Chapter 3.1 Flashcards
What is the acrosomal apparatus
- it is a tubelike structure of the sperm
- >used by the first sperm that comes into contact with the secondary oocyte
What happens after penetration of the secondary oocyte ? Note some type of reaction occurs
- a cortical reaction occurs
- > release of calcium ions
- > depolarizes the ovum
What is the point of depolarizing the ovum?
- depolarization prevents fertilization of ovum by multiple sperm cells
- increases calcium concentration increases the metabolic rate of the newly formed zygote
What is the depolarized and impenetrable membrane of the secondary oocyte referred to as?
-it is referred to as the fertilization membrane
How do conjoined twins come about?
-if division of monozygotic twins are incomplete
What is the defining characteristic of a zygote
-its unicellularity
What happens during cleavage? What ratio increases as more cleavages occur?
- first cleavage creates an embryo
- several rounds of mitosis keep occuring
- > size of the embryo doesn’t change
- > but there is division into smaller cells
- more divisions= greater nuclear:cytoplasmic ratio/ surface area to volume ratio
- > increased area for gas and nutrient exchange relative to volume
What are the two types of cleavage
1) Indeterminate cleavage
- >results in cells that can still develop into complete organisms
2) Determinate cleavage
- >results in cells with their fates determined
- >these cells are committed to differentiating into a certain type of cell
What does it mean when referring to morula?
- after several divisions of the zygote
- >it becomes a morula
Describe the process of blastulation. What forms?
- the morula undergoes blastulation
- > forms the blastula
- blastula is a hollow ball of cells
- > with an inner fluid cavity known as the blastocoel
What is the mammalian blastula known as? What two types of cells does it contain? Describe the functions of these two cell types
- it is known as the blastocyst
- > contains trophoblast cells and inner cell mass cells
Trophoblast cells
- > surrounds the blastocoel
- > gives rise to the chorion/placenta
Inner cell mass
- > protrudes into the blastocoel
- > gives rise to the organism itself
What is the process of implantation
- it is where the blastula moves through the fallopian tube
- >implants itself in the uterus
Where do chorionic villi originate from? Describe their structure. What do they later develop into? What is the purpose of this new developed structure
-they originate from trophoblasts
- they are microscopic finger like projections
- > penetrate the endometrium
- the chorionic villi later develop into placenta
- > they then support maternal-fetal gas exchange
What is the embryo connected to the placenta by. Describe the structure of this connection
-umbilical cord connects an embryo to a placenta
- it has two arteries and one vein
- > vein carries freshly oxygenated blood from placenta to embryo
- > arteries carry deoxygenated blood and waste to the placenta for exchange
What two structures does the umbilical cord form from
-it forms from the yolk sac and the allantois
What is the function of the yolk sac
- until placenta is functional
- > embryo is supported by the yolk sac
-early blood cell development also occurs in the yolk sac
What is the function of the allantois
-involved in early fluid exchange between the yolk sac and embryo
What is the function of the amnion? What structure does the amnion surround? What structure surrounds the amnion
- amnion is a thin tough membrane filled with amniotic fluid
- > it surrounds the allantois
- serves as a shock absorber during pregnancy
- note the chorion surrounds the amnion as well for extra support
What is the function of the ectoderm? Where is its location
- the outermost layer
- > gives rise to epidermis, hair, nails, epithelia of the noce, mouth and lower anal canal
- > but most importantly it gives rise to the NERVOUS SYSTEM
What is the function of the mesoderm? Where is it located?
- middle layer
- > gives rise to the musculoskeletal, circulatory and most of the excretory systems
- > also the gonads
- so anything to do with muscular and connective tissue layers
- > eg; the muscular and connective tissue layers of the digestive system
What is the function of the endoderm?
- it forms the epithelial linings of the digestive and respiratory tracts
- > including the lungs
-pancreas, thyroid, distal urinary tracts, bladder, as well as parts of the liver are derived from the endoderm
What does the process of neurulation refer to?
- it occurs after the three germ layers are formed
- >it describes the development of the nervous system
What part in the development of the nervous system gives rise to the CNS? What part gives rise to the PNS? What covers the rudimentary nervous system created by the neural tube and the neural crest cells?
- neural folds grow toward one another
- > until they fuse into the neural tube
- the neural tube gives rise to the CNS
- neural crest cells migrate outward to form the PNS
- the rudimentary nervous system is covered by the ectoderm cell
- > they migrate over the neural tube and neural crest cells
What are teratogens? Give examples
- teratogens are substances that interfere with development
- > causing defects or even death in a developing embryo
-eg; alcohol, prescription drugs, viruses, bascteria and environmental chemicals
