secondary ossification

(noun)

A process that occurs after birth, and forms the epiphyses of long bones and the extremities of irregular and flat bones.

Related Terms

Examples of secondary ossification in the following topics:

  • Postnatal Bone Growth

    • Secondary ossification occurs after birth at the epiphyses of long bones and continues until skeletal maturity.
    • Secondary ossification occurs after birth.
    • During postnatal bone formation, endochondral ossification initiates bone deposition by first generating a structural framework at the ends of long bones, within which the osteoblasts can synthesize a new bone matrix.
    • Zone of bone deposition (ossification): The walls between the lacunae break down and the chondrocytes die.
    • Differentiate among the zones of development from cartilage to bone in postnatal ossification

  • Stages of Bone Development

    • Although bone initially forms during fetal development, it undergoes secondary ossification after birth and is remodeled throughout life.
    • The formation of bone during the fetal stage of development occurs by two processes: intramembranous ossification and endochondral ossification.
    • The steps in intramembranous ossification are:
    • Endochondral ossification begins with points in the cartilage called "primary ossification centers. " They mostly appear during fetal development, though a few short bones begin their primary ossification after birth.
    • Secondary ossification occurs after birth, and forms the epiphyses of long bones and the extremities of irregular and flat bones.

  • Development of the Skeleton

    • Early in gestation, a fetus has a cartilaginous skeleton that becomes skeletal bones in the gradual process of endochondral ossification.
    • Early in gestation, a fetus has a cartilaginous skeleton from which the long bones and most other bones gradually form throughout the remaining gestation period and for years after birth in a process called endochondral ossification.
    • Intramembranous ossification is the direct laying down of bone into the primitive connective tissue (mesenchyme).
    • Endochondral ossification involves cartilage as a precursor.
    • Chondrocytes in the primary center of ossification begin to grow (hypertrophy).

  • Embryonic and Fetal Bone Formation

    • During fetal development, bone tissue is created through intramembranous ossification and endochondral ossification.
    • The skull and vertebral column are produced by intramembranous ossification.
    • Unlike the other process of bone creation— endochondral ossification—intramembranous ossification does not involve cartilage.
    • Unlike intramembranous ossification, cartilage is present during endochondral ossification.
    • The first site of ossification occurs in the primary center of ossification, which is in the middle of diaphysis (shaft).

  • Fontanels

    • The ossification of the bones of the skull causes the fontanelles to close over a period of 18 to 24 months; they eventually form the sutures of the neurocranium.
    • This is called intramembranous ossification.

  • Sutures

    • As such, the degree of ossification can be a useful tool in determining age postmortem.

  • Fibrous Joints

    • Except for the mandible, all are joined together by sutures, semi-rigid articulations formed by bony ossification.

  • Cartilaginous Joints: Synchodroses

    • Depletion of chondrocytes due to apoptosis leads to less ossification, and growth slows down and later stops when the cartilage has been completely replaced by bone.

  • Raynaud's Phenomenon

    • Raynaud's syndrome, or secondary Raynaud's, occurs secondary to a wide variety of other conditions.
    • Secondary Raynaud's has a number of associations such as connective tissue disorders, eating disorders such as anorexia nervosa, and obstructive disorders.
    • Drugs which may cause secondary Raynaud's include beta-blockers, chemotherapeutics, and anthrax vaccines.
    • A careful medical history will often reveal whether the condition is primary or secondary.
    • Once this has been established, an examination is largely to identify or exclude possible secondary causes.

  • Oogenesis

    • At the start of the menstrual cycle, some 12-20 primary follicles begin to develop under the influence of elevated levels of follicle stimulating hormone (FSH) to form secondary follicles.
    • By around day 9 of the cycle, only one healthy secondary follicle remains, with the rest having been reabsorbed into the ovary.
    • This causes the secondary follicle to develop into a tertiary follicle, which then leaves the ovary 24–36 hours later.
    • An important event in the development of the tertiary follicle occurs when the primary oocyte completes the first meiotic division, resulting in the formation of a polar body and a secondary oocyte.
    • Immediately after meiosis I, the haploid secondary oocyte initiates meiosis II.