monotremes
animals considered to be a transitional form btwn reptiles n mammals
In these animals, defecation, urination, and oviposition (egg-laying) all occur through common orifice, the cloaca
Ex: platypuses and echidnas
cloaca
the body orifice in monotremes which defecation, urination, and oviposition (egg laying) all take place
Properties of the reproductive system - male and female
Make gametes
Secrete hormones to maintain repro organs as well as other systems
Have ducts for moving gametes around
Have glands for lubrication and gamete support
Have complementary anatomy, so partners are held together briefly as gametes are exchanged
gametes
the haploid cells that when combined, make a unique human being
Define genitals and gonads
The genitals are all the structures of reproduction, both male and female
The gonads: strucutre which produces gamates ~ testes and ovaries
Properties of FEMALE reproductive system that males cannot do
fertilization (union of gametes)
implantation (attachment of embryo to uterus)
parturition (labor and delivery)
urology
the medical specialty that treats disorders and diseases of the male reproductive system
Anatomical features found in male
Testes
Ducts
Accessory sex glands
Urethra (shared btwn repro and urinary system)
Penis (shared btwn repro and urinary systems)
Anatomical features found in female
Ovaries
Uterine (Fallopian) tubes
Uterus
Cervix
Accessory sex glands
Vagina
Explain what they do:
Testes
Ducts
Male accessory sex glands
Testes: produce continuous supply of sperm; also make testosterone & other androgens
Ducts: transport, store, and assist in maturation of sperm
Accessory Sex glands: secrete bulk of seminal fluid
What all does the penis do?
encloses urethra as passageway for excretion of urine
Penis and urethra used to introduce semen into female by coitus and ejaculation
What do the ovaries do
produce oocytes, progesterone, estrogens, inhibin, and relaxin
stores and matures eggs
What does the uterine tubes do
"Fallopian" tubes
transport oocyte to uterus
is site of fertilization
What does the uterus do
site of implantation of fertilized ovum and supports development of fetus
What do the FEMALE accessory sex glands do
secrete fluid during coitus
What all does the vagina and cervix do
Vagina receives penis during coitus
Cervix and vagina are passageways for childbirth
spermatogenesis
the making of sperm
spermatozoa
or simply sperm
the gametes produced by the male
are produced in the hundreds of millions
Made in the testes, mature in the epididymis, then upon demand travel through ducts to be ejaculated
What is one single sperm called
spermatozoon
scrotum
a loose sack of skin loosely attached to the body wall
house the testes
the loose attachment is important as sperm production is highest at a temp about 2-3° lower than body temp
has 2 muscles: dartos & cremaster
spermatic cord
a canal which carrie nerves, blood vessels, and the "vas" from inside the abdomen to the scrotum
ductus deferens
also called the vas deferens
the ducts which carry sperm from seminiferous tubules to prostate
one on each side, lead to midline urethra at prostate gland and end there
dartos
one of two muscles of the scrotum that helps support the testes, spermatic cord and spermatogenesis
surrounds the scrotal sac subcutaneously
In cold conditions, causes the scrotum to become firm, drawing the testes toward body
will cause wrinkles to appear in the sac when the muscle contracts
**Lets dart inside, it's cold
Cremaster
one of two muscles of the scrotum that helps support the testes, spermatic cord and spermatogenesis
surrounds the testical; either draws the testes higher into the scrotal sac to protect them from danger or allows it to hang down
**HAHA, I am your master, you will hang when I say you can hang
Describe the inside of the testes
Each testis is divided into compartments called lobules
Each lobule contains 1 - 3 seminiferous tubules where sperm are produced
tunica albuginea
fibrous septum (collagen) which divides the testes into lobules
What kind of cell actually makes spermatozoa
spermatogenic cells
Sertoli cells
also called sustentacular cells
support the function of spermatogenic cells
basically make nursery environment for baby cells
inside basement membrane
stimulated by FSH from the pituitary
**Sed (Syd) likes making babies in a tent (sustentacular cells). But Sadie said "Fuck Syd to Hell" (FSH hormone)
androgens
hormones which support the male metabolism and secondary sexual characteristics
(Ex: things that are typically male but are not scrotum or penis)
Leydig cells
cells which produce androgens (primarily testosterone)
also called interstitial cells
outside basement membrane
stimulated by LH from the pituitary
sustentacular cells
another name for sertoli cells
interstitial cells
another name for Leydig cells
seminiferous tubules
within each testis
a series of tubules which lead to a central network; which then lead into the epididymis
The tissue lining within generates gametes from a stem cell population; approx 600 per mm of tubule per day
epididymis
where spermatozoa are stored, and undergo final maturation
closely associated w testis inside each scrotal sac
erectile tissue
consists of sponge-like venous passages which fill up with congested blood to make penis erect
Has 3 chambers in penis
Three chambers which become engorged by erection
Corpus spongiosum ~ a midline structure that surrounds the urethra (keeping it open during arousal) and also makes up bulk of glans penis
Corpora cavernosa ~ paired (left and right), each lie in the body of the penis
prepuce
"foreskin"
found on uncircumcised men
partially covering the glans
Summarize path of spermatozoa through duct system; from testes to ejaculation
Released into lumen of seminiferous tubules of testes
Mature in epididymis, wait for ejaculation
Upon sexual stimulation leading to ejaculation, travel via ductus deferens
Critical fluids from seminal vesicles and prostate added
Ejaculation through urethra of erect penis
blood-testes barrier
a basement membrane which separates the capillaries of the testes & interstitial cells from the lining of the seminiferous trubule
spermatogonia
stem cells found along the basement membrane of the seminiferous tubules, farthest from the luminal surface
constantly divideing to either make more stem cells) new spermatogonia OR differentiated cells (primary spermocytes)
What's the process of "making" a spermatozoon
Gametes mature progressively as they move from basement membrane to lumen:
Spermatogonia (mitosis)
Primary spermatocyte (meiosis I)
Secondary spermatocyte (meiosis II)
Early spermatid
Late spermatid (maturation)
Spermatozoa (sperm cell)
Summarize the "sperm itinerary"
Starts w male gametes formed in seminiferous tubules
They collect together in rete testis (network of testicle)
effterent ducts ⇒ ductus epididymis ⇒ ductus deferens
Explain how spermatozoa are motile
Sperm are only cells in human body with flagella
Obviously, it allows them to be motile
Spermatozoon is basically a "missile" (mitochondria for rocket fuel + flagellum) with a "payload" of paternal DNA
rete testis
created by seminiferous tubules collecting together
After being produced in seminiferous tubules of testes, sperm move through here and cross imaginary border into the epididymis
bulbourethral glands
another name for Cowper's glands
efferent ducts
in the epididymis, sperm use this passage to enter ductus epididymis
ductus epididymis
Where sperm wait up to 14 days to mature
If sperm are there longer than 14 days, they will resorb
During maturation, they acquire mobility and ability to fertilize ovum
How does sperm get into the ductus deferens
When sexual activity occurs, a smooth muscle "shell" around epididymis contracts
expelling sperm into the ductus
Cowper's glands
activated when spermatozoa are forced into ductus
They secrete a small amount of alkaline fluid to lubricate and buffer pH of urethra
Also called bulbourethral glands
lie just inferior to prostate, on either side of urethra
Where does the ductus meet the urethra?
the ejaculatory duct (at the prostate)
Here, secretions from the seminal vesicles and prostate are added
Now the fluid is semen and can now be ejaculated
Explain process of ejaculation
Is a sympathetic reflex coordinated by lumbar spinal cord
Internal urethral sphincter closes to prevent leakage of urine and backflow of sperm
Contractions of muscles at root of penis result in emission
Summarize the organs involved in semen production
Sperm from testes and epididymis
secretions from seminal vesicles and prostate gland
also a small contribution from bulbourethral glands
Semen facts:
How much spermatozoa/day
How much semen in average ejaculate
How many spermatozoa per mL
What's the pH
Approx 600 spermatozoa/day
Approx 2.5 to 5 mL semen in average ej.
About 100 million spermatozoa per mL (below 20 mill/mL is defined as infertility)
Is slightly alkaline @ 7.2 - 7.7, this helps neutralize acidity of male urethra and female vagina
Explain clotting factors and reliquification of semen
clots about 5 minutes after ejaculation ~ no one knows why, is from different clotting proteins than blood
After about 10-20 minutes, semen liquefies
PSA is one anti-clotting agents
PSA
prostate-specific antigen
one of the major anti-clotting agent in semen
also used to detect prostate cancer in men; however it's controversial how to use PSA levels to detect cancer as there is no evidence to support the relationship
What's the purpose of the seminal fluid
it nutrients semen
provides a buffer
is a fluid medium for delivery of ejaculate
What does the seminal vesicles secretions contribute to seminal fluid
helps w pH
prostaglandins, and fructose (which is major nutrient which powers sperm motility)
Seconday spermatocyte vs. secondary oocyte
the secondary spermatocyte in the male is the haploid
secondary oocyte is the "egg"
What does prostate secretions contribute to seminal fluid
contributes zinc, citrate and the enzyme acid phosphatase (used in forensic testing)
Also gives semen a milky quality
ovum
the female gamete
coitus
sexual intercourse btwn male and female
vulva
collective term for the externally visible parts of female reproductive system
Includes:
mons pubis (mount of adipose tissue)
labia majora (labia = lips) - outer lips (similiar to scrotum in male)
labia minora - inner lips (spread exposes vestibule), forms prepuce of clitoris, covers 2 openings: urethral opening and vaginal opening
external urethral orifice
clitoris
vaginal orifice
hymen
found on younger women
a membranous structure which partially or completely covers the vaginal orifice
A girls "cherry"
Pelvis inflammatory disease
refers to disease of the upper reproductive organs
recall cervix helps keep unwanted organisms out of uterus & upper reproductive organs
STD usually happen at the cervix
ectopic pregnancy
Recall the need for the uterine tube to have enough space for the oocyte and sperm to move around.
If there is any obstruction, such as scar tissue, there can still be enough room for a spermie to move past, but not enough room for an embryo
Therefore, the egg attaches to the uterine tube. This is dangerous
oophorsalpingohysterectomy
the removal of ovaries, uterine tubes, and uterus
What's the "egg" in the female
the oocyte
ova
ovum - plural
female gametes
begin as oocytes
they mature in the ovaries
follicle
a collective term referring to the structure (w/in the ovary) that encloses an oocyte, along w all the surrounding cells that help it grow and mature
In general, the female repro system matures only one follicle per menstrual cycle
Also, as more follicles develop, there will be an increase in estrogen production
When do female reproductive years lie?
Btwn menarche (first menstrual period) and menopause ( the time of last menstruation)
primary oocytes
describes the precursors to ova which undergo their last cell division before birth and remain in a quiescent (dormant) state until after menarche
What influences a follicle (which surrounds a primary oocyte) to begin to change?
under the influence of pituitary hormones and w hormonal feedback from the overaries and uterus
Identify the stages of follicular development in the ovary
Primordial follicles
Primary follicles
Secondary follicle
Mature (Graafian) follicle
Ovulation → secondary oocyte expelled
Corpus luteum
Degenerating corpus luteum
Corpus albicans (scar tissue)
primordial follicle
The very beginning... :-) the smallest follicle
contain a primary oocyte, and a single layer of follicular cells (which, as they develop, will be the estrogen producing cells)
primary follicle
a primordial follicle that has further developed:
still has primary oocyte
now there's multiple layers of follicular cells (granulosa cells- in several concentric layers) supporting the egg w hormones & nutrients
secondary follicle
(was a primary follicle)
Is filling with follicular fuild & now has developed a follicular fluid-filled pocket (an antrum)
The fluid will not only provide the oocyte with nutrients, but it will also help in the detachment of the egg from the wall of the follicle so it can be released
antrum
the follicular fluid-filled pocket, or space, that develops in a primary follicle
after it's formed, the follicle is now a secondary follicle
What happens to the primary oocyte right before it is released (via ovulation)
it finishes meiosis I
Graafian follicle
another name for a mature follicle, also referred to as the tertiary follicle
refers to a follicle that was a secondary follicle, but now the fluid predominates
Thus the follicle is due to rupture (ovulation)
In this phase the oocyte undergoes it's first mitotic division
What happens to all the other follicles
They are lost... will always have one dominant follicle
The rest disintegrate and are reabsorbed
*In the case of having twins, there were two dominant follicles. So it can happen; these would be fraternal twins, since it was from two different eggs
ovulation
a process in which a mature follicle ruptures
In response to a surge of luteinizing hormone (LH) released from the anterior pituitary once each month, the mature follicle ruptures and releases a secondary oocyte
**LORD HAve mercy....
What essentially is responsible for stimulating this whole process that works toward ovulation
HaHa... it's mother nature's evil trick on females
Once a gal hits puberty, it sends pulses of hormones (Gonadotropin releasing hormone) from the hypothalamus
*Recall hormones with "releasing" in it's name comes from the hypothalamus
recall how LH and FSH hormones are released
LH = luteinizing hormone
FSH = follicle-stimulating hormone
BOTH released from the anterior pituitary
The hypothalamus releases GnRH (gonadotropin releasing hormone) into the hypohpyseal portal system; thus the anterior pituitary responds
FSH:
follicle-stimulating hormone
released from the anterior pituitary
is released early in the menstrual cycle
stimulates development of the follicle in the ovary:
promotes the maturation of a primary follicle into a secondary follicle, then into a mature follicle
Therefore, FSH levels rise early in reproductive cycle
How does the follicle respond to LH
a burst of LH causes the mature follicle to rupture, releasing the oocyte
secondary oocyte
an oocyte that has been released from a ruptured follicle
ovarian cycle
refers to the changes in the ovary with each menstrual cycle
estrogens
secreted by secondary and mature follicles
corpus luteum
An endocrine structure which is the remnants of the follicle after it has ruptured & released the oocyte
a yellowish, waxy substance fills the follicle
It secretes estrogen and progesterone
IF CONCEPTION HAPPENS, corpus luteum stays intact and continues to secrete hormones
IF CONCEPTION DOESN'T HAPPEN, it begins to atrophy & turn into a hunk of scar tissue
What job is progesterone and estrogen responsible for
to maintain the lining of the uterus and prepare the womans body for implantation of the fertilized ovum
If fertilization does not occur, or if embryo does not implant, menstruation proceeds
corpus albicans
a knot of scar tissue with no endocrine function, gets reabsorbed
results from the corpus luteum "burning out" if conception doesn't happen after 14 days; it no longer secretes hormones
The sudden drop in hormone output is what begins the next menstrual cycle w the sloughing off of the endometrium menstrual flow
Summarize the "ovarian" cycle
Day 1-14 pre-ovulatory
Day 14 - 28 post-ovulatory
Summarize follicular development in the ovary
primordial follicle
primary follicle
secondary follicle
mature (Graafian) follicle
ovulation - secondary oocyte expelled
corpus luteum
degenerating corpus luteum
corpus albicans (scar tissue)
fimbriae
Latin for "fringe"
Long "fingers" of the uterine tube
acts to "sweep up" the secondary oocyte and send it on it's journey along the uterine tube
takes about a week for the oocyte to traverse the length of the tube
What CAN occurs to the secondary oocyte as it travels through the uterine tube
It can encounter sperm here
if it does, the secondary oocyte rapidly undergoes a cell division to become an ovum
The ovum can now be fertilized by the spermatozoa and become a zygote
zygote
a female gamete that was fertilized by a spermatozoa and genetics combine
after fertilization, the zygote continues it's journey out of the uterine tube and into the uterus, where it will find an inplantation site
Name layers of the uterus
3 layers:
endometrium: inner layer
myometrium: is thickest, middle layer (is smooth muscle)
perimetrium: is outer, connective tissue layer (serosa layer, nearest the pelvic cavity)
endometrium
the inner lining of the uterus, nearest the lumen
Has 3 layers:
simple columnar epithelium
stratum functionalis
stratum basalis
*The stratum functionalis is shed monthly in menstrual cycle
*The stratum basalis is the tissue from which the stratum functionalis generates from
Identify the blood supply of the uterine wall
Blood flows from:
the internal iliac arteries → uterine arteries → arcuate and radial arteries
The radial arteries branch into spiral arterioles, (which are shed along w the stratum functionalis) and straight arterioles (in the basalis, which are not shed)
** I Usually Aint Right... Slap me Silly
Describe venous drainage of the uterus
Simply drains into the uterine veins and then into the internal iliac veins
summarize what happens after ovulation
A secondary oocyte is released from ovary at ovulation
Swept up by fimbriae of uterine tube
Oocyte may encounter sperm in uterine tube
IF IT DOES, secondary oocyte undergoes the final meiotic division to form an ovum
If spermie & ovum unite, zygote is formed
Zygote travels to uterus where it implants
Clarify:
secondary oocyte vs. ovum vs. zygote
A female ovulates & releases a secondary oocyte
When sperm enters egg, and egg finishes meiosis II, THEN it's an ovum
When sperm and egg nuclei actually unite, then it's a zygote
Describe the uterine cycle
Generally the menstrual cycle is 28 days w menstruation lasting 7 days
3 "stages" :
proliferative phase
secretory phase
menstruation
*menstruation and proliferative phases are pre-ovulatory
secretory is post ovulatory
How is "day 1" of the uterine cycle marked?
The menstrual cycle begins with the sloughing off of the previous cycles tissue (the menstrual flow)
The constriction of the arteries leading into the stratum functionalis causes that layer to die and slough off
What happens during menstruation
the stratum functionalis and its associated blood vessels (spiral arterioles and venules) are lost w layer of endometrium
Day 1 of menstrual cycle marked by the sloughing off of tissue that was build during previous cycle, flow can last 7 days depending on person
Proliferative phase of uterine cycle
Time in which the stratum functionalis is rapidly rebuilt, along w arterioles and venules
Begins when menstruation ends, Goes up through about day 14
*Recall main hormone coming from follicle during this time (approx day 5 - day 14) is estrogen, therefore estrogen is in direct correlation of menstrual flow
If one cycle has more estrogen (for whatever reason) there will be an increase in flow
Explain estrogens job
It's influence is pre-ovulation
follicles produce estrogen, estrogen causes rapid growth of stratum functionalis
Other jobs:
~Promote development/maintenance of female repro structures, 2ndary sex characteristics, breasts
~Increase protein anabolism
~Lower blood cholesterol
~Moderate levels inhibit release of GnRH, FSH, and LH
**I Love Rough Sex Inside
secretory phase of uterine cycle
occurs at ovulation, ideally at day 14
the venules and spiral arterioles in endometrium enlarge
this is in preparation for the implantation of the zygote
Hormone that is post-ovulatory coming from corpus luteum is progesterone
~if embryo does implant in uterine lining, will occur about day 21. It will need rich blood supply to build placenta and feed embryo
~If no implantation happens, around day 26 the endometrial lining loses hope and menstruation begins
So what is the job of progesterone
It's influence is post-ovulation
Is secreted by the corpus luteum
Causes the endometrium to mature in preparation for implantation of a zygote
make "potting soil"
pro- in favor of; -gestation
Also:
~works w estrogens to prepare for implantation
~Prepares mammary glands to secrete milk
~Inhibits release of GnRH and LH
menorrhagia
abnormal bleeding (menstrual)
While the average is 36mL per cycle, more than 80mL is considered abnormal
How are the ovarian and uterine cycles synched?
Hormones secreted by pituitary , follicle, corpus luteum and endometrial glands are used to coordinate ovarian and uterine cycles
Summarize what is happening in the ovarian and uterine cycles early in the menstrual cycle
During last half of menstruation, FSH released from anterior pituitary causes one lucky primordial follicle in ovary to start developing.
It becomes a primary follicle
As FSH remains high, the primary follicle develops into a secondary follicle at the beginning of endometrial proliferation phase
Summarize what is happening in the ovarian and uterine cycles in proliferation phase up to ovulation
At beginning of proliferation, a secondary follicle was formed
As it further develops into a mature follicle, it begins secreting estrogens to help maintain the growth & development of the stratum functionalis
At midpoint of cycle, approx day 14, a burst of FSH and LH triggers ovulation which marks beginning of secretory phase
summarize spikes of hormones throughout cycle
At beginning of cycle, FSH spikes a little to encourage follicle development
As follicles develop, a increase in estrogen occurs
At ovulation, LH suddenly spikes to release egg, which then drops back off
That's when progesterone increases, along with a slight increase in estrogen, from the corpus luteum
Once progesterone drops (if not fertilization occurs) triggers menstration
Inhibin
hormone secreted by corpus luteum
Inhibits release of FSH (mostly) and, to lesser extent, LH
Simply keeps body from starting another cycle before it's ready
Relaxin
hormone secreted by corpus luteum
Inhibits contractions of uterine smooth muscle to allow easier implantation (from cycle to cycle)
Plays key role during labor= increases flexibility of pubic symphysis & dilates uterine cervix, also relaxation so baby can drop
parturition
childbirth
Why is estrogen always referred to in the plural sense?
There are 3 different chemicals call estrogens:
E1 estrone is main form found in body during menopause and later
E2 17β-estradiol is the predominant estrogen found in nonpregnant females
E3 estriol is main estrogen during pregnancy & is made by fetal liver
SRY
Sex-determining region Y
All 5 wk embryos start out w indifferent gender
After that, a small region of the Y chromosome kicks into action (SRY)
IF SRY is present & active & not mutated, then embryo develops male gonads
*oddly, is only important gene on Y chromosome
hermaphrodites
more modern term is intersex
describes individuals who had errors in the SRY gene
Therefore, they developed gonads somewhere btwn "SRY-on" and "SRY-off"
Describe analogous structures btwn male & female
The same embryonic structures develop into one thing if SRY is active, another if it's not
Therefore, the same lump of tissue will develop into one thing if its male, another if it's female
Describe analogous structure: gonads
Male: testes
Female: ovaries
Describe analogous structure: paramesonephric (Müllerian) ducts
Male: [degenerate]
Female: uterine tubes, uterus, vagina
describe analogous structure: glans area of genital tubercle
Male: glans penis, corpora cavernosum
Female: clitoris
Describe analogous structure: urethral folds of genital tubercle
Male: penile urethra
Female: labia minora
Describe analogous structure: labioscrotal swellings of genital tubercle
Male: Penis, Scrotum
Female: Labia majora
Male: corpus spongiosum
Female: pubocervical fascia, vestibular bulb
other analogous structures btwn male and female
Male: prostate
Female: Paraurethral glands (G-spot)
Male: bulbourethral glands
Female: greater vestibular glands
Both contribute to lubrication
perineum
the region surrounding the genitals and anus
one area where males & females differ (duh)
Traditionally divided into 2 regions: urogenital triangle and anal triangle
spermatic cord
the channel through which the descent of the male testes from the embryonic position in the abdomen, into the scrotal sac (approx 7 months gestation)
Is a mechanically weak point and common place for inguinal hernias for males
Describe hormonal control in the male for gamete production
Similar to females, GnRH is secreted (from hypothalamus) which acts to secrete FSH or LH
*No follicles in males, duh
FSH acts as stimulant to spermatogenic cells and Sertoli cells of testes
LH acts on Leydig cells of testes, which secrete testosterone...which may be converted to the active form DHT
DHT
dihydrotestosterone
a male hormone that alters secondary sexual characteristics
How is spermatogenesis promoted?
In the presence of FSH, testosterone and androgen-binding protein (from Sertoli cells) promote spermatogenesis
What does the hormone "inhibin" do in males
Controls a negative feedback loop which ensures that sperm are not over-produced
Recall mitosis
Is the reproduction of somatic cells; where DNA content is doubled (during S phase) and then divided equally btwn 2 daughter cells
retains it's ploidy (chromosome content)
Therefore, somatic cells are diploid
diploid
refers to a cell which has two copies of every chromosome
Ploidy vs n number
The ploidy of a cell refers to the number of copies of each chromosome present in the cell nucleus
The n number refers to the number of copies of each unique DNA strand in the nucleus
As each chromosome contains 1 or 2 strains of DNA at different stages of the cell cycle (whether mitotic or meiotic) these numbers do not always coincide
haploid
refers to mature gametes that have only one copy of each chromosome
Therefore, haploid gametes w one DNA strand per chromosome are said to be 1n
In some stages of cell cycle, diploid cells also have 1 DNA strand per chromosome, and hence are 2n
During earlier stages or meiosis or mitosis, each chromosome of a diploid cell has 2 strands of DNA (has a sister chromatid)= 4n
crossing over
an important feature unique to meiosis
In prophase of meiosis I, genetic recombination occurs (scrambling of pieces of chromosome)
Ensures twins are not born years apart
Differences btwn mitosis & meiosis: daughter cells
Mitosis is cell division where DNA of daughter cells is exactly the same sequence as parents (daughters are clones)
Meiosis involves tetrad formation and crossing over
Differences btwn meiosis & mitosis: reduction division or multiplication?
Mitosis preserves the ploidy & n # of cell. Always diploid, and alternates btwn 2n and 4n. Multiplication of n number during S phase, division during M phase.
Meiosis is a reduction division. The precursors of gametes are diploid (2n). The resulting cells are haploid. It's when 2 haploid cells meet, it returns to being diploid.
Differences btwn meiosis & mitosis: cycles or non-cycles
Mitosis is a cyclical process. It repeats
Meiosis is a "one-way street"; once cells become gametes, they cannot ever reproduce new cells except by joining another gamete in fertilization
Describe correlation btwn spermatogenesis with mitosis
Recall in males, gametogenesis begins with the stem cell, spermatogonia
Spermatogonia undergo mitosis to produce a clonal population
As long as they stay near the basement membrane, they remain a stem cell and divide by mitosis
Describe the correlation of spermatogenesis and when/how they go through meiosis
If a spermatogonia leave the basement membrane of seminiferous tubule, they begin the process of differentiation.
They become primary spermatocytes (diploid, 4n)
Primary spermatocytes undergo meiosis I to become secondary spermatocytes (haploid, 2n)
In meiosis II, they split their DNA into individual chromatids (1 copy DNA per cell), so they end up haploid, 1n spermatids
They continue further differentiation but no further changes in DNA content is made, so they end up as haploid, 1n spermatids
Explain meiosis I in oogenesis
OOgonia undergo their last mitotic division in female fetus
Meiosis I begins at that time, generating primary oocytes
The primary oocytes lie suspended halfway through meiosis I for 10-50 years.
Each month after menarche, 5-12 primary oocytes respond to hormonal signals
In general, only 1 progresses to 2ndary oocyte
remaining material becomes first polar body
polar body
first polar body: the remaining genetic material that is "tossed in the garbage disposal" after a primary oocyte progresses all the way through meiosis 1 to form a secondary oocyte
second polar body: only formed is a spermatozoon penetrates the egg, and the 2ndary oocyte is able to complete meiosis II to become an ovum. Again, the left over genetic material from the reduction division
In what circumstances does a 2ndary oocyte complete meiosis II
Once a primary oocyte completes meiosis I and forms a secondary oocyte, that secondary oocyte begins, but doesn't complete, meiosis II.
Meiosis II is only completed is a spermatozoon penetrates the 2ndary oocyte.
Then it completes meiosis II and becomes an ovum (this also generates the second polar body)
pronuclei
describes the female DNA (n DNA content) and male DNA (n) after an ovum is produced (via penetration of sperm into egg)
They remain separate as male and female pronuclei
Eventually they will fuse to form the diploid zygote (2n)
time zero
- of embryonic development
refers to the fusion of the male and female pronuclei to form a zygote
Summarize meiosis I for female
During fetal development, meiosis I begins
After puberty, primary oocytes complete meiosis I, which produces a 2ndary oocyte and a first polar body that may or may not divide again
summarize meiosis II for female
The secondary oocyte begins meiosis II
A secondary oocyte (and first polar body) is ovulated
After fertilization, meiosis II resumes. The oocyte splits into an ovum and a second polar body
Differences btwn male and female gametogenesis
Male: spermatogonia continuously undergo mitosis to generate primary spermatocytes
Meiosis 1 generates 2ndary spermatocytes
Meiosis II generates spermatids
continues throughout lifetime
Female: All oogonia generated b4 birth
Primary oocytes start meiosis I
After completion of meiosis I, just b4 ovulation, Primary oocyte becomes 2ndary oocyte; meiosis II begins
Meiosis II only completed at fertilization
What marks the onset of puberty for both sexes
Males: spermatogenesis
Females: menarche
Also, both are marked by development of 2ndary sexual characteristics
Primary sexual characteristics
Male: penis, scrotum, associated glands
Female: vulva, ovaries, uterine tubes, uterus, associated glands
They define gender
Secondary sexual characteristics
those that are different btwn genders but not definitive
Ex: males tend to be more muscular w deeper voices
Male: body hair on face, chest, pubic region, arms and legs, deeper voice, adams apple
Female: body hair in pubic region, arms and legs, larger breasts, wider hipds
Name some factors that may be responsible for the change in average age of menarche
internal cues
external cues
increased obesity
~adipose tissue acts as an endocrine organ and may alter the developmental clock
penile plesmythograph
an instrument for measuring penile erection
Components of sexual arousal
There are at least 2:
reflexive, mechanical dimension ~ which is obviously easier to study than the other mentioned... also easiest to study in men
spiritual dimension
Who started the study of human sexuality
Thanks be to the landmark studies in 1948 by:
Kinsey, Pomeroy and Martin
They began the field of study
Masters and Johnson advanced the field greatly in the 1960's
Nerves of sexual response
Primarily controlled by autonomic nervous system
Incoming sensory info from structures which produce sexual arousal: S2-S4
Outgoing striated motor and parasympathetic autonomic also S2-S4
Outgoing sympathetic autonomic at T10-T12
The brain clearly influences this basic reflex pathway
What process cause penile erection
Penile erection results from congestion in the corpora cavernosa
3 processes working together:
~relaxation of smooth muscle in corpora cavernosa, allowing blood to fill open spaces in this spongy tissue
~increase in arterial blood flow to penis
~restricted flow of blood out of the penis (venous congestion)
What is released via stimulation of nerves S2-S4
NO (nitric oxide)
VIP (vasoactive intestinal polypeptide)
CGRP (calcitonin gene-related peptide
prostaglandin
What effects on erection does NO play
~ nitric oxide
Promotes dilation of blood vessels through out body
In turn, promotes penile erection by stimulating all 3 processes
sildenafil
Viagra
causes penile erection by inhibiting an enzyme which breaks down an NO-related signaling molecule (PDE5)
Therefore, Viagra blocks PDE5 and prolongs smooth muscle relaxation
What areas in the female are consistently engorged in sexual arousal
only 2 have been found:
the clitoris and vestibular bulb
vestibular bulb
the area surrounding the female introitus
introitus
the entrance to the vagina
what female tissues are homologous to the corpus spongiosum penis in males
the vestibular bulb
the pubocervical fascia (Halban's fascia)
and the paraurethral glands (Skene's glands)
sexual neutrality
the idea that women engage in sexual intercourse because of desire for emotional closeness
Models of female sexual arousal
3 competing models:
Masters n Johnson: based on "male", hydraulic model of sexual arousal
Kaplan: motivational motel
Basson: sexual neutrality
The Masters and Johnson model of female sexual response:
4 stages of sexual arousal
excitement
plateau
orgasm
resolution
Focus is on physiological response; based on modification of male sexual response
Kaplan model of female sexual response
is a modification of Masters and Johnson, but w an additional phase added at beginning & 4 stages compressed to only two
1. Desire ~ a psychological motivation to engage in sexual behavior
2. Excitement ~ similar concept as in Masters and Johnsons model
3. Orgasm ~ reflexive component, w reflexive pelvic muscle contractions
Basson model of female sexual arousal
Based on "sexual neutrality"
posits that emotional intimacy is primary motivator
Once search for intimacy leads to sexual behavior, the physically pleasurable aspects take over, and sexual arousal occurs
sperm capacitation
takes place in the uterine tube
flagella are stimulated to beat more vigorously
# of chemicals (cholesterol, glycoproteins, and proteins) r removed from spermatozoa in preparation to fuse w secondary oocyte
acrosome
the "head" of the sperm
profilactin
unpolymerized actin in acrosome of spermatozoon
acrosomal reaction
the process of converting profilactin into actin
this helps spermatozoon penetrate the secondary oocyte
describe dizygotic twins
fraternal
occur when 2 oocystes are shed, usually one from each ovary
monozygotic twins
occure when the zygote splits into two embryos in an early division
identical twins
What happens in the rare case 2 spermies penetrate an oocyte
fertilization doesn't occur
This is POLYSPERMY... the idea that it's possible for more than one sperm to enter the oocyte
blocks to polyspermy
there are at least 2:
Block to polyspermy
One is fast (which is very detailed), the other is slow (which involves the cortical reaction)
Two layers surrounding the oocyte which sperm must penetrate
corona radiata
zona pellucida
corona radiata
"radiant crown"
made by granulosa cells from the follicle
partially surround the ovulated secondary oocyte
outer layer
zona pellucida
the inner layer surrounding the ovulated secondary oocyte sperm must penetrate
is a thick, clear layer
cortical reaction
caused by the penetration of the oocyte by the 1st spermatozoon
causes Ca++ to be released from cortical granules in the oocyte
This lifts the zona pellucida off egg, making it impossible to pass
Unless the zona pellucida is in close contact w oocyte, sperm can't penetrate
Define fertilization
When the sperm and egg unit
Forms a diploid = zygote
Is the moment which starts out developmental "clock"
Describe first week after fertilization
the embryo travels from uterine tube, where fertilization almost always occurs near distal end of tube,
Along the way, it continues the process of mitotic cell division
two-cell embryo
results from the first division of the zygote, resulting in two symmetrical, equal cells
*the splitting of the cell at this point will result in monozygotic twins forming
four-cell embryo
next division of embryo, takes place on day 2
produces 4 equal, almost identical cells
morula
the stage after four-cell embryo; seen at day 4
when simple pattern of cell division is lost
"raspberry"
blastocyst
when the embryo forms a hollow, fluid filled ball
seen about day 5
What leads to implantation
happens about day 6
blastocyst makes contact w endometrium of uterus
Inner cell mass develops
Problem: embryo is "foreign issue (half of genes not from mom)
so involves evading mother's defense mechanisms (since dad's DNA is foreign)
Inner cell mass
develops when the point of contact btwn blastocyst and endometrium causes uterus to release chemical factors
implantation
days 8 - 12
Upon implantation, the blastocyst divides into three parts:
~trophoblast
~innercell mass→ embryonic disc
~yolk sac
The endometrial lining becomes the decidua
By day 12, embryo is completely covered by endometrial tissue
Gastrulation
Happens approx day 16
the process by which an embryo folds in on itself to form 3 layers:
ectoderm ~ becomes skin & nervous system
mesoderm ~ becomes connective tissue, muscles and bones
Endoderm ~ becomes gut tube
carcinoma vs. sarcoma
When cancer occurs, it's named by tissue of origin
Carcinoma refers to tissue from the ectoderm
Sarcoma refers to the tissue from the mesoderm
Name ectoderm derivatives:
epidermis
teeth
jaws
nervous system
posterior pituitary
**Every Tom & Joe Needs Pussy
Name Mesoderm derivatives:
Somites
Kidneys
Heart
Reproductive system
Gonads
**Sadly Kissing Happened Regularly, George
Name endoderm derivatives
Lungs
bladder
Thyroid
Liver
Pancreas
Lining of digestive tract
**Please... Let The Bitch Lie Longer??
What is the breakdown of somites (from the mesoderm derivatives)
Look like little "speed bumps" of the mesoderm, when form into:
dermatome = dermis
sclerotome = vertebrae
myotome = skeletal muscles, appendicular skeleton
decidua
term used for the uterine lining during pregnancy
extraembryonic membranes
represent a collaboration btwn mom & baby
Deals with the fact that the embryo is different from mom's tissues (is foreign) and also convinces mom to feed and protect embryo
The joint project is called the placenta
placenta & function
a joint project btwn mother and baby
is half embryonic tissue & half maternal
Placenta will:
provide food to embryo
Provide oxygenated blood to embryo
Protect embryo from invaders w maternal antibodies (only IgG antibodies can pass placental border)
How does the placenta begin
With the development of lacunae (open spaces) which form immediately after implantation
chorionic villi (pl), chorionic villus (sing)
loops of blood vessels formed by embryonic tissue
important as the first structures of developing embryo that can be biopsied to detect genetic defects of the embryo
Since this is completely derived from embryonic tissue, and not maternal tissue, and chromosomal abnormalities can be fully attributed to embryo
Most common detected is trisomy 21 (downs)
Chorion
the circular "wall" around the entire embryonic project area
nondisjunction
chromosomal abnormalities, can occur during meiosis I or Meiosis II
Recall w meiosis, all 4 chromatids r suppose to arrive in different daughter cells
In nondisjunction, chromatids fail to separate and both go to the same cell: one gamete get two copies of chromatid 21
Therefore, at fertilization, Dad contributes one copy, Mom contributes 2, so child ends up with 3 copies
What resulting X & Y combinations can there be with Trisomy 21
Resulting embryo can be
XXX, XXY, XO, or YO
YO embryos do not survive
List blood flow btwn mom and baby
maternal circulation ⇛
maternal endometrial arteriole ⇛
fetal blood vessels in chorionic villi ⇛
umbilical vein (IS OXYGENATED BLOOD) ⇛
embryo ⇛
umbilical artery (IS DEOXYGENATED BLOOD) ⇛
fetal blood vessels in chorionic villi ⇛
maternal endometrial venule
Anlagen
The initial clustering of embryonic cells from which a part or an organ develops
organogenesis
The time when individual organs start to develop from precursor tissues found in the appropriate layer
begins once gastrulation has occurred & 3 embryonic layers are formed
Day 20-28
neural folds
a prominent feature of the dorsal surface of embryo, forming a distinct groove
The lips of this groove meet to form a neural tube, which will twist and fold to form the brain
critical period
time when systems are sensitive & can be harmed by teratogens
when a system can be changed
during the embryonic period
teratogens
substances that can cause birth defects
Ex:
rubella ("german measles")
toxoplasma (cat feces)
radiation
cytomegalovirus
embryonic period
defined as fertilization to 8 weeks
After this time, the fate of most organ systems is set
Fetal period
9 weeks to 40 weeks
There is growth and development, but most of fetal period involves the organs carrying out developmental plan set out during the embryonic period
4 hormones that are released directly by the placenta
hCG (human chorionic gonadotropin)
relaxin
hCS (human chorionic somatomammotropin)
CRH (corticotropin-releasing hormone)
hCG
human chorionic gonadotropin - hormone released by placenta
released by chorionic membrane, acts on gonads
Supports the function of the corpus luteum, keeping it "alive" for about 3 more months
Basis for home pregnancy testing
relaxin
hormone released by placenta that helps at childbirth by making pubic symphysis more flexible, and aiding in dilation of cervix during labor
hCS
human chorionic somatomammotropin - hormone released from the placenta
alters maternal metabolism, increasing protein synthesis to enhance growth
decreasing glucose use and increasing fatty acid use for ATP
CRH
corticotropin-releasing hormone - released from placenta
establishes the time of birth and increases cortisol secretion from the adrenal cortex
Hormone Levels vs. gestational age
Spike of hCG is earliest, peaking btwn 8-10 wks
Slow rise in progesterone and estrogens from maintenance of corpus luteum:
levels of estrogens rise steadily through pregnancy
levels of progesterone rise steadily, but begin to drop slightly at end of pregnancy
Cardiovascular changes during pregnancy
increased blood flow to placenta (duh)
⇧ stroke volume
⇧ cardiac output
⇧ heart rate
⇧ blood volume
compression of inferior vena cava, leading to edema in legs and varicose veins
compression of renal artery may lead to renal hypertension
Respiratory changes during pregnancy
⇧ tidal volume
⇧ ventilation
⇧ total oxygen consumption
⇩ expiratory reserve volume
dyspnea possible
Urinary changes during pregnancy
increased urination due to fetus sitting on bladder, duh
increased glomerular filtration rate
toxemia of pregnancy
pre-eclampsia
cardial signs are rapid rise in BP to hypertensive levels & proteinuria
HELLP syndrome
Life-threatening condition
Hemolytic anemia, Elevated Liver enzymes, Low Platelet count
3 stages of labor
dilation stage
expulsion stage
placental stage
dilation stage of labor
From onset of labor to dilation of cervix
Lasts about 6-12 hours
regular contractions
Usually rupturing of amniotic sac
Ends w complete diation
The estrogen/progesterone ratio, increased maternal oxytocin release, and increased fetal oxytocin release probably play a key role in initiating parturition
Expulsion stage
can last 10 minutes to several hours
begins w dilation of cervix, ends with delivery
Placental stage
The final stage to labor
can last 5 to 30 minutes
Ends w expulsion of placenta
Powerful uterine contractions expel placenta and help control bleeding
Describe feedback loop of labor
Is rare example of positive feedback loop
Input: stretching of cervix sends sensory info to brain
Processing & output: brain interprets signal, releases oxytocin from posterior pituitary
Oxytocin causes uterus to contract more forcefully
This pushes baby further into cervix, increasing stretch
Delivery of baby stops feedback loop
*Synthetic oxytocin (Pitocin) can be used to stimulate this homeostatic loop
milk let-down reflex
another positive feedback loop associated with childbirth
allows newborn to suckle
Only involves releasing stored milk
Input: baby sucks nipple
Processing & output: hypothalamus and posterior pituitary
Releases oxytocin which stimulates "milk let-down reflex"
Cycle continues until baby stops suckling
mammary glands
are modified sudoriferous (sweat) glands which produce milk
Alveolar glands w/in fat tissue of breast are surrounded by myoepithelial cells, which contract in response to oxytocin
This ejects milk from alveoli
summarize breast structure
Bulk of breast is adipose tissue, embedded within are alveolar glands
15-20 lobes per breast, separated by fat tissue
lobes have lobules that contain alveoli
Coopers ligaments
also referred to as suspensory ligaments
maintains structure of breast
become stretched throughout life
Whats the probability of concenption
from a single, unprotected act 2-4%
Peak probability of conception if at days 12-14
Sperm survive 3 days, so intercourse slightly after ovulation has higher probability of conception than intercourse after ovulation