Flashcards in Chapter 19 Deck (45)
What do the Reproductive Systems do?
- Produces and unites gametes
- Harbors the fetus and gives birth
- Nourishes the infant
What are Gametes?
Sex cells that meet and combine their genes in a "zygote" (fertilized egg). The gametes require motility to establish a contact, and nutrients for the embryo. Require sperm and Egg
What are Gonads?
Primary sex organs that produce the gametes
Man --> Testes
Woman --> Ovaries
What are the External Genitalia?
- Located in perineum between thighs
- Most externally visible or superficially beneath skin.
What is the Internal Genitalia?
- Located mainly in pelvic cavity, except for testes and some scrotal ducts
What does a Surge of pituitary gonadotropins signal?
Onset of Puberty. Begins preparing system for adult reproductive function.
Boys --> 10-12
Girls --> 8-10
What is Puberty?
- first few years of adolescence
- until first menstrual period in girls
- first ejaculation of viable sperm in boys
- around age 12 in girls; 13 in boys in U.S.
What is Adolescence?
- from puberty onset to attainment of adult height. ends late teens to early twenties
What is Gonadotropin-releasing hormone (GnRH)?
- Secreted by hypothalamus as brain matures
- Stimulates anterior pituitary gland to secrete FSH and LH
What are the Effects of Testosterone?
- Growth of sex organs and sperm production (Testes and scrotum; later the penis and internal ducts and glands)
- Burst of body growth (elongation of limb bones, increasing muscle mass, enlargement of larynx and deepening of voice, elevated metabolic rate and appetite)
- Hair and sweat glands
- Awakening of libido (sex drive)
- sustains male reproductive tract, sperm production, and libido
Testosterone peaks at what age?
After age 50, declining levels of testosterone is accompanied by what?
rising levels of FSH and LH which produces andropause
How long to men normally produce sperm?
To the end of life although in reduced numbers.
Female puberty begins at what age?
age 9 or 10
Elevations is FSH and LH in the female do what?
- stimulate development of ovarian follicles
- secrete estrogens, progesterone, inhibin, and a small amount of androgen
What are Estrogens?
Feminizing hormones with wide-spread effects on the body
The earliest noticeable sign of puberty in girls is _________?
Breast development. Complete by around age 20
What is Menarche?
- first menstrual period
- around age 12 in U.S.
- regular ovulation about a year later
What is Menopause?
- Cessation of menstruation. no menstruation for a year or more.
- Accompanies climacteric
- Hot flashes --> spreading sense of heat. from constriction and dilation of vessels from hormones
How many pairs of Chromosomes are there?
- one chromosome from mother, one from father.
- X and Y in male. X and X in female
What are Homologous Chromosomes?
look identical; except X and Y in male
What is a diploid?
any chromosome with 23 chromosome pairs. Symbolized by 2n
What is a Haploid?
23 unpaired chromosomes. Symbolized n. Germ cells
During Meiosis Reduced from _____ to _______
Diploid to Haploid
What is the difference between Mitosis and Meiosis?
Mitosis --> Serves range of functions, Constant number of chromosomes, Chromosomes unchanged genetically, 2 Daughter cells
Meiosis --> Production of gametes, Reduces chromosome number to haploid, Chromosomes exchange portions of DNA, 4 daughter cells (4 sperm, in female, three tiny and one large cell)
- Consists of 2 cell divisions in succession. The 1st division produces 2 haploid daughter cells, and the 2nd division divides each othe these into 2 more, so that the ultimate outcome is 4 haploid cells.
- Meiosis I: 2 Homologous chromoses exchange segments of their own DNA, they migrate to separate daughter cells. The daughter cells thus have only 23 chromosomes but each chromosome retains its double stranded form, composed of 3 chromatids joined at the centromere.
- Meiosis II: Each centromere divides and each daughter cell now receives 23 single stranded chromosomes.
What is Spermatogenesis?
How many sperm is produced
400 Million per day in a young man
What is Spermatogonia?
- stem cells in testes at birth
- reactivated by testosterone during adolescence
What are the stages of Spermatogenesis?
1) Spermatogonia divide by mitosis, thereby keeping up a man's lifetime supply of sperm. One daughter cell from each division remains near the tubule wall as a stem cell, thus maintaining a lifelong population of stem cells.
2) Second cell enlarges and becomes primary spermatocyte. protected from immune system by tight junctions. Spermatocyte moves toward the lumen
3) Meiosis I by primary spermatocyte. divides into two haploid secondary spermatocytes. Considered genetically unique.
4) Meiosis II by secondary spermatocyte. divides into two spermatids -- a total of 4 for each spermatogonium.
5) Transforms into single sperm cell, termed spermatogenesis. sprouts a tail, sheds excess cytoplasm. when formed, washed down seminiferous tubule by fluid
What does the Spermatozoon (sperm cell) contain?
- Head which contains nucleus with haploid chromosomes and lysosome "acrosome" which contains enzymes that a successful sperm later uses to penetrate the egg.
- Long flagellum, Tail containing a midpiece, thickest part with large mitochondria, principal piece, most of tail (axoneme + supportive fibers and provides most propulsion)
- Endpiece which contains only axoneme
What is Semen (Seminal Fluid)?
- Fluid expelled in orgasm
- 10% sperm
- 30% prostatic fluid containing calcium, ions, and clotting enzyme and protein-hydrolyzing enzyme
- 60% seminal vesicle fluid containing fructose and other carbohydrates, prostaglandins, protein, prosemenogelin
What are the 2 interrelated monthly cycles controlled by shifting patterns of hormone secretion in women?
- Ovarian Cycle --> production of eggs, "oogenesis"." and parallel developments in follicles, "folliculogenesis"
- Menstrual Cycle --> parallel changes in uterus which results in monthly menstrual flow.
What is Oogenesis?
- Produces haploid gamete by meiosis
- Produces one mature egg/month
- Resumes in adolescence
- About two dozen complete meiosis I monthly --> stimulated by FSH, divide into two haploid cells of unequal size, large daughter cell, secondary oocyte and smaller one, first polar body, disintegrates
- Secondary oocyte --> proceeds as far as metaphase II, arrests until after ovulation, if not fertilized, dies, if fertilized completes meiosis II, casts off second polar body, and chromosomes of remaining egg uniting with sperm
What are Oogonia?
- Stem cells multiplying by mitosis in ovaries of female fetus.
- transform into primary oocytes by 6 months
- proceed to early meiosis I
- arrest until puberty
What are the Stages of folliculogenesis?
1) Primordial follicles
2) Primary folliclcles
3) Secondary follicles
4) Tertiary follicles
5) Mature follicles
How long does the Ovarian cycle last?
Averages 28 days
What are the stages of the Ovarian Cycle?
1) Follicular phase --> growth of cohort of follicles, secrete estrogen, Stimulated by FSH, dominant follicle selected to ovulate, grows, considered mature follicle, degeneration of other follicles.
2) Ovulation --> rupture of mature follicle and release of its egg, sharp spike in LH proceeds, induces completion of meiosis I, oocyte swept into uterine tube, may be felt as slight abdominal pain, ovaries alternating month to month
3) Luteal Phase --> phase after ovulation to onset of menstruation, ruptured follicle into corpus luteum stimulated by LH, progesterone and estrogen secreted by luteum (which suppress pituitary output of FSH and LH
and progesterone preparing uterus for pregnancy), shrinks in absence of pregnancy, corpus albicans
(pituitary no longer inhibited, starts ripening new follicles)
What are the stages of the Menstrual Cycle?
1) Proliferative phase --> at beginning, only basal layer present, uterus rebuilding tissue lost in menstruation, estrogen stimulating basal mitosis, blood vessel regrowth, stimulates growth of progesterone receptors, and from end of menstruation (day 5) to about day 14.
2) Secretory phase --> endometrium thickening more from secretions and fluids, from about day 15 to 26 of cycle, progesterone stimulating endometrial cells (secretes glycogen), by end of phase, nutritious bed for embryo development
3) Premenstrual phase --> last two days of cycle, dying corpus luteum secreting less progesterone, triggers contractions of spiral arteries of endometrium, brings tissue necrosis and menstrual cramps, menstrual fluid from dying endometrium, blood and serous fluid
4) Menstrual phase (menses) --> accumulated fluid discharged from vagina, first day = day 1 of menstrual cycle, lasts about 5 days
What happens during Sexual arousal?
- Genitals swollen with blood
- Increased muscle tension throughout body
- Increased heart rate, BP, and respiratory rate
- Secretion of fluids --> from bulbourethral glands in male, greater vestibular glands in female, provide lubrication for intercourse
What happens during an Erection?
- From rapid blood flow through dilated deep arteries
- Lacunae near deep arteries filling with blood --> compress lacunae closer to periphery and compression blocking outflow of blood
- Each corpus cavernosum in tight fibrous tunic which contributes to tension and length increase
- Clitoris also engorged and erect (withdraws beneath the prepuce)
What is an orgasm?
- Short but intense reaction
- Occurs with discharge of semen in males. Ejaculation into the vagina
- Vaginal and uterine contraction in females
What are the stages of Ejaculation?
1) Emission --> sperm propelled from epididymis to prostatic urethra, prostate gland expels fluid into urethra, followed by seminal vesicles, induced by sympathetic nervous system
2) Expulsion --> triggered by semen in urethra, triggers somatic and sympathetic reflexes, causes expulsion of more fluid into urethra, constriction of internal urethral sphincter, bulbospongiosus muscle ensheathing penis root (trigger to compress urethra and expel semen, and most sperm in first milliliter of semen)
What happens Following Orgasm?
- Blood flow reduced to penis and clitoris
- Contraction of trabecular muscles (squeezes blood from lacunae and penis flaccid)