The sperm reaches the caudal epididymis approximately 72 days after the initiation of spermatogenesis


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The sperm reaches the caudal epididymis approximately 72 days after the initiation of spermatogenesis.

  • The sperm reaches the caudal epididymis approximately 72 days after the initiation of spermatogenesis.

  • Preservation of optimal sperm function during storage requires adequate testosterone levels and maintenance of a normal scrotal temperature.



The alkaline pH of semen provides protection for the sperm from the acid environment of the vagina.

  • The alkaline pH of semen provides protection for the sperm from the acid environment of the vagina.

  • The human, sperm can be found in the tube 5 minutes after insemination.

  • Of an average of 200 to 300 million sperm deposited in the vagina, at most only a few hundred achieve proximity to the egg.



Capacitation is characterized by three accomplishments:

  • Capacitation is characterized by three accomplishments:

    • The ability to undergo the acrosome reaction.
    • The ability to bind to the zona pellucida.
    • The acquisition of hypermotility.


There is a breakdown and merging of the plasma membrane and the outer acrosomal membrane, the acrosome reaction.

  • There is a breakdown and merging of the plasma membrane and the outer acrosomal membrane, the acrosome reaction.



Approximately 72 days are required to produce spermatozoa, a time period followed by storage in the epididymis prior to ejaculation.

  • Approximately 72 days are required to produce spermatozoa, a time period followed by storage in the epididymis prior to ejaculation.

  • Sperm enter the cervical mucus and then the fallopian tubes within minutes, but only a few hundred sperm or less reach the oocyte. The cervix serves as a reservoir of sperm for up to 72 hours.

  • Capacitation, a process initiated during the sperm's passage through the cervix or during in vitro incubation in an appropriate medium, is characterized by the acquired ability of sperm to undergo the acrosome reaction to bind to the zona pellucida and to acquire hyperactivated motility.

  • The acrosome reaction is due to the modification and breakdown, followed by a merger, of the sperm cell membrane and the outer acrosomal membrane, allowing the release of enzymes and changes in the inner acrosomal membrane, necessary for fusion with the oocyte cell membrane.



After ovulation, the oocyte and its surrounding cumulus are in the ampulla of the fallopian tube within 2–3 minutes.

  • After ovulation, the oocyte and its surrounding cumulus are in the ampulla of the fallopian tube within 2–3 minutes.

  • Tubal transport depends on smooth muscle contractions and ciliary-induced flow of secretory fluid.

  • The fallopian tube provides an important holding action.





The oocyte, at the time of ovulation, is surrounded by granulosa cells (the cumulus oophorus).

  • The oocyte, at the time of ovulation, is surrounded by granulosa cells (the cumulus oophorus).

  • The zona pellucida, a noncellular porous layer of glycoproteins secreted by the oocyte, separates the oocyte from the granulosa cells.





The ovulated eggs adhere with their cumulus mass of follicular cells to the surface of the ovary.

  • The ovulated eggs adhere with their cumulus mass of follicular cells to the surface of the ovary.

  • The fimbriated end of the tube sweeps over the ovary in order to pick up the egg.

  • the egg spends about 80 hours in the tube, 90% of which is in the ampulla at the junction of the ampulla with the isthmus.

  • It is in this location that fertilization and dispersion of the cumulus cells are completed.





The fertilizable life of the human oocyte is unknown, but most estimates range between 12 and 24 hours.

  • The fertilizable life of the human oocyte is unknown, but most estimates range between 12 and 24 hours.

  • The cumulus oophorus undergoes expansion that may have two important roles.

    • the expanded cumulus may serve to increase the chances of an encounter with one of the few spermatozoa
    • this change may facilitate sperm passage through the cumulus


Sperm pass through the cumulus without the release of acrosomal enzymes.

  • Sperm pass through the cumulus without the release of acrosomal enzymes.

  • The acellular zona pellucida that surrounds the egg at ovulation remains in place until implantation. It has two major functions in the fertilization process:

    • The zona pellucida contains ligands for sperm, which are, with some exceptions, relatively species-specific.
    • The zona pellucida undergoes the zona reaction in which the zona becomes impervious to other sperm once the fertilizing sperm penetrates.


Penetration through the zona is rapid and mediated by acrosin, a trypsin-like proteinase that is bound to the inner acrosomal membrane of the sperm.

  • Penetration through the zona is rapid and mediated by acrosin, a trypsin-like proteinase that is bound to the inner acrosomal membrane of the sperm.

  • Changes brought about by these enzymes lead to the zona reaction, the hardening of the extracellular layer by cross-linking of structural proteins, and inactivation of ligands for sperm receptors.





Approximately 3 hours after insemination, meiosis is completed. The second polar body is released and leaves the egg with a haploid complement of chromosomes.

  • Approximately 3 hours after insemination, meiosis is completed. The second polar body is released and leaves the egg with a haploid complement of chromosomes.

  • The addition of chromosomes from the sperm restores the diploid number to the now fertilized egg.







Sperm penetration of the zona pellucida depends on a combination of sperm motility, an acrosomal proteinase, and binding of sperm head receptors to zona ligands.

  • Sperm penetration of the zona pellucida depends on a combination of sperm motility, an acrosomal proteinase, and binding of sperm head receptors to zona ligands.

  • Binding of sperm head receptors and zona ligands produces an enzyme complex that induces the acrosome reaction, releasing enzymes essential for the fusion of the sperm and oocyte membranes.

  • Fusion of the sperm and oocyte membranes triggers the cortical reaction, the release of substances from the cortical granules, organelles just below the egg cell membrane.

  • The cortical reaction leads to the enzyme-induced zona reaction, the hardening of the zona and the inactivation of ligands for sperm receptors, producing an obstacle to polyspermy.

  • Cell division begins promptly after fertilization; human gene expression begins between the 4- and 8-cell stages.





The endometrium is 10–14 mm thick at the time of implantation, in the midluteal phase.

  • The endometrium is 10–14 mm thick at the time of implantation, in the midluteal phase.

  • By this time, secretory activity has reached a peak, and the endometrial cells are rich in glycogen and lipids.





The window of endometrial receptivity is restricted to days 20–24 of a 28-day normal cycle.

  • The window of endometrial receptivity is restricted to days 20–24 of a 28-day normal cycle.

  • Endometrial receptivity is heralded by the progesterone-induced formation of pinopodes, surface epithelial cells that lose their microvilli and develop smooth protrusions.



Implantation is defined as the process by which an embryo attaches to the uterine wall and penetrates first the epithelium and then the circulatory system of the mother to form the placenta.

  • Implantation is defined as the process by which an embryo attaches to the uterine wall and penetrates first the epithelium and then the circulatory system of the mother to form the placenta.

  • The human blastocyst remains in the uterine secretions for approximately 1 to 3 days and then hatches from its zona pellucida in preparation for attachment.



The blastocyst loosely adheres to the endometrial epithelium, a process called apposition, which most commonly occurs on the endometrium of the upper posterior wall of the uterus.

  • The blastocyst loosely adheres to the endometrial epithelium, a process called apposition, which most commonly occurs on the endometrium of the upper posterior wall of the uterus.

  • Cytokines, growth factors, and their receptors have been identified in virtually all tissues associated with implantation.



Three types of interactions between the implanting trophoblast and the uterine epithelium:

  • Three types of interactions between the implanting trophoblast and the uterine epithelium:

    • trophoblast cells intrude between uterine epithelial cells on their path to the basement membrane.
    • the epithelial cells lift off the basement membrane, an action that allows the trophoblast to insinuate itself underneath the epithelium.
    • fusion of the trophoblast with individual uterine epithelial cells




In the second week after ovulation, the placenta is formed.

  • In the second week after ovulation, the placenta is formed.

  • By this time, the trophoblasts at the implantation site have formed masses of cytotrophoblasts and syncytiotrophoblasts, and invasion of maternal blood vessels has begun.

  • The walls of the spiral arteries are destroyed, as sinusoidal sacs are formed lined with endovascular trophoblast.





The purpose of placental invasion is to remodel the uterine vasculature, establishing a structure that will allow and maintain an interchange between mother and fetus.

  • The purpose of placental invasion is to remodel the uterine vasculature, establishing a structure that will allow and maintain an interchange between mother and fetus.



After implantation is complete, the trophoblast further differentiates along two main pathways, giving rise to

  • After implantation is complete, the trophoblast further differentiates along two main pathways, giving rise to

    • Villous trophoblast
    • extravillous trophoblast.
  • The villous trophoblast, as its name suggests, gives rise to the chorionic villi of the placenta, and primarily functions in the transport of oxygen and nutrients between the fetus and mother.



The extravillous trophoblast migrates into the decidua and myometrium and also penetrates maternal vasculature.

  • The extravillous trophoblast migrates into the decidua and myometrium and also penetrates maternal vasculature.

  • The mechanisms leading to trophoblast invasion into the endometrium are similar to the characteristics of metastasizing malignant cells.



About 12 days after conception, the syncytiotrophoblast of the trophoblast shell is permeated by a system of intercommunicating channels of trophoblastic lacunae, or small cavities.

  • About 12 days after conception, the syncytiotrophoblast of the trophoblast shell is permeated by a system of intercommunicating channels of trophoblastic lacunae, or small cavities.

  • As the embryo enlarges, more maternal tissue (decidua basalis) is invaded by the basal syncytiotrophoblast, including the walls of the superficial decidual capillaries, and these lacunae become filled with maternal blood







As the growth of embryonic and extraembryonic tissues continues, the blood supply of the chorion facing the endometrial cavity is restricted, and consequently the villi in contact with the decidua capsularis cease to grow and degenerate.

  • As the growth of embryonic and extraembryonic tissues continues, the blood supply of the chorion facing the endometrial cavity is restricted, and consequently the villi in contact with the decidua capsularis cease to grow and degenerate.

  • This portion of the chorion becomes the avascular fetal membrane that touches the decidua parietalis (chorion laeve)





As the fetus grows, the decidua capsularis merges with the decidua parietalis. The decidua capsularis, however, is largely lost by pressure and the attendant loss of blood supply. The area of decidua where decidua capsularis and decidua parietalis merge is referred to as the decidua vera

  • As the fetus grows, the decidua capsularis merges with the decidua parietalis. The decidua capsularis, however, is largely lost by pressure and the attendant loss of blood supply. The area of decidua where decidua capsularis and decidua parietalis merge is referred to as the decidua vera



At approximately 1 month after conception, maternal blood enters the intervillous space from the spiral arteries in fountain-like bursts.

  • At approximately 1 month after conception, maternal blood enters the intervillous space from the spiral arteries in fountain-like bursts.







HUMAN CHORIONIC GONADOTROPIN

  • HUMAN CHORIONIC GONADOTROPIN

    • Rescue and maintenance of function of the corpus luteum
    • Promote male sexual differentiation
    • Stimulation of the maternal thyroid gland
    • Promotion of relaxin secretion
    • Promote uterine vascular vasodilatation and myometrial smooth muscle relaxation


HUMAN PLACENTAL LACTOGEN

  • HUMAN PLACENTAL LACTOGEN

    • Maternal lipolysis and an increase in the levels of circulating free fatty acids
    • An anti-insulin or "diabetogenic" action
    • A potent angiogenic hormone; it also may play an important role in the formation of fetal vasculature




Chorionic Adrenocorticotropin

  • Chorionic Adrenocorticotropin

  • Relaxin

  • Parathyroid Hormone-Related Protein

  • Growth Hormone Variant

  • Etc.




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