Embryology Flashcards
What is the Allantois?
A disposal sac for certain metabolic wastes produced by the embryo. The membrane of the allantois also functions with the chorion as a respiratory organ
What is the Chorion?
Together with the allantois, exchange gases between the embryo & the air. Allows oxygen & carbon dioxide to diffuse freely across the shell
What is the Yolk sac?
Contains the yolk, a stockpile of nutrients. Blood vessels in the yolk sac membrane transport nutrients from the yolk into the embryo
What is the Shell?
Protects the embryo and keeps it from drying out, but it flexible to allow gas exchange. Can be leathery
What is the Amniotic cavity?
Filled with the amniotic fluid, protects the embryo, cushions against mechanical shock
What is the amnion?
The membrane surrounding the amniotic cavity
At some stage of life, all vertebrata have 8 characteristics. Name three.
- Brain
- Mouth
- Dorsal, hollow nerve cord
- Pharyngeal slits or clefts
- Anus
- Notochord
- Muscle segments
- Muscular, post-anal tail
What three characteristics distinguish vertebrates from other chordates? Briefly describe.
- Vertebral column: vertebrae; series of bones that make-up the back bone and surround dorsal nerve cord
- Cranium: or skull; bone that surrounds and protects the brain
- Endoskeleton: internal skeleton of cartilage or bone
What is an embryo?
The phase between fertilisation and birth
To become an embryo, 4 things had to be done. What were they?
- Build from a single cell
- Respire before lungs
- Digest before a gut
- Form orderly arrays of neurons before “thinking”
Starting at Maturation, what is the vertebrate life cycle of fertilisation
(1) Maturation
(2) Spermatogenesis/Oogenesis
(3) Fertilisation (Zygote)
(4) Cleavage (Blastula)
(5) Gastrulation (Germ layers)
(6) Neurulation (Nervous system)
(7) Organogenesis (Organs)
(8) Cytodifferentiation (Specialised cells)
(9) Individual Life
(10) Growth
(1) Maturation
Steps 3 through 8 are part of EMBRYOGENESIS
Briefly describe the difference between Oviparous, Viviparous & Ovoviviparous
Oviparous: Develop & Hatch in egg
Viviparous: Develop within mother & produce live young
Ovoviviparous: Similar to viviparous & produce live young - NO PLACENTA e.g. sharks
What does isolecithal mean?
Large distribution of yolk - Nucleus & cytoplasm within yolk
Mammals
What does Telolecithal mean?
Yolk is found within the cytoplasm at the vegetal pole. Nucleus is found at the animal pole
Reptiles & birds
What does Centrolecithal mean?
Nucleus is within yolk, yolk is within cytoplasm
spiders
What does Microlecithal mean?
Small amount of yolk - mammals
What does Mesolecithal mean?
Small amount of yolk - amphibians
What does Macrolecithal mean?
Large amount of yolk - fish, reptiles & birds
Briefly describe cleavage
- Series of mitotic division
- From zygote to morula to blastula/blastocyst
What are blastomeres?
Individual cells during cleavage
What is a blastocoel?
cavity in the blastula
What is a holoblastic?
Full cleavage - microlecithal
What is a meroblastic?
- Partial cleavage - macro & telolecithal
What is the subgerminal space?
Cavity between blastoderm & yolk