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Female dogs bleed during estrus, which usually lasts from 7–13 days, depending on the size and maturity of the dog. Ovulation occurs 24–48 hours after the luteinizing hormone peak, which occurs around the fourth day of estrus; therefore, this is the best time to begin breeding.
In physal pinching, a constriction occurs at the aboral (physal) end of the anemone and the fragment then "pinches" off, at which point the fragment regenerates to form a fully functional adult polyp. During polarity reversal, oral structures form at the aboral end of the anemone resulting in an animal with two oral ends.
Once homeostasis is restored, the blood pressure and ATP production regulates. Vasoconstriction also occurs in superficial blood vessels of warm-blooded animals when their ambient environment is cold; this process diverts the flow of heated blood to the center of the animal, preventing the loss of heat. [citation needed]
Constriction is a method used by several snake species to kill or subdue their prey. Although some species of venomous and mildly venomous snakes do use constriction to subdue their prey, most snakes which use constriction lack venom. [ 1 ]
In the invagination that occurs in ascidian gastrulation, cells first undergo apical constriction and then change their shape to become rounder ––and thus shorter along the apical-basal axis––which is responsible for the completion of the invagination movement. [17] During cell division, cells also naturally take on a rounded morphology.
A sphincter is a circular muscle that normally maintains constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning. Sphincters are found in many animals.
Apical constriction mechanisms (red: filamentous actin. orange: myosin.) Apical constriction occurs primarily through the contraction of cytoskeletal elements. The specific mechanism depends on the species, the cell type, and the morphogenetic movement. Model organisms that have been studied include the frog Xenopus, and the fly Drosophila.
In pupillary constriction induced by pilocarpine, not only is the sphincter nerve supply activated but that of the dilator is inhibited. The reverse is true, so control of pupil size is controlled by differences in contraction intensity of each muscle. Another term for the constriction of the pupil is miosis. Substances that cause miosis are ...