Ovum (Egg Cell): Function, Anatomy, Ovulation and Reproductive Health
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer: What is an ovum?
An ovum is an egg cell, one of the reproductive cells involved in reproduction. The ovaries produce ova and release one mature ovum at ovulation. If sperm fertilizes it, it becomes a zygote and may develop into a blastocyst, embryo and fetus after implantation. If fertilization does not occur, the ovum breaks down and is reabsorbed by the body. [1]
What the research says
Advanced maternal age was associated with worse pregnancy outcomes in a meta-analysis of 18 studies. In the studies reporting these outcomes (14 for miscarriage, 9 for live birth), infertile women of advanced maternal age had significantly higher miscarriage rates and lower live birth rates than younger women, while lower implantation and clinical pregnancy rates did not reach statistical significance; the authors noted that a decline in oocyte quality plays a key role in reproductive problems in older women (Zhao et al., Aging, 2023). [2]
When young donor oocytes were used to minimize maternal-age effects, paternal age was not associated with embryo aneuploidy. A systematic review of 6 studies (2,637 IVF cycles; 20,024 embryos) and an individual patient data meta-analysis of three high-quality studies (10,830 day 5/6 embryos) found no significant effect of paternal age on aneuploidy (OR 0.97 per decade of age; 95% CI 0.91–1.03) (Dviri et al., Hum Reprod Update, 2021). [3]
What is an ovum?
An ovum is an egg cell. It is a reproductive cell, or gamete, produced by the ovaries. “Ovum” refers to one egg cell; “ova” refers to more than one. [1]
An ovum is not the same developmental stage as an embryo or fetus. It is a single reproductive cell that can combine with sperm. After fertilization, the combined cell develops through later stages.
Where is the ovum located?
The ovaries are two small glands on either side of the uterus. They store and produce ova and release hormones that help regulate menstruation and reproduction. [1]
During a menstrual cycle, the ovaries release one mature ovum at ovulation. The ovum’s release is part of the reproductive process, but release does not guarantee fertilization. [1]
What does an ovum do?
The ovum has several roles in reproduction and early development. It contributes genetic material, provides a setting for fertilization and supplies nutrients during the earliest stage of development.
Role of the ovum | What it means |
Contributes genetic material | The egg cell contains 23 chromosomes, or half of the genetic information needed to create a fetus; the other half comes from sperm. |
Matures for reproduction | Oogenesis is the cellular process through which an egg becomes mature and develops the parts needed to continue in reproduction. |
Participates in fertilization | Sperm and ovum genetic material combine to form a zygote. |
Helps prevent multiple-sperm entry | The ovum’s tough outer layer helps allow only one sperm cell to enter. |
Supports early development | Nutrients in the cytoplasm nourish the developing blastocyst until it can implant in the uterus. |
These roles describe the ovum’s biology. They do not predict whether fertilization will happen or whether a pregnancy will develop.
What happens after ovulation?
At ovulation, the ovary releases one mature ovum. If a sperm cell fertilizes the ovum, the fertilized cell becomes a zygote.
The zygote can later develop into a blastocyst. After implantation into the uterus, it develops into an embryo and later a fetus. This sequence describes stages of development rather than a guarantee that every released ovum will be fertilized or implanted.
If sperm does not fertilize the ovum, the ovum breaks down and is reabsorbed by the body.
What is the anatomy of an ovum in simple terms?
The ovum has four described parts. Each has a role in protecting the cell, supporting maturation or contributing to early development.
Ovum part | Main role |
Nucleus | The central core containing 23 chromosomes, or half of the genetic material involved in reproduction. |
Cytoplasm | A jelly-like substance around the nucleus that provides nutrients for egg development and early embryonic growth. |
Zona pellucida | A tough, transparent membrane that protects the ovum and helps prevent more than one sperm from entering. |
Corona radiata | The outermost layer of cells that nourishes the ovum and helps it interact with its environment. |
The ovum’s structure is specialized for a short but important role: maturing, participating in fertilization if it occurs and supporting the earliest development afterward.
What is oogenesis?
Oogenesis is the cellular process through which an egg becomes mature. Maturation involves several steps that help the egg develop the right parts and characteristics for the reproductive process.
Not every egg cell will mature or continue through every stage. The process is influenced by the biology of the ovaries and by factors that affect ovulation or egg health.
What factors can affect ova?
Ovum development, quality or release can be affected by ovulation disorders, age and other conditions and exposures, some of which are beyond a person's control. These factors do not all work in the same way, and some are beyond a person’s control.
Ovulation disorders
An ovulation disorder is a condition that affects ovulation. Examples named in the clinical material include polyendocrine metabolic ovarian syndrome (PMOS), hypothalamus disorders and primary ovarian insufficiency (POI).
A hormonal imbalance can disrupt ovulation and potentially affect egg quality. Problems involving the hypothalamus can disrupt signals needed for ovulation. With primary ovarian insufficiency, the ovaries stop working before age 40, resulting in fewer ova and a decline in their quality.
Age-related factors
A person is born with all the eggs they will ever have. As age increases, the quantity and quality of eggs naturally decline. This can affect how successful fertilization is and increase the possibility that an ovum has an irregularity involving its chromosomes.
Age is one factor among many. It does not determine an individual outcome by itself.
Environmental toxins
Exposure to heavy metals, pesticides and chemicals can affect the health of ova. If you are concerned that an environmental exposure may be affecting reproductive health, discuss the concern with a healthcare professional.
Genetic conditions
Some genetic conditions affect the process of ovulation. Certain chromosomal disorders can affect the ovum directly and influence how a fertilized egg develops.
Genetic conditions are not personal choices, and an educational article cannot determine whether one is present.
Other medical conditions
Autoimmune diseases and unmanaged chronic diseases can indirectly affect egg health. Poorly managed diabetes is one example of a chronic condition that can create an unhealthy environment for egg development and affect ovulation.
Managing a health condition should be individualized with a healthcare professional.
Can lifestyle support egg health?
Some health habits can support overall reproductive health, but they cannot control every factor that affects ova. Some diseases, genetic conditions and age-related changes are outside a person’s control.
General health habit | How it may support reproductive health |
Avoid smoking and tobacco products | Smoking can negatively affect several aspects of health, including egg health. |
Maintain a weight that is healthy for you | Being underweight or having obesity can disrupt hormones and affect ovulation; an appropriate weight is individual. |
Eat balanced meals | Fruits, vegetables, lean protein and whole grains support overall health; limiting excess sugar, unhealthy fats and processed foods may also help overall health. |
Manage chronic stress | Chronic stress can raise stress hormones that may affect ovulation and egg quality; relaxation practices and physical activity may help manage stress. |
Limit alcohol | Excessive alcohol consumption can negatively affect egg health. |
Take a prenatal vitamin when appropriate | During reproductive years, a prenatal vitamin may benefit overall health; ask a healthcare professional whether it is right for you. |
Stay physically active | Regular activity such as walking, swimming or yard work has broad health benefits. |
These steps are not a guarantee of fertility. They should be viewed as general health support rather than a promise that an egg will mature, fertilize or lead to pregnancy.
When might a clinician evaluate the ovaries or ova?
If someone has difficulty with menstruation or becoming pregnant, a healthcare professional may evaluate the ovaries and eggs to look for a possible explanation.
The evaluation depends on the person’s symptoms, health history and reproductive goals. An article cannot determine which tests or treatments are appropriate.
Consider arranging an appointment when menstrual patterns change, ovulation concerns persist or pregnancy has not occurred despite trying. A clinician can help distinguish a concern involving ovulation, the ovaries, the egg cell or another part of the reproductive system.
What questions should you ask about your ovum and ovulation?
Questions about the ovum to ask at an appointment include whether your cycle suggests an ovulation concern, whether an evaluation is needed and which changes should prompt follow-up.
Could my menstrual pattern suggest an ovulation concern?
How do my ovaries and ovulation relate to the symptoms I am noticing?
Could a medication, chronic condition or environmental exposure be relevant?
What general health habits are appropriate for my situation?
Do I need an evaluation of the ovaries, ovulation or fertility?
Should I discuss prenatal vitamins, alcohol, tobacco or physical activity?
Which changes should prompt follow-up?
What can an ovum not tell you about reproductive health?
A single egg cell cannot provide a complete picture of reproductive health. Egg quantity, egg quality, ovulation, sperm, the uterus, hormones and other health factors can all matter.
Likewise, lifestyle advice should not be used to blame a person for difficulty conceiving. Some conditions affecting ova are beyond a person’s control.
Conclusion: Understand the egg cell, and get support for concerns
An ovum is an egg cell produced and released by the ovaries. It contributes 23 chromosomes, participates in fertilization and provides nutrients for the earliest stage of development. Its four described parts—the nucleus, cytoplasm, zona pellucida and corona radiata—support these roles.
Ova can be affected by ovulation disorders, age-related changes, environmental toxins, genetic conditions and other medical conditions. General health habits may support reproductive health, but they cannot control every factor. Menstrual concerns or difficulty becoming pregnant are valid reasons to speak with a healthcare professional.
Frequently Asked Questions
Is an ovum the same as an egg?
Yes. Ovum is the medical term for an egg cell. Ova is the plural form.
Where are ova made?
The ovaries produce and store ova. The ovaries are two small glands on either side of the uterus.
How many eggs are released during ovulation?
One mature ovum is released at ovulation during each menstrual cycle.
What happens when sperm fertilizes an ovum?
The fertilized ovum becomes a zygote. The zygote can develop into a blastocyst, which may implant in the uterus and then develop into an embryo and later a fetus.
What happens if an ovum is not fertilized?
An unfertilized ovum breaks down and is reabsorbed by the body.
How many chromosomes are in an ovum?
The ovum contains 23 chromosomes, which is half of the genetic information involved in creating a fetus. The other half comes from sperm.
What is the zona pellucida?
The zona pellucida is a tough, transparent membrane surrounding the ovum. It protects the egg cell and helps prevent more than one sperm from entering during fertilization.
What is the corona radiata?
The corona radiata is the outermost layer of cells around the ovum. It nourishes the ovum and helps it interact with its environment.
What is oogenesis?
Oogenesis is the cellular process through which an egg becomes mature. It involves several steps that help the egg develop the parts needed for reproduction.
Does age affect ova?
The quantity and quality of eggs naturally decline with age. This can affect fertilization and increase the possibility of chromosomal irregularity in an ovum.
Can health conditions affect ovulation or egg health?
Yes. Ovulation disorders, genetic conditions, autoimmune diseases and unmanaged chronic diseases can affect ovulation or egg health. Environmental toxins such as heavy metals, pesticides and chemicals may also affect ova.
Can lifestyle habits guarantee healthy eggs?
No. Avoiding tobacco, eating balanced meals, staying active, managing stress, limiting alcohol and maintaining a weight that is healthy for you may support overall health, but many factors affecting ova are outside a person’s control.
When should I discuss ovum or fertility concerns with a healthcare professional?
Consider arranging an appointment for ongoing menstrual concerns, suspected ovulation problems or difficulty becoming pregnant. A clinician can help decide whether the ovaries, ovulation or another part of the reproductive system needs evaluation.
Related guides
References
Holesh JE, Bass AN, Lord M. Physiology, Ovulation. StatPearls. Treasure Island (FL): StatPearls Publishing. Last updated May 1, 2023. https://www.ncbi.nlm.nih.gov/books/NBK441996/
Zhao J, Huang B, Li N, et al. Relationship between advanced maternal age and decline of endometrial receptivity: a systematic review and meta-analysis. Aging (Albany NY). 2023;15(7):2460-2472. PMID 37036802. https://doi.org/10.18632/aging.204555
Dviri M, Madjunkova S, Koziarz A, et al. Is there an association between paternal age and aneuploidy? Evidence from young donor oocyte-derived embryos: a systematic review and individual patient data meta-analysis. Hum Reprod Update. 2021;27(3):486-500. PMID 33355342. https://doi.org/10.1093/humupd/dmaa052
Disclaimer
This article is for general educational purposes and is not a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified healthcare professional with any questions about a medical condition or treatment.
This article does not diagnose infertility or an ovulation disorder, predict pregnancy, recommend fertility treatment or assess genetic risk. Please do not use this information to blame yourself or anyone else for difficulty conceiving.
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