Lecture 17 - Reproduction
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What is preformation?
Embryo is preformed and grows or enlarged during development
What is epigenesis?
Man arises from the successive differentiation of a formless being • menstrual blood and semen
What is a biopotential gonad?
Sexually indifferent stage in which the embryo has the potential to develop either male or female structures
What do the Wolffian (mesonephric) ducts develop into?
Epididymis, ductus deferens, seminal vesicle, urethra
What do the Mullerian (paramesonephric) ducts develop into?
Oviduct, uterus, cranial vagina
What is the importance of sex differentiation?
Depends on the sex chromosomes X and Y • specification of the gonad as either testes or ovaries • SRY (Sex-determining Region of the Y chromosome)
What variation must happen for sex differentiation?
Absence of SRY gene - gonads will be ovaries, anti-mullerian hormone, peptide hormone that causes the Müllerian ducts to regress (FEMALE) With SRY gene - Anti-mullerian hormone (AMH), peptide hormone that causes the Müllerian ducts to regress
What is a Freemartin?
Abnormal embryogenesis of the female reproductive tract • Heifer born twin to a bull
What is Oogenisis?
Production of female gametes, oocytes
What is folliculogenesis?
Follicle maturation and ovulation
What are functions of the ovary?
Oogenisis and folliculogenesis Produce sex hormones estrogen and progesterone
What is the function in the female reproductive tract of Gonadotropin Releasing Hormone?
GnRH - released by the hypothalamus that stimulates release of LH and FSH from the anterior pituitary
What is the function in the female reproductive tract of Luteinizing Hormone
LH - stimulates estrogen production in ovary and ovulation by binding LH - receptor on the Theca cells
What is the function in the female reproductive tract of Estrogen?
• Produced in the granulosa cells by conversion of testosterone to estrogen, primary targets is the reproductive tract • induction of pre-ovulatory surge of LH, mucus production, increased blood flow, reproductive behaviors
What is the function in the female reproductive tract of Progesterone?
• produced by the corpus luteum after ovulation, maintenance of pregnancy
When is meiosis arrested and when does it resume?
Meiosis 1 resumes at ovulation Meiosis 2 is completed at fertilization
What is the process of Oogenisis?
• developing female embryo produces oognia • undergo mitotic divisions up to birth, begin meiosis after birth and stop at prophase 1 • at puberty, FSH stimulates follicle growth, and reactivates meiosis • process stops again at meiosis 2 • ovum released at ovulation is the secondary oocyte • completion of meiosis and shedding of the last polar body may occur as late as fertilization
What is folliculogenesis?
The process in which immature follicles develop into more advanced follicles and become candidates for ovulation
What is the function of the ovary?
• highly vascularized: nutrient and oxygen delivery (hormones in and out)
Theca cells
Have LH receptors - stimulation of ovulation, formation of CL, progesterone secretion
Granulosa cells
Line the antrum of the pre-ovulation you follicle, have FSH receptors with primary action of follicular development and estrogen synthesis
Pre-ovulatory (tertiary) follicle
Characterized by fluid-filled cavity (antrium) filled with follicular fluid; have Theca and granulosa cell layers, secondary oocyte Follicle that is ovulated
Corpus luteum
Large “yellow bodies” that produce progesterone, formed from granulosa and the cal cells after ovulation
Corpus albicans
White, scar-like structure that represents degenerating CL, increasing connective tissue, decreasing secretory tissue