals, which are transverse vessels
that run perpendicular to the long axis. Volkmann’s canals also connect the
blood vessels that are present in the central Haversion canals to the
periosteum ( dense tissue covering the outer surface of the bone).
Volkmann’s canal are not surrounded by concentric lamellae. The haversian
canal is surrounded by the following structures;
Lamellae are concentric ring of a strong bone matrix . Mineral salt and
collagen fibers lend strength to the matrix The collagen fibers in a lamella
in an osteon run parallel to one another, but the collagen fibers run in
different direction in the lamella that lies next to it. This arrangement also
strengthens the osteon. It is the presence of mineral salt such as calcium and
phosphates in the matrix that makes the bone hard, whereas collagen fibers
strengthen the matrix.
Between the lamellae are small spaces called lacunae. Osteocytes are
located within these small spaces.
Tiny channels called canaliculi connect the lacunae. Nutrients are supplied
to the osteocytes via these channels. Waste products also leave the
osteocytes through these channels.
The remnants of pervious concentric lamellae can be found between the
osteons. These are referred to as interstitial lamellae.
On a concluding note, the haversion system or the osteon plays a vital role,
as it facilitates the supply of oxygenated blood and nutrient to the bone.
Moreover, the network of canaliculi also facilitates the passage of
substances between the blood vessels and mature bone cells.
STRUCTURE OF THE HAVERSIAN SYSTEM