Review Sheet B Test #1 Biology 2213 Dr. James Adams
Reproductive System and Development
THE REPRODUCTIVE SYSTEM -- Chapter 27
This system is NOT part of the homeostatic mechanisms of the body, but instead is about
bringing gametes from two different individuals together to make a new human
Two Major Functions of the primary sex organs -- the gonads (testes/ovaries):
1. Production of gametes -- sperm and eggs (ova)
2. Secretion of hormones -- testosterone (and others); estrogen/progesterone
Control of secretion:
1. GnRH stimulates release of the gonadotropins FSH and LH from anterior pituitary
2. FSH and LH named for affects on female, but important in both sexes
3. FSH estrogen release, LH stimulates testosterone release (see below) which act on
a variety of targets, including negative feedback on the hypothalamus/pituitary
4. Inhibin, released from gonads in both sexes, also inhibits FSH release.
Activation of the HPG axis at puberty -- Hypothalamus/pituitary
exquisitely sensitve to
negative feedback prior to puberty, keeping gonadal production of sex hormones very
low; sensitivity becomes much less at puberty, allowing for progression of puberty
Meiosis -- reduces the chromosome number from diploid (2N=46) to haploid
and is really two divisions, with the first division being the reduction division. You will
need to know stages and names of intermediate cells in both sexes (see below).
Reproductive System Anatomy -- primary and accessory reproductive
organs; refer to
your lab practical "Structures to Know" sheet; you are responsible for knowing the epithelial
linings/muscle in the walls of the various organs
MALE -- Know the following structures and their general functions:
Gonads and coverings
1. Scrotum, with dartos muscle (part of external genitalia)
2. Testes (testicles) -- tunica vaginalis/albuginea, lobules with seminiferous tubules/interstitial
cells, rete testis (see below* for more details on the seminiferous tubules)
1. Epididymis -- storage/maturation of sperm; can be stored for several months
2. Spermatic Cord -- vas deferens, testicular arteries/veins (pampiniform plexus), cremaster
muscle; passes through inguinal canal into abdominal cavity
3. Ductus (Vas) deferens joins ejaculatory ducts (from Seminal vesicles, see below)
4. Urethra -- prostatic, membranous, penile
Penis (part of external genitalia) with prepuce (foreskin)
1. Erectile tissue -- corpora cavernosa (two) with crura; corpus spongiosum (one, around
urethra) with bulb (root)/glans
2. Bulbospongiosus muscles
1. Seminal vesicles -- produce 60-70% of semen volume; alkaline secretions include fructose/
citric acid (for energy), substances that increase sperm motility and fertilizing ability, and
prostaglandins (stimulates reverse peristalsis in female tract; decreases mucus viscosity)
2. Prostate Gland -- produces about 30% of semen volume; secretions include PSA and sperm-
3. Bulbourethral (or Cowper=s) Glands -- secretions are pre-climactic; cleanse the urethra
Semen is a combination of testicular fluid (produced by sustentacular cells), sperm and secretions
of the accessory glands, and includes some antibiotic chemicals as well. One ejaculatory event
releases about 2 - 5 ml of semen, containing between 40 and 750 million sperm.
Male Sexual Response -- Two events:
1. Erection -- a parasympathetic event. Stimulation (various) causes release of NO which
dilates penile arteries, in turn delivering blood to erectile tissues; compresses penile veins.
Parasympathetic stimulation also causes release of fluids from bulbourethral glands.
2. Ejaculation (orgasm/climax) -- a powerful sympathetic event, with effects reaching well
beyond the reproductive tract. Involves peristaltic waves along the duct system, expulsion of
materials from accessory glands, constriction of internal urethral sphincter, and contraction of
the penile bulbospongiosus muscles. Followed by variable in length latent period.
Spermatogenesis -- Meiosis in males; as cells divide, move toward lumen of seminiferous tubules
*Takes place In Seminiferous Tubules: Spermatogonia º Primary spermatocytes (2N) º
Secondary spermatocytes (1N) º spermatids º sperm(-atozoa) -- four functional (but
immature) sperm released in lumen; takes around 70 days. Sperm structure -- head (with
acrosome/nucleus), midpiece (with mitochondria), and tail.
Sustentocytes: several roles
1. Produce testicular fluid
2. Absorbs sloughed off materials from spermatids
3. Forms blood-testis barrier; tight junctions keep genetically unique sperm isolated from the
4. Release ABP (Androgen-binding Protein) in response to FSH
5. Also release inhibin
1. FSH targets Sustentocytes to release ABP; LH (also called ICSH -- interstitial cell
stimulating hormone) targets interstitial cells to release testosterone
2. ABP picked up by spermatogonia; the ABP allows the spermatogonia to respond to
testosterone by initiating meiosis
3. Testosterone (and inhibin) balances its own release (and sperm production) through
negative feedback to hypothalamus (GnRH) and the anterior pituitary (FSH and LH)
Development of Sexual Characteristics: Primary (enlargement/maturation of sex organs) and
secondary (muscle/bone mass, hair growth, voice, etc.). Puberty represents a decrease in
sensitivity of the hypothalamus to testosterone; actual mechanism not clear.
FEMALE -- Know the following structures and their general functions:
Gonads and attachments/coverings:
1. Ovaries with tunica albuginea
2. Ovarian/suspensory ligaments
3. Mesovarium (Mesentery of the ovary; part of the broad ligament**)
1. Fallopian (Uterine) Tubes (or oviducts), with fimbriae, isthmus, mesosalpinx**.
1. Main parts: body, fundus, isthmus, cervix
2. **Broad/round ligaments.
3. Layers of wall:
a. Perimetrium (peritoneal lining around uterus)
b. Myometrium (thick [smooth] muscle in wall)
c. Endometrium with stratum basalis/functionalis and spiral arteries.
Vagina -- adventitia, muscularis, strat. squam. mucosa. With fornices around cervix; hymen
External genitalia (vulvae, pudendum):
1. Clitoris, with erectile tissue (two corpora cavernosa)
2. Labia minora/majora with clitoral hood (prepuce)
3. Vestibular glands
4. Mons pubis
Mammary glands -- READ, and know general information about breast cancer; not actually
part of reproductive system, but won't be in use unless reproductive system has been active!
Oogenesis - Meiosis in females; process partially completed within follicles in ovaries, completed
Oogonia º Primary oocytes (2N; at birth) º Secondary oocytes (1N; at ovulation) º
Ovum (only after fertilization). By puberty only some 400,000 of the original primary
oocytes remains, still well more than she will ever need.
Only one functional ovum produced, due to unequal cytokinesis during meiosis; three polar
bodies also produced.
The Ovarian/Uterine Cycles and Hormonal Regulation of the Cycles:
The hypothalamus (GnRH)/anterior pituitary (FSH/LH) control the ovarian cycle, which in turn
controls the uterine cycle with the ovarian hormones (estrogen/progesterone).
Ovarian Cycle -- Follicular/luteal phases: Rising FSH initiates development of primordial through
primary and secondary follicle to vesicular (antral) follicle (surrounded by theca folliculi);
during this, the primary oocyte develops into a secondary oocyte (which is ovulated). Several
(approx. 20) follicles are recruited to develop, but one usually becomes the dominant follicle
for that cycle. The remainder become atretic (suffer atresia). In the dominant one, follicle cells
become granular, releasing estrogen which initially inhibits FSH and therefore more follicle
development, but estrogen levels reach a critical level and initiate a positive feedback loop with
LH release from Ant. Pit. The peak of LH causes ovulation, and also conversion of remaining
granulosal cells into corpus luteum, which in turn starts releasing progesterone. Assuming no
fertilization, progesterone shuts off LH production which in turn cause atrophy of the corpus
luteum (into corpus albicans [scar]). In a lifetime, a female will ovulate fewer than 500 times.
Uterine (Menstrual) Cycle: Estrogen release from developing follicle stimulates proliferative phase
of endometrium (growth/maturation of stratum functionalis); after ovulation, progesterone ("for
gestation" --the hormone of pregnancy) stimulates the secretory phase of the endometrium
(ready for implantation); with degeneration of the corpus luteum, the spiral arteries spasm and
Please look at the excellent summary diagram, Fig. 27.23, pg. 1072, and hormonal control,
Fig. 27.25, pg. 1077.
Development of Primary/Secondary Sexual Characteristics: As with male, hypothalamus decreases
in sensitivity to female hormones at puberty. Estrogen has strongest effects on primary/secondary
structures, with maturation of sex organs, deposition of fat/development of breasts, wider/lighter
hips, etc. Puberty involves the first menstruation (menarche) and establishment of the cycle.
Female Sexual response: as with male, involves excitation by various stimuli (a parasympathetic
event with increased blood flow to clitoris, walls of vagina, and breasts, and increased secretions
from cervical/vestibular glands for lubrication), followed by climax or orgasm (a sympathetic
event with muscular contractions [reverse peristalsis] of reproductive tract, and muscular
contractions in other parts of the body and pleasurable sensations). Typically, no latent period
necessary, and female can enter directly into new excitement phase. Hormone of sex drive in
females is apparently both estrogen and DHEA, secreted from the adrenal cortex.
Menopause -- Events of (reasons for masculinization; loss of bone mass); DHEA secretion continues,
however, so there is not a loss of sex drive.
Sexually Transmitted Diseases -- read and know general characteristics of each, including most
commonly transmitted bacterial/viral (chlamydia/herpes)
Development of Male vs. Female Structures (ovary = testis; erectile
tissues in clitoris & penis; underside
of penis = labia minora; scrotum = labia majora); see pages 1082 and 1083.
DEVELOPMENT -- Chapter 28
Fertilization to Birth; conceptus passes from zygote through embryonic stage through fetal stage.
I. Embryonic stage: from fertilization
through organogensis (first eight weeks)
Fertilization -- involves sperm capacitation (degradation of acrosomal membrane)
Several hundred sperm necessary to digest path through layers of cells and zona pellucida
Involves the acrosomal reaction
Prevention of polyspermy -- one sperm cell reaches and penetrates the secondary oocyte
membrane; at this point, two events occur to prevent second penetration:
1. The oocyte membrane block -- when sperm binds to sperm-receptor in oocyte
membrane, the oocyte sheds the remaining receptors on vesicles budding off the main
membrane;this may "draw" other sperm away from oocyte by acting as "decoys"
2. The cortical reaction, where calcium channels open, calcium enters and cause cortical
granules to release enzymes that destroy the zona pellucida sperm binding receptors, as
well as releasing materials to form the fertilization membrane.
2° oocyte completes second meiotic division, forming ovum briefly before nuclei fuse.
Cleavage divisions: zygote º morula º blastocyst (w/ trophoblast, inner cell mass, fluid cavity)
Trophoblast -- contribution to placenta; forms chorion, which releases human chorionic
gonadotropin (hCG),which is identical in function to LH and retains corpus luteum
(progesterone secretion), and therefore placenta, for first trimester (at which point, placenta
produces own estrogen and progesterone). Upon implantation, forms syncytiotrophoblast
which, in turn, develops chorionic villi bathed in by maternal blood (in lacunae) for exchange
of wastes from and nutrients to developing conceptus (this is baby's contribution to the
placenta); cytotrophoblast remains immediately around developing conceptus
Inner Cell Mass (Embryoblast) -- further differentiates to form embryonic disc, with two mem-
branous sacs inside chorion, the amnion (ectodermal side) and yolk sac (endodermal side)
Embryonic disc -- double-layered (ectoderm/endoderm) goes through gastrulation, where
cells of ectoderm divide and migrate in between the two existing layers, forming mesoderm.
Establishment of three primary tissue layers ends gastrulation and begins organogenesis.
Organogenesis (gastrulation through formation of all organ systems; weeks 3-8)
The reason why gastrulation is considered so monumental is that the origin of any tissue/organ can
be traced back to one of the three primary tissue layers. Not long after gastrulation, entire
blastodisc "folds over" on itself, both along sides and end to end, engulfing much of the yolk sac,
forming the initial gut lining and extending the ectoderm (and amnion) around the entire outside.
Early events in organogenesis: formation of notochord (in mesoderm)
Chemicals released from notochord stimulate neurulation in the overlying ectoderm, first
forming the neural plate, then neural folds/groove, and ultimately neural tube
(The rest of organogenesis is another course -- embryology!)
Know what comes from ectoderm, mesoderm, endoderm -- Figure 28.13, page 1106
Additionally, you will need to know more about specializations of the mesoderm:
1. Somites, each with a sclerotome, myotome and dermatome (know what each one does)
2. Intermediate mesoderm (in abdominal region only) -- leads to gonads, kidneys
3. Lateral mesoderm: two sections
a. Somatic (dermis, parietal serosae, connective tissues of limbs)
b. Splanchnic (circulatory system, visceral serosae, smooth muscle/C.T. in walls of tubular
II. Fetal Stage: from completion of organogensis to birth (weeks 9 through term)
One of last events is maturation of the lung=s type II (surfactant-secreting) cells in 7th month
Effects of Pregnancy on Mother
Anatomical Changes: increased vascularization of reprod. organs, including vagina; incredible
enlargement of uterus; loosening/widening of pelvis (relaxin)
Metabolic Changes: Dietary requirements -- balanced nutrition, with around 300 extra calories a day
Know effects of human placental lactogen [hPL] (duh!) and human chorionic thyrotropin [hCT]
(hopefully also a "duh!")
Physiological Changes: to GI, urinary, respiratory, cardiovascular systems
Parturition -- Birth
Labor: placental estrogen production has increased during fetal stage; this stimulates formation of
oxytocin receptors on myometrial cells, and antagonizes progesterone
Fetus begins producing oxytocin causing placenta to release prostaglandins -- both oxytocin and
prostaglandins stimulate myometrial contraction, which in turn stimulates maternal release of
oxytocin from the hypothalamus/post. pit. (a positive feedback loop).
Dilation/Expulsion/Placental Stages -- Apgar score
Adjustments of neonate to extrauterine life -- first breath, closing of circulatory shunts, temp. reg.
Lactation -- prolactin stimulates milk production (but colostrum first); actual nursing stimulates
release of oxytocin, which not only stimulates milk ejection (let-down) but also shrinking of uterus.
Breast milk is nutritive, protective and laxative, important for infant to release meconium.
Continued nursing has a distinctive (though not complete!) inhibition of GnRH release, and so is a
natural birth control to some extent.