Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
25 Cards in this Set
- Front
- Back
Fertilization general
|
-fusion of sperm and ovum to initiate the development of new individual
-preceeded by: 1.ovulation: release of primary or secondary oocytes from the surface of the ovary 2. insemination: deposition of sperm into the female genital tract during coitus or artificial insemination |
|
Hormones of ovulation
|
- FSH promotes growth
-LH (leutenizing hormone) promotes ovulation - produced by adenohypophysis |
|
Corpus luteum
|
-ruptured follicles are converted into the corpus luteum under hormonal influence
- corpus luteum is an important endocrine structure that secretes progesterone which induces uterine changes facilitating the implantation and maintenence of the conceptus |
|
Induced ovulation
|
Cat and rabbit ovulate when stimulated by coitus
-eg cat's barbed penis - other mammals sponaneously ovulate |
|
polytocous/ monotocous
|
-bitch, cow, sow, cat and small ruminants are polytocous, meaning more than one oocyte is set free (usually from separate follicles)
-monotocous animals only set one oocyte free during each ovulation period |
|
Travel of egg during ovulation
|
- ovulated egg received at the fimbriated end (abdominal ostium) of the oviduct through a constant stream of peritoneal fluid which enters the uterine tube
- it is then transported towards the uterus through ciliary action and muscular contraction of the uterine tube |
|
insemination
|
-millions of spermatozoa are deposited into the vagina
- transport of the sperm is achieved not through their motility, but muscular contraction of the cervix and uterus |
|
sperm/ovum viability
|
-most species: sperm remains viable within the female genital tract for 1-2 days
-sperm of horse and dogs may be viable for up to 6-7 days - sperm host glands are in the avian vagina so sperm viability is 32 days for fowl and 70 days for turkey - ovum viability is generally 24 hours |
|
site for fertilization
|
-normally occurs in the ampullary region of the uterine tube, 12-24 hours after ovulation
- infundibulum of the uterine tube in dogs -spermatazoa must undergo process of capicitation and acrosomal reaction and are therefore unable to fertilize the oocyte upon arrival in vagina |
|
capacitation of sperm
|
-removal of glycoprotein coat and seminal plasma protein from the plasma membranes that overlie the acrosomal region of the spermatozoa
|
|
acrosomal reaction of sperm
|
-following capacitation, enzymes such as hyaluronidase and trypsin like substance are released in the acrosome
- these enzymes facilitate the penetration of the oocyte barrier, including the corona radiata, zona pellucida, and the oocyte cell membrane |
|
results of sperm penetration
|
- the 2nd meiotic division of the oocytes if completed producing ovum and 2nd polar body
- fertilization membrane/ reaction develops which prevents further entry of sperm into oocyte (polyspermy), probably as a result of chemical changes in the zona pellucida (zona reaction) -nuclei of the female and male germ cells now swell are are termed male and female pronuclei - the pronuclei fuse together reconstructing the diploid chromosomal number and creating a zygote |
|
result of fertilization
|
-prior to fusion, the pronuclei duplicate their DNA content
- immediately on fusion chromosomes split in the course of a normal mitotic division, resulting in the formation of a 2 cell zygote -restoration of the diploid -determination of sex, XX female (reverse in birds) -initiation of clevage |
|
twinning
|
1. monozygous: one ovum is fertilized but subsequently divides at the blastocyst stage into two genetically identical masses with the same sex and blood group
2. dizygous: two separate ova are fertilized |
|
ectopic implantation
|
-fertilized ovum may be lost in the peritoneal cavity and become implanted into a peritoneal surface
- early embryonic death usually follows |
|
freemartin
|
-in dizygous twinning cattle the development of a common circulation by placental anastomis usually occurs
- if opposite sex, development of female's reproductive tract is retarded under the influence of testosterone of the male - females are then infertile |
|
polyspermy
|
-occasionally more than one sperm may penetrate the female germ cell
- common in pigs - majority of these conceptuses die at a very early stage of development |
|
superfecundation
|
-impregnation by successive acts of coitus
- two or more ovum liberated at approximately the same time -fertilization by two or more males -cats, dogs |
|
superfetation
|
-when pregnant female ovulates, conceive and produce a second younger fetus
-pigs |
|
mare gestation period
|
335-345 days
|
|
cow gestation
|
279-282 days
|
|
ewe gestation
|
148-150 days
|
|
sow gestation
|
114-120 days
|
|
dog gestation
|
60-65 days
|
|
cat (queen) gestation
|
60 days
|