circumventricular organs

(noun)

So named because they are positioned at distinct sites around the margin of the ventricular system of the brain. They are among the few sites in the brain which have an incomplete blood-brain barrier and, as a result, can directly sense the concentrations of various compounds, particularly peptide hormones, in the bloodstream.

Related Terms

Examples of circumventricular organs in the following topics:

  • Circumventricular Organs

    • Circumventricular organs are situated adjacent to the brain ventricles and sense concentrations of various compounds in the blood.
    • Circumventricular organs (CVOs) are positioned at distinct sites around the margin of the ventricular system of the brain.
    • As a result, neurons located in circumventricular organs can directly sense the concentrations of various compounds, particularly peptide hormones, in the bloodstream without the need for specialized transport systems that move those compounds across the blood-brain barrier.
    • These organs include:
    • Vascular organ of lamina terminalis: Responsible for the homeostatic conservation of osmolarity.

  • Blood-Brain Barrier

    • Bacteriologist Paul Ehrlich observed that chemical dye injected into an animal would stain all of its organs except for the brain.
    • In a later experiment, his student Edwin Goldmann found that when dye is directly injected into the cerebrospinal fluid (CSF) of animals' brains, the brains were dyed while the rest of the organs were unaffected.
    • These include the circumventricular organs such as the area postrema, median eminence of the hypothalamus, pineal gland, and the posterior pituitary.

  • Levels of Organization

    • Living organisms are made up of four levels of organization: cells, tissues, organs, and organ systems.
    • An organism is made up of four levels of organization: cells, tissues, organs, and organ systems.
    • Most organs contain tissues such as parenchyma (used to perform the organ functions),  stroma (connective tissue specific to organs) and epithelial.
    • An organ system is a collection of organs that that work together to perform a similar function.
    • An organism contains organ systems made up of organs that consist of tissues, which are in turn made up of cells.

  • Organ Transplants

    • Organ transplantation involves moving organs between bodies (or from donor sites on patients' bodies) for the purpose of replacing recipients' damaged or absent organs.
    • Tissue transplants occur much more frequently than organ transplants.
    • Organ donors may be living or brain dead.
    • Organ trafficking is one problem.
    • Organ transplants are not regulated by the FDA.

  • Tissues in Levels of Organization

    • The next level is the organ system level.
    • Many organs working together to accomplish a common purpose create an organ system.
    • Cells form tissues, and tissues form organs.
    • Organs that fulfill related functions are called organ systems.
    • An organism is made up of interconnected organ systems.

  • Life Functions

    • Cells are the basic unit of life that can be found in every living organism. 
    • Multicellular organisms are typically made up of organ systems, organs, tissues, and cells.
    • More complex organisms are capable of communication.
    • Because viruses exhibit some but not all characteristics of organisms, they cannot be fully considered living things.
    • Beyond these zones are the "zones of intolerance," where life for that organism is impossible.

  • Body Cavities

    • Vertebrates have fluid-filled spaces called body cavities that contain the organs.
    • They usually contains protective membranes and sometimes bones that protect the organs.
    • The organs within the ventral cavity are also called viscera.
    • It houses the primary organs of the cardiovascular and respiratory systems, such as the heart and lungs, but also includes organs from other systems, such as the esophagus and the thymus gland.
    • The abdominal cavity is not contained within bone and houses many organs of the digestive and renal systems, as well as some organs of the endocrine system, such as the adrenal glands.

  • Lymphoid Tissue

    • Lymphoid tissue consists of many different organs playing a role in the production and maturation of lymphocytes in the immune response.
    • The tissues of lymphoid organs are different than the tissues in most other organ systems because different tissues within the system vary considerably based on cell cycle proliferation of lymphocytes.
    • The central or primary lymphoid organs generate lymphocytes from immature progenitor cells, such as lymphoblasts.
    • Secondary or peripheral lymphoid organs maintain mature naive lymphocytes until an adaptive immune response is initiated.
    • The other lymph nodes that are organized around other lymph trunks, such as those in the abdomen and intestine develop afterwards from nearby veins.

  • Anatomy of the Male Reproductive System

    • The male reproductive system includes external (penis, scrotum, epididymus, and testes) and internal (accessory) organs.
    • The organs of the male reproductive system are specialized for three major functions:
    • The penis is the male organ for sexual intercourse and urination.
    • The internal organs of the male reproductive system are called accessory organs.

  • Defining Anatomy

    • Systemic anatomy focuses on the anatomy of different organ systems, such as the respiratory or nervous system.
    • Surface anatomy is also widely used to gauge the position and structure of deeper organs, tissues, and systems.
    • Histology, the study of the organization and details of biological tissues
    • The human body has many layers of organization.
    • The history of anatomy has been an evolving understanding of organs and structures in the body.