Questions and Answers
What role do Sertoli cells play in spermatogenesis?
During spermatogenesis, what does the golgi apparatus develop into?
In the process of oogenesis, what happens to the primary oocyte before birth?
What is the duration of the first meiotic division in spermatogenesis?
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What significant event occurs during spermiogenesis?
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What usually happens to the cytoplasm of spermatids during their development?
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What is the total duration of the spermatogenesis cycle?
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During prenatal maturation of oocytes, what type of cells surround the primary oocyte?
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What is the primary function of gametogenesis?
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Which of the following correctly identifies the beginning of spermatogenesis?
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What is the number of chromosomes in a secondary spermatocyte after the first meiotic division?
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What are the two main stages of spermatogenesis?
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What distinguishes spermatozoa from ova in terms of structure?
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What occurs during spermiogenesis?
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What is the total duration of spermatogenesis?
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What genetic implication can arise from dispermy during fertilization?
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What type of cell is formed when a primary oocyte resumes its first meiotic division before ovulation?
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What happens to the secondary oocyte at ovulation?
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During fertilization, what is the outcome of the secondary oocyte completing its second meiotic division?
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How many primary oocytes are present in a newborn female's ovaries?
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What is the maximum number of secondary oocytes that are typically expelled at ovulation during a female's reproductive life?
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In comparison between male and female gametes, which statement is true about the mature oocyte?
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What defines the prenatal period of intrauterine life?
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What occurs during the first week of prenatal development?
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What is the primary site for the process of capacitation?
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Which enzyme aids in the penetration of the corona radiata during fertilization?
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What occurs immediately after a sperm penetrates the zona pellucida?
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What is the lifespan of sperm in the female genital tract?
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During fertilization, which structure is formed when the nucleus of the sperm enlarges?
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How many sperm typically reach the site of fertilization out of the original deposited?
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What is the function of zona lysin during fertilization?
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What happens to the tail of the sperm after it fuses with the plasma membrane of the oocyte?
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Study Notes
Objectives of Human Embryology
- Understand gametogenesis: formation of male and female gametes.
- Outline spermatogenesis stages: multiplication of spermatogonia, meiotic divisions, and spermiogenesis.
- Explain oogenesis stages: prenatal and postnatal maturation of oocytes.
- Identify structural differences between spermatozoa and ova: cytoplasm content, motility, and chromosomal composition.
- Describe fertilization events: capacitation, acrosome reaction, formation of the zygote.
- Recognize common fertilization errors: dispermy, superfecundation, superfetation, and their genetic implications.
- Analyze clinical problems related to fertility, genetic disorders, and embryonic development through knowledge of gametogenesis.
Gametogenesis
- Definition: Formation of gametes occurs solely in gonads.
- Key features: Preparation for fertilization and reduction of chromosome number to haploid (23 chromosomes).
- Two processes:
- Spermatogenesis: Formation of sperm in testis.
- Oogenesis: Formation of ovum in ovary.
Spermatogenesis
- Definition: Maturation of sperm occurs in seminiferous tubules of the testis.
- Duration: Approximately 64 days; begins at puberty (ages 13-16).
Stages of Spermatogenesis
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Spermatogenesis Proper:
- Spermatogonia undergo mitosis to produce more spermatogonia.
- Spermatogonia develop into primary spermatocytes.
- Primary spermatocytes undergo first meiotic division, yielding secondary spermatocytes (22 + X or 22 + Y).
- Secondary spermatocytes undergo second meiotic division into spermatids.
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Spermiogenesis:
- Morphological transformation of spermatids into mature sperm.
- Key changes:
- Enlargement of nucleus forms sperm head.
- Golgi apparatus forms the acrosomal cap.
- Mitochondria and centrioles migrate to form tail and spiral sheath.
- Most cytoplasm is eliminated.
- Cell membrane encloses the sperm.
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Subdivided into four phases:
- Mitosis: 16 days.
- First meiosis: 24 days.
- Second meiosis: A few hours.
- Spermiogenesis: 24 days.
Oogenesis
- Definition: Process of mature ovum formation in the outer cortex of the ovary.
Stages of Oogenesis
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Prenatal Maturation:
- Oogonia contain 22 pairs of chromosomes and X chromosomes.
- Oogonia grow into primary oocytes, surrounded by primordial follicles.
- Primary oocytes start first meiotic division before birth but pause in prophase until puberty.
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Postnatal Maturation:
- At puberty, 5-12 primary oocytes resume meiotic division, producing one large secondary oocyte and a small polar body.
- At ovulation, the secondary oocyte is arrested in metaphase of the second meiotic division.
- Upon fertilization, completes second meiotic division yielding a mature ovum and a second polar body.
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Statistics:
- Newborn females have 2 million primary oocytes; only about 480 become secondary oocytes expelled during reproductive years.
Comparison Between Male and Female Gametes
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Female Gametes:
- No primary oocytes after birth, only one type of ovum (22 + X).
- Mature oocyte is a massive, immotile cell containing yolk for nutrition.
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Male Gametes:
- Continuous production of primary spermatocytes after puberty with two types of sperm (22 + X and 22 + Y).
- Sperm are highly motile with minimal cytoplasm.
Prenatal Periods (Intrauterine Life)
- Definition: Time from fertilization to delivery.
- Duration: Approximately 280 days (10 lunar months); 266 days from fertilization.
Phases
- Germinal Phase: First 3 weeks after fertilization.
- Embryonic Phase: 4th to 8th weeks of development.
- Fetal Phase: From the 9th week until birth.
Fertilization Process
- Definition: Union of sperm and ovum to form zygote; typically occurs in the ampulla of the uterine tube.
- Process:
- 200-300 million sperm deposited; only 200 reach the fertilization site.
- One sperm fertilizes the ovum, assisted by other sperm enzymes digesting surrounding membranes.
- Sperm can survive in female tract for up to two days; ovum viable for 12-24 hours post-ovulation.
Capacitation and Acrosome Reaction
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Capacitation:
- Removes seminal plasma proteins, takes place in the cervix, lasts about 7 hours.
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Acrosome Reaction:
- Occurs near the oocyte, releasing enzymes (hyaluronidase, trypsin-like substances) for penetration.
Fertilization Phases
- Passage through corona radiata via hyaluronidase.
- Penetration of zona pellucida.
- Zona reaction prevents multiple sperm entry.
- Fusion of plasma membranes; sperm head and tail enter the oocyte.
- Formation of male pronucleus; degeneration of sperm tail.
- Union of two pronuclei for mitotic division preparation.
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Description
Test your knowledge on human embryology with this quiz focusing on gametogenesis. Explore the stages of spermatogenesis and oogenesis, including the formation and maturation of male and female gametes. Challenge yourself to understand the key processes involved in human reproduction.
