Ch. Seventeen: Reproductive System Flashcards
(48 cards)
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
2
Q
Meiosis
A
- half set of genetic info
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
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
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
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
7
Q
Spermatogenesis 3 stages
A
- mitotic proliferation:
- 2 mitotic divisions= 4 identical primary spermatocytes - meiosis:
- 2 meiotic divisions
- 16 spermatozoa result from each spermatogonium - packaging:
- not built to last
- 64 days from spermatogonia to sperm
- 30 million sperm/day
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)
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
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
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
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
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
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
15
Q
Accessory Glands
A
- Seminal vesicles (2)
- supply fructose for energy
- supply prostaglandins: promote smooth muscle motility in reproductive tracts
- secrete fibrinogen - Prostate Gland
- ejaculatory duct and urethra
- contributes alkaline fluid that neutralizes acidic vaginal secretions
- provides clotting enzymes and fibrinolysin - Bulbourethral glands
- lubricating mucus
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
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
18
Q
Ovaries
A
- primary female reproductive organs
- produce ova (oogenesis)
- secrete female sex hormones
- estrogen and progesterone
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
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
Follicular Phase
- 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
Luteal Phase
- 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
FSH and LH in Ovarian Cycle
- 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
Feedback Control of FSH and Tonic LH During Follicular Phase
- estrogen primarily inhibits FSH from anterior pituitary
- not on LH secretion
- LH rise continues during follicular phase
- estrogen alone cannot inhibit LH secretion
29
Control of Ovulation
- ovulation and subsequent lutinization of the ruptures follicle are triggered by an abrupt, massive increase in LH secretion
- LH surge
30
Mid-Cycle LH surge
1. halts estrogen synthesis by follicular cells
2. reinitiates meiosis: meiosis 1 completes
3. follicular cells into luteal cells
31
Control of the Corpus Luteum
- 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
Menstrual Cycle
- 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
Menstraul Phase
- 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
Proliferative Phase
- 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
Secretory Phase
- 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
Fertilization
- 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
First Sperm to Reach Ovum
- 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
Embryonic Development
- 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
The Planceta
- 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
Placenta Development
- 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
Placenta Function
- 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
Development
- 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
After Implantation
- 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
Placental Hormone Secretion
- 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
Gestation
- 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
Paturition
- 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
Preparation of the Breasts for Lactation
- 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
Lactation
- 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
