reproductive systems Flashcards
testes
Testes: the male gonad where the male gamete spermatozoa (sperm) is produced.
- there are 2 testes
- held outside of the body for temperature regulation
scrotum
Scrotum: 2 pouches that hold the testes outside the body
- the production and development of sperm require a temperature that is about 2 degrees C lower than normal body temperature- this is why the testes are located outside the body cavity.
- smooth muscle contraction causes scrotum to be closer to body where it is warmer, relaxes and testes move away from body to keep them cooler
seminiferous tubules
Seminiferous tubules: the testes are made up of a series of lobules or compartments filled with fine tubes called the seminiferous tubules
- these tubules are lined with the cells that make sperm
interstitial cells
Interstitial cells: between the seminiferous tubules are clusters of interstitial cells that produce and secrete the male hormone testosterone
epididymis
Epididymis: the seminiferous tubules join into ducts which leave the testis and enter a structure called the epididymis, this is the location where sperm matures
vas deferens
Vas Deferens: the tubule of the epididymis continues to become the vas deferens, the vas deferens carries sperm away from testes
- under the bladder the two vas deferentia, one from each testis join the urethra
urethra
Urethra: the urethra runs from the bladder through the penis to the exterior, it is a duct for transporting both urine and semen
penis
Penis: the external male organ which introduces semen into the female vagina
- contain erectile tissue - a connective tissue with many sponge-like spaces that fill with blood during sexual arousal = erection
semen
Semen: for transfer into a females body, and to reach the egg for fertilisation, the sperm must be in a liquid
- this liquid is called semen and it nourishes and aids the transport of sperm
- it is a mixture of secretions from three glands: the seminal vesicles, the prostate gland, cowper’s gland (the bulbourethral gland)
seminal vesicles
Seminal Vesicles: a pair of pouch like organs located behind the urinary bladder, they secrete a thick fluid that is rich in sugars and makes up about 60% of the volume of semen.
the prostate gland
The Prostate gland: a single gland shaped like a doughnut surrounding the urethra below the bladder, secretes a thin milky alkaline fluid (neutralises acidic conditions of vagina)
cowper’s gland (bulbourethral gland)
two small yellow glands about the size of a pea, located beneath the prostate on either side of the urethra, they secrete a clear mucus which acts a lubricant
pathway of sperm
testes → seminiferous tubules → epididymis → vas deferens → seminal vesicles → prostate gland → urethra → cowper’s gland → penis
- cowper’s gland is after as it’s secretion acts as a lubricant and the other glands (seminal vesicles and prostate gland) nourish the sperm
hormones
hormones are chemical messengers that tell your body what to do and when to do it
Main endocrine glands that affect the reproductive system
- the pituitary gland
- testes
- ovaries
what controls release of hormones from the pituitary gland
the hypothalamus
hormones of males and where they are secreted from
- follicle-stimulating hormone (fsh) - pituitary gland
- luteinising hormone (lh) - pituitary gland
- testosterone - interstitial cells of the cells
FSH
- follicle-stimulating hormone
- secreted by the pituitary gland
- affect the gonads and are thus is called a gonadotrophic hormone
- follicle stimulating hormone: stimulates the seminiferous tubules in the testes to produce sperm
LH
- luteinising hormone
- secreted by the pituitary gland
- affect the gonads and are thus is called a gonadotrophic hormone
luteinising hormone - stimulates interstitial cells in the testes to secrete the hormone testosterone
testosterone
- produced and secreted by the interstitial cells
- testosterone is important for the development of immature sperm cells into mature spermatozoa and regulating sex drive
- other roles: bone mass, fat distribution and muscle mass
- the secretion of testosterone at puberty bring about the development of secondary sexual characteristics in males
male secondary sexual characteristics
- those characteristics associated with a persons sex but not directly involved in sexual reproduction
- voice deepening (increase in larynx size)
- growth of body hair and pubic hair
- increased stature (increase in height)
- increased muscle mass and strength
- increase in penis length
gametogenesis
the process of gamete development through meiosis
types of gametogenesis
- spermatogenesis - formation of spermatozoa (mature sperm) in the testes of males
- oogenesis - formation of ova in the ovary of females
spermatogenesis
- begins at puberty
- occurs inside the seminiferous tubules of each testis
- formatting of haploid spermatids from diploid spermatogonia through meiosis
- these spermatids (immature) then mature to become spermatozoa
order of spermatogenesis
spermatogonia -> primary spermatocytes -> secondary spermatocytes -> spermatids -> spermatozoa
Spermatogonia
- immature sperm mother cells lining the seminiferous tubules of testis
- contains diploid number of chromosomes (46)
- begin dividing by mitosis at puberty
- divide by mitosis to produce primary spermatocytes
- provides continuous source of new cells for production of spermatozoa
primary spermatocytes
- daughter cells from spermatogonia pushed inwards towards the centre of the seminiferous tubule
- here they undergo a period of growth to become enlarged cells
- these diploid cells then undergo the first stage of meiosis to produce secondary spermatocytes
secondary spermatocytes
- haploid after first meiosis division
- undergo second meiotic division to produce spermatids
spermatids
- 2 spermatids from one secondary spermatocyte through meiosis 2
- 4 haploid spermatids are formed from one diploid spermatogonium
spermatids → Spermatozoa
- final stage spermatids mature into spermatozoa (sperm cells)
- as the spermatids matures, much of cytoplasm is lost and a tail containing a contractile material forms
- cytoplasm is removed to get rid of excess baggage, allowing sperm to be more streamline → less weight
- entire process from a spermatogonium to a spermatozoa takes approx 72 days and occurs continuously after puberty
spermatozoa
- 0.06mm long
- head - contain nuclear material and an acrosome
- the acrosome is a fluid filled vesicle, filled with enzymes that assists a sperm to break down the layer of cells surrounding the egg so that fertilisation can occur.
- middle - contain mitochondria where respiration takes place to provide the sperm with energy for movement
- tail - flagellum capable of contractile motions to propel the cell forward
female external structures (the genitalia)
- labia minora and labia majora
- clitoris
female internal structures
- vagina
- cervix
- uterus
- fallopian tubes (uterine tubes or oviducts)
- ovaries
female primary sex organ
two ovaries
ovaries
- they produce female gamete, the ova (egg)
- cells of the ovaries manufacture the female sex hormones - oestrogen and progesterone
Fallopian Tube/Uterine Tube/Oviduct
- when ovulation occurs - the egg from the ovary is expelled into the funnel like opening of the fallopian tube
- transports the egg from the ovary to the uterus
- the opening near the ovary is fringed with finger like projections that guide the egg into the fallopian tube - fimbriae
uterus
- the womb
- the wall of the uterus is made up of smooth muscle with soft mucous membrane lining called the endometrium
- the uterus plays a role in protecting and nourishing the developing foetus during pregnancy
cervix and vagina
- at the lower end of the uterus is the cervix or the neck of the uterus, the cervix separates uterus and vagina
- the vagina is a canal leading to the outside of the body
- muscular structure
- location where sperm is deposited during sexual inter course during sexual intercourse and serves as a birth canal
vulva
- the vagina opens to the exterior region called the vulva
- the vulva is made up of the external genital organs of the female
labia majora
labia majora: 2 fleshy folds of skins containing glands that secrete oils, inner surfaces smooth & moist
labia minora
labia minora: 2 smaller folds between labia majora that surround the openings of the urethra and the vagina
clitoris
equivalent to the penis of the male, contains erectile tissue, blood vessels and nerves
oogenesis
- oogenesis the production of ova within the ovaries
- like spermatogenesis, oogenesis also involves only meiosis and maturation
order of oogenesis
oogonia -> primary oocytes -> primary follicle -> secondary oocyte -> ovum
oogonia
- egg mother cells
- millions develop in the ovaries of a female baby before she is born
- diploid cells that divide via mitosis to make more
- 40-60k egg cells after puberty
primary oocytes
- oogonia which have gone through a growth phase
- by time of birth each ovary contains several hundred thousand primary oocytes
- they begin prophase 1 before birth but then stops at birth, still in prophase 1
primary follicle
- a single layer of cells surround each primary oocyte, forming a primary follicle
- at puberty, process of follicle growth and maturation begins
- primary oocytes contained within the follicle completes first meiotic division producing 2 haploid cells
- secondary oocyte: larger cells which receives half of the chromosomes and nearly all the cytoplasm (more nutrients)
- first polar body: smaller cell receives half of chromosomes but very little cytoplasm (less nutrients, die off later)
secondary oocyte
- the secondary oocyte immediately commences 2nd meiotic division but stops at metaphase 2
- ovulation occurs at metaphase (secondary oocyte is released)
- follicle ruptures expelling secondary oocyte and first polar body from the ovary
- 2nd meiotic division is quickly completed by the secondary oocyte if penetrated by a spermatozoa
- 2nd meiotic division only occurs if secondary oocyte fertilised
- the secondary oocyte produces 2 haploid cells and the larger one develops into the ovum (mature egg) the smaller cell is the second polar body
- the first polar body produces 2 additional polar bodies (if first polar body doesn’t die)
- secondary oocyte only becomes ovum when fertilised (zygote - 46 chromosomes)
ovum
- all polar bodies disintegrate leaving only the mature egg (ovum)
- oogenesis therefore produces a single ovum from each primary oocyte
ovarian cycle
- involves the maturation of an egg and it’s release into the uterine tube (fallopian tubes)
- takes place in the ovaries
- associated with these events are the development of follicles in the ovary and the formation of a structure called the corpus luteum
- the average length of this cycle is 28 days
ovarian cycle phases
- follicular phase: parts of the cycle that occur before ovulation
- ovulatory phase: ovulation
- luteal phase: parts of the cycle that occur after ovulation
what is the follicular phase?
follicular phase: the process of a primary follicle becoming a mature one
- takes 10-14 days
what is a follicle?
fluid filled (follicular fluid) sac surrounded by a single layer of cells that surrounds each immature egg
what happens during the follicular phase?
- cells that form the wall of the primary follicles enlarge and divide
- fluid secreted from these cells creates a fluid filled space that gradually forced the primary oocyte to the edge of the follicle - now called the secondary oocyte
- several primary follicles commence development in each cycle but usually only 1 will complete development (others break down)
- fluid accumulates in follicle and continues to enlarge
- gradually moves towards surface of the ovary, produce a bulge on the surface of the ovary - now referred to as the mature follicle (graafian follicle)
what happens in the ovulatory phase?
- mature follicle bursts expelling the secondary oocyte from the ovaries in a process called ovulation
- a layer of cells called the corona radiata surround the secondary oocyte once it is ovulated
- beating cilia within the fallopian tube create a current which sweep the egg (metaphase II) into the fallopian tube
when does ovulation occur
- ovulation occurs on day 14
- 2 weeks before the end of the ovarian and menstrual cycle
what happens in luteal phase?
- after ovulation the remains of the ruptured follicle form a blood clot in the ovaries - corpus luteum
- hormones that influence the development of the lining of the uterus are secreted by the corpus luteum
- progesterone (a lot) and oestrogen
- if fertilisation of the egg occurs, resulting in pregancy, the corpus luteum continues to develop for a trimester (3 months) and the ovarian cycle ceases
- if fertilisation of egg has not occurred, corpus luteum reaches its maximum development at about 8-10 days after ovulation
- then begins to degenerate into a fibrous mass of scar tissue called the corpus albicans which eventually disappears
- another ovarian cycle then begins
menstrual cycle
- cycle of changes that occur to the lining of the uterus (endometrium)
- preparation of endometrium for the implantation of an embryo, followed by the shedding of the lining if fertilisation does not occur
- Changes align with changes in the ovarian cycle
- Both the ovarian cycle and menstrual cycle occur congruently and coordinated over the 28 day cycle
three phase of the menstrual cycle
- menstrual phase
- proliferation phase
- secretory phase
menstrual phase
- the endometrium breaks down
- about 14 days after ovulation, the blood from broken down capillaries, mucous secretions and cell debris from the endometrium are lost through the vagina (menstruation)
- Corpus luteum degenerates (no fertilisation)→ reduced progesterone causes the break down of the endometrium
- Day 1-5, (Start of menstruation is taken as day 1 of the cycle)
proliferative phase
- The lining of the uterus regenerates and the endometrium thickens
- Occurs under the influence of oestrogen
- Occurs from around days 5-14
- The body begins to prepare for ovulation again
- Follicular phase of the ovarian cycle begins
secretory phase
Day 16 - 20
- The lining of the uterus is maintained under the influence of progesterone ready for implantation of an embryo
- Secretion of glycogen rich mucus secreted by glands in the endometrium, cervix and fallopian tubes
- Mucus provides nutrients for a fertilised ovum for its journey to the endometrium for implantation
- It begins with the formation of the corpus luteum and ends in either pregnancy or the degradation of the corpus luteum to the corpus albicans
correlation between menstrual and ovarian cycles
- Ovarian cycle phases: Follicular phase, ovulation, luteal phase → Follicle grows due to an initially increase in FSH, When the follicle becomes more mature it secretes oestrogen, this rise in oestrogen causes a drop in FSH levels (follicle doesn’t need to be stimulated to grow and mature anymore as the increase in oestrogen signals that the follicle is mature. The rise in oestrogen also influences the endometrium to regenerate and thicken after menses (proliferative phase)
- There is a sudden spike in LH and FSH which triggers ovulation to occur – the follicle is released
- The corpus luteum forms after ovulation as the follicle breaks down, the corpus luteum releases mainly progesterone (hence the rise in progesterone) but also a small amount of oestrogen (small rise in oestrogen). FSH and LH aren’t needed anymore (follicle is matured and ovulation has already occurred, increase in progesterone signals this, so these hormone levels drop). The increased progesterone stimulates the endometrium to prepare for implantation (Secreting glycogen rich mucous)
- If there is no fertilisation the corpus luteum degenerates which reduced the progesterone levels (sudden drop) and oestrogen which will cause menstruation, because progesterone maintains the endometrium
- Low oestrogen levels at the end of menses stimulate FSH to be secreted (Cycle starts again)
female gonadotropic hormones
hormones secreted by the pituitary gland that affect the gonads
- follicle stimulating hormone
- luteinising hormone
other hormones in females
- oestrogen
- progesterone
- human chorionic gonadotropin
- prolactin
follicle stimulating hormone (fsh)
- targets organs - follicles of the ovaries
- effect - stimulates the development and maturation of the ovarian follicle in females
luteinising hormone (lh)
- target organ - cells of ovaries
- stimulates ovulation
- promotes the formation of the corpus luteum
- this in turn stimulates the secretion of oestrogen and progesterone
oestrogen
- secreted by the ovarian follicles and corpus luteum
- target organ - various (e.g. uterus)
- effect - development of female reproductive system and secondary sexual characteristics
- secretion of FSH will reduce as the level of oestrogen increase in the blood
progesterone
- secreted by corpus luteum
- target organ - uterus, placenta and breasts
- effect- maintenance of endometrium, development and maintenance of placenta, development of milk secreting gland
- secretion of LH will reduce as the level of progesterone in the blood increases
human chorionic gonadotropin
- hormone produced by the developing placenta in a pregnant woman
- target organ - corpus luteum
- effect - maintains the corpus luteum during early stages of pregnancy
- the corpus luteum secreted both progesterone and oestrogen, once the placenta itself is able to secrete oestrogen and progesterone, the corpus luteum will degenerate
- all pregnancy tests detect the hormone human chorionic gonadotropin (HCG) which starts to be produced around 6 days after fertilisation
prolactin
- secreted by pituitary gland
- effect: causes contractions of smooth muscle lining the uterus (during labour and menustration
- promotes the contraction of the muscle cells surrounded the breast lobules (promotes movement of milk in the breast)
levels of female hormones
- oestrogen increases slowly from day 7-14, decreases after ovulation
- progesterone low until increase after ovulation, peak at day 21
- LH large increase/peak at ovulation
- FSH low until small increase/peak at ovulation
