Animal Reproduction

Question 1

Sexual and Asexual reproduction

Answer 1

Sexual reproduction: an egg an a sperm, both haploid, fusing to create a diploid zygote
-happens in majority of reproduction in animal kingdom
Asexual reproduction: creating offspring without the fusion of sperm and egg
-three diff types of asexual reproduction: budding, regeneration, and parthenogenesis
-budding: will still yield a completely new individual; going through the idea of cell division and cell differentiation like sexual reproduction, but mechanism is different

Question 2

Mechanisms of Asexual Reproduction

Answer 2

• Budding only happens with invertebrates BUT that doesn’t mean vertebrates cannot go through other forms of asexual reproduction; just not this one.
• Asexual reproduction: ability to generate a new individual from an existing one; parent provides info that yields that offspring
• process of fission is another mechanism of asexual reproduction; where parent separates into two or more individuals of the same size (like bacteria)

Question 3

Asexual Reproduction in Hydra

Answer 3

• Hydra= type of nedariun
• they experience budding and it
• looks like a protrusion from the parent that will give rise to an entirely new hydra
• still going to be mitotic division and differentiation to generate new individual
• new individual can become independent organism (separate from parent) or remain attached to parent (referred to as colony)
• more than one bud can be produced from organism, and can be in multiples or happen simultaneously
• process of budding can take place throughout the duration of the hydras lifetime

Question 4

Fertilization depends on mechanism that bring together sperm and egg

Answer 4

Two types of fertilization: External fertilization and Internal fertilization
-External fertilization: ex of a frog, Male frog will grasp female frog and insert sperm into the eggs as the female is releasing them into the water
Internal fertilization: an adaptation to environmental change. Bc organisms moved from water to dry land (terrestrial), there needed to be an evolution on how fertilization takes place in order to avoid desiccation (dry out). Bc if gametes dry out, not going to be able to successfully meet each other. Direct passing of male gametes into female reproductive system is how internal fertilization is able to occur
-both mechanisms, internal and external fertilization require the habitat or the surroundings in which gametes meet one another to be an aqueous one

Question 5

Asexual vs. Sexual Reproduction

Answer 5

Asexual Reproduction:

-female give rise to offspring
-each offspring can give rise to next generation
-can expand upon generation without a mate
Benefit: can reproduce even when isolated, doesn’t have to look for mate, so can reproduce very rapidly
-some asexual organisms can also go through sexual reproduction (like hydra)
-asexual reproduction would expect to be taking place in areas that are stable, not a lot of fluctuations that are organism would need to respond to and evolve
disadvantages: once environmental conditions change, an organism that is exclusively using asexual reproduction, it won’t be able to change to adapt

Sexual Reproduction:

• female is only capable of producing half as many offspring bearing progeny (bc males can’t give birth); so reduction in proliferation capacity
• has unique costs; male and female required specialized body parts needed in order to mate
• need to find another to mate
• we use this mechanism even tho it has the disadvantages above compared to asexual reproduction bc it allows for greater genetic variation
• through genetic recombination, law of independent assortment, and law of segregation, these all allow for a better ability to adapt to environmental changes w/ some combos of alleles promotes survival and reproduction, and those can be upheld through subsequent generations through natural selection

Question 6

Fertilization depends on mechanism that bring together sperm and egg

Answer 6

Two types of fertilization: External fertilization and Internal fertilization
-External fertilization: ex of a frog, Male frog will grasp female frog and insert sperm into the eggs as the female is releasing them into the water
Internal fertilization: an adaptation to environmental change. Bc organisms moved from water to dry land (terrestrial), there needed to be an evolution on how fertilization takes place in order to avoid desiccation (dry out). Bc if gametes dry out, not going to be able to successfully meet each other. Direct passing of male gametes into female reproductive system is how internal fertilization is able to occur
-both mechanisms, internal and external fertilization require the habitat or the surroundings in which gametes meet one another to be an aqueous one

Question 7

fertilization depends on mechanism that brings sperm and egg together (these are both methods of sexual reproduction)

Answer 7

Two diff types of fertilization: external fertilization and internal fertilization
External fertilization: : ex: frog
Male will grasp the female frog and discharge fluids that contain sperm onto the eggs as the female is releasing them onto the water
Internal fertilization: an adaptation to environmental change
When it comes to organisms that transition and result in organism that live on land or terrestrial organism in contrast to water, there needs to be an evolution on how fertilization takes place in order to avoid desiccation (dry out)
Bc if these gametes dry out (if the egg was just on land to be fertilized), they’re not going to be successfully meet with one another and generate offspring
A way to introduce gametes directly to one another and in doing so bypass any possibility of dedication occurring
Direct passing of male gametes into female reproductive system is how internal fertilization is able to allow for these gametes to meet one to produce offspring
Both of these are mechanisms in which we can achieve fertilization bit in both the idea her is that the habitat or surroundings in which these gametes need to meet one another needs to eb an aqueous one

Question 8

Ensuring the Survival of Offspring

Answer 8

• Internal fertilization helps enhance the survival of offspring
• with external fertilization, the sperm and egg might not meet, as they are meeting in a large aq environment, so a lot of egg and sperm get released as they know not all of them will be viable; so more gametes being released with less chances of survival (although there are some mechanisms in place to ensure the embryos that do make it are cared for as best as they can in aq environment)
• for internal fertilization, fewer gametes are produced, but the survival rate is much higher (probably due to the more controlled environment of fertilization in the female and the growth in that area only- these are my thoughts)

Question 9

internal fertilization strategies for offspring development:

Answer 9

oviparity: fertilization occurs internally but the process of developing happens externally
-ex: birds
ovoviviparity: fertilization occurs internally and development also happens internally but right before it’s going to hatch (come out of egg), egg is released to hatch externally
-nourishment comes from the egg yolk, not from the mother directly
Viviparity: fertilization occurs internally and all of development happens internally as well
-nourishment is directly from maternal blood rather than egg yolk
-ex: humans using placenta

Question 10

gamete production and delivery

Answer 10

• gametes are made from gonads, which are organs
• gametes are made from precursor cells
• in order to deliver those glands, there is going to be accessories; like duct system and glands that can secrete content that can help facilitate the movement of the gametes

Question 11

Human Male Reproductive Anatomy

Answer 11

External reproductive anatomy: scrotum and penis
Internal reproductive anatomy: gonads (produce sperm and hormones), glands (that secrete products needed for sperm movement), and ducts (that carry sperm and glandular secretions)

Question 12

The Human Male Reproductive Anatomy: more specific

Answer 12

• Male gonads: testis = sperm production; has scrotum (which houses testis), and septum (which creates divide to protect testis from becoming infected by the other)
• ducts: epididymis, ductus deferens, urethra, ejaculatory duct = moving sperm through reproductive tract
• Accessory glands: seminal vesicle, prostate gland, bulbourethral gland = secreting sperm to the ducts during the process of ejaculatation
• when thinking about human male reproductive anatomy: penis and scrotum = external
• everything else = internal!

Question 13

Zoom in: Testis

Answer 13

Testis divided into two lobules: regions called seminiferous tubules

• seminiferous tubules = sperm is generated
• rete testis = site of partial maturation and sperm movement
• efferent ductule = carry sperm to epididymis
• epididymis: three parts; head and body of epididymis = process of maturation takes place as it goes down, tail of epididymis = sperm can be stored
• Vas deferens = muscular tube that’s going to pass upwards towards the spermatic cord

Question 14

How is the structure/form of the testis important for it’s function

Answer 14

the folding of the parts of the testis helps maximize surface area to create and store lots of sperm in that tiny space

Question 15

Zoom in: Ducts

Answer 15

-spermatic ducts = ducts prior to reaching urethra
ejaculatory duct = last duct prior to sperm entering urethra
urethra = where sperm travels down to leave penis
penis = have to know glans penis; prepuce and external urethral orifice (opening where sperm comes out from

Question 16

Zoom in: Accessory Glands

Answer 16

• Seminal Glands: release alkaline fluid (basic) that contains fructose, citric acid, and prostaglandins to increase sperm mobility or fertilizing capacity
• Prostate Gland: Encircling the urethra, and during ejaculation, the smooth muscle within the gland will contract, which will squeeze the secretions the prostate glands provide into urethra; associated in sperm activation
• Bulbourethral gland: secrete mucus that helps neutralize any acidic urine that will be left behind in the urethra; mucus can also lubricate gland penis during sexual excitation

Question 17

Human Female Reproductive Anatomy

Answer 17

• provides a space to not only make gametes (oogenesis) but also create an environment to grow fetus
• external system not included
• internal system included; ovaries and duct system

Question 18

Human Female Reproductive System

Answer 18

• Ovaries = female gonads
• In ovaries, there are follicles: each follicle has an immunite egg called oocyte; follicle will develop every month to be ejected; that is ovulation
• Oviduct (uterine tubes) = receive oocyte and oocyte will travel through it to get to uterus
• uterus = receive fertilized egg and provide an area where it can be nourished
• uterine wall= endometrium; portion of uterus that sheds during menstruation and also site if implantation if successful fertilization occurs and myometrium; bulkiest part, portion that will contract during childbirth
• Cervix = has mucus that plays a role in blocking spread of bacteria from vagina into uterus, block sperm entry, viscosity of mucus changes in order to permit sperm to pass through
• Vagina = site of menstrual discharge, site for penis and semen during copulation, where baby comes out, microbiota makes vagina pH acidic, this prevents infection from unwanted bacteria, keeps vagina healthy

Question 19

Mammary glands

Answer 19

lactating mammary gland and non lactating mammary gland look diff

• lactating mammary gland has lobes that will surround opening at nipples; lobes will have lobules that will have milk producing alveolus (which will occur during lactation)
• there will be suspensory ligaments found within breast tissue that is connective tissue that helps connect breast to underlying muscle
• milk passes through lactiferous ducts
• milk will accumulate in lactiferous sinus

-non lactating mammary gland: organization looks diff (like top part of image), size of breast tissue based on adipose tissue

Question 20

Gametogenesis and Spermatogenesis specifically

Answer 20

Gametogenesis: production of gametes

• for males, they go through spermatogenesis to form the sperm and spermiogenesis to mature the sperm to be used for future fertilization; maturation takes about 7 weeks
• lots of sperm is made daily!

Question 21

Mitosis vs Meiosis

Answer 21

Mitosis = parent cell making two daughter cells like itself; goes through duplication in S phase (but still same amount of chromosomes just double the amount of chromatin), the sister chromatids separate during anaphase and two daughter cells, both diploid are formed.
Meiosis: chromosome replication again, but this time tetrads are formed wig homologous chrosomes, those chromosomes exchange genetic info for variation and get split up into sister chromatids after Meiosis I that are both haploid, in Meiosis II, the sister chromatids split and 4 daughter cells are formed that are all diploid

Question 22

Spermatogenesis

Answer 22

• spermiogenesis occurs in seminiferous tubule
• spermatogonium are stem cells found along basement membrane of seminiferous tubule; there is version A, which will continue to be stem cells (go through mitosis) which is why men are always fertile after this process of spermiogenesis starts after puberty, version B will differentiate (not mitosis) into primary spermatocyte
• primary spermatocyte will go through meiosis I and form haploid cells, these haploid cells are secondary spermatocytes; they are differentiated bc of genetic variation via crossovers in meiosis I, and unique so the supporting cells will allow secondary spermatocytes to progress forward to the lumen and close behind them, allowing for a barrier to exist btwn them and the blood supply next to the tubule so that immune cells don’t attack it as foreign
• the 2 haploid secondary spermatocytes that are created after meiosis I will go through meiosis II and become 4 haploid daughter cells called spermatids
• spermatids will go through evolve and change (not the same thing as maturation) through the process of spermiogenesis
• as a result, sperm cells are formed and released into the lumen of the seminiferous tubule

Question 23

Spermiogenesis

Answer 23

Spermiogenesis is AFTER cell division and where spermatid (which is haploid) changes and develops into sperm cell (which is also haploid since it’s not going through mitosis or meiosis but simply evolving); this is not cell maturation but just changes to get it to be the sperm cell we know

• 1. spermatid has golgi apparatus, that will package acrosomal enzymes, and the acrosomal will form at the anterior end of the nucleus within the cell, with the centrioles found opposite from there
• microtubules (tubulin dimers that can extend) are responsible for forming flagellum
• will also be amplification of mitochondrial proteins and clustering of them that will be surrounding the mid-piece of sperm
• there will be shedding of excess cytoplasm bc we want to streamline and when excess cytoplasm not there = sperm cell

Question 24

Parts of the new formed sperm cell (after spermatogenesis and spermiogenesis)

Answer 24

Head- acrosome found at head portion of sperm cell and have hydrolytic enzymes which will assist sperm penetration into an egg; head region also contains genetic info so head considered genetic component of the sperm
-Mid-piece- area in which we have a lot of mitochondria which is used to provide metabolic energy in the form of ATP to use in oxidative phosphorylation; beneficial in giving sperm the energy to move through female reproductive system
Tail- contains flagellum; used for locomotion (to move)

Question 24

Parts of the new formed sperm cell (after spermatogenesis and spermiogenesis)

Answer 24

Head- acrosome found at head portion of sperm cell and have hydrolytic enzymes which will assist sperm penetration into an egg; head region also contains genetic info so head considered genetic component of the sperm
-Mid-piece- area in which we have a lot of mitochondria which is used to provide metabolic energy in the form of ATP to use in oxidative phosphorylation; beneficial in giving sperm the energy to move through female reproductive system
Tail- contains flagellum; used for locomotion (to move)

Question 25

Oogenesis (intro)

Answer 25

• development of a mature egg
• immature eggs form in female embryo but do not complete their development until years later and this completion is due to hormone levels changing

Question 26

Oogenesis

Answer 26

• oogonium is a stem cell that goes through mitotic devision and self renewal; upon significant amplification they will go into cell cycle arrest until birth
• oogonium at some point will differentiate into primary oocyte; all of them will turn into primary ooctye by 6 months after birth
• oogonium and primary oocytes are both diploid
• once primary oocyte is formed, will enter cell cycle arrest in prophase of meiosis I (so still diploid)
• any stage from primary oocyte to fertilization, can be called an egg or ovum
• large portion of primary oocytes that are generated will be degraded at numerous points, so by the time female hit puberty, millions of primary oocyte are reduced to half a million; but still ample opportunity for fertilization before the decline of the reproductive female system

Question 27

Continuation of oogenesis (starting at puberty)

Answer 27

• Your primary oocyte goes through meiosis I when puberty starts, and now it is haploid. There is a secondary oocyte and a first polar body
• After ovulation and fertilization occurs, meiosis II is completed and a now there is a fertilized egg and a second polar body
• the polar body is both rounds of meioses is to help get rid of excess genetic material

Question 28

oogenesis and ovulation

Answer 28

• ovary cortex is where we find the ovarian follicles- where oocyte will develop
• follicles will be functional unit of ovaries to provide an environment where oocytes can develop effectively and be able to communicate with nearby cells
• primary oocyte will be surrounded by follicular cells and have primary follicle
• once puberty occurs, secondary oocyte created, now is haploid and the follicle will mature and change in size in this step
• when ovulation occurs, and secondary oocyte exits out of surrounding follicle, follicle ruptures, which is a hallmark of ovulation phase
• the ruptured follicle is called a corpus lutem
• after secondary oocyte is now in uterus, there is two options for what corpus lutem does;
• if there is no fertilization event (so no meiosis II completed) egg dies, endometrium sheds (period), and corpus luteum will degenerate and leave hind scar tissue, which can be seen with each ovarian cycle
• if there is a fertilization event, and secondary oocyte goes through meiosis II and becomes fertilized egg and another polar body is created and discarded (still haploid), now the corpus luteum will be utilization with respect to hormone production, as it can release progesterone and estrogen, for a significant amount of time

Question 29

Comparison of Comparison of spermatogenesis and oogenesis
Keep in mind that transition from spermatid to sperm is spermiogenesis not spermatogenesis by definition
Spermatogenesis
A primary spermatocyte gives rise to 4 equal sperm
Spermatogenesis + spermiogenesis, we’re thinking about the shedding of cytoplasm to streamline and make a mature sperm cell more efficient for reaching its target cell
This can take many days for spermatogenesis (2 ½ months)
Number of gametes generated per mitotic division = 4
Ton more gametes that are generated from Spermatogenesis than oogenesis
Sustentocytes that will sustain Spermatocytes during Spermatogenesis
One sustentocytes can sustain many spermatocytes
Oogenesis:
Only producing one mature egg
Other components being generated are polar bodies that will die off
Emphasis is to produce a gamete with as much cytoplasm as possible bc we’re thinking about the role the cells going to play in terms of housing genetic content and having room for a ton of cell division for developmental bio
To go through process of oogenesis, that can take 13-50 years
Number of gametes generated per mitotic division = 1
Several pauses that occur during oogenesis, error rate significantly higher than in Spermatogenesis
Seems to be correlation between maternal age and error in fetal development
There are grandolycisis cells will sustain ONE oocyte
Many grandolycisis will sustain ONE oocyte

Answer 29

Comparison of spermatogenesis and oogenesis
(Keep in mind that transition from spermatid to sperm is spermiogenesis not spermatogenesis by definition):

Spermatogenesis=
-A primary spermatocyte gives rise to 4 equal sperm
Spermatogenesis + spermiogenesis, we’re thinking about the shedding of cytoplasm to streamline and make a mature sperm cell more efficient for reaching its target cell
This can take many days for spermatogenesis (2 ½ months)
Number of gametes generated per mitotic division = 4
Ton more gametes that are generated from Spermatogenesis than oogenesis
Sustentocytes that will sustain Spermatocytes during Spermatogenesis
One sustentocytes can sustain many spermatocytes

Oogenesis:
Only producing one mature egg
Other components being generated are polar bodies that will die off
Emphasis is to produce a gamete with as much cytoplasm as possible bc we’re thinking about the role the cells going to play in terms of housing genetic content and having room for a ton of cell division for developmental bio
To go through process of oogenesis, that can take 13-50 years
Number of gametes generated per mitotic division = 1
Several pauses that occur during oogenesis, error rate significantly higher than in Spermatogenesis
Seems to be correlation between maternal age and error in fetal development
There are grandolycisis cells will sustain ONE oocyte
Many grandolycisis will sustain ONE oocyte

Question 30

Review of Endocrine System and its connection to reproductive system

Answer 30

• endocrine system all about long distance communication via hormones getting released into bloodstream and traveling until they bind to their target cell to elicit a downstream response
• hypothalamus: refereed to as master regulator; connects to pituitary gland
• pituitary gland has both anterior pituitary and posterior pituitary
• hypothalamus is going to release GnRH (gonadotropin releasing hormones) via the portal blood in the portal system to the anterior pituitary gland.
• this will allow for anterior pituitary gland to release LH and FSH, which are luteinizing hormones and follicle stimulating hormones, that play a role in both gonads (testis and ovaries)
• the gonads then respond with release of sex hormones and inhibitin (for negative feedback regulation)
• the sex hormones will go to target cells and achieve downstream response based on which gonad it is
• once downstream response is made, negative feedback response will occur via inhibin and can inhibit the hypothalamus from sending GnRH or/and anterior pituitary from releasing LH and FSH
• The relationship btwn the diff components seen here is the hypothalamic pituitary gonadal axis, or HPG axis; this is the basic pattern of interaction and can be applied to diff responses depending on which system we are in

Question 31

Hormonal Control of the Male Reproductive system: an example of the HPG axis

Answer 31

• hypothalamus once puberty hits, will release GnRH i
• GnRH will release FSH and LH, and these two hormones will act on sertoli cells and leydig cells
• sertoli cells will produce inhibitin, to help regulate this process and inhibit the anterior pituitary gland when it is no longer needed
• leydig cells will produce testosterone, which help with the process of spermatogenesis in the testis and also play an inhibitory role for the hypothalamus and anterior once response is no longer needed to turn the response off

Question 32

hormonal control of female reproductive cycle- into

Answer 32

Cycles are going to be defined in female reproductive system as what type of changes we see

• for ovarian cycle, ovary changes
• for uterine cycle, uterus changes
• these have changes specific to uterus or ovary but also work together to support prep for potential pregnancy; and also how body responds when pregnancy does not occur

Question 33

Hormonal control of female reproductive cycles- example

Answer 33

using the HPG axis, when there is a high level of estradiol, this results in a positive feedback loop with the hypothalamus to produce GnRH, which stimulates anterior pituitary to release FSH and LH

• as a result, these pituitary gonadotropins will be released.
• FSH and LH stimulate the follicle to grow
• when a follicle is chosen for that months cycle, ovulation occurs (where egg is released into uterus) due to an increase in LH at around day 14 (in a 28 day cycle)
• this causes follicle to rupture and it turning into corpus luteum like we discussed earlier
• so now the egg is coming out of ovary and into uterus for potential fertilization due to increase in LH by anterior pituitary due to increase in GnRH due to hypothalamus, due to increase in estradiol, which causes a positive feedback loop to start this process of increasing LH and FSH to help follicle grow so that by day 14, one follicle is chosen and LH spikes for it to be released.

Question 34

continuation of hormonal control of female reproductive cycle

Answer 34

• the follicle releases estrodoil to cause a positve feedback response with hypothalamus and anterior pituitary for LH and FSH to be released
• LH and FSH cause follicle to grow (hence positive feedback loop with estradiol)
• when LH increases around day 14, ovulation occurs and follicle is ruptured and turns into corpus luteum and egg goes to uterus.
• This is the end of the follicular phase ^
• for the luteal phase, now it is focusing on the uterine cycle
• progesterone and estradiol is secreted by corpus luteum (the ruptured follicle), and is used to promote the thickening of endometrium now that egg is there.
• this helps promote thickening of endometrium, which helps with fertilization, as that is where fertilization occurs

Question 35

Uterine (menstrual) cycle

Answer 35

Menstrual phase: uterus will shed most of endometrium, hormones are low as endometrium is hormone dependent, decline in hormones will serve as an indicator and tissue will sloth off, and detach from uterine wall; which will result in bleeding and leave vagina as menstrual flow

Proliferative phase: growth and thickening of endometrium, this occurs due to estrogen (estradiol) rising and a new functional layer will be built

• glands will enlarge to increase in vascularization
• induction of cells of endometrium to synthesize progesterone receptors so that progesterone can bind as it also helps thicken endometrium
• cervical mucus changes (lessens) to help sperm come through
• ovulation will mark end of proliferative phase

Secretory phase: release of oocyte from ovary to uterus

• endometrium thickened
• accumulation of glycogen for possible implantation and secretion of nutrients into uterine cavity for future embryo
• progesterone rises and cervical mucus consistency changes; if fertilization occur, mucus will become thick and mucus plug will form to serve as barriers for other sperm and pathogens
• if fertilization has not occurred, then degeneration of corpus luteum, don’t have endocrine gland, then progesterone will decrease, which will lead to less hormone support and therefore leads to uterine cycle starting again into menstrual phase as endometrium sheds

Question 36

Menopause

Answer 36

after certain amount of cycles, human females go through menopause

• cannot achieve cyclical hormone changes anymore, so feedback loop that occurs is no longer there
• diff changes that occur bc of low levels of estrogen (as w/o it, there is not positive feedback loop with hypothalamus, which means no downstream events from that)
• results in changes in vaginal secretions, vasodilation of skin blood vessels (hot flashes), loss of bone mass

Question 37

Human sexual response

Answer 37

Focus on 4 phases same in both male and female but differences with the phases, but not going to talk about distinctions

Two reactions in both sexes:	
Vasocongestion 
Swelling with tissue with blood
Myotonia
Increased muscle tension 

4 phases in sexual response cycle:

Excitement phase characterized by vasocongestion and myotonia
In addition, increase in heart rate, blood pressure, breathing (pulmonary ventilation)
Broad spectrum in excitement phase can be initiated
Ranges from person to person

Plateau: things that are variable from excitement phase (blood pressure, heart rate) will remain at a high level or even increase slightly prior to entering orgasm phase

Orgasm: intense but short lived phase

Resolution:
Cardiovascular and respiratory functions are returning to normal

Question 38

Specific events from egg to embryo

Answer 38

• this is for internal fertilization and development happens internally as well with the use of a placenta (blood supply that helps provide nourishment)
• specific events in which egg transitions to embryo; we will go through those now

Question 39

Fertilization

Answer 39

1. sperm undergoes capacitation as they migrate to the oocyte; this makes sperm capable of penetrating the egg
   - sperm have cholesterol on membrane that protects the sperm from releasing the enzymes too early as that would cause enzymatic breakdown where it shouldn’t be (like in male reproductive tract)
   - the enzmyes need to be used when entering female reproductive tract to be broken down
2. acrosomal reaction releases enzymes from head of the sperm, which breaks down granulosa cells in the zona pellucida that surrounds oocyte
   - the sperm to reach the egg isn’t the one that fertilizes it, it helps clear a path for another sperm cell to successfully interact
   - we have exocytosis in the acrosomal reaction to release those penetrating enzymes; ex one that digests HCl that binds the ganulosas together

• we want to avoid anything that will increase that ploidy, such as polyspermy; where they is too much sperm binding to the egg that would result in triploidy/inappropriate amount of genetic material
• as a result there are two mechanisms to make sure that when step 3. the sperm binds to the plasma membrane of the oocyte occurs, that will be the only sperm entering; fast block and slow block
• fast block: sperm binding results in influx of sodium ions which leads to depolarization of a membrane, which leads to the inhibition of additional sperm attachment to egg
• slow block: sperm penetration can release calcium ions which stimulates cortical reaction, which causes a fertilization membrane to occur, creating a barrier btwn egg and zona pellucida (this is step 4 to have this cortical reaction to prevent any other sperm from binding to egg via calcium ions)
• as the sperm enters, only head makes its way in, which is the genetic component
• this means mitochondrial DNA is from mom as that is in sperm mid piece which gets left behind and doesn’t enter egg
• sperm nucleus goes through change from sperm nucleus to male pronucleus; swelling occurs, microtubules spread to push sperm pronucleus towards center of the egg
• the secondary oocyte, as now fertilization has occurred, can finish meiosis and shed excess genetic material via a polar body; oocyte will also swell and female pronucleus is created
• this is a mitotic spindle that will form btwn both pronuclei and eventually rupture which will allow chromosomes of the two gametes to come together as the single diploid set

Question 40

Cleavage and Blastocyst Formation

Answer 40

• this is the early events that take place in embryonic development
• after fertilization occurs (i think in fallopian tube/uterine tube), process of cleavage will occur; cleavage = mitotic division as it goes down uterine tube
• this mitotic division is different as it doesn’t result in growth alongside the division; the size of fertilized egg isn’t changing, small cell are being formed inside of it during cleavage
• benefit = surface to volume ratio for exchange of nutrients, oxygen, and waste to take place more effectively as there’s lots of cells close together in egg so its more efficient

First cleavage: produces two cells, referred to as blastomeres
-blastomeres will continue to divide, there will be 4 cell stage, 8 cell stage, and will reach 16 cell on day 3, which is the morula stage

Morula stage, is when it is close to the embedding into uterine wall
-if morula splits into masses, and both implant, the result is identical twins
(fraternal twins is two different egg cells being fertilized by two diff sperm cell; genetically distinct from one another)
-when looking at morula, perimeter is starting to change qualitatively; the perimeter, which is the zona pellucida degenerates

-when we have that break down fully of the zona pellucisa, it turns into blastocyst

Blastocyst stage: hallow sphere at day 4 (day 3 is morula)
-composed of 2 cell types; flattened cell (trophoblast) and slightly rounded cells (inner cell mass)

Question 41

Implantation:

Answer 41

process of implantation in which blastocyst attaches to the endometrium
-blastocyst is going to have trophoblast cells separating into two layers; sychytiotrophoblast and cytotrophoblast

Sychytiotrophoblast: will form fused multi nuclear mass, can’t discern one cell from another, grow into uterus, extending roots and digest endometrial cells
-endometrial cells will respond by growing over blastocyst and covers it so that eventually the blastocyst is buried into endometrial tissue

cytotrophoblast: retain cell like properties and are the innermost layer of cells

during this time, there will be erosion of endometrium, which will produce blood filled lucunae areas in which there will be intervillous spaces within that functional layer (eventually turn into one lucanae and help with vascularization btwn mother and fetus)

We consider blastocyst to be fully implanted, when it is surrounded by uterine tissue

Question 42

Placental Circulation

Answer 42

Placenta is rich in blood vessels; blood vessels that have both maternal and fetal in nature; these are in close proximity to each other for an exchange to take place

There will be chorionic villus (which has fetal capillaries); this will have high level of folding to maximize surface area
-there will be capillaries there where we can have nutrient exchange gas exchange, and other solutes

Nutrients and O2 from mother will be carried by maternal arteries

• from there, the blood will pool in large area of the fetal placenta that surround fetal capillaries
• diffusion will be based on concentration gradient, so solutes from maternal blood go to fetal capillaries, and from there go to umbilical vein

Waste and CO2 travel from fetus through umbilical artery to the placenta, and then diffuse into maternal circulation

Bc of this movement of nutrients of waste, there is not explicit mixing of maternal and fetal blood; which is why RH incompatibility with blood type doesn’t happen with first child as blood mixing only happens at childbirth and at that point fetus is already exiting out womb, but then for second child antibodies will already be created and in the maternal blood so I think it can diffuse in as well or maybe during that childbirth it will attack

Question 43

Maternal Changes

Answer 43

Non pregnant female: uterus is size of fist, mammary glands are rudimentary

In pregnancy, there is a transition with respect to mammary glands; as time progresses, changes in lobules, lactation and sinus

When looking at progression from 4 to 9 months, uterus expands and changes as fetus size changes

Towards the end of gestation, size fo fetus is pressing down on bladder and take up space close diaphragm; which is why they have to pee often as space in bladder diminished and also why there’s limitation with respect to breathing as diaphragm plays a role in thoracic cavity

Increase in blood volume, can increase pressure in lower extremities, increase likelihood of varicose veins

Hormonal fluctuation can impact digestive system (ex. nausea)

every woman is diff, but one thing you do expect in a successfully growing fetus is a change in size as time progresses, and as size increases, increase in stress on diff areas of mothers body

Post birth: most things will go back to normal (uterus never fully goes down)

Question 44

Positive Feedback in Labor

Answer 44

Labor = positive feedback mechanism; should occur when gestation ends
-childbirth initiated by fetus

Release of estradiol from ovaries; which will help activate oxytocin receptors on the uterus and increases prostaglandins

Impact of oxytocinL released from both fetus and mother posterior pituitary; oxytocin will help with contraction of the myometrium, which is one of the layers within the uterine wall

• this uterine contractions helps stretch cervix, which can promote more contractions (positive feedback loop!)
• oxytocin can also stimulate placenta to make prostaglandins, and can result in more contractions of the uterus

All of these contractions keep going as long as there’s stimulus (baby coming out = stimulus), until baby leaves birth canal

We want the hormones are play in eliciting uterine contractions to be positive feedback loop as we want to initiate contractions in myometrium (which causes cervix to expand) until fetus is born!

Question 45

The Three Stages of Labor

Answer 45

Stage one: dilation of cervix

• longest stage
• if first time giving birth was not induced, second time this process can be shorter (induce = induce body to go through stages of labor either synthetically or chemically)
• when it comes to dilation stage, there will be widening of cervical canal to max diameter of 10 cm (like babies head)
• fetal membranes often rupture, and amniotic fluid discharged at this time = water breaking

Stage 2 = expulsion stage

• short
• 30 min to an hour, if second child, time is reduced
• expulsion stage = time from the head entering the vagina until baby is expelled entirely
• head is hardest part to come out, rest of the body will shift in a way to come out easier
• episiotomy may be performed, which is an incision to widen vaginal canal, or may opt for natural tearing to be utilized if it occurs at all

Third stage = placenta stage

• still has continued contraction of uterus even after baby has been expelled
• need to ensure that placenta, amnion, and other fetal membrane is entirely removed
• there might be slight pulling of umbilical cord to achieve that
• it is important for mother to be inspected to make sure everything is out bc if there’s anything remaining, can lead to postpartum hemorrhaging

Question 46

Maternal Immune Tolerance of the Embryo and Fetus

Answer 46

When it comes to the mechanisms a woman goes through with the fetus not being foreign to her is not properly understood

• but it is thought that the woman is in an immunosuppressed state
• this would make sense as autoimmune disease less severe during pregnancy, as that would be amplification, and also pregnant woman get sick easily, as immune system is suppressed

Question 47

Temporary methods of birth control

Answer 47

A. male and female condoms
Example of barrier methods
Designed to prevent sperm from getting into vagina or beyond vagina
Most effective when used with chemical spermicide
Male condom: composed of latex or rubber, or animal membrane like lamb intestine
Way in which seme can be collected to be prevented from entering vagina
Inexpensive, pretty reliable when used conveniently and accurately
¼ of Americans use contraceptive ONLY
Ranked second to birth control pills
Female condoms: less used
Composed of a polyurethane cheth with a flexible ring that is seen at either ends
When it comes to female condom, sometimes be more difficult with respect ot application and insertion
Male and female condoms only contraceptives that can also protect against disease transmission
Animal based condoms seen in male condoms: those are porous to HIV and to hepatitis B virus
Not be utilized as a means of protection for these particular diseases
Female specific barriers:
B) Diaphragm, cervical cap, and sponge:
These methods can block cervix so that sperm cannot pass into uterus
The efficacy can be increased through application of spermicide
C) Spermicide:
Something that can trap and kill sperm
Popular versions through disrupting plasma membrane
Spermicide all by itself is not a good protective option bc it has a pretty high failure rate, so it should be used in conjunction with A or B
Some condoms will come with spermicide already applied
Hormonal methods:
Goal with a hormonal method is to inhibit process of ovulation, can be achieved by suppression of gonadotropin, without FSH and LH we can prevent follicle maturation, estrogen levels won’t rise, there’s no LH surge, no ovulation
D) oral contraceptives
Can be composed of estrogen and a synthetic version of progesterone and progestin
Typically 28 pack in which 7 of the pills will lack the hormones
Lack of hormones will allow for menstruation to occur during 7 day window
Oral contraceptives mimic pregnancy so that ovarian cycle and ovulation are temporarily suspended
G) IUD
Stands for intrauterine device
Springy T shape devices inserted through cervical canal into the uterus
Some IUD act by releasing synthetic progesterone
But others have copper wire wrapping/copper sleeve
IUD irritates the uterine linings and interferes with the process of implantation
Copper IUDs can inhibit sperm motility
IUD can b left for a long time

Question 48

Abortion

Answer 48

Abortion can be termination of pregnancy once fertilization has taken place
Spontaneous abortions = miscarriages
⅓ of all pregnancies
Some of them are bc organism releasing there is going to be aneuploidy or successful fertilization has occurred
Drugs that can do this same idea
Non surgical procedure
Creates an inhospitable for blastocyst implantation
As a result, the uterine lining is going to be shed and in doing so there’s not going to be anything for the blastocyst to implant itself into and receive nutrients from

Question 49

Modern Reproductive Technologies- IVF

Answer 49

In vitro = example of reproductive technology which has the capability to helping to assist individuals that deal with fertility
On both male and female side
IVF, external fertilization followed by an embryo transfer
Eggs and sperm within poultry dish and embryo gets returned to uterus at around 8 cell stage (before blastocyst)
From there uterus will take over
Not like dolly the lamb as far as set up but similar in the sense that we are manipulating something outside of the organism and adding it back into the individual that’s capable of carrying that cell
Downside: multiple births are pretty common as they will transfer more than one embryo as the goal is to ensure that at least one implants and develop normally