Gametogenesis Flashcards
What similarities do both gametogenesis pathways share?
Both proliferate by mitosis
Reshuffle genetically and reduce to haploid cells via meiosis
Cytodifferentiate into mature gametes
What are the main differences between the ovum and sperm?
Females produce very few gametes (400 in a lifetime)
Females produce gametes intermittently (1 per month)
Males produce many (200 million per day) continuously
What three features of meiosis ensure genetic variation?
Crossing over
Independent assortment
Random segregation of alleles
At what point in meiosis does crossing over occur?
Prophase 1
What is the function of the blood testis barrier in males?
Keeps basal and adluminal compartments separate and protects spermatozoa from a host immune response
What cells are often referred to as nurse cells?
Sertoli cells. Nurture sperm and precursors
What is the purpose of Leydig cells?
Produce testosterone
Name the different precursors for spermatozoa throughout spermatogenesis?
Spermatogonium - primary spermocyte- secondary spermocyte - spermatid- spermatozoa
What are Ad spermatogonium?
What are Ap spermatogonium?
Ad - resting, reserve stock
Ap - active, maintain stock and produce type B spermatogonia giving rise to new primary spermatocytes
What defines spermatogenic cycle?
Time taken for reappearance of the same stage of spermatogenesis within a given segment of a tubule
What defined spermatogenic wave?
Distance between the same stage on two different cycles
What is spermiation?
Spermatid release into the lumen of seminiferous tubules
What is spermiogenesis?
Release of spermatic s into seminiferous tubules (spermiation) and remodelling of sperm as they move to the epidydimis and gain motility.
How do the non motile spermatids reach the epididymis?
Transport via Sertoli secretions and peristaltic contraction
What is sperm capacitation?
What clinical relevance does this have?
Removal of glycoproteins and cholesterol from sperm membrane to make sperm fertile
In vitro fertilisation requires sperm to be incubated in capacitation media
What is atresia?
Cell death and degeneration of primary oocytes in female reproduction
What are primordial follicles?
Surviving oocytes that have entered meiosis 1 and are surrounded by flat epithelial follicular cells
What occurs in the preantral phase of oogenesis?
Follicular epithelium changes from flat to cuboidal and proliferate to form granulosa cells
What occurs in the antral stage of oogenesis?
Fluid filled spaces appear between granulosa cells and coalesce to form the antrum
What occurs in the preovulatory phase of oogenesis? (Caused by a surge of LH)
Oocyte completes meiosis 1 forming a polar body, then undergoes meiosis 2 but arrests in metaphase.
How does ovulation occur?
Surge in LH causes increased collagenase activity and prostaglandins cause local muscular contraction resulting in oocyte extrusion
What is the corpus luteum?
Remaining granulosa and the a interna cells that develop into lute in cells
Secrete oestrogen and progesterone to prepare uterine mucosa for implantation
How is the oocyte transported into and through the uterine tubes?
Fimbrae sweep over the ovary and guide the ovum in.
Uterine tube contracts rhythmically to propel the ovum
What is the corpus albicans?
Degeneration of the corpus luteum forming scar tissue. Precipitates menstrual bleeding
