Structure and function of human reproductive structures Human Reproduction Structure and function of human reproductive structures

Sexual reproduction terms Gametes--specialized reproductive cells Ova (eggs)--female gamete Sperm--male gametes Zygote--formed from fusion of gametes’ nuclei (fertilization)--fertilization and birth brainpop animation Result: offspring have genetic information from 2 parents Brainpop intro to reproduction

Female Reproductive anatomy Ovaries(2)--produce eggs (ova pl., ovum sing.) produce sex hormones At birth, female has all the eggs she will ever have (approximately 2 million) At puberty (sexual maturity), ~400 eggs will mature Each month, one ovary releases an egg into oviduct (fallopian tubes)--long tube that leads to the uterus Fertilization normally takes place in oviduct

Female anatomy •Uterus--muscular pear-shaped organ into which the egg travels (even in not fertilized) If egg is fertilized, implants in wall of uterus-->pregnancy If not fertilized, egg disintegrates within 24 hours after ovulation Cervix--narrow portion at the bottom of uterus--provides opening to uterus from vagina Vagina--muscular tube connects uterus to outside of body Birth canal through which infants pass when born

Male reproductive anatomy Testes(2)--found in the scrotum (pouch of skin) outside of body--keeps testes away from heat of body Produce sperm in males at puberty (~13 years old) in seminiferous tubules Produce sex hormones Sperm require ~74 days to develop; millions mature each day. Many needed because few will survive / reach egg Sperm contains: Head--contains genetic material (DNA) Midsection--has mitochondria for energy production Tail--motility (movement) for travelling to egg

Male reproductive anatomy Epididymis--long, coiled duct that stores sperm until ejaculation, which moves sperm out of the body Vas deferens(2)--tubes that rapidly transport sperm from epididymis out of body

Male reproductive anatomy Penis--male organ of sexual intercourse and urine excretion Urethra--tube through which sperm (and urine) move out of the body Semen--thick, white fluid that carries sperm contains secretions seminal vesicles (2)--fructose for sperm nourishment prostate gland--basic solution to neutralize acidic environment of vagina Cowper’s (bulbourethral) gland--provides lubricant; also helps to clean urethra During ejaculation, ~5 mL of semen released with ~300 million sperm cells

Sexual intercourse Penis becomes rigid with arousal due to increased blood flow Vagina becomes lubricated with arousal Ejaculation caused by involuntary muscle contractions Sperm-containing semen released into vagina Sperm travel toward oviduct, although only thousands survive the ~1 hour trip Fertilization--sperm release enzymes that change the outer layer of egg so sperm can enter Once one sperm enters, cell membrane of egg changes so no more sperm can enter--How do you get twins? (animation) Zygote (fertilized egg) travels to uterus for implantation and is nourished by blood flow from mother during pregnancy

QUIZ--Hormones and Menstrual Cycle 1. Specifically, what body system deals with/controls hormones. 2. Name 3 organs in the human body that produce/control hormones 3. Name one of the sex hormones mentioned in the reading (other than estrogen, progesterone, and testosterone)

Hormones and their control Endocrine system regulates hormones (chemical messengers) Sexual development and secondary sex characteristics Males--deeper voice, facial hair, etc.; Females--widening hips, breast development Effect is slow and long-lasting Nervous system--response is quick and short Feedback control of hormones One hormone often stimulates organ, while another inhibits it Negative feedback--product of process stops process Positive feedback--product of process accelerated process Insulin and glucagon from pancreas control blood sugar

Sites of hormonal control Anterior pituitary (endocrine gland in brain)produces: 1. Luteinizing hormone (LH) 2. Follicle stimulating hormone (FSH) Hypothalamus (in brain) Regulates release of FSH and LH by acting on the pituitary Controls blood pressure, body temp., emotions Makes ADH and oxytocin

Hormones in males FSH stimulates maturation of the testes and sperm LH stimulates release of testosterone (male sex hormone) from the testes Testosterone stimulates: Sperm production, erection, and ejaculation Secondary sex characteristics

Hormones in females Menstrual cycle-- ~monthly cycle that releases egg (ovum) Ovulation--release of an egg (ovum) Estrogen and progesterone--major female sex hormones 1. Produced by the ovaries 2. Stimulate sexual maturity 3. Regulate menstrual cycle (in part)

Menstrual cycle Approximately 28 days Ovulation (release of egg at about day 14) Sperm survive ~72 hours; egg survives ~24 hours-->Fertilization can occur within about a four-day window If egg is not fertilized: 1. Hormone levels drop 2. Decreased blood flow to lining of uterus 3. Part of the lining of uterus disintegrates and passes to outside of body (menstruation) loss of 50 mL to 150 mL of blood Lasts 3 to 7 days

Specific menstrual hormones FSH--causes maturation of egg inside a sac (follicle) on the surface of ovary Estrogen--secreted by the developing follicle 1. Stimulates secretion of LH (stimulates ovulation and the production of estrogen) 2. Stimulates thickening of inner lining of uterus Progesterone--maintains thickness of lining of uterus and promotes pregnancy (implantation of fertilized egg) Corpus luteum formed after ovulation--releases estrogen and progesterone which together inhibit LH and maintain thick uterine lining

Menopause Profound hormonal changes in women Signals end reproductive phase of life Occurs ~45 - 50 years old