Download ANS 3319C Reproductive Physiology and Endocrinology Lab

ANS 3319C Reproductive Physiology and Endocrinology Lab
Take Home Message: Embryonic Development (25 pts: Spring 2014)
Name: _________________________________
Lab Day & Time: _____________
1) What is the definition of “cleavage” as it relates to embryo development (1 pt)?
Mitotic cell division of a zygote without an increase in cell mass 2) Approximately day 7 of gestation the blastocyst is formed. The blastocyst is composed of two distinct
cell types, which have very unique functions relative to embryo development. Please answer the
following questions relative to blastocyst development.
a) Please list the two distinct cell types that comprise the blastocyst and indicate what part of the
developing conceptus they eventually result in (2 pts).
Cell Type #1: Inner cell mass gives rise to the embryo proper. Cell type #2: Trophoblast gives rise to the chorion of the placenta. b) Cattle and pig embryos “elongate” during the second week of gestation. Please describe what type
of growth elongation is and what the difference in elongation is between cows and pigs (2 pts).
Elongation is logarithmic and filamentous growth of the embryo. In pigs elongation is very rapid over a couple of hours and in cows it is extended over a couple of days. c) In what farm animal species does elongation not occur and what is the shape of the developing
blastocyst in this species (1 pt)?
The equine embryo does not elongate and it is a spherical embryo. 3) The early developing embryo forms specific tissue layers that eventually differentiate into the extraembryonic membranes and organs of the fetus. Please list the three germ layers and provide four
examples of the type of tissues and (or) organs they develop into (3 pts)
a) Ectoderm: CNS, sense organs, mammary glands, sweat glands, skin/hair, hooves b) Endoderm: digestive tract, liver, lungs, pancreas, thyroid gland, most other glands c) Mesoderm: circulatory system, skeletal system, muscle, reproductive organs, kidneys, urinary tracts 4) The placenta is composed of several membranes and each membrane has a specific function and the
membranes combined provide a collective function and primary function. Please answer the following
question relative to the placenta.
a) What is the primary of the placenta (1 pt)?
The primary function of the placenta is to accommodate the fetus throughout gestation and to allow for nutrient transfer from the maternal circulation to the fetal circulation so the fetus can grow and develop. Continued on the back!!!!!
b) Please list the three major placental membranes and describe their functions (6 pts).
1. Amnion: Protects fetus from injury, provides lubrication during parturition, and serves as a reservoir for urine and waste. 2. Allantois: Fuses with chorion to form the chorio-­‐allantoic placenta. Carries blood vessels of the umbilical cord, which attaches fetus to the allantois. Reservoir for nutrients and waste. 3. Chorion: Attaches to uterus, absorbs nutrients from uterus, allows maternal/fetal gas exchanges. Produces hormones. 5) As the mammalian placenta grows & develops during gestation, it either attaches or invades the uterus.
Please answer the following questions relative to the types of placental attachments in mammals
a) The type of placental attachment is determined by the distribution of the villi on the surface of the
chorion. Please list the type of chorionic villous pattern for each species listed below. In contrast,
the “maternal fetal barrier” or “maternal separation” is descriptive of whether the placenta attaches or
invades the uterus. Please indicate the type of maternal fetal barrier there is between the chorion
and maternal blood supply for each animal. Additionally, please list the type of maternal separation
for each respective animal type using the terms attaches, semi-invasive, or invasive (5 pts).
Animal Chorionic villous pattern Maternal separation Pig diffuse Epitheliochorial & attaches Mare diffuse/microcotelydons Epitheliochorial & attaches Cow & sheep cotyledonary Epitheliochorial & attaches Dog & cat zonary Endotheliochorial & semi-­‐invasive Humans & primates discoid Hemochorial & invasive b) What is the function of the “chorionic-villi” that project off the surface of the chorion (2 pts)?
The function of the villi is to increase the surface area of the placenta to increase nutrient exchange. c) Relative to answer of the previous question, why do you think it would be advantageous for the pig
to develop a diffuse placenta instead of a cotyledonary placenta (2 pts)?
The pig is a polytocous species with a litter size of 12-­‐15 piglets. Therefore, an extremely large amount of nutrients are needed to allow for adequate fetal growth and developing. The diffuse placenta allows for an increase in surface area so that nutrient transfer is maximized. If the pig had a cotyledonary placenta, there would probably not be enough nutrients to allow for proper fetal development.