The ovary is a primary gonad of the female reproductive system. It produces the female reproductive cells called the ovum (non-motile). The ovum is fertilised by a motile sperm to form a zygote. Also, the ovaries act as an endocrine gland by releasing certain hormones in females. Here, let’s discuss the anatomy of an ovary with a well-labelled diagram.
Table of Contents
Ovary Anatomy
Ovaries are flat oval structures that measure approximately 4 cm in length, 1 cm in thickness and 2 cm in breadth. Females have two ovaries. They are present on the left and right sides of the uterus in a portion termed the ovarian fossa. The side close to the fallopian tube is connected via a suspensory ligament called the infundibulopelvic ligament. The other side connects to the uterus through ovarian ligaments. Each ovary is connected to the broad ligament of the uterus at the hilum (depression) through the mesovarium and ovarian ligament.
Each ovary is divided into two parts:
1. The medulla
2. The cortex
Medulla
The medulla, also known as the zona vasculosa, is the deeper core region of the ovary. It has a stroma made up of loose connective tissues. Near the hilum, it comprises blood arteries, lymphatics, nerve fibres, and bundles of smooth muscle fibres.
Cortex
The cortex is the wider outer section with dense cellular layers. It is broken at the hilum, where the medulla joins the mesovarium. The germinal epithelium lines the cortex beneath a fibrous layer known as tunica albuginea.
The cortex is made up of the following structures:
- Glandular structures that indicate various phases of ovarian follicles
- Cells of connective tissue
- Interstitial cells are clusters of epithelial cells with tiny lipid granules that are generated mostly from theca interna of ovarian follicles.
Ovarian Follicles
The outer cortex comprises germinal epithelium that is formed from the germinal ridges. The germinal epithelium gives birth to a number of primordial eggs. The primordial eggs migrate to the cortex’s inner substance. The ova or egg cell is surrounded by a layer of spindle cells termed granulosa cells from the ovarian stroma. The primordial egg cells and granulosa cells together form the primordial follicles. These primordial follicles develop into tertiary vesicular follicles with a characteristic fluid-filled cavity called the antrum. The final fully mature follicle that ruptures to release the ovum is termed the Graafian follicle.
The ovary has around 6 million primordial follicles by the seventh or eighth month of intrauterine development. However, at birth, only 1 million primordial follicles are visible in both ovaries, and the remainder of the follicles degenerate. During adolescence, the number drops to around 300,000 to 400,000. Also during each menstrual cycle, one of the follicles grows and discharges its ovum. Throughout each menstrual cycle, only one egg is released from each of the ovaries. Many follicles degenerate with each cycle.
After the release of the mature ovum, the remains of the ovarian follicles are termed corpus luteum. This corpus luteum regresses to form a remnant termed corpus Albicans.
Labelled Diagram of Ovary
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Functions of Ovary
Some of the functions of the ovary are as follows:
- Secretion of female sex hormones like progesterone and estrogen. It also secretes other hormones like relaxin, inhibin and small quantities of androgens.
- Oogenesis (female gametogenesis) happens in the ovary. It is a process through which the ovum is formed.
- It governs the menstruation process by which the unfertilised ovum is shed.
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