Embryology Midterm Flashcards
Gametogenesis
- process by which germplasm are converted into highly specialized sex cells (gametes) that are capable of uniting at fertilization and producing a new being
Where is the Primordial Germ Cells origin? What do they develop into?
- originate in the wall of the yolk sac
- develop into gametes
Pre-embryonic Period
- development of the gametes up to implantation
Embryonic Period
- from implantation to the origin of the primordia of the organs and the formation of the basic body form
Fetal Period
- The period of growth and maturation of the organ-system to become competent to assume their specialized functions
Corpus Luteum
- After ovulation, the ruptured follicles are converted into this
- secretes progesterone to facilitate the implantation and maintain the conceptus
Induced Ovulators
- ovulation is spontaneous in most mammals
- the cat and rabbit are the exception
- ovulation is only induced by coitus
In the Prenatal period what phases are most susceptible to abnormal changed?
- Embryonic Period
- Fetal Period
- Pre-embryonic period
Ampullary Region of the Uterine Tube
- site of fertilization in most animals
Infundibulum of the Uterine Tube
- site of fertilization in dogs and birds
Capacitation
- involves removal of glycoprotein coat and seminal plasma protein from the plasma membranes that overlies the acrosomal region of the spermatozoa
Acrosomal Reaction
- after capacitation
- Involves the release of enzymes (hyaluronidase and trypsin like substance) in the acrosome
- The action of these enzymes facilitate the penetration of the oocyte barriers
Zona Reaction
- chemical changes in the zona pellucida
Fertilization Membrane (fertilization reaction)
- develops to prevent further entry of sperm into oocyte, or polyspermy
Freemartin
- In Cattle
- female is born infertile and with male characteristics
- dizygous twinning where the development of a common circulation of placental anastomosis occurs
- If the twins are of opposite sex, the development of the genital system is retarded in the female embryo under the influence of the testosterone produced in the male embryo
Superfecundation
- Impregnation by successive acts of coitus, of two or more ovum that were liberated at approximately the same time, by two or more different males
- cats and dogs
Superfetation
- When a pregnant female ovulates, conceive and produce a second younger fetus
- pigs
Gestation Periods in:
- Mare
- cow
- ewe/goat
- sow
- bitch/queen
- 11 months
- 9 months
- 5 months
- 4 months
- 2 months
Cleavage
- It is a series of mitotic cell divisions without overall increase in the size of the zygote, which is still enveloped by zona pellucida
- production of blastomeres
Total, or Holoblastic Cleavage
- complete division of the zygote
- Isolecithal eggs
- > in mammals where a small amount of yolk is present and equally distributed
Partial, or Meroblastic Cleavage
- prevents complete division of the zygote
- Polylecithal Egg
- > In birds, there is a massive amount of yolk
Blastogenesis
- rupture of the zona pellucida
- formation of the Blastocoel, or a fluid filled cavity
- embyro is called a blastocyst
- marked by increase in size and shape of embryo
Embryonic Disc/Inner Cell Mass/Blastodisc
- develop into the main embryo
- cells of the blastocyst
Trophoblast Cells
- facilitate the absorption of nutrients early in development
- cells of the blastocyst
Gastrulation
- the embryonic disc/inner cell mass/blastodisc is rearranged to form the 3 germ layers
1. Ectoderm
2. Mesoderm
3. Endoderm
Primitive Gut, or Archenteron
- enclosed cavity in the endoderm
Delamination
- the process of detachment of the cells from the inner cell mass
- development of the endoderm
Notochord
- induces the ectoderm to form the neural ectoderm, or neural plate
- Later as an adult, the notochord regresses and persists as the nucleus pulposus of the invertebral disc
Mesoderm Gives Rise to:
- 4 mesodermal cells
1. Notochord
2. Paraxial Mesoderm
3. Lateral Mesoderm
4. Intermediate Mesoderm
Paraxial Mesoderm forms the:
- forms the somites
- > Sclerotome, Myotome and Dermatome
Sclerotome, Myotome and Dermatome give rise to:
- Vertebral Column
- Epimere and Hypomere
- epaxial and hypoaxial muscles - Dermatome
- Dermis
Lateral Mesoderm
- Somatic Mesoderm
- outer - Splanchnic Mesoderm
- inner - Coelom
- cavity between these two layers
Somatopleure
- ectoderm + somatic mesoderm
Splanchnopleure
- endoderm + splanchnic mesoderm
Intermediate mesoderm
- the junction between the paraxial and lateral mesoderm
Intraembryonic Germ Layer
- the part of the germ layer that underlies the embryonic disc
Extraembryonic Germ Layer
- the cells lying peripherally under the trophoblast
- develop into the extraembryonic, or fetal membranes
Most important aspect during establishment of body form
- the transformation of the embryonic disc from an elongated flat disc (gastrulation phase) into a rough curved cylindrical embryo
Intraembryonic Somatopleure gives rise to:
- the lateral and ventral body walls
Extraembryonic Somatopleure gives rise to:
- constitutes the amnion and chorion
Intraembryonic Splanchnopleure gives rise to:
- the gut
Extraembryonic Splanchnopleure gives rise to:
- yolk sac and allantois
How does the yolk sac communicate with the gut?
- through the vitello-intestinal duct, or yolk stalk
Umbilical Cord Contains:
- All fetal, or extraembryonic membranes
- Yolk sac, or vitelline blood vessels
- Allantois, or umbilical blood vessels
How to determine the Approximate age of an embryo
- early age expressed by the number of somites
- later the crown-rump length is used
Amnion
- develops from extraembryonic somatopleure
- fluid filled sac around the embryo
- hydroamnion is an excess amount of amniotic fluid
Chorion
- outermost membrane
- develops from the extraembryonic somatopleure
- fingerlike projections called the chorionic villi develop over the surface of the chorion to make contact with the uterus of the mother
Yolk Sac
- develops from the extraembryonic splanchnopleure
- develops and forms temporary contact with the chorion called choriovitelline placenta
- well developed in birds and develop vitelline vessels
Choriovitelline, or Yolk Sac Placenta
- yolk sac makes temporary contact with the chorion
- regresses immediately in most mammals
- Functional in the first quarter of pregnancy in dog and horses
Allantois
- extraembryonic splanchnopleure
- reservoir for excretory products of the fetus
- umbilical vessels develop here
Superficial or Central Implantation
- uterine lumen or cavity
- ruminants, equines and porcine
Eccentric Implantation
- fold or pocket of the uterine wall
- rat or squirrel
Interstitial Implantation
- embedded into the uterine wall
- guinea pig, carnivores, bat and man
Mare Implantation Time
- 35 to 40 days
