The Reproductive System

Chapter 8.11

Introduction

• Reproduction occurs in all species.– Tiny 1 celled organisms divide or separate by

themselves to reproduce.– Most animals require male and female

reproduction– The Male and Female Reproduction Systems

have several parts in common:• Gonads (endocrine glands)• Tubes• Exocrine glands

Gonads

• Males– These are called testes

• They produce sperm

• Females– These are called ovaries

• They produce the ova (egg)

Male• Gonads are found outside the body in a sac called the

Scrotum.• Testes produce sperm and the male hormone

testosterone.• The Penis is the primary sex organ and it lies anterior to

the testes.• The epididymis is a 20 foot long tube that is coiled inside

the scrotal sac. Sperm are stored here until they are mature and able to move by themselves

• As the epididymis extends upward it becomes the vas deferens. This is known as the spermatic cord. It extends through the abdominal wall and curves over and behind the bladder.

• Seminal Vesicles are outpouchings at the end of the vas deferens. They produce a thick yellow secretion that adds to the volume of semen and nourishes the sperm.

• Prostate Gland produces a secretion that maintains the mobility of sperm.

• The ejaculatory duct carries sperm through the prostate gland to the urethra.

• The urethra is a small passage for urine and sperm and leads to the outside of the body.

Effects of Testosterone

• at puberty testosterone prompts spermatogenesis

• causes reproductive organs to grow & assume adult functions

• as adult normal levels of testosterone are required to maintain normal structure & function of reproductive organ

Spermatogenesis

• sequence of events in seminiferous tubules of testes that leads to production of male gametes or sperm

• healthy male produces several hundred million sperm per day

Female Reproduction System

Main function is to house a developing fetus

• Female Gonads…the are small ovaries oval shaped structures that produce the female sex cell…the ova and the hormone estrogen.

• Approximately every 28 days an ovum matures and is forced from the ovary and received by the Fallopian Tube.

• Fallopian Tubes are muscular tubes about 5 inches in length.

• They do NOT connect to the ovaries…when the ovum is forced out, it floats around till the Fimbriae “finger like projections” create a current and sweep it into the tube.

• The ovum lives in the fallopian tube for about 5 days and is then deposited into the uterus.

Uterus

• size & shape of pear

• hollow, thick-walled organ that functions to receive, retain, & nourish a fertilized egg and developing baby

• The uterus is attached to the fallopian tubes.

• While the ovum is in the Fallopian tube the uterus begins to build an interlining called the endometrium. If the ovum is not fertilized it deteriorates and does not implant into the wall of the uterus.

• If nothing implants, the endometrium deteriorates causing bleeding or Menstruation.

• The Vagina is a muscular tube that houses the neck of the uterus called the cervix. – It extends approximately 3 inches to the

outside of the body– It is known as the birth canal.

Oogenesis

• process in which eggs are produced

• supply of eggs that female releases is determined by the time of birth

• from puberty to about 50

• one ovulation each month

• Only 400 - 500 oocytes of potential 700,000 are released during lifetime

Fertilization of the egg

• Occurs in the Fallopian Tube.• A sperm with 23 chromosomes and an egg with

23 chromosomes fuse to form a Zygote with 46 complete chromosomes.

• If the ovum is fertilized it will implant into the endometrial wall.– The woman will not experience a period while she is

pregnant. – The ovaries will not release another ovum while there

is an implanted ovum in the wall. Cannot get pregnant again

– The endometrium serves as nourishment for the developing fetus.

Fertilization

• The long journey to fertilization must be completed within 12 to 48 hours, before the sperm die. They must first cross the barrier of the cervix, which will be thin and watery if the woman has just ovulated (for our purposes, we will assume that sexual intercourse has occurred within a couple of hours after ovulation). Once the sperm have traversed the cervical mucus, they travel up the moist lining of the uterus into the Fallopian tubes (only one of the Fallopian tubes contains an egg, so many sperm travel in the wrong direction). Fewer than 1,000 sperm out of the millions in the semen actually reach the Fallopian tubes.

Contraception and STDs• As you can see from the process of sexual reproduction, there are

several ways to prevent the sperm and egg from coming together. These methods of contraception fall into the following categories: – Not engaging in sexual activity - abstinence – Preventing a follicle from developing - birth control pills – Placing a barrier between sperm and egg - condoms

(male/female), cervical caps, diaphragms – Killing the sperm - spermicides – Surgery - blocking the sperm or egg with surgical

procedures like tubal ligations (in women) or vasectomies (in men)

– Timing - avoiding intercourse during the period of maximum fertility NOT EFFECTIVE!!!!

• Sexual activity carries certain risks of diseases caused by: – Bacteria (gonorrhea, syphilis, chlamydia) – Protozoa (trichomoniasis) – Viruses (genital herpes, HIV/AIDS, HPV)