Uterus

The uterus is a hollow, muscular organ located in the pelvis of the female reproductive system.

It is crucial for reproduction and plays several key roles in the menstrual cycle, pregnancy, and childbirth. The uterus is also known as the womb and is shaped somewhat like an inverted pear.

The uterus is a key organ in the female reproductive system, responsible for menstruation, pregnancy and childbirth. Its presence is linked to the biological and evolutionary aspects of human reproduction, making it unique to women.

The uterus consists of three main parts:

• Fundus – the upper, rounded part of the uterus
• Body (corpus) – the main, central portion of the uterus where a fertilised egg implants and grows
• Cervix – the lower, narrow part that connects the uterus to the vagina. It serves as a passageway for menstrual blood and childbirth

How the uterus works

Menstrual cycle

• Endometrial lining – the interior of the uterus is lined with a layer called the endometrium. During the menstrual cycle, the endometrium thickens to prepare for a potential pregnancy. If fertilisation does not occur, the lining sheds and exits the body through menstruation
• Menstrual flow – menstruation, or the monthly period, involves the shedding of the endometrial lining through the vagina. This cycle is regulated by hormonal changes involving oestrogen and progesterone

Pregnancy

• Implantation – if a sperm fertilises an egg, the resulting embryo travels to the uterus and implants into the thickened endometrial lining
• Gestation – the uterus supports and nourishes the developing embryo throughout pregnancy. It expands significantly to accommodate the growing fetus and provides a protective environment for fetal development
• Childbirth – during labor, the uterus contracts rhythmically to help push the baby through the birth canal (cervix and vagina) and into the outside world

Hormonal regulation

• Menstrual and pregnancy hormones – the uterus responds to various hormones like oestrogen and progesterone. These hormones regulate the menstrual cycle, prepare the uterus for potential pregnancy, and support the maintenance of pregnancy

Why only women have a uterus

The uterus is specific to the female reproductive system and is part of the complex biological structure necessary for human reproduction.

Here’s why only women have a uterus:

Reproductive anatomy

• Sexual differentiation – during foetal development, individuals with XX chromosomes develop female reproductive structures, including the uterus. Those with XY chromosomes develop male reproductive structures, such as the testes and penis. This differentiation is guided by the presence or absence of specific sex-determining genes and hormones

Role in reproduction

• Pregnancy and childbirth – the uterus is essential for pregnancy as it provides a suitable environment for the fertilised egg to implant and grow. It also plays a crucial role in childbirth by contracting to expel the foetus during delivery. Men do not have a uterus because they do not need this organ for their reproductive role

Hormonal influence

• Sex hormones – female hormones such as oestrogen and progesterone regulate the development and function of the uterus. Men have different hormonal profiles and reproductive needs, which do not involve the uterus

References

• Anatomy, abdomen and pelvis: uterus. National Institutes of Health, USA. Accessed 15 July 2024
• Definition of uterus – NCI dictionary of cancer terms. National Cancer Institute, USA. Accessed 15 July 2024
• Physiology, uterus. National Institutes of Health, USA. Accessed 15 July 2024
• Uterus: anatomy, function, size, position & conditions. Cleveland Clinic, USA. Accessed 15 July 2024
• Uterus: MedlinePlus medical encyclopedia image. MedlinePlus, USA. Accessed 15 July 2024

Last reviewed and updated: 15 July 2024