Bio 10 Fertilization and Development Flashcards
Fertilization #1
Exocytosis occurs as the tip of the sperm reaches the jelly coat. Acrosome releases enzymes to digest.
Fertilization acrosomal reaction #2
Enzymes create a hole while growing actin filaments form from the acrosomal process. They bind to the egg cell receptors.
Fertilization block #3
Contact and fusion of sperm and egg occurs. Membrane voltage depolarizes causing a fast block to polyspermy.
Fertilization Cortical reaction #4
Ca++ is released from the Endo Reticulum. Cortical granules in the egg fuse with the plasma membrane. Sperm bind receptors are removed and fertilization envelope forms.
Slow block to polyspermy
In Fertilization #4 when the fertilization envelope forms.
Fertilization in Mammals
Generally internal. Egg releases progesterone which aids in motility. After fusion the entire sperm is taken into the egg.
Cleavage
Rapid period of mitosis. S and M phases. 4 cells is Blastomeres, then becomnig a solid ball, Morula.
Blastocoel
Fluid filled cavity forms within the morula and begins to hollow, becoming blastula.
Yolk distribution
Most important driving force that influences the cleavage pattern.
Two poles: Vegetal pole = high in yolk
Animal pole = low in yolk.
Gastrula
After cleavage, cell division slows and the process is called gastrulation. Results endo, meso, and ectoderm.
Z -> M -> B-> G
Zygote -> Morula -> Blastula -> Gastrula
Archenteron
New central cavity which becomes the primative gut during gastrulation. Opening of the archenteron is called the blastopore.
Blastopore
Opening of the gastrula that forms the mouth in protostomes and anus in deuterostomes.
Protostomes
Mollusks, arthropods, and annelids
Deuterostomes
Chordates and echinoderms
Mollusks
Snails, oysters, clams, squids, octopuses. Most have hard shells (CaCO3) and open circulatory system where fluid called hemolymph moves in cavities. Coelomates (have a body cavity).
Arthropods
Most successfull of all animal phyla and largest category. Insects, crustaceans, spiders, millipedes. Segments bodies, hard chitinous exosketelon. Jointed appendages, thousands of photoreceptors, open circulatory system.
Grasshoppers use Malpighian tubules to aid in metabolic waste removal.
Annelids
Worms. Closed circulatory system (blood moves through vessels). Segmentation. Setae to move, provides traction to crawl and burrow. Ganglia. Nephridia - functional unit of excretion, regs body fluid comp and vol.
Arthropods, annelids and mollusks are …….
Protostomes. Mouth forms first and anus forms second.
Echinoderms
Detuterostomes: anus first then mouth formation.
Sea stars, urchins, cucumbers.
Are radially symmetrical (Symmetrical in all directions).
Decentralized nervous system, no brain.
Unique to them is a water vascular system involved in locomotion, gas exchange, and nutrients.
Chordates
Fish, amphibians, birds, mammals, reptiles, tunicates, and lancelets.
Bilateral symmetry. Notochord (skeletal support). Dorsal hollow nerve chord. that develops into the brain and spinal chord.
Chordates human dorsal hollow nerve chord
Becomes a gelatinous disk found between vertebrae. Muscular, post anal tail.
Tunicates and amphioxus classification exeception
Are classified as chordates but are invertebrates
Cnidaria
Hydras, jellyfish, corals, sea anemones. Unique stinging cells called nematocytes.
Platyhelminthes
Flatworms such as tapeworms and flukes.
Unsegmented, acoelomates (solid body animal lacking a body cavity).
Coelomate
Vertebrates have a body cavity derived from the mesoderm.
Porifera
Includes sponges: have choanocytes to trap food.
Nematode
Includes hookworms and pins worms (round worms). Pseudocoelomates. No circulatory system.
Coelomates, acoelomates, pseudocoelomates
Coelomates: Molusks, annelids, arthropods, echinoderms, mammals, chordates
Acoelomates: Platyhelminthes
Pseudocoelomates: Nematodes
Amphibians
Half aquatic, half terrestrial
Evolved from lobe finned fish that live in brackish, salty, water as in coastal wetlands.
Frogs, salamanders, toads, newts, and caecilians.
Moist skin is essential, for gas exchange. Some even lack lungs.
External fertilization. No amnion. Close circulatory system. Three chambered heart (2 atria, 1 ventricle).
Reptiles
Turtle, crocodilians, lizards, snakes.
Closed circulatory system. Bony exoskeleton and scaly skin. Have an amnion.
As amniotes they have terrestrially adapted eggs. Internal fertilization. Most have 3 chambered hearts, Crocs and allis have 4.
Birds descend from ____
Reptiles during the Jurassic times.
The Jurassic periods was part of the ___________ Era.
Mesozoic.
Most modern era: Cenozoic Era.
Ectoderm
Epidermis, glands on skin, some cranial bones, pituitary and adrenal medulla, the nervous system, the mouth between cheek and gums, and the anus.
Skin cells, neurons, nails, hair, and pigment cells.
Mesoderm
Connective tissues, bone, cartilage, blood, endothelium of blood vessels, muscle, synovial membranes, serious membranes lining body cavities, kidneys, lining of gonads. Connective tissues, notochord, dermis of skin,
Endoderm
Lining of the airways and digestive system except the mouth, rectum, and anal canal. Glands. Lungs, thyroid, and pancreas.
Organogenesis
Move of cells occurred in gastrulation, note the U shape structure. More shape change.
Which stages have the greatest shape changes in embryology?
Gastrulation and organogenesis.
Organogenesis in vertebrates
- Condensing of mesoderm forms the notochord. This is a rod of stiffened tissues that serves as a support structure in all chordates.
- Neural plate forms from the ectoderm and rolls into the neural tube becoming the CNS (brain and spinal chord).
- Somites are formed. Representing blocks of mesoderm which form vertebrae and muscles. Somites arrange along the notochord.
Amniotes
Birds, reptiles, and mammals. All contain a fluid filled sac called an amnion.
Extraembryonic membranes: Found in most shelled eggs. Located outside the embryo:
1) Yolk sac
2) Amnion
3) Chorion
4) Allantois
Yolk Sac
Encloses the yolk; provides needed nutrients
Chorion
Gas exchange, forms part of the placenta
Amnion
Absorbs shocks, keep embryo from drying out
Allantois
Disposes Nitrogen waste and gas exchange.
O2 and nutrient transport in humans.
Totipotent
Capable of developing into all different cell types.
A zygote is totipotent plus the next three cell divisions.
Pluripotent
Capable of developing into many cell types, not extraembryonic tissues.
Stem cells
Implantation
Occurs in the endomtrium of the uterus and occurs before end of the first week.
The blastocyst is what adheres to the endometrium.
The blastocyst is what adheres to the endometrium.
Blastocyst is the mammalian version of a blastula.
The mammalian egg is…
Smaller compared to birds and reptiles. A human embryo is not in a shell, nor nourished by yolk, but does have a yolk sac. This sac plays a role in forming the digestive tract.
The umbilical cord will connect
the human embryo to parts of the yolk sac, allantois, and amnion. The umbilical cord is high vascular.
The chorion develops around
The embryo and secretes the human chorionic gonadotropin hormone responsible for maintaining the corpus luteum.
The corpus luteum secretes
Proteserone during the first trimester.
After the first trimester
The placenta takes over to produce progesterone and estrogen(steroid hormones).
1st Trimester
Most growth and differentiation, most sensitive to radio and drug toxicity. Main period for organogenesis. After 8 weeks the embryo is a fetus.
Outer layer of the blastocyst
Trophoblast, grows within the endometrium to form the placenta.
Viviparous development
Young are born alive after being nourished in the uterus from the placenta.
Oviparous
Young hatch from eggs laid outside the mother
2nd trimester
All major organs formed. Corpus luteum now deteriorates as levels of hCG decrease since placenta now takes over progesterone and estrogen supply.
3rd Trimester
8 months the fetus can survive on its own.
What is a homeotic gene?
Regulatory genes responsible for the placement and spatial organization of body parts in animals, plants and fungi.
