The Reproductive System: Gametogenesis: Sperm Flashcards
Gametogenesis
Gametes are haploid cells that combine to form new combination of genes
Gametogenesis: Male
Sperm
Ongoing in the testes
Where is sperm produced?
Testes
Gametogenesis: Female
Oocyte → Ova
Arrests during meiosis prior to birth
Where are oocytes produced?
Ovaries
Where are the testes located?
External to the main body cavity in the scrotum
Tunica Albuginea
Dense CT
Surrounds the seminiferous tubules
Tunica Vasculosa
Loose CT containing blood vessels
Found between the albuginea and tubules
Layers of the testes
Epididymis
Tunica Albuginea
Tunica Vasculosa
Seminiferous tubules - Tunica Propria
Tunica Propria
Layer of collagen fibers and myoid cells
Surrounds each seminiferous tubule
No fibroblasts
What are Myoid Cells?
Peritubular contractile cells
Similar to smooth muscle
Have alot of RER for collagen production
What is the function of myoid cells?
Contraction produces peristaltic waves that move spermatozoa and testicular fluid out of seminiferous tubules
Where are myoid cells located?
On the outside of seminiferous tubules
What are leydig cells?
hormone-producing interstitial cells (steriod)
surrounded by CT - between seminiferous tubules
Store a lot of lipid (foamy inside)
When are Leydig Cells active?
During early fetal development
Inactive until puberty
What activates Leydig Cells?
Gonadotropic pituitary hormones
Spermatogenesis
Population of basal cells that divide (by mitosis) to produce additional gametes
What gametes are produced during mitosis of spermatogenesis?
Spermatogonia
What stage of gametes are produced during Meiosis I and Meiosis II during spermatogenesis?
Primary and secondary spermatocytes
What is the difference between primary and secondary spermatocytes?
Primary have constricted chromatin
Secondary typically are not visible
What are the haploid gametes produced by meiosis?
Spermatid
What regulates spermatogenesis?
Sertoli cells
Starting at Mitosis, what are the stages of Spermatogenesis and what gametes do they form?
Mitosis → Spermatogonia phase
Meiosis I and II → Spermatocytes phase
Spermatid phase
Residual bodies
Spermatozoa
Why are Sertoli Cells called the “true” epithelium of seminiferous tubules?
All other cells present in the walls of seminiferous tubules are spermatogenic cells
What are residual bodies?
Every part of early spermatids that won’t be present in final spermatozoa
Where are spermatogonia located?
Closest to the basal lamina
What are the stages of spermatogenesis?
- very few primary spermatocytes
- Release of late spermatids
- No late spermatids
- No early spermatids
- No early spermatids
- Anaphase in primary spermatocytes
Why wont you see every stage in every area of a seminiferous tubule?
Spermatogenesis occurs in waves
What is the difference between spermatogesis stages in mice vs. human?
Mice are segmented
Human are patchwork
Describe Primary Spermatocytes histologically
Condensed chromatin
Speckled pattern
Describe spermatogonia histologically
Closest to basement membrane
Round
Relativly evenly stained nucleus
Describe the difference between early spermatids and late spermatids histologically.
Early Spermatids → rounder, lighter
Late Spermatids → Arrow head shape, darker
What are Sertoli Cells? What are their function?
Supporting cells of seminiferous tubules
Regulate Spermatogenesis
Receptors for what hormones are found on Sertoli Cells?
FSH and testosterone
How do Sertoli Cells regulate spermatogenesis?
They keep the different stages seperate by extending processes between all spermatogeneic cells as well as to seperate developing sperm from the rest of the body
Why do developing sperm need to be seperated from the body?
They arent there during fetal development so exposure may result in attack from the immune system.
Describe the process of spermatid remodeling.
- Golgi forms acrosome - determining anterior pole
- Acrosomal cap forms - Flagellum extends into lumen
- Cytoplasm shifts to posterior as nucleus and acrosome shift to anterior
- Remove excess cytoplasm
Late spermatids are connected to…
Sertoli Cells
Where are spermatids produced/released from?
Sertoli cells
How are spermatids released?
By cleavage of specific junctions to become spermatozoa
What is the path spermatids follow after release from Sertoli Cells?
- Released from Sertoli Cell
- Travel through tubuli recti (straight tubules)
- Through the rete testis (series of channels)
- To the Ductuli Efferentes (akak the efferent ductules)
What is the different between straight tubules and rete testis?
Straight tubules → found around seminiferous tubules, lined with sertoli cells (simple columnar epithelium); nuclei with prominant nucleuolus
Rete testis → found in mediastinum, simple cuboidal epithelium
Where do all seminiferous tubules drain into?
Mediastinum
What is the mediastinum?
Dense CT with blood vessels
Contains rete testis
Somewhat similar to hilum of other organs
