Reproduction Flashcards
How is sex determined in humans?
Presence of SRY gene on y chromosome
Produces testes determining factor which results in testes
What are some sex chromosome abnormalities?
Turners syndrome- female phenotype by XO/no second sex chromosome
Klinefelters syndrome- male phenotype but some female characteristics, XXY chromosomes
Androgen insensitivity syndrome- inability to respond to androgens, male genotype but female phenotype
List the stuructures in the female reproductive system
Uterine tube Uterus Ovaries Cervix Vagina
What are the functions of the ovary?
Gamete production
Hormone production
What is the importance of oestrus?
Occurs before ovulation so increases chance of successful fertilisation
Define oogenesis
Formation of ovum
What are the reproductive hormones secreted from the anterior pituitary?
FSH
LH
Prolactin
During follicle development what causes the switch from negative to positive feedback of oestrogen on hypothalamus hormones?
Prolonged oestrogen
Oestrogen acts on alpha and beta receptors
GnRH neurones have beta receptors which mediate negative feedback on tonic GnRH release
GnRH have no alpha receptors but intermediate neurones with alpha neurones synapse to GnRH increasing GnRH pulses
Where are oestrogen, progesterone and inhibin secreted from?
Ovaries
What hormone does the hypothalamus secrete?
GnRH
How are FSH and LH released and what triggers it?
Tonic or surge release
GnRH induces it
Describe the pulsatile release of GnRH in the follicular and luteal phases
Follicular phase- increased frequency of GnRH pulses increases FSH and LH. FSH promotes follicle development so increased oestrogen by follicle
Luteal phase- reduces frequency of GnRH pulses so fall in FSH and LH. Increased progesterone from corpus luteum
What are the effects of oestrogens in the female reproductive system?
Oviduct- increased secretions, cilia and muscle activity
Cervix- cervical muscle relaxes, thinner alkaline secretions
Mammary glands- primes glandular tissue
Uterus- increases myometrium activity, number and size of glands and watery secretion and induced synthesis of progesterone receptors
What are the effects of progesteragens in the female reproductive system?
Oviduct- reduced secretions, muscle activity and cilia
Cervix- firmer cervix, thick acidic secretions
Mammary glands- glandular tissue growth
Uterus- reduced myometrium activity, glandular growth, thick secretions
What is the main hormonal control of the female reproductive system and how does it change?
FSH and LH
Prolactin switches it to progesterone
Explain how ovulation takes place
LH surge induces protease and collagenous activity in follicles
Increase in follicular activity
Granulosa cell layer thins
Stigma forms then ruptures releasing oocyte
How does the oocyte move down the uterine tube?
Ampulla- cilia
Isthmus- muscular contractions
What lines the uterine tube?
Ciliated and secretory epithelium
Where is the oocyte held until fertilisation and how does this happen?
At the ampulla isthmus junction by a physiological sphincter which only opens at high progesterone
How does the corpus luteum form?
Follicle collapses after ovulation
Granulosa and theca interna cells form the corpus luteum
Blood vessels invade theca
Cells switch to progesterone synthesising by two cell hypothesis
Cells stop dividing and undergo luteinisation to transform to lutein cells
Why is luteolysis needed?
When no pregnancy to allow another follicular phase to occur by reducing levels of progesterone
List the components of the male reproductive system
Testes Epididymis Ductus deferens Urethra Seminal vesicles Prostate gland Bulbourethral glands Penis
What are the functions of the testes?
Hormone production
Sperm production
Define spermatogenesis
Development of sperm cells
Where does spermatogenesis take place?
Seminiferous tubules with steroli cells providing nourishment
What is the purpose of the blood testes barrier in spermatogeneses?
Mitosis occurs below and meiosis occurs above junction so the sperm are protected from the immune system
Allows different seminiferous tubular fluid environments for late stages of spermatogenesis
How does sperm move through the epididymis?
Cilia and contraction of smooth muscle, sensitive to oxytocin
What are the functions of the epididymis?
Mature sperm to make motile and fertile
Concentrate sperm
Store in tail for release
Phagocytose in times of abstinence
Define spermeogenesis
Non-motile round cells converting to motile cells
What takes place in spermeogenesis?
Condensation of nucleus
Acrosome formation
Flagellogenesis
What is the morphology of sperm?
Head- highly condensed chromatin covered in acrosomal cap
Midpiece- mitochondria spiral
Tail- 9+2 microtubule arrangement responsible for motility
How does sperm have motility?
Motor protein dynein attach to adjactent microtubules with Ca2+ dependent ATPase activity
ATP hydrolysis causes microtubules to slide past each other causing flagella to bend
Sequential activation generates wave of bending
How long do spermatogenesis cycles take?
64 days
What secretes testosterone?
Leydig cells in seminiferous tubules interstitium
How is testosterone mainly found in plasma?
Bound to albumin or sex hormone binding protein
What are the roles of hormones in spermatogenesis?
Androgen binding protein is in adluminal space
Testosterone alone is not enough for spermatogenesis
GnRH releases FSH
FSH acts on steroli cells and binds to androgen binding protein
Spermatogenesis increased
Vitamin A also aids the process
What are the effects of testosterone?
Testes development and descent Genital tract development Enlarging genital tract Libido Masculine behaviour Secondary sexual characteristics Maintain sexual activity Spermatogenesis
How does sperm travel along the ductus deferens?
Muscular contractions
What is the components of seminal fluid?
High fructose concentration Buffer Glycoprotiens to coat sperm head Coagulants to plug further sperm penetration Leukocytes
Describe how errection happens
Parasympathetic reflex response dilates arteries
Veins get compressed
Penis becomes turgid
What arteries are involved in errection?
Helicine artery, branches of main artery
What substances/molecules causes dilation of helicine artery in erection?
Acetylcholine
Vasoactive peptide
Nitrous oxide
Describe how seminal emission happens
Sympathetic outflow to epididymis tail, ductus deferens and accessory glands increase
Contents get expelled into pelvic urethra
Stimulates for ejaculation
How does ejaculation take place?
Rhythmic contractions of urethra under somatic control causes ejaculation
What causes uneven mixing of semen?
Emission and ejaculation overlap
How do cervical secretions vary under oestrogens and progesterone?
Oestrogen- water alkaline fluid so hospitable to sperm
Progesterone- thick, acidic, impermeable secretions
How does sperm move into the uterus from the vagina and once in the vagina?
Uterine muscular contractions causing negative pressure pulling
Then move by own propulsion aided by current of fluid by uterine cilia
How do sperm move alone uterine tube?
Swim to isthmus ampullary junction attracted by chemical from oocyte
How does capacitation happen and why is it important?
Exposure of sperm to female reproductive tract changes sperm membrane to enable acrosome reaction and activate tail for whiplash motions
Needed for fertilisation
How is the corpus luteum lifespan increased to extend past the time it takes for implantation?
Unimplanted embryo extends by producing HCG that prevent luteolysis until placenta is established the life to maintain progesterone levels
What are the endometrium requirements for implantation?
Primed by oestrogens to thicken lining
High progesterone to limit contractions
What are the hormones produced by the placenta?
HCG- prolongs corpus luteum lifespan
Oestrogen- stimulates uterine growth and development
Progesterone- stabilises uterus
Human placental lactogen- growth hormone like activity
What are the changes that happen to the human body in pregnancy?
Uterus expands x1000
Blood volume, heart workload and kidney filtering increases
Average weight gain 10-15kg
What are the stages of labour?
Stage 1-uterine contractions, foetus positions, cervix dilates and softens
Stage 2- foetus expelled, uterus sensitive to oxytocin
Stage 3- placenta expelled, uterus contracts to prevent blood loss
What is needed for parturition to take place?
Softened cervix
Coordinated contractions of myometrium
What stimulates lactation?
Sudden decline in oestrogen, progesterone
Increased prolactin by suckling
Describe the structure of mammary glands
Glandular tissue arranged in alveoli and clusters
Milk secreting cells are single epithelial layer surrounded by myoepithelial cells to contract for secretion
What initiates milk ejection reflex?
Suckling
How is milk production and excretion maintained?
Production- prolactin and suckling
Excretion- oxytocin or conditioned relflex without stimulation
What is the ideal contraceptive?
100% effective Safe Effective Reversible No side effects Easy to use
How do hormonal contraceptives work?
Target negative feedback of hypothalamic pituitary ovarian axis
Why can lactational amenorrhea happen?
Suckling supresses follicular development as it disrupts pulsatile GnRH so there is no LH surge interfering with corpus luteum
How does the combined pill work?
Negative feedback on gonadotrophs so inhibit production of LH and FSH so ovulation inhibited
How does progesterone pill work?
Cervical mucus stays hostile
What are the main causes of infertility?
Declines after 35 years old Female tract disorders Ovulation disorders Poor sperm quality unexplained
What are the dangers of assistive fertility techniques?
Multiple babies
Ovarian hyperstimulation
Low birth weights
Congenital abnormalities
How do fertility drugs work?
Anti-oestrogens block oestrogen receptors in hypothalamus so LH and FSH increases allowing ovulation
Gonadotrophins- stimulate follicular growth
Explain the process of IVF
Natural cycle supressed with GnRH agonist to prevent LH surge and early ovulation
Ovarian hyperstimulation by FSH then LH injections to mature follicles
Eggs collected, incubated and fertilised
Implanted at 4 cell stage
Progesterone given to help
Define luteolysis
Cell death of corpus luteum cells
Define decidual cell reaction
Membranes break down where they come into contact with each other to form single multinucleated cell
