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Reproductive and Development (Fetal Development (weeks 21-38 (body gains…
Reproductive and Development
Hormones
Male
testosterone
produced by interstitial cells in the testis
high levels of testosterone facilitate spermatogenesis
hypothalamus secretes FSH and LH
androgens
testosterone
spermatogenesis
Female
FSH and LH
stimulates the follicles in ovaries to mature
a surge in LH levels induces follicle ovulation
estrogen
low levels inhibit secretion of GnRH, FSH, LH
assist with maturation of follicle
human chorionic gonadotropin
signals corpus luteum when implantation and fertilization have occurred
corpus luteum persists for another 3 months
producing large amounts of progesterone and estrogen
progesterone
Progesterone, hormone secreted by the female reproductive system that functions mainly to regulate the condition of the inner lining (endometrium) of the uterus
Embryonic development
week 3
primitive streak appears
gastrulation occurs
week 4
basic human plan is established
derivatives of the three germ layers begin to form
limb buds appear
weeks 5-8
head enlargest
eyes, ears, and nose appear
major organs are formed
Meiosis
Spermatogenesis
occurs in the seminiferous tubules of testis
spermatogonia
diploid cells
divide by
mitosis
first
spermatogonium
germ cell arising from spermatogonia
ensures that the numbers of spermatogonia are never depleted
primary spermatocyte
other cell arising from spermatogonia division
diploid cells that undergo meiosis
secondary spermatocyte
two haploid cells
results from primary spermatocytes meiosis I
spermatids
four spermatids result from secondary spermatocytes undergoing meiosis II
spermatogenesis
the newly formed spermatids differentiate into mature spermatozoa
Oogenesis
ovulated oocyte
breaks away from mature follicle
if oocyte is fertilized, it completes meiosis II
mature follicle turns into corpus luteum
mature follicle
contains secondary oocyte
secondary oocyte has completed meiosis I
secondary follicle
forms from a primary follicle after meiosis I, houses primary oocyte
primary follicle
secrete estrogen as it matures, houses primary oocyte
primordial follicles
consist of a primary oocyte
Reproductive Structures
Male
Seminiferous tubules: spermatogenesis
Sustentacular cells
provide a protective environment for the developing sperm
Interstitial cells
secrete androgens. Mostly, testosterone
Epididymis
stores sperm until maturation and motile
Vas deferens
propels sperm from epididymis to prostate gland
Accessory organs that contribute to semen
Seminal vessicle
alkaline fluid containing fructose to nourish sperm
bulbourethral glands
mucus that lubricates urethra for passage of sperm
Prostate gland
citric acid and PSA
Penile urthra
corpus cavernosum
engorged with blood during an erection
corpus spongiosum
engorged with blood during an erection
Female
Ovaries
houses primordial follicles
fallopian tube
where fertilization occurs
fimbriae
guides ovum to fallopian tube
uterus
where zygote burrows and implants in endometrium
expands as fetus grows, protects baby
cervix
allow flow of menstrual blood from uterus into vagina
direct sperm into the uterus during sexual intercourse
vagina
accept penis during sexual intercourse
birth canal for baby
Fetal Development
weeks 9-12
primary centers appear in most bones
epidermis and dermis of the skin become fully developed
permanent kidneys develop
palate develops
weeks 13-16
body grows rapidly
limbs become more proportional to body
weeks 17-20
muscle movements become stronger and more frequent
lanugo convers skin
vernix caseosa covers skin
weeks 21-38
body gains major amount of weight
subcutaneous fat deposited
eyebrows and eyelashes appears
eyelids open
blood cells form in marrow only
Menstrual Cycle
follicular phase
days 1-13
FSH and LH stimulate up to 20 primordial follicles to mature into primary follilcles
a few of these primary follicles mature and become secondary follicles
late in the follicular phase, typically only one secondary follicle matures into a mature follicle
as the secondary follicle matures, it's primary oocyte finishes meiosis I and two cells form
one of these cells receives a minimal amount of cytoplasm and forms a polar body.
the other cell receives the bulk of the cytoplasm and becomes the secondary oocyte
Ovulation
occurs during day 14
release of the oocyte from a mature follicle
induced only when there's a peak in LH secretion
follicle cells in the mature follicle increase rate of fluid secretion
the follicle eventually ruptures
expelling the secondary oocyte
Luteal phase
occurs during day 15-28
the remaining of the ruptured mature follicle becomes the corpus luteum
corpus luteum secrete progesterone and estrogen
progesterone and estrogen help build uterine lining
also secretes inhibin , inhibits secretion of reproductive hormones from hypothalamus
if oocyte is not fertilized, it regresses and becomes corpus albicans
as corpus luteum refgresses, progesterone and estrogen levels decrease
causing the uterine lining to be shed