Download Chapter 27

Chapter 27
1) Asexual and sexual reproduction
a) reproduction
i)
creation of new individuals from existing ones
ii) only life function now required for survival of
individual
iii) required for survival of species
b) Asexual reproduction
i)
one parent
ii) ex. desert-grassland whiptail lizard
(1) reproduces only asexual
(2) female makes egg that does not get fertilized resulting
in clone of female
iii) Types
(1) budding
(a)splitting off of new individual from existing one
(i) Fig. 8.11C – budding hydra
(2) fission
(a)one individual separates into two or more of equal
size
(i) Fig. 27.1A – sea anemone
(3) fragmentation
(a) breaking of parent body into several pieces
(b) must be accompanied by regeneration
(c)regeneration
(i) regrowth of body parts
(ii) sea star loses arm and grows new one back
(d) example of fragmentation - sea star Linckia
(i) arm breaks off
(ii) arm can regenerate a whole new organisms
(iii) if all five arms break off, five offspring are result
iv) advantages
(1) allows animals that can’t move easily or live in
isolation to reproduce
(a)ex. desert-grassland whiptail
(i) single female ancestor isolated
(2) many offspring, quickly
(a)no time, energy lost in meiosis and fertilization
(3) quickly expand a successful genotype
v)
disadvantages
(1) genetically identical
(a)remember the little birdy whose name was Enza…
(b) if environment changes and one can’t make it, they
all can’t make it
c) sexual reproduction
i)
creation of offspring by fusion of haploid gametes
(fertilization) to form diploid zygote
(1) sperm – male gamete, tiny, moves by flagellum
(2) ovum – female gamete, relatively large, not selfpropelled
ii) recombination (reshuffling) of genes (meiosis and
random fertilization) generates great variation among
offspring
iii) advantage
(1) environment changes and some members of species
likely to survive it just by chance (influenza 1918)
d) many animals can do both (asexual and sexual reprod.)
i)
Fig. 27.1B – rotifer (microscopic)
(1) freshwater lakes and ponds
(2) eat bacteria, algae, protozoa (primary and secondary
consumers)
(3) asexual reproduction
(a)when lots of food and optimum water temp. for rapid
growth and development – make more, quick in
great conditions
(b) unfertilized eggs made by mitosis
(4) sexual
(a)cold
temps. signaling winter, food shortage, lake
starts to dry up (environment changing to
unfavorable)
(b) fertilized eggs have thick shells that can withstand
drying and freezing
(c)best to shuffle your alleles if you don’t know what is
coming…
e) Sexual reproduction is a problem from solitary and
nonmobile animals…
i)
Natures solution: hermaphroditism
(1) both female and male reprod. systems
(2) from greek myth where hermaphroditis (son of Hermes
and Aphrodite) fused with a woman to become a single,
bisexual individual
(3) some species can fertilize own eggs
(a)tapeworms
(4) mating must occur in most hermaphroditic animals
(a)when mating, both animals serve as male and female
(i) they fertilize each others eggs
1. earthworms (annelida)
(5) every individual encountered is a potential mate
(6) offspring from both individuals in a single mating
f) mechanics of fertilization
i)
external fertilization
(1) many aquatic invertebrates and most fish and
amphibians
(2) gametes discharged into water
(a)often without physical contact
(b) gametic isolation
(c)timing is crucial
(i) environmental cues like temperature and day
length signal release of sperm and eggs in certain
clams, etc…
(ii) release chemical signal as gametes are released
triggering release in opposite sex
(iii)courtship
rituals
1. most fish and amphibians
2. trigger simultaneous release in same vicinity
3. Fig. 27.1D
ii) Internal fertilization
(1) sperm deposited in or close to female reproductive tract
(2) egg fertilized within female
(3) nearly all terrestrial animals
(4) protects egg from excessive heat and drying
(5) requires copulation (sexual intercourse)
(a)need complex reproductive equipment
(i) copulatory organs
(ii) receptacles for sperm storage and shipping to egg
2) Human reproduction
a) Female anatomy
i)
Figure 27.2A
(1) ovaries
(a)inch long
(b) bumpy surface caused by follicles
(c) follicle
(i) a single developing egg
(ii) surrounded by follicle cells
1. protect and nourish egg cell
(iii) produce estrogens
(d) female born with 40,000 to 400,000 follicles
(i) only several hundred will release egg cell
(e)ovulation (Fig. 27.2B)
(i) ejection of egg cell from follicle
(ii) one follicle (two or more in rare cases) releases
egg every 28 days starting at puberty and ending
at menopause
(f) corpus luteum (“yellow body” – latin)
(i) this is what the remaining follicle tissue becomes
after ovulation
(ii) secretes
progesterone
1. helps maintain uterine lining during pregnancy
(iii)secretes additional estrogens
(iv) degenerates if egg is NOT fertilized
(v) new follicle matures during next cycle
(2) oviduct (fallopian tube)
(a) opening is like a funnel with fingerlike projections
(b) projections touch ovary
(c) tiny space separates ovary and oviduct
(d) egg passes through tiny space and into oviduct where
cilia sweep it towards uterus
(e)fertilization will occur in upper third of oviduct
(f) zygote will begin mitosis and become and embryo
(fertilization to 9th week when body structures begin
to form in humans, after 9th week it is a fetus) as it
continues to move down oviduct towards uterus
(3) uterus (womb)
(a)site of pregnancy
(b) 3 inches long in women never pregnant
(c)can obviously expand quite a bit during pregnancy
(d) thick muscular wall
(e) endometrium
(i) lining of uterus
(ii) loaded with blood vessels
(f) embryo digests a place for itself in endometrium
(g) ectopic (out of place) pregnancy
(i) when embryo implants in a place other than uterus
(ii) tubal pregnancy
1. when they occur in oviduct (most)
(iii)require surgical removal otherwise will rupture
tissue and cause internal bleeding (death)
(4) cervix
(a)narrow neck of uterus
(b) opens into vagina
(5) vagina
thin-walled, strong, muscular chamber
(b) birth canal
(c)repository for sperm during copulation
(d) just behind urethral opening
(6) labia minora
(a)skin folds that border opening
(7) labia majora
(a)thick, fatty ridges
(b) cover and protect entire region
(8) hymen
(a)thin membrane that partly covers vaginal opening
(b) ruptures by sexual intercourse or vigorous physical
activity
(c)no known function
(9) Bartholin’s gland
(a)secretes lubricating fluid during sexual arousal along
with vaginal lining
(10) clitoris
(a)engorges with blood during sexual activity along with
labia minora and vagina
(b) sole function is sexual arousal
(c)three parts
(i) shaft – supports glans
(ii) glans (head)
1. enormous number of nerve endings
2. sensitive to touch
a. can trigger orgasm
(iii)prepuce – skin covering glans
b) human male reproductive anatomy (Fig. 27.3AB)
i)
scrotum
(1) house testes (male gonads)
(2) outside abdominal cavity
(a)sperm cannot develop at body temp.
(b) scrotum keeps sperm cool outside body
ii) Tracking the path of sperm
(a)
(1) epididymis
(a)coiled
tube
(b) sperm is stored here until development is complete
(2) ejaculation
(a)sperm leaves the epididymis
(b) expulsion of sperm from the penis containing fluid
(c)muscular contractions propel sperm from epididymis
to vas deferens
(3) vas deferens
(a) duct that pass up into abdomen, around bladder
(4) seminal vesicle (there are two)
(a)secretes a thick, clear fluid that protects and nourishes
sperm
(b) duct of seminal vesicle meets with duct of vas def.
(c)combined duct = ejaculatory duct
(5) prostate gland (one)
(a)ejaculatory duct passes through this gland
(b) secretes milky, alkaline fluid
(i) balance acidity of traces of urine in urethra
(ii) protect sperm from natural acidity of vagina
(6) bulbourethral gland (two)
(a) secretes a few drops of fluid into urethra during
sexual arousal
(b) may help lubricate for sperm movement
(c)duct of this gland forks with ejaculatory duct
(7) urethra
(a)conveys both sperm and urine (unlike females)
(i) NOT at the same time
(ii) connection b/w reprod. and excretory system
iii) semen
(1) sperm plus ejaculatory fluids
(2) 5ml discharged typically
(3) 95% glandular secretions
(4) 5 % is 200-500 million sperm
(a)only one can fertilize egg
iv)
penis
(1) tissue that can fill with blood causing erection during
sexual arousal
(a)erectile tissue shown in blue in Fig. 27.3AB
(b) essential for insertion into vagina
(c)parts of penis (similar to clitoris)
(i) shaft
(ii) glans (head)
1. many nerve endings
2. sensitive to touch
(iii)prepuce (foreskin)
1. skin that covers glans
2. removed via circumcision
v)
Two stages of ejaculation
(1) stage one (build-up stage)
(a)muscles in epididymis, seminal vesicles, prostate, vas
deferens contract (upper drawing Fig. 27.3)
(b) force secretion and sperm into and down vas def
(c)sphincter at bladder base contracts preventing leakage
of urine
(d) second sphincter contracts, closes off entrance to
urethra to penis (keeps semen from entering)
(i) build up of semen causes expansion and pressure
on vas def.
(2) stage two (expulsion stage)
(a) sphincter relaxes (second one)
(i) semen allowed to enter penis
(b) muscles contract simultaneously around base of
penis and along urethra expelling semen
vi) control of sperm production
(1) hypothalamus (controlled by other parts of brain)
secretes releasing hormone
(2) releasing hormone stims. AP to secrete FSH and LH
(3) FSH
(a)increases sperm production by testes
(4) LH
(a)promotes
secretion of androgens (mainly
testosterone)
(5) androgens
(a)stim. sperm production
(b) maintain homeostasis by neg. feedback
(i) inhibit secretion of releasing hormone and LH
(6) testes produce 100’s of millions of sperm per day from
puberty well into old age
c) formation of sperm and ova
i)
both are haploid
ii) develop by meiosis
iii) spermatogenesis (Fig. 27.4)
(1) formation of sperm cells
(2) takes 65-75 days
(3) seminiferous tubules
(a)site of sperm generation (spermatogenesis) in testes
(b) coiled tubes
(c)diploid cells near outer wall
(i) undergo MITOSIS constantly to keep a constant
supply
(ii) 3 million become primary spermatocytes per day
(4) primary spermatocytes
(a)cells that undergo MEIOSIS (diploid)
(5) secondary spermatocytes
(a)produced after meiosis I (there will be two of course
for each primary spermatocyte)
(b) haploid number (double chromatids)
(6) sperm
(a)meiosis II produces 4 haploid cells (single
chromatids)
(b) these cells differentiate into sperm
(i) 4 sperm per primary spermatocyte
(7) developing sperm cells move closer and closer to center
of tubule (Fig. 27.4A)
(8) passes into epididymis, matures and becomes mobile
iv)
oogenesis (Fig. 27.4BC)
(1) development of an ovum
(2) mostly occurs in ovary
(3) reminder: ovary contains all follicles it will ever have at
birth
(4) begins prior to birth
(a)diploid cell in each follicle begins meiosis
(5) at birth
(a)each follicle contains a primary oocyte
(i) arrested at prophase I
(ii) needs to be hormonally triggered to continue
(6) at puberty and every 28 days after until menopause
(a) FSH from AP stim. one follicle to develop
(i) follicle enlarges
(ii) primary oocyte completes meiosis I
1. there is an unequal division of cytoplasm
2. results in two haploid (double chromatid) cells
a. secondary oocyte
i. gets most of cytoplasm
ii. arrests at metaphase II
iii. released by ovary during ovulation –
triggered by LH
b. other cell (first polar body)
i. undergoes meiosis II
ii. resulting cells broken down and recycled
(7) in the oviduct
(a)secondary oocyte
(i) if fertilized, meisosis II will be completed
(ii) unequal division of cytoplasm again
(iii) result
1. ovum (haploid)
a. nucleus fuses with nucleus of sperm
2. second polar body (same fate as first)
(8) remaining follicle becomes corpus luteum
(a)degenerates
if fertilization does not occur
v)
Differences b/w spermatogenesis and oogenesis
(1) 4 sperm cells vs. one ovum
(2) ovary contains all primary oocytes at birth vs. new
primary spermatocytes produced continuosly
throughout life
(3) oogensis needs stim. by sperm cell to complete
d) Hormones synchronize cyclical changes in the ovary and
uterus
i)
ovarian cycle (Fig. 27.5 – part 3)
(1) cycle of events occurring every 28 days in female
(2) three parts
(a)pre-ovulatory phase – follicle growing and secondary
oocyte develops
(b) ovulation – release of sec. oocyte
(c) post-ovulatory phast – formation and degeneration of
corpus luteum
ii) menstrual cycle (Fig. 27.5 – part 5)
(1) cycle of events occurring in uterus
(2) build up and breakdown of endometrium
(3) first day = day 1 of woman’s period
(4) menstruation
(a)uterine bleeding (blood, endometrium cells, mucus)
(b) lasts 3-5 days
(c)endometrium breaks down and leaves through vagina
(d) coincides with growing follicle in ovarian cycle
(5) regrowth of endometrium
(a)thickens through ovulation
(b) max at day 20-25
(c)no embryo, prepares for menstruation again
iii) How are these two cycles synchronized? ovarian and
menstrual cycle synchronized by hormones (its just
dominoes)
(1) five hormones (table of page 542)
(a)releasing
hormone from hypothalamus regulate
release of FSH and LH from AP like in males
(b) estrogen and progesterone
(2) hormonal events before ovulation (Fig. 27.5)
(a) RH stims release of FSH and LH from AP
(i) FSH – stims growth of follicle
(ii) follicle in turn secretes estrogen
1. amount depends on size of follicle
2. rising (still low) level of estrogen applies neg.
feedback to pituitary
3. keeps FSH and LH relatively low for most or
pre-ov phase
4. estrogen reaches critical peak just before
ovulation (follicle is very large)
5. high estrogen exerts positive feedback on
hypothalamus
6. bursts of FSH and LH secreted
7. put a piece of paper over Fig 27.5 and slide to
right to follow hormone levels
(3) hormonal events at ovulation and after
(a) role of FSH unknown after follicle matures
(b) LH peak
(i) stims completion of meiosis I
1. primary oocyte to secondary
(ii) signals enzymes to rupture follicle allowing
ovulation
(iii)triggers dev. of corpus luteum (CL) from ruptured
follicle (hence luteinizing hormone)
(iv) promotes secretion of progesterone and estrogen
by CL
(c) progesterone and estrogen
(i) high levels after ovulation
(ii) influence ovary and uterus
(iii)combination of both apply neg. feedback to
hypothalamus
FSH and LH levels fall
a. prevents ovulation and follicle development
b. LH drop results in degeneration of CL
c. CL eventually stops secreting progesterones
and estrogens
d. neg. feedback removed from hypothalamus
e. FSH and LH secreted again to start cycle
once more
(4) control of menstrual cycle
(a) controlled by estrogen and progesterone alone
(b) high levels trigger thickening of endometrium
(c)low levels trigger release of endometrium
(5) remember, this is in the absence of fertilization
(6) these cycles are put on hold if fertilization and
pregnancy occur
(a)developing embryo releases a hormone
(i) HCG – human chorionic gonadotropin
1. acts like LH
2. maintains corpus luteum
3. is not influence by estrogen and progesterone
levels
4. progesterone and estrogen keep being made
5. endometrium stay intact
e) human sexual response occurs in four phases
i)
most female mammals are receptive to males only on
certain days
(1) for certain species, only certain time(s) a year
(a)deer and bear mate only during autumn
(2) estrus – female is primed for implanation and ovulation
will occur shortly
ii) humans are several other primates are unique
(1) unique in having no distinct mating period
(2) sexuality is emotional as well as physical
(3) four phases in humans
(a)excitement phase
1.
passion builds; penis and clitoris erect; testes,
labia and nipples may swell; vagina secretes
lubricating fluid; muscles tighten in arms and legs
(b) plateau phase
(i) increased breathing and heart rate
(c)orgasm
(i) rhythmic contraction of reproductive structures,
extreme pleasure for both, ejaculation by male
(d) resolution phase
(i) reverse all previous responses
f) disease
i)
STDs – sexually transmissible diseases
(1) Table on page 544
g) contraception prevents unwanted pregnancy (Table –pg. 545)
i)
contraception
(1) deliberate prevention of pregnancy
(2) effective to varying degrees
(3) only abstinence is 100%
(4) three ways
(a)prevent release of gametes from gonads
(i) birth control pills
1. combination of synthetic estrogen and
progesterone-like hormones (progestin)
2. prevents ovulation and keeps follicles from
developing (look at Fig. 27.5)
3. Cardiovascular side effects a concern
(b) prevent fertilization
(i) progestin minipill, implant,
1. alters mucus of vagina so sperm can’t get into
uterus
(ii) sterilization
1. vasectomy
a. cut section out of each vas deferens
b. sperm can’t enter urethra
2. tubal ligation
(i)
a. cut short section out of each oviduct
b. tie or ligate ends to each other
c. egg can’t get to uterus
3. both are difficult to reverse and should be
considered permanent
(iii) rhythm method (natural family planning)
1. don’t have sex around ovulation
a. hard to predict ovulation
b. not very effective
(iv) withdrawal
1. removal of penis before ejacualtion
2. no very effective – sperm leaks before
(v) barrier methods
1. physically stop sperm from moving into uterus
and oviducts
2. condoms
a. thin, latex sheaths that fit over penis or in
vagina
3. diaphragms
a. dome-shaped rubber cap that covers cervix
b. must be used with spermacides
(c)prevent embryo from implanting
(i) intrauterine devices (IUD)
1. small plastic or metal devices inserted by a
doctor into uterine cavity
2. harmful in small percentage of women
(ii) morning after pills
1. high doses of birth control
2. taken within 3 days of intercourse
3. 75% effective
h) Fertilization results in a zygote and triggers embryonic
development
i)
fertilization
(1) union of sperm and ovum to form diploid zygote
ii) properties of sperm cells (Fig. 27.9AB)
(1) only one can fertilize egg – the lucky genes
(2) all other sperm will die
(3) form-function
(a)streamlined
for swimming
(b) head of sperm
(i) haploid nucleus
(ii) acrosome
1. membrane enclosed sac
2. contains enzymes that help sperm penetrate egg
(c)neck and middle piece
(i) long, spiral mitochondrion
(ii) sperm absorbs fructose from semen
(iii)mito. provide ATP for long swim (move
flagellum)
(d) flagellum = tail
iii) The process of fertilization (Fig. 27.9)
(1) based on sea urchin research
(2) Three barriers sperm nucleus must pass
(a)jelly coat
(i) digested by enzymes in acrosome
(b) vitelline layer
(i) proteins on surface of sperm bind to specific
receptors on surface of vitelline layer
1. gametic isolation
a. really important in external fertilization
(c)plasma membrane (PM)
(i) after receptor-ligand complex forms, PM of sperm
fuses with PM of egg
1. nucleus enters
2. induces changes in egg
a. PM becomes impenetrable to other sperm in
less than a second
b. vitelline layer hardens and separates from
PM
i. space b/w vitelline layer and PM fills
with fluid
ii. vitelline layer now called fertilization
envelope (FE)
iii. FE is impenetrable to sperm
(3) egg and sperm nuclei fuse
(4) egg gears up metabolic machinery for growth
i) embryonic development – 2 major phases
i)
Cleavage (Fig. 27.10)
(1) rapid succession of cell divisions
(2) produces a ball of cells from zygote
(3) cell division is occurring rapidly
(4) gene transcription is virtually shut down (no new
proteins being made)
(a)embryo does not grow larger, just more cells
(5) takes ~3 hours in sea urchin (20min per division)
(6) result is blastula
(a)fluid filled ball of cells
(b) blastocoel = fluid filled center
(7) multicellular embryo is partitioned into developmental
regions (review 11.2 – mRNA/protein gradients in
embryo)
ii) gastrulation
(1) adds more cells
(2) sorts cells into distinct layers
(3) blastula (hollow ball) develops into gastrula (threelayered stage)
(a)ectoderm
(i) outer layer (skin) of gastrula
(b) endoderm
(i) embryonic digestive tract
(c)mesoderm
(i) partly fills space b/w ecto- and endoderm
(4) three layers will eventually form all parts of adult (table
on page 551)
– nervous system and outer skin
(b) endoderm – inner most lining of digestive tract and
resp system, liver, pancreas, lots of inner linings of
systems
(c)mesoderm – circ. system, skeletal sys, muscular
system, excretory sys, reprod. sys
(5) mechanics of gastrulation
(a)vary from species to species
(b) Fig. 27.11 shows the frog
(c)takes ~15-20 hours (depends on species)
(i) the blastula
1. animal pole vs. vegetal pole
a. animal pole has smaller cells
b. vegetal pole cells have yolk granules
i. divide slower
(ii) blastopore formation
1. small groove on one side
2. marks beginning of gastrulation
(iii)cell migration to form layers
1. archenteron – simple digestive cavity formed
by endoderm cells
(iv) completion of gastrulation
1. ectoderm covers almost entire surface
2. yolk plug remains on surface
a. site of blastopore and future anus
3. blastocoel replaced by archenteron
j) organs start to form after gastrulation
i)
cells begin to differentiate into tissues and embryonic
organs
ii) Fig. 27.12A – frog embryo
(1) Notochord
(a)forms from mesoderm
(b) made of cartilage like substances
(c)extends length of embryo, provides support
(d) will develop into backbone of vertebrates
(a)ectoderm
(2) hollow nerve cord (Fig. 27.12B)
(a)formed
from ectoderm
(b) neural plate
(i) thickened region of ectoderm
(c)neural folds
(i) ectodermal ridges
(ii) rise from neural plate
(d) neural tube
(i) formed from neural plate folding and sinking
below surface
(ii) will become brain and spinal cord (Fig. 27.12C)
iii) Fig. 27.12 C (12 hours after 27.12A)
(1) embryo has elongated
(2) beginnings of eye and tail
(3) somites
(a)blocks of mesoderm giving rise to segmented
structures like vertebrae
(b) coelom
(i) hollow space formed by mesoderm
iv) Summary
(1) cleavage, gastrulation, organ formation
(2) understand how a single zygote becomes multicellular
organisms is one of the great challenges of biology
3) Human development
a) embryo and placenta take shape during month 1 of pregnancy
i)
gestation = pregnancy
(1) carrying of developing young in reprod. tract
(2) begins with conception and ends with birth
(3) 38 (~9 months) weeks in humans
(4) 1 month in mice
(5) 22 months in elephants
ii) cleavage starts 24 hours after fertilization
iii) embryo reaches uterus 6-7 days after fert.
(1) 100 cells now – blastocyst (mammalian blastula)
iv)
blastocyst (Fig. 27.16C)
(1) fluid filled cavity
(2) inner cell mass that will form baby
(3) trophoblast
(a)outer cell mass
(b) secretes enzymes to allow for implantation
(digestion of endometrium)
(c)moves into endometrium (roots)
(d) will eventually form part of placenta
(e)placenta
(i) organ that provides nourishment and O2 and get
rid of waste from embryo
(ii) made of both embryonic and maternal tissue
v)
four extraembryonic membranes (mammals, birds and
reptiles)
(1) made from yellow cells, some purple and some tropho.
(2) help support embryo – life support system
(3) Types (Fig. 27.16D)
(a) amnion (from purple cells)
(b) yolk sac (from yellow cells)
(c) chorion (part from tropho.)
(d) allantois (extension of yolk sac) (Fig. 27.16E)
vi) gastrulation
(1) started 9 days after conception
(2) Fig 27.16D
(3) embryo forms from three inner layers (Fig. 27.16E)
vii) roles of extraembryonic membranes
(1) Fig. 27.16F (31 days after conception)
(2) amnion
(a)grown to enclose embryo
(b) amniotic cavity filled with protective fluid
(3) yolk sac
(a) provides nourishment in reptiles (eggs)
(b) mammals – remains small
produces first blood and germ cells (cells that give
rise to gamete forming cells)
(4) allantois
(a)mammals
(i) remains small
(ii) part of umbilical cord
(iii)part of urinary bladder
(b) birds and reptiles
(i) surrounds embryo and involved in waste disposal
(5) chorion
(a) embryos part of placenta
(b) secrete HCG
(i) maintains corpus luteum for first 3 months
(ii) what if HCG were not secreted?
viii) the placenta
(1) chorionic villi
(a)knobby outgrowths of chorion and mesoderm
(b) contain embryonic blood vessels
(i) developed from mesoderm
(c)closely associated with blood of moms endometrium
(DO NOT touch each other – blood is separate)
(d) bath in pools of moms blood
(e)absorb nutrients and O2 and get rid of wastes
(i) mother gets rid of waste
(2) allows antibodies to pass from mom to baby
(3) can be trouble
(a)depends on what is circ. in moms blood
(i) alcohol
1. fetal alcohol syndrome
a. group of disorders (includes mental
retardation)
(ii) drugs
(iii)chemicals in tobacco smoke
(iv) many viruses can cross – german measles, HIV
(i)
(4) Why does testing for HCG in a woman’s urine or blood
work as an early test of pregnancy?
b) human development divided into three trimesters
i)
3 months each
ii) read this section, it is very descriptive in nature
c) childbirth is hormonally induced and occurs in three stages
i)
labor
(1) strong, rhythmic contractions of uterus
ii) last weeks of pregnancy (Fig. 27.18A)
(1) high levels of estrogen from ovaries
(a)triggers expression of oxytocin receptors on uterus
(b) fetal cells produce oxytocin
(c)moms pituitary secretes oxytocin late in pregnancy
(d) oxytocin
(i) causes muscles of uterine wall to contract
(ii) stimulates placenta to make prostaglandins
1. make uterine muscles contract even more
(2) uterine contractions
(a)stimulate more oxytocin and prostaglandins to be
produced (positive feedback)
iii) three stages of labor
(1) dilation of cervix
(a)from onset of labor to 10cm dilation
(b) longest stage – 6 to 12 hours or much more
(c)no pushing, just wait
(2) expulsion (delivery of infant)
(a)20 minutes to an hour
(b) intense uterine contraction that last 1 min every 2-3
minutes
(c)urge to push
(3) delivery of placenta
(a)15 minutes after birth
iv) dereases in progesterone after birth leads to increase in
prolactin
(1) prolactin + oxytocin allow milk productin 2-3 days
after birth
d) reproductive technology
i)
hormone therapy
(1) increase sperm or egg production
ii) assisted reproductive technology (ART)
(1) surgically remove eggs
(2) fertilize secondary oocytes outside body
(3) return to uterus
(4) in vitro fertilization (IVF)
(a) most common ART procedure
(5) surrogate motherhood
(a)if woman can’t carry fetus use another woman