L28 - Spermatogenesis Flashcards
(39 cards)
Define the duration and number of spermatozoa formed in 1 spermatogenesis cycle?
60 -70 days
1 spermatogonium»_space;64 spermatozoa (4 mitosis + 1 meiosis)
Give differences between Meiosis in spermatogenesis and oogenesis?
Spermatogenesis = Uninterrupted, Starts at puberty, Equal cell divisions, Constant stem cell pool for lifelong production
Oogenesis = Interrupted twice, unequal division with polar bodies, All oogonia undergo meiosis before birth = limited number
Compare the end products of spetmatogenesis and oogenesis?
Spermatogenesis = 4 functional spermatid
Oogenesis = one functional oocyte + polar bodies
List the stages of sperm maturation? Define the number of pairs of chromosomes?
Spermatogonium = 2c
Primary spermatocyte = 4c
Secondary spermatocyte = 2c
Spermatid = 1c
Speratozoan (with tail) = 1c
How do spermatogonia retain lifelong capacity to produce spermatocyte?
Number of spermatogonia always remain in stem cell pool and self-renew»_space; unlimited spermatocytes production
Anatomical site of sperm production?
Seminiferious tubules in testis
Define the phases of spermatogenesis that occur in the 2 compartments of the seminiferous tubules?
Basal compartment (outside of Blood-testis barrier) = Mitosis of Spermatogonia
Adluminal compartment = Meiosis and Spermiogenesis
Describe the function of sertoli cells as spermatocytes mature?
Maintain blood testis barrier by breaking tight junctions in front of moving spermatocyte + reforming tight junctions behind
How is testicular temperature regulated?
Testis temp = 2 degrees lower
1) Contraction of scrotum muscle
2) Countercurrent heat exchange between arteries and veins cool arterial blood
Which cell type divide seminiferous tubules into compartments?
Sertoli cells:
Form tight junctions that separate pre- and post-meiotic germ cells
List the 4 main structural changes in spermiogenesis. exam
Nuclear condensation
Shrinkage of cytoplasm
Formation of an acrosome
Development of a tail
How does temperature affect sperm quality?
High temp = decrease sperm quality, motility and count
Describe the process of spermiogenesis?
- Formation of acrosome granules at head of sperm for penetration of egg
- Alignment of mitochondria along tail: store Ca for acrosomal reaction + energy for tail
- form sperm tail for motility
- Nucleus of spermatid become condensed: replace Histone with Protamine
Define spermiation
spermatozoa is extruded into the lumen of the seminiferous tubule
= Ovulation in female
Describe how sperm is transported to the epididymis?
tubular fluid current created by peritubular myoid cells + cilia of epididymis
contraction of the testicular capsule
Describe the change of sperm maturation as it travels through the epididymis?
Sperm gain motility & lose cytoplasm
Define the hormones secreted by Sertoli cells and their functions?
- Anti-Mullerian hormone = regression of paramesonephric ducts before puberty
- Androgen-binding protein (ABP) = high testosterone
- Inhibin/activin:
- Regulate testosterone
- Secreted in different parts of seminiferous tubules to guide spermatogenesis - Plasminogen activator for spermiation
Describe the 2 processes that occur in capacitation of sperm?
- Hyperactive motility
- Acrosome reaction: binding of sperm to ZP3 of zona pellucida causes massive Ca2+ influx at head of sperm
» fusion of sperm and egg membrane
» release proteolytic enzymes for penetration
Compare the physiological effects of Inhibin and Activin secreted by Sertoli cells?
Inhibin = Decrease FSH production at Pituitary, Increase Testosterone production from Leydig cells
Activin = Decrease Testosterone production from Leydig cells, Increase FSH from pituitary
Role of peritubular myoid cells in testes?
modulate function of other testicular cells e.g. Sertoli cells
Contraction = Move spermatozoa to rete testis
List the hormone produced by Leydig cells? Location in testis?
In interstitial tissue outside seminiferous tubules
Make Testosterone»_space; converted to estrogen and Dihydrotestosterone (DHT) in target tissue
The ability to synthesize testosterone begins only at puberty. T or F
False
Testosterone production is high during fetal development and after birth
How is Cholesterol turned into estrogen?
Cholesterol»_space; pregnenolone»_space; progesterone (C21)»_space; Androgen (testosterone, Androtenedione)
Androgen turned into estrogen by Aromatase enzyme
Which hormones controls Leydig cell activity?
Growth factor from germ cells, Pituitary LH, Inhibin from Sertoli= stimulate
Estradiol, Activin from Sertoli = Inhibit
