CorpusHuman Anatomy

Female Reproductive Organs

Coronal section, anterior view — the journey of the oocyte

The uterus, uterine tubes, ovaries, cervix and upper vagina seen from the front. The uterus is cut in the coronal plane to show its three layers — endometrium, myometrium and perimetrium — around the triangular uterine cavity, continuous below with the cervical canal. The patient's left side (on the right of the picture) is also sectioned: the uterine tube is opened to show its intramural part, isthmus, ampulla and infundibulum with fimbriae, and the ovary shows follicles at successive stages, a recently ruptured follicle, a corpus luteum and a corpus albicans. The patient's right side shows the external surfaces and the broad, round, ovarian and suspensory ligaments.

The animation follows the ovulated oocyte as the fimbriae capture it, sperm ascend to meet it in the ampulla, and the resulting zygote, morula and blastocyst travel to the uterus to implant in the endometrium (numbered markers 1–6). Use the guided walkthrough to step through the journey.

Step-by-step

  1. 1 · Follicles mature in the ovary

    The ovarian cortex holds follicles at every stage: primordial (flat granulosa cells around a primary oocyte arrested in prophase I) → primary (cuboidal granulosa, zona pellucida) → secondary (multilayered granulosa, theca) → antral (fluid-filled antrum, FSH-dependent). Each cycle one becomes the dominant Graafian follicle (≈18–25 mm), whose estradiol triggers the LH surge.

  2. 2 · Ovulation

    The LH surge makes the oocyte complete meiosis I (first polar body) and arrest in metaphase II, expands the cumulus and digests the follicle wall at the stigma. About 24–36 h after the surge begins, the secondary oocyte with its zona pellucida and corona radiata is released onto the ovarian surface (marker 1).

  3. 3 · Capture by the fimbriae

    At ovulation the fimbriae of the infundibulum sweep over the ovary; ciliated cells and the adhesive cumulus draw the oocyte through the abdominal ostium. Because the tube opens into the peritoneal cavity, ascending infection (PID) can reach the pelvis — and a captured embryo can rarely implant ectopically on the ovary or peritoneum.

  4. 4 · Fertilisation in the ampulla

    Capacitated sperm (animated, ascending from the cervix) meet the oocyte in the wide, mucosa-folded ampulla, usually within 24 h of ovulation. One sperm penetrates the corona and zona; the cortical reaction blocks polyspermy and the oocyte completes meiosis II — forming the zygote (marker 2). The ampulla is also the commonest site of ectopic pregnancy.

  5. 5 · Cleavage during tubal transport

    Cilia and peristalsis carry the embryo through the narrow, muscular isthmus while it cleaves inside the zona: 2 cells at ≈30 h (marker 3), a 16-cell morula by day 3–4 (marker 4). Damaged cilia or scarring delay transport and predispose to tubal ectopic pregnancy.

  6. 6 · Blastocyst in the uterine cavity

    The morula passes through the intramural part of the tube into the uterine cavity at about day 4, becomes a blastocyst (inner cell mass + trophoblast around a fluid cavity) and hatches from the zona pellucida on day 5–6 (marker 5), nourished by uterine gland secretions.

  7. 7 · Implantation into the endometrium

    From ≈day 6–7 the blastocyst attaches by its embryonic pole to the progesterone-primed secretory endometrium, usually in the upper posterior wall of the body (marker 6). The syncytiotrophoblast invades the stroma and starts secreting hCG; implantation is complete by ≈day 10–12, and the stroma undergoes the decidual reaction.

  8. 8 · Corpus luteum sustains the pregnancy

    After ovulation the follicle wall becomes the corpus luteum, secreting progesterone that keeps the endometrium secretory. hCG from the implanting embryo rescues it until the placenta takes over at ≈7–9 weeks; without pregnancy it regresses after ≈14 days into a white scar, the corpus albicans, and menstruation follows.

  9. Anatomy · Layers of the uterine wall

    The endometrium (mucosa: functional layer shed at menstruation, basal layer that regenerates it), the thick smooth-muscle myometrium that contracts in labour, and the serosal perimetrium (visceral peritoneum). Below the isthmus the wall becomes the mainly fibrous cervix, with its canal running from the internal to the external os into the vagina.

  10. Anatomy · Ligaments

    The broad ligament is a peritoneal sheet draping the uterus, tubes and ovaries. The suspensory ligament of the ovary carries the ovarian vessels from the pelvic brim; the ovarian ligament ties the ovary to the uterus; the round ligament runs from the uterotubal junction through the inguinal canal to the labium majus. The ovarian and round ligaments are remnants of the gubernaculum.

Labelled parts