Gametogenesis
Summary
Description
The animation starts with spermatogenesis.
The first diagram presents a transversal section of an approximately 8-week-old male fetus, showing the testis with testis cords containing gonocytes, among other details. The transversal section of one of the testis cords is magnified. The gonocytes are defined along with their central position within the sectioned testis cord.... (more)
The animation starts with spermatogenesis.
The first diagram presents a transversal section of an approximately 8-week-old male fetus, showing the testis with testis cords containing gonocytes, among other details. The transversal section of one of the testis cords is magnified. The gonocytes are defined along with their central position within the sectioned testis cord. The Sertoli cells, basal lamina and surrounding mesenchymal cells are also shown. The first animated sequence shows the mitotic division of gonocytes. Paternal and maternal autosomes as well as sex chromosomes are described. After division, the daughter cells of gonocytes (i.e. fetal spermatogonia) migrate toward the basal lamina. Myofibroblasts, Leydig interstitial cells and capillary endothelial cells differentiate from the mesencyhmal cells.
To follow one fetal spermatogonium, a basal area of a testis cord is cut out and magnified. The first diagram shows the structure of the fetal spermatogonium, Sertoli cells, basal lamina and myofibroblasts at the onset of puberty. This structure corresponds to the beginning of the multiplication phase of spermatogenesis.
The next sequence shows the mitotic division of the fetal spermatogonium and the formation of type A spermatogonia within the seminiferous epithelium. The chromosome and DNA formula (complement) is given for each division. At the same time, the primordium for a tight junction develops between the bases of the Sertoli cells. Next, the mitotic divisions of type A spermatogonia are shown in parallel with the appearance of stem cells. The formation of the tight junction above one type A spermatogonium divides the seminiferous epithelium into the basal and adluminal compartments. The type A spermatogonium becomes a type B-spermatogonium and migrates through the junction to enter the adluminal compartment, where it divides and gives rise to two primary spermatocytes. This starts the growth phase of spermatogenesis.
The growth of the primary spermatocytes is animated along with their paternal and maternal autosomes and sex chromosomes. The primary spermatocyte formula (complement) is indicated.
The next sequences animate the maturation phase of spermatogenesis, the formation of bivalents of homologous autosomes and the sex chromosomes during the prophase I of the 1st meiotic division. The corresponding chromosome and DNA formula is given. The crossover and interchange of chromatid segments of autosomes and sex chromosomes is demonstrated. The separation of whole chromosomes during anaphase I of 1st meiotic division is animated. The genetic diversity of autosomes is highlighted along with the formation of the haploid secondary spermatocytes.
The secondary spermatocytes become spermatids during 2nd meiotic division. The difference between the 1st and the 2nd meiotic divisions and the genetic particularity of each spermatid are highlighted.
The next sequence shows the transformation phase of spermatogenesis, i.e. the spermiogenesis.
The gradual transformation of spermatogonia into spermatozoa connected with intercellular bridges and the expulsion of residual bodies are shown. The last sequence presents the release of nonmotile spermatozoa from the Sertoli cells. The genetic diversity of each of 8 spermatozoa is given with equal distribution of X and Y chromosomes.
In order to animate the transformation of a spermatid into a spermatozoon, one spermatid is observed under low transmission electron microscopic magnification. The Golgi phase of maturation shows 12 cytologic details, whose evolution is followed in the next 4 sequences. At the beginning of the cap phase, the acrosome starts to develop, the spermatid body elonagets, the chomatin condensates and the future spermatozoon tail starts to grow. The evolution of numerous other cytologic structures is animated simultaneously. During the acrosomal phase, the acrosomal cap spreads over the entire part of the spermatid nucleus. The spermatid nucleus elongates into a hydrodynamic form; the microtubular machette, microtubular sheath and complex ultrastructure of the spermatid tail appear. In addition, the residual spermatid cytoplasm gradually separates. In the maturation phase, the residual cytoplasm separates from the spermatid body, and the lysosomes of the Sertoli cells discharge their enzymes into the residual cytoplasm, thus forming phagolytic vacuoles. The continual elongation of the spermatid body and the breakdown of intercellular bridges are also animated. The expulsion of the mature spermatozoon is shown. A diagram details the ultrastructure of an spermatozoon viewed with the transmission electron microsope.
A special diagram summarizes spermatogenesis.
The following malformations of spermatogenesis are animated: giant spermatozoon with noncondensed chromatin, dwarf spermatozoon, spermatozoon with two tails, spermatozoon with underdeveloped tail, two-headed spermatozoon with excess cytoplasm.
The animation continues with oogenesis.
The first diagram shows a transversal section of an approximately 2-month-old female fetus. In the ovary, the cortical cords break up into isolated cell clusters with oogonia. Numerous other details are described.
One cluster with two oogonia, future follicular cells and the overlying proliferated celomic epitheliumis is magnified. This diagram starts the multiplication phase of the oogenesis.
The oogonia divide by mitosis; paternal and maternal chromosomes as well as X chromosomes are indicated. The endothelial cells of the blood vessels differentiate from the mesenchymal cells. The celomic epithelium differentiates into the germinal epithelium and the future follicular cells multiply by mitosis. In an approximately 3-month-old fetus, the follicular cells suuround each oogonium. The oogonia formula (complement) is indicated. The next sequence shows the multiplication of the follicular cells and the formation of primordial follicles. The oogonia enters 1st meiotic division to become the primary oocytes. The process of DNA replication is animated along with the formation of bivalents and the crossover of chromosomes during the prophase of 1st (reductional) meiotic division. The primary oocyte chromosome formula is indicated. In the next sequence, which animates the continuation of the prophase of 1st meiotic division, the chromosomes decondense, and all primary oocytes enter a long resting period (diplotene stage) during which the chromosomes escape observation. The composition of a primordial follicle is given.
The next sequence animates the follicular atreasia under high magnification. To provide an overview of the extent of atresia, magnification is reduced, and the reduction of primordial follicles is animated through birth.
The onset of puberty starts the growth phase of oogenesis. A segment of the ovarian cortex is cut out and magnified. The diagram shows three primordial follicles, spindle cells of the stroma, tunica albuginea, blood vessels and the germinal epithelium. The next sequence shows the transformation of one primordial follicle into the primary follicle (leading follicle), whose chromosomal formula is indicated. The animation follows the growth of the primary follicle and its transformation into the secondary follicle. The follicular antrum forms from the granulosa cells of a secondary vesicular follicle.
Since the secondary follicle occupies nearly the entire screen, magnification is reduced. The cortex and medulla of the ovary are shown. The primordial follicles and secondary vesicular follicle are visible within the cortex. Blood vessels occupy the medulla. The next sequence shows the growth of the secondary vesicular follicle to form the tertiary or Graafian follicle. The next diagram shows above mentioned details with the oviduct.
The secondary vesicular follicle grows to form a tertiary follicle. The fimbriae of the oviduct surround the tertiary follicle, in whose interior the cumulus oophorus is visible. Numerous other legends explain the diagram.
The next sequences animate the maturation phase of oogenesis. The primary oocyte, which is surrounded by granulosa cells, separates from the stratum granulosum. After expulsion of the 1st polar body, the primary oocyte becomes the secondary oocyte. The animation continues through the metaphase. The formation of the stigma and the dilatation of medullary blood vessels are shown. The ovulation is animated as a rupture of the tertiary follicle. The expulsion of the secondary oocyte into the uterine tube is shown on the 14th day of the cycle.
Because some details escape observation under low magnification, the next sequences animate the maturation phase of oogenesis under high magnification. The first diagram details the primary oocyte and more than 20 structures. Then, the oocyte is shed from the stratum granulosum and enters the follicular antrum. The 1st meiotic division of the primary oocyte (i.e. the end of the diplotene stage of meiotic prophase) is animated. The crossover of chromosomes reappear in the oocyte cyoplasm. During the metaphase of 1st meiotic division, the chromosomes separate; the expulsion of the 1st polar body is shown. Thus, the primary oocyte becomes the secondary oocyte and starts its 2nd meiotic division without DNA replication (Secondary oocyte and 1st polar body formulae are given).
Ovulation occurs with the formation of the metaphase plate of 2nd meiotic division.
The next sequence shows the fertilization of the secondary oocyte, which triggers the anaphase of the 2nd meiotic division. The formation of the male and female pronuclei, the expulsion of the 2nd polar body and the division of the 1st polar body are animated. The genetic diversity of the pronuclei is demonstrated. The next sequence animates the fusion of the pronuclei and the formation of the zygote with a restored number of chromosomes and DNA content.
In order to summarize oogenesis, a recapitulative and animated overview is shown.
A primary follicle with two primary oocytes and a trinuclear primary oocyte are shown as malformations of oogenesis.
A special diagram summarizes spermatogenesis and oogenesis.
The last sequence concerning gametogenesis explains why there are 106 boys born for every 100 girls.
(This animation is essential for students of medicine, veterinary medicine, biology, and stomatology as well as for departments of anatomy, histology, embryology and cell biology; it is also recommended for departments or clinics of obstetrics and gynecology, schools for midwives, and fertility or reproductive biology research institutes.)
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Details
13.8MB in size
1061 pictures
18 chapters
86 legend panels
Version 1.0
Collections
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| All of Embryodynamics (56 animations) | $599.00 | |
| Amnion, Aortic arches, Blood and blood vessels, Body cavities, Central nervous system, Chromosomal anomalies, Cleavage, Cloaca, Cycles, Deciduae, Descent of sexual organs, Diaphragm, Digestive system, Ear, Embryology beginning, Embryonic circulation, Endochondral ossification, Endocrine glands, External genitalia, Eye, Face, Fertilization, Fetal circulation, Gametogenesis, Gastrulation, Gonads, Heart, Implantation, Integumentary system, Kidney, Liver, Long bone growth in diameter, Lymphatic system, Membranous ossification, Mesoderm, Myogenesis, Nerve fibres, Notochord, Olfactory, Pancreas, Pericardial reflexions, Pharyngeal arches, Placenta, Prostate, Respiratory system, Secondary ossification, Sex differentiation, Skeleton, Somites, Teeth, Tongue, Twins, Umbilical cord, Urinary bladder, Uterus during pregnancy, Veins | ||
Structure
View the structure of the Gametogenesis animation without thumbnails:
- GAMETOGENESIS
Animated scheme - 1) Spermatogenesis
- Onset of puberty: Multiplication phase of spermatogenesis or spermatocytogenesis
- Spermiogenesis viewed at the ultrastructural level
- Recapitulative overview of spermatogenesis
- SOME MALFORMATIONS
Giant spermatozoon
Dwart spermatozoon
Spermatozoon with two tails
Spermatozoon with underdeveloped tail
Two headed spermatozoon
Giant spermatozoon with excess of cytoplasm
- 2) Oogenesis
- Prenatal and prepubertal atresia
of primordial follicles
- Onset of puberty
- Now, for didactic reasons the magnification will be reduced...
- Growth of the secondary vesicular
follicle to form the tertiary or graafian
follicle and continuation of the growth
phase of oogenesis
- Maturation phase of the primary
oocyte and ovulation
- Maturation phase of the primary
oocyte viewed under somewhat
higher magnification
- Recapitulative overview of oogenesis
- Comparative diagram of spermatogenesis and oogenesis
- SOME MALFORMATIONS
Primary follicle with two primary oocytes
Trinuclear primary oocyte
- Why at birth there are 106 boys against 100 girls ?
(A partly hypothetical explanation)
- THE
END
RELATED TOPICS are covered in the following animations:
Chromosomal anomalies, Fertilization, Gastrulation, Gonads, Embryology beginnig, External genitalia, Kidney, Mesoderm, Placenta.
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- Cloaca
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- Descent of sexual organs
- Diaphragm
- Digestive system
- Ear
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