Development of Male and Female Flashcards
What are the three layers of the embryo?
- endoderm
- mesoderm
- ectoderm
Which organs/systems develop from the ectoderm?
- vagina and vestibule
- penis and clitoris
- mammary glands
- nervous system
Which organs/systems develop from the mesoderm?
- gonads
- uterus, cervix, cranial vagina
- epididymis, ductus deferens
- accessory sex glands
What are the three fetal membranes?
- amnion (inner)
- allantois
- chorion (outer)
Which is the first organ to develop?
brain
- then heart and liver
What is Schistomus reflexus? What are the morphologic problems?
- fatal congenital disorder
- spinal inversion
- exposure of abdominal viscera due to fissure of the ventral abdominal wall
- limb ankylosis
- positioning of the limbs adjacent to the skull
- lung and diaphragm hypoplasia
What events occur in the 1st trimester?
- migration of primordial germ cells from yolk sac
- sex cords develop in gonad, paramesonephric ducts develop
In what trimester does formation of the broad ligament occur?
2nd
In what trimester does testicular descent occur?
2nd - bull and ram
3rd - boar and colt
When is development of the ducts and testes/ovaries?
between 1st and 2nd trimesters
What is karyotype?
the chromosomal complement of an organism
- number of chromosomes followed by XX or XY
What is genotype?
the allele genetic constitution of an individual
What is phenotype?
observed characteristics of an individual
- morphology, development, blood type, and behavior
What is a chimera?
- single organism composed of genetically distinct cells
- produced by fusion of two different zygotes in a single embryo
What is a mosaic?
an individual with two different cell lines that originated from that same individual
How is chromosomal sex determined?
determined at fertilization by the type of sex chromosome contributed by the sperm
How is gonadal sex determined?
determined by “sex determining region” of the Y chromosome
- SRY gene
How is phenotypic sex determined?
determined by substances produced in male testes to cause regression of female tract and formation of male tract
What is the mesonephros, and what happens to it in the male and female?
- intermediate kidney
- forms efferent ducts in the male
- regresses in the female
What happens to the mesonephric/Wolffian ducts in the male and female?
- forms epididymis and ductus deferen in the male
- regresses in the female
What happens to the paramesonephrics/Mullerian ducts in the male and female?
- regresses in the male
- forms uterus oviducts, and cranial vagina in the female
What is formed by the primitive sex cords in the male and female?
- forms seminferous tubules in the male
- regresses and forms primitive follicular cells in the female
Describe the determination of physical sex organ characteristics in a male
- testis determining factor (TDF) and SRY genes on the Y chromosome cause development of testes and testosterone
- anti-mullerian hormone causes degeneration of paramesonephric ducts and causes leydig cells to differentiate
- dihydrotestosterone causes development of penis, scrotum, and accessory sex glands
