Repro6 - Gametogenesis Flashcards
5 features of spermatogenesis
Spermatogonia Primary Spermatocyte Spermatozoa Spermatogenic Cycle Spermatogenic Wave
- ) Spermatogonia + mitosis –> Ad Spermatogonium (reserve stock) + Ap Spermatogonium (active stock)
- Ap Spermatogonium + puberty –> Type B Spermatogonia –> Primary Spermatocyte - ) Primary Spermatocyte + meiosis 1 –> 2 Secondary Spermatocytes + meiosis 2 –> 4 Spermatids
- Spermatids + spermiogenesis –> spermatozoa - ) Spermatogenic Cycle - time taken for reappearance of the same stage within a given segment of tubule
- 16 days in humans
4.) Spermatogenic Wave - distance between the same stage within the testes
3 features of spermiogenesis
Spermiation
Remodelling
Peristaltic Contraction
- ) Spermiation - spermatids released into lumen of seminiferous tubules
- ) Remodelling - occurs as they pass down the tubule, rete testis, and epididymis to form spermatozoa
- ) Peristaltic Contraction - they are non motile so they rely on secretions by sertoli cells to aid movement
4 divisions in the structure of spermatoza
- ) Head - contains acrosome, plasma membrane, and nucleus
- ) Mid (connecting) Piece - contains centriole, mitochondria, and terminal disc
3/4.) Tail and End Piece - axial filament runs throughout
5 features of the components and delivery of semen
Pathway Seminal Vesicle Secretions Spermatozoa Prostate Secretions Bulbourethral Gland Secretions
1.) Pathway - seminiferous tubules –> rete testis –> ductuli efferentes –> epididymis –> vas deferens –> urethra
- ) Seminal Vesicle Secretions (70%) - vas deferens
- contains AAs, citrate, fructose, and prostaglandins
- provides nutrition and helps neutralise acidity of vagina - ) Spermatoza (2-5%) - also occurs in vas deferens
- 200-500 million per ejaculate - ) Prostate Secretions (25%) - occurs while in urethra
- contains proteolytic enzymes and zinc
- produces the milky secretions and is mildly acidic - ) Bulbourethral Gland Secretions (< 1%) - in urethra
- contains mucoproteins to help lubricate and neutralise acidic urine in distal urethra
5 features of sperm capacitation
What is it? Function Sperm Membrane Sperm Tail IVF
- ) What is it? - final maturation step, that occurs in the female reproductive tract
- activates sperm signalling pathways - ) Function - allows sperm to bind to zona pellucida of oocyte and initiate acrosome reaction
- ) Sperm Membrane - removal of glycoproteins and cholesterol to allow fusion with zona pellucida
- ) Sperm Tail - tail movement: wave-like –> whip-like
- allows penetration of the zona pellucida
5.) IVF - human sperm in IVF must first be incubated in capacitation media
4 features of maturation of oocytes before birth
Oogonia
Primary Oocytes
Atresia
Primordial Follicle
- ) Oogonia - arise from germ cells arising from yolk sac
- some proliferate by mitosis, others enter meiosis - ) Primary Oocytes - oogonia which enter meiosis
- arrest in prophase of meiosis 1 until puberty
- no of germ cells by mid gestation is 7 million - ) Atresia - cell death causing degeneration of many oogonia and primary oocytes
- by 7 months, majority of oogonia have degenerated leaving 2 million primary oocytes
4.) Primordial Follicle - primary oocyte surrounded by follicular cells (layer of flat epithelial cells)
4 features of the preantral stage during maturation of oocytes at puberty
Continued Atresia
Structure Change
Zona Pellucida
Primary Follicle
- ) Continued Atresia - occurs during childhood
- by puberty, only 40,000 primary oocytes remain
- from puberty, 15-20 oocytes start to mature each month (only 1 makes it) passing through 3 stages: - ) Structure Change - follicular cells change from flat to cuboidal and proliferate, producing stratified epithelium of granulosa cells
- ) Zona Pellucida - formed by the granulosa cells secreting a layer of glycoproteins
- ) Primary Follicle - the primordial follicle has now become the primary follicle
5 features/structures of the antral stage during maturation of oocytes at puberty
Follicular Antrum Theca Interna Theca Externa Cumulus Oophorus Secondary Follicle
- ) Follicular Antrum - fluid filled spaces appear between granulosa cells which coalesce to form the antrum
- ) Theca Interna - inner secretory layer that secretes androstenedione taken up by granulosa cells
- ) Theca Externa - outer fibrous layer
- ) Cumulus Oophorus - granulosa cells surrounding the oocyte
- ) Secondary Follicle - the primary follicle has now become the secondary follicile
3 features of the preovulatory stage during maturation of oocytes at puberty
- ) Induction - induced by surge in LH
- ) Secondary Oocyte - meiosis 1 is completed which produces a secondary oocyte and a polar body
- ) Meiosis 2 - cell enters meiosis 2 but arrests in metaphase 3 hours before ovulation
- meiosis 2 is only completed if the oocyte is fertilised otherwise the cell degenerates 24 hours after ovulation
4 features of ovulation
1.) FSH and LH Stimulation - causes rapid growth of follicle several days before ovulation occurs
- ) Graafian Follicle - new name of the mature follicle
- its a roughly 2.5cm in diameter - ) Collagenase Activity - increased by surge in LH
- prostaglandins increase response to LH causing local muscular contractions in ovarian wall
4.) The oocyte is eventually extruded and breaks free from the ovary
4 features of the corpus luteum
Contents
Secretions
hCG
Corpus Albicans
1.) Contents - vascularised granulosa and theca interna cells develop yellow pigment, changing to lutein cells
- ) Secretions - oestrogens and progesterone
- stimulates the uterine mucosa to enter secretory stage to prepare for embryo implantation - ) Human Chorionic Gonadotropin (hCG) - prevents the degeneration of the corpus lutem so it grows further
- its is secreted by the developing embryo
- CL of pregnancy is corpus luteum graviditatis - ) Corpus Albicans - mass of fibrotic scar tissue that is formed if fertilisation doesn’t occur (no hCG) in 14 days
- progesterone production decreases, causing menstrual bleeding
