Module 2: Reproductive Physiology Flashcards
what are primary reproductive organs called
gonads
how is genetic sex determined
by the combo of sex chromosomes at conception
- gametes are produced via meiosis in which diploid parent cells divide to produce haploid gamete cells (sperm and ova). half sperm carry an X, while the other half carry a Y chromosome
- when these 2 haploid cells combine, they create a fertilized ovum w 2 sets of 23 chromosomes (46 total)
- sperm carrying an X chromosome gets fertilized the embryo will b XX, which is female
- XY is male
what is meiosis
specialized germ cells undergo meiosis to produce 4 daughter cells with only a single set of genetic info or 23 unpaired chromosomes. involves meiosis 1 and meiosis 2.
what is meiosis 1
1st division of meiosis, replicated chromosomes containing a identical pair of chromatids, sort themselves into homologous pairs before separating so each daughter cell receives a single set of chromosomes (or one homologue from each pair)
results in 2 daughter cells w a single set of chromosomes, each containing a pair of sister chromatids
what does prophase 1 have
1 diploid cell
what does metaphase 1 have
1 diploid cell
what does anaphase 1 have
1 diploid cell
what does telophase 1 have
2 haploid cells
what is meiosis 2
2nd division, the sister chromatids within the chromosomes of each of the daughter cells separate and are distributed to 2 cells
result is 4 daughter cells each containing a single set of chromosomes containing 1 chromatid each
what does prophase 2 have
2 haploid cells
what does metaphase 2 have
2 haploid cells
what does anaphase 2 have
2 haploid cells
what does telophase 2 have
4 haploid cells
how is the gonadal sex determined
by the presence or absence of a Y chromosome
- 1st 6 weeks of gestation, the reproductive sys of male and female embryos are identical
- around week 7 of preg, the sex-determining region of the Y stim the production of H-Y antigen, which acts on the gonads to differentiate into testes
- absence of H-Y antigen, the gonads differentiate into ovaries
how is the apparent (phenotypic) anatomical sex of an individual decided
dependent on the gonadal sex
- w undifferentiated gonads, embryos of both sexes have the potential to develop either male or female external genitalia and reproductive tracts
- in presence of androgens secreted by the developing testes male-type reproductive sys are developed
- the absence of androgens results in a female-type reproductive system
- external genitalia develop from the same embryonic tissue, the reproductive tracts do not
in the undifferentiated embryo’s what are the 2 primiltive duct systems
the wolffian, and mullerian ducts
what are wolffian ducts and how are they stim
- placenta secretes hCG
- if testes are present, hCG stim them to produce and secrete testosterone
- that testosterone will stim these to develop into the male reproductive sys
- testosterone is converted to dihydrotestosterone, responsible for developing male external genitalia
- testes secrete mullerian-inhibiting factor, causing degradation of the mullerian ducts
what are mullerian ducts, how to they develop
- in absence of testosterone, wolffian ducts degrade and mullerian ducts develop into female reproductive tract + external genitalia
w/o the addition of _______, all fetus’s would be feminized due to high levels of female sex hormones during gestation
testosterone
when do the testes descend
- into the scrotum in the last months of fetal life
- majority of premature male babies, the testes will descent in early childhood
- should they remand undescended into adulthood, this is called cryptorchidism and results in sterility
however in some cases this does not occur
location and function of testes
- primary roles of the testes, spermatogenesis
- temp within the scrotum avgs several degrees celsius less than normal body temp
- descent of testes into this cooler environment is essential bc spermatogenesis is temp sensitive and cannot occur at normal body temperature
what happens when the testes are too cold for spermatogenesis
the scrotal muscles (the cremaster muscle and the dartos muscle) contract to bring the testes closer to the body to gain heat
what happens when testes are too hot for spermatogenesis
the scrotal muscles relax to move the testes away from body
where in the testes is sperm produced
the testes majority consist of coiled seminiferous tubules in which sperm are produced
what secretes testosterone
in connective tissues, between the seminiferous tubules are Leydig cells
- when secreted by this some testosterone enters the bloodstream and circulates to distant target cells
- most testosterone enters the lumen of seminiferous tubules where it supports sperm production
what is testosterone’s effects before birth
causes masculinization of the reproductive tract and external genitalia as well as the descent of testes into the scrotum
testosterone effects on sex-specific tissues after birth
maintains the reproductive tract throughout adulthood, promotes spermatogenesis, and promotes maturation of the reproductive system at puberty
testosterone effects on other reproductive effects
develops sex drive at puberty and controls the secretion of gonadotropin hormone
testosterone effects on secondary sexual characteristics
voice deepens, development of male pattern of body hair, promotion of muscle growth (protein anabolism)
testosterone non-reproductive actions
promotes bone growth at puberty and plays a role in the closing of the epiphyseal plates. may also induce aggressive behaviour.
what are the seminiferous tubules
within testes are highly-coiled seminiferous tubules which are the location of spermatogenesis
majority are composed of: germ cells and Sertoli cells
what is spermatogenesis the process of
process in which diploid (46 chromosomes_ primordial germ cells are converted into motile sperm cells with a haploid (23 chromosomes) set of chromosomes
what are the 3 steps of spermatogenesis
- mitotic proliferation
- meiosis
- packaging
what is mitotic proliferation
- primordial germ cells are called spermatogonia, located on outermost layer of seminiferous tubules
- these cells continuously undergo mitotic division to create a supply of new germs cells
- after each division, 1 daughter cell remains at outer edge while others start to migrate towards lumen of tubule
- sperm-forming daughter cell will undergo mitotic divisions twice more to produce 4 identical primary spermatocytes that enter resting phase in prep for meiosis 1
what is meiosis
- each primary spermatocyte forms 2 secondary spermatocytes (each w 23 double stranded chromosomes)
- in meiosis 2, each secondary spermatocyte results in 2 spermatids, w 23 single stranded chromosomes (after this there are no further divisions)
- for each spermatogonia, 16 spermatids can be produced
what is the packaging phase
- final maturation of spermatids into spermatozoa
- cells are stripped down of all non-essentials such as the cytosol and most organelles
what are the four parts of a mature spermatozoa
(make sure to take a look at the diagram of sec 2 slide 10)
- head (consists of the acrosome and the nucleus)
- midpiece (consists of the mitochondria)
- tail also known as the flagellum (consists of the microtubules
what is the head of the mature spermatozoa
consists of the nucleus
what is the acrosome of a mature spermatozoa
enzyme-packed vesicle at the tip of the head that is needed to penetrate the ovum
what is the midpiece of the mature spermatozoa
packed full of mitochondria to provide energy for locomotion
what is the tail (flagellum) of a mature spermatozoa
movement of this provides propulsion (a process that requires lots of ATP)
- what do sertoli cells make up
- how are they connected, and what happens during the process of spermatogenesis to the developing sperm cells
- what happens to developing sperm cells by the sertoli cells
- a single layer of these cells makes up the walls of the seminiferous tubules
- connected by tight junctions, but during the process of spermatogenesis, developing sperm cells pass between them as they migrate towards the lumen
- developing sperm cells are engulfed in Sertoli cells as they migrate towards the lumen where the sperm head remains embedded until it is mature