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By the end of this section, you will be able to:
  • Classify the different types of bones in the skeleton
  • Explain the role of the different cell types in bone
  • Explain how bone forms during development

Bone , or osseous tissue    , is a connective tissue that constitutes the endoskeleton. It contains specialized cells and a matrix of mineral salts and collagen fibers.

The mineral salts primarily include hydroxyapatite, a mineral formed from calcium phosphate. Calcification is the process of deposition of mineral salts on the collagen fiber matrix that crystallizes and hardens the tissue. The process of calcification only occurs in the presence of collagen fibers.

The bones of the human skeleton are classified by their shape: long bones, short bones, flat bones, sutural bones, sesamoid bones, and irregular bones ( [link] ).

 Illustration shows classification of different bone types. The sternum at the front, middle of the rib cage is a flat bone. The femur is a long bone. The patella is a sesamoid bone. The vertebrae are irregular bones, and the bones of the foot are short bones.
Shown are different types of bones: flat, irregular, long, short, and sesamoid.

Long bones are longer than they are wide and have a shaft and two ends. The diaphysis    , or central shaft, contains bone marrow in a marrow cavity. The rounded ends, the epiphyses , are covered with articular cartilage and are filled with red bone marrow, which produces blood cells ( [link] ). Most of the limb bones are long bones—for example, the femur, tibia, ulna, and radius. Exceptions to this include the patella and the bones of the wrist and ankle.

Illustration shows a long bone, which is wide at both ends and narrow in the middle. The narrow middle is called the diaphysis and the long ends are called the epiphyses. The epiphyses are filled with spongy bone perforated with holes, and the ends are made up of articular cartilage. A hollow opening in the middle of the diaphysis is called the medullary cavity.
The long bone is covered by articular cartilage at either end and contains bone marrow (shown in yellow in this illustration) in the marrow cavity.

Short bones , or cuboidal bones, are bones that are the same width and length, giving them a cube-like shape. For example, the bones of the wrist (carpals) and ankle (tarsals) are short bones ( [link] ).

Flat bones are thin and relatively broad bones that are found where extensive protection of organs is required or where broad surfaces of muscle attachment are required. Examples of flat bones are the sternum (breast bone), ribs, scapulae (shoulder blades), and the roof of the skull ( [link] ).

Irregular bones are bones with complex shapes. These bones may have short, flat, notched, or ridged surfaces. Examples of irregular bones are the vertebrae, hip bones, and several skull bones.

Sesamoid bones are small, flat bones and are shaped similarly to a sesame seed. The patellae are sesamoid bones ( [link] ). Sesamoid bones develop inside tendons and may be found near joints at the knees, hands, and feet.

The patella is a flat, teardrop-shaped bone.
The patella of the knee is an example of a sesamoid bone.

Sutural bones are small, flat, irregularly shaped bones. They may be found between the flat bones of the skull. They vary in number, shape, size, and position.

Bone tissue

Bones are considered organs because they contain various types of tissue, such as blood, connective tissue, nerves, and bone tissue. Osteocytes, the living cells of bone tissue, form the mineral matrix of bones. There are two types of bone tissue: compact and spongy.

Compact bone tissue

Compact bone (or cortical bone) forms the hard external layer of all bones and surrounds the medullary cavity, or bone marrow. It provides protection and strength to bones. Compact bone tissue consists of units called osteons or Haversian systems. Osteons are cylindrical structures that contain a mineral matrix and living osteocytes connected by canaliculi, which transport blood. They are aligned parallel to the long axis of the bone. Each osteon consists of lamellae , which are layers of compact matrix that surround a central canal called the Haversian canal. The Haversian canal    (osteonic canal) contains the bone’s blood vessels and nerve fibers ( [link] ). Osteons in compact bone tissue are aligned in the same direction along lines of stress and help the bone resist bending or fracturing. Therefore, compact bone tissue is prominent in areas of bone at which stresses are applied in only a few directions.

Questions & Answers

What is Staining?
Fazal Reply
what is biology
Biology is the study of life
what is biology
Ysabella Reply
biology is a study of living things
Biology is a diverse branch of science that deals with mostly living things
What happen when inhibit the transcription?
what is the effect of not doing sexual intercourse
what is the mechanism of cellular respiration
Rita Reply
what is enzyme
garry Reply
They are organic catalysts that alter the rate of chemical reactions in the body.
meaning they speed up reaction
Enzymes are forms of chemicals that are specialized in their own areas.(eg digestion of food)
Enzymes are organic catalysts
what is a cell
Praize Reply
Basic Functional Unit of Life
what is biology
Mordi Reply
biology is the study of living organisms and their interactions with one another and their environments
which of the following event does not occur during some stages of interface?
Bangha Reply
What is microfilaments
KHalid Reply
What is multicellular organisms
Ovie Reply
these are organisms with more than two cells
the process when a male toad fertilizer a female eggs is called what?
Ahrebe Reply
how did unicellular organisms form plants and animals or is it that different unicellular organisms formed plants and animald
YXNG Reply
name the components of faeces
undigested carbohydrate, fibre
what are unicellular organisms..?
they have only one cell
faeces contains many undigested food materials, after the food has been digested then it will be absorbed in the blood stream for assimilation.,......... but the remains toxic materials are stored in the rectum these toxic materials are the faeces and it contains bile salts, the polysaccharides .
unicellular organisms are the ones with only single cell.
thanks for your answers guys.
what is class bryophyta
Emefa Reply
how many stages do we have in glycolysis?
10 stages
the presence of a membrane enclosed nuclosed is a characteristics of what
Addai Reply
eukaryotic cell

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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