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 areejaculated out through the penis during sexualintercourse.

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

SpermatozoaSpermatozoa, also known as sperm, is the malegamete (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 reachan egg and fertilize it.

Semen

When sperm is released from the body, it is mixedwith 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

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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

Internal Anatomy:

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 (sexcell).

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 itwhile in the fallopian tubes.

During sexual intercourse,millions of sperm are releasedand all compete to get to thepotential ova first.