1.1 Development of the reproductive system Flashcards
How do new individuals arise?
from fusion of 2 haploid gametes
what does fusion of 2 haploid gametes form?
diploid conceptus (embryo)
where do gametes (sex cells: sperm / ova) originate from?
diploid germ cells (diploid sex cells)
undergo meiosis –> haploid gametes
what are diploid germ cells?
embryonic cells that have the potential to develop into spermatozoa / ovum (gametes)
what are gametes?
spermatozoa or ovum
(sex cells - haploid)
from diploid germ cells
where do diploid germ cells separate from?
separated from somatic cells early in embryonic life
what is the male and female gamete?
female gamete = ovum
male gamete = sperm
what is the male gametes production rate? why?
7000 sperm / second
have to exploit (make use of) the intermittent female activity
what is the production of female gametes like?
limited by the number that can be supported by gestation
about 400 in total fertile lifespan (40 years), 12-14 per year (between conception to birth)
where are gametes produced?
in the gonads
what are the male and female gonads?
males = testis female = ovary
aside from gonads, what is the remainder of the reproductive system divided into?
internal and external genitalia
what are the female internal genitalia?
Ovaries Duct system: vagina cervix uterus fallopian tube
what are the female external genitalia?
vestibule
labia minora & majora
clitoris
perineum
what are the male internal genitalia?
testis Duct system: epididymus, vas deferens, (urethra) seminal vesicles prostate bulbo-urethral gland
what are the male external genitalia?
penis
scrotum
when do secondary (sexual) characteristics arise?
at puberty when gametes begin to be produced
what does secondary characteristics aid?
facilitate sexual interaction
what are the secondary characteristics in females?
decrease in body size (relative to male) subcutaneous fat distribution hair & skin changes breast development smell & touch become more acute CNS effects
what are the secondary characteristics in male?
increase in body size (relative to female) change in body composition hair & skin changes pain experienced more acutely CNS effects
what are the secondary characteristic changes coordinated by?
hormones e.g. those by pituitary gland (FSH & LH) or from gonads (testosterone, oestrogen & progesterone)
what do the hormones in repro coordinate?
production of gametes
mechanisms of gestation
parturition (birth)
where are the repro hormones produced from?
hypothalamus
anterior & posterior pituitary gland
gonads
placenta
what are the hormones produced in the hypothalamus?
peptides releasing factors:
GnRH (gonadotrophin releasing hormone)
FSH (follicle stimulating hormone)
LH (leutinising hormone)
which hormone is produced in the posterior pituitary gland?
oxytocin
hypothalamus neural control
what are the hormones produced in the anterior pituitary gland?
gonadotrophins:
FSH (follicle stimulating)
LH (leutinising)
which hormones are produced by the gonads? (ovaries & testis)
gonadal steroids:
male = testosterone
females = oestrogens (oestradiol, oestrone, oestriol) & progesterone
inhibin
what are the hormones produced by the placenta?
human chorionic gonadotrophin (hCG)
human placental lactogen (hPL)
Oestrogen (oestradiol, oestrone, oestriol)
Progesterone
when do germ cells arise?
3 weeks after conception
what is the genetic sex of an individual determined by?
the chromosome (XX or XY) of the germ cells which arise 3 weeks post conception
what is the developed gonad made up of?
somatic cells from original primordium (early structure) and germ cells
what does primordial gonad consist of?
cortex and a medulla
what can the primordial gonad form?
ovary or testis - depending on genetic sex
how do male germ cells develop from the primordial gonad?
colonise in the medullary region, cortex region will atrophy
M = Medullary, Male
thick tunica albuginea (enclose gonads tightly)
what do the germ cells within males allow for?
rapid growth of the definitive sex cords
where does structural development occur?
in utero
when does functional development and maturation occur?
continues after birth
what is the indifferent stage of development of reproductive tracts?
gonad and duct systems
what is the developmental ‘cross-roads’ stage of reproductive tracts regulated by?
genetic sex: XX or XY
what is the urogenital ridge?
region of intermediate mesoderm giving rise to both embryonic kidney and gonad
what is indifferent gonad derived from?
intermediate mesoderm + primordial germ cells (extragonadal)
Where do primordial germ cells arise from? where do they migrate to? what do they form?
arise in yolk sac, migrate into retroperitoneum, along dorsal mesentery into UG ridge
forming primordial gonads, mesonephric origin
what determines the genetic male?
male gamete (sperm) carrying Y chromosome
primordial germ cells carry Y chromosome (meiosis to form haploid gamete)
so XY male conceptus (embryo)
what physical characteristics (organs) determine male?
gonad (testis) internal genitalia (duct system) external genitalia
what drives the development of MALE?
expression of SRY genes
what determines genetic female?
male gamete carrying X chromosome (XX female conceptus)
primordial germ cells do NOT carry Y chromosome
what leads to development of female?
absence of Y chromosome
what is the female gonad?
ovary
how do female germ cells develop from the primordial gonads?
colonise the cortex of primordial gonad (containing primordial of follicles)
medullary cords regress
no tunica albuginea
what is the (indifferent stage) duct systems that develop? where do they end?
mesonephric (embryonic kidney ducts) and paramesonephric ducts developes in both male & female embryos
both end in cloaca
what is the mesonephric system?
mesonephric tubules which perform primitive renal function (filter blood - nephrons)
what makes up the embryonic kidneys?
mesonephric tubules + mesonephric duct
what is mesonephric duct also know as? what is it’s direction of travel? what does it make contact with?
Wolffian duct
runs caudally
make contact with cloaca
