Human Reproduction Flashcards
Can you label and recognise structures in the male reproductive system?
https://www.healthdirect.gov.au/male-reproductive-system
Give 10 labels of the male reproductive system
Testes
Scrotum
Penis
Seminiferous tubules
Epididymus
Vas deferans
Seminal vesical
Prostate gland
Urethra
Ureter
Describe the function of the testes
These are a pair of organs that contain the seminiferous tubules and epididymus which are crucial for sperm production
Describe the function of the scrotum
This is an external sac that protects the testes and maintains them at a temperature lower than the body’s core temperature (37 °C)
Describe the function of the penis
This intromittent organ is responsible for delivering sperm into the female reproductive system
Describe the function of the seminiferous tubules
These structures within the testes are where spermatozoa are produced and also contains cells that produce testosterone
Describe the function of the epididymus
This is where spermatozoa mature and are stored until ejaculation
Describe the function of the vas deferans
Spermatozoa travel along this tube from the epididymus to the urethra during ejaculation
Describe the function of the seminal vesical
These glands produce a mucus secretion that enhances sperm motility
Describe the function of the prostate gland
This gland produces an alkaline fluid that neutralises urine and supports sperm motility
It can also undergo enlargement and put pressure on the urethra
Describe the function of the urethra
This tube carries urine from the bladder to the outside of the body and is longer than the female urethra
Describe the function of the ureter
These tubes connect the kidneys to the bladder
Can you label and recognise the female reproductive system
https://maygrant.com/reproductive-development/diagram-of-reproductive-organs/
Give the 6 labels of the female reproductive system
Ovaries
Oviducts
Uterus
Endometrium
Cervix
Vagina
Describe the function of the ovaries
These are a pair of organs where both mitosis and meiosis occur to produce primary and secondary oocytes. The hormones FSH and LH regulate the development and release of secondary oocytes
Ovaries aren’t connected to oviducts and the ovum that is released is attracted to the oviduct but may not make it there
Describe the function of the oviducts
Also known as fallopian tubes, these are the pathways through which ova travel to reach the uterus. They are lined with ciliated epithelial cells and are the site of fertilisation
Describe the function of the uterus
Commonly referred to as the womb, this organ has muscular walls called the myometrium and is lined with the endometrium. During childbirth, oxytocin induces contractions through a positive feedback mechanism
Describe the function of the endometrium
This is the mucus membrane lining of the uterus, with a rich supply of blood. The embryo implants here during pregnancy or is shed during menstruation. Its maintenance is regulated by the hormones progesterone and oestrogen
Describe the function of the cervix
This is the (strong) ring of muscle and connective tissue at the entrance to the uterus
Describe the function of the vagina
This canal provides a passageway for menstrual blood and mucosal tissue from the uterus. It also receives the penis during sexual inter course and serves as the birth canal during childbirth
It also shrinks a bit near the cervix to reduce the baby’s journey from the womb to the outside world
what is gametogenesis?
this is the process of producing gametes, which occurs in specialised paired glands called gonads
define spermatogenesis
the formation of sperm in the testes
define oogenesis
the formation of ova in the ovaries
what do the germinal epithelium cells in the gonads undergo and produce?
undergo both mitosis and meiosis
to produce genetically different haploid gametes
why is it important that the gametes are haploid?
so when fertilisation occurs, the diploid number is restored and the zygote has a full set of homologous chromosomes
what leads to the genetic variation in the gametes?
crossing over during Prophase I and independent assortment during Metaphase I
where is spermatozoa produced?
within the seminiferous tubules of the testes
how many on average of spermatozoa is produced daily?
germinal epithelial cells in these tubules give ruse to approximately 120 million viable spermatozoa daily
what hormones are required to develop spermatozoa?
FSH
Testosterone
draw a diagram of spermatogenesis and indicate next to each cell whether it is diploid or haploid (2n or n)
page 5 in booklet
what is a sertoli cell?
a type of somatic cell around which spermatids develops
they are located in the seminiferous tubules
describe the role of sertoli cells
to secrete a fluid which nourishes the spermatids and protects them from the immune system of the male
to provide oxygen and remove waste products
what are interstitial cells? (cells of Leydig)
a type of somatic cell that is stimulated by the hormone LH
they are located outside the seminiferous tubules
what is the role of interstitial cells?
to secrete testosterone
what does testosterone do?
stimulates spermatogenesis and causes male secondary sexual characteristics to develop
summarise spermatogenesis
spermatozoa are produced in the seminiferous tubules of the testes by a process called spermatogenesis
spermatogonia divide many times to produce primary spermatocytes
these undergo meiosis and the products of the first meiotic division are haploid secondary spermatocytes
these undergo the second half of the meiotic division producing spermatids which differentiate and mature into spermatozoa
the spermatozoa are protected (from the immune system) and nourished by the sertoli cells
can you recognise and label a spermatozoon?
page 7 in booklet
give the labels of the spermatozoon
cell membrane
acrosome
haploid nucleus
centriole
mitochondrion
axial filament
describe the contents and the function of the head in the spermatozoon
contains a haploid nucleus and is covered at the end by a structure called the acrosome, a large lysosome which contains enzymes used in fertilisation
describe the contents and the function of the mid piece in the spermatozoon
packed with mitochondria which provide ATP for movement
describe the contents and the function of the tail in the spermatozoon
also known as the flagellum, this structure makes lashing movements that propel the sperm, enabling its motility
why is both meiosis and mitosis important in spermatozoon production?
meiosis produces haploid spermatozoa and leads to genetic variation
mitosis produces large numbers of primary spermatocytes
this leads to large numbers of spermatocytes, which increases the chances of fertilisation
describe the process of oogenesis
the germinal epithelium cells also divide to form follicle cells, which surround the primary oocytes to form primary follicles
at puberty, hormones stimulate these follicles to develop further
each month, one or more follicles will mature into a graafian follicle containing a secondary oocyte
the mature graafian follicle migrates to the surface of the ovary where it bursts to release the secondary oocyte - this is ovulation
after ovulation, the graafian follicle becomes the corpus luteum which - if fertilisation occurs - secretes hormones for pregnancy
if fertilisation does not occur, the corpus luteum degenerates into the corpus albicans
can you recognise oogenesis in the ovary with the use of diagrams?
page 9-10 and 12 in booklet
describe the structure of the secondary oocyte after ovulation
a clear glycoprotein layer called the zona pellucida surrounds the cell membrane of the secondary oocyte
the chromosomes of the secondary oocyte are a t metaphase II
corona radiata cells surround the secondary oocyte and provide nutrients
give the labels of the graafian follicle in the ovary
germinal epithelium
theca
antrum
zona pellucida
secondary oocyte
cells of corona radiata
stroma of ovary
what happens at the before birth stage in a woman’s life?
germinal epithelium cells (2n) divide by mitosis to form oogonia (2n)
oogonia undergo mitosis to form primary oocytes (2n)
these commence meiosis I but stop at prophase I
this primary oocyte is contained within a primary follicle
what happens at the after puberty, each month stage in a woman’s life?
the primary oocyte completes meiosis I to form a secondary oocyte (n)
this commences meiosis II but stops at metaphase II
the primary follicle develops into a graafian follicle containing the secondary oocyte
what happens at the fertilisation stage in a woman’s life?
the secondary oocyte completes meiosis II to form an ovum
during cytokinesis, how does the splitting of the cytoplasm differ in oogenesis and spermatogenesis?
cytoplasm split unequally in oogenesis
cytoplasm split equally in spermatogenesis
what happens when an embryo is not implanted?
the endometrium is shed through menstruation
describe briefly about menstruation
this occurs monthly from the start of puberty (menarche) to the menopause
the menstrual cycle is a system of positive and negative feedback , operating between events involving the brain, the ovaries and the uterus
what happens at the start of the menstrual cycle (day 0)?
the anterior pituitary gland secretes follicle-stimulating hormone (FSH)
what does FSH trigger and stimulate in the menstrual cycle?
triggers the development of a follicle in the ovary which will mature into a graafian follicle
also stimulates the production of oestrogen
following menstruation, the level of oestrogen secreted by the developing follicle increases in the blood. this results in….
inhibition of further production of FSH by negative feedback so no new follicles develop
stimulation of the anterior pituitary gland to secrete luteinising hormone (LH) by positive feedback
growth and repair of the endometrium
what does a high level of LH cause in the menstrual cycle?
initiates ovulation
also causes the graafian follicle to develop into the corpus luteum
what does the corpus luteum secrete during progesterone and what does progesterone do?
CL secretes progesterone which causes further development of the endometrium
progesterone also inhibits further production and release of LH and increases the level of mucus in the cervix to block the entry of sperm
if implantation does not occur during the menstrual cycle….
falling FSH and LH levels cause the corpus luteum to degenerate
progesterone levels fall
the endometrium breaks down and is lost during menstruation
FSH is no longer inhibited, and another menstrual cycle is initiated
summarise the menstrual cycle
FSH secreted by the anterior pituitary gland, stimulates the maturation of a follicle, stimulating the production of oestrogen
as a result, oestrogen secreted by the developing follicle increases in the blood which triggers the repair of the endometrium and inhibits FSH production and stimulates LH production
a high level of LH secreted by the anterior pituitary, initiates ovulation and causes the graafian follicle to develop into a corpus luteum
progesterone secreted by the corpus luteum causes further development of the endometrium prior to menstruation
if implantation does not occur, falling FSH and LH levels cause the corpus luteum to degenerate, progesterone levels fall, the endometrium breaks down and is lost during menstruation
explain how oestrogen can be used as a contraceptive pill?
oestrogen inhibits production of FSH
without FSH the follicles do not develop
without a mature/graafian follicle, ovulation and subsequent fertilisation cannot take place
explain how progesterone can be used as a contraceptive pill?
progesterone inhibits LH secretion and so no ovulation
progesterone increases levels of mucus in the cervix so blocks the entry of sperm
no ovulation or no sperm means no fertilisation can take place
IVF involves the maturation of a large number of follicles which can then be retrieved from the ovary, suggest the hormone that would be provided to patients and explain your answer
FSH
responsible for primary follicles developing into graafian follicles/follicle development
describe the process of copulation (sexual intercourse)
arterioles entering the penis dilate while the venules leaving the penis constrict
this leads to a build up of blood in spaces in the penis, causing it to become erect
the penis is then inserted into the vagina and movements result in the ejaculation of semen
the force of ejaculation is sufficient to propel some sperm through the cervix into the uterus, with the remainder being deposited at the top of the vagina
briefly describe what the sperm do after entering the uterus
the sperm respond to chemoattractants released by the secondary oocyte and swim to the oviduct
the sperm remain viable for 2-5 days but are most fertile 12-24 hours after ejaculation
if ovulation has recently occurred, a secondary oocyte will be present in the oviduct, although it will only remain viable for 24 hours unless fertilised
what are the names of the three stages of fertilisation?
capacitation
acrosome reaction
cortical reaction
describe capacitation
spermatozoa can only fertilise a secondary oocyte after undergoing a process called capacitation, which takes several hours
capacitation involves changes to the cell membrane covering the acrosome, removing cholesterol and glycoproteins
this increases the permeability of the acrosome membrane to calcium ions and enhances the spermatozoon’s motility
plasma membrane is reorganised and destabilised, K+ channels open allowing influx of calcium, uterine chemicals cause membrane proteins to leak out
describe acrosome reaction
the spermatozoa push their way through the cells of the corona radiata
on contact with the zona pellucida, the acrosome membrane ruptures, releasing hydrolase enzymes which digest a path through the zona pellucida
the membranes of the spermatozoon and secondary oocyte then fuse, allowing the genetic material of the spermatozoon (haploid nucleus) to enter the secondary oocyte
describe cortical reaction
once a spermatozoon has successfully penetrated the secondary oocyte, the oocyte’s smooth endoplasmic reticulum releases calcium ions into the cytoplasm
these calcium ions cause cortical granules to fuse with the cell membrane and release their contents, modifying the zona pellucida
the zona pellucida hardens to form the fertilisation membrane which prevents other sperm from penetrating the egg (polyspermy)
why is it important that the zona pellucida hardens?
the oocyte could receive too many chromosomes resulting in an inviable zygote
what else happens in the process of fertilisation after the three stages are done?
the entry of the spermatozoon’s genetic material also triggers the continuation of meiosis II, forming the ovum and a polar body
the nuclei of the spermatozoon and ovum fuse to form a zygotic nucleus
the fertilised ovum, now called a zygote, is diploid (2n)
summarise fertilisation
spermatozoa are attracted to the oocyte by chemoattractants
sperm enter the oviduct and swim towards the secondary oocyte
on contact with the zona pellucida, the spermatozoon’s acrosome ruptures, releasing hydrolase enzymes
these enzymes digest a pathway through the zona pellucida
the membranes of the secondary oocyte and sperm fuse, allowing the haploid nucleus of the sperm to enter the secondary oocyte
the nucleus of the secondary oocyte completes meiosis II
the cortical reaction occurs, releasing cortical granules
the zona pellucida hardens, forming a fertilisation membrane to prevent polyspermy
the haploid nuclei of the sperm and secondary oocyte fuse to form a diploid zygote
describe the process of implantation
the zygote undergoes repeated mitotic division, forming a ball of cells. this process is known as cleavage
by day seven, cleavage has resulted in the production of a hollow ball of cells called a blastocyst
the blastocyst moves into the uterus where it attaches and embeds into the endometrium, a process known as implantation
give some labels involved with implantation
endometrium
trophoblast
inner cell mass - embryoblast (forms the embryo)
blastocyst cavity
how long does the period of pregnancy last?
period from the first day of the last menstrual cycle until birth - lasts approx. 39 weeks in humans
what is the amniotic fluid?
the embryo, which later becomes the foetus, develops and grows in the uterus, enclosed by the amnion, a membrane derived from the blastocyst
what is the role of amniotic fluid?
maintains the foetal temperature
acts as a shock absorber, protecting the foetus from injury from outside the uterus
prenatal diagnosis can take place to identify foetal chromosomal abnormalities. suggest three concerns that some people may have about the ethics of prenatal diagnosis
it could increase the rate of abortion, which conflicts with the perceived moral status of the foetus (when do we attain the right to life)
it could cause unintended harm to the foetus
it could provide false positive or false negative results
describe the placenta
the placenta forms between the maternal and foetal tissues and is connected to the foetus by the umbilical cord
the cord contains two blood vessels; an umbilical artery and an umbilical vein
describe the umbilical artery and umbilical vein
the umbilical artery carries deoxygenated blood and waste products, such as carbon dioxide, away from the foetus
the umbilical vein carries oxygenated blood and nutrients, like glucose, to the foetus
where are foetal capillaries located?
in the chorionic villi, which form the boundary between maternal and foetal blood
how does the exchange of materials occur between the mother and foetus?
food from the maternal arteries empties into an intervillous space
there absence of maternal capillaries between the maternal arteriole and maternal venule reduces the number of cell layers to be crossed, providing a shorter diffusion pathway for materials
foetal capillaries are immersed in this intervillous space, allowing the exchange of materials to occur
blood containing waste materials then returns to maternal venules from the intervillous space
maternal and foetal blood flow in opposite direction to maintain a concentration gradient across the whole placenta and is also known as counter-current flow
what are the roles of the placenta?
1 - facilitates the exchange of materials across a thin barrier which separates maternal and foetal blood: into foetal blood is glucose, oxygen, amino acids and salts
and out of foetal blood is carbon dioxide and nitrogenous waste
2 - provides protection from the immune system of the mother
3 - protects the foetus from the differences in maternal and foetal blood pressures (the mother’s blood pressure is much higher than that of the foetus, and could cause damage)
4 - allows the passage of maternal antibodies into the foetus to provide short term immunity - known as passive immunity
describe and explain the position of the foetal oxygen dissociated curve and how this benefits the foetus (also bonus if you remember the shape of the curves (foetal and adult) on the graph)
foetal haemoglobin has a higher affinity for oxygen than the mothers haemoglobin
the dissociation curve shifts to the left
therefore foetal haemoglobin can load oxygen from the mother’s blood at all partial pressures of oxygen
foetal haemoglobin becomes highly saturated with oxygen
what hormone is secreted just before and after implantation?
the developing embryo secrets hCG which maintains the corpus luteum for the first 26 weeks of pregnancy
what hormones does the placenta secrete?
progesterone and oestrogen which rise to high levels in the blood plasma
these hormones suppress the secretion of FSH and LH
why are FSH and LH suppressed during pregnancy?
FSH - so no more follicles mature
LH - so ovulation isn’t possible
what does progesterone and oestrogen do during pregnancy?
progesterone suppresses the uterine wall’s ability to contract and maintains the endometrium
oestrogen stimulates the growth of the uterus to accommodate the growing foetus and stimulates the growth and development of the mammary glands
what happens just before birth?
oestrogen levels increase and progesterone levels decrease meaning the uterine walls can now contract
what are two other hormones released before birth?
oxytocin and prolactin
describe the role of the hormone oxytocin
it is secreted by the posterior pituitary gland
it stimulates the contraction of the myometrium (muscle layer in the wall of the uterus)
these contractions stimulate the secretion of more oxytocin, which is an eg of positive feedback
as the oxytocin levels increase, the contractions become stronger and more frequent
5 steps of oxytocin release:
head of foetus pushes against cervix
nerve impulses from the cervix transmitted to brain
brain stimulates pituitary gland to secrete oxytocin
oxytocin carried in bloodstream to uterus
oxytocin stimulates uterine contractions and pushes foetus toward cervix
(repeat)
describe the role of the hormone prolactin
released from the anterior lobe of the pituitary gland during and after birth to stimulate the production of milk by mammary glands
what does oxytocin do after birth?
releases milk for the current feed and helps the baby to get the milk easily
(positive feedback involved)
(prolactin PRODUCES milk and oxytocin RELEASES it)
