Reproduction & Development FINISH AND Switch to NOTION
FSH binds to _______and aids in _________
FSH binds to sertoli cells and aids in spermatogenesis. —-
Oogonia are.....
Oogonia: are immature female reproductive cells that give rise to primary oocytes by mitosis. They are diploid.
Peristalsis in sperm helps...
Peristalsis in sperm helps contraction of smooth muscle: Remember that this is just a force that basically helps propel the sperm further along
The ovary is...
The Ovary is the part of the female reproductive system responsible for the production of eggs (singular: ovum; Plural: Ova)
The endometrium contains a mixture of ____________.
The endometrium contains a mixture of ciliated and secretory columnar cells.
5. Zygote Formation......
Zygote Formation VIdeo: https://www.youtube.com/watch?v=7G2rL5Cutd4&feature=emb_title
Androgens are....
male sex hormones
Types of asexual reproduction include....
1. Binary Fission 2. Budding 3. Regeneration (fragmentation) 4. Parthenogenesis
1. Capacitation:.......
1. Capacitation: Final Maturation Step of Sperm Prior to Fertilization Back to our dating example, you can think of capacitation as the final stage of puberty for boys. After this takes place, a boy matures into a man and is ready for romantic relationships. Likewise, capacitation is the final maturation step for the sperm prior to fertilization. After capacitation, the sperm is ready to fertilize! As the sperm is moving up in the female reproductive tract, secretions from the uterine wall triggers capacitation. Capacitation will destabilize the sperm's plasma membrane proteins and lipids resulting in: 1. Preperation of sperm tip for acrosomal reaction 2. Increases the permeability to calcium -The increase in calcium influx puts the sperm into a hyperactive state — the flagellum (tail) beats harder and it swims faster. Remember: Interestingly, the egg secretes progesterone which gives the sperm a "boost" of energy, which allows them to swim better as they journey towards the egg. Much research is going on to study this. Recently it was found that progesterone activates a calcium channel called CATSPER. CATSPER is vital for male fertility. These channels seem to be specific for sperm. The outer end of each tube is funnel shaped and contain the fimbria. The fimbria catch the secondary oocyte and channel it down into the fallopian tube when they are released by the ovary. The fallopian tube has two different cell types: 1) Non-ciliated peg cells: Peg cells provide a nutritive and a protective environment for maintaining spermatozoa as they move towards the secondary oocyte. Peg cells secretions are believed to be involved with the process called capacitation. This is a process by which the spermatozoa become fully mature and capable of fertilizing the egg. 2. Ciliated Cells: The ciliated cells beat in unison and allow the fertilized ovum to be propelled toward the uterus.
There are two ways to why Sertoli cells secrete peptide hormone inhibin to inhibit further FSH release.....
1. High sperm count induces the Sertoli cells to secrete peptide hormone inhibin which inhibits the production of FSH. 2. (FSH) stimulates sperm to develop in the seminiferous tubules in the testes. So when there is a high sperm count, we do not need high levels of FSH anymore. So to work around this, Sertoli cells begin to secrete inhibin which works on the hypothalamus gland telling the gland to stop releasing gonadotropin-releasing hormone (GnRH). GnRH acts on the anterior pituitary gland to produce FSH and LH. FSH aids in spermatogenesis LH causes Leydig Cells to secrete testosterone. When there is a high amount of testosterone, this signals the Sertoli cells too, releasing inhibin which further acts on the hypothalamus telling in to stop producing GnRH. **Elevated Levels of testosterone inhibit the secretion of GnRH - hence inhibits the release of LH and FSH.
The process of oogonia is....
1. These remaining oogonia cells will differentiate into primary oocytes, which will begin the first meiotic division before birth but will not complete meiosis I. Meiosis I will be arrested in prophase I until the age of puberty. The primary oocyte stays dormant in the ovaries until puberty. 2. The primary oocyte increases in size and a membrane called the Zona Pellucida form around it as the follicle matures. 3. Once the female hits her puberty age, the primary oocyte completes the first meiotic division. So these primary oocytes will be stimulated to develop in the process of ovulation. So when the primary oocyte completes its meiotic division, the division of cytoplasm is unequal. 4. This ovulated egg will complete the first meiotic division, producing a large secondary oocyte and a polar body. (the polar body may or may not go onto divide again through meiosis II). 4. The secondary oocyte is large because it keeps most of the cytoplasm from this division. 5. The polar body is a small daughter cell that lacks most organelles and will atrophy away. 6. At ovulation, the nucleus of the secondary oocyte begins the second meiotic division progressing only to metaphase II, then division arrests. 7. The secondary oocyte released at ovulation is surrounded by the zona pellucida and a follicular cell layer, the corona radiata. It is a large cell 8. If fertilization occurs then the second meiotic division (meiosis II) is completed, and the mature oocyte retains most of the cytoplasm, whereas the second polar body is small and degenerates. 9. However, only the oocyte can produce viable offspring (not the polar bodies) because the vast majority of the nutrients and cytoplasm in the progenitor cells go into making the oocyte viable (the polar bodies receive very little cytoplasm from each division).
2. Acrosomal Reaction: .........
2. Acrosomal Reaction: Recognition Process Between Sperm and Egg to Ensure Same-Species Fertlization The acrosomal reaction is the recognition process between the sperm and the egg before they fuse together. Think of it as a process of mutual acknowledgement to ensure same-species fertilization. Before we dive into the steps of acrosomal reaction, we will need to know the basic structure of the sperm and egg....
3. Polyspermy Block....
3. Polyspermy Block: Fast Block and Slow Block to Prevent Polyspermy (more than one sperm to penetrate the egg) In fertilization, polyspermy would occur if more than one sperm were to penetrate into the egg. This would result in a polyploidy (more than two copies of chromosomes), and would not be a viable embryo. The body has developed two types of polyspermy block: the fast block and slow block.
Menstrual Cycle .... Luteal Phase (Proliferative)...Step 4
4- Luteal Phase: follicle develops into the corpus luteum (maintained by FSH and LH) → corpus luteum produces progesterone and some estrogen → Progesterone joins estrogen in making the uterine lining receptive to embryo implantation by stimulating the thickening of the endometrial tissue and engorging it with blood. The corpus luteum is maintained by FSH and LH levels. Since the corpus luteum produces progesterone and estrogen, high levels of these hormones inhibits the hypothalamus from producing GnRH. Which means it cannot tell anterior pituitary to release FSH and LH. WIthout these high levels of FSH and LH, corpus luteum will degenerate.
Leydig cells....
A cell that produces testosterone and other androgens and is located between the seminiferous tubules of the testes.
The follicle.....
A follicle is a sac filled with fluid in which an immature egg develops. Follicles are located in the ovaries. When a follicle grows to an ideal size, ovulation occurs, which results in the rupture of a follicle and the release of an egg from the ovary. The follicle produces female sex hormones (progesterone and estrogen).
Negative Feedback Loop...
A negative feedback loop is a loop that inhibits the pathway to decrease production. An increase in A leads to a decrease in B, stopping the cycle.
A progenitor cell is....
A progenitor cell is a biological cell that, like a stem cell, has a tendency to differentiate into a specific type of cell, but is already more specific than a stem cell and is pushed to differentiate into its "target" cell.
A surge in Luteinizing Hormone (LH)....
A surge in Luteinizing Hormone (LH) causes ovulation of an egg and formation of the corpus luteum. Luteinizing hormone causes ovulation of the egg and formation of the corpus luteum - this makes intuitive sense based on the name luteinizing hormone.
An estrous cycle ....
Animals that have an estrous cycle reabsorb the endometrium if conception does not occur during the cycle. In species with these cycle, females are generally only sexually active during their estrous cycle. This is sometimes rferred to as "animals in heat". For females that have menstrual cycles, this is not true.
Negative Feedback Loop Example with Testosterone ....
As testosterone levels rise, the high testosterone level will create a negative feedback loop on the hypothalamus and the anterior pituitary gland. The hypothalamus will produce less gonadotropin releasing hormone (GnRH), and the anterior pituitary gland will produce less LH and FSH. luteinizing hormone causes the leydig cells to produce testosterone. This results in less testosterone. This is because the hormones that create high testosterone are inhibited when testosterone increases- a negative feedback loop. Remember that gonadotropin-releasing hormone (GnRH) stimulates the release of FSH and LH from the anterior pituitary gland and LH causes Leydig Cells to produce testosterone.
Blocked ovaries are one of the most common causes of infertility......
Blocked ovaries are one of the most common causes of infertility. The outer end of each tube is funnel shaped and contain the fimbria. The fimbria catch the secondary oocyte and channel it down into the fallopian tube when they are released by the ovary.
Negative Feedback Example in Menstruation...
During the menstrual cycle, follicle stimulating hormone (FSH) and luteinizing hormone (LH) cause an increase in progesterone and estrogen. The combination of increasing progesterone and estrogen causes the levels of FSH and LH to drop. This is negative feedback. (FSH and LH increases progesterone and estrogen up until a certain point. When progesterone and estrogen tells the body its at a good level, it then sends a signal to allow a decrease in FSH and LH release.)
Estrogen (AKA Estrodiol) is....
Estrogen (AKA Estradiol) — A female steroid sex hormone that is secreted by the ovary and responsible for typical female sexual characteristics such as breasts, the endometrium, and regulation of the menstrual cycle, etc.
Females have _______ ovaries.
Females have two ovaries.
Fertilization is.......
Fertilization is the joining of a haploid sperm and a haploid egg to form a diploid zygote. However, the process is much more complicated than it sounds. There are many steps involved in this fusion, it's almost as complex as going from dating someone to marrying that person.
sperm meets egg in the
Fertilization takes place in the fallopian tubes, which connect the ovaries to the uterus. Fertilization happens when a sperm cell successfully meets an egg cell in the fallopian tube.
Menstrual Cycle .... Follicular Phase (Proliferative)...Step 1
Follicular phase: In the ovaries, an ovarian follicle which is a fluid-filled sac that contains an immature egg called an oocyte. While several follicles begin to develop each cycle, one will develop the most and will become the dominant Graafian follicle. This is where the egg to be ovulated will release from. So in this phase, GRAFFIAN FOLLICLE DEVELOPS
________ are the cells of the body that produce gametes. They're the only cells in the body that can undergo mitosis as well as meiosis.
Germ cells are the cells of the body that produce gametes. They're the only cells in the body that can undergo mitosis as well as meiosis.
Gonad is _________. In males the gonads are.______. In females the gonads are______
Gonad is a primary reproductive gland that produces reproductive cells (gametes). In males the gonads are called testes; in females the gonads are called ovaries.
_______ exhibit parthogenesis by....
Honeybees exhibit parthogenesis and exhibit haplodiploidy (sex determination based on whether the organism is haploid or diploid). Offspring that arise from unfertilized eggs (parthenogenesis - asexual reproduction) are haploid male drones. Offspring that arise from fertilized eggs (sexual reproduction) are diploid female bees. https://www.youtube.com/watch?v=sd5HV1LNbcY&feature=emb_title
Humans engage in sexual reproduction, meaning.....
Humans engage in sexual reproduction, meaning offspring are created by the joining of two distinct gametes (in the case of humans, a male sperm and a female egg).
The placenta is formed by____ and secretes human chorionic gonadotropin (HCG) which functions to_____
If an embryo implants into the endometrium, the outer layer of the placenta begins to secrete human chorionic gonadotropin (HCG). If an embryo implants into the endometrium, the outer layer of the placenta begins to secrete human chorionic gonadotropin (hCG). Human chorionic gonadotropin maintains the corpus luteum, preventing the corpus luteum from degenerating. The corpus luteum is therefore able to continue to produce progesterone (progesterone maintains pregnancy and the endometrium lining) (which continues estrogen production) and this maintains the thickened endometrium, preventing menstruation. The chorion is an extraembryonic membrane formed during development. The chorion allows for gas exchange in birds and reptiles, while in mammals it attaches to the endometrium and develops into the placenta. The placenta is a structure that allows for the exchange of gases, nutrients, and wastes from the embryo and the mother. The chorion and the endometrium both form the placenta.
Menstruation...If Implantation Does NOT Occur
If implantation does NOT occur: With lower FSH and LH, the corpus luteum can no longer be maintained. The high amounts of progesterone and estrogen that is in the system which helps maintain the corpus luteum waiting for pregnancy to occur. If pregnancy does not occur the high levels of progesterone and estrogen cause the hypothalamus to stop sending GnRh to the anterior pituitary which releases LH and FSH. Therefore, estrogen and progesterone levels drop (remember, the corpus luteum was producing both progesterone and estrogen). With decreasing estrogen and progesterone, the endometrium can no longer be maintained, and the uterine line will slough off, causing menstruation (the female period). So if no pregnancy, the absence of LH and FSH leads to the degernation of the corpus luteum into what is called the corpus albicans. This is simply fibrous tissue that is eventually reabsorped. The remnants simply persist as scar tissue on the ovarian surface. Corpus albicans means "white body" due to the large amount of collagen When no fertilization, bleeding starts. Upon low levels of progesterone and estrodiol, because the corpus luteum has disintegrated, we see arteries in the endometrium constrict. O2 levels are now reduced and this leads to glandular shutdown, invasian by leukocytes, and the uterine lining breaks down and begins disintegration. Blood tissue (endometrial) are now shed. This continues for about 4 days *35 mL is the average blood loss, althrough in some women, it can be more.) Hopefully you can see that FSH and LH regulates the maturation of the follicles as well as ovulation.
Menstruation...If Implantation Does Occur
If implantation does occur: Menstruation is prevented if implantation occurs. If an embryo implants into the endometrium, the outer layer of the placenta begins to secrete human chorionic gonadotropin (HCG). Human chorionic gonadotropin maintains the corpus luteum, preventing the corpus luteum from degenerating. The corpus luteum is therefore able to continue to produce high levels of progesterone and estrogen which help maintain the uterine lining (endometrium) so it isn't shed. What occurs with the embryo from fertilization to implantation and then beyond will be discussed in the second part of this chapter.
Binary Fission is....
In binary fission, the DNA of a unicellular organism is replicated. These two identical DNA molecules migrate to opposite sides of the cell. A septum appears in the middle and forms a dividing wall to separate the two DNA. The septum then splits into two to create two separate cells, each with one copy of DNA. Binary fission occurs in prokaryotes and some organelles within eukaryotes (mitochondria and chloroplasts)
Budding is....
In budding, an outgrowth (a bud) forms on an organism (can be either unicellular or multicellular). The DNA of the organism is replicated and deposited into the bud, and the outgrowth buds off and separates from the original organism to form a new organism. Hydra (a Cnidaria) and yeast (a fungus) demonstrate budding.
In females, Follicle Stimulating Hormone (FSH)....
In females, Follicle Stimulating Hormone (FSH) stimulates follicles in the ovary to develop. Follicle stimulating hormone stimulates the follicle to develop - this makes intuitive sense based on the name follicle stimulating hormone.
In females, oogonia are.....
In females, oogonia are the primordial (earliest) egg cells. They are immature female reproductive cells that give rise to primary oocytes by mitosis. They are replicated by mitotic division before birth in the ovaries. As many as 10 million oogonia can be produced in human females; however, the large majority will apoptose and die. Only about 50,000 oogonia will remain (exact numbers aren't important - just know that many oogonia are produced, and there is major apoptosis, with only a small fraction remaining.
The head of the sperm contains acrosomes which break down______ hence allowing for _______.
In humans, the head of the sperm is called the acrosome. The acrosome contains hyaluronidase enzymes which break down the zona pellucida (outer membrane of ova - the ova is the egg cell), allowing for syngamy (fertilization). The hyaluronidase enzyme is a digestive enzyme that helps the sperm penetrate the egg for fertilization upon contact. The zona pellucida is the extracellular egg matrix which contains sperm receptors.
In humans, the male gamete is called the _______, and the female gamete is called an _____. When the gametes join they form a cell called a __________.
In humans, the male gamete is called the sperm, and the female gamete is called an egg. When the gametes join they form a cell called a zygote.
Testosterone in males ...
In males testosterone works in growth and division of cells that mature sperm and in the development of secondary male sex characteristics
In males, Follicle Stimulating Hormone (FSH)....
In males, Follicle Stimulating Hormone (FSH) stimulates sperm to develop in the seminiferous tubules in the testes
In males, Follicle Stimulating Hormone (FSH) ....
In males, Follicle Stimulating Hormone (FSH) works with sertoli cells to stimulates sperm to develop in the seminiferous tubules. Mnemonic: we know follicle stimulating hormone is abbreviated as FSH. The acronym FSH looks like the word FiSH and sperm look like swimming fish. So FSH helps development of sperm.
3. Regeneration (fragmentation) is...
In regeneration (also known as fragmentation) a piece of an organism 'breaks off.' The original organism regenerates the piece that broke off, and sometimes the fragment can regenerate into a completely new organism. Hydra and planaria flatworms demonstrate the extraordinary ability to regenerate lost body parts.
identical twins from __________ cleavage
Indeterminate cleavage refers to cells which do not have a pre-set fate. The cells of the blastomere are referred to at totipotent stem cells. These cells are capable of producing an entire zygote because it is able to produce extraembryonic structures. After the blastomere is made, it can split off from the rest of the cells and can go on to form a separate organism. When this happens in humans we get identical twins!
Menstrual Cycle Intro:
Intro: Estrogen and Progestrone levels are dropping. When estrogen and progesterone are low, this stimulates the hypothalamus to turn on and start to release GnRH. GnRH stimulates the anterior pituitary to release FSH and LH. FSH → stimulates the follicles in the ovary to develop and LH → stimulates the follicle to release the egg. When the egg gets released, the remain of the follicle develops into the corpus luteum. The corpus luteum is a hormone secreting structure, it secretes estrogen and progesterone.
LH causes .......
LH causes the Leydig cells to secrete testosterone.
Leydig Cells produce....
Leydig Cells produce testosterone in the testes
Luteinizing Hormone (LH) in males stimulates .....
Luteinizing Hormone (LH) stimulates the Leydig Cells of the testes to produce testosterone. Leydig cells are interstitial cells next to the seminiferous tubules. Luteinizing hormone is abbreviated as LH. We can think about luteinizing hormone (LH) making men look Large and Hairy (L and H, just like LH) - testosterone makes men Large and Hairy, and luteinizing hormone (LH) stimulates testosterone production from the Leydig cells.
Main Events taking place during Fertilization.....
Main Events taking place during Fertilization: 1. Capacitation 2. Acrosomal Reaction 3. Polyspermy Block 4. Completion of Meiosis II for the Secondary Oocyte 5. Zygote Formation
________ will be arrested in _________until puberty.
Meiosis I will be arrested in prophase I until puberty.
Menopause..
Menopause occurs around 48 years old. Ovarian response to LH and FSH decrease, and estrogen levels plunge. Why does this occur? Many theories have been proposed but one states that during human evolution, the mother is needed to provide care for her offsprings. This will allow an increase in survival. Only humans and a few primates (apes and chimpanzees for example) have a menstrual cycle. Others have an estrous cycle.
What can lead to more than one zygote developing?
Monozygotic twins are identical twins. In this case, one fertilization gives rise to one zygote, which then divides to form two separate embryos. The two embryos have the exact same genetic material, that's why they become identical twins. Dizygotic twins are fraternal twins. In this case, the mother ovulates two eggs and both eggs are individually fertilized by two different sperms. This leads to two different zygotes with slightly different genetic material (due to crossing over in meiosis).
Asexual Reproduction is....
Non-animal reproduction is much simpler than animal reproduction. Asexual reproduction means only one organism is needed to reproduce and create offspring (asexual means no sex is involved). Therefore all offspring are genetically identical to the parent.
The process of the acrosomal reaction....
Now that we have laid down the basic structures for the sperm and egg, we can move onto the process of the acrosomal reaction. First, the hyperactive sperm dashes through the jelly-like corona radiata. When the sperm reaches the zona pellucida, actin filaments from the sperm extend out and bind to ZP3. ZP3 is the zona pellucida protein that binds to sperm and stimulates the acrosome reaction The binding signals mutual recognition. Afterwards, the sperm's acrosome membrane fuses with the sperm head's plasma membrane. This exposes the acrosomal enzymes held within, and helps to digest through the zona pellucida. The sperm can now fuse with the egg's plasma membrane, and fertilization can occur. In mammals, the zona pellucida plays a key role to prevent fertilization between different species. For example, the sperm of a dog cannot recognize the zona pellucida of a cat's egg (no catdog for now...)
Oocyte is....
Oocyte: is a cell in an ovary which may undergo meiotic division to form an ovum.
_______ is the process by which the female gametes, or ova, are created. The female gametes is called the ______
Oogenesis is the process by which the female gametes, or ova, are created. The female gametes is called the ovum.
___________are the female germ cells.
Oogonia are the female germ cells.
Menstrual Cycle .... Ovulation Phase (Proliferative)...Step 3
Ovulation Phase: As mentioned before, the remains of the follicle after the egg is released will transform into the corpus leuteum. This is a hormone secreting structure which secretes estrogen and progesterone. Estrogen will: develop secondary female characteristics, thickens the endometrium lining making it become engorged with blood and prepare the uterus in case fertilization of an egg occurs and the developing embryo implants into the endometrium, and regulates the menstrual cycle. Progesterone: (maintains Pregnancy)- Prepares and maintains the uterus for pregnancy by preparing the egg to be implanted in the uterus. High levels of estrogen → Stimulates a surge in LH. LH causes ovulation by stimulating the follicle to RELEASE THE EGG FROM THE GRAAFIAN FOLLICLE. We now see the follicle maturing 24 hours after this surge of LH, all hell breaks loose, the ovarian wall ruptures and the secondary oocyte is released. This is often felt as a slight pain in the abdomen of the female when this event occurs. Depending on which ovary is involved, the pain can be on the left or the right side. In order for a fertilized egg to be implanted in the uterus, the egg that was released from the dominant Graffian follicle must first be transported from the ovary to the uterus through the oviduct (fallopian tube). The ovaries do not directly connect to the oviducts. The oviducts have fimbriae (fingerlike projections), and an ovulated egg is swept into the oviduct by the cilia of the fimbriae. The egg leaves the ovary, and begins to travel down the fallopian tube, where it could meet a sperm gamete, if sexual intercourse has occurred between the female and male. Fallopian Tube has two different cells: a) Non-ciliated Peg Cells: Sperm meets egg in the fallopian tubes for fertiliation. Peg cells provide a nutritive and a protective environment for maintaining spermatozoa as they move towards the secondary oocyte. Peg cells secretions are believed to be involved with the process called capacitation. This is a process by which the spermatozoa become fully mature and capable of fertilizing the egg. b) Ciliated Cells: The ciliated cells beat in unison and allow the fertilized ovum to be propelled toward the uterus.
Ovulation is....
Ovulation is the name of the process that happens usually once in every menstrual cycle when hormone changes trigger an ovary to release an egg. You can only become pregnant if a sperm fertilizes an egg. Ovulation usually happens 12 to 16 days before your next period starts
An ovulation of an egg means....
Ovulation is the release of an egg from one of a woman's ovaries. After the egg is released, it travels down the fallopian tube, where fertilization by a sperm cell may occur.
Ovum is....
Ovum: is a mature female reproductive cell, especially of a human or other animal, which can divide to give rise to an embryo usually only after fertilization by a male cell. They are haploid and have only one copy of each gene.
Oxytocin.....
Oxytocin also functions to increase contractions in labor. During childbirth, this increase in contractions pushes the child out of the womb. The baby presses against the cervix of the uterus, and this stimulates a nerve. The nerve signals the hypothalamus and posterior pituitary gland to release more oxytocin, which causes more contractions, which causes greater pressure on the cervix, which causes more oxytocin release, which causes more contractions...etc. —again, a positive feedback loop.
PRIMARY OOCYTE GETS ARRESTED IN ______ UNTIL OVULATION (PUBERTY) AND SECONDARY OOCYTE GETS ARRESTED IN _________ UNTIL FERTILIZATION
PRIMARY OOCYTE GETS ARRESTED IN PROPHASE I UNTIL OVULATION (PUBERTY) AND SECONDARY OOCYTE GETS ARRESTED IN METAPHASE II UNTIL FERTILIZATION
Parthenogenesis is....
Parthenogenesis is when an unfertilized egg develops into a viable (living) organism. Many species that exhibit parthenogenesis can reproduce both sexually and asexually, but resort to sexual reproduction when the environmental conditions are not ideal and cannot sustain large populations. This is because sexual reproduction is slower and produces fewer offspring.
Parts of the vagina include.....
Parts of the vagina include the 1. labia majora 2. labia minora 3. the clitoris which contains erectile tissue similar to the male penis. The clitoris is highly sensitive and richly supplied with nerve endings.
Positive Feedback loops...
Positive Feedback loops: A positive feedback loop is a loop that ramps itself up, or stimulates the pathway to increase production. An increase in A leads to an increase in B, which leads to an increase in A... and so on. Prolactin and oxytocin are two hormones released by the pituitary gland that exhibit a positive feedback loop.
Progesterone .....
Progesterone (hint=pregnancy) — A steroid hormone that is produced in the ovary that prepares and maintains the uterus for pregnancy by preparing the egg to be implanted in the uterus.
Prolactin.....
Prolactin functions to stimulate lactation (milk production) in female mammals in response to infant suckling. The more the infant suckles, the more prolactin is produced, leading to more milk production, which causes the infant to suckle more... a positive feedback loop. While prolactin produces the milk, oxytocin releases the milk. It helps perform the milk let down reflex, which increases contractions of smooth muscle in the breast to eject the milk. As the baby continues to suckle, prolactin and oxytocin work together to produce and release more milk.
4. Completion of Meiosis II for the Secondary Oocyte....
Recall from the reproductive section that the egg is arrested in metaphase II during meiosis. After successful penetration, the secondary oocyte will go through the rest of meiosis II and produce a second polar body — to be expelled out of the body. This will result in a mature haploid oocyte which can fuse together with the haploid sperm to form a diploid zygote. Remember that after ovulation the secondary oocyte is arrested in metaphase of meiosis II until fertilization. After fertilization, the secondary oocyte completes meiosis II to form a mature oocyte and a second polar body. VERY IMPORTANT: REMEMBER THAT PRIMARY OOCYTE GETS ARRESTED IN PROPHASE I UNTIL OVULATION AND SECONDARY OOCYTE GETS ARRESTED IN METAPHASE II UNTIL FERTILIZATION
Remember that the cells from each parent that combine to form the _______are called _______.
Remember that the cells from each parent that combine to form the zygote are called gametes.
Reproduction is the process of....
Reproduction is the process of producing repeats; children are made from parent organisms. Reproduction ranges from single cell organism replication, to the production of parental germ cells that combine to form new offspring.
Semen is the combination of ......
Semen is the combination of sperm and secretions from the accessory glands.
SEVEn UP - Mnemonic: The pathway of sperm movement can be easily remembered by the acronym SEVEn UP:
Seminiferous tubules Epididymis Vas deferens (nothing) Ejaculatory duct Urethra Penis. (Note that the letter 'n' in "seven" does not stand for anything - it is just included to make the acronym more memorable).
Sertoli cells also contain__________, which acts on the ______________ to inhibit further FSH release so that sperm cells can stop developing. This is an example of___________
Sertoli cells also contain peptide hormone inhibin that they secrete, which acts on the anterior pituitary to inhibit further FSH release so that sperm cells can stop developing. This is an example of negative feedback.
What is the blood-testis barrier?
Sertoli cells occupy 25% of the volume of the seminiferous epithelium. These cells contain an impressive cytoskeleton of microtubules involved with intracellular transport. The blood-testis barrier (BTB) that forms from specialized junctions between adjacent Sertoli cells in the seminiferous epithelium is critical because they form specialized tight junctions termed the blood-testis barrier. This barrier prevents the body from destroying sperm.
Sperm contributes....
Sperm contribute very little cytoplasm or nutrients to the fertilized egg, and it is the responsibility of the high-investment oocyte to provide enough for the offspring to survive.
Spermatogenesis occurs in the .....
Spermatogenesis occurs in the seminiferous tubules located in the testes.
___________ are the male germ cells
Spermatogonia are the male germ cells
Testosterone is......
Testosterone is a male sex hormone that is important for sexual and reproductive development. Women also produce testosterone, but at lower levels than men. Testosterone is a gonadal steroid hormone. Testosterone functions in spermatogenesis to mature the sperm, and is responsible for contributing to male secondary sex characteristics (facial hair, lean muscle mass etc.)
The Sperm is composed of three major parts...........
The Sperm is composed of three major parts: the Head, the midpiece, and the tail.
The bulbourethral gland ....
The bulbourethral gland also produces viscous mucus that helps clean and lubricate the urethra.
The categorization of what type of feedback loop the hormone exhibits is dependent on the context....
The categorization of what type of feedback loop the hormone exhibits is dependent on the context. For example, testosterone stimulating sperm maturation is the effect of a hormone on its target. Mature sperm do not stimulate or inhibit further testosterone production. This is not an example of a feedback loop. Therefore, we cannot say testosterone exhibits negative feedback simply from the paragraph above, because that is specific to the context of testosterone's effect on GnRH, LH, and FSH.
Do primary spermatocytes form after birth.....
The continuous production of primary spermatocytes occur in the male after puberty, unlike primary oocytes in females which are only present at birth and do not form after birth.
The corpus luteum....
The corpus luteum also produces female sex hormones (progesterone and estrogen). When a follicle breaks open and releases the ovum, the follicle remains transforms into the corpus luteum. The corpus luteum is a hormone secreting structure that develops in an ovary after the ovum has been discharged from the follicle. The corpus luteum secretes the hormone progesterone. (Hint Progesterone = pregnancy). So progesterone helps maintain pregnancy by the development and maintaining the endometrium. The endometrium is the most inner lining that is enforced with blood. If pregnancy does not occur then this corpus luteum degenerates away and the endometrium breaks down as well and this is how your period basically starts if you don't get pregnant.
Acrosomal Reaction....Egg....
The egg has several layers for the sperm to penetrate — it takes a lot of work for a sperm to be accepted! The outermost layer of the egg of a mammal is called the corona radiata. It is a jelly coat made up of follicular cells, which nourishes the egg when it was a developing follicle inside the ovary. Within the corona radiata, there is a layer of glycoproteins called the vitelline layer that surrounds the plasma membrane of the egg. In mammals, this layer is called the zona pellucida. The zona pellucida is a VERY important structure for acrosomal reaction. There are four main zona pellucida proteins: ZP1, ZP2, ZP3, ZP4. ZP3 is the zona pellucida protein that binds to sperm and stimulates the acrosome reaction. Good to keep this in mind! Underneath the zona pellucida is the egg's plasma membrane.
The ejaculatory ducts is where....
The ejaculatory ducts is where the vas deferens meets the seminal vesicles. The seminal vesicle is a gland that secretes: 1. fructose 2.viscous mucus 3. prostoglandins. The ejaculatory ducts propel the sperm into the urethra, which leads to ejaculation of the sperm out of the penis as semen.
The __________ lining is very important because....
The endometrium is the inner lining which is very important, as is is highly vascularized, in other words, rich in blood vessels.
The epididymis is...
The epididymis is a duct that sits around the testes, and is the site of sperm storage before ejaculation. This is where sperm attains maturation, motility, and membrane receptors for the zona pellucida protein, and also acrosomal maturation.
Fast Block:......
The fast block happens first. It occurs immediately after the sperm's membrane has fused with the egg's membrane. When the sperm penetrates into the egg, sodium ions diffuse into the egg and cause the egg membrane to depolarize (become positively charged). Depolarization repels additional sperms from binding for a few seconds. This is called the fast block because it happens right after fusion of sperm and egg, and because it lasts for only a short period of time.
The midpiece of the sperm.....
The midpiece connects the head to the tail. 1. It's most important characteristic is that it contains a lot of mitochondria. As you may recall, the mitochondria are organelles that produce ATP. The sperm has to expend a lot of energy trying to move through the female reproductive system to reach and fertilize the egg. The mitochondria at the midpiece provides this necessary energy.
Do primary oocytes form after birth.....?
The ova are formed in the ovary from cells called oogonia which proliferate by mitotic division. All of the oogonia enlarge to form primary oocytes, of which about 2 million are present at birth. No primary oocytes form after birth About 2 million primary oocytes are found in the ovaries of a newborn female. Many regress during childhood so that at puberty about 30-40 thousand remains. Only about 200-400 of these ever reach full maturity after puberty and are expelled at ovulation during the female's reproductive life.
The prostate gland ....
The prostate gland makes the semen more alkaline (basic) so that the sperm can survive the acidity of the female reproductive tract.
The seminal vesicles is a gland that secretes....
The seminal vesicles is a gland that secretes.... 1. Fructose which provides the sperm with nutrients to produce ATP for motility. 2- Viscous mucus, which cleans and lubricates the urethra. 3- Prostaglandins, which stimulates contraction of the urethra. Contractions further help the sperm move through the urethra.
The seminiferous tubules contain ....
The seminiferous tubules contain two types of cells that partner together 1. spermatogenic cells that give rise to spermatozoa (mature motile male sex cells.) 2. 'nurse-like' Sertoli cells (which surround and nourish the developing sperm cells within the testes)
The seminiferous tubules do not fully mature the sperm, therefore....
The seminiferous tubules do not fully mature the sperm (the sperm are not fully motile and cannot fertilize eggs at this point in their development). Therefore, they are transported by peristalsis to the epididymis for maturation.
The ______ block is much more effective than the ______block. ......
The slow block is much more effective than the fast block. However, due to its slow onset, the fast block is also crucial to prevent polyspermy before the slow block takes action. These two blocks work in conjunction to ensure a faithful marriage between a sperm and an egg, which in turn secure a viable embryo.
Slow Block.....
The slow block is the longer-lasting solution to prevent polyspermy. It happens gradually after the sperm has fused with the egg. In addition to depolarization of the membrane, the slow block also triggers a release of calcium ions inside the egg's plasma membrane. The calcium ions will stimulate the egg to undergo the cortical reaction which is the exocytosis (release) of cortical granules. The cortical granules play a key role in the slow block. They serve two functions: 1. Changes the zona pellucida (vitelline layer) into an impenetrable fertilization envelope. 2. Stimulate proteases (protein-cutting enzymes) to sever the link between the zona pellucida (vitelline layer) and the plasma membrane. -This prevents other sperm from reaching the egg's plasma membrane The slow block is much more effective than the fast block. However, due to its slow onset, the fast block is also crucial to prevent polyspermy before the slow block takes action.
The tail of the sperm.....
The tail of the sperm is a long flagellum that moves around in a whip-like, beating motion that propels the sperm forward and gives it mobility. The tail (like all flagella of eukaryotes) is made of microtubules (which are made of tubulin, the building block of microtubules).
The testes....
The testes are the male reproductive gland and are the site of spermatogenesis (the production of sperm).
Acrosomal Reaction....Sperm....
The tip of the sperm's head is the acrosome, which contains hydrolytic enzymes that will digest through the outer coating of the egg in order to allow sperm penetration.
The uterus is ____
The uterus is a muscular organ that functions to provide an ideal environment for a fertilized egg to implant into, grow, and ultimately develop into an embryo.
The uterus is the ________
The uterus is the womb!
The Uterus is composed of __________
The uterus is the womb! It is composed of three layers: 1. perimetrium (outer layer) 2. myometrium (smooth muscle, middle layer) 3.endometrium (inner epithelial layer, lined by mucous membranes)
The uterus leads to the ________, a narrow opening of uterus that leads to the _________.
The uterus leads to the cervix, a narrow opening of uterus that leads to the vagina.
The vagina......
The vagina acts as the opening between the uterus (and its contents) with the external environment. 1. It is where sperm first enter the female body to fertilize eggs, 2. It is where newborn babies that were developing in the uterus exit the female body (parturition, ie. giving birth/delivery). The vagina is an extended, thin-walled tubular canal that connects the cervical area with the outside of the body.
The vas deferens in the testes....
The vas deferens is a group of tubules that helps move sperm from the storage area in the epididymis towards the ejaculatory ducts. Peristalsis is the force that helps propel the sperm further along.
The Zona Pellucida is...
The zona pellucida is the outer membrane of ova. Ova is the egg cell The zona pellucida contains sperm receptors.
The head of the sperm....
There are certain characteristics of the head that are important to remember. 1. The head is the part of the sperm that contains the nucleus, meaning the head contains all the genetic information. 2. The head also has an organelle called the acrosome at the very tip. The acrosome contains digestive enzymes that help the sperm penetrate the egg for fertilization upon contact. 3. Right underneath the head of the sperm is a pair of centrioles; eggs have none. The Sperm's centrioles are absolutely essential for forming a centrosome which will form a spindle enabling the first division of the zygote to take place post fertilization.
The accessory glands of the male reproductive system are....
There are three accessory glands in the male reproductive system tract that contribute certain secretions to the sperm to form semen. These secretions aid sperm in achieving successful fertilization when ejaculated into the female reproductive tract. 1.The seminal vesicles 2. prostate gland 3. The bulbourethral glands. These glands secrete fluids that enter the urethra.
The remaining oogonia cells...
These remaining cells will differentiate into primary oocytes before birth in the female, which will begin the first meiotic division but will not complete meiosis I. Meiosis I will be arrested in prophase I until puberty.
Top Functions of Sertoli Cells
Top Functions of Sertoli Cells: 1. "Nurse-like" Sertoli cells nourish the developing sperm within the testes in the seminiferous tubules 2. Contain peptide hormone inhibin, which acts on the anterior pituitary to inhibit further FSH release so that sperm cells can stop developing. WHY? 1. High sperm count induces the Sertoli cells to secrete peptide hormone inhibin which inhibits the production of FSH. 2. (FSH) stimulates sperm to develop in the seminiferous tubules in the testes. So when there is a high sperm count, we do not need high levels of FSH anymore. **Elevated Levels of testosterone inhibit the secretion of GnRH - hence inhibits the release of LH and FSH. 3. they are involved with the blood-testis barrier. The blood-testis barrier (BTB) that forms from specialized junctions between adjacent Sertoli cells in the seminiferous epithelium is critical because they form specialized tight junctions termed the blood-testis barrier. This barrier prevents the body from destroying sperm.
Separation of a human embryo at the two-cell stage into two distinct masses would most likely result in
When an embryo is separated at the two-cell stage, monozygotic twins result. These blastomere cells are referred to at totipotent stem cells which are capable of producing a zygote because they can form extramembryonic membranes. Each monozygotic twin would develop separately, leading to two separate placentas and separate amniotic and chorionic cavities.
When eggs are released from the ovary, they travel through the __________(also known as the __________) to the ________.
When eggs are released from the ovary, they travel through the oviduct (also known as the fallopian tube) to the uterus.