Human Reproductive System Quiz

Reproductive System Overview

• Gonads are the primary sex organs
• Testes are the male gonads
• Ovaries are the female gonads
• Gonads produce gametes (sex cells) and secrete hormones
• Sperm are male gametes
• Ova (eggs) are female gametes

Male Reproductive System

• Testes: The primary male reproductive organs

• Duct system: Includes the epididymis, ductus (vas) deferens, and urethra

  • Epididymis: A comma-shaped, tightly coiled tube located on the superior aspect of the testis. It functions in sperm maturation and storage. Sperm are expelled to the vas deferens by muscular contractions.
  • Ductus (vas) deferens: Carries sperm from the epididymis to the ejaculatory duct; passes through the inguinal canal and over the bladder. Sperm movement is accomplished by peristalsis. The spermatic cord contains the ductus deferens, blood vessels, and nerves.
  • Ejaculatory duct: Formed by the union of the vas deferens and seminal vesicle; carries sperm into the urethra
  • Urethra: Extends from the bladder to the tip of the penis; carries both urine and sperm. Has three regions: prostatic, membranous, and spongy (penile).

• Accessory organs:

  • Seminal vesicles: Located at the base of the bladder; produces a thick, yellowish secretion (60% of semen), which contains fructose (sugar), vitamin C, prostaglandins, and other substances that nourish and activate sperm.
  • Prostate: Encircles the upper part of the urethra; secretes a milky fluid that helps activate sperm. It enters the urethra through several small ducts. Inflammation of the prostate is known as prostatitis; prostate cancer is the third most common cancer in males.
  • Bulbourethral glands (Cowper's glands): Pea-sized glands inferior to the prostate; produce a thick, clear mucus that cleanses the urethra of acidic urine prior to ejaculation and acts as a lubricant during sexual intercourse.

• External genitalia:

  • Scrotum: A divided sac of skin outside the abdominal cavity; maintains testes at 3°C lower than normal body temperature to protect sperm viability.
  • Penis: Delivers sperm into the female reproductive tract. The penis has a shaft and glans (enlarged tip). The prepuce (foreskin) covers the glans in some males.

Semen

• Mixture of sperm and accessory gland secretions
• Contains fructose for sperm energy
• Its alkalinity neutralizes the acidic environment of the vagina
• Inhibits bacterial multiplication
• Enhances sperm motility

Testosterone Production

• Most important hormone of the testes
• Produced in interstitial cells
• During puberty, luteinizing hormone (LH) activates the interstitial cells to produce testosterone.
• Functions of testosterone: Stimulates reproductive organ development, underlies sex drive, causes secondary sex characteristics (deepening of voice, increased hair growth, enlargement of skeletal muscles, thickening of bones)
• Testosterone production is regulated by a feedback loop involving the hypothalamus and pituitary gland

Spermatogenesis

• Sperm cell production
• Begins at puberty
• Occurs in the seminiferous tubules within the testes
• Spermatogonia (stem cells) divide rapidly to produce more stem cells before puberty. FSH modifies spermatogonia division. One resulting daughter cell is A (a stem cell), and the other becomes a primary spermatocyte, type B.
• Primary spermatocytes undergo meiosis, producing four haploid spermatids (each with 23 chromosomes).
• Spermatids mature into sperm cells through spermiogenesis.

Ovarian Follicle Stages

• Ovaries contain ovarian follicles. (sac-like structures)
• Primary follicle, contains an immature oocyte
• Graafian or vesicular follicle: growing follicle with a maturing oocyte
• Ovulation: egg matures, follicle ruptures; occurs about every 28 days
• Ruptured follicle transforms into the corpus luteum

Oogenesis

• Production of female gametes (ova)
• Supply of eggs present at birth
• Ability to release eggs begins at puberty
• Oogonia are female stem cells in a developing fetus
• The production of primary oocytes is achieved by mitosis of oogonia
• Primary oocytes are inactive until puberty; FSH causes maturation of some follicles each month; creates cyclic monthly changes known as the ovarian cycle
• Meiosis I begins in a primary oocyte during the follicular phase of the ovarian cycle .
• Meiosis II is completed only if the sperm penetrates the secondary oocyte. The secondary oocyte transforms into an ovum and the sperm’s genetic material combines to form a zygote

Female Reproductive System

• Ovaries: The primary female reproductive organs, responsible for producing ova and hormones.

• Duct system: Includes uterine tubes (fallopian tubes), uterus, and vagina

  • Uterine tubes (fallopian tubes): Receive the ovulated oocyte; provide a site for fertilization; little or no contact between ovaries and uterine tubes; supported by the broad ligament
  • Uterus: Hollow, pear-shaped organ; receives fertilized egg; retains fertilized egg; nourishes it; has three layers: endometrium (inner), myometrium (middle muscle), and perimetrium
  • Vagina: Extends from the cervix to the exterior of the body; acts as a birth canal; receives the penis during intercourse; hymen partially closes the vagina until it ruptures

• External genitalia (vulva): Includes:

  • Mons pubis: fatty area above the pubic symphysis, covered with pubic hair
  • Labia majora: hair-covered skin folds that enclose labia minora and the vestibule
  • Labia minora: delicate, hair-free folds of skin
  • Vestibule: enclosed by the labia majora; contains the external openings of the urethra and vagina
  • Clitoris: sensitive erectile tissue, homologous to the male penis; hooded by a prepuce
  • Greater vestibular glands: located on each side of the vagina; secrete lubricant during intercourse
  • Perineum: diamond-shaped region between the anterior ends of the labia, anus posteriorly, and ischial tuberosities laterally

Uterine (Menstrual) Cycle

• Cyclic changes in the endometrium
• Regulated by cyclic production of estrogens and progesterone
• FSH and LH regulate the production of estrogens and progesterone
• 28 days in length
• Ovulation typically occurs around day 14, usually in the middle of the cycle
• Stages of the cycle:
• Menstrual phase (days 1-5): functional layer of the endometrium is sloughed off, bleeding occurs
• Proliferative phase (days 6-14): Functional layer of the endometrium regenerates, estrogen levels rise, and ovulation happens
• Secretory phase (days 15-28): Progesterone rises and increases blood supply to endometrium; endometrium increases in size and readies for implantation. After fertilization, a hormone called hCG will cause the corpus luteum to continue making its hormones If fertilization does not occur, this hormone drops, and the corpus luteum degenerates.

Mammary Glands

• Modified sweat glands in females
• Function: produce milk
• Stimulated by sex hormones (mostly estrogens) to increase in size
• Anatomy:
• Areola: central pigmented area
• Nipple: protruding central area of areola
• Lobes: internal structures radiating around the nipple.
• Lobules: within lobes; contain alveolar glands
• Alveolar glands: produce milk during lactation
• Lactiferous ducts: connect alveolar glands to the nipple; lead to the nipple

Mammography

• X-ray examination that detects breast cancers too small to feel; recommended every 2 years for women between 40 and 49 years old, and yearly thereafter

Pregnancy and Development

• Pregnancy: period from conception until birth

• Conceptus: developing offspring

• Embryo: period from fertilization to week 8

• Fetus: period from week 9 until birth

• Gestation period: from date of last period until birth (approximately 280 days)

• Accomplishing Fertilization: for fertilization to occur, intercourse must happen within 2 days of ovulation at the uterine tube

• Mechanisms of Fertilization: Enzymes in sperm break down corona radiata; acrosomal reaction occurs and enzymes digest holes in the oocyte membrane; membrane receptors on oocyte pull sperm head into contact; second meiotic division occurs to form the ovum; genetic material of sperm and oocyte combines to form a zygote.

• Zygote: first cell of a new individual, formed by the union of sperm and egg DNA. Rapid mitotic cell divisions begin; moves from the uterine tube toward the uterus.

• Cleavage: rapid mitotic divisions that result in the blastocyst. The zygote divides 24 hours after fertilization; floats freely in the uterus for 2-3 days; implants in the endometrium around day 7 after ovulation, as part of the late blastocyst stage

• Events of Embryonic and Fetal Development: begins with the zygote (fertilized egg), forming into the 4-cell, morula (16-cell solid ball of blastomeres), and blastocyst (hollow ball of blastomeres); trophoblast cells surround the blastocyst, and the inner cell mass develops inside the cavity. Implantation typically occurs around day 7 and the primary germ layers are formed

• Development After Implantation: chorionic villi develop to form the placenta, a structure that supplies nutrients and oxygen to the developing embryo or fetus. The fluid filled amniotic sac surrounds the embryo and its umbilical cord.

• Functions of the placenta: Forms a barrier between mother and embryo; delivers nutrients and oxygen; removes waste from embryonic blood; becomes an endocrine organ by producing estrogen and progesterone to maintain pregnancy.

The Fetus (Beginning of Ninth Week)

• In the 8th week, all organ systems have formed
• Activities of the fetus are growth and organ specialization
• The appearance and the fetus changes tremendously.

Effects of Pregnancy on the Mother

• Anatomical changes: enlargement of the uterus, accentuated lumbar curvature (lordosis), relaxation of pelvic ligaments/pubic symphysis.
• Physiological changes: Gastrointestinal (morning sickness, heartburn, constipation); Urinary (increased urine production, stress incontinence); Respiratory (nasal congestion/swelling, increased vital capacity and respiratory rate); Cardiovascular (increased blood volume, blood pressure/pulse increase, varicose veins)

Childbirth (Parturition)

• Labor: series of events that expel infant from uterus
  • Stages of Labor:
• Dilation: cervix dilates; uterine contractions begin and increase, cervix softens and effaces, amniotic sac ruptures
• Expulsion: infant passes through the cervix and vagina. Typically lasts 50 minutes (first birth), or 20 minutes(subsequent births).
• Placental: delivery of the placenta; usually accomplished within 15 minutes after birth.

Developmental Aspects of the Reproductive System

• Gender Determination: determined at fertilization (XY for males, XX for females)
• Gonads begin to form in the 8th week
• Puberty: ages 10-15 and is signaled by certain developments in males and females:
• Males: enlargement of testes and scrotum
• Females: budding of the breasts
• Both: Menarche (first menstrual period)
• Menopause: occurs when a whole year passes without menstruation and the ovaries stop producing hormones. Males do not experience a similar event, but there is a steady decline of testosterone.

A Closer Look: Contraception

• Methods Include:
• Hormonal contraceptives (pill, patch, shot, ring): reduce ovarian hormone production to prevent ovulation and menstrual flow.
• Morning-after pill (MAP): disrupts normal hormone signals to prevent fertilization.
• Other hormonal birth control devices: thicken the cervical mucus.
• Intrauterine devices (IUDs): prevent implantation of a fertilized egg.
• Sterilization (tubal ligation in females, vasectomy in males): permanently prevents gamete transport.
• Barrier methods: diaphragms, cervical caps, condoms, spermicidal foams, gels, sponges
• Withdrawal: (coitus interruptus) involves withdrawal of penis before ejaculation
• Rhythm method/fertility awareness: avoiding intercourse during ovulation or fertile period; checking basal temperature or monitoring changes in cervical mucus.
• Abortion (RU486/other methods): termination of pregnancy
• Miscarriage (spontaneous abortion) is common; typically occurs before a woman knows she's pregnant.