IB Biology 11.3 and 11.4

Human Health and Physiology Kidney 11.3 and Reproduction 11.4
Define excretion
Excretion is the removal from the body of the waste products of metabolic activities
Draw and label a diagram of the kidney
Cortex, Renal Pelvis, Medulla, Renal Artery, renal vein, and uretra
Annotate a diagram of a glomerulus and associated nephron to show the function of each part
Afferent arteriole: Brings blood to the nephron to be filtered

Efferent arteriole: Removes blood from nephron (minus filtered components)

Glomerulus: Capillary tuft where filtration occurs

Bowman's Capsule: First part of nephron where filtrate is collected

Proximal Convoluted Tubule: Where selective reabsorption occurs

Loop of Henle: Important for establishing a salt gradient in the medulla

Distal Convoluted Tubule: Final site of selective reabsorption

Collecting Duct: Feeds into ureter and is where osmoregulation occurs

Vasa Recta: Blood network that reabsorbs components from the filtrate
Explain the process of ultrafiltration, including blood pressure, fenestrated blood capillaries and basement membrane
Ultrafiltration occurs when hydrostatic pressure forces blood through a semi-permeable membrane, separating blood cells and large proteins from the remainder of the serum
Ultrafiltration occurs between the glomerulus and the Bowman's capsule and requires two things to form the filtrate:
Hydrostatic Pressure
Basement Membrane
Define osmoregulation
Osmoregulation is the control of the water balance of the blood, tissue or cytoplasm of a living organism
Explain the reabsorption of glucose, water and salts in the proximal convoluted tubule, including the roles of microvilli, osmosis and active transport
The proximal convoluted tubule extends from the Bowman's capsule and is where most selective reabsorption in the nephron occurs
All glucose, amino acids, vitamins and hormones are reabsorbed here, along with most (~80%) of the mineral ions and water
The proximal convoluted tubule has a microvilli cell lining to increase the surface area for the absorption of materials from the filtrate
There are also a large number of mitochondria in these cells, as reabsorption from the filtrate involves active transport
Once materials have been activly reabsorbed into the tubule cells, they can passively diffuse into the bloodstream (along the concentration gradient)
Mineral ions and vitamins are actively transported via protein pumps or carrier proteins
Glucose is actively transported across the membrane in symport with sodium
Water follows the movement of the ions passively (via osmosis)
Explain the roles of the loop of Henle, medulla, collecting duct and ADH (vasopressin) in maintaining the water balance of the blood
Creating a Salt Gradient in the Medulla

The function of the loop of Henle is to create a salt bath concentration in the fluid surrounding the tubule
The descending limb of the loop of Henle is permeable to water, but impermeable to salts
The ascending limb of the loop of Henle is permeable to salts, but impermeable to water
This means that as the loop descends into the medulla, the interstitial fluid becomes more salty (and less salty as it ascends into the cortex)
As the vasa recta blood network that surrounds the loop flows in the opposite direction (counter-current exchange), this further multiplies the effect


As the collecting duct passes through the medulla as it drains into the ureter, the hypertonic solution of the deep medulla will draw water by osmosis
Antidiuretic hormone (ADH or vasopressin) is a hormone released from the posterior pituitary in response to dehydration (detected by hypothalamus)
ADH increases the permeability of the collecting duct to water, allowing more water to be reabsorbed by osmosis (via the production of aquaporins)
This means less water remains in the filtrate and the urine becomes more concentrated
When the individual is suitably rehydrated, ADH levels will decrease and less water will be reabsorbed from the collecting ducts
Explain the difference in the concentration of proteins, glucose and urea between blood plasma, glomerular filtrate and urine

Proteins will be present in blood plasma, but not present in glomerular filtrate or urine
This is because proteins cannot pass across the basement membrane during ultrafiltration and thus cannot form part of the filtrate


Glucose will be present in blood plasma and glomerular filtrate, but not present in urine (normally)
This is because the glucose is selectively reabsorbed in the proximal convoluted tubule
It is reabsorbed from the filtrate into the blood by active transport (symport with Na+ ions)


Urea will be present in blood plasma, glomerular filtrate and urine
Only about 50% of urea is reabsorbed (some urea is reabsorbed to help regulate the medullary osmolarity gradient)
Because water is reabsorbed from the filtrate (by osmosis, due to the hypertonicity of the medulla), urea becomes more concentrated in urine
The concentration of urea in the urine will depend on the amount of water in the urine
Explain the presence of glucose in the urine of untreated diabetic patients
The urine of non-diabetic patients should contain no glucose as it is selectively reabsorbed from the filtrate in the proximal convoluted tubule
Diabetics have higher levels of blood glucose due to either a lack of insulin secretion (type I) or insensitivity to insulin secretions (type II)
Because of this, not all of the glucose in diabetics is reabsorbed into the blood (protein pumps in tubule wall become saturated)
This results in the presence of glucose in the urine of untreated diabetics, which can be detected using test strips
Outline the processes involved in spermatogenesis within the testes, including mitosis, cell growth, the two divisions of meiosis and cell differentiation
Spermatogenesis describes the production of spermatozoa (sperm) in the seminiferous tubules of the testes
The first stage of sperm production requires the division of germline epithelium by mitosis
These cells (spermatogonia) then undergo a period of growth
This is followed by two meiotic divisions that result in four haploid daughter cells
These haploid cells then differentiate to form sperm cells
The developing sperm cells are nourished throughout by the Sertoli cells
State the role of LH, testosterone and FSH in spermatogenesis
LH: Stimulates the interstitial cells (Leydig cells) to produce testosterone

FSH: Stimulates the (first) meiotic division of spermatogonia

Testosterone: Stimulates the (second) meiotic division of spermatogonia and the maturation of spermatozoa through differentiation
Annotate a diagram of the ovary to show the location and function of germline epithelium, primordial follicles, mature follicles and secondary oocyte
Corpus Albicans
Corpus Leteum
Secondary Oocyte
Premordical follicles
Germline Epithelium
Mature follicle

The ovary contains follicles in various stages of development
Egg cells within primordial follicles have been arrested in prophase I and have yet to undergo meiotic division
Egg cells within mature follicles have begun meiotic division and are released from the ovary as secondary oocytes (arrested in prophase II)
The ruptured follicle develops into a corpus luteum that will, in time, degenerate into a corpus albicans
The germline epithelium functions as an epithelial layer separating ovarian tissue from the rest of the body - it is not involved in oocyte development
Outline the processes involved in oogenesis within the ovary, including mitosis, cell growth, the two divisions of meiosis, the unequal division of cytoplasm and the degeneration of polar body
Oogenesis describes the production of female gametes (ova) within the ovary
The process begins during foetal development, when a large number of cells (oogonia) are formed by mitosis before undergoing a period of growth
These cells begin meiosis but are arrested in prophase I until puberty
At puberty, some follicles continue to develop each month is response to FSH secretion
These follicles complete the first meiotic division to form two cells of unequal size
The cell with less cytoplasm is a polar body (which degenerates), while the larger cell forms a secondary oocyte
The secondary oocyte begins the second meiotic division but is arrested in prophase II (until fertilisation)
It is released from the ovary (ruptured follicle develops into corpus luteum) and, if fertilisation occurs, will complete meiosis
The second meiotic division will produce an ovum and a second polar body
Draw and label a diagram of a mature sperm and egg
acrosome, nucleus, centriole, mitochondria, Microtubules , Head, Midpiece, Tail Flagellum

Cortial Granules
Zona Peclluicda (jelly coat)
Plasma membrane
Corona Radiata
Outline the role of the epididymis, seminal vesicle and prostate gland in the production of semen

Testicular fluids are removed, concentrating the sperm
Sperm mature and develop the ability to swim

Seminal Vesicle

Adds nutrients (including fructose) for respiration
Secretes prostaglandins, causing contractions to the female system and helping sperm move towards the egg

Prostate Gland

Secretes alkaline fluid which neutralises vaginal acids (changes pH from 4 to 6 which aids sperm motility)
Compare the processes of spermatogenesis and oogenesis, including the number of gametes and the timing of formation and release of gametes
Both processes result in the formation of haploid gametes
Both processes involve mitosis, growth and meiosis
Describe the process of fertilisation, including the acrosome reaction, penetration of the egg membrane by a sperm and the cortical reaction
When the sperm enters the female reproductive tract, biochemical changes to the sperm occur in the final part of its maturation (capacitation)
The sperm is attracted to the egg due to the release of chemical signals from the secondary oocyte (chemotaxis)
Fertilisation generally occurs in the oviduct (fallopian tube)
To enter the egg membrane, the sperm must penetrate the protective jelly coat (zona pellucida) surrounding the egg via the acrosome reaction
The acrosome vesicle fuses with the jelly coat and releases digestive enzymes which soften the glycoprotein matrix
The membrane of the egg and sperm then fuse and the sperm nucleus (and centriole) enters the egg
To prevent other sperm from penetrating the fertilised egg (polyspermy), the jelly coat undergoes biochemical changes via the cortical reaction
The cortical granules release enzymes that destroy the sperm-binding proteins on the jelly coat
Now fertilised, the nucleus of the secondary oocyte completes meiosis II and then the egg and sperm nuclei fuse to form a diploid zygote
Outline the role of hCG in early pregnanc
The endometrium is a blood-rich environment in which an implanted zygote can grow and it is sustained by the hormone progesterone
If progesterone levels aren't maintained (i.e. the corpus luteum degenerates), then the endometrium will be sloughed away (menstruation)
A fertilised zygote develops into a blastocyst that secretes human chorionic gonadotrophin (hCG)
hCG maintains the corpus luteum post-ovulation so that the blastocyst can remain embedded in the endometrium and continue to develop
Gradually the placenta develops and produces progesterone (at around 8 - 10 weeks), at which point the corpus luteum is no longer needed
Outline early embryo development up to the implantation of the blastocyst
After fertilisation, the zygote undergoes several mitotic divisions to create a solid ball of cells called a morula (at around 4 days)
Unequal divisions beyond this stage cause a fluid-filled cavity to form in the middle - this makes a blastocyst (at around 5 days)
The blastocyst consists of:
An inner mass of cells (this will develop into the embryo)
An outer layer called the trophoblast (this will develop into the placenta)
A fluid filled cavity (called the blastocoele)
These developments all occur as the developing embryo is moving from the oviduct to the uterus
When the blastocyst reaches the uterus, it will embed in the endometrium (implantation)
Explain how the structure and function of the placenta, including its hormonal role in secretion of estrogen and progesterone, maintain pregnancy
Structure and Function

The placenta is a disc-shaped structure that nourishes the developing embryo
It is formed from the development of the trophoblast upon implantation and eventually invades the uterine wall
The umbilical cord connects the fetus to the placenta and maternal blood pools via open ended arterioles into intervillous spaces (lacunae)
Chorionic villi extend into these spaces and facilitate the exchange of materials between the maternal blood and fetal capillaries
Nutrients, oxygen and antibodies will be taken up by the fetus, while carbon dioxide and waste products will be removed
The placenta is expelled from the uterus after childbirth

Hormonal Role

The placenta also takes over the hormonal role of the ovary (at around 12 weeks)
Estrogen stimulates growth of the muscles of the uterus (myometrium) and the development of the mammary glands
Progesterone maintains the endometrium, as well as reduces uterine contractions and maternal immune response (no antibodies against fetus)
Both estrogen and progesterone levels drop near time of birth
Outline the process of birth and its hormonal control, including the changes in progesterone and oxytocin levels and positive feedback
The process of childbirth is called parturition and is controlled by the hormone oxytocin
After nine months, the fetus is fully grown and takes up all available space in the uterus, stretching the walls of the uterus
This causes a signal to be sent to the brain, releasing oxytocin from the posterior pituitary
Oxytocin inhibits progesterone, which was inhibiting uterine contractions
Oxytocin also directly stimulates the smooth muscle of the uterine wall to contract, initiating the birthing process
The contraction of the uterine wall causes further stretching, which triggers more oxytocin to be released (causing even more contraction)
Additionally, the fetus responds to the cramped conditions by releasing prostaglandins which cause further myometrial contractions
As the stimulus causing oxytocin release is increased by the effects of oxytocin, this creates a positive feedback pathway
Contractions will stop when labour is complete and the baby is birthed (no more stretching of the uterine wall)
What is the difference between human sperm and human egg cells?
a.) Sperm have a larger SA:Vol ratio
b.) Sperm have more chromosomes
c.) The division of the cytoplasm in sperm production is uneven
d.) Egg have an acrosome
a.) Sperm have a larger SA:Vol ratio
During the urine production, what happens if water content of the blood is too low?
a.) Membrane channels are produced in the cells of the collecting duct
b.) large volumes of dilute urine is formed
c.) The pituitary gland stopbs secreting ADH
d.) The collecting duct becomes less permeable to water
a.) Membrane channels are produced in the cells of the collecting duct
Which of the following best describes what happens in the glomerulus?
a.) regulation of salt balance leads to the production of urine
b.) Selective reabsorption of water and molecules by active transport
c.) Ultrafiltration introduces water and other molecules into the capillaries
d.) High blood pressure forces water and other molecules into the nephron
d.) High blood pressure forces water and other molecules into the nephron
What is a consequence of insufficient FSH secretion in woman?
a.) menstruation starts before embryo implantation occurs
b.) progesterone secretion is inhibited
c.) embryo implantation fails because uterine lining is too thin
d.) Mature eggs (oocytes) are not produced
d.) Mature eggs (oocytes) are not produced
What is the source of glucose in the fluid in the Bowman's capsule?
a.) blood in the Glomerulus
b.) Filtrate in the distal convoluted tubule
c.) Urine in the Renal pelvis
d.) Interstitial fluid in the medulla
a.) blood in the Glomerulus
What is the processes are required for the reabsorption of glucose in the kidney tubules?
a.) simple and facillitated diffusion
b.) Facilliated diffusion and active transport
c.) Simple diffusion and active transport
d.) Active transport only
b.) Facilliated diffusion and active transport
Which structure is acted upon by ADH (vasopressin)?
a.) PRoximal convoluted tubule
b.) Loop of Henle
c.) Bowman's capsule
d.) Collecting duct
d.) Collecting duct
What is the role of hCG in early pregnancy?
a.) It stimulates teh degeneration of teh corpus leteum
b.) it inhibits the production of estrogen
c.) It initiates the development of uterine lining
d.) It prevents degeneration of the corpus leteum
d.) It prevents degeneration of the corpus leteum
What is the role of testosterone in spermatogenesis?
a.) it inhibits the germinal epithelium
b.) it inhibits the prostate gland
c.) it stimulates interstitial cells
d.) it stimulates Sertoli cells
d.) it stimulates Sertoli cells
Outline the process of in vitro fertilization (IVF). 6 marks
(IVF) is fertilization outside body / "in glass"
(drug) stops normal menstrual cycle
(inject FSH) to stimulate ovaries / stimulate production of eggs
(HCG) matures the follicles
eggs are removed from follicles / ovaries / mother
male provides sperm / sperm donor
washing / capacitation of sperm
eggs are mixed with sperm
2-3 embryos are implanted into uterus
pregnancy test is done to see if implantation / pregnancy has occurred
Production of semen involves a series of processes, which in total take many weeks to carry out. Outline the processes involved in semen production from the start of sperm formation (spermatogenesis) to ejaculation. 8 marks
cell division by mitosis to form more cells / spermatogonia
growth of cells / spermatogonia to form larger calls / primary spermatocytes
cells / primary spermatogonia divide by meiosis
haploid cells / spermatids formed
differentiation of haploid cells / spermatids into sperm
growth of tail / other feature of differentiation
FSH, testosterone and LH all needed for spermatogenesis
sperm stored / maturation in epididymis / gain motility
fluid added to sperm by seminal vesicle (during ejaculation)
fluid from seminal vesicle contains nutrients / mucus
fluid added to sperm by prostate gland (during ejaculation) / fluid from prostate gland contains alkali / minerals
Explain the roles of LH and FSH in the menstrual cycle, including the timing of their secretion during the cycle. 6 marks
FSH is secreted at the start of the cycle / early in the cycle / days 1 to 5 / when progesterone / estrogen is low
FSH stimulates follicle development
FSH stimulates secretion of estrogen (by the follicle / ovary)
LH is secreted in the middle of the cycle / before ovulation / days 10 to 14
LH stimulates ovulation
LH stimulates the development of the corpus luteum
LH stimulates less estrogen
more progesterone secretion / high progesterone / estrogen inhibits FSH and LH release
Explain the processes involved in oogenesis in humans. 9 marks
mitosis used to produce many / 100 000s of cells
so that the ovaries never run out of cells for use in oogenesis
oogonia / cells must grow to a size large enough for meiosis
growth involves accumulation of yolk / food reserves in cytoplasm
replication of DNA is necessary before meiosis
(first division of) meiosis needed to halve the chromosome number
chromosome number must be halved as fertilization will double it
first meiotic division takes place just before ovulation
meiosis gives rise to genetically different cells
variation needed for evolution
second meiotic division occurs after fertilization
division of cytoplasm is unequal
because oocyte / egg needs a large amount of cytoplasm
yolk / food reserves needed by developing zygote / embryo
polar bodies / cells receiving little cytoplasm degenerate
because only small numbers of female gametes are needed
because humans only produce one / few babies at a time
Compare the roles of LH and HCG in female reproduction. 2 marks
both stimulate the development of the corpus luteum
both stimulate the secretion of progesterone
before fertilisation by LH and after by HCG
Compare the process of spermatogenesis and oogenesis. 7 marks
both involve meiosis
both involve cell proliferation / mitosis (before meiosis)
both involve cell growth /enlargement (before meiosis)
LH /FSH involved in both
spermatogenesis starts at puberty versus oogenesis starts in the fetus
spermatogenesis until death versus oogenesis until menopause
millions of sperm versus one egg per month
ejaculation of sperm any time versus ovulation in middle of menstrual cycle
four sperm per meiosis / spermatogenesis versus 2 or 3 polar bodies in oogenesis
spermatogenesis involves equal divisions versus oogenesis involves unequal cell / cytoplasm divisions
no polar bodies in speratogenesis versus 2 or 3 polar bodies in oogenesis
spermatogenesis involves Sertoli / nurse cells versus oogenesis does not
meiosis II completed before fertilization in spermatogenesis versus after in oogenesis
testosterone needed for spermatogenesis versus not needed for oogenesis
Explain oogenesis. 5 marks
mitosis multiplies the germ cells to produce oogonia
cell volume increased / cell grows (after mitosis) (oogonium to primary oocyte)
unequal division of cytoplasm during meiotic divisions
small polar bodies formed and break down (accept three polar bodies formed)
one haploid egg formed per meiosis
oogenesis begins in the fetal ovary of the girl and it is only totally completed at fertilisation
Describe the process of spermatogenesis. 8 marks
in the germ layer / germinal epithelium
spermatogonia produced
mitosis to allow many cells to be produced / continuous cell production
cell growth
enlarged cells are primary spermatocytes
diploid to haploid
two divisions of meiosis
secondary spermatocytes produced by first division / carry out second division
spermatids formed by (second division of) meiosis
differentiation into spermatozoa / mature sperm cells
growth of a tail / acrosome / other feature
ref to role of Sertoli cells
Discuss how, in humans, a larger number of sperms are produced than eggs. 4 marks
more germ cells in testes than ovary / more germinal epithelium
all four products of meiosis become sperm versus one only becoming an egg
continuous sperm production versus monthly egg production
early stages of oogenesis only in the fetus so finite number of cells for oogenesis
reference to progesterone inhibiting FSH secretion and thus egg production
no eggs produced during pregnancy
eggs not produced after menopause
Describe the process of fertilization in humans. 6 marks
acrosome contains enzymes
acrosome releases its contents (by exocytosis)
hyaluronidase / other named enzyme
zona pellucida loosened / broken down
acrosome reaction
many sperm needed to allow one to penetrate
head / sperm nucleus / sperm penetrates the egg membrane
cortical reaction
cortical granules released
zona pellucida hardened
other sperm prevented from entering
reference to fast and slow blacks to polyspermy
Outline the way in which a pregnancy can be detected at a very early stage. 4 marks
test strip dipped into urine
embryo produces HCG
HCG is present in the urine if the woman is pregnant
(monoclonal) antibodies detect / bind to HCG
(monoclonal antibodies have dye attached so) a colour change if the woman is pregnant
Outline the role of human chorionic gonadotropin (HCG) in early pregnancy 2 marks
stimulates / maintains the corpus luteum
stimulates secretion of estrogen / progesterone levels
maintains pregnancy / uterine lining / progesterone levels
State the role of the amniotic sac and the amniotic fluid. 2 marks
support the fetus / weightless / fetus floats in amniotic fluid
protect the fetus / absorb shock / protect against infection
allows the fetus to move