Embryonic Growth Flashcards
Between conception and growth; Gestation
Prenatal Development
Prenatal subject classifications
Ovum, Embryonic, Fetal
Fertilization to implantation
Ovum
Organism reflects mature form
Embryonic
Longest phase; Species can be identified
Fetal
Shortly after parturition
Neonatal Development
Birth through maturity; What we typically manage in production systems
Postnatal Development
Time in uterus
Gestation period
Sheep Gestation
135 Days
Pig Gestation
114 Days
Cattle Gestation
285 Days
Turkey Gestation
28 Days
Chicken Gestation
21 Days
What can impact postnatal development?
Prenatal growth
Has selection for fewer days to market changed gestation?
No
What kind of animal grows slower and has a longer gestation?
Large Animals
Rate of prenatal growth is related to postnatal growth rate
Relative growth
Animals that grow slow at the cellular or tissue level require what to develop more size?
Additional time
How long does the Ovum Phase last?
11-14 Days
Ovary produces?
Oocytes, ova, or unfertilized eggs
What is the ovum surrounded by?
Zona Pellucida
Where does sperm fertilize the egg?
Oviduct
What is a fertilized egg called?
Zygote
What is the cascade of events in the ovum called?
Oocyte Activation
How soon does the rate of metabolism increase?
Immediately
Meiotic Divisions
- Extrusion of 2nd polar body
- Pronuclear formation
- Cytokinesis
2 pronuclei migrate to center of cell
Pronuclear formation
Development of daughter cells
Cytokinesis
Define Ovum Phase
- Rapid Cell Division
- Replication of DNA, but absent of protein synthesis
- Constrained within the zonal pellucida
- Lack supply of nutrients
A cell formed by cleavage of a fertilized ovum. Have excellent plasticity.
Blastomere
When does the end of the Ovum Phase Occur?
When the Zona Pellucida breaks down
A process where inner cells become more closely associated and leads to the Morula 20 to 30 cells
Start of Compaction
The ability of a single cell to divide and produce all of the differentiated cells in an organism
Totipotent
When will pregnancy rates be high?
- Embryo immobilized without damaging it
- Bisection process does not damage too many cells
- Embryos are bisected reasonably symmetrically
Progression from cleavage to blastula phase is characterized by two things:
- Increased # of blastomeres form into blastocyst
2. Formation of flattened layer of cells, known as trophoblast, and the inner cell mass
Formation of blastocoele
Blastulation
Cells committed to form embryonic or extraembryonic structures
Loss of totipotency
After the cell losses totipotency it becomes _____
plurapotent
Means stomach
gaster
Period when regions exert control over development rather than cells (loss of cellular anatomy); a lot of cell reorganization and movement
Gastrulation
The creation of shape; types of cell movement during gastrulation
Morphogenesis
Infolding of cell sheet into embryo
invagination
Inturning of cell sheet over the basal surface of an outer layer
Involution
Migration of individual cells into the embryo
Ingression
Splitting or migration of one sheet into two sheets
Delamination
The expansion of one cell sheet over other cells
Epiboly
Blastodisc means an egg is ____
infertile
Blastoderm means an egg is ____
fertile
What becomes a chick?
Epiblast
Becomes extra-embryonic membranes
Hypoblast
Cells in the epiblast layer begin to replicate in a region known as _____
Henson’s Node
Where is the Henson’s Node located?
At the dorsal caudal end of the developing embryo
Cells migrate inward through the primitive knot and result in third germinal layer
Primitive Groove
After cells begin to replicate, what develops?
Primitive streak
Skin and neural
Non-neural ectoderm (external layer)
Muscle, fat, and bone
Mesoderm (middle layer)
Respiratory and digestive
Endoderm (internal layer)
Development of the spinal cord precursors; develops simultaneously with gastrulation
Neuralation
In the neural crest region, cells migrate to the periphery of the embryo to form ______
Peripheral nerves
Mesoderm continues to develop and forms ____ adjacent to the ___ ____
Somites; neural tube
Occurs in a pattern from head to tail; occurs in paired fashion
Somitogenesis
Somites are paired on either side
Neural tube
Somite develops into
Sclerotome and Dermomyotome
Dermomyotome develops into
Dermatome and Myotome
Cells closest to the neural tube migrate around it and become the vertebral column
Sclerotome
Dermatome becomes____
dermis
Myotome becomes____
Muscle
Cell migration can be assisted by:
Chemotaxis and Morphogens
Cells follow a chemical trail
Chemotaxis
Factors produced in one location of a developing embryo but exert an effect on distant cells
Morphogens
Growth and development is a repeating series of these two things
Proliferation and Differentiation
Todipotent
Zygote and Morula
Plurapotent
Any tissues during prenatal growth and development that aren’t the zygote or morula
Sclerotome becomes____
skeleton
Day 1
Fertilized egg
Day 5-6
Blastocyst
Day 14-16
Gastrula
The placenta is important for the exchange of these gases and nutirents
Oxygen and Carbon Dioxide; Amino acids and glucose
Closely covers embryo; fills with amniotic fluid; shock absorption
Amnion
Membrane between fetus & mother; Villi “invade” endometrium
Chorion
Part of umbilical cord; exchange of gases; metabolic waste; webbed with blood vessels
Allantois
Fetal membranes
Amnion, chorion, allantois
Developing embryo penetrates the uterine epithelium
Interstitial implantation
Close contact of maternal epithelium and placenta
Superficial implantation
Two characteristics form the bases for classification of placental types:
1) The gross shape of the placenta and the distribution of contact sites between fetal membranes and endometrium.
2) The number of layers of tissue between maternal and fetal vascular systems
Almost the entire surface of the allantochorion is involved in formation of the placenta. Seen in horses and pigs
Diffuse
Multiple, discrete areas of attachment are formed by interaction of patches of allantochorion with endometrium. This type of placentation is observed in ruminants
Cotyledonary
The placenta takes the form of a complete of incomplete band of tissue surrounding the fetus
Zonary
A single placenta is formed and is this shape
Discoid
Dissuse is also ____
Epitheliochoral
Ruminants are cotyledonary while horses are ____
diffuse
Similar to epitheliochoral; placental epithelium and maternal blood seperated by connective tissue
Syndesmochorial
Zonary is also ____
Endotheliochorial
Discoid is also _____
Hemochorial placentation
Swine retain these maternal layers and have this type of placenta
Endometrial epithelium, connective tissue, uterine endothielium; Eitheliochorial
Ruminants and horses retain these maternal layers and have this placenta shape
Endometrial epithelium, connective tissue: Syndesonchorial
Dogs and cats retain this maternal layer and have this placenta shape
Uterine endothielium; Endotheliochorial
Do humans retain any maternal layers? What placenta shape do they have?
No; Hemochorial
