Male and Female Reproductive Systems & Heredity Notes

Male and Female Reproductive Systems

• Unit Student Learning Outcomes
  • Identify organs of the female and male reproductive systems and their functions. (CSLO 1)
  • Describe the functions of major male and female sex hormones during the life cycle. (CSLO 1)
  • Summarize the concepts of the reproductive process (CSLO 1, 2, 3).
  • Recognize interrelationships among the female and male reproductive systems related to common pathophysiology’s utilizing nursing judgment (CSLO 4).
  • Summarize the concepts of the reproductive process in relation to heredity (CSLO 1, 2, 3).

Gametes

• Specialized cells designed for reproducing
• Male gamete: spermatozoa.
• Female gamete: ova.
• Have only half of the chromosomes found in other body cells.

Primary and Accessory Organs

• Primary Organs
  • Gonads (or sex glands)
  • Produce gametes and make hormones.
    • Testes: Primary Male Organ
    • Ovary: Primary Female Organ
• Accessory Organs
  • Organs, ducts involved in transportation of the gametes, and exocrine glands involved.

Male Reproductive System

• Function
  • Manufacture spermatozoa
  • Deliver the spermatozoa to the female reproductive tract.
• Primary Organs
  • 2 testes
• Accessory organs
  • Penis
  • Scrotum
  • Prepuce
  • Seminiferous tubules
  • Epididymis
  • Ductus deferens
  • Seminal vesicle
  • Ejaculatory duct
  • Urethra
  • Prostate gland
  • Bulbourethral glands

Epididymis

• Where the testes deliver sperm.
• A greatly coiled tube.
• Where sperm cells mature.
• Extends upward into the ductus deferens (vas deferens).

Semen

• Function
  • Nourish and transport spermatozoa
  • Neutralize acidity of male urethra and female vaginal tract
  • Lubrication
  • Prevent infection with antibacterial enzymes and antibodies
• Composition
  • Alkalotic mixture
  • Contains sperm cells and different secretions
  • Is expelled from the body

Glands Contributing to Seminal Secretions

• Seminal Vesicles
  • Thick yellow alkaline fluid is secreted
  • Has a large number of simple sugars and other substances for nourishment for the sperm.
  • Makes up a lot of the volume of semen.
• Prostate Gland
  • Thin alkaline secretion
  • Decreases acidity
  • Enhances sperm motility.
  • Muscular tissues contract and helps expel semen.
• Bulbourethral Glands (Cowper Glands)
  • A pair of glands below the prostate.
  • Secrete mucus for lubrication.
  • Empty into the urethra.

Male Urethra

• Conveys urine from bladder and semen from ejaculatory duct to outside of body.

Penis

• Spongey tissue that fills with blood.
• Has 3 segments
  • Corpus (body)
  • Corpus spongiosum
  • Corpus cavernosum

Testis

• Pair
• Outside the body suspended inside the scrotum
• Descends 1-2 months after birth.

Internal Structures

• Seminiferous tubules
  • Tiny coiled tubes
  • Has primitive cells in the walls that develop into sperm aided by sustentacular cells that nourish and protect the developing sperm.
• Interstitial Cells
  • Located between the seminiferous tubules
  • Secrete testosterone.
• Spermatozoa
  • Tiny individual cells
  • Start making them at puberty in the seminiferous tubules.
  • Has an oval head that is mostly a nucleus containing chromosomes.
  • Has a tail (flagellum) that propels it to the egg.
  • Middle area has mitochondria for energy.

Male Hormones

• 2 hormones from the anterior pituitary control the testes
  • Gonadotropins
    • FSH (follicle stimulating hormone)
    • LH (Luteinizing Hormone)
• FSH
  • Promotes the formation of spermatozoa.
  • It tells the testes to form more sperm.
• LH
  • Stimulates interstitial cells to produce testosterone that’s needed for sperm development.
  • Tells the interstitial cells to make testosterone to develop sperm.
• Testosterone (Hormone from the testes)
  • Develops and maintains the male reproductive accessory organs.
  • Development of spermatozoa.
  • Development of secondary sex characteristics (Deeper voice, broader shoulders, more body hair).

Age-Related Changes in Males

• Decreased production
  • Sperm
  • Testosterone
• Decreased
  • Sperm motility
  • Sperm quality
• More commonly seen with aging
  • BPH
    • Benign Prostatic Hyperplasia
    • Nonmalignant enlargement of the prostate
  • ED
    • Erectile dysfunction

Female Reproductive System

• Female gonads
  • Paired ovaries
  • Where the gametes (ova) are formed.
• Female gametes
  • Ova
• Accessory organs
  • Uterus
  • uterine tubes
  • vagina
  • greater vestibular glands
  • vulva
  • breasts

Uterus

• Pear-shaped muscular organ where the fetus develops
  • Body: Wide upper region
  • Fundus: Small rounded area above the body and tube entrance.
  • Cervix: Lower narrower region.
• Layers of the Uterus
  • Perimetrium: Outer layer
  • Myometrium: Muscular wall
  • Endometrium: Inner layer and Lining of the uterus

Uterine Tubes

• Paired
• Extend from the uterus to near the ovary but don’t directly connect to the ovary.
• Fimbriae
  • Small fringe-like extension of the tubes opening
  • Sweeps ovum into tube

Vagina

• Part of the birth canal
• Has a mucus membrane lining
• Surface is stratified squamous epithelium.
• Receives the penis during sexual intercourse.
• Sperm travels thru the vagina to the uterus for fertilization in the uterine tube.

Vulva

• External female genitalia
  • Pair of labia majora
  • Pair of labia minora
  • Clitoris
  • Openings of the urethra and vagina
  • Mons pubis

Perineum

• Area between vaginal area and anus.

Greater Vestibular Glands

• Paired glands
• Produces mucus
• Provides lubrication

The Ovaries and Ova

• Ovary
  • They produce the ova.
  • Outer layer is a single layer of epithelium.
  • Ova are produced beneath this layer.
  • The developing oocyte is inside an ovarian follicle.
  • An ovarian follicle is a small cluster of cells that protect the ovum and produce hormones.
• Females are born with all the gametes they will ever produce.
• Each month one developing follicle (usually just one) completes the maturation process and releases the ovum inside.

Female Reproductive Cycle

• Regular cyclic patterns of increases and decreases of hormone levels controlled by FSH & LH.
• The 1st day of menstrual flow is considered the 1st day of the cycle.
• Ovulation
  • Release of gamete from ovary
  • It’s what separates the reproductive cycle from the preovulatory (follicular) phase and postovulatory (luteal) phase.
• As the follicle grows it produces different amounts of ovarian hormones that cause the changes in the uterus.
• Uterine events
  • Proliferative phase
  • Secretory phase
• Ovarian events
  • Preovulatory phase
    • From menstruation leading up to ovulation.
  • Postovulatory phase
    • When the ovum moves thru the uterine tube to the uterus.

Preovulatory (Follicular) Phase

• FSH
  • Stimulates follicles to mature.
  • The follicle contains an immature ovum.
  • As it matures, it enlarges and fluid accumulates inside.
  • During growth, the follicle secretes more and more estrogen.
  • This stimulates further growth of the follicle.
  • Most follicles die off.
  • Usually, only a single follicle survives to release its ovum.
• Estrogen
  • Prepares the endometrium for pregnancy.
  • Thickens the endometrium.
  • As levels become high it stimulates an LH surge.

Ovulation & Post-Ovulatory Phase

• The LH surge triggers ovulation.
  • Ovulation usually occurs about 1 day after the LH surge.
  • The ovarian follicle ruptures and releases the ovum into the peritoneum where it begins its journey to the uterus.
  • The ovum is propelled into the uterine tube.
• LH also transforms the ruptured follicle into the corpus luteum.
• Corpus luteum secretes estrogen and progesterone.
  • Progesterone is a hormone that promotes the survival of a fertilized ovum and eventually an embryo.
  • Estrogen and progesterone cause the endometrium to continue to thicken.
  • Rising levels of estrogen and progesterone inhibit the release of FSH and LH (negative fb system).
• If the ovum is fertilized it will begin to secrete hormones that maintain the corpus luteum for a few months.
• If not fertilized it dies within 2-3 days and degenerates about 11 days post ovulation.

Menstruation and Menopause

• Menstruation
  • If ovum is not fertilized, the corpus luteum degenerates.
  • The lining of the endometrium is shed.
• Menopause
  • Menstruation ceases altogether
  • Often around ages 45-55 years old
  • Normal decline in ovarian function
  • A decrease in estrogen level can cause unpleasant symptoms
  • Can be given hormone replacement therapy for this if they desire.

Pregnancy

• Begins with fertilization of ovum
• Ends with childbirth
• Period of development called gestation
• Obstetrics is the care of women before, during, and 6 weeks after childbirth.
• Trimesters
  • 1st: First 3 months
  • 2nd trimester: Months 4-6
  • 3rd trimester: Months 7-birth

Fertilization

• Occurs in the uterine tube when nuclei of sperm and egg combine.
• This union is a single cell called a zygote
  • Has 46 chromosomes, 23 from the mother and 23 from the father (egg and sperm).
• The zygote divides rapidly into 2, then 4, and soon forms a ball of identical cells we call a morula.
  • While the zygote is growing into a morula, it’s traveling toward the uterine cavity.
• Before reaching the uterus the morula develops into a blastocyst.
  • A blastocyst is a partially hollow structure.

Implantation

• Blastocyst
  • Burrows into thick uterine lining until completely covered.
  • After implantation, the inner mass becomes an embryo.
• Inner mass
  • A group of cells within the blastocyst.
• Trophoblasts
  • The rest of the blastocyst cells (besides the inner mass).
  • It will become tissue that supports the developing offspring.
• Embryo
  • A growing offspring in the early stage of gestation.
• Fetus
  • Growing offspring from the beginning of the third month of gestation until birth.

Placenta

• Meets the needs of the offspring.
• Consists of maternal and embryonic tissue.
• The organ of nutrition, respiration, and excretion throughout gestation for the offspring.

Umbilical Cord

• How the embryo is connected to the placenta.
• AVA
  • 2 arteries, 1 vein

Fetal Circulation

• Special circulatory mechanisms
• Allows blood to be carried to and from the umbilical cord.
• Bypasses offspring's nonfunctioning lungs.

Hormones Involved in Pregnancy

• Human Chorionic Gonadotropin (hCG)
  • The blastocyst produces this soon after implantation.
  • Stimulates the growth of the corpus luteum.
  • Only occurs in fetal tissues.
  • The presence is an indicator of pregnancy.
  • What a pregnancy test screens for.
• Progesterone
  • Essential for the maintenance of pregnancy.
  • Promotes endometrial secretions to nourish the embryo.
  • Maintains the endometrium and decreases uterine muscle's ability to contract.
  • Prepares breasts for milk secretion.
• Estrogen
  • Enlargement of uterus and breasts
• Relaxin
  • Placental hormone that softens the cervix and relaxes sacral joints and pubic symphysis.
  • Helps widen the birth canal to facilitate birth.

Corpus Luteum and Development

• Corpus Luteum
  • hCG stimulates the growth of the corpus luteum.
  • Continues to grow and produce increasing amounts of progesterone and estrogen for about 11-12 weeks post-fertilization and then degenerates.
  • The placenta is now formed, functioning, and producing adequate amounts of progesterone and estrogen.
• Development of the Embryo
  • 1st 8 weeks of life.
  • The developing embryo is very sensitive to harmful substances and poor maternal nutrition.
  • When all body systems are established.
    • The heart and brain are first.
    • The primitive nervous system begins to form in the 3rd week.
    • The heart and blood vessels originate during the 2nd week, and the 1st heartbeat appears during week 4.

Development of the Fetus

• Beginning of 3rd months until birth
• Organs grow and mature
• Amniotic Sac
  • Filled with amniotic fluid
  • Surrounds the fetus
  • Protective cushion
• Fetus’ Skin
  • Protected by cheese-like substance vernix caseosa.

Genes & Chromosomes

• Genes
  • Segments of DNA inside the chromosomes that are in the nucleus of every cell.
  • Govern cells by controlling the manufacture of protein, especially enzymes.
  • Each version of a specific gene is an allele.
• Chromosomes
  • All cells except the gametes have 46.
  • They exist in pairs.
  • One of the pair came from the mother of the offspring while the other came from the father.
  • The paired chromosomes (except for the pair that determines sex) are alike.
  • Since chromosomes are paired and come from each parent we have 2 alleles for every gene.
• Autosomes
  • 22 chromosome pairs not involved in sex determination
• Sex chromosomes
  • 1 pair, the 23rd pair.
  • involved in the sex determination.

Heredity

• Homozygous
  • Both alleles are the same
• Heterozygous
  • The alleles are different
• Dominant allele
  • Expresses its effect no matter what the other allele is.
  • Only needed from one parent.
• Recessive allele
  • Only seen if both alleles are recessive.
• Phenotype
  • Characteristic observed
  • What is expressed
• Genotype
  • What the allele actually is despite what is expressed.

Meiosis

• How sperm and ova are produced.
• Divides the number of chromosomes in half.
• Each reproductive cell will have 23 chromosomes instead of the original 46.
• At the end of meiosis, a single cell produces 4 cells.
• Each cell contains 22 autosomes and one sex chromosome.

Punnett Squares & Sex Determination

• Punnett Square
  • Grid used by geneticists.
  • Shows all possible combinations of an allele that can result from one mating.
• Sex Determination
  • Male XY
    • Has one x and one y chromosome
    • Gets one X from the mother and one Y from the father.
    • Y Chromosome
      • Smaller than other chromosomes
      • Mainly determines sex
      • Sex is determined by the receipt of the Y chromosome from the father.
  • Female XX
    • Two X chromosomes
    • Gets one x chromosome from the mother and one x chromosome from the father.

Gene Mutation

• Any change in a gene or chromosome.
• May occur spontaneously.
• Can also be induced by an agent called a mutagen.
• If a mutation occurs in ovum or sperm the altered trait may be inherited by an offspring.
• Some mutations can be beneficial.