A Graafian follicle is the fully mature ovarian follicle in Anatomy and Physiology II. It contains the secondary oocyte and ruptures at ovulation to release the egg.
A Graafian follicle is the mature ovarian follicle that is ready to ovulate in Anatomy and Physiology II. It is the last stage of follicle development before the oocyte is released from the ovary.
By the time a follicle reaches this stage, it has developed a large fluid-filled antrum and contains a secondary oocyte surrounded by supporting follicle cells. You will usually see it described as a tertiary follicle or mature follicle, and at ovulation it is often about 18 to 25 mm across. That size matters because it shows the follicle has completed the growth and hormonal changes needed for release.
The Graafian follicle does more than just hold the egg. Its granulosa and thecal cells produce estrogen, which rises during the follicular phase and helps build up the uterine lining. In other words, the follicle and the uterus are being coordinated at the same time, so the body is preparing for a possible pregnancy before the egg is even released.
Ovulation happens when the follicle ruptures and the secondary oocyte is released into the uterine tube. This is the moment that makes fertilization possible. If sperm is not present, the oocyte will not be fertilized, and the follicle tissue changes after ovulation instead of staying in its mature form.
A common confusion is thinking the Graafian follicle is the egg itself. It is not. The follicle is the structure in the ovary that houses and supports the oocyte, while the oocyte is the actual cell that can be fertilized. After release, what remains in the ovary becomes the corpus luteum, which shifts hormone production toward progesterone.
The Graafian follicle is the bridge between oogenesis and the ovarian cycle, so it connects what is happening inside the ovary to what is happening in the uterus. If you can trace this one structure, you can explain why estrogen rises, when ovulation happens, and how the body knows when to move from the follicular phase to the luteal phase.
It also helps you separate the different parts of the reproductive cycle. The follicle is not just a container for the egg. It is an active endocrine structure that responds to pituitary hormones, grows, matures, and then changes again after ovulation.
In A&P II, this term often shows up in diagrams, cycle charts, and hormone-feedback questions. If you can identify the mature follicle on a visual or explain what happens to it after ovulation, you are already using the term the way the course expects.
Keep studying Anatomy and Physiology II Unit 11
Visual cheatsheet
view galleryFollicular Phase
The Graafian follicle is the end point of the follicular phase. During this phase, follicles grow under hormonal stimulation and one becomes dominant. Estrogen from the maturing follicle rises as the phase continues, which helps prepare the uterine lining and sets up the timing for ovulation.
Ovulation
Ovulation is the event that happens when the Graafian follicle ruptures and releases the secondary oocyte. If you are tracking the ovarian cycle, the mature follicle is the structure right before this release. A lab image or cycle diagram often shows the follicle just before rupture and the oocyte leaving the ovary.
Corpus Luteum
After ovulation, the emptied Graafian follicle does not stay the same. Its remaining tissue transforms into the corpus luteum. That shift changes hormone production from mainly estrogen to mostly progesterone, which is why the follicle and corpus luteum are often taught as back-to-back stages.
Luteinizing Hormone
A surge in luteinizing hormone triggers ovulation from the mature Graafian follicle. Without that hormonal signal, the follicle does not rupture at the right time. This makes LH the main link between pituitary control and what the ovary actually does during the cycle.
A quiz question might ask you to label a mature follicle on an ovary diagram, match it to the follicular phase, or explain what structure releases the oocyte. You may also be asked to trace what happens after ovulation, which means identifying the same follicle as the tissue that becomes the corpus luteum. In hormone-based questions, look for the follicle as the source of rising estrogen before the LH surge. In short-answer responses, use the term to connect structure, hormone production, and the timing of ovulation instead of describing it as just an egg sac.
These two are easy to mix up because they happen back-to-back in the ovarian cycle. The Graafian follicle is the mature follicle before ovulation, while the corpus luteum is what forms from the leftover follicle tissue after the oocyte is released. One prepares for ovulation, the other takes over hormone production afterward.
A Graafian follicle is the mature ovarian follicle that contains the secondary oocyte right before ovulation.
It has a large fluid-filled antrum and is usually about 18 to 25 mm wide when it is ready to release the egg.
The follicle produces estrogen, which helps coordinate the ovarian cycle with changes in the uterine lining.
Ovulation happens when the Graafian follicle ruptures and releases the oocyte into the uterine tube.
After ovulation, the remaining follicle tissue becomes the corpus luteum instead of staying a mature follicle.
A Graafian follicle is the fully mature ovarian follicle that contains a secondary oocyte and is ready to ovulate. In A&P II, it is the final follicle stage before the egg is released from the ovary. It also secretes estrogen during the follicular phase.
No. The Graafian follicle is the structure in the ovary that surrounds and supports the oocyte. The egg itself is the oocyte inside it. This distinction matters because many diagram questions ask you to identify the follicle, not the cell it contains.
After ovulation, the follicle does not stay in its mature form. The remaining tissue turns into the corpus luteum, which changes its hormone output. If pregnancy does not happen, the corpus luteum later regresses.
Look for the large follicle with a big antrum, usually near the surface of the ovary, and often shown with a secondary oocyte inside. If the picture shows a mature follicle just before rupture, that is the Graafian follicle. After rupture, the structure is no longer labeled that way.