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Testis (plural: testes or testicles) is the organ in male mammals that generates sperm, the male reproductive cell and androgens, the male hormone. Testes are a pair of oval-shaped structures in the male reproductive system. They can be found in the scrotal sac, right behind the penis and in front of the anus.
The ovary is the female reproductive organ responsible for producing sex cells (eggs or ova) . Female vertebrates’ ovaries, usually paired, produce both sex cells and hormones required for reproduction. The ovaries’ production is linked to the seasons in some invertebrate taxa, such as coelenterates (cnidarians).
Normal and Microscopic Anatomy of Testis
Each human testis weighs about 25 grams (0.875 ounces) and measures 4 to 5 cm (1.6 to 2.0 inches) in length and 2 to 3 cm (0.8 to 1.2 inches) in width. Each testis is encased in a fibrous capsule called the tunica albuginea. It is divided into 200 to 400 wedge-shaped parts, or lobes, by partitions of fibrous tissue from the tunica albuginea.
Three to ten coiled tubules, known as seminiferous tubules, are found in each lobe and create sperm cells. The mediastinum testis is formed when partitions between the lobes and the seminiferous tubules converge in one location near the anal side of each testis.
The testes contain germ cells that develop into mature spermatozoa, Sertoli cells that provide support, and Leydig (interstitial) cells that produce testosterone. From the embryonic yolk sac, germ cells travel to the foetal testes.
The Sertoli cells, which are found between the germinal epithelial cells within the seminiferous tubules, are similar to the ovary’s granulosa cells. The Leydig cells, found under the tunica albuginea, located in the septal walls and between the tubules, are similar to the hormone-secreting interstitial cells in the ovary.
Leydig cells are irregularly shaped and may contain several nuclei. Fat droplets, pigment granules, and crystalline structures are frequently seen in Leydig cells, which vary in number and appearance among animal species. Numerous blood and lymphatic veins, as well as nerve fibres, surround them.
The presence or lack of genes on the Y chromosome determines whether the primordial, indifferent gonad develops in the testes or the ovaries throughout embryonic development. During the first trimester of pregnancy, testosterone and its substantial derivative, dihydrotestosterone, play important roles in constructing male genitalia in the foetus but not in the actual formation of the testes.
During the seventh month of pregnancy, the testes develop in the abdominal cavity and descend into the scrotum, where androgens stimulate them. About 2% of males have an undescended testis at birth, but this problem usually resolves after three months.
Human chorionic gonadotropin is a hormone released by the placenta which stimulates testosterone production in the unborn testes. During early childhood, testosterone secretion stops, and the cells within the testes remain immature; during adolescence, gonadotropic hormones released by the pituitary gland at the base of the brain drive tissue development, and the testes develop the ability to produce sperm and androgens.
Anatomy of the Ovary
The ovaries’ primary purpose is to nourish and prepare oocytes (eggs) for ovulation (the mature egg is ruptured and released from the ovary). After being released, an egg travels through the fallopian tube to the uterus.
An egg can be pierced and fertilised by sperm in the fallopian tube. If an egg is fertilised, it will implant in the uterus wall. The production and secretion of hormones by cells in the ovaries influence ovulation and fertilisation significantly.
These hormones are also crucial for female sexual development and to keep a pregnancy going. In humans, they also help control the menstrual cycle (periodic shedding of the uterine lining).
The ovaries of infants and young girls are a mass of elongated tissue in the pelvic girdle that gradually enlarges and changes shape as the female reaches adolescence. Adult ovaries are almond-shaped, with a frequently uneven and scarred surface.
The two ovaries are around 4 cm (1.6 inches) long, 2 cm (0.8 inches) broad, and 1.5 cm (0.6 inches) thick, and weigh 4 to 8 grams (0.14–0.3 ounces). Several ligaments (bands of fibrous connective tissue) hold the ovaries in place, including the wide ligament, suspensory ligament, and ovarian ligament. The follicles, oocytes, and some interstitial cells are found in the outer cortex, whereas the inner medulla contains additional interstitial cells, fibrous tissue, blood vessels, lymphatic ducts, and nerves.
Follicular Development
Follicles are hollow balls of cells that contain immature eggs and are present in the ovaries at birth. About 150,000 to 500,000 follicles are present at that time. The number of immature follicles reduces to around 34,000 by the start of a woman’s reproductive life and continues to fall.
The number of follicles in a woman’s body decreases with age until, at menopause, the few remaining follicles degenerate. Only 300 to 400 follicles mature throughout the active reproductive years, typically between 13 and 50.
Conclusion
In animals, the testis is the organ that produces sperm, the male reproductive cell, and androgens, the male hormones. The ovary is the female reproductive organ that generates sex cells in zoology (eggs or ova). The ovaries of female vertebrates, which are usually paired, produce both sex cells and reproductive hormones.
