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57 terms

Embryology

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An _____ is an organism in the early stages of development that has not acquired the anatomical form that is recognized as a member of that particular spp.
embryo
What is special about early embryonic death?
the embryo dies, you wont see aborted fetuses or anything, it is simply reabsorbed by the mother
A ____ is a potential offspring within the uterus that is generally recognized as a member of that spp.
fetus
The change between an embryo to a fetus is marked by the development of a ______.
placenta
The ______ _____ mass of the embryo becomes the animal.
inner cell
Nerves, skin, mammary glands, hair and the caudal vagina/vestibule, and penis/clitoris are all derived from this germ layer.
ectoderm
Muscles, the skeleton, the CVS, and most of the repro. system (cranial vagina) are derived from this germ layer.
mesoderm
The endoderm gives rise to these three body systems.
GI, lungs, and endocrine
Which part of the repro. tract is derived from two different germ layers?
the vagina (cranial vagina = mesoderm, caudal vagina/vestibule/clit = ectoderm)
What is the functional unit of the placenta called?
alantochorion
The ____ is what you palpate to detect pregnancy, the earliest you can feel it is 42 days in the cow, and is a small hard water balloon the size of a finger.
amnion
What is the earliest time you can palpate a preg. in a bovine? what structure are you feeling?
42 days; amnion
Fluids ingested (absorbed) by the embryo from the amnion are excreted into the _____, which is basically the bladder of the fetus and _____is the substance secreted into it.
allantois; urine
Interestingly, _______ happens OUTSIDE the embryo.
organogenesis
What is shistasoma reflexis?
when the organs are never fully enclosed in the body (because organogenesis happens outside of the body)
Teratogenic drugs have the most effect on the _______ period of pregnancy.
embryonic
Migration of the primordial germ cells from the yolk sac to the precursors of the repro. organs happens during the _______ trimester.
first
During what trimester do the sex cords develop in the gonads, as well as the paramesonephric ducts?
first
During what trimester do the ducts of the testis and ovaries develop?
second
The formation of the broad ligament of the uterus happens during this trimester.
second
Bulls and rams testis should be descended by the _____ trimester. What can you infer from this information about a bull or ram who is cryptorchid at birth?
second; the testis will never descend b/c the time has come and gone
Testicular descent happens in the _____ trimester in colts, boars, and humans.
third
In which spp. can testicular descent occur normally up to 6 mos. after birth?
canines
Dogs aren't considered cryptorchid until when?
6 mos after birth.
___ ______ is the process where by a group of unspecialized cells develop into a functional and recognizable group of cells that have a common sexual function.
sex differentiation
______ sex (karyotype) is determined at fertilization in mammals by the sex chromosome contributed by the SPERM.
chromosomal
_____ sex only tells the observer if the animal is chromosomally male or female.
chromosomal
_____ sex is determined by the sex determining region of the Y chromosome, the SRY gene.
gonadal
If an animal has the SRY gene on the Y chromosome, it will develop?
testis
_______ sex is determined by substances/hormones, or the lack thereof, produced in the testis causing regression of the female tract and formation of the male tract.
phenotypic
What happens to the mesonephric (wolffian) ducts when exposed to testosterone? what about when there is no testo., i.e. the animal is female?
they become the male epididymis and ductus deferens; they regress
The paramesonephric ducts ____ in males, and become the ______ _____, and _____ in females.
regress; uterus, oviducts, and cranial vagina
The primitive sex cords become the ______ in males, and _____ in females becoming the ______ _____ cells.
seminiferous tubules; regress; primitive follicular
The _____ gene on the Y chromosome causes the production of hormones that cause the development of the ______.
SRY; Testis
Testosterone produced by the _____ cells of the embryologic testis cause the ______ cells to produce anti-mullerian hormone which causes the regression of the __________ ducts.
leidig; sertoli; paramesonephric
Testosterone conversion in the embryo to ______ causes development of the penis, scrotum,and accessory sex glands.
DHT
The karyotype describes the ______ compliment of the embryo.
chromosomal
The ______ is described by the alleals and genetic constitution of an individual.
genotype
The ______ is defined by the morphology, development and blood type of an individual.
phenotype
A ____ results from the fusion of two different zygotes in a single embryo.
chimera
A ____ results from the combination two different cell lines in an individual that originate from the same individual.
mosaic
The metanephros in the embryo becomes the _____.
functional kidney
The MESOnephros is the ______ kidney in the embryo and form the ______ in males and _____ in females.
intermediate; efferent ducts; regresses
The hormone coded for by the SRY gene on the Y chromosome that is the initial hormone that causes male sex differentiation is?
testis determining factor
What hormone is responsible for the development of the male duct system? the development of the penis, scrotum and accessory sex glands?
testosterone; DHT
The _______ duct beomes the fallopian tubes and uterus in females .
paramesonephric
The regressing epithelial cords in females give rise to the ______ _____.
primordial follicles
The ____ stage of development consists of rapid growth and maturation of the organs that were produced during the _____ stage.
fetal; embryonic
The broad ligament formation and testicular descent happens during the ___ stage of development.
fetal
The ____ is the structure responsible for testicular descent.
gubernaculum
_____ possess both ovaries and testis and is most often seen in _____ and they are usually X__ chromosomally.
hermaphrodites; swine; XX
Pseudohermaphrodites possess only one type of gonad, and are named for the _____.
gonad
A female pseudohermaphrodite has _____ and is phenotypically _____.
ovaries; male
The polled, or non-horned gene is _____.
dominant
Most polled intersex goats are _____ pseudohermaphrodites and genotypically _____.
male; female (XX)
A ____ is a heifer born twin to a bull, there is a chimera of xx/xy from placental anastamosis, the xy prevents _____ development, but males also have decreased fertility.
freemartin; uterine
A tortoise shell cat is an example of a ________, in that 2 embryos are fused by placental blood vessel anastamosis.
chimera