Module 2: Reproductive Physiology Flashcards
1
Q
what are primary reproductive organs called
A
gonads
2
Q
how is genetic sex determined
A
by the combo of sex chromosomes at conception
- gametes are produced via meiosis in which diploid parent cells divide to produce haploid gamete cells (sperm and ova). half sperm carry an X, while the other half carry a Y chromosome
- when these 2 haploid cells combine, they create a fertilized ovum w 2 sets of 23 chromosomes (46 total)
- sperm carrying an X chromosome gets fertilized the embryo will b XX, which is female
- XY is male
3
Q
what is meiosis
A
specialized germ cells undergo meiosis to produce 4 daughter cells with only a single set of genetic info or 23 unpaired chromosomes. involves meiosis 1 and meiosis 2.
4
Q
what is meiosis 1
A
1st division of meiosis, replicated chromosomes containing a identical pair of chromatids, sort themselves into homologous pairs before separating so each daughter cell receives a single set of chromosomes (or one homologue from each pair)
results in 2 daughter cells w a single set of chromosomes, each containing a pair of sister chromatids
5
Q
what does prophase 1 have
A
1 diploid cell
6
Q
what does metaphase 1 have
A
1 diploid cell
7
Q
what does anaphase 1 have
A
1 diploid cell
8
Q
what does telophase 1 have
A
2 haploid cells
9
Q
what is meiosis 2
A
2nd division, the sister chromatids within the chromosomes of each of the daughter cells separate and are distributed to 2 cells
result is 4 daughter cells each containing a single set of chromosomes containing 1 chromatid each
10
Q
what does prophase 2 have
A
2 haploid cells
11
Q
what does metaphase 2 have
A
2 haploid cells
12
Q
what does anaphase 2 have
A
2 haploid cells
13
Q
what does telophase 2 have
A
4 haploid cells
14
Q
how is the gonadal sex determined
A
by the presence or absence of a Y chromosome
- 1st 6 weeks of gestation, the reproductive sys of male and female embryos are identical
- around week 7 of preg, the sex-determining region of the Y stim the production of H-Y antigen, which acts on the gonads to differentiate into testes
- absence of H-Y antigen, the gonads differentiate into ovaries
15
Q
how is the apparent (phenotypic) anatomical sex of an individual decided
A
dependent on the gonadal sex
- w undifferentiated gonads, embryos of both sexes have the potential to develop either male or female external genitalia and reproductive tracts
- in presence of androgens secreted by the developing testes male-type reproductive sys are developed
- the absence of androgens results in a female-type reproductive system
- external genitalia develop from the same embryonic tissue, the reproductive tracts do not
16
Q
in the undifferentiated embryo’s what are the 2 primiltive duct systems
A
the wolffian, and mullerian ducts
17
Q
what are wolffian ducts and how are they stim
A
- placenta secretes hCG
- if testes are present, hCG stim them to produce and secrete testosterone
- that testosterone will stim these to develop into the male reproductive sys
- testosterone is converted to dihydrotestosterone, responsible for developing male external genitalia
- testes secrete mullerian-inhibiting factor, causing degradation of the mullerian ducts
18
Q
what are mullerian ducts, how to they develop
A
- in absence of testosterone, wolffian ducts degrade and mullerian ducts develop into female reproductive tract + external genitalia
19
Q
w/o the addition of _______, all fetus’s would be feminized due to high levels of female sex hormones during gestation
A
testosterone
20
Q
when do the testes descend
A
- into the scrotum in the last months of fetal life
- majority of premature male babies, the testes will descent in early childhood
- should they remand undescended into adulthood, this is called cryptorchidism and results in sterility
however in some cases this does not occur
21
Q
location and function of testes
A
- primary roles of the testes, spermatogenesis
- temp within the scrotum avgs several degrees celsius less than normal body temp
- descent of testes into this cooler environment is essential bc spermatogenesis is temp sensitive and cannot occur at normal body temperature
22
Q
what happens when the testes are too cold for spermatogenesis
A
the scrotal muscles (the cremaster muscle and the dartos muscle) contract to bring the testes closer to the body to gain heat
23
Q
what happens when testes are too hot for spermatogenesis
A
the scrotal muscles relax to move the testes away from body
24
Q
where in the testes is sperm produced
A
the testes majority consist of coiled seminiferous tubules in which sperm are produced
25
what secretes testosterone
in connective tissues, between the seminiferous tubules are Leydig cells
- when secreted by this some testosterone enters the bloodstream and circulates to distant target cells
- most testosterone enters the lumen of seminiferous tubules where it supports sperm production
26
what is testosterone's effects before birth
causes masculinization of the reproductive tract and external genitalia as well as the descent of testes into the scrotum
27
testosterone effects on sex-specific tissues after birth
maintains the reproductive tract throughout adulthood, promotes spermatogenesis, and promotes maturation of the reproductive system at puberty
28
testosterone effects on other reproductive effects
develops sex drive at puberty and controls the secretion of gonadotropin hormone
29
testosterone effects on secondary sexual characteristics
voice deepens, development of male pattern of body hair, promotion of muscle growth (protein anabolism)
30
testosterone non-reproductive actions
promotes bone growth at puberty and plays a role in the closing of the epiphyseal plates. may also induce aggressive behaviour.
31
what are the seminiferous tubules
within testes are highly-coiled seminiferous tubules which are the location of spermatogenesis
majority are composed of: germ cells and Sertoli cells
32
what is spermatogenesis the process of
process in which diploid (46 chromosomes_ primordial germ cells are converted into motile sperm cells with a haploid (23 chromosomes) set of chromosomes
33
what are the 3 steps of spermatogenesis
1. mitotic proliferation
2. meiosis
3. packaging
34
what is mitotic proliferation
- primordial germ cells are called spermatogonia, located on outermost layer of seminiferous tubules
- these cells continuously undergo mitotic division to create a supply of new germs cells
- after each division, 1 daughter cell remains at outer edge while others start to migrate towards lumen of tubule
- sperm-forming daughter cell will undergo mitotic divisions twice more to produce 4 identical primary spermatocytes that enter resting phase in prep for meiosis 1
35
what is meiosis
- each primary spermatocyte forms 2 secondary spermatocytes (each w 23 double stranded chromosomes)
- in meiosis 2, each secondary spermatocyte results in 2 spermatids, w 23 single stranded chromosomes (after this there are no further divisions)
- for each spermatogonia, 16 spermatids can be produced
36
what is the packaging phase
- final maturation of spermatids into spermatozoa
- cells are stripped down of all non-essentials such as the cytosol and most organelles
37
what are the four parts of a mature spermatozoa
(make sure to take a look at the diagram of sec 2 slide 10)
- head (consists of the acrosome and the nucleus)
- midpiece (consists of the mitochondria)
- tail also known as the flagellum (consists of the microtubules
38
what is the head of the mature spermatozoa
consists of the nucleus
39
what is the acrosome of a mature spermatozoa
enzyme-packed vesicle at the tip of the head that is needed to penetrate the ovum
40
what is the midpiece of the mature spermatozoa
packed full of mitochondria to provide energy for locomotion
41
what is the tail (flagellum) of a mature spermatozoa
movement of this provides propulsion (a process that requires lots of ATP)
42
1. what do sertoli cells make up
2. how are they connected, and what happens during the process of spermatogenesis to the developing sperm cells
3. what happens to developing sperm cells by the sertoli cells
1. a single layer of these cells makes up the walls of the seminiferous tubules
2. connected by tight junctions, but during the process of spermatogenesis, developing sperm cells pass between them as they migrate towards the lumen
3. developing sperm cells are engulfed in Sertoli cells as they migrate towards the lumen where the sperm head remains embedded until it is mature
43
what are the 6 functions of Sertoli cells for spermatogenesis
1. tight junctions exist between Sertoli cells form, they form the blood-testes barrier. for a substance to reach the intratubular fluid it must pass thru these cells, this allows them control of the intratubular environment optimal for developing spermatozoa
2. nourish sperm cells
3. absorb developing sperm cytoplasm and remove any defective germ cells
4. secrete seminiferous tubule fluid into lumen to flush released sperm into epididymis for storage
5. secrete androgen-binding protein that helps to concentrate testosterone in the lumen
6. site of action for testosterone and FSH to regulate spermatogenesis
44
what are the 2 hormones that control the testes
LH and FSH
44
in males what does LH, FSH, testosterone, GnRH, and inhibin do?
LH: stim the Leydig cells to secrete testosterone
FSH: acts the Sertoli cells to stimulate spermatogenesis and to secrete inhibin
Testosterone: has a direct negative-feedback pathway at the level of both the hypothalamus to decrease GnRH release and at the anterior pituitary to decrease LH and FSH release
inhibin: released by the Sertoli cells feeds back to the anterior pituitary to decrease FSH release
45
what does the male reproductive tract consist of
the epididymis and ductus deferens, the accessory sex glands, and the penis
46
what are the epididymis and ductus deferens
sperm are produced in the seminiferous tubules, they are swept into the epididymis which is a tightly coiled tube around 5m in length. sperm enter the epididymis they are not motile, mainly due to the low pH in this region. epididymal ducts from each testis converge to form the ductus deferens, and the ductus deferens of each testis empties into the urethra. sperm can be stored for months here.
47
what are the 3 male accessory sex glands and what do they do
1. seminal vesicles
2. prostate gland
3. bulbourethral glands
these make secretions make up the bulk of semen, and they provide support for the continuing viability of sperm inside the female reproductive tract
48
what are the seminal vesicles
- one empties into each of the ductus deferens just before the urethra
- purpose is to provide the bulk of semen, supply fructose as an energy source for ejaculated sperm, secrete prostaglandins to cause smooth muscle contractions in both male and female reproductive tracts, and to secrete fibrinogen
49
what is the prostate gland and what are its 2 primary purposes
- large gland that surrounds the ejaculatory ducts and urethra
1. to secrete an alkaline fluid to neutralize the acidic environment of the vagina
2. secretes clotting enzymes which act on the fibrinogen from the seminal vesicles to produce fibrin, which clots the semen and keep it within the female reproductive tract
50
what are the bulbourethral glands
- aka Cowper's glands
- pair of glands that both empty into the urethra, one on each side, before the urethra enters the penis
- secrete a clear substance during secual arousal and this fluid helps to lubricate the urethra for sperm to pass through
51
describe oogenesis
1. primordial germ cells in ovaries undergo mitotic division during fetal life. by 5th month of preg, the oogonia have divided to give rise to 6-7 million primary oocytes. processes ceases w the primary oocytes arrested prior to 1st meiotic division. each primary oocyte is surrounded by a single layer of granulosa cells (structure called a primordial follicle). primary oocytes start to decay such that by birth only 2 mill primordial follicles remain. represents the entire complement of potential ova a women will have throughout her entire life.
2. primordial follicles give rise to ongoing tricke of developing follicles when follicle begin development, entire structure is called a primary follicle. developing primary follicle either results in the release of an ova, or it will undergo atresia and decay. after puberty only about 400 primary follicles will mature and release ova.
3. from puberty -> menopause only a small fraction of primary follicles will develop into secondary follicles on a cyclic basis. primary follicles get larger due to cytoplasmic materials that would be necessary for early embryonic development. just before ovulation, the primary oocyte undergoes its first meiotic division to produce 2 daughter cells, each w 23 pairs of chromosomes. during this division the majority of the cytoplasm goes to one of these daughter cells, called the secondary oocyte. other daughter cell forms the first polar body which will eventually degenerate.
4. secondary oocyte is release during ovulation. if fertilized, will undergo the 2nd meiotic division in which 23 SS chromosomes form the second polar body, while the remaining 23 SS chromosomes combine w the 23 single stranded chromosomes from the sperm.
52
what does the ovarian cycle do
occurs in ovaries and prepares an ova for release (contains the follicular phase, ovulation, and the luteal phase)
53
what is the uterine cycle
prepares the uterus for implantation
(includes menstrual, proliferative, and secretory phase)
54
what is the follicular and luteal phases
follicular: prepares a mature egg. lasts for the 1st 14 days of the ovarian cycle.
luteal: prepares reproductive tract for potential implantation. cycle on average lasts 28 days.
55
what are the 6 steps of follicular phase
1. begins w proliferation of granulosa cells in a primary follicle. granulosa cells divide to form several layers around the oocyte.
2. granulosa cells secrete glycoproteins that from a thick extracellular matrix that surrounds the oocyte and separates it from the granulosa cells. membrane is known as the zona pellucida. while granulosa cells are proliferating, specialized ovarian connective tissue cells differentiate and surround granulosa cells w a layer of thecal cells. thecal and granulosa cells are known as follicular cells. development of this primary follicle is due to the influence of FSH and estrogen.
3. as follicle enlarges, it becomes a secondary follicle which is capable of secreting estrogens, primarily estradiol. formation of the secondary follicle is mainly due to FSH and estrogen.
4. also during that stage, a fluid filled cavity known as an antrum is formed within the granulosa cells. expansion of the antrum increases the size of the follicle as it matures. estrogen secretion also increases.
5. each cycle, 1 follicle develops faster into a mature follicle by around 14 days. in the mature follicle, the oocyte has undergone its first meiotic division to become a secondary oocyte. also at this time, the location of the oocyte is not central in the follicle, but rather to the side of the growing follicle.
6. under the influence of LH and FSH, ovulation occurs around day 14. ovarian follicle ruptures to release the ovum into the abdominal cavity. leaking antral fluid helps push the ovum into the oviduct. the release of the ovum represents the end of the follicular phase.
56
what are the 2 stages of the luteal phase
1. once ovum has been released, the remaining follicular cells undergo a process called luteinisation to form the corpus luteum. corpus luteum becomes highly vascularized and it becomes very active in secreting hormones, mainly progesterone w some estrogens.
2. within around 14 days the ovum is not fertilized and implanted, the corpus luteum degenerates to form the corpus albicans, which is a fibrous scar tissue. this signifies the end of one ovarian cycle and the follicular phase begins again.
57
what 3 hormones is the ovarian cycle under control of
FSH, LH, estrogen
58
what are the actions of the LH surge
- it stops estrogen synthesis by follicular cells
- it reinitiates meiosis in the oocyte
- it triggers release of local factors that increase the swelling of the follicle and weaken the wall
- it differentiates the follicular cells into luteal cells
59
what causes the LH secretion
as estrogen levels continue to rise, estrogen then exerts a positive feedback action on the anterior pituitary to cause a surge in LH secretion
60
during the luteal phase what does the corpus luteum begin secreting
begins secreting large amounts of progesterone in preparation of a potential pregnancy
progesterone causes changes in the uterine lining to prepare for potential implantation of an embryo to establish a pregnancy
if no implantation occurs, the rapid degradation of the corpus luteum results in a rapid drop in circulating progesterone
61
how long does the uterine or menstrual cycle last
around 28 days
62
what are the two layers of the uterus
the myometrium, and endometrium
63
what is the myometrium
outer layer comprised of smooth muscle
64
what is the endometrium
the inner lining that is highly vascularized and also has many glands
65
what are the 3 phases of the uterine cycle
1. menstrual phase
2. proliferative phase
3. secretory phase
66
what is the menstrual phase of the uterine cycle
w decreased estrogen at the end of the luteal phase, the endometrial growth ceases. the decrease in estrogen and progesterone results in the local release of prostaglandins. these prostaglandins constrict the blood supply to the endometrium and cease the myometrium to rhythmically contract. the endometrial lining sloughs off and is expelled out thru the vagina.
67
how long is menstruation? what happens during this time with follicles?
5-7 days
newly developing follicles are secreting enough estrogen to begin repair of the endometrium
68
what is the proliferative phase of the uterine cycle
begins when menstrual flow ceases, coincides w the later stages of ovarian follicular phase. @ end of menstrual phase, the endometrium consists only of a few layers of cells (1mm). w estrogen, these cells proliferate and there is an ingrowth of glands and blood vessels until the lining is 3-5mm thick. ovulation occurs now, ovum leaves ovary and begins travelling thru oviduct towards uterus.
69
what is the secretory phase of the uterine cycle
w formation of the corpus luteum + beginning of ovarian luteal phase, this begins. large amounts of progesterone and estrogen convert the endometrium into a richly vascularized and glycogen-filled tissue necessary to support an early embryo. by this phase, the ovum has made its way to the uterus. w/o implantation, the corpus luteum degrades and triggers the next menstrual phase.
70
what is menopause
rep the end of reproductive capacity, when there are no more viable primary follicles in the ovaries and follicular growth stops and ovarian and uterine cycle ceases.
- causes a dramatic decrease in estrogen
- this affects many things; most notably estrogen helps to promote strong bones by inhibiting osteoclast activity. causes bone decay, and can result in osteoporosis in pts.
71
how does an erection during sex work
erection: is when the penile tissue fills w blood allowing the penis to become rigid and permits it's entry into the vagina
the erectile tissue is made up of 3 columns of sponge-like vascular spaces, this is known as corpora cavernosa
during arousal, the arterioles supply these vascular spaces dilate. the penis enlarges and becomes rigid.
72
male sex act involves:
erection and ejaculation
73
what is the erection reflex
thoughts about sec or stim of mechanoreceptors in glans penis initiate erection reflex. this is a spinal reflex, and the erection generating centre lies in the lower spinal cord
74
what are the 3 main actions to activate the erection reflex
1. inhibiting the SNS supply to penile arterioles. this removes the tonic vasoconstrictor actions of the sympathetic sys.
2. activates the PSNS supply to penile arterioles to cause vasodilation via a NO-medicated mechanism
3. activates the PSNS supply to the bulbourethral glands to secrete mucus for lubrication
75
describe ejaculation
is a spinal reflex mediated by the same tactile and psychological stimuli as for erection. mediated by the same tactile and psychological stim that cause erection
76
describe and name the 2 stages of ejaculation
1. emission: increased SNS activity causes smooth muscle contractions in the prostate, reproductive ducts, and seminal vesicles. timing is coordinated such that prostatic fluid, then sperm, then seminal vesicle fluid is delivered into the urethra. this mix is called semen. the sphincter at the neck of the bladder also contracts to prevent urine release.
2. the filling of the urethra w semen triggers activation of skeletal muscles at the base of the penis. this increases the pressure and forcibly expels semen. the changes in pressure within the urethra forcibly expels the semen.
77
what are the 4 stages of the male sexual response and describe them
1. excitement phase: includes heightened sexxual awareness and erection
2. plateau phase: has more generalized responses such as increased HR, bp, RR
3. orgasmic phase: includes ejaculation as well as other physical and emotional responses
4. resolution phase: return of body to pre-arousal stage
78
what happens once ejaculation has occured
a temporary refractory period occurs in which further secual stim cannot trigger another erection
79
does the female sexual response cycle have the same 4 phases as the male sexual response?
yes
80
describe the female sexual response cycle steps
1. excitement: stim of clitoris and surrounding area activates spinal reflec activating PSNS sys to dilate arterioles throughout vagina and external genitalia. nipples also become erect and there is an increase blood supply to skin. the clit, contains erectile tissue + becomes erect. dilation of arterioles in vaginal walls causes vasocongestion of capillaries, forcing fluid out of vessels and into vagina. this fluid, w secretions from Bartholin's gland is the lubricant for sex.
2. plateau: uterus raises upward, lifting the cervix and enlarging the upper portion of the vagina. this tenting effect creates space for ejaculated semen. RR, HR, and bp increase.
3. orgasm: if erotic stim continues, sexual response culminates in orgasm, as SNS impulses lead to rhythmic contractions of pelvic musculature. no female equivalent to ejaculation.
4. resolution: post orgasm, HR, bp, RR return to normal. phase is marked by general sense of well-being, enhanced intimacy, and fatigue. some women are capable of rapid return to plateau phase w further sex stim.
81
what are the 4 stages of fertilization
1. ovum transport to the oviduct
2. sperm transport to the oviduct
3. fertilization
4. implantation
82
how does the ovum transport to the oviduct
ovum is released into abdominal cavity. at the end of the oviducts is fimbriae. fimbriae guide ovum into oviduct and contractions move ocum to ampulla.
83
how does sperm transport to the oviduct
after being deposited in vagina, 1st barrier sperm face is the cervical canal. under influence of progesterone, cervial mucus is very thick and prevents sperm from passing thru canal. high levels of estrogen at ovulation cause mucus to become thin enough to allow sperm passage. consequently, passage of sperm into uterus is limited to only a few days/month and coincides w ovulation. once in uterus, myometrial contractions disperse sperm to ampulla. they arrive approx 30 min after ejaculation
84
describe fertilization
once ovum + sperm are in ampulla fertilization can occur. for this to happen, sperm must be able to penetrate both the corona radiata and zona pellucida. sperm penetrates by membrane-bound enzymes on its head. plasma membrane of sperm contains protein called fertilin, which binds to ZP3, a glycoprotein on the outer layer of zona pellucida. binding causes acrosome membrane to be disrupted and releases acrosomal enzymes. the 1st sperm to reach fuses, head first. this triggers release of intracellular Ca2+. within an hr, sperm and ovum nuclei have fused
85
what does the release of intracellular Ca2+ during fertilization cause
- inactivation of ZP3 so no more sperm can bind to zona pellucida
- it hardens the zona pellucida so no sperm can penetrate
- triggers the 2nd meiotic division in ovum
86
true/false:
sperm start to arrive in ampulla 30 min following ejaculation
true
87
true/false:
the zygote remains in ampulla for a few hrs
false
88
true/false:
the release of intracellular Ca2+ in ovum causes zona pellucida to harden
true
89
true/false:
fertilization normally happens in endometrium of uterus
false
90
true/false:
after implantation, the corpus luteum is secreting large amounts of estrogen which helps to relax the oviduct and allow the morula to move to the uterus.
false
91
how do identical twins occur
when a single egg is fertilized w a sperm cell, forms 1 zygote, and then spontaneously divides into 2 separate embryos
92
how do fraternal twins occur
after 2 eggs are released from the ovary. both eggs are fertilized by 2 different sperm cells, which are implanted in the uterine wall at the same time.
93
describe the development of the placenta
4 weeks: by day 12 embryo is completely embedded in endometrial tissue at implantation site. tissue contributes to development of the placenta.
8 weeks: not fully developed, but well established and operational by 5 weeks after implantation.
12 weeks: development of maternal blood supply to placenta is complete by end of 1st trimester of pregnancy (12-13 weeks). at this point, the placenta has developed all necessary structures to support the embryo for remainder of pregnancy.
40 weeks: once fully developed, placenta continues to grow throughout pregnancy. functions as digestive sys, respiratory sys, and kidneys of fetus. exchange of nutrients and wastes between maternal and fetal blood occurs across the thin barrier that is the placenta.
94
what are the placental hormones?
1. human chorionic gonadotropin (hCG)
2. estrogen
3. progesterone
95
what does hCG do in the placenta
- 1st hormone secreted by the developing placenta
- is a peptide hormone similar to LH, and can bind to LH receptors
- hCG stim and maintains the corpus luteum
- thus the corpus luteum gets larger and becomes the primary source of estrogen and progesterone until the placenta takes over at around 10 weeks of gestation. once placenta secretes sufficient estrogen and progesterone, hCG secretions decrease to a low and steady level. corpus luteum of pregnancy remains until after birth. also plays a role in development of male fetuses. timing of hCG production also coincides w timing and duration of morning sickness associated w early pregnancy. used as marker for pregnancy tests.
96
role of estrogen w the placenta
- placenta itself does not contain enzymes necessary to convert cholesterol into estrogen
- fetal adrenal cortex produces and secretes dehydroepiandrosterone (DHEA) and converts it into estrogen, which it then secretes into maternal blood. main estrogen it produces is estriol. the corpus luteum of preg is the primary source of estrogen for the 1st trimester
- role of estrogen during preg is primarily to increase the size of the myometrium as the uterus expands and to make sure enough muscle mass for childbirth
- estradiol also promotes the development of the ducts within the mammary glands
97
what does progesterone do in the placenta
- takes about 10 weeks for the placenta to produce enough to support the endometrium and replace the role of the corpus luteum
- placenta continues to grow thru pregnancy, maternal circulating levels of progesterone also increase throughout pregnancy
- maintains cervical mucus plug, stim milk gland development, and suppresses uterine contractions
98
what is parturition and describe it and estrogens roles
aka childbirth
- requires dilation of cervical canal
- during early preg estrogen levels are low, and slowly increase
- end of normal preg period there is an increase in estrogen production that prepares both cervix and uterus for delivery
- late surge in estrogen cause myometrium smooth muscles not connected by gap junctions, to synthesize contractions and to form gap junctions so that the myometrium can contract synchronously
- rise in estrogen increases synthesis of oxytocin receptors in the myometrium
99
describe the 2 effects the pressure of contractions has
1. helps to force open the cervix
2. a neuroendocrine reflex causes the release of oxytocin. this release of oxytocin strengthens the uterine contractions, which puts even more pressure on the cervix so even more oxytocin is released. this cycle continues until birth occurs and cervical pressure is removed, returning oxytocin levels to normal.
100
why are +'ve feedback loops necessary in parturition
they increase the release of oxytocin, which strengthens uterine contractions. these contractions make the birth canal. without the increasing level of oxytocin, there would not be enough cervical pressure, and birth would not occur.
101
describe lactation
the mammary glands or breasts are prepared for milk production. a breast prepared for lactation has a network or ducts that branch out from the nipple and get progressively smaller until they terminate to lobules. these lobules are epithelial-lined milk producing glands called alveoli. milk is synthesized in the epithelial cells and secreted into alveoli, where it can flow thru milk collecting duct to the nipple.
102
how is the preparation for lactation controlled (which 4 hormones)
estrogen (promotes development of milk collecting ducts), progesterone (stim formation of alveoli), prolactin and hCG (stim synthesis of enzymes necessary for milk production)
103
oxytocins job in lactation
from the posterior pituitary is responsible for milk ejection
103
what 2 hormones control lactation
1. prolactin
2. oxytocin
these are released by a neuroendocrine reflex triggered by suckling
