3: Gametogenesis and Hormones in Reproduction and Development Flashcards
development of gametes
Gametogenesis
Gametogenesis usually not completed until the organism has become
physically mature
Gametogenesis completed in the sexually mature adult, begins at _ times during development, depending on the species
different
Gametogenesis divided into four phases
a.) the extraembryonic origin of the germ cells and their migration into the gonads,
b.) an increase in the number of germ cells by mitosis,
c.) a reduction in chromosomal number by meiosis, and
d.) structural and functional maturation of the eggs and spermatozoa
The first phase of gametogenesis is _ in males and females, whereas distinct differences exist between the male and female patterns in the last three phases.
identical
process of sperm cell production
Spermatogenesis
Spermatogenesis _ process in the adult male
prolific and continuous
Spermatogenesis occurs in the paired male gonads, or testes, specifically in the _
seminiferous
tubules
each ejaculation of a human male contains _ sperm cells, and males can ejaculate daily with little loss of fertilizing capacity
100 to 650 million
Primordial germ cells of the embryonic testes differentiate into
spermatogonia
diploid cells that are the precursors of sperm
spermatogonia
are undifferentiated cells located near the outer wall of the
seminiferous tubules
Spermatogonia
Spermatogonia undergo repeated _ to produce more spermatogonia.
mitosis
In a mature male, about 3 million spermatogonia per day differentiate into _
primary spermatocytes.
diploid or haploid?
Each primary spermatocyte undergoes first meiotic division producing _
haploid secondary spermatocytes.
how many are they?
In the second meiotic division, each secondary spermatocyte gives rise to _
two haploid spermatids.
_ are produced from the original primary spermatocyte.
Four spermatids
Spermatids then differentiate into a mature sperm cell or _.
spermatozoa
The differentiation of the spermatids into sperm cells is called _
spermiogenesis
corresponds to the final part of spermatogenesis and comprises the following individual processes that partially proceed at the same time.
spermiogenesis
Spermatogenesis involves association of the developing sperm with _ which transfer nutrients to the spermatozoa
large Sertoli cells
The release of a sperm cell from its connection to a Sertoli cell is known as
.
spermiation
During spermatogenesis, the developing sperm are gradually pushed toward the _, flow toward _ and make their way to the _ where they acquire motility.
center or lumen of seminiferous tubules
ducts of the testes
epididymis
This process from spermatogonia to motile sperm, takes _ in the human male to complete.
64 days
Sperm cells mature at a rate of _ per day.
300 million
Once ejaculated, they will probably not survive more than _ within the female reproductive tract.
48 hours
The approximate _ cycle of the spermatogenesis can be subdivided into four phases that last differing lengths of time
64-day
process-> days-> product
The Temporal Course of Spermatogenesis
- Mitosis of the spermatogonia - 16 days:primary spermatocytes
- First meiosis - 24 days: secondary spermatocytes
- Second meiosis - few hours: spermatids
- Spermiogenesis - 24 days: sperm cells
parts of sperm
Each mature sperm consists of a
head, midpiece, and flagellum (tail)
The head consists of the nucleus and the nuclear material DNA and a cap called acrosome that produces enzymes _ that aid sperm cell to penetrate the secondary oocyte.
hyaluronidase and proteinases
Numerous mitochondria, located in the _ of the sperm (provides the energy (ATP) for locomotion)
midpiece
A tail, the flagellum has a typical eukaryotic arrangement of _ propels the sperm along its way.
9+2
microtubules
sperm head may appear _ in bull and man, _ in rat, while _ in birds
ovoid
triangular and with a hook
slender and with pointed tips
“discards cytoplasm and growing tails”
Spermiogenesis
Stages of Spermiogenesis
- Formation of the Acrosomal Cap
2.Condensation of the Nucleus
3.Development of the Flagellum
4.Sheath Arrangement of the Mitochondria
5.Cytoplasm Reduction
6.The mature sperm cell is approximately 60 µm long and completely enveloped by the plasma membrane
Formation of the Acrosomal Cap
The development of the acrosomal cap is due to the coalescence of the _ which pinch off from it and forms a membranous structure called acrosome
vesicles of the Golgi apparatus
Formation of the Acrosomal Cap
Acrosome contains enzymes that play important role in the penetration through the _ (part) of the oocyte.
zona pellucida
Formation of the Acrosomal Cap
The acrosome corresponds functionally to a lysosome and thus contains lysosomal enzymes (_ among others).
hyaluronidase
Condensation of the Nucleus
The _ makes it condensed, thus, reducing its size and decreasing the concentration of its chromatin
loss of fluid in the nucleus
Condensation of the Nucleus
The acrosome lies over the _ of the nucleus
tip
Condensation of the Nucleus
_ form the sperm cell’s head that is bound to the mid-piece by a short neck.
Nucleus and acrosome
Involves the generation of the sperm cell tail.
Development of the Flagellum
Development of the Flagellum
At the opposite pole of the spermatids, a _ becomes the root of the growth of a group of microtubules.
pair of centrioles
Development of the Flagellum
The posterior centriole which moves away from the anterior one forms the shape of a _ surrounding the flagellum.
ring
Development of the Flagellum
This organelle supports the developing flagellum which extends into the lumen of the tubule.
mitochondrion
Sheath Arrangement of the Mitochondria
The cell’s mitochondria aggregate around the base of the flagellum forming a _ configuration
spiral
Cytoplasm Reduction
As the event continues, the _ disintegrates, leaving the spermatozoon stripped of all nonessential parts.
residual part of the cytoplasm
All unnecessary cytoplasm is eliminated during the process.
development of ova (mature, unfertilized egg) from oogonia
Oogenesis
Oogenesis involves _ and occurs in the ovaries (the female gonad)
meiosis
1
The process begins when oogonia undergo _ to produce a fixed number of daughter cells during embryonic stage of development
mitotic division
1
Before
birth, hundreds of thousands of _ are present in the ovaries
oogonia
2
_ arises from the primordial germ cell dividing by meiosis in the ovary into oocyte.
Oogonium
2
All of the female’s gametes originate during _.
embryonic development
No new oogonia are formed after birth.
3
During prenatal development, the oogonia increase in size and become _
primary oocyte
4
By the time of birth, they are in the _. At this stage, they enter a resting phase that last throughout childhood and into the adult life
prophase of the first meiotic division
4
A primary oocyte and the cluster of cells surrounding it together make up a _
follicle
4
when?
With the onset of puberty a few follicles develop _ in response to FSH secreted by the anterior pituitary gland.
each month
As the follicle grows, the primary oocyte completes its first meiotic division.
5
?
The two cells produce are different in size. The smaller one, the first polar body.
What divides that eventually disintegrate?
forming two polar bodies
6
The larger cell, the secondary oocyte, proceeds to the second meiotic division but remains in _ until it is fertilized.
metaphase
6
product?
When meiosis does not continue, the second meiotic division gives rise to a
_
single ovum and a second polar body
The polar bodies are small and apparently serve to dispose of unneeded chromosomes with minimal amount of cytoplasm