Reproductive system Flashcards
What are primary oocytes?
Egg cells surrounded by zona pellucida; formed at birth (~2mil) that is maintained in a state of meiotic arrest until puberty.
What is oogenesis?
process of egg (oocyte) development in females, which occurs in the ovaries.
What does the primary follicle encompass the primary oocyte in?
- granuolsa cells
- basal lamina
- thecal cells
What are the two fates of follicles?
Ovulation (release of secondary oocyte) or Atresia (Degeneration of oocyte within follicle)
3 main components of the ovarian cycle?
- Follicular phase: prep of oocyte
- ovulation: release of secondary oocyte
- luteal phase: preparation of reproductive tract for pregnancy via corpus luteum hormones
What are the three phases of the uterine cycle?
Menses: beginning of follicular phase
Prolferative phase: latter part of follicular phase
Secretory phase: luteal phase
What are the FSH and LH levels during the ovarian cycle?
- Follicular phase (menses): FSH>LH
- Follicular phase (proliferative): FSH<LH
- Ovulation: FSH spikes a little, LH spikes a lot
- Luteal phase (secretory): LH>FSH
What are the development of the primary oocyte?
- Primary follicle: Oocyte arrested in prophase I, surrounded by single layer granulosa and thecal cells
- Secondary follicle: Oocyte arrested in prophase I, multiple layers of theca, multiple layers of granulosa that secrete Antrum
- Tertiary follicle: Secondary follicle grows large and has produced estrogen rich antrum due to thecal and granulosa cells, first meiotic division completed
How do LH and FSH control ovulation?
LH: targets thecal cells
FSH: target granulosa cells
How does the secondary oocyte leave the follicle?
Collagenases secreted by the follicle expels secondary oocyte into the abdominal cavity and down the oviduct
How does the secondary follicle develop post release of secondary oocyte?
Granulosa and tehcal cells differentiate into CORPUS LUTEUM which synthesize and secrete progesterone with some estrogens.
How does the corpus luteum develop with and without fertilization?
With fertilization: corpus luteum grows into mature corpus luteum
Without fertilization: corpus luteum grows into corpus albicans (due to white colour)
What are the 4 stages of the sexual act for biological females?
- Excitement: arousal and erection - increase PSNS, decrease in SNS
- Pleateau: continued arousal, increased heart rate, BP, respiration rate
- Orgasmic phase: aid in sperm transport
- Resolution: decrease in arousal
Where do testes develop?
Gonadal ridge and descend through inguinal canal into the scrotum before 7 months of gestation
What is cryptorchidism?
one or both of the testes fail to descend into the scrotum before birth or shortly after
What are the parts of the testicle?
seminiferous tubules go to epididymis which expand in lumen size in the vas deferens
What are the cells of the seminiferous tubule from the lumen outward?
- Spermatozoa
- Sertoli cells + sperrmatocytes
- Basal lamina and fibroblasts
- Leydig cells surrounded by capillaries
Why is the lumen of the seminiferous tubule high in K+?
limit sperm mobility which reduces metabolic rate and energy demand
What do leydig cells do?
Lie within the interstitium between seminiferous tubules and make dihydrotestosterone (potent testosterone)
What are some of the functions of testosterone?
- Influence reproductive system prior to birth
- influence sex-specific tissues after birth
- development of secondary sexual characteristics and non-sexual characteristics
4 parts of sperm
- head: contains nucleus
- acrosome: coontains enzymes too degrade oocyte membrane
- mid-piece: mitochondria rich for flagellum
- Flagellum: swimming
What are sertoli cells for?
- Protect and nourish sperm cells
- remove unwanted material
- secrete seminiferous tubule fluid and androgen binding protein.
How does GnRH promote testosterone production via FSH?
- GnRH triggers production of FSH and LH in anterior pituitary
- LH targets leydig cells outside the testes, inducing testosterone production and sending it too the sertoli cells
3.. FSH binds to receptor on testes, promoting proliferation of inhibin and sertoli cells.
4.. Sertoli cells create more spermatogonia and androgen binding protein in the lumen which couple with testosterone from leydig cells
What does the epididymis do?
Concentrates non-motile, infertile sperm through reabsorption of fluid and protects sperm with defensins
What are the accessory glands of the male reproductive tract?
- Seminal vesicle: empties fructose, prostaglandins, seminal fluid and fibrinogen into ejaculatory duct
- prostate: secretes alkaline fluid (increasing motility), clotting enzymes (fibrinolysin)
- Bulbourethral gland: secretes mucus like subbstance for lubrication
What are the 4 phases in the male sexual act?
Excitement: arousal and erection
Plateau: continued arousal, increased heart rate, blood pressure, respiraton rate
Orgasmic phase: ejaculation and muscle contraction + phyiscal pleasure
Resolution: return to pre-arousal state (latency period)
What is the erection pathway?
- Tactile stimuli on glans triggers mechanoreceptor on sensory neuron
- Sensory neuron synapses at spinal chord and ascends to higher brain centres
- Descending autonomic pathways inhibit sympathetic neurons and stimulate parasympathetic neurons
- Parasympathetic neurons trigger vasodilation of penile arterioles, and vasoconstriction of venules, maintaining erection. Also triggers bulbourethral and urethral glands
What does sildenafil do?
- When NO is released during parasympathetic stimulation, it acts as a ligand for a signal cascade that produces cGMP.
- cGMP initiates PKG pathway which leads to the activation of SERCA which dilates arteries
- PDE 5 is an enzyme that inhibits SERCA activation by breaking down cGMP.
- Sildenafil blocks PDE 5
What is the pathway of GnRH in response too high plasma estrogen?
- Positive feedback on GnRH
- Increase in GnRH
- Increase in FSH & LH, targets ovary for ovulation
What is the pathway of GnRH on moderate plasma estrogen or androgen?
- negative feedback on GnRH
- decrease in GnRH
- Decrease in FSH andLH
- Decrease in estrogen or androgen production
What is the pathway of GnRH on low plasma estrogen or androgen?
- NO feedback on GnRH
- increase in GnRH
- Increase in FSH & LH
- Targets gonad for increase increase in estrogen or androgen productions
How does the follicle undergo steroidogenesis via Delta 5 in FOLLICULAR PHASE?
- Cholesterol to pregnenolone
- Pregnenolone to 17-hydroxypregnenolone
- DHEA
- Androstenedione
- Estrone/testosterone
How does the follicle undergo steroidogenesis via Delta 4 in LUTEAL phase?
- cholesterol to pregnenolone
- pregnenolone to progesterone
- progesterone to hydroxyprogesterone
- Androstenedione
- Estrone/testosterone
What is kisspeptin?
stimulates the release of GnRH, which triggers the release of FSH and LH from the anterior pituitary, starting the process of ovulation and spermatogenesis
What is human chorionic gonadotropin?
produces by blastocyst to preserve the corpus luteum
What is the human placental lactogen?
involved with mammary gland development and regulating maternal metabolism
What is the pathway for onset parturition?
- Placenta produces CRH which stimulates ACTH release
- ACTH release targets fetal adrenal cortex to release cortisol and DHEA
- Cortisol targets fetal lungs to produce pulmonary surfacant for breathing air and DHEA in the placenta is converted to estrogen
- Pulmonary surfacant increases the macrophages in utero, especially IL-1B which couplees with NF-kB activated by uterine stretching into IL-8.
- Activated NF-kB and estrogen increase prostaglandin production which causes cervical stretching
- Estrogen increases gap junctions between myometrial cells and oxcytocin receptors in myometrial cells.
What is the positive feedback loop for parturition?
- Uterus sees low level of OT
- uterus contracts which push fetus afainst the cervix
- Pushing causes neuroendocrine reflex that releases oxytocin and prostaglandin
- Oxytocin and prostaglandin reinforce step 1
What is the let down reflex in nursing mothers?
Inhibition of prostaglandin inhibiting hormone, allows stimulus of milk production by prostaglandin releasing hormone
