Exam #1 Flashcards
When do primordial sperm cells (spermatogonia) become 1˚ spermatocytes, i.e. when does spermatogenesis begin? Were are they located?
At puberty; seminiferous tubules of the testes.
When do oogonia proliferate and transform into 1˚ oocytes, i.e when does oogenesis begin?
Early in fetal life (in contrast to spermatogenesis in males, which begins at puberty).
Describe the state of oogonia in females up to the point of puberty.
Oogenesis BEGINS during the fetal period, but is not completed until after puberty. All primary oocytes have completed PROPHASE I (of meiosis), but are arrested in this phase (prophase I) UNTIL PUBERTY.
p.16
What will be the karyotype of affected spermatids if abnormal gametogenesis occurs during Meiosis I (2)?
- ) Two spermatids with 24, XY.
2. ) And TWO spermatids with 22, 0.
Oogenesis is not complete until when?
FERTILIZATION
Gametogenesis results in ______(#) of (haploid or diploid) cell.
Results in FOUR HAPLOID cells.
At ______, spermatogonia are signaled to begin maturation. What is this process called?
At puberty, spermatogonia begin SPERMATOGENESIS.
Monosomic nondisjunction often results in _______.
Termination of the embryo.
What must be shed from the blastocyst before implantation can occur?
Zona Pellucida
What metamorphosis do the spermatids undergo during spermiogenesis? (3)
- ) Nucleus condenses
- ) Acrosome forms
- ) Most of cytoplasm is shed
How long does spermiogenesis require, and how long does it persists in males?
Requires ≈ 2 months; normally continues throughout the reproductive life of a male. p.15
Where are the new sperm stored?
The epididymis.
When and how do oogonia become primary oocytes?
During early fetal life, oogonia proliferate by MITOSIS and enlarge to form primary oocytes.
Oocytes remain in _____ until puberty.
Prophase
By birth, all 1˚ oocytes have completed the ______ of ______.
prophase of the first meiotic division.
Shortly before ovulation, a 1˚ oocyte ______. How does this stage differ from the corresponding stage in spermatogenesis?
Completes the first meiotic division.
The division of cytoplasm is unequal, and the 2˚ oocyte receives almost all of the cytoplasm, whereas the FIRST POLAR BODY RECEIVES VERY LITTLE, causing it to degenerate after a short time.
At ovulation, the nucleus of the 2˚ oocyte _______, but only progresses to _______.
the 2nd meiotic division, but only progresses to METAPHASE.
What completes the second meiotic division of the 2˚ oocyte?
Fertilization.
Nondisjunction occurs during _____ when _______.
At what time is it likely that the cause of this chromosomal event occurred?
- Gametogenesis when homologous chromosomes fail to separate.
- Meiosis I of oogenesis.
Development of an ovarian follicle is characterized by (4 things):
Growth and differentiation of a primary oocyte.
• Proliferation of follicular cells.
• Formation of the zona pellucida.
• Development of a connective tissue capsule
surrounding the follicle – the theca folliculi.
What triggers ovulation?
LH surge in maternal circulation; ovulation follows within 24 hours of this surge.
Before fertilization, the secondary oocyte is where?
The uterine tube.
Each chromosome in male and female pronuclei is made up of only _______.
One chromatid.
What pre-embryonic group of cells are destined to become the placenta?
Trophoblast
What pre-embryonic group of cells form the primordium of the embryo?
Embryoblast
How many days post-fertilization does a blastocyst form?
Where is it located?
≈ 4 days
In the uterine cavity
What lets the blastocyst rapidly grow in size?
Degeneration of the zona pellucida
What prevents the blastocyst from sticking to the walls of the uterus prior to implantation?
The zona pellucida
During implantation, which layer of cells begins to invade the endometrium?
Syncytiotrophoblast
The zona pellucida is shed by day ______.
≈ 5-6
Implantation begin at week ______, and ends by week ______.
Begins week 1, ends by week 2. Lecture says will be fully implanted by DAY 10
Which cells produce the hCG that is detected for pregnancy tests?
Syncytiotrophoblasts
The endometrium is in the _____ phase of menstruation at the time of implantation.
Secretory
What structure turns into the primary yolk sac (aka 1˚ umbilical vessel)? What turns it into the primary yolk sac?
Blastocele; endoderm proliferating and closing it off.
In between which cell layers does the amniotic cavity form?
Which cells form the amnion?
- Embryoblast/Ectoderm and trophoblast.
- Amniogenic cells from the EPIBLAST organize and enclose the blastocele. The thin membrane they form is called the amnion.
After which day does fetal and maternal circulation become united? Which event causes this?
≈ Day 12; when adjacent STB networks fuse.
What are the contents of the mature umbilical cord? (5)
- Two umbilical arteries
- One umbilical vein (L umbilical vein)
- Wharton’s Jelly
- Remains of allantoic diverticulum
- Remains of vitellointestinal duct (remnant of yolk sac)
- p.71 Clinical
Give the timeline (in weeks) that each stage of the chorionic villus appears. What happens at each stage?
Primary villus: Week 2
-CTB surrounded by STB invades trabeculae.
Secondary villus: Early week 3
-Extraembryonic somatopleuric mesoderm (deep to CTB) invades each villus.
Tertiary villus: End of week 3
-Blood vessels develop in the mesoderm of the 2˚ villi.
p.65 Clinical
What are the four embryonic components of the diaphragm and what do they become?
- ) Septum Transversum – Central tendon
- ) Pleuroperitoneal membranes – Posterolateral/Dorsolateral aspect of diaphragm .
- ) Dorsal mesentery of the esophagus – Crura of diaphragm.
- ) Lateral body walls, i.e. migrating myoblasts – Muscle of diaphragm.
What defect causes CDH?
Pleuroperitoneal membrane failure to form or fuse with the other three parts of the diaphragm (large opening in the posterolateral aspect of diaphragm that intestines come out through).
Concerning neural tube closure, where does closure begin? Which closes first: Rostal or caudal neuropore?
Closure begins at the midline –Rostral closes before caudal.
By week _____, the intraembryonic coelem becomes 3 cavities, what are they?
Week 8: Pericardial, pleural, and peritoneal.
The ____ is the maternal contribution to the placenta.
Decidua basalis.
Which somites go on to form the diaphragm? Innervation?
Cervical somites 3-5 (Phrenic nerve)
What causes the apparent descent of the diaphragm during development?
Rapid dorsal growth.
What must happen to sperm before fertilization, describe? What are the steps to fertilization (6)? Briefly state what happens at each stage.
Sperm must undergo CAPACITATION – glycoprotein and plasma membrane coat in the acrosomal region is removed.
- ) Penetration of the corona radiata (ONLY capacitated sperm).
- ) Penetration of zona pellucida (Acrosomal rxn of sperm, then zona reaction makes it impermeable).
- ) Fusion of sperm and oocyte cell membrane (head and tail enter, plasma membrane and mitochondrial sheath left behind
- ) Completion of 2nd meiotic division (oocyte), and formation of female pronucleus (second polar body produced).
- ) Formation of male pronucleus (gametes change from ‘n’ to ‘2n’ –two chromatids each).
- ) Zygote formation: 2n zygote from ootid (female pronuclei).
a. ) 24, XX + 23, XY = ? (what condition, examples?)
- Where/when is this likely to occur?
b. ) 23, XX + 22, XY = ?
a. ) Trisomy (most likely from the mother during meiosis II of oogenesis…if mother >38y/o, chances of occuring in Meiosis I increase). T21 = Down, T18 = Edwards, T13 = Patau.
b. ) Monosomy ≈ Death of fetus.
Describe Klinefelter Syndrome
(XXY): The primary feature issterility.Often symptoms may be subtle and many people do not realize they are affected. Sometimes symptoms are more prominent and may include weaker muscles, greater height, poorcoordination, less body hair, smallergenitals,breast growth, and less interest in sex. Often it is only atpubertythat these symptoms are noticed.
