Chapter 3.1 Flashcards
What happens to the secondary oocyte following ovulation?
The secondary oocyte will leave the ovary and enter the abdominal cavity. It will then be pushed to the fallopian tube where it can potentially be fertilized.
What is the cortical reaction and how does it affect the ovum?
When a sperm penetrates the cell membrane of an ovum, a flood of calcium ions occurs and the ovum’s cell membrane depolarizes. This serves 2 purposes.
- The depolarized cell membrane is impenetrable to more sperm, preventing multiple sperm from fertilizing one egg.
- The increased calcium concentration increases the metabolic rate of the newly formed zygote, helping it to grow and survive.
What is the fertilization membrane?
The fertilization membrane is the depolarized and impenentrable membrane of a zygote following the cortical reaction.
What are the two types of twins?
- Dizgotic, or Fraternal
- Monozygotic, or Identical
How do dizygotic twins come to be?
Dizygotic twins form from the fertilization of two different eggs that were released in one ovulatory cycle by two different sperm. Both of these zygotes will implant in the uterine wall and be carried to full term.
How do monozygotic twins come to be?
Monozygotic twins occur when a single fertilized ovum (zygote) splits into two without differentiating into other tissues. Because the genetic material in daughter cells is identical in mitosis, these two twins will carry the same genetic information and share appearance.
What is cleavage? (in embryonic development)
Cleavage is the series of rapid mitotic divisions undergone by a newly fertilized zygote.
These cleavages are distinct because they do not result in an increase of the size of the organism, they just result in more cells.
This increases surface area to volume ratio which increases area for nutrition and gas exchange
What are the two types of cleavage?
- Intermediate
- Determinate
What is indeterminate cleavage?
Intermediate cleavage results in cells that can still develop into complete organisms. This is actually what happens in monozygotic twins. At some point, the embryo undergoes an indeterminate cleavage that results in another organism forming in addition to the original.
What is Determinate cleavage?
Determinate cleavage results in cells with fates that are determined. That is to say, they are already committed to differentiating into a certain type of cell.
By what factor does the number of cells increase after each cleavage?
2x
What is a morula
Morula refers to the solid mass of cells that culminates from several divisions of the zygote. It’s name comes from the latin word for mulberry, which is what the morula looks like.
What is blastulation?
Blastulation is the name for the transformation of the morula into the blastula.
What is a blastula?
A blastula is a hollow ball of cells with a fluid filled inner cavity know as a blastocoel.
How is a blastocsyt distinct from a blastula?
Blastocyst is just the name for a mammalian blastula.
What are the two notweorthy cell groups in a blastocyst?
- The trophoblast cells
- The inner cell mass
What is the function of the trophoblast cells?
The trophoblast cells surround the blastocoel and give rise to the chorion and later the placenta.
What is the function of the inner cell mass?
The inner cell mass is the group of cells that will give rise to the organism being born.
Describe the path of a fertilized egg, starting from the ovary and ending with implantation.
- From the supply with which females are born, a primary oocyte will be allowed to develop into a secondary oocyte.
- The secondary oocyte will burst forth from the follicle, leave the ovary, and enter the abdominal cavity.
- The secondary oocyte is taken up by the Fallopian tube with the help of cilia.
- The secondary oocyte is fertilized by sperm at some point in the fallopian tube.
- After fertilization, the zygote continues its path through the fallopian tube.
- As the zygote travels through the fallopian tube, it undergoes blastulation, eventually forming a blastocyst (blastula).
- The blastocyst implants in the thickened endometrium and begins secreting hCG, a hormone that mimics LH.
What is the chorion?
The chorion is an extraembryonic membrane that forms from the trophoblast cells and develops into the placenta.
What is the umbilical cord?
The umbilical cord is a thick cord comprised of two arteries and one vein encased in a gelatinous substance. The umbilical vein carries oxygen and nutrient rich blood to the embryo from the placenta and the umbilic arteries carry deoxygenated blood from the embryo to the placenta.
NOTE: This is opposite of the normal situation, which is arteries carrying oxygenated blood and veins carrying deoxygenated blood.
What is the yolk sac?
The yolk sac is a temporary structure from which the embryo draws nutrients and forms red blood cells. The yolk sac supports the embryo until the umbilical cord and the placenta are fully formed and can take over supplying the embryo.
What is the amnion?
The amnion is a thin, tough membrane which produces amniotic fluid. It serves as a shock absorber to protect the developing fetus.
What is gastrulation?
Gastrulation is the term used to refer to the
inward folding of the blastula to create a layered structure with a prominent invagination known as a gastrula.
What 5 important structures are developed during gastrulation?
During gastrulation, the three primary germ layers are developed as well as the archenteron and the blastopore.
What are the three germ layers and what is their collective function?
The three germ layers are the Ectoderm, the Mesoderm, and the Endoderm. These three layers provide the base for the development of all of the tissues in the human body. Each layer will develop into its own specific tissues.
What is the archenteron?
The archenteron is the name of the invagination that forms during gastrulation.
What is the blastopore?
The blastopore is the name for the mouth of the opening in the gastrula known as the archenteron.
How deep is the Ectoderm in the Gastrula and what tissues are derived from it?
The Ectoderm is the outermost germ layer. It develops into skin (epidermis), hair, nails, the lens of the eye, the entire nervous system, the inner ear, the adrenal medulla, pituitary gland, and the epithelial linings of the mouth and anus.
MNEMONIC: Ectoderm = “Attracto” derm. We are attracted to good skin, good brain, and pretty eyes.
How deep is the Mesoderm in the Gastrula and what tissues are derived from it?
The Mesoderm is in between the outermost Ectoderm and the innermost Endoderm. The Mesoderm develops into the musculoskeletal system, the circulatory system, the heart, the spleen, the kidney, bone, connective tissue layers of the digestive and respiratory system, the gonads, and the adrenal cortex.
MNEMONIC: Mesoderm = “means” oderm. These tissues provide us the means to move around (musculoskeletal), the means to move things within our body (circulatory system), the means to get rid of things (kidneys), and the means to have sex (the gonads).
How deep is the Endoderm in the gastrula and what tissues are derived from it?
The Endoderm is the innermost of the three germ layers. It develops into the epitelial lining of the digestive tract (except for the mouth and the anus) and the lungs. It also develops into the pancreas, thyroid, bladder, distal urinary tracts, and part of the liver.
MNEMONIC: Endoderm = linings of the “endernal” organs (digestive and respiratory tract) and the accessory organs attached to these systems (such as the pancreas, thyroid, bladder, and liver.)
Every single cell in the human body contains the ____ DNA
same
If every single cell in the human body contains the same DNA, and DNA is the blueprint for the development of the cell, how is it that cells can be so different from one another?
Certain cells will express different parts of the genome while not expressing others. For example, heart cells will express the heart related segments of our DNA, where as kidney cells will express the kidney related segments of our DNA.
What is selective transcription?
Selective transcription is when a cell develops a specialized function by only transcribing certain parts of the genome.
What is induction?
Induction is the ability of one group of cells to influence the development of other nearby cells through the use of inducers.
What are inducers?
Inducers are the chemical signals that are used by cells to cause induction.
What are the two main layers of the adrenal gland and from what germ layers are they derived?
- The Adrenal Cortex, derived from the Mesoderm
- The Adrenal Medulla, derived from the Ectoderm
What is Neurulation?
Neurlation is the development of the internal nervous system from the external ectoderm.
What is the notochord and what is its function in Neurulation?
The notochord is a long rod of mesodermal cells. During Neurlation, the notochord induces a segment of the ectoderm to slide inward. This establishes the neural folds and the neural groove.
As the neural groove deepens, what happens to the neural folds?
As the neural groove deepens, the neural folds come closer to one another. They will continue to come closer to one another until they meet, forming the neural tube.
What are the neural crest cells and into what will they develop?
The neural crest cells are cells at the tip of both of the neural folds. These cells will migrate from the neural folds and develop into the entirety of the peripheral nervous system (sensory ganglia, autonomic ganglia, adrenal medulla, schwann cells) as well as specific cell types in other tissues (calcitonin producing cells of the thyroid, melanocytes in the skin, etc.) Cells derived from ectoderm
