Reproductive System Flashcards
what 6 parts is the human male reproductive tract formed from?
testis epididymis ductus defrens accessory glands urethra penis
what is the male gonad?
testis
what are the testis the source of?
male androgen hormone (testosterone) and gametes
what makes up the external genitalia?
penis and scrotum
what is the epididymis continuous with?
ductus defrens
where do the testis develop?
in the abdomen at the level of the kidneys
what happens to the testes at birth/just prior?
migrate through hole in the abdominal wall (inguinal canal) to the scrotum
what is descent of the testes guided by?
gubernaculum
what does the testis bring with it as it descends?
‘lifeline’ spermatic cord - including blood vessels, nerves and sperm transport duct
also brings fascia from the abdomen which covers it within the scrotal sac
what happens within the epididymis?
sperm maturation, transport and storage
where is the sperm manufactured?
semiphorous tubules within lobules of the testis
what happens during travel through epididymis?
fluid is reabsorbed
what part of the epididymis is sperm stored in?
tail
how many days does it take for sperm to travel through the epididymis?
12-16 days
what does the acrosome of sperm contain?
enzymes to penetrate oocyte
what is found on the midpiece of sperm?
mitochondria to produce the ATP required to power flagella movements
what is the ductus defrens continuous with?
tail of epididymis
what are the walls of the human ductus defrens formed of?
thick smooth muscle
what is the role of smooth muscle in the ductus defrens?
contracts to propel sperm movement
how does the ductus defrens exit the abdomen?
passes through inguinal canal
where is sperm emptied into at ejaculation?
urethra
what is involved in a vasectomy?
cutting or tying off ductus defrens
where is the urethra located?
from base of bladder to external urethral opening
how long is the male urethra?
~20cm
what is the urethra lined with?
uroepithelium
what are the 3 segments of the urethra?
prostatic, membranous, and spongy/penile
where is the attachment for external genitalia found?
perineal membrane
what is the role of accessory sex glands?
make the seminal fluid
where are the ampulla found?
dilated distal ends of the ductus defrens
what is produced by the ampulla in human males?
minor amount of seminal fluid
how much of the seminal fluid is produced by seminal vesicles in men?
60%
what is found in the secretions of the seminal vesicles?
nutrients for sperm (fructose)
fibrinogen
enzymes
what is the role of fibrinogen in semen?
maintains life of sperm and facilitates swimming
what do the seminal vesicles join with?
ductus defrens
what is the name of the duct formed when the seminal vesicles and ductus defrens join?
ejaculatory duct
how much of the seminal fluid is produced by the prostate in men?
40%
what is contained in seminal fluid produced by the prostate?
buffers to counteract acidic urethra and vagina
clotting factors which act on fibrinogen and led to coagulation
what is the consistency of the seminal fluid produced by the prostate?
thin/milky
where do ejaculatory ducts open?
seminal colliculus
where is the seminal colliculus?
raised area on prostatic urethra
what do bulbourethral glands produce?
small amounts of clear, pre-ejaculatory fluid
where do bulbourethral glands empty into?
penile/spongy urethra at the level of the perineal membrane
what is the role of pre-ejaculatory fluid?
flushes urethra
where is the root of the penis attached?
at perineal membrane by two crura which sit between the rami of the pelvis
what is the main part of the penis called?
the body/shaft
what is the tip of the penis called?
glans
what does the glans contain?
external urethral oriface
what is the erectile tissue formed from?
2 corpora cavernosa and 1 corpus spongiosum
what are corpus cavernosa?
paired cavernous bodies that form the main erectile bodies of the shaft
what are the corpus cavernosa attached to?
the perineal membrane via crura
where is the corpus spongiosum located?
surrounding the urethra, forms the bulb proximally and glans of the penis
what is the purpose of the corpus spongiosum?
allows passage of products through the urethra
what artery supplies the penis?
internal pudendal (larger in males)
what is the internal pudendal artery a branch of?
internal illiac
how does orientation of the testis vary in domestic species?
may be vertical or horizontally aligned
some are located near the perineum (cats)
how do testis differ between the bull and stallion?
bull -vertical arrangement of epididymis and testis
stallion - horizontal arrangement of epididymis and testis
describe snake testicles
internal and elongated
how do accessory sex glands vary between species?
presence and size varies
what are seminal vesicles known as in domestic species?
vesicular glands
which species has large bulbourethral glands?
the pig
where does most seminal secretion occur from in dogs?
prostate gland
what are the 2 main types of penis?
musculocavernous
fibroelastic
describe a musculocavernous penis
flaccid when not in use and covered by prepuce. becomes engorged with blood to produce erection
give 3 examples of species with a musculocavernous penis
cat
horse
man
what is specialised about the dogs penis?
has os penis formed from ossification of the corpora cavernosa
large bulbus glands enable locking during mating
describe a fibroelastic penis
few cavernous spaces
more solid structure that elongates during erection
retractor penis muscle relaxes to allow sigmoid flexure to straighten
does the shape of the penis vary between species?
yes
what is the role of the urethral process on a rams penis?
can pass through the cervix
how long is the human ovary?
4cm
what is the ovary the site of?
egg maturation (oogenesis)
what does the ovary produce that has effect on the body?
hormones
what happens to ovaries after the menopause?
reduce in size, become shrunken.
what ligament are ovaries attached by?
ovarian ligament
what is the role of the suspensory ligament of the uterus?
brings blood vessels to the ovary
what 2 parts is the uterus formed of?
body and cervix
what hormones are produced by the ovaries?
oestrogen
progesterone
testostorone
what is the name of the fibrous outer coat of the ovary?
Tunica albuginea
what is found in the outer cortex of human ovaries?
follicles
what is in the inner medulla of the ovary?
vascular supply and nerves
what does egg maturation involve?
follicogenesis and oogenesis
when is egg release from the ovary timed for?
when the uterine wall is most primed for implantation
what is the uterine tube?
aka oviduct/fallopian tube
from ovary to uterus
what is the infundibulum in mammals?
finger-like fimbriae that collect ova. Become engorged and cover surface of ovary during ovulation
how is the egg moved through the fallopian tube?
by cilia and peristaltic movements of fluid
what is the ampulla of the fallopian tube?
wider part of the tube
what occurs in the ampulla?
fertilisation
what is the isthmus of the fallopian tube?
narrow part of the fallopian tube
how long is the human uterus?
~10cm
what occurs in the body of the uterus?
implantation
what happens to the lining of the body of the uterus id there is no implantation of an egg?
lining is shed (menses)
what is the external os?
opening into the cervix
how does the cervix appear on a woman who has not had a vaginal delivery?
normal nulliparous - small hole
how does the cervix appear on a woman who has had a vaginal delivery?
normal parous - slit
what is the endometrium?
lining of the uterus which is shed during menses
what causes change in endometrium thickness?
cyclic hormones cause thickening to prepare for implantation and a reduction in progesterone leads to shedding
what is the body of the uterus formed of?
thick smooth muscle
what is the cervix made of?
dense smooth muscle
what is the effect of progesterone on the mucous in the cervix?
thickens
what effect does oestrogen have on mucous at the cervix?
dilutes it to allow sperm to pass through
describe the normal uterus position in the human?
anteverted (folded over the bladder) and anteflexed (flexed at cervix)
what is the uterus held in position by?
round ligament
where does the round ligament attach?
runs from uterine tube and passes through inguinal canal and attaches to vulva
what are the anterior relations of the uterus and vagina
bladder and urethra
what are the posterior relations of the uterus and vagina?
rectum and lower GI tract
how long is the human vagina?
~10cm
what is the wall of the vagina formed of?
distensible smooth muscle
what is the vagina lined with?
stratified squamous non-keratinised epithelium
what do glands in the vagina secrete?
lubricant
what is the role of the vagina?
copulation, passage of menses and birth canal
what forms the vestibule in humans?
area between the labia where openings of the vagina and urethra are
what is the perineum?
surface area and all it’s contents between inner thighs
what is the clitoris the homologue of ?
the glans
what type of tissue is the clitoris formed of?
erectile tissue
what is the broad ligament?
perineal fold over uterine tube and anterior and posterior surface of uterus
what does the broad ligament carry?
blood vessels and nerves
what are the 3 parts of the broad ligament?
mesovarium
mesosalpinx
mesometrium
where is the mesovarium found?
around ovary
where is the mesosalpinx found?
around uterine tube
where is the mesometrium found?
around the uterus
in the human where do ovaries sit on the broad ligament?
posterior
what is the role of the broad ligament?
support uterus and ovaries
what is the fundus of the uterus?
area above where uterine tubes enter
what artery supplies the ovaries?
ovarian artery
what is the ovarian artery a branch of?
Aorta
what is the ovarian ligament supported by?
suspensory ligament of ovary
what are the uterine and vaginal arteries a branch of?
internal illiac
how are the blood supplies of ovaries, uterus and vagina linked?
form anastomoses with each other to provide a wide supply to the tissues
how does release of female gametes differ from male?
female are released discontinuously in cycles
what do oocytes mature within?
follicles
where are follicles found in most domestic species ovaries?
cortex
what does follicles in the cortex mean for the appearance of the ovary?
follicles are visible and palpable externally
what happens to follicles when mature in ovaries where they are found in the cortex?
burst on external surface
where are horses follicles found?
medulla
what does the position of horses follicles in the medulla mean for the outwards appearance of the ovary?
smooth externally
where do follicles erupt in horses?
in ovarian/ovulatory fossa
where is the ovarian/ovulatory fossa found?
depression on the medial boarder of ovary
in what species is only one ovary found?
birds and some reptiles
in hens, what is the entire tract (from infundibulum to cloaca) called?
the oviduct
what are the parts of the uterine tube found in egg laying reptiles and birds?
Infundibulum - collects yolk Magnum - produces albumin Isthmus - shell membranes produced Uterus - shell forms vagina
where does fertilization occur in egg laying reptiles/birds?
Infundibulum
what is the uterus known as in egg laying reptiles/birds?
shell gland
what feature of the vagina in egg laying reptiles and birds aids egg laying?
very muscular
describe a simplex uterus
1 cervix
large uterine body
no horns
how many cervix are found in a simplex and bicornuate uterus?
1
in what species is a simplex uterus found?
humans, apes, bats
describe a bicornuate uterus
1 cervix, small uterine body, long uterine horns
what is the role of long uterine horns in bicornuate uteri
enables attachment of large litters along horns
in what species is a duplex uterus found?
rats, mice rabbits
in what species is a bicornuate uterus found?
dog, pig, horse, sheep
describe a duplex uterus
2 cervices, separate horns, no uterine body (no fusion of paramesonephric duct)
what is the vestibule in domestic species?
vagina and urethra join in common opening
what marks the change from vagina to vestibule in domestic species?
presence of external urethral opening within the body
what is the cloaca?
common opening for excretion defaecation and copulation
do birds have external genitalia?
no
what occurs in the seminephorus tubules?
spermatogenesis
what makes up excurrent ducts?
rete testis
efferent ductules
epididymis
what is the role of the epididymis?
maturation of sperm
what are the pampiniform plexus in the testis?
veins which drain blood away from the testis
what are the 3 main cells found in the seminiferous tubule?
leydig cells
sertoli cells
germ cells
where are leydig cells found?
surrounding connective tissue
what is the role of leydig cells?
make testosterone
what does testosterone work with to maximise sperm production?
FSH
what type of hormone is testosterone?
steroid
where are sertoli cells found?
in seminephorus tubule
what is the role of sertoli cells?
support developing sperm cells (form syncitium)
where are germ cells least mature?
periphery
where are germ cells most mature?
near lumen
what allows continuous production of sperm?
always at different stages of development (spermatogenesis) in the testis
where are efferent ductules found?
head of epididymis
how does the head of the epididymis appear histologically?
saw toothed lumen
what epithelium is the head of the epididymis formed of?
pseudostratified epithelium with ciliated cells and non ciliated tall columnar cells
what is the role of non ciliated tall columnar cells?
fluid absorption
what must happen to sperm in order to reach maturity
must pass through duct of epididymis and be covered in maturation factors
how does the tail of the epididymis appear histologically?
smooth, uniform lumen with thick epithelium
what epithelium is the tail of the epididymis formed of?
pseudostratified epithelium cells with stereocilia to increase surface area for absorption and secretion of maturation factors
what is follicogenesis?
follicle maturation including egg
when are all primordial follicles formed?
before birth
what is a woman’s egg reserve?
total number of primordial follicles
why may more than one oocyte be released per month?
if a species is polyovulatory
when is oocyte meiosis completed?
only at fertilisation as oocyte in primordial follicles remains in arrested meiosis
what is the zona pelicunda?
where the sperm bind preventing polyspermi
how does oestrogen reach the blood stream?
builds up in antrum of secondary follicle, is released into the blood after ovulation
what is the wall of the uterine tube formed of?
outer longitudinal and inner circular muscles
what is the lining of the uterine tube?
ciliated columnar epithelium
how is the ova transported along the tube into the uterus?
peristalsis and cilia
what is the role of secretions in the uterine tube?
nourish fertilised egg and allow egg to start first divisions
how does the human uterine tube appear histologically?
highly folded
what are the 3 layers of the human uterus?
perimetrium, myometrium, endometrium
where is the perimetrium located?
outermost layer of the uterus
what is the perimetrium formed of?
layer of peritoneum
what is the myometrium formed of?
3 layers of smooth muscle
what layer of the uterus is the myometrium?
middle
what is the endometrium formed of?
vascular and glandular tissue
what is the endometrium thickness regulated by?
hormones of menstrual cycle
what layer of the uterus is the endometrium?
innermost
describe the cascade of sexual differentiation
genetic sex leads to gonadal sex and so hormonal sex. Hormonal sex leads to duct and genital sex, and brain sex. Brain sex is then divided into neuroendocrine sex and behavioral sex
when is the indifferent phase of sexual differentiation?
week 1-7
when is genotypic sex determined?
when the gametes unite at conception
the early embryonic gonad is ….?
bipotential
what is sex determined by?
the presence of a single transcription factor
what transcription factor determines sex?
SRY protein
where is the SRY protein encoded?
encoded on the sex determining region of Y chromosome
what is the sex determining region on the Y chromosome also known as?
Testis determining factor
where do gonads develop?
on the genital/gonadal ridges
what is week 5 of the embryo’s development the beginning of?
differentiation period
what happens during initial gonadal development?
primordial germ cells migrate from the yolk sac to genital ridge to become oocytes/spermatazoa
what are the 2 ducts found in gonadal sex development?
mesonephric and paramesonephric duct
what effect does testosterone have on mesenephric and paramesonephric ducts?
amplifies mesonephric duct
what does the mesonephric duct go on to form in the male?
ductus defrens
what effect does antimullerian hormone have on mesenephric and paramesonephric ducts?
regresses paramesonephric duct
how do the mesenephric and paramesonephric ducts respond differently in the female gonad with female hormones?
lack of testosterone degenerates mesonephric duct
lack of antimullerian hormone prevents regression of paramesonephric duct
what does the paramesonephric duct go on to form in the female?
uterus, fallopian tubes and upper 1/3 of vagina
what is the indifferent duct stage?
in foetus weeks 6-8 both sets of ducts are present
what promotes the development of sex specific ducts?
presence or absence of testicular hormones
what is the effect of testosterone on duct sex?
stimulate mesonephric ducts to form epididymis, ductus defrens and seminal vesicles
why do paramesonephric ducts develop?
because of an absence of AMH and form upper vagina, uterus and oviducts
what does the genital tubercle go on to form in the male and female?
male: prepuce
female: clitoris
what does the genital fold go on to form in the male and female?
male: urethral groove
female: labia minora
what does the genital swelling go on to form in the male and female?
male: scrotum
female: labia majora
what is the effect of AMH in the testis?
regression of paramesonephric ducts
what is the effect of testosterone in the testis?
growth of seminal vesicles and ductus defrens
what is the effect of DHT in the testis during development?
fusion of labial scrotal folds and growth of phallus and prostate
what is the effect of lack of AMH in the ovary?
differentiation and growth of fallopian tubes, uterus and upper 1/3 of vagina
what is the effect of lack of testosterone in the ovary?
regression of mesonephric ducts
what hormone are all foetuses exposed to in the placenta?
oestrogen
how do hormones influence development of sex-specific behavior and sex preferences?
via differentially inducing expression of hormone receptors in the brain
what does the growth of the foetus displace?
abdominal organs
what is the effect of progesterone on digestion?
relaxes smooth muscle which can slow digestion
what is a big danger during pregnancy in horses?
the colon can become twisted and cause colic
what does torsion/twisting of the equine colon over 90 degrees lead to?
veins are cut off so there is limited drainage of metabolites and toxins
what does torsion/twisting of the equine colon over 270 degrees lead to?
ischemia and rupture of the uterine artery
what causes varicose veins and oedema in pregnancy?
venous return is restricted
what is another cause of oedema in pregnancy?
increase in cortisol and aldosterone which cause water retention in the kidney
what can oedema be a sign of?
pre-eclampsia
what can an increase in melanin production lead to?
melasma due to increased pigmentation of the skin
darkening of freckles and moles
linea nigra appears in place of linea alba
what is an increase in melanin production due to?
response to pregnancy hormones
what hormone is released in the latter half of pregnancy?
relaxin
what is the role of relaxin?
loosens joints and ligaments which creates more space for the birth canal
what can relaxin cause?
pelvic symphysis disorder
what is the effect of relaxin and oestrogen on the cervix in late pregnancy?
soften the cervix by breaking down dense collagenous tissue and making the cervix distensible
what do mammary glands produce?
colostrum and then milk
what are mammary glands formed of?
modified and enlarged sweat glands
what are mammary glands lined with?
cuboidal epithelial cells
what are mammary glands surrounded by?
myoepithelial cells
what happens to ducts in the first half of pregnancy?
rapid proliferation
what happens to ducts in the first half of pregnancy?
alveoli (groups of ducts) enlarge and begin secretion
what type of glands are mammary glands?
apocrine glands
where are mammary glands positioned?
between skin and muscle
what is the role of areolar glands?
lubrication and protection of nipple
what can happen to areolar pigmentation during pregnancy?
increases
what is a species number of mammary glands dependent on?
number of offspring per litter
what is the lactiferous sinus?
large cavity that drains into the nipple
where do lactiferous ducts open?
in pore on the nipple surface
what is a lactiferous duct supplied by?
15-20 lobes
what are lobes of the mammary glands surrounded by?
interlobar connective and adipose tissues
describe the structure of mammary glands in cows
lactiferous duct drains into gland sinus. This drains into the teat sinus and then out of the teat canal
what happens to lumen size at each sinus of the cow mammary glands?
thinning of lumen size caused by smooth muscle
what effect does suckling have on filling of teat sinus?
causes milk let down, leads to filling of the teat sinus and exit of milk
what is the difference between menstrual and oestrus cycles?
lack of menstruation in oestrus cycles
what happens to the endometrium during oestrus cycles?
is reabsorbed
what happens to the endometrium during menstrual cycles?
is shed
what days of the menstrual cycle does the follicular phase take place?
day 6-13
what is secreted by the pituitary gland at the start of the follicular phase?
follicle stimulating hormone (FSH)
what does FSH stimulate during the follicular phase?
stimulates ovaries to develop follicles where one will become dominant
what hormone will the growing follicles produce?
oestrogen
what does oestrogen stimulate during the follicular phase?
the lining of the uterus to thicken by encouraging vasoconstriction and formation of new blood vessels
also thins cervical mucous and so increases fertility
what happens around day 14?
ovulation
what do increased oestrogen levels lead to happen around day 14?
pituitary gland releases luteinising hormone (LH) leading to LH surge
how long will the egg survive post ovulation?
~24 hours
how long can sperm survive in the uterus?
3-5 days
when is the most fertile period?
before and around ovulation
what days does the luteal phase occur?
15-28
what does the follicle become after ovulation?
corpus luteum
what hormone does the corpus luteum produce?
progesterone and a small amount of oestrogen
what happens to the corpus luteum after 14 days if there is not a pregnancy?
degrades
what is the effect of progesterone on the uterus?
maximises thickness of uterine lining and glands become secretory
cervical mucous thickens to form a barrier
what day does menses occur?
1-5
what hormone levels drop during menses?
oestrogen and progesterone
what happens to the uterine lining during menses?
is shed
what hormone is secreted by the implanted embryo if fertilisation occurs?
human Chorionic Gonadotropin (hCG)
what is the effect of hCG?
maintains the corpus luteum and so oestrogen and progesterone are still produced until the placenta is established
uterus lining is maintained
what is measured in pregnancy tests?
hCG levels
what do high levels of progesterone in pregnancy prevent?
further ovulation
what is the oestrus cycle?
period of sexual activity
define seasonally monoestrus
only 1 period of sexual activity during a season at a particular time of year e.g. fox
define dioestrus
go into oestrus twice a year (e.g.dog)
define polyoestrus
can go through a succession of oestrus cycles during a particular time of the year (e.g cat, cow)
define seasonal polyoestrus
can go through a success of oestrus cycles during a particular time of the year (e.g. horse, sheep). ensures offspring arrive at a prosperous time of year
what sort of ovulators are most species?
spontaneous
what are induced ovulators?
species which require mating to stimulate ovulation (e.g. cats)
what organs are bypassed in the foetus?
liver and lungs
why are the liver and lungs bypassed in the foetus?
as they are not used until after birth
what is oxygen and nutrient rich blood supplied to the foetus by?
placenta through the umbilical vein
what happens soon after birth when the first breath is taken?
pulmonary vessels increase in size and pulmonary circulation takes over
what remains in the adult of foetal structures?
remnants
what does fetal circulation consist of?
umbilical blood vessels and 3 shunts
what are the 2 umbilical blood vessels?
umbilical vein and artery
what are the 3 shunts of the fetal circulation?
ductus venosus
foramen ovale
ductus arteriosus
what is a shunt?
vessel which diverts blood
what is the role of the umbilical vein?
carries oxygenated blood from placenta to liver
what does the umbilical vein become after birth?
teres ligament covered by the falciform ligament
what happens to the umbilical vein in the calf?
retains patency and is open until a few months after birth
what is the role of the ductus venosus?
allows the majority of oxygenated blood to bypass liver
what does the ductus venosus connect?
umbilical vein to caudal vena cava
what does the ductus venosus become after birth?
ligamentum venosum
what is the role of the foramen ovale?
a hole in the interatrial septum which allows oxygenated blood to pass from the right to left atrium
what is happens to the foramen ovale after birth?
valve closes to leave fossa ovalis
what is the role of the ductus arteriosus?
allows deoxygenated blood to bypass the lungs
what does the ductus arteriosus connect?
pulmonary trunk to the aorta
what does the ductus arteriosus become after birth?
ligamentum arteriosum
what is the role of umbilical arteries?
carry deoxygenated blood from the aorta to the placenta
what happens to the umbilical arteries after birth?
proximal ends remain open and help supply the bladder with blood
distal ends close
in mammals where does the egg develop?
within the female body
what does the placenta allow to take place?
physiological exchange (e.g. nutrients, gases and excretory products)
what does the placenta produce?
hormones which establish and support pregnancy
where should the placenta develop?
posterior boarder of uterus
what to the fetal membranes create?
placenta
what do the membranes and placenta do?
protect embryo/fetus during pregnancy and provide for nutrition, respiration and excretion
what are the names of the 4 fetal membranes?
amnion
chorion
allantois
yolk sac
what are all 4 fetal membranes formed by?
zygote
what does the placenta form from?
fetal chorion and maternal endometrium
what is the decidua?
area of endometrium where blastocyst implants and placenta is formed
atbirth what is expelled as afterbirth?
umbilical cord, amnion, placenta and chorion
define fetal membrane
any tissue or structure developed from fertilized ovum which does not form part of the embryo itself.
what does the embryoblast form?
the embryo
what does the trophoblast form?
part of the placenta
what are the inner and outer cell masses of the blastocyst?
inner - embryoblast
outer - trophoblast
what 2 layers does the trophoblast differentiate into?
cytotrophoblast
syncytiotrophoblast
what is the name of the outer layer of the trophoblast?
syncytiotrophoblast
what is invaded by the syncytiotrophoblast?
maternal endometrium
describe the formation of the human placenta
lacunae form in the syncytiotrophoblast, the cells of the syncytiotrophoblast erode the walls of maternal capillaries and so maternal blood enters the lacunae.
how is a large exchange surface created in the placenta?
projections of trophoblast cells (villi) grow into the maternal tissue
do maternal and foetal circulation ever combine?
no - are in close apposition but never mix
why is it essential that maternal and fetal blood never meet?
fetus would be detected as foreign and initiate immune response
fetal antibodies are fatal to the mother
when is the chorionic cavity formed?
as the embryo implants
what is the chorionic plate?
extraembryonic mesoderm lining the inside of the trophoblast
where do blood vessels develop to form the umbilical cord?
the connecting stalk
chorionic plate
what is the placenta a fusion of?
tissues not blood!
what cavity surrounds the fetus?
amniotic
where is the placenta positioned in placenta previa?
over or close to the cervix
what happens to the fetal membranes as the fetus develops
amniotic cavity increases in size
chorionic cavity decreases in size and amnion and chorionic plate fuse
what happens in the domestic species formation of the placenta?
some of the yolk sac is taken into the embryo to form gut tube. external part forms a provisional placenta
what is the name of the provisional placenta in domestic species?
choriovitelline
where does the embryo remain in domestic species?
the centre of the uterus rather than being embedded in uterine wall like humans
what surrounds the embryo of domestic species?
amnion which is filled with fluid
how is the yolk sac attached to the embryo?
at umbilicus
what is the outermost embryonic tissue of domestic species?
chorion
what is the chorion associated with in domestic species?
endometrium of uterus
what is the role of chorionic villi?
project into endometrium to bring fetal blood close to maternal blood
what does the overgrowth of hindgut form in domestic species?
allantoic cavity
what forms the definitive placenta in domestic species?
allantoic cavity and chorion
what is the name of the definitive placenta in domestic species?
chorioallantoic
what does the chorioallantoic placenta become vascularised with?
umbilical vessels
in the pig does the allantois (and vasculature) extend to tips of chorion
no - there is no anastomosis between embryos so each one has their own blood supply
in the cow does the allantois (and vasculature) extend to tips of chorion?
yes - there is anastomosis between embryos which allows for freemartinism (influence of androgens of male embryo on female development)
what is the placenta arrangement like in a horse?
allantois totally surrounds the amnion so only chorioallantoic connections exist
how can species with only chorioallantoic connections be born?
totally enclosed in amnion which must be removed to avoid suffocation
why doesn’t amnion rupture in species with only chorioallantoic connections in the placenta?
amnion does not need to rupture as not attached to chorion
what is the placenta arrangement like in ruminants and pigs?
amnion is in connection with the chorion
how can species with amnion is in connection with the chorion be born?
not totally enclosed in the amnion
why does the amnion rupture in species with amnion in connection with the chorion in the placenta?
needs to as it is attached to chorion
what happens in polytoccus animals (e.g. pigs)?
each fetus must rupture its amniotic membrane during birth as allantois is separate and there is no anastomosis
what are the 3 main types of contraceptive used in humans?
hormonal
barrier method
intrauterine devices
what types of hormonal contraception are there?
pill
patch
injection
hormonal IUD
what is the role of hormonal contraceptives?
prevent ovulation
thicken cervical mucus
thin endometrial lining
how do hormonal contraceptives prevent ovulation?
high level of progesterone (and oestrogen) prevent the release of GnRH, FSH and LH from the pituitary gland
what are the main barrier methods of contraception?
diaphragm/cap
male condom (most effective with spermicides)
female condom
spermicides
what are the two types of intrauterine device?
copper
hormonal
how do copper IUDs prevent pregnancy?
inhibit sperm motility and prevent them from traveling through the cervical mucus. Presence inhibits implantation of embryo
how do hormonal IUDs prevent pregnancy?
thickens cervical mucus and thins endometrial lining. Presence inhibits implantation of embryo
how can IUDs be used in cattle?
synchronising breeding cycles of the herd
how does progesterone IUD synchronise pregnancy in cattle?
imitates corpus luteum by releasing progesterone which suppresses the release of GnRH and therefore FSH and LH. Once IUD is removed levels of these hormones increase stimulating ovulation 2-3 days later in all cows
what happens during vasectomy?
small section of ductus defrens is removed
what effect does vasectomy have on sexual behavior?
maintained just unsuccessful
what animals is vasectomy commonly used in?
humans, zoo animals, ferrets and rams
why is vasectomy difficult to reverse?
any interaction of sperm with blood will result in an autoimmune response and destruction of sperm leading to infertility
what happens during castration?
testis are removed bilaterally
what is decreased through castration?
sexual behaviors and aggression due to removal of androgen source
prostate cancer risk
when can lambs and piglets be castrated?
in the first few days after birth
how can lambs and pigs be castrated?
blocking off blood supply to testis
what is the benefit of early castration of lambs and pigs?
males and females can be kept together for longer
production of testosterone can alter taste of meat
alters behavior and makes flock/herd easier to manage
what happens during ovohysterectomy?
ovaries and uterus are removed
what are the benefits of ovohysterectomy?
eliminates signs of oestrus
decreases risk of ovarian cysts and mammary tumors
when should ovohysterectomy be performed ideally to have full benefits?
before 1st season will prevent mammary tumors
what is complex about ovohysterectomy?
ovarian, uterine and vaginal arteries must be tied off carefully to prevent internal bleeding
what happens during intra uterine insemination?
sperm is concentrated and placed in to catheter. Catheter passed into uterus and sperm injected just after ovulation (natural cycle or induced)
what is AI used for?
creation of a more effective ejaculate due to concentration of sperm
timing can maximise chance of pregnancy
used to improve breeding success and reduce injuries in animals
wide range of semen (think equine breeding)
