Reproduction and development Flashcards
organs of the reproduction system
they are all organs involved in mating, gametogenesis, or other functions involved in producing offspring
these include:
-gonads
-accessory reproductive organs
gonads:
-testes
-ovaries
have 2 main functions
-produce gametes
-secrete sex hormones
components of the reproductive system
sex hormones:
-testes; androgens
-ovaries; oestrogen’s and progesterone
-differing levels of these steroids are found in all people
-adrenal cortex also produces androgens
accessory reproductive organs
-organs of the reproductive tract: transport of gametes
-glands: secrete fluids into reproductive tract
state the events following feritilisation
After fertilisation: pregnancy or gestation
First two months: embryo
After two months: fetus
About nine months (40 weeks): parturition or birth
Chromosomes determine whether fetus develops ovaries or testes: sex determination
Y chromosome: srY gene (sex-determining region of the Y chromosome)
If srY gene present: testes
If srY gene absent: ovaries
srY gene
Codes for testis-determining factor
If present: testis-determining factor causes fetus to develop testes
If absent: ovaries develop
foetal development
sex differentiation is controlled by hormones
in the first 2 weeks, the embryo is sexually indifferent
Wolffian ducts (precursor to male tract)
Müllerian ducts (precursor to female tract)
if testes are present:
testosterone is released, stimulating the. development of the Wolffian ducts
Müllerian-inhibiting hormone degenerates Müllerian ducts
no testes present
the horns are absent
Wolfian ducts regress
Müllerian ducts develop
patterns of humans reproductive cycle
1- adolescence (prior to 10-14 years)
inability to reproduce
2-puberty (starts at 10-14 years)
-begins development of sexual maturation
-reproductive organs mature
-secondary sexual characteristics develop
3-sexual maturation (late teens onwards)
-female reproductive system cycles
-female loses ability to reproduce at approximatelyage 45–50
-menopause: loss of female reproductive capacity
-male retains ability to produce sperm (age related decline in quality)
testes and associated structures
Gonads
250–300 compartments
Seminiferous tubules
Sperm production
Leydig cells (interstitial cells)
Secrete testosterone
Sertoli cells (epithelial cells)
Support sperm development
Sertoli cells
they support sperm development
they secrete luminal fluid
they secret androgen-binding protein
androgen buffer that helps maintain a steady level of androgen in the lumen
secrete hormones that stimulate spermatogenesis
hormone regulation in testes
Gonadotropin releasing hormone (GnRH)
-Hypothalamus
-Gonadotropins by anterior pituitary gland
-FSH: stimulates gametogenesis
-LH: stimulates androgen secretion
Blood levels of sex hormones
-Fairly constant on a short-term basis
-Prepubescent → low blood levels
-Puberty and adulthood → high blood levels
functional anatomy of the ovary
follicles contain one ovum each
-develop in ovary
-start as primordial follicles
–oocyte
–surrounded by granuloma cells
granuloma cells are target cells of oestrogen and FSH
secrete chemical messengers in response to these hormones
secrete oestrogen’s
the actions of granuloma cells is analogous to the action Sertoli cells.
later development, some granuloma cells become theca cells
functional anatomy of the uterine tubes (fallopian tubes)
ova is transported from ovaries to uterus
site of fertilisation
infundibulum and fimbriae; pick up released ovum
movement of ovum through uterine tube
-initially: peristaltic contractions
-mostly: ciliary actions
-duration: 4 days to uterus
describe the menstrual cycle
Repeated changes in the ovary and uterus through time
Includes two sub-cycles
Ovarian cycle- governs the preparation of endocrine tissues and release of eggs
Uterine cycle- governs the preparation and maintenance of the uterine lining
Caused by changes in estrogen and progesterone concentration
describe the Ovarian cycle: Phases of menstruation
split into 2 phases
1- follicular phase
menstruation-> ovulation
follicular phase commences with start of menstruation and ends with ovulation
lasts approx 14 days
2- luteal phase
ovulation-> before menstruation
lasts approx 14 days
describe the follicular phase
1- FSH and oestrogen’s stimulate follicle growth and development
,, a few follicles develop from primordial follicles,,
2- Oocyte grows; granuloma cells proliferate
3- dominant follicle continues development; remaining follicles regress, Graafian follicle=mature follicle
GnRH surge causes LH surge
(LH surge triggers ovulation and development of corpus luteum in luteal phase)
4- ovulation: wall of Graafian follicle ruptures
Oocyte is released and enters fimbrae (uterine tube)
describe the luteal phase
5- Ruptured follicle → gland = corpus luteum
Corpus luteum secretes estrogens and progesterone
6- Corpus luteum reaches maximum activity in 10 days, then degenerates (luteolysis)
Luteolysis → decreased estrogens and progesterone → menstruation (end of luteal phase)
If oocyte is fertilized, degeneration does not occur
describe the phases of the uterine cycle
occurs at the same time as the ovarian cycle
divided into 3 phases
menstrual phase- 天1-5
proliferative phase- 天5-14
secretory phase- coincides 跟 ovarian luteal phase
describe Uterine cycle: Menstrual phase
Menstrual phase (menses)
Shedding of uterine lining
Blood flow to tissue decreases
Tissues die, causing menstrual flow
caused by reduced blood flow to area
Hormonal control of menstruation
Triggered by decreased levels of estrogens and progesterone
Hormones levels decrease when corpus luteum degenerates
describe Uterine cycle: Proliferative phase
uterus prepares 为 fertilised ovum
-endometrial layers grows
- smooth muscle layer thickens
hormonal control 的 proliferative phase
-estrogens stimulate development的 uterine lining
describe Uterine cycle: Secretory phase
Secretory phase
- endometrium prepared for implantation
- blood supply increased
Cervical secretions are more sticky, forming a plug
describe Fertilisation of the oocyte and implantation
fertilisation usually takes place 在 uterine tube， takes 4日
implantation occurs 6-7日 post fertilisation：secretes enzymes
blastocyte attaches to endometrial lining
trophoblast penetrates endometrium
fertilisation
implantation
development
说说 development 从 embryo to foetus
Amnion (amniotic sac) contains amniotic fluid
Week 5: heart, spinal cord, and GI tract start to develop
Week 6: 心 beating
Week 8: lungs develop
Week 9: remaining organs develop
Week 10: size of kidney bean = fetus
说说 placenta development
fetal component
-chorionic villi
maternal component
- endometrial tissue
blood flow to placenta
-maternal uterine artery 和 vein
-fetal umbilical artery 和vein located in umbilical chord
-by 5 weeks， placenta is functioning，和心是beating
hormones在pregnancy
Estrogen
Growth of duct tissue in the breasts
Prolactin secretion
-breast enlargement and milk production
Growth and enhanced contractile responsiveness of smooth muscle in uterus; increases receptors for oxytocin
-Oxytocin
Progesterone
Growth of glandular tissue in the breasts
Maintenance of secretory-phase uterine conditions
Suppression of contractile activity of smooth muscle in uterus
what happens during delivery
also known as parturition
beginning of parturition
the cervix dilates
labour occurs; uterine contractions
parturition
baby‘s 头 wedges cervix open
baby 是 born 头-first
说说parturition
- weak uterine contractions
- pressure of fetus against cervix
- oxytocin secretion from posterior pituitary
- strengthen uterine contractions
from 4, either return back to 2., or go onto 5.
- parturition
describe lactation
Inhibition of lactation
Estrogen 和 progesterone
Stimulation of lactation
Prolactin stimulates milk synthesis
Oxytocin stimulates the milk ejection reflex
Colostrum
Watery milk produced in the first few days after birth
- Later 牛奶 more complex- inc growth factors, hormones, and antibodies
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