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増殖期
増殖期は一般的に月経後に起こり、標準的な 28 日周期で 6 日から 13 日間続きます。この段階では、発育中の卵胞によって生成されるエストロゲンによって誘導される子宮内膜の再構築が行われます。
特に、子宮腺の基底部を含む子宮内膜の基底層は月経の影響を受けません。この層の幹細胞は有糸分裂を起こし、機…
増殖期は、子宮月経周期の第2段階です。月経後に始まり、典型的な28日周期で約6〜13日間続きます。
この段階では、子宮子宮内膜は、卵巣で成長している卵胞によって放出されるエストロゲンの影響下でそれ自体を再構築します。
子宮内膜の基底層は、子宮腺の基底部分を含む、層基底部として知られており、月経後も無傷で生存します。
基底層の細胞は急速に分裂し、新しい層機能層が形成されます。
子宮内膜が肥厚するにつれて、子宮内膜腺が発達し、細動脈が渦巻いて伸び、新たに形成された機能層を貫通します。
その結果、子宮内膜はビロードのようになり、厚くなり、血管新生が進み、厚さは約2倍の約4〜10 mmになります。
その間、卵巣での出来事は、優勢な卵胞がグラフィアン卵胞に成熟する結果をもたらします。
その結果、増殖期は、下垂体前葉から放出される黄体形成ホルモンレベルの急増によって引き起こされる排卵で終了します。
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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.