Human Reproduction – The Basics

MATURITY REQUIRED

Reproductive Anatomy of the Human Male.The mammalian male reproductive system

includes the external genitalia and the internal reproductive organs The scrotum and the penis are the external

components of the reproductive system. The internal reproductive organs consist of the gonads (testes) that produce gametes (sperm

cells) and hormones accessory sex glands that secrete products

essential to sperm movement A set of ducts that carry the sperm and glandular

secretion.

Male Reproductive Structures

Testosterone: the male reproductive hormone made by the testicles which causes the changes of puberty.

Penis: the organ of transfer of sperm to female.

Scrotum: pouch-like sac holding both testicles in a separate compartment that hang underneath the penis.

Testicles – Testes Gland: two glands in the male, located in the scrotum, which produce male hormones (testosterone) and sperm.

External Male Reproductive

Sperm: the microscopic cells produced by the male’s testicles which can fertilize the female’s ovum.

Prostate Gland: a man’s gland that helps make semen.

Cowper’s Glands: behind the base of the penis which secretes fluid to make semen and neutralize acid.

Ejaculatory duct: a short straight tube that passes into the prostate gland and opens into the urethra.

Internal Male Reproductive System

The scrotum is a fold of the body wall which aids the reproductive process in different ways:

Testes develop in the abdomen and descend into the scrotum just before birth. This is important since sperms can not develop at normal body temperature.

By having the testes hanging outside the abdominal cavity in the scrotum, the temperature is 2° C lower and sperm production can occur

In many rodents, the testes are drawn back into the abdominal cavity, and sperm maturation is interrupted between breeding seasons.

Some mammals whose body temperature is low enough to allow sperm maturation, such as monotremes, whales and elephants retain the testes within the abdominal cavity permanently.

Scrotum

Swimming for Your LifeA sperm is a tiny package with a big responsibility – to

fertilize the egg and create a human life. So that tiny package is loaded with “gear” for its important journey.

A few facts: Daily sperm production by a healthy man:

10 million to 50 million Contents of average ejaculation:

50 million sperm; 25 million moving; 20 million deformed Maturation: 72 days Average swimming speed of a sperm:

8 inches per hour Survival time in a woman: 2 to 7 days

External structures consist of two sets of labia surrounding the vaginal opening.

Internal reproductive structures consist of a pair of gonads (ovaries) and a system of ducts and chambers.- The role of the ducts and chambers are gamete movement and embryo development.

Female Reproductive Structures

Fig. 46.9

Ovaries are the female gonads. Located in the abdominal cavity and enclosed in a tough

protective capsule.. Attached by mesentery to, the uterus. Each ovary contains follicles.

During ovulation, the egg is expelled from the follicle. After ovulation the remaining follicular

tissue develops into the corpus luteum. Secretes estrogens and progesterone. Maintain the uterine

lining during pregnancy. If the egg is not fertilized (pregnancy does not

occur) the corpus luteumdegenerates and a new

follicle matures during the next cycle.

Once the sperm enter the female’s body, they travel through the vaginal canal towards the fallopian tubes.

The egg is then fertilized in the fallopian tube. Once fertilization occurs, the zygote travels through the fallopian tube and into the uterus.

Sometimes, the embryo implants inside the fallopian tube instead of the uterus. This is called an “ectopic” pregnancy, and is very dangerous for both mother and child.

Fertilization

The egg is only viable while inside the fallopian tube. If it is not fertilized by that point, it dies and is shed along with the uterine lining during menstruation.

Fertilization