Human Reproduction

The Male Reproductive System

1. Penis - tube-like organ that hangs outside the body - come in all sizes and shapes, determined by our genes - during sexual intercourse, the spongy cells that surround the urethra fill with blood, and the penis becomes firm and erect

2. Testicles - also known as testes - usually two, one hangs lower - where sperm are made - also produces testosterone (male sex hormone that regulates sperm production)

3. Scrotum - bag of skin that holds testicles - keeps them at right temperature to make sperm, slightly cooler than body’s temperature - with age, gets bigger and baggier and turns a darker colour

4. Epididymis - attached to testicles, inside scrotum - stores the large numbers of sperm until they are ejaculated out through the penis during sexual intercourse.

5. Urethra - the tube through which urine and semen leaves the boy’s body (only 1 is released at a time) the prostate gland enlarges to block off any urine from the bladder during sexual intercourse

6. Vas Deferens - transports sperm from the testes to urethra

Sperm flow out of the body through this pathway: Testicles Epididymis Vas Deferens Urethra

Spermatozoa Spermatozoa, also known as sperm, is the male gamete (sex cell). Sperm look like tadpoles They are very small (the head is 5 µm by 3 µm, and the tail is 50 µm long) Very fragile… needs to be kept at a good temperature, must stay hydrated and cannot be exposed to a very acidic environment After puberty you make 200,000 - 400,000 sperm cells a day for the rest of your life For reproduction to happen, the sperm needs reach an egg and fertilize it.

Semen When sperm is released from the body, it is mixed with semen. Semen is a fluid. It has 2 major functions: - to protect the sperm from dehydration and the acidic environment of the female vagina - allows the sperm to swim more easily Semen is produced by 3 glands found in the male reproductive system: Seminal Vesicles Prostate Gland Cowper’s Gland

The Female Reproductive System

Internal Anatomy: 1. Vagina - passageway joining outside and uterus - an elastic & muscular organ that expands during birth to allow for the passage of the baby - place where the penis is inserted during sexual intercourse

2. Cervix - the opening between the vagina and the uterus - sperm enters this opening during sex - makes mucus to keep sperm alive - during pregnancy, a mucous plug forms across the cervix separating the uterus from the outside to prevent infection of the unborn baby - when giving birth, the cervix dilates (expands) to allow the baby to pass through

3. Uterus - also known as the womb - strong muscular and elastic organ where an unborn baby develops normally the size of a pear, grows to the size of a watermelon when pregnant - after an egg is released from the ovary, a blood-filled lining develops on the walls of the uterus in preparation for the unborn baby if no fertilization of the egg occurs, then this lining passes out through the vagina over several days as ‘periods’ or menstruation if there is fertilization, it is where the developing baby, called a fetus, grows and is fed

4. Fallopian Tubes - narrow tubes between the uterus and the ovary - place where conception or fertilization of an egg by a sperm occurs

5. Ovaries - there are 2 ovaries (1 at the end of each Fallopian Tube) - it is the gland that makes egg cells (ova) and female sex hormones (estrogen & progesterone)

Eggs exit the body through this pathway: Ovary Fallopian Tube Uterus Cervix Vagina

Ovum Ovum, also known as egg, is the female gamete (sex cell). Girls are born with hundreds of thousands of tiny ova. These egg cells are only half formed (immature) at puberty, hormones tell the ovaries it is time to start releasing eggs usually only one egg at a time matures (develops) and is released from an ovary eggs stop being released once menopause hits (at approx. 45 to 55 years old)

Fertilization For the ovum to be fertilized, a sperm must enter it while in the fallopian tubes. During sexual intercourse, millions of sperm are released and all compete to get to the potential ova first.