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Human Phys
Reproductive physiology II
| Question | Answer |
|---|---|
| Female reproductive system | Gonads: Ovaries Reproductive tract/internal genitalia: Fallopian/uterine tubes/oviducts Uterus Cervix Vagina |
| Female reproductive system | External genitalia/vulva: Mons pubis Labia majora Labia minora Clitoris Vestibule of vagina Vestibular glands Breasts |
| Ovarian Macrostructure | Divided into two main sections Ovarian cortex Contains the developing oocytes Ovarian medulla Contains vasculature Surrounded by a thick connective tissue layer (tunica albuginea) covered by a simple squamous epithelium (mesothelium) |
| Ovarian function | Oogenesis Production, maturation and ovulation of eggs Maturation of eggs occurs within a follicle; referred to as folliculogenesis Reproductive hormone synthesis Sex steroids – estrogen and progesterone Protein hormone inhibin |
| Oogenesis | Oogonia undergo mitosis during the first 7 months of gestation 2-4 million primary oocytes present at birth 200,000 to 400,000 oocytes remaining by puberty |
| Oogenesis | Only ~400 secondary oocytes ovulated throughout lifetime Meiosis I completed just before ovulation Meiosis II is completed after fertilization |
| Primordial Follicles | Primordial follicles are formed during fetal life Consist of a primary oocyte + a single layer of squamous epithelial cells (granulosa/follicular cells) |
| Primordial Follicle | Form a resting pool of follicles that are recruited for growth in postnatal life Arrested in the first meiotic division |
| Primary follicles | Some primordial follicles develop further throughout infancy, childhood and menstrual cycling Granulosa cells become cuboidal and begin to proliferate |
| Primary follicles | Zona pellucida develops from glycoproteins secreted by granulosa cells Granulosa cells remain in contact with oocyte via gap junctions Late stage may also be referred to as preantral |
| Secondary follicles | Also referred to as early antral follicle Fluid-filled antrum develops within the granulosa cells Granulosa cell population, zona pellucida and oocyte all increase in size Theca cells differentiate from the surrounding connective tissue stroma |
| Antral follicles | Also referred to as tertiary or Graffian follicles 1.5 cm structure balloons out on the surface of the ovary Antrum makes up most of the follicle |
| Antral follicles | Granulosa cells project into the antrum (“cumulus oophorus”) and surrounding the oocyte (“corona radiata”) Ovulation occurs when the walls of antral follicle and ovary rupture due to enzymatic digestion |
| Corpus Luteum/Corpus Albicans | Following ovulation, the remaining granulosa and theca cells form the corpus luteum → luteal phase Corpus luteum secretes large amount of estrogen and progesterone |
| Corpus Luteum/Corpus Albicans | Unless fertilization occurs, corpus luteum undergoes apoptosis after ~10-14 days and forms corpus albicans scar tissue |
| Ovarian Follicular Dynamics | Follicular development occurs in waves over the menstrual cycle Recruitment: 10-25 preantral (late primary) and early antral (secondary) follicles develop into larger follicles Occurs during both the follicular phase and the luteal phase |
| Ovarian Follicular Dynamics | Selection: One of the larger antral follicles is selected for further development Two follicles may be selected in the case of fraternal (dizygotic) twins Occurs 1 week into cycle Non-dominant follicles undergo atresia |
| Ovarian Follicular Dynamics | Further follicular growth and ovulation following the gonadotrophin surge |
| Endocrine Regulation | HPG axis is responsive to both negative and positive feedback Negative feedback Low levels of estrogen Estrogen in the presence of progesterone Inhibin |
| Endocrine Regulation | Positive feedback High levels of estrogen Interaction among hormones enable a self-cycling pattern (i.e., menstrual cycle) to occur |
| Follicular Phase Endocrine Regulation | Early-mid follicular phase ↑ FSH Oocyte recruitment Granulosa cell survival and proliferation → estrogen synthesis Antrum enlargement Emergence of dominant follicle |
| Follicular Phase Endocrine Regulation | Granulosa cells are stimulated by both FSH and LH Estrogen synthesis → negative feedback regulation of FSH Late follicular phase Estrogen positive feedback regulation |
| Follicular Phase Endocrine Regulation | ↑ LH → Completion of meiosis I + ovulation + corpus luteum formation ↑ FSH and progesterone |
| Follicular Phase Endocrine Regulation | Mid-late follicular phase: Uterine proliferative phase Endometrial and myometrial proliferation Progesterone receptor upregulation in endometrium |
| Luteal Phase Endocrine Regulation | ↑ progesterone and estrogen ↑ in body temperature (~0.5°C) Negative feedback regulation ↓ LH maintains corpus luteum Uterine secretory phase ↑ glycogen + enzymes necessary for embryo implantation ↓ myometrial contractions |
| Luteal Phase Endocrine Regulation | Corpus luteum degeneration Release of negative feedback control ↓ progesterone and estrogen → prostaglandin secretion → vasoconstriction and uterine contractions → menstruation (i.e., shedding of endometrium) |
| Reproductive Onset and Cessation | Puberty Activation of kisspeptin neurons in hypothalamus → ↑GnRH secretion Attainment of sufficient energy fat stores → ↑leptin → ↑GnRH secretion |
| Reproductive Onset and Cessation | Menopause Normal function of hypothalamus and pituitary gland Failure of ovary to respond due to oocyte depletion Loss of estrogen |
| Reproductive Onset and Cessation | Loss of temperature regulation in hypothalamus Decrease in bone mass Breast and genital organ atrophy Increased cardiovascular disease risk |
| Relevant Research Connection | How is the dominant follicle selected? Timing Coincides with the drop in FSH levels Can be delayed with exogenous FSH LH responsiveness |
| Relevant Research Connection | Number of LH receptors Can a subordinate follicle achieve dominance? Removal of the dominant follicle Exogenous FSH |
| Fertilization and Implantation | Oocyte is swept into fallopian tube following ovulation; takes about 4 days to reach the uterus Fertilization occurs in the fallopian tube Oocytes remain viable for 1-2 days |
| Fertilization and Implantation | Several regulated steps Capacitation Acrosome reaction Fast block to polyspermy Cortical reaction Meiosis II Increasing progesterone secretion prevents uterine contractions and allows conceptus to enter Implantation occurs ~7 days after ovulation |
| Placentation | The placenta is the organ of fetal-maternal exchange Nutrients Waste Hormones and growth factors Gas Drugs Attached to the fetus via the umbilical cord Well-established 5 weeks after implantation |
| Pregnancy Sex Steroid Production | Estrogen and progesterone increase throughout pregnancy Estrogen stimulates growth of uterine muscle mass Progesterone (promotes gestation) inhibits uterine contractility |
| Pregnancy Sex Steroid Production | Corpus luteum supplies nearly all estrogen and progesterone for first 2 months Persistence of CL due to human chorionic gonadotropin (hCG) Secreted by trophoblast cells from embryo invading endometrium |
| Pregnancy Sex Steroid Production | Very similar activity to LH Stimulates gonadal steroidogenesis → negative feedback regulation |
| Pregnancy Sex Steroid Production | Placenta secretes estrogen and progesterone from 3rd month of gestation Coincides with decrease in hGC production and corpus luteum regression |
| Pregnancy Sex Steroid Production | Converts androgens secreted by ovary and adrenal cortex into estrogen via aromatase Maintains negative feedback inhibition on HPG axis |
| Parturition Hormonal Regulation | Parturition: delivery of the infant and placenta at ~38 weeks of gestation Uterine smooth muscle contraction Estrogen Connexin synthesis → gap junctions Oxytocin receptor synthesis Prostaglandins Progesterone withdrawal not necessary |
| Parturition Hormonal Regulation | Cervical ripening (softening) Estrogen and prostaglandins Initiation Fetal ACTH (adrenocorticotropic hormone) |
| Lactation | Ductal and alveoli cell proliferation occurs during late pregnancy Ductal proliferation initiated during puberty Alveoli cell proliferation occurs during luteal phase under influence of progesterone |
| Lactation | Prolactin stimulates milk production Delivery of the placenta is required for milk production Removal of estrogen and progesterone inhibition |
| Lactation | Oxytocin stimulates milk ejection Milk ejection inhibits milk production; must occur separately |
| Fetal to Neonate Transition | Immediately following birth, adaptions in two organ systems necessary for survival Respiratory system Cardiovascular system |
| Fetal to Neonate Transition | Neonate must accommodate for loss of gas exchange from placenta Further changes in endocrine system, metabolism and thermoregulation |
| Neonatal Respiratory System | Clearance of lung fluid Uterine contractions Sodium ion channels Synthesis triggered by cortisol secretion |
| Neonatal Respiratory System | Surfactant secretion Coats the alveoli to decrease surface tension at the air-liquid interface |
| Neonatal Respiratory System | Normally produced by 24-28 weeks of gestation; enough produced by week 34 for normal breathing Prevents alveolar collapse after exhalation Typical cause of respiratory distress syndrome |
| Neonatal Cardiovascular System | Three major changes: Closure of the ductus venosus: Returns blood from the abdomen Closure of the foramen ovale: Hole between left and right atria Closure of the ductus arteriosus: Connects aorta to pulmonary artery |
| Neonatal Cardiovascular System | Alveoli open in first breath: Decrease pressure on right side Increase pressure on left side Assists in closure of fetal structures |
Created by:
reub8n
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