Reproductive physiology Flashcards
what are the different types of reproduction
1) sexual reproduction = production of haploid gametes which form a diploid zygote
2) Asexual reproduction
- corals = budding & fragmentation
- daphnia = parthenogenesis (reproduction from ovum without fertilization)
3) hermaphrodites
what are the different reproductive strategies
1) oviparous =
producing by eggs which are hatched after laying, nourishment within egg
2)ovoviparous=
producing young by means of eggs which are hatched within the body of the parent, nutrition from eggs
3) viviparous =
bringing forth live young which have developed inside the body of the parent, nourishment from mother till birth
what is the difference between r and k selective reproduction
r = produce lots of eggs and offspring at once such as in frogs with little parental investment
k = produce few or a singular offspring with high parental investment
what are the different mechanisms for sex determination
1) genetic sex determination
= presence of sex chromosomes such as XX (female) and XY (males)
= Y chromosome contains SRY hormone for development of male characteristics
= birds are different females ZW, males ZZ, females lack gene which occurs on Z as W is shorter so don’t develop as male
2) environmental sex determination e.g. temperature influences in turtles, warmer = females, stress and glucocortisol also influence sex of some species
how does gene expression control sexual differentiation
SRY gene in males codes for testis determining factor (TDF) which causes gonads to differentiate into testis
WNT = testosterone suppression in females
gonad-genesis (generation of gonads) and steroid-genesis work together for sex steroids development (oestrogen and testosterone) and the development of gonads which when mature allow gametogenesis
= not always fixed some species are hermaphrodites reproducing with clonal forms and sex plasticity of females transitioning to male and back again
what features do all reproductive systems have
1) neuroendocrine glands
= hormonal control for sex differentiation, gonad/steroid/gametogenesis
2) gonads
= testis and ovaries producing sex steroids and gametes
3) reproductive tract
4) accessory organs
= both develop and receive gametes and facilitate development of offspring
outline an invertebrate example of a female reproductive system
more variable endocrine control
- neuroendocrine glands = interplay between the brain and corpora allata producing juvinile hormones
brain = OEH, facilitates ovary development and egg production and vitogellin
vitogellin = egg yolk protein which provide nutrition to embryo produced from juvenile hormones
outline an invertebrate example of a female reproductive system
HPG axis = interplay between hypothalamus and anterior pituitary gland and gonads
- the hypothalamus receives signals internally and externally releasing gonadotrophic releasing hormone
- this acts on the AP which releases gonadotropins (LH and FSH) which act on the gonads
- gonads then produce sex hormones
outline the structure and function of the testis
Function = production of sperm cells after the process of spermatogenesis as well as the production of sex steroids
structure = internalised pair of testis with various tubes and ducts
1) seminiferous tubules = site of mitosis ad meiosis for spermatid production
2) epididymis = site of sperm maturation
what are the two cells found in testis and what are their functions
Hypothalamus –> gonadatropin releasing hormone –> LH and FSH –> acts on two cell types within testis
1) steroli cells = aka nurse cells which support the development of sperm in the seminiferous tubules by providing androgen binding proteins (responsive to testosterone), production of nutrients and protection by phagocytosis
2) Leydig cells = outside of the semiferous tubules within interstitial tissues which secrete testosterone which act on steroli cells and developing cells, responsive to LH
outline the process of spermatogenesis within the testis
1) spermatogonia (2n) ells undergo mitosis producing one dasughter cell which remains and spermatogonia and the other becomes a primary spermatocyte
2) P.S (2n) undergoes first meiotic division forming 2 (n) secondary spermatocytes
3) second meitoic divison forming 4 (n) spermatids
4) each spermatid undergoes morphological and structural changes to form mature spermatozoa e.g. acrosome and tail formation, loss of non-vital organelles
what are the two types of spermatogenesis
1) cystic = allows high concentration of sperm to be released at one time as spermatogonia enclosed in individual steroli cells. Sertoli cells nourish different stages of germ cells simultaneously in distinct regions of their surfaces before being released
= seen in mostly aquatic animals
2) non-cystic = sperm production occurs in the middle of seminiferous tubules with spermatogonia on the outside and move inwards as they mature before being released into the lumen, steroli cells are dotted between sperm cells
how does ovary structure differ in fish
fish = external fertilisation with pairs of ovaries which extend the entire length of their body
outline the two main cycles seen in the female reproductive cycle
1) Ovarian cycle = made up of the follicular phase and luteal phase
the development and release of an egg controlled by FSH and LH
2) Uterine cycle = preparation of the uterus to receive a fertilised egg divided into the menstrual phase (shedding of endometrium) , proliferative phase (regeneration and multiplication of endometrial cells) and secretory phase (following ovulation ruptured follicle transform into the corpus luteum
outline the process of oogenesis
Before birth
1) oogonia (2n) undergo mitosis increasing numbers
2) oogonia differenciate into primary oocytes
3) oocytes arrest in prophase I of meiosis and remain in this state till puberty
4) at puberty they are activated and one primary oocytes become surrounded by granulosa cells forming primordial follicle
5) undergoes further development and maturation producing a Graafian follicle
6)completes meisosi I forming secondary oocyte and a polar body
7) secondary oocyte is arrested in metaphase II of meiosis which is completed after fertilization producing an ovum and another polar body
