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What type of division involves replication of cells without reduction of number of chromosome number?
What type of division involves reduction of chromosome number?
What is the normal complement of chromosomes in a cell?
What happens in the S phase of mitosis?
- Duplication of DNA.
- (Still same # of chromosomes, just sister chromatids - 4d)
In what phase of mitosis is a chromosome first visible microscopically?
In what phase of mitosis do sister chromatids separate?
What phase of mitosis involves the constriction furrow?
What is the chromosome # in the stage that involves the contriction furrow?
- (Remember that it is 2N all throughout mitosis)
Why is prophase longer in meiosis than mitosis?
To allow homologous chromosomes to pair
What occurs in prophase of meisosi that involves genetic recombination?
How is metaphase I different in meisos than in mitosis?
- It is reduction division (2N -> N).
- Chromosomes are pulled apart.
After meiosis I how much DNA is present? How many chromosomes?
What is pulled apart in metaphase II?
- Sister chromatids (similar in mitosis).
- Differentiate this from what happens in metaphase I
How many oocytes are developed from each oogonia?
How many spermatids are developed from each spermatagonia?
What is a polar body?
- It is the result of unequal division of cytoplasm in oogenesis.
- It undergoes apoptosis and degenerates.
What makes up the head of a spermatozoa?
What cellular compartment is derived from the acrosomal layer that is draped over the head of the spermatozoa?
What is the function of the acrosomal layer of the head of a spermatozoa?
It provides enzymes necessary for fertilization
Why is mitochondrial inheritance maternally derived?
The mitochondra in the sperm are located in the tail of spermatid and degenerate
What is the acellular membrane around oocyte that persists until fertilization occurs?
Collectively, what are the cells around the oocyte referred to as?
At what point of meisos is a primary oocyte arrested?
Diplotene of prophase I, until puberty occurs. Then it completes meisos I and a secondary oocyte is ovulated each month.
At what point of meiosis is a secondary oocyte arrested?
Metaphase of meiosis II until fertilization occurs. Then it forms an embryo (thus there is really no such thing as a mature ovum)
What portion of the oviduct does fertilization occur in?
Distal 1/3 of oviduct
What is a sperm covered in that prevents fertilization?
What is the process of removal of protein coat covering a sperm?
- It typically takes 7 hours.
What must occur in order for sperm to penetrate the zona pellucid?
- Acrosome reaction
- Enzymes are released and the plamsa membrane over the acrosome is dissolved. A hole is made in the zona pellucid to allow passage of the sperm.
What causes the oocyte, after penetration by the sperm, to prevent other sperm from entering? (polyspermy)
What are the three consequences of fertilization?
- 1) Restoration of chromosome #
- 2) Sex deterination
- 3) Initiation of cleavage
When cells undergo compaction and reach the 16 cell stage, what is the embryo referred to as?
At what stage does the embryo arrive in the uterus?
As a morula
What is the embryo called when fluid begins to leak through the zona pellucid and form a cavity?
- Blastocyst sticks to the uterine wall which has been prepared via hormonal changes.
What are the two laters of the bilaminar disk?
- 1) Epiblast
- 2) Hypoblast
- (Week 2 has two layers)
What does the outer cell mass form?
What layer of the trophoblast invates the endometrium to get nutrients and blood?
What produces beta-hCG? When can it be detected?
- 8-11 days after fertilization
What is a method to detect pregnancies earlier?
- Early Pregnancy Factor (EPF)
- This is related to an immunologic factor protecting the fetus from the mother's immune system.
What is a pregnancy that occurs in the wrong place?
- Ectopic pregnancy
- Previous pelvic infections can cause these by forming adhesions
Where do most ectopic pregnancys occur?
Distal portion of the oviduct.
What is an ETP called in the cervical canal?
What is the most likely place for an ETP in the peritoneal cavity?
Rectouterinef pouch (pouch of douglas)
What forms the primary yolk sac?
Migrating cells from hypoblast
What fills the space between primary yolk sac and cytotrophoblast?
- Extraembryonic somatic mesoderm
- (This also forms the secondary yolk sac due to its migration pattern)
What is extraembryonic mesoderm called around the yolk sac?
Splanchnic extraembryonic mesoderm
What is the fetal part of the placenta derived from?
- Extraembryonic mesoderm
What is the maternal part of the placenta derived from?
- Decidua basalis
- (lining of the uterus)
During which week does gastrulation occur?
- Week 3
- (Remember - 3 layers, ectoderm, endoderm, mesoderm in 3rd week)
What is the area in which the epiblast and hypoblast are tightly ajoined?
- Buccopharyngeal membrane
- (future site of mouth - prochordal plate)
What do cells that travle through through the primitive pit toward buccopharyngeal membrane form?
What cells migrate in the bilaminar disk to form endoderm and mesoderm?
Epiblast cells migrate downward to form the endoderm and mesoderm. The epiblast cells that remain in the epiblast form the ectoderm.
What connects the primitive yolk sac?
What is the remnant of the notochord in the intervetebral disk?
What is an abnormal remnant of the primitive streak?
What forms the epiblast over the notochord?
- (neural crest branches off from this in development)
What forms from general ectoderm?
- Epidermis of skin
- Outer covering of teeth
- Sensory part of inner ear
- Pituitary gland
- Mammary gland
- Lower Anal Canal
What forms the neurectoderm?
- - Think CNS and retina -
- CN II (optic nerve)
- Neurohypophysis (portion of pituitary gland)
What forms from neural crest?
- - Nervous system not from CNS (ANS) -
- C Cells
- Aortiocopulmonary septum
- Adrenal medulla
- Schwann cells
What forms from endoderm?
- Lining of GI tract and respiratory tract
- Bladder, Rectum
- Pharyngeal Pouches
- Parenchyma of liver, pancreas, sublingual, submandibular, thyroid gland
What forms from mesoderm?
- Connective tissue of:
- - kidney
- - liver
- - spleen
- - cardiovascular
- - gonads
* The developing embryo reaches the uterus as a _______?
* Before sperm can fertilize an egg, they must remain in the female reproductive tract for approximately 7 hours during which they undergo a process know as _______.
* When a sperm is taken inside the egg, the egg plasma membrane is rendered impenetrable to any other sperm. This block to polyspermy is caused by _______.
The release of lysosomal enzymes by cortical granules
* Gastrulation causes the establisment of what germ layers?
* Cells destined to become the notochord migrate through the ______.
* The loss of what structure from the embryo permits implantation to begin?
* Indicate the states of chromosome number and DNA content in division of products after the first meiotic division.
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