The Reproductive System A Practical Guide

The Reproductive System Gonads – primary sex organs Male: testes Female: ovaries Gonads produce gametes and secrete hormones Male gametes: sperm Female gametes: eggs (ova) Functions: Male: produce sperm and testosterone Female: produce eggs, estrogen and progesterone; nurture the developing embryo; and deliver the newborn baby.

Male Reproductive System External genitalia: Penis Scrotum (house testes) Accessory organs: Seminal vesicles Prostate Bulbourethral gland Duct system: Epididymis Vas deferens Urethra

Male Reproductive System

Testes Testes make sperm via meiosis Produce testosterone – male characteristics Epididymis – collects mature sperm (mature for 20 days) and eventually propel them through the vas deferens Vas deferens – tube where sperm travel to the outside of body (peristalsis) Urethra – urine and sperm leave through

Vasectomy Vasectomy - the vas deferens is cut to prevent sperm leaving (and fertilizing an egg)

Accessory Organs Seminal vesicles – produce 60% of semen Nourish sperm with fructose, Vitamin C Prostate – secrete milky fluid to activate sperm Bulbourethral gland – secretes thick, clear mucus Acts as lubricant Protects sperm vs. acidic environment found in urethra and vagina

External male genitalia Scrotum – maintains testes at 3°C lower than body Penis – deliver sperm Shaft Erectile tissue fills with blood Glans penis – enlarged tip Prepuce – foreskin

Sperm Production of sperm begins at puberty and continues throughout life in the testes During ejaculation, 2 to 5 ml of semen are released in which there are between 50-150 million sperm per ml. Infertility results when there are less than 20 million per ml.

Female Reproductive System Mammaries Ovaries Duct System Fallopian tubes Uterus Vagina External genitalia

Female Mammary Glands Figure 16.13a

Female Mammary Glands Figure 16.13b

Mammograms Figure 16.14

Female Internal Genitalia Ovaries B: Fallopian tubes – receive oocyte and provide place for fertilization C: Uterus – receives, retain, and nourishes egg D: Cervix – Bottom of uterus E: Vagina – thin walled tube Birth canal – passageway for delivery of baby and menstrual flow Receives penis during copulation Female Internal Genitalia

Female External Genitalia Labia – skin folds Clitoris – contains erectile tissue Female correspondent to penis Greater vestibular gland (i.e. Bartholin’s Gland) – secretes lubricant

Ovaries Where eggs are produced through meiosis Each ovary takes turns releasing one egg per month (twins = two eggs released) Secrete progesterone and estrogen Estrogen – secondary sex characteristics in females Progesterone – regulates menstruation

Ovaries Consist of developing follicles Each follicle has: Oocyte (developing egg) Follicular cells (surround egg) Ovulation – when egg is mature the follicle ruptures releasing egg and follicle becomes corpus luteum

Oocyte Developing

Oogenesis Total supply of eggs are present at birth Ability to release eggs from puberty  menopause FSH causes some primary follicles to mature into oocytes every month LH causes development of secondary follicle If sperm penetrates oocyte then ovum is produced

Fertilization Sperm must travel to the egg and penetrate to combine the DNA from both parents -- this creates the first cell after fertilization: the Zygote 23 chromosomes from each parent; zygote has a total of 46 chromosomes

Fertilization normally occurs in the Fallopian Tubes Secondary oocyte Ovulation Uterus Endometrium Uterine tube Blastocyst cavity Inner cell mass Trophoblast Zygote (fertilized egg) Early cleavage 4-cell stage Early blastocyst Late blastocyst (implanting) Morula Ovary (a) (b) (d) (e) (c) The fertilized egg (zygote) implants in the uterus

Ova An egg is usually a few days old before it implants in the uterus.  At this point, it has already divided several times and is called a bastula.

Female Cycles *Interesting fact – humans are one of the few animals that do not have some kind of visible obvious display of fertility. Evolutionary biologists suggest this trait evolved as a way to keep males interested for more than just the fertile period, increasing the likelihood of male parental care of offspring.

Fluctuation of Gonadotropin Levels Figure 16.12a

Fluctuation of Ovarian Hormone Levels Figure 16.12b

Ovarian Cycle Figure 16.12c

Uterine (Menstrual) Cycle Figure 16.12d

How does a woman know she is pregnant? Missed period Changes in body, tenderness in breasts, nausea…etc Pregnancy test – tests urine for hormone levels (hCG – human chorionic gonadotropin) which is produced by the blastocyst 6-12 days after fertilization

Clearblue Pregnancy Test

Embryo of Approximately 18 Days Figure 16.16

Fetal Development

Fetal Development

The 7-week Embryo Figure 16.17

Photographs of a Developing Fetus Figure 16.18a

Development of the Human Fetus Table 16.1 (1 of 2)

Development of the Human Fetus Table 16.1 (2 of 2)

Initiation of Labor Figure 16.19, step 1 Baby moves deeper into mother’s birth canal Figure 16.19, step 1

Initiation of Labor Figure 16.19, step 2 Pressoreceptors in cervix of uterus excited Baby moves deeper into mother’s birth canal Figure 16.19, step 2

Initiation of Labor Figure 16.19, step 3 Afferent impulses to hypothalamus Pressoreceptors in cervix of uterus excited Baby moves deeper into mother’s birth canal Figure 16.19, step 3

Initiation of Labor Figure 16.19, step 4 Hypothalamus sends efferent impulses to posterior pituitary, where oxytocin is stored Afferent impulses to hypothalamus Pressoreceptors in cervix of uterus excited Baby moves deeper into mother’s birth canal Figure 16.19, step 4

Initiation of Labor Figure 16.19, step 5 Hypothalamus sends efferent impulses to posterior pituitary, where oxytocin is stored Posterior pituitary releases oxytocin to blood; oxytocin targets mother’s uterine muscle Afferent impulses to hypothalamus Pressoreceptors in cervix of uterus excited Baby moves deeper into mother’s birth canal Figure 16.19, step 5

Initiation of Labor Figure 16.19, step 6 Hypothalamus sends efferent impulses to posterior pituitary, where oxytocin is stored Posterior pituitary releases oxytocin to blood; oxytocin targets mother’s uterine muscle Uterus responds by contracting more vigorously Afferent impulses to hypothalamus Pressoreceptors in cervix of uterus excited Baby moves deeper into mother’s birth canal Positive feedback mechanism continues to cycle until interrupted by birth of baby Figure 16.19, step 6

Stages of Labor Figure 16.20 (1 of 3)

Stages of Labor Figure 16.20 (2 of 3)

Stages of Labor Figure 16.20 (3 of 3)

Temporary methods of birth control What if you don’t want to have a baby? There are lots of options…… Temporary methods of birth control Condom Birth control pills Nuva-ring Depo-Provera (shot) IUD (semi-permanent) Diaphragm

More Permanent Options… Vasectomy Tubal Ligation

What about the morning after pill - also known as Plan B? Plan B must be taken within 72 hours of unprotected sex, it prevents the egg from releasing or the sperm from fertilizing the egg. It may also prevent implantation of a fertilized egg. Plan B does NOT work on women who are already pregnant. It can be bought from pharmacies, though some states have age restrictions.

What about abortion? Regardless of your political views on the subject, abortion is legal in the U.S. Most procedures must be done early and involve removing the fetus from the uterus.

Juno Preview