Reproduction | Jamb Biology

Jamb(UTME) tutorial on asexual reproduction

Sexual Reproduction

1. Definition: Sexual reproduction involves the combination of genetic material from two parents.
2. Gametes: Male (sperm or pollen) and female (egg or ovule) reproductive cells.
3. Fusion: Male and female gametes fuse during fertilization, forming a zygote.
4. Examples: Occurs in humans, flowering plants, and most animals.
5. Genetic Diversity: Produces offspring with unique genetic combinations.
6. Advantages: Enhances adaptability to environmental changes.
7. Disadvantages: Slower process, requires more energy, and depends on finding a mate.
8. Offspring Variability: Increases the chances of survival against diseases and environmental challenges.
9. Zygote Development: The zygote divides and develops into a multicellular organism.
10. Evolution: Sexual reproduction drives evolution by introducing genetic variation.
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Asexual Reproduction

11. Definition: Offspring are produced from a single parent without gametes.
12. Cloning: Offspring are genetically identical to the parent.
13. Examples: Seen in bacteria, fungi, and some plants like Bryophyllum.
14. Methods: Includes fission, budding, fragmentation, and vegetative propagation.
15. Advantages: Quick reproduction and no need for a mate.
16. Disadvantages: Lack of genetic diversity reduces adaptability.
17. Environmental Suitability: Ideal for stable environments.
18. Rapid Growth: Enables exponential population increase under favorable conditions.
19. Survival Mechanism: Ensures species continuity during resource abundance.
20. Common in Simple Organisms: Found in unicellular organisms and some multicellular plants.
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Fission (e.g., Paramecium)

21. Definition: The division of a single organism into two identical daughter cells.
22. Binary Fission: Common in unicellular organisms like Paramecium.
23. Process:
    • The nucleus divides through mitosis.
    • The cytoplasm divides, forming two new cells.
24. Rapid Multiplication: Ensures a quick increase in population.
25. Adaptation: Ideal for resource-rich environments.
    
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Budding (e.g., Yeast)

26. Definition: A new organism develops as a bud from the parent organism.
27. Process in Yeast:
    • A bud forms on the parent cell.
    • The nucleus divides, and one nucleus moves into the bud.
    • The bud detaches to form an independent organism.
28. Examples: Seen in yeast, Hydra, and some plants like Bryophyllum.
29. Advantages: Produces multiple offspring rapidly.
30. Significance: Helps maintain population size in stable environments.
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Natural Vegetative Propagation

31. Definition: Reproduction in plants using naturally occurring structures like roots, stems, or leaves.
32. Examples:
    • Tubers: Potato produces new plants from underground structures.
    • Bulbs: Onion and garlic propagate through bulbs.
    • Runners: Strawberries and grasses grow from horizontal stems.
33. Adaptation: Ensures survival by producing genetically identical plants.
34. Agricultural Importance: Maintains desirable traits in crops.
35. Speed: Faster and more efficient than seed propagation.
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Artificial Vegetative Propagation

36. Definition: Human-assisted propagation methods to reproduce plants.
37. Techniques:
    • Cuttings: Stems or leaves are planted to grow new plants (e.g., rose).
    • Layering: A branch is bent and covered with soil to induce rooting (e.g., jasmine).
    • Grafting: A desired plant part is attached to a rootstock (e.g., mango).
38. Applications:
    • Widely used for fruits like apple and citrus.
    • Enhances the production of ornamental plants.
39. Advantages: Combines desirable traits and ensures uniformity.
40. Significance: Essential for modern horticulture and crop improvement.
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Parts of a Flower and Their Functions

41. Sepals: Protect the flower bud before it blooms.
42. Petals: Attract pollinators with their colors and fragrance.
43. Stamens: Male reproductive part; produces pollen.
44. Carpels (Pistils): Female reproductive part; contains ovary, style, and stigma.
45. Receptacle: Supports the floral organs.
46. Ovules: Contain the egg cells.
47. Pollen Grains: Contain male gametes for fertilization.
48. Nectaries: Produce nectar to attract pollinators.
    
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Reproductive Process in Flowers

49. Pollination: Transfer of pollen from anther to stigma.
50. Self-Pollination: Occurs within the same flower.
51. Cross-Pollination: Pollen is transferred between flowers.
52. Fertilization: Male gametes from pollen fuse with egg cells in ovules.
53. Seed Formation: Fertilized ovules develop into seeds.
54. Fruit Formation: Ovary develops into fruit to protect seeds.
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Advantages of Cross-Pollination

55. Genetic Diversity: Produces varied offspring.
56. Increased Adaptability: Offspring can better survive environmental changes.
57. Improved Crop Yield: Enhances fruit and seed production.
58. Disease Resistance: Genetic variation reduces susceptibility to diseases.
    
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Placentation and Fruit Types

59. Placentation: Arrangement of ovules in the ovary.
60. Marginal Placentation: Ovules along one margin (e.g., pea).
61. Axile Placentation: Ovules around a central axis (e.g., tomato).
62. Parietal Placentation: Ovules attached to the ovary wall (e.g., cucumber).
63. Basal Placentation: Ovules at the base of the ovary (e.g., sunflower).
    
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Fruit Types

64. Simple Fruits: Develop from one ovary (e.g., mango).
65. Aggregate Fruits: Develop from multiple ovaries of one flower (e.g., strawberry).
66. Multiple Fruits: Formed from ovaries of multiple flowers (e.g., pineapple).
67. Succulent Fruits: Fleshy fruits like watermelon and orange.
    
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Pollination and Fertilization

68. Pollination: Facilitates the transfer of male gametes to female gametes.
69. Types of Pollination:
    • Insect Pollination: Flowers are colorful and produce nectar.
    • Wind Pollination: Lightweight pollen grains are carried by the wind.
70. Fertilization: Fusion of male and female gametes forms a zygote.
71. Seed Formation: Zygote develops into an embryo within the seed.
72. Fruit Formation: The ovary develops into a fruit to protect seeds.
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Products of Sexual Reproduction

73. Zygote: The first cell of the new organism.
74. Seed: Contains the embryo and stores food for early growth.
75. Fruit: Protects seeds and aids in their dispersal.
76. Offspring: Ensures the survival of species through genetic variation.
    
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Comparison: Asexual vs. Sexual Reproduction

77. Asexual Reproduction:
    • Involves one parent.
    • Produces identical offspring.
78. Sexual Reproduction:
    • Involves two parents.
    • Produces genetically diverse offspring.
79. Advantages:
    • Asexual: Quick and efficient.
    • Sexual: Genetic diversity ensures adaptability.
      
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Applications in Agriculture

80. Cross-Pollination: Improves crop resilience and productivity.
81. Grafting: Combines desirable traits for better yields.
82. Vegetative Propagation: Ensures uniform crop production.
    
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Jamb(UTME) tutorial on reproduction in mammals

Structures and Functions of Male Reproductive Organs

1. Testes: Produce sperm and testosterone, the male sex hormone.
2. Epididymis: Stores and matures sperm cells.
3. Vas Deferens: Transports sperm from the epididymis to the urethra.
4. Prostate Gland: Produces a fluid that nourishes and protects sperm.
5. Seminal Vesicles: Add a nutrient-rich fluid to semen to energize sperm.
6. Penis: Delivers sperm into the female reproductive tract during mating.
7. Scrotum: Holds and regulates the temperature of the testes for optimal sperm production.
8. Urethra: Common pathway for the excretion of urine and ejaculation of semen.
9. Structure-Function Relationship: The compact and specialized structure of male organs ensures efficient sperm production and delivery.
10. Hormonal Control: Testosterone regulates the development of secondary sexual characteristics and sperm production.
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Structures and Functions of Female Reproductive Organs

11. Ovaries: Produce eggs (ova) and hormones like estrogen and progesterone.
12. Fallopian Tubes: Transport the egg from the ovary to the uterus; site of fertilization.
13. Uterus: Supports and nourishes the developing embryo and fetus.
14. Cervix: A muscular opening that connects the uterus to the vagina, facilitating sperm entry and childbirth.
15. Vagina: Receives sperm during mating and serves as the birth canal.
16. Endometrium: Lining of the uterus that thickens during the menstrual cycle to prepare for implantation.
17. Clitoris: A sensitive structure involved in female sexual arousal.
18. Hormonal Control: Estrogen and progesterone regulate the menstrual cycle and pregnancy.
19. Structure-Function Relationship: The design of female organs supports gamete production, fertilization, implantation, and fetal development.
20. Special Adaptations: Elasticity of the uterus and vagina aids childbirth.
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Fertilization and Development (Fusion of Gametes)

21. Definition of Fertilization: The union of a sperm and an egg to form a zygote.
22. Process:
    • Sperm travels through the female reproductive tract to reach the egg in the fallopian tube.
    • The sperm penetrates the egg's protective layers using enzymes.
    • Fusion of sperm and egg nuclei forms a diploid zygote.
23. Significance: Fertilization restores the diploid chromosome number and initiates embryonic development.
24. Early Development:
    • Zygote undergoes mitotic divisions (cleavage).
    • Forms a blastocyst that implants in the uterine wall.
25. Embryonic Development:
    • Differentiation of cells leads to organ formation.
    • Fetus grows within the uterus, supported by the placenta.
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Differences Between Male and Female Reproductive Organs

26. Gamete Production:
    • Males produce millions of small, motile sperm continuously.
    • Females produce a limited number of large, immotile eggs.
27. External vs. Internal Organs:
    • Male organs are primarily external (penis, scrotum).
    • Female organs are internal (ovaries, uterus).
28. Hormonal Regulation:
    • Males rely on testosterone.
    • Females depend on estrogen and progesterone.
29. Role in Reproduction:
    • Males deliver sperm.
    • Females provide the environment for fertilization, implantation, and development.
30. Structural Adaptations:
    • Males have structures designed for efficient sperm delivery.
    • Females have structures adapted for nurturing and birthing offspring.
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Effects of Maternal Health and Lifestyle on Embryonic Development

31. Nutrition: Poor maternal nutrition can lead to fetal malformations, low birth weight, or developmental delays.
32. Health: Chronic illnesses like diabetes and hypertension in mothers may complicate pregnancy.
33. Drug Use: Indiscriminate use of drugs or alcohol can cause birth defects or developmental issues (e.g., Fetal Alcohol Syndrome).
34. Smoking: Increases the risk of premature birth, low birth weight, and respiratory problems in newborns.
35. Prenatal Care: Ensures the mother’s health is monitored, reducing risks to the fetus.
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Modern Methods of Regulating Reproduction

36. In Vitro Fertilization (IVF):
    • Fertilization occurs outside the body in a lab.
    • The fertilized egg is implanted in the uterus.
    • Used for couples with fertility issues.
37. Birth Control Pills:
    • Hormonal pills prevent ovulation.
    • Highly effective when used correctly.
38. Barrier Methods:
    • Condoms and diaphragms block sperm from reaching the egg.
39. Intrauterine Devices (IUDs):
    • Inserted into the uterus to prevent implantation.
    • Effective for long-term contraception.
40. Sterilization:
    • Vasectomy: Cutting the vas deferens in males.
    • Tubal Ligation: Blocking the fallopian tubes in females.
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Relation of Structure and Function to Offspring Production

41. Male Structures:
    • Testes produce motile sperm capable of reaching the egg.
    • The scrotum maintains an optimal temperature for sperm production.
42. Female Structures:
    • The uterus provides a protective environment for fetal growth.
    • The fallopian tube facilitates fertilization.
43. Adaptations for Fertilization:
    • The sperm’s streamlined shape allows efficient movement.
    • The egg’s cytoplasm provides nutrients for early development.
44. Placental Function:
    • The placenta facilitates nutrient and oxygen exchange between mother and fetus.
45. Hormonal Support:
    • Progesterone maintains the uterine lining during pregnancy.
      
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Fertilization and Development

46. Gamete Fusion:
    • Sperm binds to receptors on the egg’s surface.
    • Enzymes allow the sperm to penetrate the egg.
    • Genetic material combines to form a zygote.
47. Blastocyst Formation:
    • The zygote divides into a multicellular structure.
    • The blastocyst implants in the uterine lining.
48. Embryo Growth:
    • The heart begins to beat by week 4.
    • Major organs start forming by the second trimester.
49. Fetal Development:
    • Rapid growth occurs in the third trimester.
    • The fetus gains weight and prepares for birth.
50. Birth Process:
    • Hormones like oxytocin trigger labor.
    • The cervix dilates, and the baby is delivered through the birth canal.
      
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Structures and Functions of Male Reproductive Organs

1. Testes: The primary male reproductive organs located in the scrotum. They have two main functions:
   • Sperm Production (Spermatogenesis): Occurs in the seminiferous tubules, where diploid cells undergo meiosis to produce haploid sperm cells.
   • Hormone Secretion: Produce testosterone, which is crucial for the development of male secondary sexual characteristics (e.g., facial hair, deepening voice) and the regulation of libido and spermatogenesis.
2. Epididymis: A long, coiled tube sitting atop each testis where sperm mature and are stored.
   • Function: Sperm gain motility and the ability to fertilize an egg as they pass through the epididymis over a period of about 2 weeks.
3. Vas Deferens (Ductus Deferens): A muscular tube that transports mature sperm from the epididymis to the urethra in preparation for ejaculation.
   • Function: Propels sperm using peristaltic contractions during ejaculation.
4. Prostate Gland: A walnut-sized gland located below the bladder surrounding the urethra.
   • Function: Produces a slightly alkaline fluid that makes up part of semen, enhancing sperm motility and longevity by neutralizing the acidic environment of the female reproductive tract.
5. Seminal Vesicles: Paired glands that secrete a fluid rich in fructose, prostaglandins, and proteins.
   • Function: The fructose provides energy for sperm, while prostaglandins may help widen the cervix and promote sperm movement.
6. Penis: The external male organ composed of erectile tissue.
   • Function: Delivers semen into the female reproductive tract during intercourse and serves as a conduit for urine excretion.
7. Scrotum: A pouch of skin containing the testes.
   • Function: Regulates the temperature of the testes, keeping them slightly cooler than body temperature, which is essential for viable sperm production.
8. Urethra: A tube that runs through the penis.
   • Function: Carries urine from the bladder and semen from the reproductive ducts to the outside of the body, but not simultaneously.
9. Bulbourethral (Cowper's) Glands: Small glands below the prostate.
   • Function: Secrete a pre-ejaculatory fluid that lubricates the urethra and neutralizes any acidic urine residues.
10. Hormonal Control:
    • Hypothalamus: Releases Gonadotropin-releasing hormone (GnRH), stimulating the pituitary gland.
    • Pituitary Gland: Secretes Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH).
      • LH: Stimulates testosterone production in the Leydig cells of the testes.
      • FSH: Along with testosterone, stimulates spermatogenesis in the seminiferous tubules.
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Structures and Functions of Female Reproductive Organs

11. Ovaries: The primary female reproductive organs located on either side of the uterus.
    • Function:
      • Oogenesis: Produce eggs (ova) through meiosis.
      • Hormone Secretion: Produce estrogen and progesterone, regulating the menstrual cycle and supporting pregnancy.
12. Fallopian Tubes (Oviducts): Tubes connecting the ovaries to the uterus.
    • Function:
      • Egg Transport: Cilia and muscular contractions move the egg toward the uterus.
      • Site of Fertilization: Typically occurs in the ampulla region of the tube.
13. Uterus: A muscular organ where the fertilized egg implants and develops into a fetus.
    • Structure:
      • Endometrium: The inner lining that thickens in preparation for pregnancy.
      • Myometrium: The muscular layer that contracts during labor.
14. Cervix: The lower part of the uterus opening into the vagina.
    • Function:
      • Gateway: Allows flow of menstrual blood out and directs sperm into the uterus.
      • Mucus Production: Changes in mucus consistency facilitate or prevent sperm entry depending on the menstrual cycle phase.
15. Vagina: A muscular canal leading from the cervix to the outside of the body.
    • Function:
      • Birth Canal: Passageway for childbirth.
      • Intercourse: Receives the penis during sexual activity.
      • Menstrual Flow: Serves as an exit for menstrual blood.
16. External Genitalia (Vulva):
    • Labia Majora and Minora: Protect internal reproductive organs.
    • Clitoris: Contains erectile tissue and nerve endings; plays a role in sexual arousal.
17. Breasts (Mammary Glands):
    • Function: Produce and secrete milk to nourish the newborn after childbirth.
18. Hormonal Control:
    • Hypothalamus: Releases GnRH.
    • Pituitary Gland: Secretes FSH and LH.
      • FSH: Stimulates follicle development in the ovaries.
      • LH: Triggers ovulation and supports the formation of the corpus luteum, which secretes progesterone.
19. Menstrual Cycle Phases:
    • Follicular Phase: Follicle matures; estrogen levels rise.
    • Ovulation: Release of the mature egg around day 14.
    • Luteal Phase: Corpus luteum forms; progesterone maintains the endometrium.
    • Menstruation: Shedding of the endometrial lining if no fertilization occurs.
20. Structural Adaptations:
    • Elasticity: The uterus and vagina can expand significantly to accommodate a growing fetus and childbirth.
    • Cervical Mucus: Changes consistency to either facilitate or block sperm entry based on fertility signals.
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Fertilization and Development (Fusion of Gametes)

21. Fertilization Process:
    • Capacitation: Sperm undergo biochemical changes in the female reproductive tract to become capable of fertilizing an egg.
    • Acrosome Reaction: Enzymes from the sperm's acrosome digest the egg's protective layers (zona pellucida).
    • Penetration: Sperm nucleus enters the egg cytoplasm.
    • Zygote Formation: Fusion of male and female nuclei restores the diploid chromosome number.
22. Significance of Fertilization:
    • Genetic Combination: Offspring receive half of their genetic material from each parent, promoting genetic diversity.
    • Activation of Development: Triggers metabolic changes in the egg, initiating embryogenesis.
23. Early Development:
    • Cleavage: Rapid cell divisions without growth, forming a morula.
    • Blastocyst Formation: Cells differentiate into an inner cell mass (embryo) and outer trophoblast (placenta precursor).
    • Implantation: The blastocyst embeds into the uterine lining about 6-7 days after fertilization.
24. Embryonic Development:
    • Gastrulation: Formation of three germ layers (ectoderm, mesoderm, endoderm), which give rise to all tissues and organs.
    • Organogenesis: Development of organs from the germ layers.
    • Critical Periods: Certain stages where the embryo is highly sensitive to environmental factors and teratogens.
25. Fetal Development:
    • Growth: From the 9th week to birth, the fetus grows in size and weight.
    • Maturation: Organs develop and become functional.
    • Viability: By the end of the second trimester, the fetus may survive outside the womb with medical support.
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Differences Between Male and Female Reproductive Organs

26. Location:
    • Male Organs: Primarily external (penis, scrotum) and internal (testes located in the scrotum but outside the pelvic cavity).
    • Female Organs: Primarily internal within the pelvic cavity (ovaries, uterus, fallopian tubes).
27. Gamete Production:
    • Males: Continuous production of sperm from puberty throughout life.
    • Females: Born with a finite number of immature eggs; one matures and is released typically each menstrual cycle.
28. Hormonal Differences:
    • Male Hormones: Testosterone is the primary androgen.
    • Female Hormones: Estrogen and progesterone regulate the menstrual cycle and pregnancy.
29. Reproductive Ducts:
    • Males: Vas deferens, ejaculatory ducts, urethra.
    • Females: Fallopian tubes, uterus, vagina.
30. Reproductive Functions:
    • Males: Produce and deliver sperm.
    • Females: Produce eggs, provide site for fertilization, support fetal development, and enable childbirth.
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Effects of Maternal Health, Nutrition, and Drug Use on Embryonic Development

31. Maternal Health:
    • Chronic Conditions: Diabetes, hypertension, and infections can affect fetal development.
    • Prenatal Care: Regular medical check-ups are essential for monitoring fetal health and addressing complications early.
32. Nutrition:
    • Balanced Diet: Adequate intake of proteins, vitamins, and minerals supports fetal growth.
    • Folic Acid: Essential to prevent neural tube defects.
    • Iron and Calcium: Necessary for blood production and bone development.
33. Indiscriminate Drug Use:
    • Prescription Medications: Some drugs can cross the placenta and harm the fetus; always consult a healthcare provider.
    • Alcohol and Tobacco: Can lead to fetal alcohol spectrum disorders, low birth weight, and developmental delays.
    • Illicit Drugs: Associated with miscarriage, premature birth, and withdrawal symptoms in newborns.
34. Environmental Exposures:
    • Teratogens: Substances that cause birth defects (e.g., certain chemicals, radiation).
    • Avoidance: Pregnant women should avoid exposure to harmful substances.
35. Lifestyle Factors:
    • Stress Management: High stress can affect fetal development.
    • Exercise: Moderate physical activity is beneficial unless contraindicated.
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Modern Methods of Regulating Reproduction

36. In Vitro Fertilization (IVF):
    • Process:
      • Ovarian Stimulation: Hormones stimulate multiple eggs to mature.
      • Egg Retrieval: Eggs are collected from the ovaries using a minor surgical procedure.
      • Fertilization: Eggs are combined with sperm in a lab dish.
      • Embryo Transfer: One or more embryos are placed into the uterus.
    • Applications: Helps couples with infertility due to blocked fallopian tubes, low sperm count, or unexplained infertility.
37. Birth Control Methods:
    • Hormonal Methods: Pills, patches, injections, and implants release hormones to prevent ovulation.
    • Barrier Methods: Condoms, diaphragms, and cervical caps prevent sperm from reaching the egg.
    • Intrauterine Devices (IUDs): T-shaped devices inserted into the uterus to prevent fertilization or implantation.
38. Emergency Contraception:
    • Morning-After Pill: High-dose hormones taken shortly after unprotected intercourse to prevent ovulation or implantation.
    • Copper IUD: Can be used as emergency contraception if inserted within five days.
39. Sterilization Procedures:
    • Vasectomy: Surgical cutting or blocking of the vas deferens in males, preventing sperm from entering semen.
    • Tubal Ligation: Surgical procedure to block or cut the fallopian tubes in females, preventing eggs from reaching the uterus.
40. Assisted Reproductive Technologies (ART):
    • Intracytoplasmic Sperm Injection (ICSI): A single sperm is injected directly into an egg.
    • Surrogacy: Another woman carries the pregnancy for individuals unable to do so.
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Relation of Structure and Function to Offspring Production

41. Sperm Cell Structure:
    • Head: Contains the nucleus with genetic material and is covered by the acrosome, which has enzymes to penetrate the egg.
    • Midpiece: Packed with mitochondria to provide energy for movement.
    • Tail (Flagellum): Propels the sperm towards the egg.
42. Egg Cell Structure:
    • Cytoplasm: Rich in nutrients to support the early stages of development.
    • Zona Pellucida: A glycoprotein layer surrounding the plasma membrane, involved in sperm binding and preventing polyspermy.
43. Placenta:
    • Function: Facilitates nutrient and gas exchange between mother and fetus.
    • Hormone Production: Secretes hormones like hCG, progesterone, and estrogen to maintain pregnancy.
44. Amniotic Sac and Fluid:
    • Function: Protects the fetus from mechanical shocks, prevents dehydration, and allows free movement for musculoskeletal development.
45. Umbilical Cord:
    • Structure: Contains two arteries and one vein within a protective jelly-like substance (Wharton's jelly).
    • Function: Connects the fetus to the placenta, transporting oxygenated blood and nutrients to the fetus and carrying waste products away.
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Fertilization and Development

46. Embryogenesis:
    • Formation of Body Plan: Establishment of the basic body axes (head-tail, back-front, left-right).
    • Neurulation: Development of the neural tube, which becomes the central nervous system.
47. Fetal Circulation:
    • Unique Pathways: Presence of shunts like the foramen ovale and ductus arteriosus to bypass non-functional fetal lungs.
    • Oxygenation: Oxygen and nutrients come from maternal blood via the placenta.
48. Maternal-Fetal Interface:
    • Immune Considerations: The fetus is genetically distinct; mechanisms prevent maternal immune rejection.
    • Nutrient Transfer: Active and passive transport mechanisms ensure the fetus receives necessary substances.
49. Labor and Delivery:
    • Hormonal Triggers: Increase in oxytocin and prostaglandins initiate labor.
    • Stages:
      • First Stage: Onset of contractions to full cervical dilation.
      • Second Stage: Delivery of the baby.
      • Third Stage: Delivery of the placenta.
50. Postnatal Adaptations:
    • Respiratory Transition: First breath inflates the lungs; pulmonary circulation increases.
    • Closure of Fetal Shunts: Foramen ovale and ductus arteriosus close, redirecting blood flow.

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