2.3 - sexual reproduction in humans Flashcards
list parts of female reproductive system + explain function
ovaries - produce egg cells in follicles
fallopian tubes - transports egg cell from ovary to uterus
uterus - where embryo develops
cervix - separates uterus from vagina, protects fetus
vagina - leads from cervix to outside of body
list parts of male reproductive system + explain function
testes - production of sperm cells + testosterone
vas deferens - carry sperm from testes to urethra
prostate gland - secretes alkaline fluid to counteract vaginal acidity
urethra - allows excretion of urine + semen from body
seminal vesicle - secretes fluid (proteins + fructose) to nourish sperm
penis - penetrates vagina, releases sperm
epididymis - stores sperm
scrotum - holds + maintains optimum temperature for testes
how does human body produce gametes
via gametogenesis
name 2 types of gametogenesis
- spermatogenesis
- oogenesis
what is spermatogenesis
gametogenesis in males resulting in production of spermatozoa
where does spermatogenesis take place
seminiferous tubules
outline stages of spermatogenesis
primordial germ cells → spermatogonia → primary spermatocytes → secondary spermatocytes → spermatic → 4 spermatozoa
what’s the germinal epithelium
surface layer of cells surrounding ovaries in females + testicles in males that’s involved in gametogenesis
how do primary spermatocytes form
- primordial germ cells divide by mitosis, forming spermatogonia
- growth period of spermatogonia w/out further division forms primary spermatocytes
how are spermatids formed
- primary spermatocytes divide in meiosis I to form haploid secondary spermatocytes
- secondary spermatocytes divide in meiosis II to form 4 haploid spermatids
how do spermatozoa form
spermatids differentiate to gain flagellum, acrosome, + many mitochondria
the 3 types of cells within testes
- spermatogonia
- sertoli cells
- interstitial cells (cells of leydig)
what are leydig cells
- cells located adjacent to seminiferous tubules in testes that secrete testosterone
- also called interstitial cells of leydig
what are sertoli cells
cells located within seminiferous tubules in testes that provide nourishment + protection to cells produced in spermatogenesis
describe structure of mature sperm cell
acrosome - contains digestive enzymes which break down zona pellucida of egg
flagellum - propulsion
mitochondria - energy
what’s oogenesis
gametogenesis in females that results in production of secondary oocytes
where does oogenesis take place
ovaries
outline stages of oogenesis
primordial germ cell → oogonia → primary oocyte → secondary oocyte + polar body → ootid + polar bodies → ovum
how do primary oocytes form
- primordial germ line cells in ovaries (+ oviduct) divide by mitosis, forming oogonia
- growth period of oogonia w/out further division forms primary oocytes
- meiosis begins but pauses in prophase I until puberty
what happens during first meiotic division of oogenesis
- primary oocytes divide in meiosis I to form secondary oocyte
- polar body buds off + sticks to oocyte
what’s a polar body
haploid cell produced during meiosis in females that doesn’t have ability to be fertilised
when is second meiotic division of oogenesis completed
meiosis II initiated but pauses in metaphase II unless fertilisation takes place
what happens during second meiotic division
secondary oocyte develops into fertilised ovum + second polar body
describe structure of secondary oocyte
corona radiata - outer layer of follicle cells
zona pellucida - coating above cytoplasm that prevents polyspermy + hardens when cortical granules release chemicals
haploid nucleus - fertilisation restores diploid chromosome number
outline stages in development of follicle
primary follicle → secondary follicle → graafian follicle → ovulation → corpus luteum
what’s a primary follicle
immature ovarian follicle surrounded by two layers of follicular cells
what’s a secondary follicle
larger follicle that’s developed from primary follicle
define graafian follicle
mature fluid filled follicle in ovary within which egg cell develops
what’s a corpus luteum
mass of cells that forms from graafian follicle after ovulation
serves as temporary endocrine structure during pregnancy, secreting progesterone
what’s sexual intercourse
entry of male reproductive organ + deposition of sperm into female reproductive tract
explain what happens in fertilisation
- spermatozoa move into fallopian tubes
- acrosome binds to zona pellucida + releases hydrolase enzymes that digest zona pellucida
- membranes of sperm + secondary oocyte fuse, allowing sperm nucleus to enter oocyte
- nuclei fuse, forming diploid zygote
- cortical reaction causes zona pellucida to harden, preventing polyspermy
outline stages of early embryo development
zygote → blastocyst → implantation
how does a blastocyst form
several mitotic division of zygote (cleavage) produce ball of cells, the blastocyst
define implantation
early stage of pregnancy in which blastocyst adheres + sinks into endometrium
what is placenta
temporary organ attached to lining of uterus during pregnancy
name the hormones involved in menstrual cycle
- follicle stimulating hormone (FSH)
- luteinising hormone (LH)
- oestrogen
- progesterone
where is FSH secreted from
anterior pituitary gland
what’s the function of FSH in menstrual cycle
binds to follicle cells, stimulating them to mature + secrete oestrogen
where is LH secreted from
anterior pituitary galnd
what’s the function of LH in menstrual cycle
initiates ovulation + stimulates development of graafian follicle into corpus luteum
what’s the function of oestrogen in menstrual cycle
inhibits production of FSH + causes surge in LH production
what structure secretes progesterone in menstrual cycle
corpus luteum
what’s the function of progesterone in the menstrual cycle
causes development of endometrium + inhibits production of FSH + LH
what happens if implantation doesn’t occur during menstrual cycle
- corpus luteum degenerates due to decreasing FSH + LH levels
- progesterone levels decrease
- endometrium breaks down
what is HCG
- human chorionic gonadotropin
- hormone secreted by developing embryo that maintains corpus luteum during early pregnancy
describe role of placenta in pregnancy
- exchange of gases + nutrients
- barrier between fetal + maternal blood
- secretes progesterone + oestrogen
- protects mothers immune system
- protection from difference between maternal + foetal blood pressure
what’s the role of progesterone during pregnancy
suppresses contractions of uterine wall
what’s the role of oestrogen during pregnancy
stimulates uterine growth + development of mammary glands
how do levels of progesterone + oestrogen change prior to birth
- oestrogen levels increase
- progesterone levels decrease
why do progesterone levels decrease jut before birth
allows uterine wall to contract
where is oxytocin secreted from
posterior pituitary gland
describe the role of oxytocin
triggers contraction of uterus wall
what type of feedback is secretion of oxytocin an example of
positive feedback
what type of feedback is secretion of oxytocin an example of
postive feedback
where is prolactin secreted from
anterior pituitary gland
describe the role of prolactin
stimulates lactation during + after birth
what is amniotic fluid
liquid surrounding embryo in amniotic sac
describe role of amniotic fluid during fetal development
protects foetus + acts as a shock absorber
describe how placenta is adapted for exchange of substances between maternal + fetal blood
- counter current blood flow
- chorionic villi provide large SA for exchange of products
- fetal capillaries lie close to surface, giving short diffusion distance
- abundance of maternal blood vessels
what are intervillous sapces
spaces between chorionic villi that contain maternal blood
describe role of umbilical artery
carries deoxygenated blood from fetus to placeta
describe role of umbilical vein
carries oxygenated blood from placenta to fetus
