Menstruation is the body’s physical process of shedding the inner layer of the uterus when pregnancy has not occurred. During this time, the body releases a mixture of blood, tissue, and fluids, which can contain various components that people sometimes mistake for the egg. The reality is that the reproductive cell released by the ovary is far too small and fragile to be seen within the flow.
The Microscopic Truth About the Unfertilized Egg
The human ovum, or egg cell, is recognized as one of the largest single cells in the human body. Despite this distinction, its size remains microscopic, measuring approximately 0.1 to 0.12 millimeters in diameter. The unfertilized egg is roughly the width of a single strand of human hair. This minute size means that it is completely invisible to the naked eye within the menstrual fluid.
The egg is released from the ovary during ovulation, which typically occurs about 14 days before the start of the next period. If the ovum is not fertilized, its lifespan is extremely short, lasting only 12 to 24 hours.
After this brief window, the unfertilized egg rapidly begins to disintegrate through a process called lysis. The cellular remnants are then naturally reabsorbed by the body long before the menstrual bleeding phase even begins. Therefore, by the time the uterine lining is shed, the egg has already dissolved and been cleared from the reproductive tract.
What You Are Actually Seeing During Menstruation
Since the egg dissolves long before the menstrual bleed, the visible pieces in the flow are components of the uterine lining and clotted blood. Menstrual fluid is a complex mixture primarily composed of blood, mucus from the cervix and vagina, and endometrial tissue. The appearance of this material can change significantly throughout the cycle, leading to confusion about its contents.
Blood Clots
One of the most common materials mistaken for the egg is a blood clot, which appears as a jelly-like, dark red mass. These clots form when the rate of bleeding is heavy and the body’s natural anticoagulants are overwhelmed. The blood begins to solidify before it can pass out of the body, creating varying sized clumps of material.
Endometrial Tissue
In addition to blood clots, pieces of actual endometrial tissue are shed. This tissue is the inner lining of the uterus and can sometimes appear as small, pale, or grayish fragments within the darker red blood. These pieces can be stringy, ragged, or thin, and their passage can be more noticeable on days of heavier flow.
The Biological Purpose of Shedding the Uterine Lining
The reason for the presence of blood and tissue is the cyclical preparation of the uterus for potential pregnancy. Following the end of the previous period, the uterine lining, known as the endometrium, begins to thicken dramatically. This growth is driven by rising levels of the hormone estrogen and is designed to create a soft, nutrient-rich environment for a fertilized egg to implant.
After ovulation, the hormone progesterone takes over, further preparing the endometrium by increasing its blood supply. This process continues for about two weeks while the body waits to see if fertilization has occurred.
If the egg is not fertilized, the corpus luteum—the temporary structure in the ovary that produces progesterone—begins to break down. This causes a sharp drop in the levels of both estrogen and progesterone in the bloodstream. This sudden withdrawal of hormonal support signals the body to begin dismantling the prepared uterine lining.
The shedding of this prepared tissue and blood is the menstrual period itself. The resulting flow is simply the material that the body no longer needs, as the lack of a fertilized egg means the pregnancy preparation was unnecessary for that month.