Mammals 4 & 5 Flashcards
What glands have therians lost?
Uterine glands that make the shell and other egg components
All therians have a placenta; what is it formed from?
Extraembryonic membranes of the fetus
What is embryonic diapause?
When the embryo is maintained in a state of arrested development prior to implantation
Why does embryonic diapause happen?
Enables mother to space out successive litters and to separate the time of mating and fertilization from the start of gestation
***diapause allows mating and birth to occur at optimal times of the year
Where are the testes retained in monotremes?
Retained in the abdomen (like in other vertebrates)
Where do therians retain their testes?
Most have testes that descend into a scrotum during development
- some retain them in the abdomen: original position or partially descended
What is the value of a scrotum?
Traditionally thought to provide cooler environment for sperm- however, there is no correlation between body temp and testicular position among mammals
Why does the vervet monkey have blue balls?
The balls appear blue because of the scattering of light by the skin itself. The collagen fibres are unusually neat and orderly to produce the blue hue
Why does the Northern Giant Mouse Lemur have huge testicles?
They have the proportionately largest testicles of any mammal- this is linked to frequent mating and strong sperm competition among males
In all therians, where do ureters drain from?
The kidney into the bladder
Why do the ureters pass laterally around developing reproductive ducts to enter the bladder?
Allows the oviducts to fuse at midline for much of their length
All placentals have a single mid-line vagina, but what kind of uterus?
Bipartite uterus (occurs as a developmental abnormality in humans)
Where does the vasa deferentia loop around?
Loops around the ureters in their journey from the scrotum to the urogenital sinus
What are the urogenital sinus and alimentary canals like in placentals?
They have separate openings with a distinct external space (the perineum) between them
Do placentals require a period of lactation?
Yes
Where do ureters pass through in marsupials?
Ureters pass medial to developing reproductive ducts to enter bladder- prevents oviducts from fusing at midline
-vasa deferential do not have to loop around ureters
What is the female reproductive system of a female marsupial like?
-2 lateral vagine unite anteriorly from which 2 separate uteri diverge
What is the male reproductive system of a male marsupial like?
They have bifed (forked) penis to complement the female anatomy
Where is the birth of the young in marsupials?
Through the midline structure (median vagina or pseudovaginal canal)
What parts of marsupial neonates are well-developed so the newborn can attach itself to a nipple and begin suckling?
Well-developed forelimbs and relatively large lungs
What parts have advanced development vs delayed in marsupials?
Advanced: jaws, secondary palate, facial muscles and tongue
Delayed: central nervous system
Where are the nipples of most marsupials?
In the pouch- newborns climb upward to attach themselves to nipple
How do kangaroos (and other marsupials) aid in the newborns journey?
They lick a path from the vagina to the pouch (wtf)
How does milk vary in marsupials and montremes over time?
First milk is dilute and rich in protein, while later milk is concentrated and rich in fats
What is concurrent asynchronous lactation observed in some kangaroos?
Mother can produce different kinds of milk at each nipple for different ages of young
