Histology -- Spermatogenesis Flashcards
Define spermatogenesis
An elaborate process of cell differentiation starting with non-differentiated spermatogonial stem cell and terminating with a fully differentiated highly specialized motile cell called spermatozoa
Location of the formation of spermatozoa
Seminiferous epithelium
2 populations of cells composing the seminiferous epithelium
Somatic Sertoli cells
Spermatogenic cells
Fate of spermatogonia
Division and differentiation into spermatocytes
Fate of spermatocytes
Undergo meiosis to originate spermatids
3 phases of spermatogenesis
- Spermatogonial phase (proliferation, renewal and differentiation of spermatogonia)
- Spermatocyte phase (meiosis)
- Spermatid phase (spermiogenesis)
3 types of spermatogonia and what differentiates them from each other
- Type Ad (dark; less active)
- Type Ap (pale; true stem cells)
- Type B (differentiated)
Amount of DNA in primary spermatocytes and why
4n (44 autosomes and an X and a Y chromosome each having two chromatin strands or chromatids) since spermatocytes replicate their DNA shortly after they form
4 stages of prophase of the first meiotic division of spermaocytes
- Preleptotene
- Leptotene
- Zygotene-Pachytene
- Diplotene
Describe the preleptotene and leptotene phases of spermatocyte division
Chromatin condenes into visible chromosomes
Describe the Zygotene-Pachytene of spermatocyte division
Homologous chromosomes paired
Describe the diplotene stage of spermatocyte division
Pairs of homologous chromosomes called tetrads (because they consist of 4 chromatids) exchange genetic material by crossing over
Describe what occurs afer prophase of spermatocyte division
Primary spermatocytes divide and the tetrads separate to become diads in the daughter cells
Amount of DNA in secondary spermatocytes
2n DNA (22 autosomes and an X or a Y chromosome [haploid])
Describe what occurs during the metaphase of the second division of spermatocytes
Sister chromatids separate into two haploid round spermatids
Amount of DNA in round spermatids
1n amount of DNA
4 phases of spermiogenesis
- Golgi phase
- Cap phase
- Acrosome phase
- Maturation phase
Describe the Golgi phase of spermiogenesis
The Golgi apparatus forms a proacrosomic granule within an acrosomic vesicle. Centrioles start forming the axonese (tail)
Describe the cap phase of spermiogenesis
The acrosomal vesicle spreads to cover the anterior half of the nucleus.
Describe the acrosome phase of spermiogenesis
The head of the spermatid is oriented towards the basement membrane. The machete of microtubules forms and the Golgi apparatus migrates posteriorly.
Describe the maturation phase of spermiogenesis (4 events)
- Spermatid elongates
- Chromatin condenses
- Mitochondria migrate and form the mid piece of the tail (NOTE: Primary piece has no mitochondria)
- A residual body (surplus of cytoplasm) is formed and eliminated
Duration of spermatogenesis in a man
Fixed and constant at 60 days
Frequency at which stem cells enter spermatogenesis in a man
Regular intervals of 16 days
Describe how stem cells enter spermatogenesis
In groups, the members of which are connected by open intercellular bridges, which also connect the daughter cells until the end of spermatogenesis
What structure contains the hydrolytic enzymes necessary for he fertilization of the ovum?
Acrosomic cap structure
Define one generation of germinal cells
One group of cells at one stage of development
Number of generations of germinal cells seen in the epithelium of the seminiferous tubules
4 - 5
Cause of immotile cilia syndrome in men
Mutations in the dynein gene and in other genes encoding proteins required for flagellar and ciliar motility
Associated conditions to immotile cilia syndrome
Chronic respiratory infections (impaired motility of the cilia of the respiratory epithelium)
Potential use for stem cell transplantation regarding male testes
Useful in testicular cancer of young individuals (use for fertilization post-radiotherapy, which kills sperm cells)
Situation in which in vitro fertilization is useful
Obstructive azoospermia
Define ICSI
Intracytoplasmic sperm injection into oocytes
Define ROSNI
Round spermatid nuclear injection into oocytes
Define ROSI
Round spermatid injection into oocytes
