Reproduction Flashcards
reproduction
propagation and continuation of the species
parturition
birth
puberty
reproductive maturation
- physical - reproductive organs
- endocrine - endocrine cycle develops
heat/ estrus
period of sexual receptivity
estrous cycle
interval from one heat to the next heat
ovulation
release of oocyte from ovary
spermiation
release of spermatozoa into male duct system
copulation
transfer of sperm from male to female
fertilization
union of the male (sperm) and female (oocyte) gametes
pregnancy/ gestation
development of the zygote/ embryo/ growth of fetus
lactation
nourishment of neonate
ovaries
female gonad (sex organ) structure which contains all the follicles from which oocytes are released
infundibulum
catches egg when it is released from the ovary
oviduct
fallopian tube
tube for egg transportation to the uterus
site of fertilization
uterus
the place where the fetus(s) develops
provides nutrients prior to development of the placenta
contracts during parturition to expel the fetus
cervix
fibrous connective tissue
barrier to external environment
acts as a passageway and filter for sperm
dilates at parturition
vagina
copulatory organ
passageway btwn cervix and external genetalia (vulva)
passageway for the fetus
vulva
external genetalia
includes labia which help protect vagina from bacterial contamination
ovarian cycle
primary follicle
secondary follicle
tertiary (antral) follicle
corpus luteum
primary (primordial) follicle
immature oocyte surrounded by a single layer of granulosa cells
secondary (growing) follicle
recruited from primordial pool
2 or more layers of granulosa cells
tertiary (mature) or antral follicle
antrum is visible
corpus luteum
develops from follicle after ovulation
-yellow mass of cells that fills the ruptured follicle
granulosa and theca cells become luteal cells
produces progesterone - necessary for the maintenance of pregnancy
in most species CL degenerates @ end of cycle unless gets signal from uterus that embryo is present
oogenesis
egg production
production of primary oocytes occurs before birth
females complement of oocytes is fixed soon after birth
100,000s of primordial follicles each containing an oocyte
only a relative few will be ovulated - most partially develop and become atretic
zona pellucida
protein coat “shell” that surrounds the oocyte
follicle
blister like structure on the ovary
contains an oocyte
contains granulosa cells that produce estrogen
corpus albicans
“scar” left on ovary after CL regresses
ovarian cycle of a uniparous species
usually produce 1 mature ovum per estrous cycle
ex. horse, cow, human
ovarian cycle of a multiparous species
(ie litters)
multiple ova produced per estrous cycle
ex. cat, dog, sow
estrous cycle
time from beginning of one heat period (estrus) to the next
stages: proestrus, estrus (high estrogen), metestrus, diestrus (high progesterone), anestrus (only some species)
proestrus
follicles begin developing and growing
output of estrogen from follicles increases accordingly
estrus
day 0 of cycle
period of sexual receptivity in the female
estrogen level production peaks
ovulation occurs near end of estrus
metestrus
corpus luteum developing
estrogen dropping rapidly
progesterone rising rapidly
diestrus
CL exerting maximum effect
the uterus preps for an embryo
if fertilized ovum implants, CL is retained
if no pregnancy, CL degenerates
anestrus
period of temporary ovarian inactivity
seen in animals that have seasonal cycles
also seen during periods of nutritional stress
estrous cycle intervals
polyestrous
seasonal polyestrous
diestrous
monoestrous
polyestrous
cycle continuously throughout the year if they are not pregnant (cattle, swine, human)
seasonally polyestrous
seasonal variations in estrous cycles (horse, sheep, cat)
diestrous
2 cycles/ year, usually spring and fall (dog)
monoestrus
one cycle per year (fox and mink)
endocrine regulation of female cycle
initiation by the hypothalamus in the brain
releases gonadotropin(GnRH)
responds to environment (some species; day length)
responds to body maturity (puberty)
often inhibited by nutritional stress
- early lactation, (also athletic training)
inhibited by progesterone (ie birth control)
gonadotropin releasing hormone
GnRH
stimulates anterior pituitary gland to produce gonadotropin hormones
- follicle stimulating hormone (FSH)
- leutinizing hormone (LH)
- they travel in blood to the gonads
follicle stimulating hormone
stimulates follicle development
hypothalimc - pituitary - ovarian axis
mature follicle –> estrogen –> GnRH –> LH –> ovulation
mature follicles produce lots of estrogen
estrogen level reaches high threshold
causes a surge in GnRH production
causes surge in LH release from pituitary
causes ovulation
ovulated follicle becomes CL producing high P4
high P4 low E2 = neg feedback
high E2 low P4 = positive feedback
-causes LH surge
prostaglandin (PGF2)
produced by non-pregnant uterus
causes lysis of CL
lysis of corpus luteum
if animal is not pregnant turns into corpus albicans loss of CL causes progesterone levels to decrease new follicles mature quickly ovulation occurs thus completing a cycle
pregnancy: maintenance of the corpus luteum
embryo moves to uterus for implantation
embryo makes placenta
-membranes which surround the fetus and help w/ nutrient exchange w/ mother
-may make progesterone and other hormones
signs of estrus - dairy
standing for mounting or chin pressing
reproductive physiology of the bitch
one estrus per breeding cycle (monoestrus) one breeding cycle every 6 to 8 months -not related to season anestrus - proestrus - estrus - diestrus corpus luteum for aprox 65 days (preg or not) -no maternal recognition of pregnancy estrus for approx 10 days ovulation (multiple) at approx day 7 -2 days after LH surge
reproductive physiology of the queen
polyestrus (3 week cycles)
-induced ovulator
-alternate proestrus - estrus - postestus until mating
no mating - no ovulation - no CL - no rise in progesterone
male reproductive system
produces testosterone
spermatozoa
delivers spermatozoa to the female system
testes
suspended in scrotum
cooler temperature required for sperm production
descend through inguinal canal into scrotum before birth
develop in abdominal cavity during fetal development
cryptochid
lack of testicular descent
sterile
still produce testosterone
pampiniform plexus
countercurrent heat exchanger (of scrotum/testes)
sperm pathway
seminferous tubules - continually produce sperm rete testis epididymis (head, body, and tail) vas deferens (ductus deferens) urethra
seminiferous tubules
between tubules:
-leydig cells - produce testosterone
w/in tubules
-sertoli cells - support development of spermatozoa
spermaition
release of spermatozoa into tubule spermatogonia --> proliferation spermatocyte --> meiosis spermatid --> final differentiation spermatozoa
sperm anatomy
head - contains nucleus of the cell, covered by acrosome
midpiece - large concentration of mitochondria
tail - contractile fibrils (flagella)
acrosome
covers sperm head
contains enzymes that help the spermatozoa penetrate the zone pelucida
semen
seminal plasma and spermatozoa
billions of spermatozoa/ mL of semen
seminal plasma
fluid produced by epididymis and accessory sex glands
provides nutrients and buffer
accessory reproductive glands
seminal vesicles - paired glands
prostate gland - single gland surrounds urethra
bulbourethra (coupers) gland - secrete mucinous fluid just before ejaculation that clears and lubricates the urethra
endocrine regulation in male
negative feedback loop
GnRH -+-> LH -+-> leydig cell –> testosterone - - -> GnRH
delivery of sperm to oocyte
sperm transported from vagina to oviduct by - swimming - contractions of uterus and oviducts -cilia in oviducts arrives in the oviduct in minutes
acrosome reaction
occurs when sperm binds to zona pellucid
release of acrosomal enzymes to help the sperm penetrate through the zona pellucida
fertilization
a single sperm penetrates the zone and fuses w/ the cell membrane of the ovum
this leads to the “zona block” which prevents any other sperm from getting through
this is due to the cortical reaction occurring in the oocyte
-blocks polyspermy
cortical reaction
“zona block”
occurs after fusion of sperm and oocyte membranes
contents of oocyte’s cortical granules are exocytosed into perivitine space and cause a hardening of the zona
polyspermy is thus prevented
zygote
a diploid cell resulting from the fusion of 2 haploid gametes; a fertilized ovum
morula
a solid ball of cells resulting from division of a fertilized ovum, from which a blastula is formed
blastocyst
a blastula (hollow ball of cells) in which some differentiation of cells has occurred
blastocoel
fluid filled cavity of a blastula
placenta
multilayered (3 layers), fluid filled, membranous sacs (2)
outermost layer of placenta (chorion) attaches to uterine lining
-fetal and maternal blood vessels are in close proximity to each other in this area
-site of exchange of blood and nutrients and waste
amnion
(placenta)
membranous layer immediately surrounding the fetus
-forms the amniotic sac
-fetus floats in amniotic fluid inside the amniotic sac
allantois
(placenta)
layer surrounding amniotic sac
-forms allantoic sac which accumulates wastes
-outside of allantoic sac is covered by the chorion
chorion
(placenta)
attaches to lining of uterus
linked to fetus by the umbilical cord
diffuse placental attachement
ex. horse or pig
cotyledonary placental attachement
ex. ruminant
zonary placental attachement
ex. dog, cat
discoid placental attachement
ex. primates, rodents, rabbits
eustocia
normal parturition
dystocia
prolonged or difficult parturition due to: excessive fetal size abnormal presentation multiple births
stages of parturition
stage I: initiation of uterine contractions and cirvical dilation
Stage II: expulsion of fetus
Stage III: expulsion of placenta
parturition initiated by the fetus
fetal maturation and stress
-responds w/ cortisol from fetal adrenal gland
fetal cortisol causes
-removal of maternal “progesterone block” on uterine contractions
-stimulation of cervical secretions
-effects on fetus: final lung maturation
stage I parturition
removal of progesterone block inc. uterine contractions
uterine contractions –> pressure on cervix –> release of oxytocin -> uterine contractions
usually 2 to 6 hours
dilation of cervix “fully effaced” - becomes flush w/ vagina
relaxation of pelvic ligaments
lubrication of birth canal
stage II parturition
expulsion of fetus
usually less than 1 hour
rupture of chorioallantoic and amniotic sacs
-lubrication
uterine labor wave contractions superimposed w/ abdominal muscle contractions
propulsion of fetus into vagina
neonate first breath
rupture of umbilicus and or detachment of placenta from uterus
hypoxia
massive stimulation of nervous system
expansion of lungs
stage III parturition
expulsion of fetal membranes
-litter bearing species have interspersed stage II and III
constriction of blood vessels @ maternal fetal union
oxytocin for continued uterine contractions and continued vasoconstriction
timing:
mare: 1-3 hrs, cow: 6-12hrs, sow 1-4hrs
reproductive technologies
artificial insemination
estrus synchronization
artificial insemination
approx 80% of dairy cows
bull ejaculate contains about 5mL w/ about 1 billion sperm per mL = 5 billion sperm/ ejaculate
typical AI does is 10 million sperm 500 doses
estrus synchronization
homronal injection protocol to control female cycle
often used in dairy management in conjunction w/ AI
simplest form is to give injections of PGF2 during diestrus
-causes regression of CL - allows rapid growth of follicles
-estrus and ovulation about 3 days later
no effect if CL not present (ie not in diestrus)
therefore give 2 injections about 14 days apart
timed artificial insemination
give GnRH to cause LH surge
-forces follicle to ovulate
not heat detection dependent
-pre arranged breeding schedule
embryo transfer
donor cow - given FSH to super ovulate and GnRH to time breeding
recipient cow - synched to donor cow’s cycle
blastocyst collected on day 7 by flushing donor uterus
transfer 1 egg to each recipient that is also on day 7 of cycle
day 7 blastocyst needs day 7 uterus
