General Embryology 2

What term describes the fusion of the sperm and ovum to initiate the development of a new individual?


What two events precede fertilization?

1. Ovulation
2. Insemination

What term is defined as the release of the primary or secondary oocyte from the surface of the ovary?


What term is defined as the deposition of sperms into the female genital tract?


What two hormones control ovulation? Where are they released from?

FSH (follicular stimulating hormone) and LH (luteinizing hormone) - both are released from the adenohypophyses (anterior pituitary gland)

What structure has important endocrine function with its secretion of progesterone?

Corpus Luteum

What hormone produces uterine changes that facilitate the implantation and maintenance of the conceptus?


What are the only two species that have non-spontaneous (induced) ovulation? What does this mean?

Rabbits and Cats - this means that coitus stimulates the release of the oocyte

What two domestic species are well known monotocous animals?

Horses and Cows (Heifers)

The ovulated egg is received at the _____ end (abdominal ostium) of the oviduct through a constant stream of the ______ fluid, which enters the uterine tube

- Received at the fimbriated end
- Constant stream of peritoneal fluid

Transport of sperm after insemination is achieved by what two factors?

1. Muscular contractions of the uterus
2. Motility of the sperm's flagellum

In most species the sperm remain viable within the female genital tract for ______ days. What two domestic species are an exception to this rule?

1-2 days
Dog and Horses (6-7 days)

How long can sperm remain viable inside the fowl? Turkey?

Fowl - 32 days
Turkey - 70 days
This is because birds have sperm host glands at their utero-vaginal junction which store and provide nutrients to the sperm

How long is the ovum viable after ovulation? (This is for all species typically)

24 hours

In most species, fertilization normally occurs in what region of the uterine tube? What are the only two domestic species that have a different site of fertilization?

Most species see fertilization in the ampulla
Dogs and Birds see fertilization at the infundibulum

How long after ovulation does fertilization typically take to occur?

12-24 hours

What is the name of the process that sperm must undergo in order to fertilize the ovum?


What process involves the removal of the glycoprotein coat and seminal plasma protein from the plasma membranes that overlie the acrosomal region of the spermatozoa?


Capacitation is followed by _________ which involves the release of enzymes that facilitate the penetration of the oocyte barriers

Acrosomal reaction

What are the three oocyte barriers that acrosomal enzymes, hyaluronidase and trypsin-like substance, help degenerate?

Corona radiata, Zona pellucida, and oocyte cell membrane

What occurs during the fertilization reaction? What does this help to prevent?

Fertilization membrane forms which helps to prevent polyspermy

What occurs during the zona reaction? What does this help to facilitate?

Chemical changes within the zona pellucida that facilitate the fertilization reaction (prevention of polyspermy)

When the nuclei of the male and female germ cells swell they are then referred to as...

Pronuclei - these are what will fuse together reforming a diploid cell/zygote (So you can say that the pronucleus is the intermediate stage between fertilization and fusion)

The restoration of the diploid chromosomal number, sex determination, and the initiation of cleavage, all are the result of ...


What form of twin results from one ovum being fertilized and subsequently dividing at the blastocyst stage into two genetically identical masses?


What is the definition of Ectopic pregnancy?

This is when the egg is fertilized away from the uterine tube as is lost in the peritoneal cavity where it will implant on a separate peritoneal surface (this results in early embryonic death)

What is a freemartin? What species is this unique to?

The result of a dizygotic pregnancy (with one boy and one girl) in which the male sex hormone (testosterone) limits the sexual characteristics of the female fetus, leading to a sterile heifer - this is typically seen in Cattle

Polyspermy is more common in what species?


What term is defined as the impregnation by successive acts of coitus, of two or more ovum that were liberated at approximately the same time, by two of more different males? What species is this common in?

Superfecundation - typically seen in dogs and cats

What term is defined as a pregnant female ovulating, conceiving and producing a second younger fetus? What species is this common in?

Superfetation - typically seen in pigs

What domestic species see the shortest gestation period?

Queens - 60 days

What domestic species see the longest gestation period?

Mare - 335-345 days

What is the gestation period of the Bitch?

60-65 days

Match the following species to the following gestation periods
A. 148-150 days
B. 279-282 days
C. 114-120 days

Cow - B
Ewe - A
Sow - C