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Fase proliferativa
La fase proliferativa ocurre típicamente después de la menstruación y dura entre 6 y 13 días en un ciclo estándar de 28 días. Esta fase implica la rec…
La fase proliferativa es la segunda fase del ciclo menstrual uterino. Comienza después de la menstruación y dura aproximadamente de 6 a 13 días en un ciclo típico de 28 días.
Durante esta fase, el endometrio uterino se reconstruye bajo la influencia del estrógeno liberado por los folículos en crecimiento en los ovarios.
La capa basal del endometrio, conocida como estrato basal, que incluye las partes basales de las glándulas uterinas, sobrevive intacta a la menstruación.
Las células del estrato basal se dividen rápidamente, creando una nueva capa de estrato funcional.
A medida que el endometrio se engrosa, se desarrollan las glándulas endometriales y las arteriolas se enrollan y alargan, penetrando en el estrato funcional recién formado.
Como resultado, el endometrio se vuelve aterciopelado, grueso y bien vascularizado, duplicando aproximadamente su grosor a unos 4-10 mm.
Mientras tanto, los eventos en los ovarios dan como resultado la maduración del folículo dominante en un folículo de Graaf.
Como resultado, la fase proliferativa concluye con la ovulación, desencadenada por un aumento en los niveles de hormona luteinizante liberada por la glándula pituitaria anterior.
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Q1: When does the proliferative phase occur in the menstrual cycle?
The proliferative phase begins after menstruation and lasts approximately 6 to 13 days in a typical 28-day cycle. This phase follows the menses phase and precedes ovulation. During this time, the uterine endometrium undergoes reconstruction under the influence of estrogen released by growing ovarian follicles.
Q2: What role does the stratum basale play during the proliferative phase?
The stratum basale, the basal layer of the endometrium, survives menstruation intact and serves as the source for endometrial regeneration. Stem cells within this layer undergo rapid mitosis, creating a new stratum functionalis layer. This regenerative capacity allows the endometrium to rebuild completely during the proliferative phase.
Q3: How does the endometrium change during the proliferative phase?
During the proliferative phase, the endometrium thickens from approximately 2 mm to 4–10 mm, roughly doubling in thickness. Endometrial glands develop and become more numerous, while arterioles coil and lengthen to penetrate the newly formed stratum functionalis. These vascular changes enhance blood supply, giving the endometrium a velvety, thick, and well-vascularized appearance.
Q4: What hormonal changes trigger the end of the proliferative phase?
The proliferative phase concludes with ovulation, which is triggered by a surge in luteinizing hormone released by the anterior pituitary gland. This hormonal surge causes the dominant follicle to mature into a Graafian follicle and rupture, releasing the oocyte. The luteinizing hormone surge marks the transition from the proliferative phase to the secretory phase.
Q5: Why is estrogen essential during the proliferative phase?
Estrogen, released by growing follicles in the ovaries, drives endometrial reconstruction during the proliferative phase. It stimulates stem cells in the stratum basale to divide rapidly and promotes the development of endometrial glands and blood vessels. Without adequate estrogen, the endometrium cannot rebuild properly to prepare for potential implantation.
Q6: What is the relationship between follicle development and the proliferative phase?
Follicle maturation in the ovaries occurs simultaneously with endometrial reconstruction during the proliferative phase. Growing follicles produce estrogen, which stimulates endometrial thickening and gland development. The phase culminates when the dominant follicle matures into a Graafian follicle, triggering ovulation and ending the proliferative phase.
Q7: How does vascularization of the endometrium support the proliferative phase?
Arterioles coil and lengthen during the proliferative phase, penetrating the newly formed stratum functionalis to enhance blood supply to the endometrium. This increased vascularization delivers oxygen and nutrients necessary for gland development and tissue thickening. The well-vascularized endometrium becomes prepared to support potential embryo implantation.