Animal Development Flashcards
What is fertilization?
The formation of a diploid zygote from a haploid egg and sperm
Describe fertilization
Begins with the sperm penetrates the protective layer around the egg. Initiating the acrosomal (acrosomes release hydrolytic enzymes to digest egg surroundings) reaction.
Receptors on the egg surface find molecules on the sperm surface
This fusion depolarizes egg cell membrane and sets up a fast block to polyspermy
What is a cortical reaction?
After the sperm and egg bind faecal beneath the egg plasma membrane release their contents in form of fertilization envelope
The cortical reaction requires a high concentration of calcium ions in the egg
What substance do sperm have to travel through to reach the zona pellucida?
They travel through a layer of follicle cells and bind two receptor in the zona pellucida
What is cleavage?
A period of rapid cell division without growth after fertilization. The cytoplasm is cleaved into many smaller cells called blastomeres the blastula is a ball of cells with a fluid filled cavity called a blastocoel
Describe differences in cleavage patterns in other animals
Cleavage is asymmetric yoke distributed, unevenly between the vegetal hemispheres and the animal hemisphere
Holoblastic cleavage is a complete division of egg and occurs in species whose eggs have little or moderate amounts of yolk, such as sea urchins, and frogs
Meroblastic cleavage: incomplete division of egg occurs in species with yolk rich eggs like reptiles and birds
What are the embryonic germ layers?
Three layers produced by gastrulation
Ectoderm forms the outer layer
Endoderm lines, the digestive tract
Mesoderm partly fills the space between the endoderm and ectoderm
What is the archenteron?
A blind ended tube formed by invagination
What is the blastopore?
The open end of the archenteron
How is the primitive gut formed?
The tip of the archenteron reaches the embryo surface, completing embryo now a gastrula
What forms from the ectoderm? (Outer layer of embryo)
Epidermis of skin, including sweat, glands, and hair follicles
Nervous and sensory system
Pituitary gland adrenal medulla
Jaws and teeth
Germ cells
What derives from the mesoderm?
Skeletal and muscular system
Circulatory lymphatic systems
Excretory and reproductive systems
Dermis of skin
Adrenal cortex
What arises from the endoderm? (Inner layer of embryo)
Epithelial lining of digestive track and associated organs like liver and pancreas
Epithelial lining of respiratory excretory and reproductive tracts and ducts
Thymus, thyroid, that hurt and parathyroid glands
What are stages in the early embryonic development of humans?
- blastocyst reaches uterus
- blastocyst implants
- Extra embryonic membrane start to form and gastrulation begins.
- Gastrulation has produced a three layered embryo with four extra embryonic membranes.
What are the four extra embryonic membranes that form around the embryo?
Chorion - functions in gas exchange
Amnion - encloses the amniotic fluid
Yolk sack - encloses the yolk
Allontois - disposes of waste products and contributes to gas exchange
What is organogenesis?
When the various regions of the germ layers develop into rudimentary organs
The notochord forms from the dorsal mesoderm
Signalling molecule secreted by the notochord and other mesodermal cells induced the neural plate formation from the ectoderm
Describe neurulation
Neurode soon curves, inward, forming neural tube, becomes a central nervous system
Notochord disappears before birth, but contributes to parts of the discs between vertebrae
What is cell migration in organogenesis?
Neural crest cells develop along the neural tube of vertebrates and migrate in the body, eventually forming various parts of the embryo
The mesoderm lateral to the notochord forms blocks called somites
Parts of the somites dissociate to form me cells which migrate individually to new locations
What is the role of cytoskeleton in morphogenesis and migration?
It promotes convergent extension through rearrangement of cells of a tissue that caused it to become narrower and longer
Convergence - the cell elongate and crawl between each other
Extension - sheets of cells become longer, and narrower, forming a single file line of alternating cell types
Describe the formation of vertebrate limbs
Inductive signals play a major role in pattern formation development of spatial organization
What is the apical ectodermal ridge?
A limb bud regulating region
Regulates positional information indicating location, along three axis proximal distal axis anterior posterior axis dorsal ventral axis
The second region is the zone of polarizing activity
Mesodermal tissue under the ectoderm where the posterior side of the butt is attached to the body it influences development by a protein, signal called sonic hedgehog and inductive signal for limb development
