Lecture 20 Materials -Reproduction
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Questions and Answers

What is the main function of meiosis?

  • To increase genetic diversity and produce gametes with 23 chromosomes (correct)
  • To produce somatic cells with 23 chromosomes
  • To produce gametes with 46 chromosomes
  • To produce somatic cells with 46 chromosomes

    • How many chromosomes do gametes have?

  • Thousands
  • 46
  • 23 (correct)
  • 20,000

    • What is the result of fertilization?

  • A genetically unique individual with 46 chromosomes (correct)
  • A genetically identical individual with 23 chromosomes
  • A genetically identical individual with 46 chromosomes
  • A genetically diverse individual with 20,000 chromosomes

    • What is the purpose of gametes?

    <p>To combine genetic information to produce offspring</p> Signup and view all the answers

    What is the number of genes in the human body?

    <p>20,000</p> Signup and view all the answers

    What is the result of meiosis in the testes?

    <p>Four genetically unique sperm cells</p> Signup and view all the answers

    What is the function of somatic cells?

    <p>To make up the body except for gametes</p> Signup and view all the answers

    What is the number of chromosomes in somatic cells?

    <p>46</p> Signup and view all the answers

    What is produced in the ovaries through meiosis?

    <p>One mature egg cell and several smaller cells</p> Signup and view all the answers

    What is the purpose of reproduction?

    <p>To combine genetic information to produce offspring</p> Signup and view all the answers

    Fertilization occurs in the ovaries and results in a genetically unique individual with 46 chromosomes.

    <p>False</p> Signup and view all the answers

    Gametes have 23 pairs of chromosomes.

    <p>False</p> Signup and view all the answers

    Sperm cells are produced in the ovaries.

    <p>False</p> Signup and view all the answers

    Chromosomes are molecules of RNA.

    <p>False</p> Signup and view all the answers

    Somatic cells have 23 chromosomes.

    <p>False</p> Signup and view all the answers

    Meiosis occurs in all cells of the body.

    <p>False</p> Signup and view all the answers

    Gametes are produced through mitosis.

    <p>False</p> Signup and view all the answers

    Reproduction involves making offspring through the combination of genetic information from three individuals.

    <p>False</p> Signup and view all the answers

    Fertilization results in a genetically identical individual with 46 chromosomes.

    <p>False</p> Signup and view all the answers

    Meiosis results in four genetically identical sperm cells in the ovaries.

    <p>False</p> Signup and view all the answers

    Where are sperm cells produced in the male reproductive system?

    <p>Seminiferous tubules</p> Signup and view all the answers

    What is the role of Sertoli cells in sperm production?

    <p>To modify and nourish sperm cells</p> Signup and view all the answers

    Which hormone stimulates Leydig cells to produce testosterone?

    <p>Luteinizing hormone (LH)</p> Signup and view all the answers

    What is the role of testosterone in the development of the reproductive system?

    <p>It promotes the maturation of the reproductive system and growth of reproductive organs</p> Signup and view all the answers

    Where are eggs produced in the female reproductive system?

    <p>Ovaries</p> Signup and view all the answers

    What is the process by which eggs are produced in the ovaries?

    <p>Meiosis</p> Signup and view all the answers

    What is the role of estrogen and progesterone in the female reproductive system?

    <p>They are produced by the granulosa cells within the ovaries during egg development</p> Signup and view all the answers

    How many eggs are produced in the ovaries during fetal development?

    <p>All eggs a female will ever have</p> Signup and view all the answers

    What is the role of the blood-testis barrier in the male reproductive system?

    <p>To protect the sperm from the immune system and harmful chemicals</p> Signup and view all the answers

    What happens to the egg cells during fetal development?

    <p>They are stored in the ovaries</p> Signup and view all the answers

    Sperm cells are produced in the ovaries through meiosis

    <p>False</p> Signup and view all the answers

    Sertoli cells form a blood-testis barrier to protect the sperm from the immune system

    <p>True</p> Signup and view all the answers

    Leydig cells produce estrogen and progesterone

    <p>False</p> Signup and view all the answers

    Egg production occurs in the seminiferous tubules through meiosis

    <p>False</p> Signup and view all the answers

    All eggs a female will ever have are formed during fetal development and are stored in the ovaries

    <p>True</p> Signup and view all the answers

    Meiosis is completed in the ovaries even if fertilization does not occur

    <p>False</p> Signup and view all the answers

    Testosterone is necessary for the maturation of the reproductive system and growth of reproductive organs at puberty

    <p>True</p> Signup and view all the answers

    Follicle stimulating hormone (FSH) stimulates Leydig cells to produce testosterone

    <p>False</p> Signup and view all the answers

    Sperm cells are initially oval and take on their typical appearance without modification

    <p>False</p> Signup and view all the answers

    Estrogen and progesterone are produced by the Sertoli cells in the testes

    <p>False</p> Signup and view all the answers

    What is the primary function of the testes?

    <p>To produce testosterone and store sperm</p> Signup and view all the answers

    Where do immature sperm mature and get stored?

    <p>Epididymis</p> Signup and view all the answers

    What is the purpose of the prostate gland?

    <p>To produce fluids that make up semen</p> Signup and view all the answers

    What is the function of the seminal vesicles?

    <p>To produce fluids that make up semen</p> Signup and view all the answers

    What is the purpose of the bulbourethral glands?

    <p>To produce a pre-ejaculate that helps neutralize urine in the urethra</p> Signup and view all the answers

    What occurs in the seminiferous tubules within the testes?

    <p>Sperm production through meiosis</p> Signup and view all the answers

    What is the common function of the urethra?

    <p>To transport both sperm and urine</p> Signup and view all the answers

    Where do sperm from the epididymis travel to during ejaculation?

    <p>Vas deferens</p> Signup and view all the answers

    What is the function of the penis?

    <p>To deliver sperm to the female reproductive tract</p> Signup and view all the answers

    What type of cell division occurs in the testes to produce sperm?

    <p>Meiosis</p> Signup and view all the answers

    The testes produce sperm through a special type of cell division called mitosis.

    <p>False</p> Signup and view all the answers

    The urethra is only responsible for transporting urine during urination.

    <p>False</p> Signup and view all the answers

    The epididymis is responsible for producing testosterone.

    <p>False</p> Signup and view all the answers

    The seminal vesicles produce fluids that make up the majority of urine.

    <p>False</p> Signup and view all the answers

    Sperm cells undergo differentiation to take on their typical head, neck, and flagellum structure in the epididymis.

    <p>False</p> Signup and view all the answers

    The prostate gland produces fluids that dump into the vas deferens.

    <p>False</p> Signup and view all the answers

    The bulbourethral glands produce a pre-ejaculate that helps facilitate fertilization.

    <p>False</p> Signup and view all the answers

    The vas deferens is a tube that transports sperm from the testes during ejaculation.

    <p>False</p> Signup and view all the answers

    The penis is the structure that delivers urine to the outside of the body.

    <p>False</p> Signup and view all the answers

    The ejaculatory duct is where sperm from the vas deferens and fluids from the bulbourethral glands combine.

    <p>False</p> Signup and view all the answers

    What is the primary function of the ovaries in the female reproductive system?

    <p>To produce eggs and female sex steroids</p> Signup and view all the answers

    Which part of the female reproductive system transports the egg towards the uterus?

    <p>Fallopian tube</p> Signup and view all the answers

    What is the main function of the cervix in the female reproductive system?

    <p>To dilate during childbirth</p> Signup and view all the answers

    Which part of the female reproductive system serves as the birth canal during childbirth?

    <p>Vagina</p> Signup and view all the answers

    What is the function of the clitoris in the female reproductive system?

    <p>To facilitate female arousal and orgasm</p> Signup and view all the answers

    What is the purpose of the labia in the female reproductive system?

    <p>To cover the vaginal opening and urethra</p> Signup and view all the answers

    What is the site of fertilization in the female reproductive system?

    <p>Fallopian tube</p> Signup and view all the answers

    What is the role of estrogen and progesterone in the female reproductive system?

    <p>To produce female sex steroids</p> Signup and view all the answers

    What is the function of the smooth muscle walls in the uterus?

    <p>To contract and dilate during childbirth</p> Signup and view all the answers

    What is stored in the ovaries during fetal development?

    <p>Eggs</p> Signup and view all the answers

    The ovaries produce eggs through mitosis, a special type of cell division.

    <p>False</p> Signup and view all the answers

    Cilia in the epithelial cells of the Fallopian tube push the sperm towards the uterus.

    <p>False</p> Signup and view all the answers

    The cervix is the upper part of the uterus that extends into the abdominal cavity.

    <p>False</p> Signup and view all the answers

    The vagina serves as the birth canal during pregnancy.

    <p>True</p> Signup and view all the answers

    The clitoris and labia become engorged with air and secrete fluid during arousal.

    <p>False</p> Signup and view all the answers

    The uterus has smooth muscle walls that cannot contract.

    <p>False</p> Signup and view all the answers

    Eggs are produced in the ovaries through a process called mitosis.

    <p>False</p> Signup and view all the answers

    The Fallopian tube is the site of fertilization and transports the sperm towards the uterus.

    <p>False</p> Signup and view all the answers

    The vulva is the upper part of the vagina that connects to the cervix.

    <p>False</p> Signup and view all the answers

    The ovaries produce eggs that are stored in the Fallopian tube until puberty.

    <p>False</p> Signup and view all the answers

    During ejaculation, where do sperm travel from?

    <p>Epididymis</p> Signup and view all the answers

    What is the purpose of the alkaline secretions in semen?

    <p>To neutralize the acidity of the vagina</p> Signup and view all the answers

    What facilitates sperm travel through the uterus?

    <p>Uterine contractions and prostaglandins</p> Signup and view all the answers

    What is the location of fertilization?

    <p>Fallopian tube</p> Signup and view all the answers

    What is the purpose of a vasectomy?

    <p>To cut or sever the vas deferens</p> Signup and view all the answers

    What is the role of the cilia in the Fallopian tube?

    <p>To push the fertilized egg towards the uterus</p> Signup and view all the answers

    What happens to the fertilized egg if it implants outside the uterus?

    <p>It is an ectopic pregnancy, which is dangerous and potentially fatal</p> Signup and view all the answers

    What occurs in the cervix around ovulation?

    <p>The mucous plug becomes thinner</p> Signup and view all the answers

    What is the function of the bulbourethral gland?

    <p>To produce alkaline secretions</p> Signup and view all the answers

    What is the purpose of tubal ligation as a contraception method?

    <p>To cut or sever the Fallopian tubes</p> Signup and view all the answers

    Sperm travel through the urethra and out the vas deferens during sexual intercourse.

    <p>False</p> Signup and view all the answers

    The vagina is alkaline, and semen's acidic secretions help neutralize the alkalinity.

    <p>False</p> Signup and view all the answers

    Fertilization occurs in the ovary.

    <p>False</p> Signup and view all the answers

    The fertilized egg implants in the Fallopian tube.

    <p>False</p> Signup and view all the answers

    Vasectomy involves cutting or severing the urethra, making it difficult for sperm to exit.

    <p>False</p> Signup and view all the answers

    Sperm are deposited in the lower portion of the vagina during sexual intercourse.

    <p>False</p> Signup and view all the answers

    The uterine contractions and prostaglandins in semen help push the fertilized egg towards the Fallopian tube.

    <p>False</p> Signup and view all the answers

    The cilia in the uterus help push the fertilized egg towards the Fallopian tube.

    <p>False</p> Signup and view all the answers

    If the fertilized egg implants in the Fallopian tube, it's an ectopic pregnancy.

    <p>False</p> Signup and view all the answers

    Tubal ligation involves tying or cauterizing the vas deferens to prevent sperm from exiting.

    <p>False</p> Signup and view all the answers

    What triggers the development of secondary sex characteristics during puberty?

    <p>Increased GnRH release from the hypothalamus</p> Signup and view all the answers

    What is the role of the anterior pituitary gland in the regulation of the reproductive system?

    <p>To regulate hormone release from the testes and ovaries</p> Signup and view all the answers

    What is the effect of low body fat levels on puberty onset in females?

    <p>It delays puberty onset</p> Signup and view all the answers

    What is the role of FSH in the regulation of testosterone production?

    <p>To stimulate sperm production in the testes</p> Signup and view all the answers

    What is the result of increased hormone levels during puberty?

    <p>Development of both gametes and secondary sex characteristics</p> Signup and view all the answers

    What is the role of testosterone in the development of the reproductive system?

    <p>To promote secondary male sex characteristics and sperm production</p> Signup and view all the answers

    What is the effect of endocrine disruptors in the environment on puberty onset?

    <p>They may be affecting puberty onset</p> Signup and view all the answers

    Which hormone stimulates the anterior pituitary to release FSH and LH?

    <p>GnRH</p> Signup and view all the answers

    What is the role of the hypothalamus in the regulation of the reproductive system?

    <p>To control the anterior pituitary gland</p> Signup and view all the answers

    What happens to hormone levels during fetal development?

    <p>They are low until a brief period of masculinization in male fetuses</p> Signup and view all the answers

    During fetal development, hormone levels are consistently high until the onset of puberty.

    <p>False</p> Signup and view all the answers

    The hypothalamus releases FSH and LH, which stimulate testosterone and estrogen production.

    <p>False</p> Signup and view all the answers

    Breast tissue development and fat deposition occur in males during puberty.

    <p>False</p> Signup and view all the answers

    Increased hormone levels during puberty trigger the development of secondary sex characteristics, including armpit and pubic hair growth in females only.

    <p>False</p> Signup and view all the answers

    Gamete production begins during fetal development.

    <p>False</p> Signup and view all the answers

    The anterior pituitary gland regulates hormone release from the hypothalamus.

    <p>False</p> Signup and view all the answers

    LH stimulates Sertoli cells to release testosterone.

    <p>False</p> Signup and view all the answers

    Body fat levels have no effect on puberty onset.

    <p>False</p> Signup and view all the answers

    Endocrine disruptors in the environment have no effect on puberty onset.

    <p>False</p> Signup and view all the answers

    FSH acts on the testes to stimulate Leydig cells to release testosterone.

    <p>False</p> Signup and view all the answers

    Testosterone has positive feedback effects on the anterior pituitary and hypothalamus to maintain steady hormone levels.

    <p>False</p> Signup and view all the answers

    What happens to estrogen and progesterone levels when the corpus luteum regresses?

    <p>They drop</p> Signup and view all the answers

    How do hormonal contraceptives prevent ovulation and fertilization?

    <p>By maintaining low-ish levels of estrogen and progesterone</p> Signup and view all the answers

    What is an additional mechanism by which hormonal contraceptives prevent fertilization?

    <p>Thickening cervical mucus</p> Signup and view all the answers

    Why is the emergency contraceptive less effective than other hormonal contraceptives?

    <p>Because it is taken after sexual intercourse and may not delay ovulation long enough to prevent fertilization</p> Signup and view all the answers

    What is the result of the decrease in estrogen and progesterone levels?

    <p>The uterine lining is shed</p> Signup and view all the answers

    What is the purpose of maintaining low-ish levels of estrogen and progesterone in hormonal contraceptives?

    <p>To prevent ovulation and fertilization</p> Signup and view all the answers

    What is the effect of hormonal contraceptives on the uterine lining?

    <p>It keeps the uterine lining thin</p> Signup and view all the answers

    Why do hormonal contraceptives prevent implantation?

    <p>Because they keep the uterine lining thin</p> Signup and view all the answers

    What is the common mechanism by which hormonal contraceptives prevent pregnancy?

    <p>By preventing ovulation and fertilization</p> Signup and view all the answers

    What stimulates the release of FSH and LH from the anterior pituitary?

    <p>GnRH</p> Signup and view all the answers

    What is the primary role of FSH in the female reproductive system?

    <p>Stimulating the development of the follicle in the ovaries</p> Signup and view all the answers

    At what point in the menstrual cycle is ovulation triggered?

    <p>Day 14 of the menstrual cycle</p> Signup and view all the answers

    What is the function of the corpus luteum in the ovary?

    <p>Producing estrogen and progesterone</p> Signup and view all the answers

    What is the result of low estrogen and progesterone levels in the menstrual cycle?

    <p>The uterine lining is shed, resulting in menstruation</p> Signup and view all the answers

    What is the primary function of estrogen and progesterone in the female reproductive system?

    <p>Preparing the uterine lining for implantation</p> Signup and view all the answers

    What is the negative feedback effect of estrogen and progesterone on the hypothalamic-pituitary axis?

    <p>Inhibiting the release of FSH and LH</p> Signup and view all the answers

    What is the result of a surge in LH levels in the female reproductive system?

    <p>Ovulation is triggered</p> Signup and view all the answers

    The hypothalamic-pituitary axis regulates male reproduction.

    <p>False</p> Signup and view all the answers

    FSH triggers ovulation and the release of eggs from the ovary.

    <p>False</p> Signup and view all the answers

    At low levels, estrogen and progesterone have positive feedback effects on the hypothalamus and anterior pituitary.

    <p>False</p> Signup and view all the answers

    The corpus luteum forms in the ovary after menstruation.

    <p>False</p> Signup and view all the answers

    The menstrual cycle refers to the changes in the ovaries.

    <p>False</p> Signup and view all the answers

    Estrogen and progesterone levels decrease after ovulation.

    <p>False</p> Signup and view all the answers

    The uterine lining is shed due to high estrogen and progesterone levels.

    <p>False</p> Signup and view all the answers

    Ovulation is triggered by a surge in FSH levels.

    <p>False</p> Signup and view all the answers

    As the corpus luteum regresses, estrogen and progesterone levels increase, and the uterine lining is maintained.

    <p>False</p> Signup and view all the answers

    Hormonal contraceptives prevent ovulation by maintaining high levels of estrogen and progesterone.

    <p>False</p> Signup and view all the answers

    The emergency contraceptive is more effective than other forms of hormonal contraceptives.

    <p>False</p> Signup and view all the answers

    Hormonal contraceptives can prevent fertilization by thinning cervical mucus.

    <p>False</p> Signup and view all the answers

    The uterine lining is maintained when estrogen and progesterone levels are low.

    <p>False</p> Signup and view all the answers

    Hormonal contraceptives work by stimulating the release of FSH and LH.

    <p>False</p> Signup and view all the answers

    The corpus luteum regression is triggered by high estrogen and progesterone levels.

    <p>False</p> Signup and view all the answers

    Hormonal contraceptives can keep the uterine lining thick, making it easier for implantation to occur.

    <p>False</p> Signup and view all the answers

    The emergency contraceptive is taken before sexual intercourse to prevent ovulation.

    <p>False</p> Signup and view all the answers

    During which period do major organs begin to form?

    <p>Embryonic period</p> Signup and view all the answers

    What is the length of the embryo at the end of the embryonic period?

    <p>About an inch long</p> Signup and view all the answers

    Why is the embryonic period susceptible to environmental factors?

    <p>Because the embryo is more susceptible to birth defects and chromosomal abnormalities</p> Signup and view all the answers

    What is the estimated percentage of pregnancies that fail to implant or miscarry during the embryonic period?

    <p>33.3 to 50 percent</p> Signup and view all the answers

    When does the fetal period begin?

    <p>At week nine</p> Signup and view all the answers

    What happens to the fetus during the fetal period?

    <p>The fetus continues to grow and develop</p> Signup and view all the answers

    What is the main difference between the embryonic and fetal periods?

    <p>The embryonic period is more susceptible to environmental factors</p> Signup and view all the answers

    What is the primary focus of the embryonic period?

    <p>Organ formation</p> Signup and view all the answers

    What is the outcome of the fetal period?

    <p>A full-sized baby is formed</p> Signup and view all the answers

    During which period of human development is the fertilized egg called a zygote?

    <p>Pre-embryonic period</p> Signup and view all the answers

    What is the result of fertilization in the Fallopian tube?

    <p>A single-cell fertilized egg called a zygote</p> Signup and view all the answers

    What occurs during the blastocyst phase?

    <p>All of the above</p> Signup and view all the answers

    What hormone ensures that the pregnancy is maintained during implantation?

    <p>Human chorionic gonadotropin (HCG)</p> Signup and view all the answers

    What forms during implantation?

    <p>The placenta and the amniotic sac</p> Signup and view all the answers

    What is the correct sequence of development during the pre-embryonic period?

    <p>Zygote, morula, blastocyst</p> Signup and view all the answers

    How is pregnancy typically measured?

    <p>From the last menstrual period (LMP)</p> Signup and view all the answers

    During which period of human development does the zygote undergo mitosis?

    <p>Pre-embryonic period</p> Signup and view all the answers

    What can cause birth defects, especially at high levels?

    <p>Radiation</p> Signup and view all the answers

    What is a nutritional deficiency that can result in birth defects?

    <p>Insufficient folic acid intake</p> Signup and view all the answers

    What is a critical period for development, and exposure to risk factors during this period can have a significant impact on the developing fetus?

    <p>Embryonic period (3-8 weeks post-fertilization)</p> Signup and view all the answers

    What can cause birth defects, including fetal alcohol syndrome?

    <p>Chemicals such as alcohol</p> Signup and view all the answers

    What is an infection that can cause birth defects, including microcephaly (smaller head size) and intellectual disability?

    <p>Zika virus</p> Signup and view all the answers

    What is a medication that can cause birth defects affecting the brain, heart, and face, and can result in conditions like cleft palate?

    <p>Accutane</p> Signup and view all the answers

    What is a genetic or inherited condition that can cause birth defects?

    <p>All of the above</p> Signup and view all the answers

    What can cause birth defects, including hydrocephaly (water on the brain) and intellectual disability?

    <p>Toxoplasmosis</p> Signup and view all the answers

    What is the timing that affects the likelihood of birth defects?

    <p>The timing and level of exposure to risk factors</p> Signup and view all the answers

    What determines chromosomal sex?

    <p>The set of sex chromosomes inherited during fertilization</p> Signup and view all the answers

    What triggers the development of testes?

    <p>The presence of a Y chromosome</p> Signup and view all the answers

    What determines phenotypic sex?

    <p>Hormones, such as testosterone</p> Signup and view all the answers

    What occurs when the phenotypic sex does not match the chromosomal sex?

    <p>Intersex conditions</p> Signup and view all the answers

    What is responsible for masculinization of internal and external structures?

    <p>Testosterone produced by the testes</p> Signup and view all the answers

    What is the result of the absence of a Y chromosome?

    <p>The development of ovaries</p> Signup and view all the answers

    What is the role of the SRY gene?

    <p>To trigger the development of testes</p> Signup and view all the answers

    What is an example of an intersex condition?

    <p>5-alpha-reductase deficiency</p> Signup and view all the answers

    What determines gonadal sex?

    <p>The development of ovaries or testes</p> Signup and view all the answers

    What is the role of hormones in determining phenotypic sex?

    <p>Hormones, such as testosterone, play a crucial role in determining phenotypic sex</p> Signup and view all the answers

    Study Notes

    Reproduction and Fertilization

    • Reproduction involves making offspring or babies through the combination of genetic information from two individuals.
    • Fertilization is the fusion of sperm and egg, resulting in a genetically unique individual with 46 chromosomes.

    Gametes

    • Gametes are sex cells: sperm (male gamete) and egg (female gamete).
    • Sperm is produced in the testes, while the egg is produced in the ovaries.
    • Gametes have half the number of chromosomes (23) compared to somatic cells (46).

    Chromosomes and Genes

    • Chromosomes are molecules of DNA.
    • Humans have 23 pairs of chromosomes (46 total) in somatic cells, except for gametes which have 23.
    • Chromosomes contain thousands of genes, with approximately 20,000 genes in the human body.

    Somatic Cells

    • Somatic cells are all cells in the body except for gametes (sperm and egg).
    • They have 46 chromosomes, with 23 pairs of homologous chromosomes.
    • One chromosome in each pair comes from each parent.

    Meiosis and Gametogenesis

    • Meiosis is a special type of cell division that occurs in the gonads (testes and ovaries).
    • Meiosis involves two successive rounds of division, resulting in gametes with half the number of chromosomes (23).
    • Meiosis increases genetic diversity and occurs only in the gonads.

    Gamete Production

    • In the ovaries, meiosis results in one mature egg cell and several smaller cells that are not viable.
    • In the testes, meiosis results in four genetically unique sperm cells.
    • Fertilization combines the genetic material from the sperm and egg, resulting in a zygote with 46 chromosomes.

    Reproduction and Fertilization

    • Reproduction involves combining genetic information from two individuals to produce offspring.
    • Fertilization is the fusion of sperm and egg, resulting in a genetically unique individual with 46 chromosomes.

    Gametes

    • Gametes are sex cells: sperm (male gamete) and egg (female gamete).
    • Sperm is produced in the testes, while the egg is produced in the ovaries.
    • Gametes have half the number of chromosomes (23) compared to somatic cells (46).

    Chromosomes and Genes

    • Chromosomes are molecules of DNA.
    • Humans have 23 pairs of chromosomes (46 total) in somatic cells, except for gametes which have 23.
    • Chromosomes contain thousands of genes, with approximately 20,000 genes in the human body.

    Somatic Cells

    • Somatic cells are all cells in the body except for gametes (sperm and egg).
    • They have 46 chromosomes, with 23 pairs of homologous chromosomes.
    • One chromosome in each pair comes from each parent.

    Meiosis and Gametogenesis

    • Meiosis is a special type of cell division that occurs in the gonads (testes and ovaries).
    • Meiosis involves two successive rounds of division, resulting in gametes with half the number of chromosomes (23).
    • Meiosis increases genetic diversity and occurs only in the gonads.

    Gamete Production

    • In the ovaries, meiosis results in one mature egg cell and several smaller cells that are not viable.
    • In the testes, meiosis results in four genetically unique sperm cells.
    • Fertilization combines the genetic material from the sperm and egg, resulting in a zygote with 46 chromosomes.

    Reproduction and Fertilization

    • Reproduction involves combining genetic information from two individuals to produce offspring.
    • Fertilization is the fusion of sperm and egg, resulting in a genetically unique individual with 46 chromosomes.

    Gametes

    • Gametes are sex cells: sperm (male gamete) and egg (female gamete).
    • Sperm is produced in the testes, while the egg is produced in the ovaries.
    • Gametes have half the number of chromosomes (23) compared to somatic cells (46).

    Chromosomes and Genes

    • Chromosomes are molecules of DNA.
    • Humans have 23 pairs of chromosomes (46 total) in somatic cells, except for gametes which have 23.
    • Chromosomes contain thousands of genes, with approximately 20,000 genes in the human body.

    Somatic Cells

    • Somatic cells are all cells in the body except for gametes (sperm and egg).
    • They have 46 chromosomes, with 23 pairs of homologous chromosomes.
    • One chromosome in each pair comes from each parent.

    Meiosis and Gametogenesis

    • Meiosis is a special type of cell division that occurs in the gonads (testes and ovaries).
    • Meiosis involves two successive rounds of division, resulting in gametes with half the number of chromosomes (23).
    • Meiosis increases genetic diversity and occurs only in the gonads.

    Gamete Production

    • In the ovaries, meiosis results in one mature egg cell and several smaller cells that are not viable.
    • In the testes, meiosis results in four genetically unique sperm cells.
    • Fertilization combines the genetic material from the sperm and egg, resulting in a zygote with 46 chromosomes.

    Sperm Production

    • Sperm cells are produced in the testes through meiosis in the seminiferous tubules.
    • The process of sperm production results in four genetically unique sperm cells.
    • Sperm cells are initially round and need to be modified to take on their typical appearance.
    • Sertoli cells play a crucial role in sperm modification and provide nourishment to the sperm.
    • Sertoli cells also form a blood-testis barrier to protect the sperm from the immune system and harmful chemicals.

    Sertoli Cells

    • Sertoli cells are found in the seminiferous tubules and respond to follicle stimulating hormone (FSH).
    • FSH is necessary for maximum sperm production and comes from the anterior pituitary.
    • Sertoli cells remodel the sperm and provide nourishment to them.
    • The blood-testis barrier formed by Sertoli cells protects the sperm from the immune system and harmful chemicals.

    Leydig Cells

    • Leydig cells are found in the interstitial tissue and produce testosterone in response to luteinizing hormone (LH) from the anterior pituitary.
    • Testosterone is a male sex steroid or hormone essential for:
      • Masculinization of accessory organs and structures during fetal development.
      • Maturation of the reproductive system and growth of reproductive organs at puberty.
      • Development of secondary sex characteristics.
      • Promoting protein synthesis and bone growth.
      • Stimulating spermatogenesis.

    Ovary and Egg Production

    • Ovaries are the female gonads responsible for producing eggs through meiosis.
    • Estrogen and progesterone are produced by the granulosa cells within the ovaries.
    • Estrogen and progesterone are female sex steroids produced during egg development.
    • All eggs a female will ever have are formed during fetal development and are stored in the ovaries.
    • From puberty to menopause, one egg is stimulated to mature each month.
    • Meiosis is not completed unless fertilization occurs.

    Sperm Production

    • Sperm cells are produced in the testes through meiosis in the seminiferous tubules.
    • The process of sperm production results in four genetically unique sperm cells.
    • Sperm cells are initially round and need to be modified to take on their typical appearance.
    • Sertoli cells play a crucial role in sperm modification and provide nourishment to the sperm.
    • Sertoli cells also form a blood-testis barrier to protect the sperm from the immune system and harmful chemicals.

    Sertoli Cells

    • Sertoli cells are found in the seminiferous tubules and respond to follicle stimulating hormone (FSH).
    • FSH is necessary for maximum sperm production and comes from the anterior pituitary.
    • Sertoli cells remodel the sperm and provide nourishment to them.
    • The blood-testis barrier formed by Sertoli cells protects the sperm from the immune system and harmful chemicals.

    Leydig Cells

    • Leydig cells are found in the interstitial tissue and produce testosterone in response to luteinizing hormone (LH) from the anterior pituitary.
    • Testosterone is a male sex steroid or hormone essential for:
      • Masculinization of accessory organs and structures during fetal development.
      • Maturation of the reproductive system and growth of reproductive organs at puberty.
      • Development of secondary sex characteristics.
      • Promoting protein synthesis and bone growth.
      • Stimulating spermatogenesis.

    Ovary and Egg Production

    • Ovaries are the female gonads responsible for producing eggs through meiosis.
    • Estrogen and progesterone are produced by the granulosa cells within the ovaries.
    • Estrogen and progesterone are female sex steroids produced during egg development.
    • All eggs a female will ever have are formed during fetal development and are stored in the ovaries.
    • From puberty to menopause, one egg is stimulated to mature each month.
    • Meiosis is not completed unless fertilization occurs.

    The Male Reproductive System

    • Consists of testes, epididymis, vas deferens, ejaculatory duct, urethra, penis, and accessory glands.

    Testes

    • Produce sperm and testosterone.
    • Housed in a pouch of skin called the scrotum.
    • Endocrine glands that produce testosterone.
    • Sperm production occurs in seminiferous tubules through meiosis, resulting in four genetically unique cells with half the genetic material as the original cell.
    • Sperm cells undergo differentiation to take on their typical head, neck, and flagellum structure.

    Epididymis

    • Tube-like structure where immature sperm from the testes mature and are stored.
    • Sperm leave the epididymis and travel through the vas deferens during ejaculation.

    Vas Deferens and Ejaculatory Duct

    • Vas deferens: tube that transports sperm from the epididymis during ejaculation.
    • Ejaculatory duct: where sperm from the vas deferens and fluids from the seminal vesicles combine.

    Urethra and Penis

    • Urethra: common tube for both sperm transport during ejaculation and urine transport during urination.
    • Penis: structure that delivers sperm to the female reproductive tract and contains erectile tissue that becomes engorged with blood during arousal.

    Accessory Glands

    • Seminal vesicles: produce fluids that make up the majority of semen, including alkaline fluids, prostaglandins, fructose, and enzymes.
    • Prostate gland: produces fluids that dump into the prostatic urethra.
    • Bulbourethral glands: produce a pre-ejaculate that helps neutralize urine in the urethra prior to ejaculation.

    The Male Reproductive System

    • Consists of testes, epididymis, vas deferens, ejaculatory duct, urethra, penis, and accessory glands.

    Testes

    • Produce sperm and testosterone.
    • Housed in a pouch of skin called the scrotum.
    • Endocrine glands that produce testosterone.
    • Sperm production occurs in seminiferous tubules through meiosis, resulting in four genetically unique cells with half the genetic material as the original cell.
    • Sperm cells undergo differentiation to take on their typical head, neck, and flagellum structure.

    Epididymis

    • Tube-like structure where immature sperm from the testes mature and are stored.
    • Sperm leave the epididymis and travel through the vas deferens during ejaculation.

    Vas Deferens and Ejaculatory Duct

    • Vas deferens: tube that transports sperm from the epididymis during ejaculation.
    • Ejaculatory duct: where sperm from the vas deferens and fluids from the seminal vesicles combine.

    Urethra and Penis

    • Urethra: common tube for both sperm transport during ejaculation and urine transport during urination.
    • Penis: structure that delivers sperm to the female reproductive tract and contains erectile tissue that becomes engorged with blood during arousal.

    Accessory Glands

    • Seminal vesicles: produce fluids that make up the majority of semen, including alkaline fluids, prostaglandins, fructose, and enzymes.
    • Prostate gland: produces fluids that dump into the prostatic urethra.
    • Bulbourethral glands: produce a pre-ejaculate that helps neutralize urine in the urethra prior to ejaculation.

    Female Reproductive Tract

    • Ovaries produce eggs and release female sex steroids (estrogen and progesterone)
    • Eggs are produced within the ovary and released into the abdominal cavity before being taken in by the Fallopian tube

    Ovarian Cycle

    • One egg is released each month during the ovarian cycle
    • If fertilization occurs, the second round of meiosis is triggered

    Fallopian Tube

    • Transports the egg towards the uterus
    • Site of fertilization
    • Cilia in the epithelial cells help push the egg towards the uterus

    Uterus

    • Has smooth muscle walls that can contract
    • Inner lining is the endometrium
    • Site of prenatal development, including implantation of the fertilized egg, embryonic development, and fetal development

    Cervix

    • Lower part of the uterus that extends into the vaginal canal
    • Dilates during childbirth
    • Contains a mucous plug during most parts of the menstrual cycle to protect reproductive structures and abdominal organs from pathogens

    Vagina

    • Muscular canal that accommodates the penis during sexual intercourse and receives sperm
    • Serves as the birth canal during childbirth
    • Contains ribbed structures that can expand and stretch
    • Sperm are typically deposited in the upper portion during sexual intercourse

    External Genitalia

    • Include the clitoris, labia, and vulva
    • Clitoris is important for female arousal and orgasm
    • Labia are folds of skin that cover the vaginal opening and urethra
    • Clitoris and labia become engorged with blood and secrete fluid during arousal

    Female Reproductive Tract

    • Ovaries produce eggs and release female sex steroids (estrogen and progesterone)
    • Eggs are produced within the ovary and released into the abdominal cavity before being taken in by the Fallopian tube

    Ovarian Cycle

    • One egg is released each month during the ovarian cycle
    • If fertilization occurs, the second round of meiosis is triggered

    Fallopian Tube

    • Transports the egg towards the uterus
    • Site of fertilization
    • Cilia in the epithelial cells help push the egg towards the uterus

    Uterus

    • Has smooth muscle walls that can contract
    • Inner lining is the endometrium
    • Site of prenatal development, including implantation of the fertilized egg, embryonic development, and fetal development

    Cervix

    • Lower part of the uterus that extends into the vaginal canal
    • Dilates during childbirth
    • Contains a mucous plug during most parts of the menstrual cycle to protect reproductive structures and abdominal organs from pathogens

    Vagina

    • Muscular canal that accommodates the penis during sexual intercourse and receives sperm
    • Serves as the birth canal during childbirth
    • Contains ribbed structures that can expand and stretch
    • Sperm are typically deposited in the upper portion during sexual intercourse

    External Genitalia

    • Include the clitoris, labia, and vulva
    • Clitoris is important for female arousal and orgasm
    • Labia are folds of skin that cover the vaginal opening and urethra
    • Clitoris and labia become engorged with blood and secrete fluid during arousal

    Journey of Sperm

    • Sperm travel from the epididymis through the vas deferens during ejaculation.
    • Vasectomy involves cutting or severing the vas deferens to prevent fertilization.

    Through the Male Reproductive Tract

    • Sperm exit the body through the urethra during sexual intercourse.
    • The vas deferens is the pathway for sperm to reach the urethra.

    Into the Female Reproductive Tract

    • Sperm are contained in semen, which includes secretions from the prostate, seminal vesicles, and bulbourethral gland.
    • Sperm are deposited in the upper portion of the vagina during sexual intercourse.

    Through the Female Reproductive Tract

    • The vagina's acidity is neutralized by semen's alkaline secretions.
    • Hormonal changes around ovulation reduce the vagina's acidity, increasing the chance of fertilization.
    • The cervix, normally blocked by a mucous plug, becomes thinner around ovulation, allowing sperm to pass through.
    • Uterine contractions and prostaglandins in semen aid sperm in traveling through the uterus.
    • Sperm must select the correct Fallopian tube, as only one will have the egg.

    Fertilization

    • Sperm become capacitated and ready to fertilize an egg as they swim upstream through the Fallopian tube.
    • Fertilization occurs in the Fallopian tube, not in the ovary.
    • The cilia in the Fallopian tube help push the fertilized egg towards the uterus.

    Implantation and Development

    • The fertilized egg implants in the uterus, where embryonic and fetal development occur.
    • Ectopic pregnancy occurs when the fertilized egg implants outside the uterus, which is dangerous and potentially fatal.

    Contraception Methods

    • Vasectomy is a contraception method that involves cutting or severing the vas deferens to prevent sperm from exiting.
    • Tubal ligation is a contraception method that involves tying or cauterizing the Fallopian tubes to prevent sperm from reaching the egg.

    Journey of Sperm

    • Sperm travel from the epididymis through the vas deferens during ejaculation.
    • Vasectomy involves cutting or severing the vas deferens to prevent fertilization.

    Through the Male Reproductive Tract

    • Sperm exit the body through the urethra during sexual intercourse.
    • The vas deferens is the pathway for sperm to reach the urethra.

    Into the Female Reproductive Tract

    • Sperm are contained in semen, which includes secretions from the prostate, seminal vesicles, and bulbourethral gland.
    • Sperm are deposited in the upper portion of the vagina during sexual intercourse.

    Through the Female Reproductive Tract

    • The vagina's acidity is neutralized by semen's alkaline secretions.
    • Hormonal changes around ovulation reduce the vagina's acidity, increasing the chance of fertilization.
    • The cervix, normally blocked by a mucous plug, becomes thinner around ovulation, allowing sperm to pass through.
    • Uterine contractions and prostaglandins in semen aid sperm in traveling through the uterus.
    • Sperm must select the correct Fallopian tube, as only one will have the egg.

    Fertilization

    • Sperm become capacitated and ready to fertilize an egg as they swim upstream through the Fallopian tube.
    • Fertilization occurs in the Fallopian tube, not in the ovary.
    • The cilia in the Fallopian tube help push the fertilized egg towards the uterus.

    Implantation and Development

    • The fertilized egg implants in the uterus, where embryonic and fetal development occur.
    • Ectopic pregnancy occurs when the fertilized egg implants outside the uterus, which is dangerous and potentially fatal.

    Contraception Methods

    • Vasectomy is a contraception method that involves cutting or severing the vas deferens to prevent sperm from exiting.
    • Tubal ligation is a contraception method that involves tying or cauterizing the Fallopian tubes to prevent sperm from reaching the egg.

    Hormonal Regulation of the Reproductive System

    • The reproductive system is controlled by the hypothalamic-anterior pituitary axis, which regulates hormone release from the testes and ovaries.
    • The hypothalamus stimulates the anterior pituitary gland, which in turn regulates hormone release.

    Fetal Development and Puberty

    • Hormone levels are low during fetal development, except for a brief period of masculinization in male fetuses.
    • Hormone levels decrease towards the end of gestation and remain low until puberty.
    • At puberty, GnRH release from the hypothalamus increases, stimulating FSH and LH production, which triggers testosterone and estrogen production.

    Puberty and Secondary Sex Characteristics

    • Increased hormone levels trigger the development of secondary sex characteristics, such as:
      • Deepening of the voice in males
      • Armpit and pubic hair growth in both sexes
      • Breast tissue development and fat deposition in females
    • Gamete production begins during puberty.

    Factors Affecting Puberty Onset

    • Body fat levels play a crucial role in puberty onset in females, with low body fat delaying puberty.
    • Historical changes in diet have led to earlier puberty onset, with girls now reaching menarche earlier than 100 years ago.
    • Endocrine disruptors in the environment, such as BPA, may be affecting puberty onset.

    Testosterone Production Regulation

    • The hypothalamus releases GnRH, which stimulates the anterior pituitary to release FSH and LH.
    • FSH acts on the testes to stimulate sperm production, while LH stimulates Leydig cells to release testosterone.
    • Testosterone promotes secondary male sex characteristics and sperm production, and has negative feedback effects on the anterior pituitary and hypothalamus to maintain steady hormone levels.

    Hormonal Regulation of the Reproductive System

    • The reproductive system is controlled by the hypothalamic-anterior pituitary axis, which regulates hormone release from the testes and ovaries.
    • The hypothalamus stimulates the anterior pituitary gland, which in turn regulates hormone release.

    Fetal Development and Puberty

    • Hormone levels are low during fetal development, except for a brief period of masculinization in male fetuses.
    • Hormone levels decrease towards the end of gestation and remain low until puberty.
    • At puberty, GnRH release from the hypothalamus increases, stimulating FSH and LH production, which triggers testosterone and estrogen production.

    Puberty and Secondary Sex Characteristics

    • Increased hormone levels trigger the development of secondary sex characteristics, such as:
      • Deepening of the voice in males
      • Armpit and pubic hair growth in both sexes
      • Breast tissue development and fat deposition in females
    • Gamete production begins during puberty.

    Factors Affecting Puberty Onset

    • Body fat levels play a crucial role in puberty onset in females, with low body fat delaying puberty.
    • Historical changes in diet have led to earlier puberty onset, with girls now reaching menarche earlier than 100 years ago.
    • Endocrine disruptors in the environment, such as BPA, may be affecting puberty onset.

    Testosterone Production Regulation

    • The hypothalamus releases GnRH, which stimulates the anterior pituitary to release FSH and LH.
    • FSH acts on the testes to stimulate sperm production, while LH stimulates Leydig cells to release testosterone.
    • Testosterone promotes secondary male sex characteristics and sperm production, and has negative feedback effects on the anterior pituitary and hypothalamus to maintain steady hormone levels.

    Female Reproductive Regulation

    • The hypothalamic-pituitary axis regulates female reproduction, involving GnRH, FSH, and LH hormones.
    • GnRH stimulates the anterior pituitary to release FSH and LH, which in turn regulate ovarian function.

    Ovarian Function

    • FSH stimulates follicle development in the ovaries.
    • LH triggers ovulation and the release of eggs from the ovary.
    • FSH and LH increase estrogen and progesterone levels, preparing the uterine lining for implantation and influencing female secondary sex characteristics.

    Hormone Regulation

    • Low levels of GnRH stimulate the release of FSH and LH.
    • Low-ish levels of estrogen and progesterone have negative feedback effects, preventing the release of FSH and LH.
    • High levels of estrogen and progesterone have positive feedback effects, leading to a surge in FSH and LH levels.

    Menstrual Cycle

    • The menstrual cycle is a 28-day cycle involving changes in the uterus, specifically the endometrial layer.
    • The cycle starts with menstruation, where the uterine lining is shed due to low estrogen and progesterone levels.
    • Estrogen and progesterone levels increase, causing the uterine lining to grow and thicken, preparing for implantation.

    Ovulation

    • Ovulation is triggered by a surge in LH levels, caused by high estrogen levels, around day 14 of the menstrual cycle.

    Post-Ovulation

    • The corpus luteum forms in the ovary after ovulation, producing estrogen and progesterone.
    • These hormones maintain the thickened uterine lining, preparing it for implantation.
    • As the corpus luteum regresses, estrogen and progesterone levels drop, and the uterine lining is shed, starting the menstrual cycle again.

    Contraceptives

    • Hormonal contraceptives work by maintaining low-ish levels of estrogen and progesterone, preventing ovulation and fertilization.
    • These contraceptives can thicken cervical mucus, blocking sperm entry, and keep the uterine lining thin, making it difficult for implantation to occur.
    • The emergency contraceptive is less effective than other forms of hormonal contraceptives, as it may not delay ovulation long enough to prevent fertilization.

    Female Reproductive Regulation

    • The hypothalamic-pituitary axis regulates female reproduction, involving GnRH, FSH, and LH hormones.
    • GnRH stimulates the anterior pituitary to release FSH and LH, which in turn regulate ovarian function.

    Ovarian Function

    • FSH stimulates follicle development in the ovaries.
    • LH triggers ovulation and the release of eggs from the ovary.
    • FSH and LH increase estrogen and progesterone levels, preparing the uterine lining for implantation and influencing female secondary sex characteristics.

    Hormone Regulation

    • Low levels of GnRH stimulate the release of FSH and LH.
    • Low-ish levels of estrogen and progesterone have negative feedback effects, preventing the release of FSH and LH.
    • High levels of estrogen and progesterone have positive feedback effects, leading to a surge in FSH and LH levels.

    Menstrual Cycle

    • The menstrual cycle is a 28-day cycle involving changes in the uterus, specifically the endometrial layer.
    • The cycle starts with menstruation, where the uterine lining is shed due to low estrogen and progesterone levels.
    • Estrogen and progesterone levels increase, causing the uterine lining to grow and thicken, preparing for implantation.

    Ovulation

    • Ovulation is triggered by a surge in LH levels, caused by high estrogen levels, around day 14 of the menstrual cycle.

    Post-Ovulation

    • The corpus luteum forms in the ovary after ovulation, producing estrogen and progesterone.
    • These hormones maintain the thickened uterine lining, preparing it for implantation.
    • As the corpus luteum regresses, estrogen and progesterone levels drop, and the uterine lining is shed, starting the menstrual cycle again.

    Contraceptives

    • Hormonal contraceptives work by maintaining low-ish levels of estrogen and progesterone, preventing ovulation and fertilization.
    • These contraceptives can thicken cervical mucus, blocking sperm entry, and keep the uterine lining thin, making it difficult for implantation to occur.
    • The emergency contraceptive is less effective than other forms of hormonal contraceptives, as it may not delay ovulation long enough to prevent fertilization.

    Human Development

    • Human development consists of prenatal and postnatal periods.

    Prenatal Period

    • Divided into pre-embryonic, embryonic, and fetal periods.

    Pre-Embryonic Period

    • Lasts for the first two weeks after fertilization.
    • Measured clinically from the last menstrual period (LMP), but this is not exactly accurate.
    • Fertilization occurs around day 14 of a 28-day menstrual cycle, resulting in a zygote.
    • Zygote undergoes mitosis, producing genetically identical cells, and begins moving down the Fallopian tube towards the uterus.

    Morula and Blastocyst Phases

    • Zygote divides and becomes a solid ball of cells called the morula.
    • Morula develops into a hollow ball of cells called the blastocyst.
    • Blastocyst phase has embryonic stem cells that can develop into different tissues.
    • Remaining cells develop into extra membranes, such as the amniotic sac.

    Implantation

    • Blastocyst reaches the uterus and implants into the uterine lining around day five.
    • Implantation lasts about five to 14 days after fertilization.
    • Embryo produces human chorionic gonadotropin (HCG) hormone to maintain pregnancy.
    • Placenta forms, allowing for exchange between the embryo and mother.
    • Three primary germ layers (endoderm, mesoderm, and ectoderm) form and differentiate into tissues.

    Embryonic Period

    • Lasts from three to eight weeks after fertilization.
    • Major organs begin to form, including the heart, lungs, digestive tract, brain, and limbs.
    • Embryo is still small, about an inch long.
    • Susceptible to environmental factors causing birth defects and chromosomal abnormalities.
    • Miscarriage common during this stage, with an estimated 33.3 to 50 percent of pregnancies failing to implant or miscarrying.

    Fetal Period

    • Begins at week nine and continues until birth.
    • Major organs continue to develop and grow.
    • Fetus still susceptible to certain environmental factors causing birth defects.
    • Fetus grows and develops into a full-sized baby by the end of this period.

    Birth Defects

    • Genetic or inherited conditions can cause birth defects, including chromosomal abnormalities or spontaneous mutations inherited from parents.

    Environmental Factors

    • High levels of radiation can cause birth defects.
    • Chemicals like alcohol can cause fetal alcohol syndrome, leading to behavioral problems, intellectual disability, heart defects, and digestive problems.
    • Accutane, a medication related to vitamin A, can cause birth defects affecting the brain, heart, and face, and can result in conditions like cleft palate.
    • Excessive intake of vitamin A can also cause birth defects.

    Nutritional Deficiencies

    • Inadequate dietary intake during pregnancy can result in birth defects.
    • Insufficient folic acid intake is linked to spina bifida.

    Infections

    • Zika virus infections can cause birth defects, including microcephaly and intellectual disability.
    • Toxoplasmosis infections, typically contracted through cat feces, can cause birth defects, including hydrocephaly and intellectual disability.

    Critical Periods

    • The timing and level of exposure to risk factors affect the likelihood of birth defects.
    • The embryonic period (3-8 weeks post-fertilization) is a critical time for development, and exposure to risk factors during this period can have a significant impact on the developing fetus.

    Sex Determination

    • Sex determination occurs in three levels: chromosomal, gonadal, and phenotypic sex.

    Chromosomal Sex

    • Determined by the set of sex chromosomes inherited during fertilization: XX (female) or XY (male).
    • Eggs can only carry X chromosomes, while sperm can carry either X or Y chromosomes.

    Gonadal Sex

    • Initially, the embryo has bipotential gonads that can develop into ovaries or testes.
    • The presence of a Y chromosome triggers the development of testes, while the absence of a Y chromosome leads to the development of ovaries.
    • The SRY gene on the Y chromosome triggers the development of testes.

    Phenotypic Sex

    • Determined by the appearance of the individual, including accessory structures and external genitalia.
    • Hormones, such as testosterone, play a crucial role in determining phenotypic sex.
    • Testosterone production by the testes masculinizes internal and external structures.
    • Absence of testosterone leads to the development of female structures.

    Intersex Conditions

    • Occur when the phenotypic sex does not match the chromosomal sex.
    • Examples:
      • 5-alpha-reductase deficiency: XY individual with female phenotype, but masculinization occurs at puberty.
      • Testicular feminizing syndrome: XY individual with testes, but cells can't respond to testosterone, leading to a female phenotype.
      • Adrenal hypersecretion: XX individual with masculinization of external genitalia due to excessive androgen production.

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    Learn about the process of reproduction, fertilization, and gametes. Understand how offspring are created and the role of sex cells in this process.

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