TISSUE TYPES
2- COMPACT and SPONGY BONE TISSUES (cont.)
Lets have a look at these two types of bone tissue in
more details:
Click inside the blue square to magnify the chunk of bone.
Both types of bone tissues compact (A)
and spongy (B) are observed on this section of bone.
You can magnify any part of the drawing simply by clicking on it. If you want to see the structures described
in the text, you will have to magnify the different regions of this drawing.
Compact bone tissue:
The compact bone tissue is made mostly of bone matrix deposited in layers 3-7 micrometers thick.
These layers of bone matrix are called lamellae (J, K, L).
The lamellae of compact bone
are disposed in three different patterns:
- the concentric lamellae (J) are arranged concentrically around longitudinal
vascular channels to form the osteons (= cylindrical units of the compact bone tissue H);
they have been colored to differentiate them easily from the two other types of lamellae.
- the interstitial lamellae (K) fill the spaces between osteons
- the circumferential lamellae (L) run around the circumference of the bone. The inner circumferential
lamellae are located on the inner side of the compact bone tissue and the outer circumferential lamellae
are located on the outside.
The bulk of the compact bone tissue is made of cylindrical units: the
osteons (H).
You can see 6 osteons. Click on any parts of the compact bone tissue
to magnify the osteons (the osteons have been colored in the magnified drawings).
The osteons are made of osteocytes (I) arranged in circles
and concentric layers of bone matrix (= concentric lamellae J).
The concentric lamellae are like
tubes of different size fitting inside each other to make an osteon.
Running through the core of an
osteons and along its axis is the central canal
(= Haversian canal E) that contains blood vessels and nerves.
Perforating canals (= Volkmann's canal F)
lie perpendicular to the haversian canals.
Perforating canals connect blood vessels and nerves of the central canals
with those outside the bone
and with those inside the medullary cavity and inside the cavities of the spongy bone tissue
Spongy bone tissue:
The spongy bone tissue does not contain osteons. It consists of layers of bone matrix
(= lamellae M) arranged in an irregular latticework of
thin plates of bone called trabeculae. The spaces within the trabeculae are filled with red bone marrow
and blood vessels. These blood vessels are connected to blood vessels found in the Volkman's and haversian canals.
Periosteum:
The periosteum (D) is lining the outer surface of bones. It is made of a tough outer fibrous layer (in black)
and a thin inner osteogenic layer (in orange).
Endosteum:
The endosteum (C)is colored in green. It is lining the outside of the trabeculae and the wall
of the Haversian and Volkmann's canals.
