Gametogenesis Flashcards
What determines the sex of the offspring?
Whether the sperm contains an X or Y chromosome
What is the function of meiosis?
Reduce chromosome number to 23
Ensures genetically unique
Crossing over
Produces 4 daughter cells (3 are polar bodies in females)
How does genetic variation arise?
Crossing over
Independent assortment
Random segregation
Outline spermatogenesis
Occurs in the seminiferous tubules
Spermatogonia divide by mitosis = 1) AD spermatogonium: reserve stock, 2) AP spermatogonium: give rise to type B spermatogonia which give rise to primary spermatocyte
Primary spermatocytes divide my meiosis = secondary spermatocytes then = spermatids
What is the spermatogenic cycle?
Time taken for reappearance of the same stage within a given segment of tubule
~16 days
What is the spermatogenic wave?
Distance down the length of the seminiferous tubule, between the same stage
Outline the role of the rete testis
Concentrate the spermatozoa
Describe the role of the epididymis
Storage tube for sperm
What is the role of the vas deferens?
Tube carrying sperm from epididymis to the urethra
What is the basal compartment of the testes?
Spermatogonia (germ cells) reside
Define spermiation
Spermatids being released into the lumen of the seminiferous tubule
Outline the journey of the sperm
Seminiferous tubule
Rete testis
Ductuli efferentes
Epididymis
Vas deferens
Urethra
Outline the role of the seminal vesicle
65% vol
Secrete = AA, citrate, fructose, prostaglandins
What is the role of the prostate?
25% vol
Secrete = proteolytic enzymes, zinc
What is the role of the bulbourethral glands?
1% vol
Secrete = mucoproteins: help lubricate and neutralise acidic urine in distal urethra
What is capacitation?
Final maturation step required before sperm becomes fertile
= removal of glycoproteins/cholesterol = allow sperm to bind zona pellucida and initiate acrosome reaction
Outline the maturation of oocytes before birth
Germ cells diff into oogonia
Oogonia divide by mitosis
Some enter meiosis but arrest in prophase of meiosis I = primary oocytes
Become surrounded by follicular cells = primordial follicle
What are the stages of an oocyte maturing at puberty?
Preantral
Antral
Preovulatory
Outline the preantral stage
follicular cells change into stratified ep of granulosa cells = primary follicle
Outline the antral stage
theca cell present (prod androgens)
space appears between granulosa cells called antrum = sec follicle
Outline the preovulatory stage
meiosis I now complete giving 2 daughter cells
enters meiosis II but arrests in metaphase
finishes meiosis II if fertilised
if not fertilised cell degenerates
Briefly outline ovulation
FSH + LH stimulate rapid growth of follicle
LH surge = collagenase activity
Prostaglandins = local contractions of ovarian wall
Oocyte extruded
What happens to the follicle once ovulation has occurred?
Granulosa and theca cells become vascularised = corpus luteum
Secrete oestrogen and progesterone
What happens if the oocyte isnt fertilised ?
Corpus luteum degenerates = corpus albicans
What happens to the corpus luteum of the oocyte if fertilisation occurs?
Corpus luteum grows = corpus luteum graviditatis
Very briefly outline the cell stages of the ovarian cycle
Primary follicle Secondary follicle Ovulation (LH surge) Corpus luteum Corpus albicans
