The Journey of Sperm: How the Reproductive System Works

Sex hormones are a type of hormone that originates from our reproductive systems. They play a crucial role in the development and maintenance of our sexual characteristics and reproductive functions. For instance, the primary male sex hormone is testosterone. The hormone testosterone, produced in the testes, is responsible for many masculine traits. These include: Body hair

The female reproductive system consists of two ovoid-shaped ovaries attached to the dorsal body wall, just below the kidneys. The ovaries not only produce eggs but also play a role in the production of estrogen and progesterone. During a 20-week gestation period, it is believed that around six to seven million potential egg cells are present in a fetus. However, this number decreases to one to two million at birth. As a woman reaches puberty, the number of eggs further declines to 300,000 to 500,000. By the time of menopause, there are usually less than one thousand eggs left. Typically, only one egg is released each month. The ovaries take turns releasing an egg. These eggs undergo division through mitosis and then meiosis. Most of them remain arrested at prophase one for up to 50 years.

The egg is spherical with a diameter of about 110 to 120 micrometers. In comparison, the head of a human sperm, as discussed in the previous video, is only around 2.5 micrometers in diameter. Similar to the sperm, the egg also contains a large nucleus and a haploid set of chromosomes. It is surrounded by a plasma membrane and an outer membrane called the vitelline membrane.

Despite having the same main function, the male reproductive system has quite different parts compared to the female. To start with, there are two ovoid testes in male humans. The testes lie in a pair of sacks which are pouchlike extensions of their skin between the thighs. These are called the scrotal sacs. The development of the sperms requires a temperature around 1 to 8 degrees less than the body temperature, which is around 30 degrees Celsius. This is why the testes lie in the scrotal sacs outside the main body.

There is a spermatic cord that contains blood vessels at the upper end of each testes. Leading from the end of the testes is a narrow, much coiled tube called the epididymis. The testes produce sperms, which may then be stored in an inactive form in the epididymis before entering the vas deferens or sperm duct. The sperm duct from each site passes into the abdominal cavity, loops over the urethra of that site, and finally opens into the urethra. A gland called the seminal vesicle opens into each sperm duct at the base of the urinary bladder. Where the two sperm ducts join, their urethra is the prostate gland. Beneath the prostate gland is the bulbourethral gland. The seminal vesicle, the prostate, and the bulbourethral gland secrete a slippery fluid that mixes with the sperms called seminal fluid or semen. The semen is an important fluid because it contains nutrients and enzymes which serve to nourish and protect the sperms and activate them so that they begin to swim.

The human sperm or spermatozoon has a head with a diameter of only about 2.5 micrometers. To get a better understanding of how small this is, compare it with the diameter of your hair which is around 70 micrometers. You can fit 28 of these wiggly cells along the width of just a single hair. The sperm head contains a large nucleus that carries a haploid set of chromosomes, little cytoplasm, and an acrosome. The acrosome is a sac containing enzymes. The human sperm also includes a middle piece containing mitochondria to provide energy for the activity of the sperm and, of course, a tail or flagellum to enable the sperm to swim towards the egg. The enzymes can break down part of the egg's membranes to let the sperm penetrate during fertilization.

Puberty is the stage in the development of humans and other mammals when the sex organs mature and produce gametes for the first time. In humans, puberty takes place later in life compared to other mammals. Puberty begins at the age of about 12 years for boys. However, there has been a recent increase in hitting puberty at a younger age because of the artificial food given to our kids. Testosterone is the male sex hormone made by the testes that increases during puberty and is responsible for secondary sex characteristics.