Seminar
Presentation on Oogenesis
Process Of Oogenesis
Multiplication Phase
Growth Phase
Maturation Phase
Ovulation
Hormones in Oogenesis
Significance of Oogenesis
References
In testis, the immature male germ cell (spermatogonia ) produce sperms by spermatogenesis
The spermatogonia ( sing. Spermatogonium ) present on the inside of seminiferous tubules multiply by mitotic division and increase in numbers
Each spermatogonium is diploid and contains 46 chromosomes
Some of the spermatogonia called primary spermatocytes periodically undergo meiosis.A primary spermatocyte completes the first meiotic division (reduction division) leading to formation of two equal, haploid cells called secondary spermatocyte, which have only 23 chromosomes
The secondary spermatocyte undergo the second meiotic division to produce four equal, haploid spermatids
In testis, the immature male germ cell (spermatogonia ) produce sperms by spermatogenesis
The spermatogonia ( sing. Spermatogonium ) present on the inside of seminiferous tubules multiply by mitotic division and increase in numbers
Each spermatogonium is diploid and contains 46 chromosomes
Some of the spermatogonia called primary spermatocytes periodically undergo meiosis.A primary spermatocyte completes the first meiotic division (reduction division) leading to formation of two equal, haploid cells called secondary spermatocyte, which have only 23 chromosomes
The secondary spermatocyte undergo the second meiotic division to produce four equal, haploid spermatids
Polyspermy describes an egg that has been fertilized by more than one sperm. Diploid organisms normally contain two copies of each chromosome, one from each parent. The cell resulting from polyspermy
The first issue that an egg and a sperm of any organism type face in successfully producing an embryo is the possibility of polyspermy. Polyspermy is the fertilization of an egg by multiple sperm, and the results of such unions are lethal.
If multiple sperm fertilize an egg, the embryo inherits multiple paternal centrioles. This causes competition for extra chromosomes and results in the disruption of the creation of the cleavage furrow, thus causing the zygote to die. As an important model organism in the study of fertilization and embryonic development, polyspermy in sea urchins has been studied in detail. The sea urchin’s methods of polyspermy prevention have been broken down into two main pathways. These two primary pathways are known as the fast block and the slow block to polyspermy
After the sperm’s receptors come into contact with the egg’s jelly layer and the acrosomal enzymes are released and break down the jelly layer, the sperm head comes into contact with the vitelline and plasma membranes of the egg. When the two plasma membranes contact one another, signals in the egg are initiated.
First, Na+ channels in the egg open, allowing Na+ to flood into the egg. This causes a depolarization of the egg from it’s normal resting potential of -70 mV.
While depolarization is occurring, the remainder of the jelly layer is dissolving. With the dissolution of the jelly layer and the depolarization of the plasma membrane, the first block to preventing fertilization by multiple sperm is put into place.
These two simple changes are part of the first block to polyspermy, known as the fast block. Within 1/10th of a second of contact, the fast block t
presentation on oogenesis of fertilisation process full details about it u will never find it anywhere else have full details about the ovum formation polar bodies and everything . so explore here
How 3 germ layers are formed in Chick that are endoderm, mesoderm and ectoderm.As Chick are polylecithal so cell movements are somewhat restricted and gastrulation is modified as compared to frog.
AnswerOogenesis is the process by which ovum mother cells or oogo.pdfarasanlethers
Answer:
Oogenesis is the process by which ovum mother cells or oogonia gives rise to mature ovum- the
female gametes. The process takes place in the outermost layer- the germinal epithelium of the
ovary.
Meiotic Events in oogenesis:
Initially before birth, the oogonium undergoes mitotic divisions so as to increase its number. This
process takes place during the embryonic growth phase. No further addition to this number takes
place after birth. In the human embryo, the thousand or so oogonia divide rapidly from the
second to the seventh month of gestation to form roughly 7 million germ cells. After the seventh
month though, there is a sharp decline in the number of these newly formed cells. These
remaining cells are the ones entering the reductional division of meiosis (meiosis-1). These cells
enters into meiosis-1 but they are unable to advance through Prophase-1 of meiosis. These cells
are arrested in the diplotene sub-stage of Prophase-1 and they are maintained at this stage until
puberty. These cells are now known as primary oocytes. Even the primary oocytes continue to
die during this phase. Roughly only about 400 oocytes mature during the reproductive life of a
female periodically. At the onset of puberty, specific hormonal cues re-initiate the process of
meiosis.
During adolescence, the GnRH or gonadotropin releasing hormones released from the
hypothalamus signals the anterior pituitary to release hormones like LH & FSH which lifts the
cell cycle arrest in these cells and assists them in resuming meiosis. The primary oocytes
completes meiosis-1 and gives rise to a tiny polar body and another larger secondary oocyte with
greater content of cytoplasm ( unequal cell division). In some organisms , the polar bodies may
again divide to form 2 polar bodies while it dies off in case of humans. The secondary oocyte
thus produced advances through Meiosis-2 ( equational division) but halts at meiosis-2. The
secondary oocyte is released from the follicle and it travels towards the fallopian tube. The
immature secondary oocyte can re-enter cell cycle and complete the remaining sub-stages of
meiosis-2 only if union with a sperm takes place. The secondary oocyte progresses through
meiosis-2 giving rise to another polar body and a female pro-nucleus which unites with the
sperm and gives rise to the zygote or the fertilized egg. Thus begins the process of embryonic
development.
Developmental process in oogenesis:
Oogonia are formed from the primoridial germ cells of the ovary by mitotic cell division. By
growth & maturation oogonia increase in size and become primary oocytes. During this phase,
synthesis of food and factors required for further differentiation are synthesized. During the
growth phase, the primary oocytes gets surrounded by specialized cells of the ovary known as
follicle cells. Once they are fully formed, cavities are formed and these gets filled with their own
secretion. At this stage, it is known as Graafian follicle. Oocyte collects .
Polyspermy describes an egg that has been fertilized by more than one sperm. Diploid organisms normally contain two copies of each chromosome, one from each parent. The cell resulting from polyspermy
The first issue that an egg and a sperm of any organism type face in successfully producing an embryo is the possibility of polyspermy. Polyspermy is the fertilization of an egg by multiple sperm, and the results of such unions are lethal.
If multiple sperm fertilize an egg, the embryo inherits multiple paternal centrioles. This causes competition for extra chromosomes and results in the disruption of the creation of the cleavage furrow, thus causing the zygote to die. As an important model organism in the study of fertilization and embryonic development, polyspermy in sea urchins has been studied in detail. The sea urchin’s methods of polyspermy prevention have been broken down into two main pathways. These two primary pathways are known as the fast block and the slow block to polyspermy
After the sperm’s receptors come into contact with the egg’s jelly layer and the acrosomal enzymes are released and break down the jelly layer, the sperm head comes into contact with the vitelline and plasma membranes of the egg. When the two plasma membranes contact one another, signals in the egg are initiated.
First, Na+ channels in the egg open, allowing Na+ to flood into the egg. This causes a depolarization of the egg from it’s normal resting potential of -70 mV.
While depolarization is occurring, the remainder of the jelly layer is dissolving. With the dissolution of the jelly layer and the depolarization of the plasma membrane, the first block to preventing fertilization by multiple sperm is put into place.
These two simple changes are part of the first block to polyspermy, known as the fast block. Within 1/10th of a second of contact, the fast block t
presentation on oogenesis of fertilisation process full details about it u will never find it anywhere else have full details about the ovum formation polar bodies and everything . so explore here
How 3 germ layers are formed in Chick that are endoderm, mesoderm and ectoderm.As Chick are polylecithal so cell movements are somewhat restricted and gastrulation is modified as compared to frog.
AnswerOogenesis is the process by which ovum mother cells or oogo.pdfarasanlethers
Answer:
Oogenesis is the process by which ovum mother cells or oogonia gives rise to mature ovum- the
female gametes. The process takes place in the outermost layer- the germinal epithelium of the
ovary.
Meiotic Events in oogenesis:
Initially before birth, the oogonium undergoes mitotic divisions so as to increase its number. This
process takes place during the embryonic growth phase. No further addition to this number takes
place after birth. In the human embryo, the thousand or so oogonia divide rapidly from the
second to the seventh month of gestation to form roughly 7 million germ cells. After the seventh
month though, there is a sharp decline in the number of these newly formed cells. These
remaining cells are the ones entering the reductional division of meiosis (meiosis-1). These cells
enters into meiosis-1 but they are unable to advance through Prophase-1 of meiosis. These cells
are arrested in the diplotene sub-stage of Prophase-1 and they are maintained at this stage until
puberty. These cells are now known as primary oocytes. Even the primary oocytes continue to
die during this phase. Roughly only about 400 oocytes mature during the reproductive life of a
female periodically. At the onset of puberty, specific hormonal cues re-initiate the process of
meiosis.
During adolescence, the GnRH or gonadotropin releasing hormones released from the
hypothalamus signals the anterior pituitary to release hormones like LH & FSH which lifts the
cell cycle arrest in these cells and assists them in resuming meiosis. The primary oocytes
completes meiosis-1 and gives rise to a tiny polar body and another larger secondary oocyte with
greater content of cytoplasm ( unequal cell division). In some organisms , the polar bodies may
again divide to form 2 polar bodies while it dies off in case of humans. The secondary oocyte
thus produced advances through Meiosis-2 ( equational division) but halts at meiosis-2. The
secondary oocyte is released from the follicle and it travels towards the fallopian tube. The
immature secondary oocyte can re-enter cell cycle and complete the remaining sub-stages of
meiosis-2 only if union with a sperm takes place. The secondary oocyte progresses through
meiosis-2 giving rise to another polar body and a female pro-nucleus which unites with the
sperm and gives rise to the zygote or the fertilized egg. Thus begins the process of embryonic
development.
Developmental process in oogenesis:
Oogonia are formed from the primoridial germ cells of the ovary by mitotic cell division. By
growth & maturation oogonia increase in size and become primary oocytes. During this phase,
synthesis of food and factors required for further differentiation are synthesized. During the
growth phase, the primary oocytes gets surrounded by specialized cells of the ovary known as
follicle cells. Once they are fully formed, cavities are formed and these gets filled with their own
secretion. At this stage, it is known as Graafian follicle. Oocyte collects .
This topic contains Gametogenesis- oogenesis and spermatogenesis, ovulation, fertilization, development of fertilized ovum/ zygote, implantation, development of decidua, chorion and chorionic villi, development of inner cell mass.
This topic includes menstruation:- its definition, anatomical aspects- follicular growth and atresia, germ cells, premodial follicle; menstrual cycle/ ovarian cycle:- definition, phases- recruitment of groups of follicles (premature phase), selection of dominant follicle and its maturation, ovulation, follicular atresia; Endometrial cycle:- division of endometrium- basal zone, functional zone and its phases- stage of regeneration, stage of proliferation, secretory phase, menstrual phase, mechanism of menstrual bleeding, role of prostaglandins, hormones in relation to ovarian and menstrual cycle, ovulation, luteal-follicular shift, menstrual symptoms, menstrual hygiene, anovular menstruation, artificial postponement; cervical cycle, vaginal cycle and general changes in follicular and luteal phase.
permatogenesis and oogenesis are the processes of formation of male and female gametes. Spermatogenesis leads to the formation of sperms, whereas oogenesis helps in the formation of ova. The fertilization of sperm and ova leads to the formation of a zygote which further develops into an embryo
Giving overview of human embryonic development including spermatogenesis, oogenesis, fertilization, gastrulation, cleavage, extraembryonic layers and pregnancy
Oogenesis in amphibians, PowerPoint presentationmahnoorbaig11301
Stages of oogenesis:
Oogonia proliferation:
Stem cells called oogonia divide mitotically in the ovaries, creating a large pool of cells.
Pre-meiosis and entry into first meiotic prophase:
Oogonia differentiate into primary oocytes, which arrest in prophase I of meiosis for an extended period, sometimes years.
Folliculogenesis:
Surrounding follicular cells nourish and support the growing oocyte, forming a protective layer called the follicle.
Vitellogenesis:
The main event! Yolk proteins like vitellogenin synthesized in the liver are transported to the oocyte and stored as yolk platelets, filling the cytoplasm and providing nutrients for the developing embryo.
Meiotic maturation:
Upon hormonal stimulation, the oocyte resumes meiosis, completing meiosis I and entering meiosis II. At this point, it's called a secondary oocyte.
Ovulation:
The mature oocyte, surrounded by a layer of follicular cells, bursts out of the ovary and into the oviduct, ready for fertilization.
Unique features of amphibian oogenesis:
Long period of meiotic arrest: This extended pause allows for significant growth and yolk accumulation before fertilization.
Large numbers of oocytes:
Amphibians can produce hundreds or even thousands of eggs per breeding season.
Asynchronous development:
Not all oocytes mature and ovulate at the same time, ensuring a longer spawning period.
Environmental control:
Hormonal regulation of oocyte maturation is often triggered by environmental cues like temperature or rainfall.
Additional points of interest:
Different types of amphibians exhibit variations in oogenesis, such as the timing of oocyte maturation and the specific yolk protein sources.
Research on amphibian oogenesis offers insights into early embryonic development and reproductive strategies in these fascinating creatures.
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
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Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
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Acetabularia Information For Class 9 .docxvaibhavrinwa19
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1. OOGENESIS
GUIDED BY PRESENTED BY
BIHUNG BASUMATARY PARAG PATGIRI
ASST. PROFESSOR MSC 2ND SEMESTER
DEPT. OF ZOOLOGY ROLL NO- 01
BODOLAND UNIVERSITY DEPT. OF ZOOLOGY
KOKRAJHAR-783370 BODOLAND UNIVERSITY
KOKRAJHAR-783370
2. CONTENT
o INTRODUCTION
o PROCESS OF OOGENESIS
o OVULATION
o HORMONAL CONTROL IN OOGENESIS
o SIGNIFICANCE OF OOGENESIS
o REFERENCES
3. INTRODUCTION
Oogenesis is the process of formation of female gametes.
It is the type of gametogenesis through which female gametes are formed.
Also known as OVA.
This process begins inside the fetus
before birth.
The steps in oogenesis up to the
production of primary oocytes occur
before birth.
The significance of the egg varies
based on the type of organisms.
4. Primary oocytes do not divide further.
They either become secondary oocytes or degenerate.
Oogenesis occurs in the outermost layers of the ovaries.
Oogenesis starts with a germ cell called oogonium and undergoes mitosis to increase in number.
5. Process of Oogenesis
The process of oogenesis is completed in the following three stages:
1. Multiplication Phase
2. Growth Phage
3. Maturation Phase
6. Multiplication Phase
Certain cells in the germ epithelium of the ovary of the fetus are larger than others in fetal growth.
These cells are separated by mitosis.
Creating a few million egg mother cells or oogonia in each ovary of the fetus.
The oogonia multiplied by mitotic divisions and form the primary oocytes which pass through the
growth phase.
7. Growth Phase
The growth phase of the oogenesis is comparatively longer than the growth phase of the
spermatogenesis.
The size of the primary oocyte increases enormously.
In the primary oocyte, large amount of fats and proteins becomes accumulated in the form of yolk and
due to its heavy weight.
It is usually concentrated towards the lower portion of the egg forming the vegetative pole.
The portion of the cytoplasm containing the egg pro-nucleus remains often separated from the yolk
and occurs towards the upper side of the egg forming the animal pole.
The cytoplasm of the oocyte becomes rich in RNA, DNA, ATP and enzymes.
The mitochondria, Golgi apparatus, ribosomes concentrated in the cytoplasm of the oocyte.
8. Maturation Phase
The maturation phase is accompanied by the maturation or meiotic division.
First Maturation Division:
The homologous chromosomes of the primary oocyte nucleus pass through the pairing or synapsis,
duplication, chiasma formation and crossing over.
The nuclear membrane breaks and the bivalent chromosomes move towards the opposite poles due to
contraction of chromonemal fibers.
A new nuclear envelope is developed around the daughter chromosomes.
The unequal cytokinesis occurs and a small haploid polar body or polocyte and a large haploid secondary
oocyte are formed.
9. Second Meiotic Division:
The haploid secondary oocyte and first polocyte pass through the second meiotic division.
The secondary oocyte forms amature egg and a second polocyte.
By the second meiotic division, the first polocyte also divides into two secondary polocytes.
These polocytes ooze out from the egg and degenerate while the haploid egg cell becomes ready for the
fertilization.
10. Ovulation
Development of oocyte takes place in ovaries.
Every oocyte is neighbored by follicle cells to form a follicle.
As the menstrual cycle starts, primary oocytes initiate to grow bigger, and follicle cells rise in
number, causing the follicle to grow larger too.
When a follicle attains maturity, the primary oocyte finishes its primary meiotic division and becomes
secondary oocyte.
The follicle breaks and secondary oocyte is liberated in the fallopian tube even when the second
meiotic division has not happened.
Meiosis-II is completed on fertilization.
This gives off a third polar body.
If the fertilization does not occur, the oocyte degenerates 24 hours after ovulation while remaining
arrested in meiosis-II cell division.
12. Cyclic changes in the hormonal cycle, governed by the hypothalamic-pituitary system.
It is responsible for the periodicity of the ovulation.
The Pituitary releases two hypophysial gonadotropins FSH and LH.
The pulsating liberation of GnRH by the hypothalamus is the fundamental precondition for a normal
control of the cyclic ovarian function.
FSH and LH stimulates the maturation of the follicles in the ovary and trigger ovulation.
Estrogen is produced by the theca interna and follicular cells, progesterone by the corpus luteum.
The ovarian cycle lasts 28 days.
13. The ovarian cycle is subdivided into two phases:
Follicle phase:
Recruitment of a follicle cohort.
Selection of the mature follicle.
This phase ends with ovulation.
Estradiol is the steering hormone.
Normally, it lasts 14 days, but this can vary considerably.
Luteal phase:
Progesterone produced by the corpus luteum.
It lasts 14 days (relatively constant).
14. Significance of Oogenesis
Oogenesis is the process of formation of female gametes and
WITHOUT OOGENESIS THERE IS NO FERTILIZATION, REPRODUCTION, LIFE !!
15. References
1. Scott F. Gilbert, 2009, “Developmental Biology”, 8Th Edition, Sinauer Associates, Inc. Publishers,
USA.
2. Berry Mitchell, Tam Sharma, 2005, “Embryology an Illustrated color text”, 2nd Edition, Churchill
Livingstone Publishers, Pg: 1-10.
3. https://byjus.com/biology/oogenesis/
4. https://www.embryology.ch/anglais/cgametogen/oogenese04.html