The Reproductive System

Male and Female Reproductive Systems Are functionally different Female produces 1 gamete per month: retains and nurtures zygote Male disseminates large quantities of gametes: produces 1/2 billion sperm per day

Functions To ensure survival of the species produce egg and sperm cells transport & sustain these cells nurture the developing offspring produce hormones

The Male Reproductive System

Pathway of Sperm Testes or male gonads: secrete male sex hormones (androgens) testosterone produce male gametes (spermatozoa or sperm) contribute X and Y chromosomes

Pathway of Sperm Epididymis superior to each testis tubular (5-6cm) takes ~2 weeks for sperm to mature/ travel through

Pathway of Sperm Vas deferens: tubes transport sperm from testes to the ejaculatory ducts where a vasectomy occurs

Pathway of Sperm Ejaculatory duct Urethra passes urine & semen out entrance way for STDs

Accessory Organs Secrete fluids into ejaculatory duct & urethra Seminal vesicles secrete alkaline fluid containing fructose, vitamin C, and coagulating enzymes Prostate gland produces milky white fluid which activates sperm Bulbourethral gland thick clear ejaculate fluid which neutralizes traces of acidic urine in the urethra

External Genitalia Scrotum: Penis: surrounds testes scrotal skin lengthens and shrinks to maintain optimal temperature Penis: erectile organ

Sperm

Spermatogenesis

Testosterone Stimulates spermatogenesis Affects CNS functions libido & related behaviors Stimulates metabolism blood cell formation, muscle growth

Testosterone Establishes male secondary sex characteristics: distribution of facial hair increased muscle mass and body size characteristic adipose tissue deposits Maintains accessory glands and organs of male reproductive tract

Female Reproductive System

Functions Produces sex hormones and functional gametes Protects and supports developing embryo Nourishes newborn infant

Female Organs Ovaries or female gonads: release 1 immature gamete (oocyte) per month produces estrogen & progesterone

Female Organs Ovum (egg): female reproductive cell contributes X chromosome

Female Organs Fallopian tubes: carry oocytes to uterus

Female Organs Uterus: Cervix: “womb” encloses and supports developing embryo lining is shed when no fertilized egg is present Cervix: lower end of the uterus

Female Organs Vagina: connects uterus with exterior pathway for menstrual flow, birth canal, sperm, & STDs

Mammary Glands Modified sweat glands Ducts and glands do not complete development unless pregnancy occurs

Estrogen Stimulates bone and muscle growth Maintains female secondary sex characteristics: body hair distribution adipose tissue deposits

Estrogen Affects central nervous system (CNS) activity (especially in the hypothalamus, where estrogens increase the sexual drive) Maintains functional accessory reproductive glands and organs Initiates repair and growth of endometrium

Oogenesis Begins before birth Accelerates during puberty Ceases at menopause

Aging - Females Menopause ovulation and menstruation cease ~ ages 45-55 levels of estrogen & progesterone decline reduction in uterus & breast size reduction in bone deposits (osteoporosis)

Aging - Males Andropause aka male climacteric occurs over a gradual period of time testosterone declines ~ age 50-60 sperm production continues

Fertilization May occur when: Location: Process: sperm are present a few days after ovulation Location: fallopian tube Process: head of sperm enters ovum nuclei fuse zygote is formed

Fertilization Cleavage: Implantation: initial division of the zygote continues as the zygote moves towards the uterus the zygote becomes a blastocyte (hollow ball of cells) Implantation: ~ 6 days after fertilization blastocyte burrows into the lining of the uterus

Early Zygote Development

Pregnancy 9 month gestation period Divided into trimesters 3-month periods First 8 weeks of pregnancy: developing human is called an embryo

Pregnancy First Trimester: supportive membranes rapid growth amnion closes & protects the embryo chorion forms the placenta structure through which the mother nourishes the embryo

Structure of the Placenta

Pregnancy First Trimester: Development of Embryo 4th week: 2nd month: major organs are formed heart begins to beat 2nd month: arms and legs take shape major internal organs are evident

Embryo Development

Pregnancy First Trimester: Development of Fetus After 1st trimester: from 8th week - delivery After 1st trimester: sex can be distinguished recognizable body features organ systems have begun to form

Pregnancy Second and Third Trimesters: 3rd trimester: ~9 months: fetus grows rapidly organs become functional 3rd trimester: fetus can exist outside the mother’s body ~9 months: fetus leaves the mother’s body in a process called labor usually lasts several hours

Events of Human Fetal Development

Pregnancy During childbirth, the fetus exits the mother’s body through the vagina.