Urogenital Flashcards
Describe spermatogenesis
- Mitotic proliferation - Creates large number of identical, diploid spertogonia from gonocyte
- Meiotic division - Creates genetic diversity formind haploid spermatocytes and spermatids. 2 stages.
- Cytodifferentiation (spermiogenesis) - genes packed for delivery and spermatozoa elongated
What are the role of sertoli and leydig cells, where are they found and what hormones stimulate them ?
Sertoli cells
- Found in the seminefrous tubules
- Attached to sperm via gap junctions, mediating androgen hormone action and convert testosterone into dihydrotesttestorone
- FSH stimulates them to increase receptors for androgens
Leydig cells
- Convert choleterol in prognenolone which then forms testosterone
- Testosterone passed into blood of sertoli cell to be converted. Dihydrotestosterone most potent androgen, stimulates spermatogenesis
GnRH released from Hypothalamus stimulates release of LH/FSH from Anterior pituitary. Negative feedback loop
Describe the changes undergone by spermatozoa during epididymal maturation
- loss of surplus cytoplasm
- addition of glycoproteins (decapacitation facters)
- condensation of nuclear chromatin
- depression of metabolic activity (prolong life)
- increased dependance on external fructose
- cAMP content in tail increased allowing Motility!
Describe the contents of seminal plasma and what accessory glands produce it
Produced in Ampulla, seminal vesicles and prostate
- Glycoproteins
- Fructose
- Citric acid
- Acsorbic acid (stop sperm being oxidated)
- Buffers
- Prostaglandins
Describe folliculogenesis
Primordial follicle - Fixed number at birth!
- 1 primary oocyte and 1 layer of granulosa cells
Primary follicle
- Increased oocyte size
- 1 layer of cuboidal granulosa cells seperated from oocyte by zona pellucida (have GnRH receptors but no blood supply)
Secondary follicle
- Multiple layes of granulosa
- Theca cells for and differentiate to form interna & externa
- Vascularisation of theca layer allowing LH/FSH into follicles
Tertiary follicle
- Granulosa secrete fluid froming antrum
- Pituitary LH causes theca cells to become steriodogenic producing Androstendione, the substrate for oestrogen synthesis by granulosa cells
- Pituitary FSH stimulate granulosa proliferation
Graafian follicle
- thought to be selected due to competition for FSH
- Remaining tertiary follicles undergo atresia
Describe positive feedback loop involving eostrogen, LH and FSH
- Oestrogen stimulates pituitary release of LH & FSH
- FSH causes granulosa cells to proliferate
- LH stimulates theca cells to produce androgens (Androstendione)
- Androstendione converted into oestrogen by granulosa cells
- More oestrogen = more LH/FSH!
How is ovulation induced?
- High levels of eostrogen cause a LH surge
- LH surge induces release of proteolytic enzymes that weaken follicular wall
- LH also increase blood flow to follicle, causing an increase in pressure leading to rupture of the wall
- stigma
What are the funtions of oestrogen and progesterone in the female
Oestrogen
- prepare uterus for sperm transport
- stimulate the growth of mammary glands and endometirum
- regulate secretions of gonadotropins
Progesterone
- Maintain uterus during pregnancy
- Stimulate growth of mammary glands but suppress secretion of milk
- regulate secretions of gonadotropins
Describe oestrus cycle
- Pro-oestrus - Immediately before onset of behaviour (Follicular phase, E2 dominant)
- Oestrus - Mating behaviour (follicular phase, E2 dominant)
- Metoestrus - Transition period
- Dioestrus - CL formed, length dependent on life of corpus luteum (Luteal phase, Progesterone dominant)
- Anoestrus - quiescent period
Describe sperm changes that occur in the female tract
Capacitation - uterus
- Progressive destabilisation of the plasma membrane and removal of gylcoproteins exposing ZP3
- Surface charge altered (attract to oocyte?)
- membrane fluidity increased, aiding in breakdown of acrosome and influx of calcium ions
Hyperactivation - oviducts
- Increased intracellular calcium leads to elevated cAMP levels
- Increased force required to swim through viscous environment of oviduct
Acrosome reaction - at fertilisation
- Sperm binds to oocyte via ZP3
- Fusion of sperms plasma membrane and oute acrosomal membrane
- Enzymes hyaluronidase/acrosin digest through zona pellucida and sperm moves into pervitelline space
- Equatorial segment fuses with plasma membrane of oocyte and sperm engulfed
- Cortical granules released by oocyte into pervitelline space to prevent polyspermy
Whats the difference between passive and active luteolysis
Passive Luteolysis
- Occurs in primates
- A decrease in LH during the luteal phase leads to regression of the corpus luteum
- Blastocyst secretes LH like substance (hCG) to prolong CL life
Active Luteolysis
- Oxytocin binding leads to the release of PGF2a
- Release of Interferon Tau from trophoblast prevents production of PGF2a
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Describe the structure of a placentome
- maternal curuncle
- Foetal cotyledon
- Six layers of seperation between foetal and mother blood, minimally invasive placenta. Good for prey species, reduction in blood loss when placenta is expelled
Describe how Parturition is induced by foetal stress
What are the roles of oxytocin, prostaglandins and oestroegn during parturition
Oestrogen
- Cause hypertrophy of myometrial smooth muscle
- Liberate phospholipase A2 from lysosomes, allow convertion on arachidonic acid to prostaglandin
Oxytocin
- release from posterior pituitary in response to cervical stimulation by foetus
- Lowers excitation threshold of muscles
Prostaglandins
- Stimulate liberation of calicum ions from intracellular stores
- facilitate softening of cervix by increasing collage breakdown, increasing proteoglycan matrix fibres and stimulating uterine activity
What is primary and secondary inertia and what are their causes
Primary inertia
- Failure to initiate contractions
- Lack of oxytocin or oxytocin receptors
- obesity
- small foetus
Secondary inertia
- good initial uterine contractions then a sudden stop
- Uterus can become fatigued and over stretched
- Litter size is large
