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Questions and Answers
What is the role of the SRY protein in sexual organs development?
What is the role of the SRY protein in sexual organs development?
During which stage of development do germ cells migrate from the yolk sac to the genital ridge?
During which stage of development do germ cells migrate from the yolk sac to the genital ridge?
What is the function of the corona radiata in relation to the ovum?
What is the function of the corona radiata in relation to the ovum?
What would happen if all fertilized eggs developed into females?
What would happen if all fertilized eggs developed into females?
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At what stage does the formation of a placenta occur during human reproduction?
At what stage does the formation of a placenta occur during human reproduction?
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When does folliculogenesis mainly occur within the female reproductive system?
When does folliculogenesis mainly occur within the female reproductive system?
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What is the primary function of Leydig cells during male reproductive system development?
What is the primary function of Leydig cells during male reproductive system development?
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Which of the following correctly describes the process of oogenesis in the female fetus?
Which of the following correctly describes the process of oogenesis in the female fetus?
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In the absence of the SRY gene, what happens to the bipotential gonads during development?
In the absence of the SRY gene, what happens to the bipotential gonads during development?
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What is the primary function of spermatogonia during spermatogenesis?
What is the primary function of spermatogonia during spermatogenesis?
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What is the primary cause of cryptorchidism, or failure of the testes to descend?
What is the primary cause of cryptorchidism, or failure of the testes to descend?
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What is the primary function of primordial follicles that form during oogenesis in the female fetus?
What is the primary function of primordial follicles that form during oogenesis in the female fetus?
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At what stage of embryonic development does the number of germ cells reach its peak?
At what stage of embryonic development does the number of germ cells reach its peak?
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What event precedes the phenotypic changes associated with puberty?
What event precedes the phenotypic changes associated with puberty?
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Which of the following is the correct sequence of events during the onset of puberty?
Which of the following is the correct sequence of events during the onset of puberty?
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Which of the following statements about folliculogenesis is true?
Which of the following statements about folliculogenesis is true?
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During which stage of embryonic development do most oogonia die, while the remaining oogonia enter the first meiotic division?
During which stage of embryonic development do most oogonia die, while the remaining oogonia enter the first meiotic division?
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What is the term used to describe the cells that result from the remaining oogonia entering the first meiotic division?
What is the term used to describe the cells that result from the remaining oogonia entering the first meiotic division?
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Which process is directly stimulated by the release of testosterone during puberty?
Which process is directly stimulated by the release of testosterone during puberty?
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What is the primary function of folliculogenesis?
What is the primary function of folliculogenesis?
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Which of the following is NOT a secondary sex characteristic associated with the release of testosterone during puberty?
Which of the following is NOT a secondary sex characteristic associated with the release of testosterone during puberty?
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During puberty, what change occurs in the sensitivity of the hypothalamus and pituitary to negative feedback signals from testosterone and estrogen?
During puberty, what change occurs in the sensitivity of the hypothalamus and pituitary to negative feedback signals from testosterone and estrogen?
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Which of the following is NOT a secondary sex characteristic associated with the release of estrogen during puberty?
Which of the following is NOT a secondary sex characteristic associated with the release of estrogen during puberty?
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According to the Tanner stages of puberty, which of the following occurs during the later stages?
According to the Tanner stages of puberty, which of the following occurs during the later stages?
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What role does the Leptin hormone play in determining menarche?
What role does the Leptin hormone play in determining menarche?
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Which of the following is NOT a factor affecting puberty onset?
Which of the following is NOT a factor affecting puberty onset?
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In spermatogenesis, what do the Sertoli cells stimulate the production of?
In spermatogenesis, what do the Sertoli cells stimulate the production of?
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What is the primary function of FSH in males?
What is the primary function of FSH in males?
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Which part of the male reproductive system secretes testosterone?
Which part of the male reproductive system secretes testosterone?
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How many chromosomes do secondary spermatocytes have as they undergo the second meiotic division?
How many chromosomes do secondary spermatocytes have as they undergo the second meiotic division?
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Study Notes
Factors Affecting Puberty Onset
- Genetics, environment, and psychological stress affect the onset of puberty
- Better nutrition has led to a decrease in the age of menarche in girls in the US
- There is a link between puberty onset and stored fat, especially in girls but also present in both sexes
- Leptin hormone plays a role in determining menarche
- Delay in puberty onset can occur in lean and highly active girls, such as gymnasts
Male Reproductive System
Hormonal Control
- Hypothalamus secretes Gonadotropin-releasing hormone (GnRH)
- Anterior pituitary secretes FSH and LH
- FSH stimulates Sertoli cells to secrete Androgen Binding Protein (ABP) and inhibin
- LH causes interstitial cells to secrete testosterone
- ABP and testosterone stimulate spermatogenesis
- Negative feedback control occurs through increased testosterone and inhibin
Anatomy
- Gonads, ducts, sex glands, and supporting structures
- Functions of various parts:
- Penis
- Testis
- Epididymis
- Scrotum
- Prostate
- Seminal vesicle
- Urethra
Spermatogenesis
- Sperm forming cells go through two meiotic divisions
- Each of four spermatids develop into a sperm
- Second meiosis division gives four spermatids, each with 23 single-stranded chromosomes
- First meiosis division gives two secondary spermatocytes, each with 23 chromosomes that become double-stranded
- Testosterone release leads to spermatogenesis
Effects of Hormone Release
- Penis and scrotum grow
- Facial hair grows
- Larynx elongates, leading to a lowering of the voice
- Shoulders broaden
- Body, armpit, and pubic hair grow
- Musculature increases body-wide
Female Reproductive System
Hormone Release
- Estrogen release leads to:
- Breast development and maturation
- Hips broadening
- Pubic hair growth
- Folliculogenesis (process of growing and developing ovarian follicles in the ovary)
Human Reproductive System
- Essential features of human reproduction:
- Liberation of an ovum at a specific time
- Internal fertilization of the ovum by spermatozoa
- Transport of the fertilized ovum to the uterus
- Implantation of the blastocyst in the uterus
- Formation of a placenta and maintenance during gestation
- Birth of the child and maternal organ return
Unfertilized Egg
- Corona radiata: an outer layer made up of follicular (granulosa) cells that form around a developing oocyte in the ovary and remain with it upon ovulation
- Zona pellucida: a specialized extracellular matrix surrounding the developing oocyte
Fetal Reproductive System Development
- Development of reproductive systems begins soon after fertilization of the egg, around 3 weeks of development
- Germ cells migrate from the yolk sac to the genital ridge
- Females are the "fundamental" sex in development, without much chemical prompting; all fertilized eggs would develop into females
Sexual Organs Development
- Bipotential tissue: same group of cells has the potential to develop into either male or female gonads
- SRY protein actively recruits other genes to develop testes and suppresses genes important in female development
- Without SRY, different genes are expressed, oogonia form, and primordial follicles develop in the primitive ovary
Male Reproductive System Development
- Scrotum formation at 9 weeks
- Testosterone induces development of the mesonephric (Wolfian) duct to form the epididymis, vas deferens, and seminal vesicles
- Testis moves from the genital ridge across the pelvis to lie at the internal inguinal ring
- Leydig cells' testosterone secretion influences tissues to become male reproductive structures
Oogenesis
- Creation of an egg in the female fetus
- Oogenesis starts in the fetus at around 7 weeks' gestation, when primordial germ cells (PGC) colonize the newly formed ovary
- Oogonia undergo mitosis
- Number of oogonia increases rapidly from about 43,000 at 7 weeks' gestation to about 7 million at 14-15 weeks' gestation
- After the seventh month of embryonic development, the number of germ cells drops precipitously
Reproductive System Development
- Minimal changes in the reproductive system between infancy and puberty
Gonadal Changes during Puberty
- Puberty-related gonadal changes occur between 9-12 years of age
- Blood levels of LH and FSH increase
- High levels of LH and FSH initiate gonadal development
- Nocturnal GnRH pulsatility (LH secretion) precedes phenotypic changes by several years
- First phenotypic changes: breast development and testicular enlargement
Folliculogenesis
- Process of ovarian follicle growth and development
Changes during Puberty (Tanner Stages)
- Puberty consists of five stages:
- At age 8, the hypothalamus increases its production of GnRH
- GnRH triggers the anterior pituitary to release LH and FSH
- LH and FSH trigger testosterone production in the testes and estrogen production in the ovaries
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Description
Learn about the rapid increase in oogonia from 7 to 14-15 weeks' gestation, followed by a drop in germ cell numbers after the seventh month. Discover the fate of oogonia during embryonic development and the transition to primary oocytes.
