a. Use of Bony Tissues to Form an Individual Bone.
(1) Cortex. The cortex is the outer layer of the individual bone. It is made up
of compact (dense) bony tissue.
(2) Medulla. The medulla is the central portion of the individual bone. It
generally consists of cancellous (spongy) bone tissue. In some bones, particularly long
bones, the medulla may include a space without any bony tissue. This space is called
the medullary or marrow cavity.
b. Marrow. Marrow serves as a filler of the inside of bones. There are two
types of bone marrow--yellow bone marrow and red bone marrow. Yellow bone marrow
is mostly yellow fat tissue. Red bone marrow is the only site in adults for the formation
of red blood cells (hematopoiesis).
c. Named Parts of an Individual Long Bone.
(1) Shaft (diaphysis). The shaft is the central portion of a long bone. Here,
the cortex is thickened as required by applied physical stresses.
(2) Ends (epiphyses). The ends of long bones are made up mainly of
cancellous (spongy) bone tissue. An articular cartilage covers each area where a bone
contacts another bone(s). This articular cartilage is made up of hyaline cartilage tissue
and provides a smooth surface for motions.
d. Periosteum. The periosteum is a covering of the bone surface area not
covered by articular cartilage. It has two layers--the innermost layer and the fibrous
(1) The innermost layer, which lies against the outer surface of the bone,
consists of bone-forming cells (osteoblasts). It is the osteogenic (bone-forming) layer.
(2) The outermost layer is a FCT (fibrous connective tissue) layer.
(3) The periosteum is well supplied with blood vessels and sensory-type
e. Blood Supply of an Individual Bone. A system of blood vessels enters and
spreads out through the periosteum. Additional blood vessels, called "nutrient vessels,"
penetrate the cortex of the bone and spread out through the marrow. The passageways
for penetration of these vessels are called the nutrient canals.