polar body

(noun)

A small haploid cell formed concomitantly as an egg cell during oogenesis, but which does not have the ability to be fertilized.

Related Terms

Examples of polar body in the following topics:

  • Oogenesis

    • 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.
    • When meiosis II has completed, an ootid and another polar body is created.
    • Both polar bodies disintegrate at the end of meiosis II, leaving only the ootid, which eventually develops into a mature ovum.
    • The formation of polar bodies serves to discard the extra haploid sets of chromosomes that have resulted as a consequence of meiosis.

  • Cholesterol Metabolism

    • One quarter of body cholesterol is produced by the liver, and 50% of this is reabsorbed back into the circulation via the small intestine.
    • However, as we now know that cholesterol is kept in balance in the body, and that food intake has little effect on blood cholesterol concentrations, it appears that eggs can be a healthy part of one's diet.
    • The body also compensates for any absorption of additional cholesterol by reducing cholesterol synthesis.
    • For these reasons, cholesterol intake in food has little, if any, effect on total body cholesterol content or concentrations of cholesterol in the blood.
    • Photo taken under polarized light.

  • Medical Imaging

    • Medical imaging is used to create images of the human body used for clinical purposes, diagnostic procedures or medical science.
    • A magnetic resonance imaging instrument (MRI), or "nuclear magnetic resonance (NMR) imaging" scanner as it was originally known, uses powerful magnets to polarize and excite hydrogen nuclei (single proton) in water molecules in human tissue, producing a detectable signal which is spatially encoded, resulting in images of the body scanner .
    • Images of activity distribution throughout the body can show rapidly growing tissue, like tumor, metastasis, or infection.
    • A magnetic resonance imaging instrument (MRI scanner), or "nuclear magnetic resonance (NMR) imaging" scanner as it was originally known, uses powerful magnets to polarize and excite hydrogen nuclei (single proton) in water molecules in human tissue, producing a detectable signal which is spatially encoded, resulting in images of the body.
    • The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body on a biologically active molecule.Three-dimensional images of tracer concentration within the body are then constructed by computer analysis.A PET scan is one of the many medical uses for radioactive isotopes

  • The Action Potential and Propagation

    • As additional sodium rushes in, the membrane potential actually reverses its polarity.  
    • During this change of polarity the membrane actually develops a positive value for a moment (+40 millivolts).

  • Water Content in the Body

    • In physiology, body water is the water content of the human body.
    • It makes up a significant percentage of total body composition.
    • The water in the body is distributed among various fluid compartments that are interspersed in the various cavities of the body through different tissue types.
    • Body water is regulated largely by the renal and neuro-endocrine systems.
    • There are many clinical methods to determine body water.

  • Body Planes and Sections

    • Body planes are hypothetical geometric planes used to divide the body into sections.
    • The sagittal plane (lateral or Y-Z plane) divides the body into sinister and dexter (left and right) sides.
    • It is typically a horizontal plane through the center of the body and is parallel to the ground.
    • Body planes are used to describe anatomical motion in the X-Y-Z coordinate system that the body moves through.
    • Anatomical change during embryological development is also described and measured with body planes.

  • Thalamus

    • The thalamus derives its blood supply from four arteries including the polar artery (posterior communicating artery), paramedian thalamic-subthalamic arteries, inferolateral (thalamogeniculate) arteries, and posterior (medial and lateral) choroidal arteries.
    • These are all derived from the vertebrobasilar arterial system except the polar artery.

  • Tissues in Levels of Organization

    • The human body is organized at several levels of scale that can each be examined.
    • The human body has many levels of structural organization.
    • Each tissue type has a characteristic role in the body:
    • Each organ is a specialized functional center responsible for a specific function of the body.
    • List the various levels of structural organization that make up the human body

  • Thermoregulation

    • If the body must cool down, the body vasodilates these blood vessels. 
    • This allows for our body to release a lot of body heat through radiation. 
    • The body also thermoregulates via the process of sweating (perspiration).
    • In addition, our body thermoregulates using our hair. 
    • Finally, while technically not a thermoregulatory mechanism, the fat associated with our skin does help insulate our body and therefore increases body temperature as a result.

  • Body Cavities

    • Vertebrates have fluid-filled spaces called body cavities that contain the organs.
    • By the broadest definition, a body cavity is any fluid-filled space in a multicellular organism.
    • "The human body cavity," normally refers to the ventral body cavity because it is by far the largest one in volume.
    • The dorsal cavity is a continuous cavity located on the dorsal side of the body.
    • This is the most narrow of all body cavities, sometimes described as threadlike.