As mentioned above, mastoiditis most often develops as a result of a middle ear infection. Bacteria from the middle ear can travel into the air cells of the mastoid bone. In addition, a type of skin cyst in the middle ear, called a cholesteatoma, may block drainage of the ear, leading to mastoiditis. Mastoiditis symptoms may include: Fever, irritability, and lethargy.
LINK / CITE ADD TO WORD LIST. noun. The definition of a streak is a flash of light or a long thin line that stand out in color or texture from its surroundings. An example of a streak is a strip of red in otherwise blonde hair.
The primitive streak is a structure that forms in the blastula during the early stages of avian, reptilian and mammalian embryonic development.The presence of the primitive streak will establish bilateral symmetry, determine the site of gastrulation and initiate germ layer formation.he formation of the primitive streak in the blastocyst involves the coordinated movement and re-arrangement of cells in the epiblast. Even before the streak is visible, epiblast cells have started to move. Two counter-rotating flows of cells meet at the posterior end, where the streak forms.