Chapter 28 Notes
Chapter 28 Notes 80887 - BIOL 3150 - 001
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This 16 page Class Notes was uploaded by Abigail Towe on Monday November 9, 2015. The Class Notes belongs to 80887 - BIOL 3150 - 001 at Clemson University taught by Tamara L. McNutt-Scott in Fall 2015. Since its upload, it has received 17 views. For similar materials see Functional Human Anatomy in Biological Sciences at Clemson University.
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Date Created: 11/09/15
The Reproductive System ● you as an individual can live without a reproductive system, but as a species we need it to have a continuation of species ● it’s quiescent (quiet/at rest/inactive) until puberty - ○ puberty - time of reproductive maturity - can now successfully reproduce ● comprised of: gonads, ducts, accessory glands, and external genitalia Development of Reproductive System ● aristotle- thought that the heat/passion of sex is what determines maleness (you would get a son) ● how does your body know if you are male or female? ○ know that: you start out sexually indifferent with a bipotential gonad (neither male or female) that are sexually indifferent. these gonads are reproductive tissue. has capacity to become male or female. ■ there are two duct systems in the sexually indifferent system: ● Mesonephric duct (Wolffian duct) ● Paramesonephric duct (Mullerian duct) ○ the activation of SRY gene initiates the sexually indifferent gonad to become a testes (male) if activated ■ it’s a sex-determining region of Y chromosome ○ if SRY is activated, then development of male reproductive system starts: ■ Mullerian duct will break down and be regressed/ not used and be reabsorbed. ■ Wolffian duct- forms duct for epididymal duct ○ if female: in the absence of Y chromosome, there is an activation of this lack of Y chromosome to form an ovary (because if no Y, then an X chromosome comes forth to form XX = female) ■ the mullerian duct forms → oviduct and the uterus and a little part of the vagina ■ since the mesonephric duct (the wolffian duct) doesn’t have any androgens to support it --it regresses because it isn’t needed ○ in humans, you start off sexually indifferent. by week 7 or 8- the SRY gene is activated to form male (using the Wolffian duct (mesonephric duct) used). ○ there is a two week window for this SRY gene to become activated. ○ scenario- if androgen is blocked and you have male chromosomes (XY)- and you have estrogens presence- then you have a genotypic male( XY) but a female phenotype (XX) ■ can occur vice versa ■ jamie lee curtis Male reproductive system: ● anatomically more simplistic (straightforward) ● functions: produce gamete and their functional maturation. & store and move gametes from testes ● it’s a continuous system - WHY? ○ deals with anatomical construction ○ it’s because if you look at sperms journey: ■ start in testes move to epididymis to ductus deferens then to ampulla to ejaculatory duct and then it joins the urinary system and use the urethra ○ anatomically speaking there is no breaks, it goes from one anatomical region to another ● testicular development: ○ develop close to where the kidneys are (inside the body cavity) ○ has structure called gubernaculum ■ this is a bundle of CT fibers that extend from testis to floor of scrotal swelt (scrotum) ■ as this structure grows, it does not actually change length, it only chances position. ■ there is rapid growth in first 7 months of life ■ at 7th month, the growth is rapid and hormones stimulate contraction of gubernaculum ■ so around 7 to 8 months, the gubernaculum contracts to pull testis through inguinal canal to form scrotum ■ if we look at what happens during this process and how things finish up after child birth, the testes comes down but also part of the parietal peritoneum is pulled down. ● when part of the parietal peritoneum is pulled down, it forms the tunica vaginalis- is formed as the testis is pulled into scrotum. It’s a serous membrane that allows testicular movement within the scrotum sac. It’s derived from parietal peritoneum. ● forms structure called spermatic cord = made of ductus deferens, testicular blood vessels, nerves and lymphatic vessels ○ testes: ■ has parietal and visceral layer = serous membranes to allow movement ■ wrapped in tunica albuginea - this CT invaginates into vastus proper to form septa, which then finds globulus to form seminiferous tubulus ■ in seminiferous tubules, spermatogenesis occurs ( sperm cells becoming a structurally mature sperm cells) ● know it occurs in the lumen ■ there’s a place called mediastinum testis ● forms the network called rete testis ● site of entry into testes proper for vasculature ■ everything is present in spermatic cord has nerve, vasculature--- only thing not present is lymphatics Quiz 10: male reproductive system: seminiferous tubule has sertoli cells (sustentacular cells) ● have two compartments in adluminal and basal that form tight junctions to seal the tubule off into the two compartments. ○ basal compartment - close to the basal lamina ■ spermatogonia is found in basal ○ adluminal compartment - toward the lumen ■ adluminal compartment needs to be separated from immune system to form blood-testis barrier. ● blood-testis barrier- formed by these two compartments because they do not allow large molecules pass through. ○ it’s important to keep spermatogonia, spermatocytes, spermatids, and mature spermatozoa from blood so that the immune system does not become introduced and try to kill the sperm bodies. This is what causes many men to become infertile. ● relationship of testis to scrotum and spermatic cord: ○ testis are found outside of the body ■ exception: elephants have internal testes. ○ cremaster muscle - it’s skeletal muscle that is derived from internal oblique muscle ■ covers the spermatic cord and testis ■ functions to retract testis (brings testes closer to body to keep it warm or relax to allow more circulation testes) ○ dartos muscle: ■ smooth muscle within scrotal wall ■ function: temperature regulation of testis ● does this by causing wrinkling of the scrotum → more SA to retain more heat when it’s cold ● when it relaxes, the surface area decreases so heat radiates ○ these two muscles are important because spermatogenesis depends on temperature ○ raphe ■ the line that results from the union between two contiguous, bilaterally symmetrical structures ■ unique anatomical structure ■ nothing to do with reproduction ○ pampiniform plexus ■ remember: plexus- interweaving network of something ● this specific plexus is a network of vasculature ■ in spermatic pore ■ we don’t want the blood bringing in too much heat because it could shut down spermatogenesis. ■ so there’s a countercurrent mechanism as a heat exchanger ● as warm arterial blood flows into the testes it is wrapped by a section of the testicular vein- where it becomes the pampiniform plexus. ○ so blood is cooled as it enters testis, but warmed as it leaves the testis ● this mechanism is a way to make sure the testis remains correct temperature ■ structure within spermatic cord Spermatogenesis ● occurs continuously from time of puberty ○ puberty = age 14 but prob more around age 12 or 13 in more modernized countries ● takes about 64-72 days to mature sperm ● produces about 140 x 10^6 sperm per day ● sensitive to temperature ● starts as: spermatogonia -- goes through meiosis and ends up forming a structurally mature sperm cell ● we have a blood-testis barrier because: ○ represented by tight junctions between sertoli cells ○ puberty occurs around 14 years old ○ T cells are set before puberty ○ blood testis barrier serves to immunologically isolate developing sperm cells. we need this because male reproductive system recognizes spermatogonia but they don’t recognize spermatids or structurally mature sperm. ○ one common element in infertility is due to immune system- where the sperm cells are viewed as non-self and then they are attacked after that. ● spermatogenesis cell is seen as self- but anything after that is seen as non-self ● spermatogenesis- start with spermatogonia and ends with sperm ● spermiogenesis is a part of spermatogenesis ○ reconstruction of round spermatocyte to structurally mature sperm ○ note: structurally mature, but not functionally! ○ structure ends up having: ■ acrosome cap = head of sperm ■ nucleus (genetic material) ■ mitochondria that creates energy to move itself = found in midpiece ■ tail = flagellum ● spermiation - another process that sperm undergoes ○ sperm loses attachment to sustentacular cells Epididymis ● “half-moon” shaped organ (or large comma) ● highly coiled ● area that McNutt-Scott spent majority of her research ● 3 regions: 1. caput (head) - where sperm comes in 2. corpus (body) 3. cauda (tail/end) ● function of epididymis: ○ monitors/adjusts fluid composition to support developing cells ○ recycling center for damaged sperm ■ anything “bad” is reabsorbed and taken away ○ stores, protects, and facilitates functional maturation of sperm ○ sperm earns “diploma” saying they have learned how to swim in epididymis and now have capacity to fertilize ● sperm moves: along epididymis occurs via peristaltic contractions of wall smooth muscle. so sperm is constantly move to caput/head, corpus and caudal. stored in tail/cauda region until ejaculation. Ductus Deferences, Ejaculartory Duct, and Urethra ● once we leave the testis and leave the epididymis- the functionally and structurally mature sperm then moves through the ductus deferens and goes back into the body cavity and then into the ampulla (storage cavity) of the ductus deferens ● ductus deferens connects epididymis to urethra ○ the wall of ductus deferens is constructed of thick layer of smooth muscle ○ wall is also lined with pseudostratified ciliated columnar epithelium ● then move from ampulla (store cavity) to ejaculatrory duct, which is a connection tube, to connect to seminal vesicles to urethra (now connected to urinary system) ● urethra is just used for delivering the gametes Sperm’s journey: testes → epididymis (caput to corpus to caudal)→ ductus deferens → ampulla → seminal vesicle → ejaculatory duct → prostatic urethra → urethra Accessory Glands: ● provides fluid medium that is part of the semen that sperm is suspended in ● function: provide nutrients, butter and functional maturation ● in human male, they have: ○ seminal vesicles: ■ tubular gland ■ highly secretory structure ■ makes 60% of the fluid composition of the semen ■ secretions high in fructose - sperm’s favorite energy source ■ has prostate gland’s and fibrinogen ■ slightly alkaline ● female reproductive tract which is slightly acidic so having buffers is important. it helps to keep gametes in the female reproductive tract. causes contraction of vagina muscles to keep sperm in there. the human semen actually gels to help it stay and protect it from environment - helps it into cervix. ○ prostate gland ■ sits at base of bladder ■ round ■ muscular ■ encircles urethra ■ wrapped by smooth muscle ■ produces prostatic fluid ■ slightly acidic ■ contains seminalplasmin (helps get rid of bacteria) ○ bulbourethral gland ■ Cowper’s gland ■ tubuloalveolar mucous gland ■ primarily secretes thick mucus that is alkaline Semen: ● in human it’s milky white, someway sticky (because presence of fructose) ● mixture of sperm and accessory gland secretions ● provides a transport medium, nutrients, chemicals to protect and activate sperm ○ and facilitates their movement 6 ● humans produce about 2-5 ml volume with 5-13 X10 sperm/ml Penis ● tubular organ at distal end of urethra ● two functions: ○ conduct urine to exterior ○ also used to deposit male gamete in female Reproductive tract ● erectile tissue - deep to dermis ○ it’s a dense network of elastic fibers ○ largest erectile tissue in body, not the only location of erectile tissue ○ moving through it is vascular channels ○ it’s a spongy network of connective tissue and smooth muscle riddles with vascular spaces ■ so vascular channels that are separated by networks of connective tissue and smooth muscular fibers ● 3 cylinders/columns of erectile tissue: ○ corpus cavernosum (2) ■ has central artery ○ corpus spongiosum (1) ■ has the spongy urethra ● has deep fascia that allows tissue to become flaccid and erect ○ allows movement of erectile tissue with skin ● why is it better to use this type of erectile tissue? why have cylinders of erectile tissue? why erectile tissue instead of just a hollow tube? ○ it offers structural support! ○ erectile tissue gives better rigidity and more structural strength with this anatomical design ● two blood supplies: ○ one is blood supply that provides regular nutrients ○ one is helicine arteries: ■ these are actually involved with the functionality of the erectile tissue Erection and Ejaculation (two separate processes) ● regulated by autonomic nervous system ○ so the neural input coming in is from the autonomic NS ● erectile tissue muscle = smooth muscle in blood vessels and vascular spaces ○ use Autonomic NS because vascular walls are gonna have smooth muscle (which is regulated by autonomic NS) ● erection occurs because of sensory and mental stimulation ○ vasodilator impulses from parasympathetic NS ■ causes relaxation of penile vessels → allows the blood flow into erectile tissue ■ as the tissue fills with blood, this creates a high pressure system that traps the blood within penis to sustain erection ■ the drainage elements are found more peripherally (on the sides), so as the erectile tissue flows in, it blocks the drainage vessels flow. ■ so by trapping the blood flow, erection is sustained ○ at the same time are are going to suppress sympathetic NS ● Ejaculation: ○ coordinated by sympathetic nervous system ■ contractions of vas deferens and have “sweeping” peristaltic contractions in penile urethra (also in urethra as well) ■ moves sperm through series of ducts ● with psychological relaxation, vasoconstriction of penile arteries occur allowing outflow channels to open and the erectile tissue drains ● PNS and SNS - point and shoot ○ Parasympathetic NS - point (erection) ○ Sympathetic NS - shoot (ejaculation) Hormonal Regulation of Testicular Activity ● hypothalamus produces GnRH ---> stimulates anterior pit to send LH and FSH ● LH stimulates the leydig (interstitial) cells release testosterone ● spermatogenesis requires both FSH and testosterone ● males also make prolactin - ○ this increases sensitivity of interstitial cells to LH ○ prolactin is supportive of LH influencing interstitial cells and making sure they are producing testosterone ● Inhibin serves as a “sperm barometer” ○ when sperm numbers increase, then the testes releases more inhibins ○ inhibin function: shuts down the release of the gonadotropins (shuts down GrnH) ■ helps to regulate the number of sperm being made and keep it within a normal range ○ thus, when sperm numbers decreased, inhibin secretion declines so the release of gonadotropins increases to lead to sperm production. Female Reproductive System ● series of organs and other structures that allow use to produce gametes as well as support steroid production. ● also site of fertilization, embryonic/fetal development, parturition (childbirth) and nutrition of postpartum ● more complex - because females responsible for gastration and postpartum and parturition. the energy demands on female is much greater in majority of species than on the male. energy demands are higher because of all the required processes. ● discontinuous system because: there is a break in the system at the ovaries. ○ the ovaries expel oocytes (side note: this is how you get ectopic pregnancies) ■ the ovaries are where oogenesis occurs and expelled- to be picked up from oviduct - which is picked up by the fimbriae (finger like structures of oviduct) ■ then it goes into the uterus and then goes into the vagina ■ oocytes don’t have to go into the oviduct- they can go away ● same thing for sperm- can go away. doesn’t have to go into oviduct. can be found in fluid surrounding. ● ovaries and uterus anchored by specific cords and sheets of connective tissue ○ the fimbriae/oviduct hangs over uteries (fimbriae holds ovaries) ○ broad ligament- the “cape”, which is peritoneum that folds over the structures of the female reproductive system ○ two ligaments: keep ovaries stationary ■ suspensory ligament- attach ovary to the body wall ● this is where vasculature comes into this suspensory ligament ■ ovarian ligament- posteriorly located, attaches to uterus to ovary to keep ovary in place . important to keep it in reach of fimbriae ○ terms: ■ anteverted- where uterus is inclined forward ● most young women our age should have this ■ retroverted- uterus is turned backwards toward rectum ● as you age it tilts this way The Ovary and Follicle Development ● germinal epithelium has simple cuboidal epithelium on the outside of ovary - scientists first thought these were oocytes. ○ wrong - but the name didn’t change : hemocytes forms the capsule that surrounds ovary ● has two domains: ○ medulla: inner layer ■ vasculature and lymphatics comes in through the suspensory ligament ○ cortex: outer layer ■ action occurs here ■ where follicles develop ● important terms; ○ primordial follicles- these are recruited oocytes during each cycle (usually 10-15). they then flow through grow to be a mature follicle. ○ mature follicle - or vesicular follicle- ■ fluid filled antrum with oocytes with zona pellucida and corona radiata ○ then the follicle is ovulated ○ follicle then converted into corpus luteum Oogenesis- ● look at oogonia (equivalency in males: spermatogonia)- these are diploid cells that divided by mitosis ○ increase oogonia and spermatogonia through mitosis ○ there is a difference between males and females. ○ in adult male, you have presence of spermatogonia. stem cell is retained. ○ in females, right before birth- the oogonium starts in meiosis and becomes arrested. ■ this means that women are born with their full compliment of oogonium. Women are born with all the oocytes they will ever have. ■ This is different from male that continually produce spermatogonia ● radiation is bad for both males and females - ○ males because spermatogonia are ready to divide ○ females because they have their whole set that they are born with. ● female oogonia are inactive until puberty- then the reproductive cycle starts. ○ each month, up to 20 primordial follicles mature into primary follicles. from there, only one of the primordial follicles develop into secondary follicles. the primary follicles that do not mature into secondary follicles undergo atresia. ○ the one primary follicle that matures into secondary follicle completes the first meiotic division. This creates a polar body and a secondary oocyte. This secondary oocyte is a haploid cell (23 chromosomes) and pauses in the second meiotic metaphase. Only if it is fertilizes does this secondary oocyte complete the second meiotic division to become an ovum. if not fertilized, it is degraded. ● once primordial follicles are recruited and undergo development, they undergo mitosis and stop right before meiosis 2. ● menarche- first reproductive cycle ● menopause- one full year without reproductive cycle (and not pregnant) then you are officially in menopause ● spermatogenesis - we end up with 4 structurally mature sperm cells (4 gametes) ○ sperm - genetic material with a tail that tries to get to site of fertilization ● but in female, we end up with 1 ovum. the extra genetic material is released as first and second polar bodies. ● why one ovum and 4 sperm? ○ because the uterus is set up for one, maybe 2 young ○ all the elements are in place for the first cell division. ovum has all the nutrients are there. until the nucleus for the first zygote can take over and use it’s own genetic material -which takes time. ○ so that’s why the ovum is such a large cell - it houses and provides energy for the first division for the zygote. ● female reproductive cycle usually ovulates 1-2 oocytes per cycle Meiosis- diploid cell → haploid cell mitosis = diploid cell to diploid cell Ovarian Cycle: ● length of ovarian cycle is 21-40 days in length ● two phases of ovarian cycle: ○ follicular phase ■ represented by recruiting one of these primordial follicles and progress under series of events to turn into mature (or graafian) follicle which is a cell that’s ready to ovulate. ● during these time,this mature follicle produces estrogen ■ then we have ovulation - ovulation is like an eruption because the walls of follicle thin and the pressure inside builds. so the oocyte “pops out” ■ what causes ovulation? rise in gonadotropins (FSH and LH, LH is larger force). ● important because it’s then going to affects the cells left over in the follicle. this represents luteal phase. these cells go through luteinization. under impression of LH. take the follicle that was making estrogen, now undergo morphological changes to become the corpus luteum and make progesterone. ● this change in hormone product being produced = steroidogenesis to produce progesterone ○ ○ luteal cells produces the progesterone ■ remains active and has a timer: has a signal for pregnancy - to maintain corpus luteum is maintained if pregnant. ■ if the signal is not maintained, the cycle restarts again ○ follicle cells produces estrogen ○ luteal phase ■ remains fairly constant Structures of female reproductive system: ● oviducts (fallopian tube) - hollow muscular tubes. ○ held up by broad ligament ○ open into peritoneal cavity ○ 3 segments: ■ infundibulum - close (but not attached to) ovary - ends have fimbriae ● picks up the egg? ■ ampulla- fertilization occurs here. ■ isthmus- connects to uterus - site where fertilization occurs- serves as “sperm reservoir” . ● as sperm comes into vagina, sperm “takes a break”/comes immobile on isthmus of oviduct so that they reach the infundibulum at different times. decrease risks of missing ovulated egg. egg continually met by sperm. ○ functionality: ■ designed to receive oocyte ■ site of fertilization ■ preimplantation of development (immediately after fertilization occurs in ampulla- then it heads to uterus) ● ectopic pregnancy is when the fertilized egg doesn’t go into the uterus, it goes back toward fallopian tube. ● Uterus ○ once egg ovulated, moves into oviduct, and uterus ○ uterus is also a hollow, muscular organ ○ muscles and ligaments help to limit its movement ○ anatomical subdivisions: ■ fundus- dome shaped superior portion ■ body- corpus ■ certix - bottom basement of uterus- inferior narrow portion opens into vagina ○ in the human female, we have a simplex inverted design (triangular design) so a larger superior portion and then a narrow base. ○ function: ■ serves as a site of implantation and embryonic/fetal development ■ parturition ● Uterine wall ○ 3 layers important for its functionality 1. endometrial- mucosal lining a. made of simple columnar epithelium on top of a thick, robust basal lamina. it’s made up of two elements: stratum functionalis and stratum basalis. i. stratum functionalis- next to lumen. responds to the hormonal environment- so it undergoes the cyclic chances in response to the hormonal changes from estrogen to progesterone. this layer is fed by a spiral artery( coiled arteries). 1. lost during menses.contains most of uterine glands. thickness. ii. stratum basalis- sites next to myometrium.thin layer fed by straight artery. also has uterine glands. 1. foundation for new functional layer after menses. 2. myometrium - no distinct layers. interwoven smooth muscle bounded. 3. perimetrium- serosa layer (visceral peritoneum) Uterine Cycle: ● “menstrual cycle” in humans ● 3 phases of uterine cycle: married to what happens in ovary because it reflects what happens to uterine cycle 1. menses- degeneration of endometrial functional zone. a. breaks down in patches because of the constriction of spiral arteries. b. the entire endometrial functional zone is lost = menstruation a. menses is actually a lack of hormones. 2. proliferative- endometrial basilar zone grows to restores integrity of endometrium by forming the functional layer. growth and vascularization is restored in functional layer. supported by estrogen. a. estrogen builds. progesterone maintains. 3. secretory - enlargement of uterine glands along with increased secretory rate and elongation of coiled arteries. tissues maintained by progestins. ● when hormones releases decline, the spiral arteries respond by constriction - which leads to menses and so the whole uterine cycle begins again. ○ the straight arteries are insensitive to hormone levels. so the stratum basalis is never really affected by hormonal changes because it consists of straight arteries. The vagina and external genitalia ● amenorrhea - loss of reproductive cycle ○ correlation between amount of body fat and reproductive cycle ○ reproductive cycle is very costly- requires a certain amount of body fat ○ so a woman’s overall fat content has to be a certain level to have a cycle. ● dysmenorrhea- painful menstruation Vagina- ● thin-walled elastic fibromuscular tube ● extends from certix → vestibule ● function: ○ serves as birth canal ○ serves as passage for elimination of menstrual fluids ○ a site of semen deposition ○ so basically a conduit or deposition place ● structure: ○ vaginal rugae ■ why fold the inner layer? ● folds are important because this area stretches. ■ the primary tissue type of this mucosal membrane is connective tissue and epithelium. (remember epithelium doesn’t allow stretching. and connective tissue is somewhat stretchy.) ■ so rugae of mucosal folds allows structure to stretch without tearing. Mammary Glands: ● found in both sexes ○ functional in females, but males can have breasts ● functionality seen in females: produce milk (lactation for newborn offspring) ● mammary gland is a specialized organ of integument - modified sweat gland. ● hormones that regulate lactation: prolactin stimulates milk production and oxytocin activates smooth muscles that helps with milk injection/”milk let down”. ○ guys also produce prolactin (supportive of gonadal activity) and oxytocin ■ oxytocin stimulates smooth muscle contraction in male reproductive system ■ oxytocin also referred to as “cuddle” hormone because it does enhance pair bonding and maternal behaviors ● elevated levels of oxytocin found in mated pairs ■ also may be connected to limbic system ■ evidence: when couples cuddle their oxytocin levels rise → brings down cardiac output and heart beat, which brings down blood pressure. makes you more relaxed, lessens stress and anxiety. ● has ductal system and milk producing alveoli. ○ in females,you have both ○ but in males, they tend to only have elevation of ductal system only. ● gynecomastia - “man boobs” ○ excessive development of male mammary glands due to ductal proliferation due to increased estrogen levels ○ seen mostly at time of puberty in males. observed in normal adolescence ■ so not only is their voice changing, they start to develop breasts. but over time the tissue is reabsorbed and the mammary structures will not longer exist. ■ commonly seen at puberty because sex hormones are being produced. ○ males produce estrogen just like they produce testosterone ■ because the zona reticularis produces gonadocorticoids (estrogens and androgens) ● also breast development of females as well during puberty
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