Human Sexual Reproduction Flashcards
Open ovulation where does the secondary oocyte move to?
from the ovary to the fallopian tubes (oviducts)
What is the lumen of the fallopian tube lined with?
ciliated epithelium
where does fertilisation take place?
fallopian tubes
What is capacitation?
when the sperm is activated by a change to the membrane surrounding the acrosome
How long do sperm remain viable for?
12-48 hours
What is the secondary oocyte?
name for the egg released at ovulation
suspended in metaphase II
Will complete meiosis II and become an ovum when sperm penetrates it.
When is the acrosome reaction stimulated?
as the head of the sperm binds to the cells of the zona pellucida around the oocyte
what does the acrosome release?
Hydrolytic proteases?
What do the hydrolytic proteases do?
act on the glycoproteins of the zona pellucida to soften them and allow the sperm head to penetrate
What other type of enzymes are also secreted by sperm?
Hyaluronidase enzymes
What does the head of the sperm form to pierce through the softened egg cell?
protein needle-like filament
What happens when the sperm binds to the egg’s membrane?
stimulates a change in the zona pellucida which modifies and thickens to form an impenetrable barrier called the ‘fertilisation membrane’
What is a cortical reaction?
exocytosis (release) of the cortical granules also leads to fertilisation
Where are cortical granules found?
In oocytes
what is formed when the sperm and ovum fuse?
A diploid zygote
What is a blastocyst?
Early stage of the embryo, the zygote undergoes mitosis to form a hollow ball of cells (blastocyst)
When does the blastocyst embed into the endometrium?
after about 3 days
What 2 layers does the trophoblast develop into?
The chorion and the amnion
What is the chorion?
forms finger like projections called chorionic villi which will form the placenta
Secretes human Chorionic Gonadotrophin (HCG)
What do chorionic villi do?
increase surface area for absorption from uterus
What does Human Chorionic gonadotrophin do?
maintains the corpus luteum which secretes progesterone (maintaining pregnancy)
What is the corpus luteum?
the old follicle cells left behind in the ovary after ovulation
What hormone us used to detect pregnancy in pregnancy tests
HCG (Human Chorionic Gonadotrophin)
What are the characteristics of the ovary?
approximately 40mm long
over 200000 specialised cells
only 1% of primary follicles will become secondary oocytes
What is the function of the urethra in males?
carry either semen or urine
what is the function of the urethra in females?
carry urine
What is the bladder?
a muscular membranous sac in the abdomen which receives urine from the kidneys and stores it for excretion
What is the seminal vesicle?
glands along the bladder base that produce fluid that makes up semen
what is the prostate gland?
secretes prostate fluid which is a component of semen
What is the vas deferens?
thick-walled tube in the male reproductive system that transports sperm cells from the epididymis
What is the epipidymis?
a coiled tube in three sections, where the sperm are stored prior to ejaculation
what is the testicle?
either of the two oval organs that produce sperm in men and other male mammals, enclosed in the scrotum behind the penis
What are leydig cells?
found adjacent to the seminiferous tubules in the testicle and produce testosterone in the presence of luteinizing hormone (LH)
What are sertoli cells?
known as nurse or helper cells, as they aid in the progression of spermatogenesis by releasing chemical compounds necessary for sperm production.
What is the seminiferous tubule?
located in the testes, and are the specific location of meiosis, and the subsequent creation of gametes, namely spermatozoa
In spermatogenesis how many cells are made?
4 all with equal distribution of cytoplasm
Are cells of the germinal epithelium haploid or diploid?
diploid
What process do the germinal epithelium cells divide by and form what? (spermatogenesis)
divide by mitosis and form diploid spermatogonia and more germinal epithelium cells
What then happens to these spermatogonia? (spermatogenesis)
they divide by mitosis, making more spermatogonia
some enlarge making diploid primary spermatocytes
What process do these primary spermatocytes then undergo? (spermatogenesis)
meiosis I (1) making secondary spermatocytes, which are haploid
What process do these secondary spermatocytes then undergo? (spermatogenesis)
meiosis II (2) making haploid spermatids
What then happens to spermatids? (spermatogenesis)
They mature into spermatozoa (sperm)
What are the parts of a sperm structure?
The Acrosome (head) contains haploid nucleus
Middle Piece
The Flagellum (tail)
What is the function of the acrosome?
contains enzymes used at fertilisation (gamete fusion, binding to and penetration of the zona pellucida)
What does the middle piece of spermatozoa contain and what is it’s function?
is packed with mitochondria which provide ATP for movement.
What is the function of the flagellum of spermatozoa?
makes lashing movements that move the sperm, although sperm are not motile (capable of motion) until they have been modified in the epididymis
Before birth, in developing foetus, What do the cells of the germinal epithelium in the ovary divide by and to form? (oogenesis)
divide by mitosis
form diploid oogonia and more germinal epithelium cells
what then happens to the oogonia? (oogenesis)
divide many times by mitosis and enlarge, making diploid primary oocytes and oogonia
what then happens to the primary oocytes? (oogenesis)
they begin meiosis I (1) but stops; a girl is born with millions of primary oocytes at prophase 1 (I) in her ovaries
After birth, during early development, what happens to the germinal epithelium cells? (oogenesis)
divide to form diploid follicles, which surround the primary oocytes, making primary follicles
From puberty onwards what happens to the follicles? (oogenesis)
hormones are released and stimulate the primary follicles to develop further
When does a primary oocyte complete meiosis I (1)? (oogenesis)
just before ovulation
What happens when a primary oocyte completes meiosis I (1)? (oogenesis)
makes a haploid secondary oocyte (contains most of the cytoplasm) and a haploid polar body (smaller cell)
What does the primary follicle develop into? (after puberty) (oogenesis)
a secondary follicle which matures into a graafian follicle
What happens to cells in ovulation? (oogenesis)
Each month several primary follicles start to develop, normally only one matures into a fully developed graafian follicle. This then migrates to the surface of the ovary where it bursts and releases a secondary oocyte
What happens to the secondary oocyte after ovulation? (oogenesis)
begins meiosis II (2), but stops at metaphase II (2) unless fertilisation takes place
What happens after fertilisation? (oogenesis)
meiosis Ii (2) is completed, making an ovum containing most of the cytoplasm. and a polar body
What happens to the graafian follicle after ovulation?
it becomes the corpus luteum, if fertilisation occurs it produces hormones, if not it regresses
What surrounds the cell membrane of the secondary oocyte? (oogenesis) (post ovulation)
a glycoprotein layer called the zona pellucida
What stage of meiosis are the chromosomes of the secondary oocyte at? (oogenesis)
metaphase II (2), at the equator, attached to microtubules that make the spindle apparatus
What do cortical granules do?
prevent the entry of more than one sperm
What does the corona radiata do?
surrounds secondary oocyte and provides nutrients
What is capacitation? (fertilisation)
the removal of cholesterol and glycoproteins from the cell membrane over the acrosome in the sperm head
How does the spermatozoa change during capacitation?
the membrane of acrosome becomes more fluid and more permeable to calcium ions,
the tail motion changes to a whipping movement, increasing sperm motility
How long does the sperm take to respond to the oocyte’s chemoattractants?
5 minutes, for sperm to respond and begin to swim through the cervix to the uterus of the oviduct
How long can sperm remain viable for?
2-5 days
When are sperm most fertile?
12-24 hours after ejaculation
How long after ovulation will a secondary oocyte remain viable in the oviduct for?
about 24 hours
How many sperm on average reach the secondary oocyte in the oviduct?
only about 200 of the millions that are deposited
What do the enzymes released by the acrosome do?
digest the cells of the corona radiata, then acrosome reaches zona pellucida
When the acrosome reaches the zona pellucida what happens?
the acrosome membrane ruptures and releases more enzymes (a protease ,acrosin) which hydrolyses the zona pellucida around the secondary oocyte
What happens upon entry of the sperm head?
the cell membranes of the secondary oocyte and sperm fuse and the head of the sperm sinks into the cytoplasm of the secondary oocyte, which is now called an ovum
What is the cortical reaction?
fusion of cortical granule membranes with the oocyte cell membrane, releasing the contents, which convert the zona pellucida into a fertilisation membrane
What does the fertilisation membrane prevent?
polyspermy (entry of additional sperm)
What does entry of the sperm also stimulate the end of?
meiosis II (2) of the ovum nucleus. divides and expels second polar body
What happens within about 24 hours of fertilisation?
the first mitosis combines the genetic material of the parents to make the diploid cells of the embryo. The sperm chromosomes join the ovum chromosomes on the cell’s equator. The cell is now a zygote
How many cells produced in first mitotic division? what is it called?
2 an embryo (until organ development around week 10)
What is the function of the amniotic fluid?
