L2 Vertebrates from egg to embryo Flashcards
(38 cards)
What are vertebrates?
Vertebrates are all organisms that have a backbone or a vertebral column
What are chordates?
Chordates are a phylum of animals that share several key features
What are the key features of a chordate?
-Head (with a brain)
-Dorsal nerve cord - runs along their back (dorsal side) and is hollow
-Notochord - flexible rod that provides skeletal support
Do vertebrates all develop the same way?
No they develop in different ways. However during the pharyngeal stage, they look similar
What is the Pharyngula stage?
This stage is a critical period in the embryonic development of vertebrates. It’s a stage of remarkable similarity across different vertebrate species
What are somites?
Somites are transient (lasts a short time) but vital structures in vertebrate embryos.
Somites form in a repeating pattern along the body axis, giving rise to the segmented appearance of the vertebrate body plan
What structural feature is common in all vertebrates at the Pharyngula stage?
- Pharyngeal pouches
- Somites
What is segmentation?
Dividing metameric structures into repeated units/segments
Explain the early stages of development.
- Sperm and oocyte combine (Fertilisation) to for a zygote.
- Zyogote undergoes cell divisions called cleavage
- The new divided cells form a hollow ball called blastomeres.
- As cleavage continues, blastomeres eventally form a solid ball of cell called a morula
- Morula rearrange themselves to form a hollow sphere called a blastula
What is blastula composed of?
Blastoderm on the outside
Blastocoel on the inside
How would you calculate the exponential growth of cells?
N (start) X 2^(tXf) = N (finish)
N = number of cells
t = time
f = frequency of division
For example at 2 hours after fertilisation:
1 X 2^(2X2) = 16 cells
What happens after fertilisation: egg activation?
After sperm entry a wave of free Ca2+ ions travels across the egg
Calcium is needed to activate egg and start division
What happens after every round of division in context to calcium composition?
After each round of division there is a burst of calcium ions so synchronisation occurs
What are the differences between the cell cycles of early embryo and regular? (4)
- Rapid, synchronous divisions - cleavage
- S (DNA replication) and M (mitosis) phases only; no G phases
- G1 transcription is suppressed (no mRNA and protein)
- Maternal stores (RNA and protein) provide building blocks for DNA synthesis and growth
Maternal stores - Components from the female oocyte.
Do embryos need maternal RNA over time?
Initially maternal RNAs is needed but as time goes on, zygotic RNA raises
What are the characteristics of the cell cycle when zygotic genome activation occurs?
Characteristics:
* Cell cycle slows
* Cell cycle becomes asynchronous
* Cell movement begins
What does gastrulation mean?
Movement of cells inside of the embruo to form the 3 germ layers
What are the 3 layers of germ ?
Endoderm - inside
Mesoderm
Ectoderm - surface
What are the derivatives of Ectoderm? (4)
Developop = derivatives
Neurons,glia, epidermis and pigment cells.
What are the derivatives of endoderm? (3)
Lungs, gut and associated organs.
What are the derivatives of the mesoderm? (6)
Muscle
Cartilage, bone
Dermis
Kidney
Heart
Blood
What are the cells gastrulation gives rise to first?
Epithelial cells and mesenchymal cells.
What does amorphous mean?
No defined shape
Describe 2 features of mesenchymal cells
Mesenchymal cells move easily and are amorphous ( no defined shape)
