Module 14 Flashcards
List the overall functions of both reproductive systems
Pass on genes of the individuals
Maintain the species
Describe the fetal development of the reproductive system before differentiation
First 6 weeks, common/indifferent gonads
Two sets of primitive reproductive tracts: Wolffian duct (mesonephric) and Mullerian duct (paramesonephric)
At 6-7 weeks, presence of Y chromosome causes gonads to develop into testes
At 9 weeks, XX chromosomes are activated and ovaries develop
Describe male fetus development
7 weeks: testicular cells begin to produce MIH, causing Mullerian duct to regress
9 weeks: testicular cells begin producing testosterone, stimulating Wolffian duct to develop into epididymis, vas deferens, seminal vesicles, and urethra, then external genitalia
Describe female fetus development
Development of the reproductive tract and external genitalia requires no hormonal control
Since no MIH, Mullerian duct develops into fallopian tubes, uterus, cervix, and part of vagina
Since no testosterone, Wolffian duct regresses and female external genitalia develop
List the functions of the male reproductive system
Produce testosterone
Produce sperm (spermatogenesis)
Deliver sperm to the female vagina
List the functions of the female reproductive system
Producing estrogen and progesterone
Produce eggs
Receive sperm
Provide the optimal conditions for the development of the fetus
List the parts of the male reproductive system
External genitalia: penis and scrotum
Penis: urethra, glans penis, corpus spongiosum and cavernosum
Scrotum: testes and epididymis
Ductus/vas deferens, seminal vesicles, prostate, bulbourethral gland
Testes: seminiferous tubules, Sertoli cells, Leydig cells
Describe the function of the seminiferous tubules
Site of spermatogenesis
Describe the function of Sertoli cells
Regulate spermatogenesis, maintain developing sperm cells, produce inhibin, secrete fluid that pushes immature sperm into epididymis, form the BTB
BTB isolates developing sperm cells from blood so immune system won’t attack and destroy them
Describe the function of Leydig cells
Produce testosterone
Located in the interstitial space between seminiferous tubules
Describe the function of the epididymis
Final maturation area for sperm
Storage site for sperm
Describe the function of the vas deferens
Carries sperm from the epididymis to the ejaculatory duct, which drains into the urethra
Describe the function of the seminal vesicles
Contribute fluid to semen during ejaculation
The fluid is rich in fructose and enzymes and helps maintain and nourish sperm
Describe the function of the prostate gland
Secretes enzymes and fluid that help neutralize the acid environment of the urethra and vagina
Describe the function of the bulbourethral gland
Secretes fluid that helps neutralize the pH and lubricate the urethra and vagina to create an optimal environment for the sperm
Describe the function of the urethra (in males)
Transports sperm during ejaculation and drains the bladder during urination
Describe spermatogenesis
At beginning of puberty, sperm production begins
Germ cells contain 46 chromosomes, located at outer edge of seminiferous tubules, divide by mitosis into spermatogonia and primary spermatocyte
Primary spermatocyte undergoes meiosis into secondary spermatocytes then spermatids (23 chromosomes)
Dividing cells are surrounded by Sertoli cells, make their way into center of tubule
Spermatids develop into sperm cells, released by Sertoli cells into lumen of seminiferous tubules
Takes 64 days
Complete maturation takes 12 more days as sperm moves to epididymis by fluid secreted by Sertoli cells
Describe the structure of sperm cells
Head with an acrosome and nucleus
Midpiece with mitochondria
Long tail or flagellum to propel itself once mature
Describe the control of testicular function
Functions of testes controlled by FSH and LH
FSH acts on Sertoli cells to promote spermatogenesis while producing inhibin (feeds back to AP to decrease release of LH and FSH)
LH stimulates Leydig cells to produce testosterone (feeds back to both H and AP to decrease LH and FSH)
List the functions of testosterone
Development of male reproductive tract and external genitalia in embryo
Growth and development of all male reproductive organs at puberty
Development of male secondary sex characteristics at puberty
Sex drive at puberty
Spermatogenesis
Bone and skeletal muscle growth
Increased aggression
Define testosterone (in males)
A steroid hormone produced by Leydig cells in the testes
Describe the production of testosterone
A series of complex reactions, begins with cholesterol, forms several intermediates, ends with testosterone
Cholesterol and testosterone are very structurally similar
Progesterone is one of the intermediates
Describe testosterone levels in relation to age
Rise during fetal development, and brief rise after birth
Remain low until puberty
Between 9-14, GnRH begins to increase, leads to increase in LH and FSH, causing increase in T
16-18 sexual maturity and peak T levels
Beginning at 40, slow decrease in T levels
At 50, sperm production decreases
Define andropause
Period of decreased testosterone production after 40, may occur because Leydig cells no longer fully respond to LH
Accompanied by decreased sexual desire and erectile ability, fatigue and depression, decreased lean body mass, increased obesity, decreased bone density
List the parts of the female reproductive system
External genitalia: vulva
Vulva: clitoris, labia majora, labia minora, vaginal orifice
Internally: vagina, cervix, uterus, fallopian tubes, fimbria, ovaries
Describe the function of the vagina
Receives the penis and sperm during copulation, allows for discharge of fluid during menstruation, and the birth of the baby
Describe the function of the cervix
Secretes mucus that varies during the menstrual cycle - from thin to facilitate sperm entry to thick to prevent sperm entry
Describe the function of the uterus
The site of implantation of the fertilized egg, and where the developing embryo is nourished and maintained
During menstruation, the uterine lining undergoes several phases under hormonal control
Describe the function of the fallopian tubes
The site of fertilization of the egg, contain cilia that pass the egg from the fimbria to the uterus
Describe the function of the fimbria
Capture the egg after it is expelled from the ovaries and funnel it into the infundibulum
Describe the function of the ovaries
Produce eggs (oogenesis), and produce estrogen and progesterone
Define oogenesis
The production of one viable oocyte
Describe oogenesis
During development, egg contained in a follicle
First stage: begins with production of several million oogonia in embryo
Develop into primary follicles, consist of outer granulosa cells and contain the primary oocyte
Granulosa cells secrete fluid into interior follicle, forms antrum
Primary oocyte and follicle remain this way until puberty
At puberty, ovaries activated by GnRH (only several hundred thousand primary oocytes and follicles survived, and menstruation begins)
After puberty, primary follicle develops theca cells outside granulosa cells
Primary follicle enlarges and develops into mature follicle
Oocyte separates from granulosa cells, floats into antrum
Describe ovulation
Follicle grows, production of estrogen from ovaries increases dramatically, causes granulosa cells to grow and produce more estrogen
Instead of decreasing LH and FSH, increases both
LH surge causes granulosa cells to secrete large amounts of fluid into antrum, causing swell, rupture, and expelling egg
Egg gathered by fimbria into fallopian tube
Mature follicle degenerates into corpus luteum
Corpus luteum degenerates into corpus albicans if no fertilization
Define estrogen
A group of hormones, including 17B-estradiol, estrone, and estriol
Principal estrogen secretes by ovaries in humans is estradiol, which is more potent than estrone or estriol
Describe the production of estrogen
Similar to testosterone, continuation of same series of reactions
Requires uptake of cholesterol by the ovaries
LH stimulates theca cells to convert cholesterol into androstenedione
Small amount of androstenedione converted to estradiol by theca cells and released into circulation
Majority of astrostenedione secreted into granulosa cells to convert into estradiol due to FSH
Describe the production of progesterone
Produced in small quantities by both granulosa cells and theca cells before ovulation
LH stimulates both cells to produce progesterone
After ovulation of the oocyte, mature follicle degenerates into corpus luteum, which secretes E and large amounts of P to prepare lining of uterus for implantation
If no implantation, corpus luteum becomes scar tissue
P levels vary during menstrual cycle
Describe estrogen levels in relation to age
Low levels of E during childhood until puberty
Between 8-13, dramatic rise in E, caused by increased secretion of GnRH from H, increases LH and FSH
Pulsate nature of E levels due to very high levels causing positive feedback at AP, producing LH surge to cause ovulation
E levels reach peak then begin to decline in adulthood
Between 40-50, menstrual cycle becomes irregular, ovulation may not occur during some cycles
Cycles stop around 50
Define and describe menopause
Period of decreased E production and cessation of menstrual cycles
Seems to be caused by decrease in number of primary follicles in the ovaries
With fewer follicles, less E produced, little negative feedback, rise in LH and FSH, resulting in ovaries less responsive to high levels of LH and FSH, causing drop in E levels
Menopause characterized by hot flashes, irritability and anxiety, fatigue, lack of strength, decreased bone density
List the stages of the menstrual cycle
Proliferative phase, days 7-14
Secretory/luteal phase, days 14-28
Menses, days 0-7
Cycle repeats
Describe the proliferative phase of the menstrual cycle
Days 7-14
Follicle increases production of E, causing LH surge
Follicle ruptures, egg expelled
E and P stimulate growth of uterine lining
Describe the secretory/luteal phase of the menstrual cycle
Day 14-28
Follicle develops into corpus luteum, increases production of P that prepares uterus for implantation
If fertilization and implantation don’t occur, corpus luteum becomes corpus albicans and P levels drop
Describe menses of the menstrual cycle
Days 0-7
Levels of LH, FSH, E and P are low
Lining of uterus cannot be maintained, uterine lining lost
Describe the birth control pill
Most widely used contraception in NA, two principal hormones, synthetic E and/or P in different combinations and strengths
Contraceptive effects occur by several mechanisms, including decreasing GnRH, LH and FSH levels by introducing E and P that act like natural hormones
Synthetic P produces thick cervical mucus to inhibit sperm entering the uterus, and decreases motility of uterus and fallopian tubes
