Development Flashcards
What are the three layers of the trophoblast?
Endoderm
Mesoderm
Ectoderm
What is the difference between an embryo and fetus?
Embryo - organism in early stages of development that has not acquired anatomical form that is readily recognizable in appearance as a member of a specific species
Fetus - recognizable as a species. Marked by placentation development
What trophoblastic layer do the gonads, and majority of the reproductive tracts develop from?>
Mesoderm
The hypothalamus and anterior pituitary develop from what trophoblastic layer?
Ectoderm
The vagina and vestibule or penis develops from what trophoblastic layer?
Ectoderm
What provides nourishment for the early embryo?
Yolk sac
What layer of the placenta is in contact with the mother?
Chorion
In the placenta, the embryo is contained within the ________ cavity
Amniotic cavity
T/F: organogenesis occurs outside the embryo
True
Brain and heart develop first
Body wall forms around them — > fetal membranes
Where do gonadotropes originate?
Originate from yolk sac and migrate into embryo to genital ridge to form ovaries/testies
What do you call the congenital disorder where there is exposure of abdominal visceral and spinal inversion because of a fissure in the ventral abdominal wall ?
Schistosomus reflexus
What is the gestation length of a cow?
285days
Gestation length of a dog?
62days
Gestation length of a horse?
340days
What reproductive events occur in the first trimester?
Migration of primordial germ cells from yolk sac
Sex cords develop in gonad, paramesonephric ducts
Sex evident from structures
What reproductive structures develop int he second trimester?
Develop into male Or female structures
Formation of broad ligament
What occurs in the 3rd trimester in males
Testicular descent
What is sex differentiation vs sex determination?
Sex differentiation: the process whereby a group of unspecialized cells develop into a functional group of cells with a common function
Sex determination: a system that determines the sexual characteristics of an organism which generally consists of genetic or hormonal parameters
What do you call the chromosomal complement of an organism?
Karyotype
What is genotype vs phenotype?
Genotype= genetic alleles coding for a specific trait
Phenotype = observed traits (dependent on genotype)
What is a chimera?
Single organism composed of genetically distinct cells. Fusion of two zygotes in a single embryo
What is a mosaic?
An individual with two different cell lines that originated from the same individual ( one zygote )
What is chromosomal sex, vs gonadal sex vs phenotypic sex?
Chromosomal - XX or XY (karyotype)
Gonadal sex = presence of testies/ovaries/ovotestis (determined by Sry gene on Y chromosome)
Phenotypic sex = determined by substances produced in testis to cause regression of female tract and formation of male tract
What structure forms the male efferent ducts but will regress in the female?
Mesonephros
What structure will form the epididymis and ductus deferens but will regress in the female?
Mesonephric ducts
What structure will develop into the uterus and oviduct and cranial vagina in the female but will regress in the male
Paramesonephric ducts (Müllerian ducts)
What do the primitive sex cords differentiate into in the male and the female?
Male - seminiferous tubules
Female - regress, primitive follicular cells
What are the key players in sex determination?
Testies determining factor (TDF) and SRY region on Y chromosome. —> testicular Development and testosterone production
Dihydrotestosterone—> development of penis, scrotum, and accessory glands
Anti-mullerian hormone — > degeneration of paramesonephric duct
During fetal maturation, the testis descend into the scrotum.. is responsible for this?
Gubernaculum
Attached at the inguinal ring to peritoneum
Shortening/fattening pulls testis from their position caudal to the kidney into the scrotum
