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Human Physiology 2 > Ch. Seventeen: Reproductive System > Flashcards

Ch. Seventeen: Reproductive System Flashcards

1
Q

Reproductive Cells

A

body (somatic) cells:

  • 46 chromosomes (diploid)
  • 23 homologous paris

gametes (sperm and egg):

  • 23 chromosomes (haploid)
  • only one member of each homologous pair of chromosomes
  • gametogenesis is accomplished by meiosis

autosomes;
- 22 pairs which code for general human characteristics and specific traits such as eye colour

sex hormones:

  • remaining pair of chromosomes
  • 2 genetically different types: larger X chromosome and smaller Y chromosome
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2
Q

Meiosis

A
  • half set of genetic info
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3
Q

Gametogenesis

A
  • nuclear division in the specialized case of gametes is accomplished by meiosis
  • only half set of genetic info is distributed to each of the four new daughter cells
  • more than 8 million different mixtures of the 23 paternal and maternal chromosomes are possible
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4
Q

Male Reproductive Physiology

A

testes:
- descent is usually complete by 7th month of gestation
- descend into scrotum: cooler enviro essential for spermatogenesis
- perform dual function:
- sperm produced in seminiferious tubules
- secrete testosterone produced in Leydig cells and lie in connective tissue between seminiferious tubules

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5
Q

Spermatogenesis

A
  • Sertoli cells= support for sperm
  • Leydig cells= testosterone
  • results in many highly specialized, mobile sperm
  • from undifferentiated diploid germ cells (spermatogonia)
  • into haploid spermatozoa
  • at puberty
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6
Q

Testosterone

A
  • steroid hormone derived from cholesterol
  • 5 categories of testosterone effects:
  • reproductive before birth: masculinizes reproductive tract; promotes descent of the testes into the scrotum
  • sex-specific tissues after birth: growth and maturation at puberty; esstetial for spermatogenesis; maintains reproductive tract
  • other reproductive-related effects: develops sex drive; controls gonadotropin hormone secretion
  • secondary sexual characterisitics: hair growth; voice deepens; muscle growth
  • non-reproductive actions: protein anaoblic effect; bone growth at puberty; induce aggressive behaviour
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7
Q

Spermatogenesis 3 stages

A
  1. mitotic proliferation:
    - 2 mitotic divisions= 4 identical primary spermatocytes
  2. meiosis:
    - 2 meiotic divisions
    - 16 spermatozoa result from each spermatogonium
  3. packaging:
    - not built to last
  • 64 days from spermatogonia to sperm
  • 30 million sperm/day
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8
Q

Spermatozoan Packaging

A
  • remains closely associated with Sertoli cells throughout development
  • consists of 4 parts: head (DNA), acrosome (penetrate ovum), midpeice (mitochondria) and tail (mobility)
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9
Q

Sertoli Cells

A
  • located in seminiferous tubules
  • secretes fluid which flushes released sperm from tubule into epididymis for storage and additional processing (maturation)
  • site of action to control spermatogenesis
  • release inhibin
  • acts in negative-feedback fashion to regulate FSH secretion
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10
Q

Control of Testicular Function

A
  • testes controlled by 2 gonadotropic hormones from anterior pit.
  • LH and FSH
  • testosterone is essential to maintaining spermatogenesis in the adult male and is under the direct control of LH
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11
Q

Gonadotropic Hormones

A
  • GnRH- secreting neurones AP bursting activity (90mins)
  • release LH and FSH from same cells in anterior pit.
  • L and FSH also show pulsatility- rapid rise and slow decrease over 90 mins
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12
Q

GnRH

A
  • predominant feedback of testosterone on GnRH
  • also on LH-producing cells of anterior pituitary
  • inhibin inhibits FSH release
  • FSH acts on Sertoli cells to stimulate speratogenesis
  • GnRH:
  • LH and FSH are too low to stimulate testosterone production pre-puberty
  • from 8-12 years more GnRH released- onset of puberty
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13
Q

Maturation of Sperm

A
  • seminiferious tubules to epididymis to ductus deferenes
  • pressure difference due to Sertoli cells continually secreting fluid
  • maturation of sperm: motility and fertilization by testosterone in epididymis
  • concentration of sperm in ductus deferens
  • peristaltic contractions
  • storage of sperm for several days
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14
Q

Functions of Accessory Sex Glands

A
  • during ejaculation
  • sperm are mixed with secretions released by accessory glands
  • secretions make up most of semen volume
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15
Q

Accessory Glands

A
  1. Seminal vesicles (2)
    - supply fructose for energy
    - supply prostaglandins: promote smooth muscle motility in reproductive tracts
    - secrete fibrinogen
  2. Prostate Gland
    - ejaculatory duct and urethra
    - contributes alkaline fluid that neutralizes acidic vaginal secretions
    - provides clotting enzymes and fibrinolysin
  3. Bulbourethral glands
    - lubricating mucus
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16
Q

Erection

A
  • sexual excitement causes dilation of small arteries to compartments
  • enlarged with blood at high pressure- erection
  • mediated by neural inputs:
    NO from PNS and decreased sympathetic
    exception to rule of PNS causing blood vessel dilation
  • contains 3 cylindrical, vascular compartments
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17
Q

Ejaculation

A
  • spinal reflex
  • efferent SNS
  • afferent pathways from penile mechanoreceptors leading to contraction of smooth muscle in: epididymis, vas deferns, ejaculatory ducts, prostate, seminal vesicles, urethra
  • contraction of urethral SM and skeletal muscle at base of penis
  • associated with intense pleasure- orgasm
  • average 2.5- 3 mLs containing 60-100 million
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18
Q

Ovaries

A
  • primary female reproductive organs
  • produce ova (oogenesis)
  • secrete female sex hormones
  • estrogen and progesterone
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19
Q

Estrogen

A
  • essential for ova maturation and release
  • establishment of female secondary sexual characterisitics
  • essential for transport of sperm from vagina to oviduct
  • contributes to breast development in lactation
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20
Q

Progesterone

A
  • suitable enviro for nourishing a developing embryo/fetus

- contributes to breasts ability to produce milk

21
Q

Steps of Gametogenesis

A
  • oogenesis
  • identical steps of chromosome replication and division during gamete production in both sexes
  • timing and end result are very different
22
Q

Oogonia

A
  • undifferentiated primordial germ cells in fetal ovaries
  • divide mitotically (2 rounds)
  • during last part of fetal life begin early steps of first meiotic division but do not complete it
  • primary oocytes: contain diploid number of 46 replicated chromosomes; remain in meiotic arrest fro years until they are prepared for ovulation
23
Q

Oogenesis

A

primary oocyte: surrounded by single layer of granulosa cells
- oocyte + granulosa cells = primary follicle

primary follicle: after development starts there are 2 possible fates

  • reach maturity and ovulate
  • degenerate to form scar tissue (atresia)
  • between puberty and menopause follicules develop into secondary follicles on cyclic bases
  • just before ovulation: primary oocyte completes first meiotic division
  • first polar body (non-functional)
  • secondary oocyte (ovulated)
  • just after fertilization (sperm entry)
  • sperm triggers second meiotic division
  • secondary polar body (haploid is non functional)
  • mature haploid ovum which unites with haploid sperm cell during fertilization
24
Q

Ovarian Cycle

A
  • average ovarian cycle lasts 28 days
  • normally interrupted only by pregnancy
  • finally terminated by enopause
  • follicular phase (maturing follicles)
  • luteal phase (corpus luteum)
25
Q

Follicular Phase

A
  • operates first half of cycle
  • oocyte inside follicle enlarges
  • Granulosa cells infollicle secrete increased amounts of estrogen
  • rapid follicular growth continues during follicular phase
  • one follicle usually grows more rapidly and matured about 14 days onset of follicular development
  • follicule ruptures called ovulation
26
Q

Luteal Phase

A
  • last 14 days
  • old follicular cells forms corpus luteum
  • becomes fully functional within 4 days after ovulation
  • progesterone and estrogen secretion
  • continues to increase in size for another 4-5 days
  • if released ovum is not fertalized and does not inplant, corpus luteum degenerates within 14 days after its formation
27
Q

FSH and LH in Ovarian Cycle

A
  • FSH rises in follicular phase; rise in estrogen feeds back to inhibit FSH secretion which declines as follicular phase proceeds
  • LH rises in follicular phase; as it peaks in mid-cycle, it triggers ovulation; LH surge
  • estrogen output decrease and mature follicle is converted to a corpus luteum
  • corpus leuteum secreted progesterone and estrogen during luteal phase
  • progesterone ouput inhibits release of FSH and LH (low LH degenerated corpus luteum)
  • FSH can start to rise again, initiating new cycle
28
Q

Feedback Control of FSH and Tonic LH During Follicular Phase

A
  • estrogen primarily inhibits FSH from anterior pituitary
  • not on LH secretion
  • LH rise continues during follicular phase
  • estrogen alone cannot inhibit LH secretion
29
Q

Control of Ovulation

A
  • ovulation and subsequent lutinization of the ruptures follicle are triggered by an abrupt, massive increase in LH secretion
  • LH surge
30
Q

Mid-Cycle LH surge

A
  1. halts estrogen synthesis by follicular cells
  2. reinitiates meiosis: meiosis 1 completes
  3. follicular cells into luteal cells
31
Q

Control of the Corpus Luteum

A
  • LH maintains the corpus luteum
  • LH stimulates ongoing steroid hormone secretion by this ovarian structure
  • under influence of LH, the corpus luteum secretes both progesterone and estrogen
  • progesterone most abundant hormonal product
32
Q

Menstrual Cycle

A
  • reflects hormonal changes during ovarian cycle
  • averages 28 days
  • menstraul bleeding once during each cycle
  • consists of 3 phases: menstrual, proliferative, and secretory/progestational
33
Q

Menstraul Phase

A
  • discharge of blood and endomtrial debris from vagina
  • 1st day of menstruation = start of new cycle
  • coincides with end of ovarian luteal phase and onset of follicular phase
  • release of uterine prostaglandin:
  • causes vasoconstriction of endometrial vessels; distrupts blood supply and causes death of endometrium
  • stimulates mild rhythmic contractions of uterine myometrium; helps expel blood and endometrial debris from uterine cavity out through vagina
34
Q

Proliferative Phase

A
  • begins concurrent with last portion of ovarian follicular phase
  • endometrium repairs itself and proliferate under influence of estrogen from newly forming growing follicles
  • estrogen-dominant proliferative phase lasts from end of menstruation to ovulation
  • peak estrogen levels trigger LH surge responsible for ovulation
35
Q

Secretory Phase

A
  • uterus enters this phase after ovulation when new corpus luteum is formed
  • corpus luteum secretes large amounts of progesterone and estrogen
  • progesterone converts endometrium to highly vascularized, glycogen-filled tissue
  • endometrial glands actively secrete glycogen
  • if fertilization and implantation do not occur corpus luteum degenerates and new follicular phase and menstrual phase begin once again
36
Q

Fertilization

A
  • oviduct; occurs in upper third of oviduct
  • must occur within 24 hours after ovulation
  • sperm survive about 48 hours
  • can survive up to 5 days in female reproductive tract
37
Q

First Sperm to Reach Ovum

A
  • triggers chemical change in ovum’s surrounding membrane
  • outer layer impermeable to entry of any more sperm
  • head of fused sperm gradually pulled into ovum’s cytoplasm
  • within hour, sperm and egg nuclei fuse; fertilized ovum = zygote
  • fuses with plasma membrane of ovum and triggers completion of meiosis
38
Q

Embryonic Development

A
  • fertilized ovum divides mitotically
  • within week grows and differentiates into blastocyst capable of implantation
  • blastocyst implants in endometrial lining by means of enzymes released by trophoblasts
  • enzymes digest endometrial tissue and carve hole for implantation
  • release nutrients from endometrial cells for use by developing embryo
39
Q

The Planceta

A
  • after implantation, plancenta develops
  • acts as transient, complex endocrine organ that secretes essential pregnancy hormones
  • hCG: maintains corpus luteum until placenta takes over function in last two trimesters
  • estrogen: essential for maintain normal pregnancy
  • progesterone: essential for maintain normal pregnancy
40
Q

Placenta Development

A
  • finger-like projections of chorionic tissue extend into the pools of maternal blood
  • developing embryo sends out capillaries into chorionic projections to form placental villi
  • inner cell mass forms a fluid-filed amniotic cavity
  • amniotic sac or amnion
  • amniotic fluid
41
Q

Placenta Function

A
  • maternal and fetal blood separated but exchange materials
  • umbilical vein carry oxygen and nutrient-rich blood from placenta to fetus
  • umbilical arteries carry waste products and low oxygen content to placenta
42
Q

Development

A
  • placenta acts as an endocrine organ
  • human chorionic gonadotropin (hCG)- pregnancy test hormone (1st trimester), trophoblast, strongly stimulates steroid hormone from corpus luteum
  • LH-like
  • estrogen
  • progesterone
43
Q

After Implantation

A
  • hCG: maintains corpus luteum- sorpus luteum of pregnancy; placenta takes over function in last two trimesters
  • Estrogen: essential for maintaining normal pregnancy- growth of uterine muscle mass
  • Progesterone: essential for maintaining normal pregnancy- inhibits uterine contractility
44
Q

Placental Hormone Secretion

A
  • in 2nd and 3rd trimester placenta produces estrogen and progesterone
  • corpus luteum of pregnancy degenerates
  • estrogen: essential for maintaing normal pregnancy- growth of uterine muscle mass
  • progesterone: essential for normal preg.- inhibits uterine contractility
  • both important for mammary gland development
45
Q

Gestation

A
  • about 38 weeks from conception
  • physical changes within mother to meet demands of preg.:
  • uterine and boobs enlargement, volume of blood increases 30%, weight gain, resp. increase 30%, urinary input increases, kidney’s excrete add. wastes, nutriontal requirements increase
46
Q

Paturition

A
  • dilation of cervical canal
  • breakdown of collagen fibres
  • relaxin
  • contraction of uterine myometrium that are sufficiently strong to expel fetus
  • hormones: oxytocin, estrogen, and DHEA
  • once contractions begin at labour onset, positive-feedback increases force
  • pressure of fetus against cervis reflexly increases oxytocin secretion
  • role of oxytocin; stronger contractions and positive-feedback until delivery is complete
47
Q

Preparation of the Breasts for Lactation

A
  • during gestation placental estrogen and progesterone promote development of mammary glands
    BUT inhibits prolactin action on mammary glands
  • prolactin stimulates milk by alveolar cells and withdrawal of placental steroids at parturition initiates lactation
48
Q

Lactation

A
  • sustained by suckling
  • triggers release of oxytocin and prolactin
  • oxytocin squeeze secreted milk out through ducts
  • prolactin stimulates secretion of more milk to replace milk ejected as baby nurses

Human Physiology 2 (10 decks)

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