NCUK Biology: Fertilization, Implantation, and Placenta

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Questions and Answers

What is the purpose of the enzymes released by the sperm during fertilization?

To strengthen the corona radiata and zona pellucida

To weaken the corona radiata and zona pellucida (correct)

To fertilize the egg

To stimulate ovulation

What is the approximate duration of sperm viability inside the female reproductive tract?

A week or more

A few hours

2 to 4 days (correct)

Only during ovulation

What is the location where fertilization of a human egg usually takes place?

Uterine tube (correct)

Ovary

Uterus

Cervix

What is the purpose of the corona radiata during fertilization?

To block sperm from reaching the egg Signup and view all the answers

What is the approximate number of sperm that reach the uterine tube out of those deposited in the vagina?

1 in 100,000 Signup and view all the answers

What is the result of the union of sperm and egg during fertilization?

A diploid zygote Signup and view all the answers

What is the duration of time during which an unfertilized egg remains viable?

A day or so Signup and view all the answers

What is the percentage of sperm that encounter the egg in the uterine tube?

1 in 20 Signup and view all the answers

What occurs if a person consumes excess water faster than their kidneys can excrete it?

Water in the blood moves by osmosis into the interstitial fluid and then into cells, causing them to swell. Signup and view all the answers

What is the function of the glomerulus?

To filter the blood and collect the resulting filtrate. Signup and view all the answers

What is the result of severe dehydration?

Loss of water in brain cells, leading to coma and death. Signup and view all the answers

How many times does the entire blood volume pass through the kidneys daily?

What is the term for the process of maintaining blood osmolarity within strict limits?

Osmoregulation Signup and view all the answers

What is the function of the renal tubule?

To convert the filtrate into urine. Signup and view all the answers

What is the term for the microscopic urine-forming units in the kidneys?

Nephrons Signup and view all the answers

What occurs if the kidneys cannot conserve enough water?

Dehydration can cause low blood pressure, dizziness, and confusion. Signup and view all the answers

What is the primary function of the antibodies that are selectively transported across the placenta?

To defend the newborn infant against disease Signup and view all the answers

What is the primary mechanism by which the placenta allows exchange of substances between the fetus and mother?

Through the exchange of wastes and nutrients between fetal capillaries and maternal blood pools Signup and view all the answers

What is the main function of the urinary system in most animals?

To excrete cellular wastes and maintain homeostasis Signup and view all the answers

What is the term for the elimination of any form of waste from the body?

Excretion Signup and view all the answers

What are the primary nitrogenous wastes excreted by the urinary system?

Ammonia, urea, and uric acid Signup and view all the answers

What is the composition of urine?

A watery fluid that contains waste products from proteins, ions, and water-soluble nutrients Signup and view all the answers

What is the purpose of the umbilical arteries and veins?

To carry deoxygenated blood from the fetus to the placenta and oxygenated blood back to the fetus Signup and view all the answers

What organs make up the mammalian urinary system?

Kidneys, ureters, bladder, and urethra Signup and view all the answers

What is the primary function of the distal tubule in the nephron?

Fine-tuning of blood composition to maintain homeostasis Signup and view all the answers

Which segment of the nephron is primarily responsible for secretion of substances into the renal tubule?

Proximal tubule Signup and view all the answers

What is the main difference between reabsorption in the proximal tubule and distal tubule?

Reabsorption in the proximal tubule is not under hormonal control, whereas in the distal tubule it is Signup and view all the answers

What is the composition of the filtrate when it enters the distal tubule?

More dilute than the surrounding interstitial fluid Signup and view all the answers

What determines the concentration of urine produced in the distal tubule and collecting duct?

Fluid intake Signup and view all the answers

What is the primary function of the nephron loop?

Reabsorption of water and ions Signup and view all the answers

Which of the following substances is NOT secreted into the renal tubule?

Glucose Signup and view all the answers

What is the main function of hormones in the distal tubule and collecting duct?

Regulation of reabsorption of water and ions to maintain homeostasis Signup and view all the answers

What is the primary function of the glomerular filtration process in the nephron?

To remove small molecules and ions from the blood Signup and view all the answers

What percentage of the blood's fluid is forced out through the glomerular capillary walls during filtration?

20% Signup and view all the answers

What type of substances remain in the blood after glomerular filtration?

Large proteins and blood cells Signup and view all the answers

What is the primary function of the peritubular capillaries in the nephron?

To reabsorb essential nutrients into the bloodstream Signup and view all the answers

What is the role of the bicarbonate ion (HCO3-) in the body?

Maintaining the constant pH required for metabolic reactions Signup and view all the answers

What percentage of the solutes in the glomerular filtrate is made up of urea?

40% Signup and view all the answers

What is the primary function of reabsorption in the nephron?

To return essential nutrients to the bloodstream Signup and view all the answers

What is the function of the glomerular capsule in the nephron?

To collect the glomerular filtrate Signup and view all the answers

Fertilization usually takes place in the uterus.

False Signup and view all the answers

The corona radiata is a barrier that facilitates fertilization.

False Signup and view all the answers

All sperm deposited in the vagina reach the uterine tube.

False Signup and view all the answers

The enzymes released by the sperm strengthen the barriers around the egg.

False Signup and view all the answers

Fertilization results in a haploid zygote.

False Signup and view all the answers

The jelly-like zona pellucida is the outermost layer of the egg.

False Signup and view all the answers

Only one sperm reaches the egg during fertilization.

False Signup and view all the answers

Cell differentiation, gastrulation, and organogenesis occur during the last two months of pregnancy.

False Signup and view all the answers

The zygote undergoes multiple cleavage divisions in the uterus, becoming a morula on its way to the uterine tube.

False Signup and view all the answers

By about the seventh day after fertilization, the zygote has developed into a hollow ball of cells, known as a blastocyst.

False Signup and view all the answers

The inner cell mass of the blastocyst will become the chorion.

False Signup and view all the answers

Gastrulation occurs during the first week of development.

False Signup and view all the answers

The embryonic disk consists of three layers of cells.

False Signup and view all the answers

The slit in the amnion side of the embryonic disk is equivalent to the blastopore in amphibians.

True Signup and view all the answers

The cells exposed to the blastocyst fluid produce the embryo proper.

False Signup and view all the answers

All the cells of the inner cell mass have the potential to develop into only specific types of tissue in the human body.

False Signup and view all the answers

The cells remaining on the surface become endoderm

False Signup and view all the answers

Organogenesis begins during the first two weeks of development

False Signup and view all the answers

The heart starts to beat around the end of the fifth week

False Signup and view all the answers

The umbilical cord forms from the fusion of the yolk stalk and the amnion

False Signup and view all the answers

The chorion grows finger-like villi that extend into the yolk sac

False Signup and view all the answers

The embryo's blood and the mother's blood mix directly in the chorionic villi

False Signup and view all the answers

Oxygen and nutrients diffuse from the embryo to the mother

False Signup and view all the answers

Carbon dioxide and other wastes diffuse from the mother to the embryo

False Signup and view all the answers

The collecting duct carries urine through decreasingly concentrated interstitial fluid within the renal medulla.

False Signup and view all the answers

The interstitial fluid within the renal medulla contains low concentrations of salt and urea.

False Signup and view all the answers

When the collecting duct is impermeable to water, the difference in osmolarity between the urine and the interstitial fluid causes water to leave the urine and enter the interstitial fluid by osmosis.

False Signup and view all the answers

The key to producing concentrated urine lies in the decreased solute concentration of the surrounding fluid.

False Signup and view all the answers

The distal tubule and collecting duct will become less permeable to water in order to conserve water.

False Signup and view all the answers

Returning water to the blood is a minor function of the collecting duct.

False Signup and view all the answers

The concentration of dissolved substances in the filtrate is indicated by the intensity of the red color.

False Signup and view all the answers

The nephron loop is responsible for reabsorption of substances into the renal tubule.

False Signup and view all the answers

If the kidneys cannot conserve enough water, blood osmolarity increases and blood volume decreases.

True Signup and view all the answers

The renal corpuscle is responsible for conducting the filtrate as it is converted to urine.

False Signup and view all the answers

The glomerulus is a knot of impermeable capillaries that allow only small molecules to ooze out.

False Signup and view all the answers

Each kidney contains roughly 2 million microscopic urine-forming units called nephrons.

False Signup and view all the answers

The entire blood volume passes through the kidneys about 30 times daily.

False Signup and view all the answers

The renal tubule is responsible for pressure-filtering the blood and collecting the resulting fluid.

False Signup and view all the answers

Nephrons are packed together in the renal medulla, with a thin extension of each nephron extending into the renal cortex.

False Signup and view all the answers

Swelling in brain cells causes high blood pressure, dizziness, and confusion.

False Signup and view all the answers

What is the primary function of the nephron loop in the renal tubule?

To produce and maintain a high concentration of salt ions (Na+ and Cl-) in the interstitial fluid of the renal medulla Signup and view all the answers

What is the sequence of blood vessels that support the nephron's role in filtering the blood?

Renal artery -> arteriole -> capillaries of the glomerulus -> outgoing arteriole -> peritubular capillaries -> venule -> renal vein Signup and view all the answers

What are the three processes involved in urine formation in the nephrons of the kidneys?

Filtration, Reabsorption, and Secretion Signup and view all the answers

What is the main function of the distal tubule in the nephron?

To convert the filtrate into urine by removing more substances from and secreting into the blood Signup and view all the answers

What is the purpose of the peritubular capillaries surrounding the renal tubule?

To conduct the blood into a venule that joins the renal vein Signup and view all the answers

What is the function of the glomerulus in the nephron?

To filter the blood and produce the glomerular filtrate Signup and view all the answers

What is the term for the microscopic urine-forming units in the kidneys?

Nephrons Signup and view all the answers

What is the primary function of the collecting ducts in the kidney?

To conduct urine from the nephrons into the renal pelvis Signup and view all the answers

What two factors facilitate glomerular filtration in the nephron?

The two factors that facilitate glomerular filtration are the high porosity of the glomerular capillaries and the unusually high pressure within the glomerular capillaries due to the narrow arterioles that collect blood from the capillaries. Signup and view all the answers

What percentage of the blood's fluid is forced out through the glomerular capillary walls during filtration?

About 20% Signup and view all the answers

What is the primary function of reabsorption in the nephron?

To return nearly all the water, ions, and organic nutrients that were previously removed during filtration back to the blood. Signup and view all the answers

What is the role of the bicarbonate ion (HCO3-) in the body?

The bicarbonate ion is crucial for maintaining a constant pH required for metabolic reactions. Signup and view all the answers

What percentage of the solutes in the glomerular filtrate is made up of urea?

About 40% Signup and view all the answers

What is the function of the peritubular capillaries in the nephron?

To return reabsorbed substances to the bloodstream. Signup and view all the answers

What is the function of the glomerular capsule in the nephron?

To collect the filtrate from the glomerular capillaries and direct it into the proximal tubule. Signup and view all the answers

How do substances move from the renal tubules back into the bloodstream during reabsorption?

Through diffusion or active transport through the walls of the renal tubule and into the peritubular capillaries. Signup and view all the answers

What is the primary consequence of excessive water consumption, leading to osmosis into the interstitial fluid and then into cells?

Swelling in brain cells, causing headaches, nausea, vomiting, seizures, coma, and sometimes death. Signup and view all the answers

Describe the structure and function of the glomerulus in the nephron.

The glomerulus is a knot of exceptionally porous capillaries that allow water and small molecules dissolved in the blood plasma to ooze out as blood flows through them, and its function is to pressure-filter the blood. Signup and view all the answers

What is the consequence of severe dehydration, if the kidneys cannot conserve enough water?

Dehydration can cause low blood pressure, dizziness, and confusion, and in extreme cases, loss of water in brain cells can lead to coma and death. Signup and view all the answers

What is the primary function of the renal tubule in the nephron?

The renal tubule conducts the filtrate as it is converted to urine. Signup and view all the answers

What is the significance of the entire blood volume passing through the kidneys about 60 times daily?

This allows the kidneys to fine-tune the blood composition. Signup and view all the answers

Describe the role of the glomerular capsule in the nephron.

The glomerular capsule captures the blood filtrate resulting from the glomerulus's pressure-filtering of the blood. Signup and view all the answers

What is the consequence of the kidneys' inability to conserve enough water in cases of dehydration?

Dehydration can cause low blood pressure, dizziness, and confusion, and in extreme cases, loss of water in brain cells can lead to coma and death. Signup and view all the answers

What is the significance of the renal corpuscle in the nephron?

The renal corpuscle is responsible for pressure-filtering the blood and collecting the resulting fluid, called filtrate. Signup and view all the answers

What is the primary function of the distal tubule in terms of reabsorption?

to fine-tune blood composition by regulating the reabsorption of water and ions to maintain homeostasis Signup and view all the answers

What is the primary function of secretion in the nephron?

to move wastes and excess ions from the blood into the renal tubule for excretion Signup and view all the answers

What determines the concentration of urine produced in the distal tubule and collecting duct?

precise regulation of water reabsorption to maintain the blood's osmolarity within narrow limits Signup and view all the answers

What is the primary function of the nephron loop in terms of reabsorption?

to reabsorb water and ions to maintain homeostasis Signup and view all the answers

What is the primary difference between reabsorption in the proximal tubule and distal tubule?

reabsorption in the proximal tubule is generally not under hormonal control, while in the distal tubule it is under hormonal control to maintain homeostasis Signup and view all the answers

What is the composition of the filtrate when it enters the distal tubule?

about 80% of its water has already been reabsorbed, but it is still dilute compared to the surrounding interstitial fluid Signup and view all the answers

What is the primary function of hormones in the distal tubule and collecting duct?

to regulate reabsorption and secretion to maintain homeostasis Signup and view all the answers

What is the primary function of the renal tubule in terms of secretion?

to move wastes and excess ions from the blood into the renal tubule for excretion Signup and view all the answers

What role do certain types of antibodies play in defending the newborn infant against disease, and how are they transported to the embryo?

These antibodies play an important role in defending the newborn infant against disease, and they are selectively transported across the placenta from mother to embryo, especially late in pregnancy. Signup and view all the answers

What are the two major roles that urinary systems play in most animals, and what substances do they excrete?

The two major roles are to excrete cellular wastes and to help maintain homeostasis. They excrete primarily nitrogenous wastes such as ammonia, urea, and uric acid. Signup and view all the answers

How does the placenta allow for the exchange of substances between the fetus and mother, while keeping their blood supplies separate?

The placenta allows exchange of wastes and nutrients between fetal capillaries and maternal blood pools, while keeping the fetal and maternal blood supplies separate. Signup and view all the answers

What is the term for the process of eliminating any form of waste from the body, and what are the primary nitrogenous wastes excreted by the urinary system?

The term is excretion, and the primary nitrogenous wastes excreted are ammonia, urea, and uric acid. Signup and view all the answers

What are the components of the mammalian urinary system, and what is the function of the urinary system in most animals?

The components are the paired kidneys and ureters, as well as a single bladder and urethra. The function is to excrete cellular wastes and help maintain homeostasis. Signup and view all the answers

What is the composition of urine, and what is its role in the body?

Urine is a watery fluid that contains a variety of substances that have been removed from the blood, including waste products, ions, and excess nutrients. Signup and view all the answers

What are the umbilical arteries and veins responsible for, and how do they contribute to the development of the fetus?

The umbilical arteries carry deoxygenated blood from the fetus to the placenta, and the umbilical vein carries oxygenated blood back to the fetus. Signup and view all the answers

Why is the placenta not a complete barrier to the transfer of substances between the mother and fetus, and what are the implications of this?

The placenta is not a complete barrier because some disease-causing organisms and harmful chemicals can pass through it. Signup and view all the answers

Fertilization, the union of sperm and egg, produces a ______ zygote.

diploid Signup and view all the answers

Men produce sperm more or less ______, and women ovulate about once a month.

continuously Signup and view all the answers

Sperm, under ideal conditions, may live for 2 to (rarely) ______ days inside the female reproductive tract.

4 Signup and view all the answers

The egg is surrounded by ______ follicle cells when it leaves the ovary.

accessory Signup and view all the answers

The ______ pellucida lies between the corona radiata and the egg.

jelly-like zona Signup and view all the answers

Perhaps 1 in ______ of the sperm deposited in the vagina reaches the uterine tube.

100,000 Signup and view all the answers

Cell differentiation, gastrulation, and organogenesis occur during the first two ______.

months Signup and view all the answers

Fertilization of a human egg usually takes place in the ______ tube.

uterine Signup and view all the answers

The outermost layer of each kidney is the ______ cortex.

renal Signup and view all the answers

The ______ medulla surrounds a branched, funnel-like chamber called the renal pelvis.

renal Signup and view all the answers

The average adult ______ can hold about a pint (500 milliliters) of urine.

bladder Signup and view all the answers

Urine is retained in the bladder by two circular ______ muscles.

sphincter Signup and view all the answers

An important function of the kidney is ______ regulation.

osmoregulation Signup and view all the answers

The ureter is a narrow, muscular tube that contracts rhythmically to propel the urine from the kidney to the ______.

bladder Signup and view all the answers

Urine exits the body through the ______, a single narrow tube.

urethra Signup and view all the answers

Water balance is essential for ______.

homeostasis Signup and view all the answers

The renal tubule consists of three parts: The first portion is the _______________ tubule.

proximal Signup and view all the answers

The filtrate then enters the second portion of the tubule, the nephron loop (also called the _______________ of Henle).

loop Signup and view all the answers

The main function of the nephron loop is to produce and maintain a high concentration of _______________ ions (Na+ and Cl-) in the interstitial fluid of the renal medulla.

salt Signup and view all the answers

The filtrate is finally converted into _______________ in the distal tubule.

urine Signup and view all the answers

Urine is produced in the nephrons of the kidneys by three processes: _______________, Reabsorption, and Secretion.

Filtration Signup and view all the answers

Blood is carried to the kidney by the _______________ artery.

renal Signup and view all the answers

Collecting ducts conduct urine from the renal cortex, through the renal medulla, and into the _______________ pelvis.

renal Signup and view all the answers

The peritubular capillaries conduct the blood into a _______________ that joins the renal vein.

venule Signup and view all the answers

When the collecting duct is ______ permeable, water will leave the urine and enter the interstitial fluid by osmosis.

water Signup and view all the answers

The ______ fluid within the renal medulla contains high concentrations of salt and urea.

interstitial Signup and view all the answers

Returning water to the blood to avoid ______ is a major function of the collecting duct.

dehydration Signup and view all the answers

The key to producing concentrated urine lies in the elevated ______ concentration of the surrounding fluid.

solute Signup and view all the answers

The distal tubule and collecting duct will become more ______ to water, which will leave the urine by osmosis.

permeable Signup and view all the answers

The collecting duct carries urine through increasingly concentrated ______ fluid within the renal medulla.

interstitial Signup and view all the answers

Salt enters the ______ fluid from the nephron loop.

interstitial Signup and view all the answers

The concentration of dissolved substances in the filtrate is indicated by the intensity of ______ color.

yellow Signup and view all the answers

Most reabsorption takes place in the ______ tubule.

proximal Signup and view all the answers

In the ______ tubule, reabsorption is generally under hormonal control.

distal Signup and view all the answers

The ______ tubule fine-tunes blood composition by regulating the reabsorption of water and ions.

distal Signup and view all the answers

The fluid that has travelled through the nephron becomes ______ as it leaves the distal tubule.

urine Signup and view all the answers

Secretion occurs primarily in the ______ tubule, but some also occurs in the distal tubule.

proximal Signup and view all the answers

When the filtrate enters the ______ tubule, about 80% of its water has already been reabsorbed.

distal Signup and view all the answers

Concentration of urine occurs in the ______ tubule and collecting duct.

distal Signup and view all the answers

If fluid intake has been low, ______ urine will be produced.

concentrated Signup and view all the answers

What is the primary function of the antibodies that are selectively transported across the placenta?

To defend the newborn infant against disease Signup and view all the answers

The placenta provides complete protection against disease-causing organisms and harmful chemicals.

False Signup and view all the answers

What is the primary role of the urinary system in most animals?

To excrete cellular wastes and help maintain homeostasis Signup and view all the answers

The urinary system excretes cellular wastes, primarily the nitrogenous wastes _______________, urea, and uric acid.

ammonia Signup and view all the answers

Match the following components of the mammalian urinary system with their descriptions:

Kidneys = Produce and eliminate urine Ureters = Transport urine from the kidneys to the bladder Bladder = Stores urine Urethra = Transports urine out of the body Signup and view all the answers

The umbilical arteries carry oxygenated blood from the placenta to the fetus.

False Signup and view all the answers

What is the term for the elimination of any form of waste from the body?

Excretion Signup and view all the answers

The placenta allows exchange of _______________ and nutrients between fetal capillaries and maternal blood pools.

wastes Signup and view all the answers

What happens if a person consumes excess water faster than their kidneys can excrete it?

Surplus water in the blood will move into the interstitial fluid and then into cells, causing them to swell Signup and view all the answers

The kidneys can filter blood without any problems even if a person is severely dehydrated.

False Signup and view all the answers

What is the function of the renal corpuscle?

To pressure-filter the blood and collect the resulting fluid, called filtrate Signup and view all the answers

The entire blood volume passes through the kidneys approximately _______________ times daily.

60 Signup and view all the answers

Match the following parts of the nephron with their functions:

Glomerulus = Pressure-filter the blood Renal tubule = Convert filtrate to urine Glomerular capsule = Collect the resulting fluid Nephron = Filter blood and produce urine Signup and view all the answers

The kidneys can only filter blood, but not produce urine.

False Signup and view all the answers

What is the result of severe dehydration on brain cells?

Loss of water in brain cells, leading to coma and death in extreme cases Signup and view all the answers

What is the term for the process of maintaining blood osmolarity within strict limits?

Osmoregulation Signup and view all the answers

What is the primary function of the glomerular filtration process in the nephron?

Removal of small molecules and ions from the blood Signup and view all the answers

Blood cells and plasma proteins can pass through the glomerular capillary walls during filtration.

False Signup and view all the answers

What percentage of the blood's fluid is forced out through the glomerular capillary walls during filtration?

20% Signup and view all the answers

The bicarbonate ion (HCO3-) is crucial for maintaining a constant ______________________ required for metabolic reactions.

pH Signup and view all the answers

Match the following substances with their functions in the body:

Na+ = Critical for nerve and muscle function Cl- = Critical for nerve and muscle function K+ = Critical for nerve and muscle function Ca2+ = Critical for nerve and muscle function HCO3- = Crucial for maintaining a constant pH Signup and view all the answers

What is the primary function of reabsorption in the nephron?

Returning important substances to the blood Signup and view all the answers

Urea makes up about 60% of the solutes in the glomerular filtrate.

False Signup and view all the answers

What is the primary function of the peritubular capillaries in the nephron?

Return reabsorbed substances to the bloodstream Signup and view all the answers

What is the primary function of the nephron loop?

To produce and maintain a high concentration of salt ions in the interstitial fluid of the renal medulla Signup and view all the answers

The distal tubule is the first part of the renal tubule.

False Signup and view all the answers

What is the main function of the renal tubule?

To convert filtrate into urine Signup and view all the answers

The collecting ducts conduct urine from the renal cortex, through the renal medulla, and into the ______________.

renal pelvis Signup and view all the answers

What is the term for the process of producing urine in the nephrons?

Urine formation Signup and view all the answers

Match the following parts of the renal tubule with their functions:

Proximal tubule = Return water and essential molecules and ions to the blood Nephron loop = Produce and maintain a high concentration of salt ions in the interstitial fluid of the renal medulla Distal tubule = Convert filtrate into urine Signup and view all the answers

The renal artery supplies blood to the entire kidney.

True Signup and view all the answers

What is the function of the peritubular capillaries in the nephron?

To conduct blood into a venule that joins the renal vein Signup and view all the answers

What is the main function of the collecting duct in the nephron?

To return water to the blood to avoid dehydration Signup and view all the answers

The interstitial fluid within the renal medulla has low concentrations of salt and urea.

False Signup and view all the answers

What is the result of the difference in osmolarity between the urine and the interstitial fluid in the collecting duct?

Water leaves the urine and enters the interstitial fluid by osmosis. Signup and view all the answers

The key to producing concentrated urine lies in the elevated solute concentration of the surrounding ________________.

fluid Signup and view all the answers

What is the primary function of the nephron loop?

To regulate water reabsorption and urine concentration Signup and view all the answers

Match the following structures with their functions:

Distal tubule = Regulates water reabsorption and urine concentration Collecting duct = Carries urine through increasingly concentrated interstitial fluid Nephron loop = Reabsorbs solutes from the filtrate Glomerulus = Filters the blood Signup and view all the answers

The proximal tubule is primarily responsible for secretion of substances into the renal tubule.

False Signup and view all the answers

What is the result of the collecting duct being water permeable?

Water leaves the urine and enters the interstitial fluid by osmosis. Signup and view all the answers

Study Notes

Fertilization, Implantation, and Role of Placenta

Fertilization: union of sperm and egg, produces a diploid zygote
Sperm and egg nuclei unite during fertilization
Process of fertilization:
- Sperm released into vagina during intercourse
- Sperm move through cervix, into uterus, and enter uterine tubes
- Sperm may live for 2-4 days inside female reproductive tract, egg remains viable for a day or so
- Copulation within a day or two of ovulation allows sperm to meet egg in uterine tube
Barriers to fertilization:
- Corona radiata (accessory follicle cells) surrounds egg
- Zona pellucida (jelly-like) lies between corona radiata and egg
Fertilization process:
- Hundreds of sperm surround corona radiata, release enzymes to weaken barriers
- Sperm wriggle through to egg, only a few hundred join in attacking barriers
Importance of fertilization:
- Fertilization usually takes place in uterine tube
- Certain antibodies are selectively transported across placenta from mother to embryo, defending newborn against disease

Role of Placenta

Placenta:
- Isolates fetus from many assaults, but does not provide complete protection
- Allows exchange of wastes and nutrients between fetal capillaries and maternal blood pools, keeping fetal and maternal blood supplies separate
- Umbilical arteries carry deoxygenated blood from fetus to placenta, umbilical vein carries oxygenated blood back to fetus

Human Excretory System

Urinary System

Urinary systems: produce and eliminate urine
Urine composition:
- Waste products from proteins, ions, and excess water-soluble nutrients
- Contains cellular wastes, primarily nitrogenous wastes (ammonia, urea, uric acid)
Urinary systems' roles:
- Excrete cellular wastes
- Help maintain homeostasis

Mammalian Urinary System

Consists of paired kidneys, ureters, bladder, and urethra
Osmoregulation: maintaining blood osmolarity within strict limits

Nephron and its Blood Supply

Nephrons in kidneys: filter blood, produce urine
Nephron structure:
- Renal corpuscle and renal tubule
- Renal corpuscle: glomerulus and glomerular capsule
Nephron function:
- Filtration: removes small molecules and ions from blood
- Reabsorption: returns important substances to blood
- Secretion: actively transports substances into renal tubule for excretion
- Concentration of urine: occurs in distal tubule and collecting duct

Filtration

Filtration: first step in urine formation, removes small molecules and ions from blood
Factors facilitating glomerular filtration:
- Porous glomerular capillaries
- High pressure within glomerular capillaries due to narrow arterioles
Filtration process:
- Fluid forced out of glomerular capillaries into surrounding glomerular capsule
- Blood cells and plasma proteins too large to penetrate capillary walls, remain in blood

Reabsorption

Reabsorption: returns important substances to blood
Substances reabsorbed:
- Water, ions (Na+, Cl-, K+, Ca2+, HCO3-), and organic nutrients (vitamins, glucose, amino acids)
Reabsorption process:
- Molecules move by diffusion or active transport through renal tubule walls into peritubular capillaries
- Most reabsorption occurs in proximal tubule, but also occurs in nephron loop and distal tubule

Secretion

Secretion: actively transports substances into renal tubule for excretion
Substances secreted:
- Excess K+, H+, small quantities of ammonia, medicinal and recreational drugs or breakdown products, food additives, and pesticides
Secretion process:
- Occurs primarily in proximal tubule, but also in distal tubule
- Regulated by circulating hormones to maintain homeostasis

Concentration of Urine

Concentration of urine: occurs in distal tubule and collecting duct
Process:
- Filtrate enters distal tubule, about 80% of water has been reabsorbed in proximal tubule and nephron loop
- Additional reabsorption of water precisely regulated to maintain blood osmolarity within narrow limits
- Fluid intake affects concentration of urine produced

Fertilization

Fertilization is the union of sperm and egg, producing a diploid zygote.
Sperm and egg nuclei unite during fertilization, with the sperm releasing enzymes to weaken the corona radiata and zona pellucida, allowing the sperm to reach the egg.
Only a few hundred sperm out of the millions deposited in the vagina reach the uterine tube, and only one sperm fertilizes the egg.

Implantation

Fertilization usually takes place in the uterine tube, and the resulting zygote undergoes cleavage divisions, becoming a morula on its way to the uterus.
By around the fifth day after fertilization, the zygote develops into a hollow ball of cells called a blastocyst.
The outer cell layer of the blastocyst attaches to and then burrows into the lining of the uterus, a process called implantation, forming the placenta.

Cell Differentiation, Gastrulation, and Organogenesis

During the first two months, cell differentiation, gastrulation, and organogenesis occur.
Gastrulation begins near the end of the second week, with cells migrating in through a slit in the embryonic disk to form mesoderm, endoderm, and ectoderm.
Organogenesis begins during weeks three to eight, with the formation of the spinal cord, brain, and heart.

Role of Placenta

The placenta exchanges materials between the mother and embryo, with the chorion forming finger-like chorionic villi that extend into the endometrium.
The embryo's blood and the mother's blood remain separated, but oxygen and nutrients diffuse from the mother to the embryo, and carbon dioxide and wastes diffuse from the embryo to the mother.

Excretory System

Osmoregulation

Osmoregulation is the process of maintaining blood osmolarity within strict limits to prevent dehydration or overhydration.
Dehydration can cause low blood pressure, dizziness, and confusion, while excess water can cause headaches, nausea, and vomiting.

Nephrons

The kidneys filter blood and produce urine through nephrons, which are packed together in the renal cortex and medulla.
Each nephron has two major parts: the renal corpuscle and the renal tubule.
The renal corpuscle pressure-filters the blood and collects the resulting fluid, called filtrate.
The renal tubule conducts the filtrate as it is converted to urine, with the distal tubule and collecting duct regulating water reabsorption to prevent dehydration.

Urine Formation

The key to producing concentrated urine lies in the elevated solute concentration of the surrounding fluid in the renal medulla.
The collecting duct carries urine through increasingly concentrated interstitial fluid, causing water to leave the urine and enter the interstitial fluid by osmosis, resulting in concentrated urine.

The Placenta and Antibodies

The placenta selectively transports certain antibodies from mother to embryo, especially late in pregnancy, to defend the newborn against disease.
The placenta isolates the fetus from many assaults, but does not provide complete protection; some disease-causing organisms and harmful chemicals can pass through.
The placenta allows exchange of wastes and nutrients between fetal capillaries and maternal blood pools, while keeping the fetal and maternal blood supplies separate.
The umbilical arteries carry deoxygenated blood from the fetus to the placenta, and the umbilical vein carries oxygenated blood back to the fetus.

The Human Urinary System

Urinary systems produce and eliminate urine, a watery fluid containing waste products from proteins, ions, and other water-soluble nutrients, and certain foreign substances.
Urinary systems play two major roles in most animals: excreting cellular wastes and maintaining homeostasis.

Urinary Systems Excrete Cellular Wastes

Excretion is a general term that encompasses the elimination of any form of waste from the body.
Urinary systems excrete cellular wastes, primarily nitrogenous wastes (ammonia, urea, and uric acid).

The Mammalian Urinary System

The mammalian urinary system consists of the paired kidneys and ureters, as well as a single bladder and urethra.
Osmoregulation is the process of maintaining blood osmolarity (the concentration of ions and other solutes in the blood plasma) within strict limits.
If a person consumes excess water or becomes dehydrated, it can lead to serious health issues (headaches, nausea, seizures, coma, and death).

An Individual Nephron and Its Blood Supply

Nephrons in the kidneys filter blood and produce urine.
The entire blood volume passes through the kidneys about 60 times daily, allowing them to fine-tune its composition.
Each kidney contains roughly 1 million microscopic urine-forming units called nephrons.
Nephrons have two major parts: the renal corpuscle and the renal tubule.

The Renal Corpuscle and Renal Tubule

The renal corpuscle is responsible for pressure-filtering the blood and collecting the resulting fluid, called filtrate.
The renal corpuscle consists of two parts: the glomerulus and the glomerular capsule.
The glomerulus is a knot of exceptionally porous capillaries that allow water and small molecules dissolved in the blood plasma to ooze out as blood flows through them.
The glomerular capsule captures the filtrate.
The filtrate then enters the renal tubule, which conducts the filtrate as it is converted to urine.
The renal tubule consists of three parts: the proximal tubule, the nephron loop, and the distal tubule.

Blood Vessels Support the Nephron's Role in Filtering the Blood

Blood is carried to the kidney by the renal artery, which gives rise to thousands of microscopically narrow arterioles.
Each arteriole supplies blood to a nephron.
The arteriole branches to form the capillaries of the glomerulus, which empty into an outgoing arteriole.
The outgoing arteriole gives rise to peritubular capillaries, which form a network surrounding the renal tubule.
The peritubular capillaries conduct the blood into a venule that joins the renal vein.

How Is Urine Formed?

Urine is produced in the nephrons of the kidneys by three processes: filtration, reabsorption, and secretion.
As urine is formed, dissolved substances move between the parts of the nephron and the interstitial fluid that surrounds these structures.

Filtration Removes Small Molecules and Ions from the Blood

Filtration, the first step in urine formation, occurs when fluid is forced by blood pressure through the walls of the nephron's glomerular capillaries.
Two factors facilitate glomerular filtration: the glomerular capillaries are far more porous than most other capillaries, and the arterioles that collect blood from the capillaries are narrower than the arterioles that supply them, creating an unusually high pressure within the glomerular capillaries.
As a result, about 20% of the blood's fluid, along with its small dissolved molecules, is forced out through the glomerular capillary walls.
Blood cells and plasma proteins, which are too large to penetrate the capillary walls, remain in the blood.

Reabsorption Returns Important Substances to the Blood

Reabsorption returns to the blood nearly all the water, ions (Na+, Cl-, K+, Ca2+, HCO3-), and organic nutrients such as vitamins, glucose, and amino acids that were previously removed during filtration.
The reabsorbed molecules move by diffusion or active transport through the walls of the renal tubule and into the peritubular capillaries, which return them to the bloodstream.

Secretion Actively Transports Substances into the Renal Tubule for Excretion

Secretion, which occurs mainly through active transport, moves wastes and excess ions from the blood into the renal tubule.
Secreted substances include excess K+ and H+, small quantities of ammonia, some medicinal and recreational drugs or their breakdown products, as well as certain food additives and pesticides.

Concentration of Urine Occurs in the Distal Tubule and Collecting Duct

When the filtrate enters the distal tubule, about 80% of its water has already been reabsorbed in the proximal tubule and nephron loop, but the filtrate is still considerably more dilute than the surrounding interstitial fluid in the renal cortex.
From this point on, additional reabsorption of water is precisely regulated to maintain the blood's osmolarity within narrow limits.
If fluid intake has been high, more water will be left behind in the filtrate, and watery urine will be produced until the normal blood volume is restored.
If fluid intake has been low, concentrated urine will be produced.

Fertilization

Fertilization produces a diploid zygote through the union of sperm and egg.
Men produce sperm continuously, while women ovulate about once a month.
During fertilization, sperm move through the cervix, uterus, and uterine tubes, where they can live for 2-4 days.
The egg is surrounded by accessory follicle cells (corona radiata) and a jelly-like zona pellucida, which act as barriers to sperm.
Sperm release enzymes to weaken these barriers, allowing a single sperm to fertilize the egg.
Only a few hundred sperm out of the millions deposited in the vagina reach the uterine tube, and only one fertilizes the egg.

Cell Differentiation, Gastrulation, and Organogenesis

These processes occur during the first two months of development.
Fertilization typically takes place in the uterine tube.

Structure and Blood Supply of the Human Kidney

The human kidney is a fist-sized organ located at waist level on either side of the spinal column.
The outermost layer is the renal cortex, beneath which lies the renal medulla (kidney marrow).
The renal medulla surrounds the renal pelvis (kidney bucket), which collects and conducts urine into the ureter.
The ureter is a muscular tube that propels urine into the bladder.
The bladder is a hollow, muscular chamber that stores and collects urine.

Urine Formation and Excretion

Urine is produced in the nephrons of the kidneys through three processes: filtration, reabsorption, and secretion.
Filtration occurs in the renal corpuscle, where the arteriole branches into capillaries.
Reabsorption occurs mainly in the proximal tubule, where water and essential molecules are returned to the blood.
Secretion occurs mainly in the proximal tubule, where wastes and excess ions are actively transported into the renal tubule.
The distal tubule fine-tunes blood composition by regulating reabsorption and secretion to maintain homeostasis.
Concentrated urine is produced in the distal tubule and collecting duct through precise regulation of water reabsorption.

Osmoregulation and Urine Concentration

The kidney regulates water balance by producing concentrated urine to conserve water.
The nephron loop produces a high concentration of salt ions (Na+ and Cl-) in the interstitial fluid, which helps the kidney produce concentrated urine.
The collecting duct becomes more permeable to water when fluid intake is low, allowing water to leave the urine by osmosis and return to the blood.
The elevated solute concentration of the surrounding fluid in the renal medulla enables the production of concentrated urine.

Placenta and Fetus

The placenta allows exchange of wastes and nutrients between fetal capillaries and maternal blood pools, while keeping the fetal and maternal blood supplies separate.
The umbilical arteries carry deoxygenated blood from the fetus to the placenta, and the umbilical vein carries oxygenated blood back to the fetus.
Certain antibodies are selectively transported across the placenta from mother to embryo, especially late in pregnancy, and play an important role in defending the newborn infant against disease.
The placenta does not provide complete protection: some disease-causing organisms and many harmful chemicals can pass through the placenta.

Human Urinary System

Urinary systems are organ systems that produce and eliminate urine, which contains waste products from proteins, ions, and other water-soluble nutrients in excess of the body's needs, and certain foreign substances.
Urinary systems play two major roles in most animals: they excrete cellular wastes and help maintain homeostasis.
The mammalian urinary system consists of the paired kidneys and ureters, as well as a single bladder and urethra.

Osmoregulation

Osmoregulation is the process of maintaining blood osmolarity (the concentration of ions and other solutes in the blood plasma) within very strict limits.
If a person consumes excess water, the surplus water in the blood will move by osmosis into the interstitial fluid and then into cells, causing them to swell.
If a person becomes dehydrated, blood osmolarity increases and blood volume decreases, leading to low blood pressure, dizziness, and confusion.

Nephron and Blood Supply

Each kidney contains roughly 1 million microscopic urine-forming units called nephrons.
Nephrons are packed together in the renal cortex, with a thin extension of each nephron extending into the renal medulla.
Each nephron has two major parts: the renal corpuscle and the renal tubule.
The renal corpuscle is responsible for pressure-filtering the blood and collecting the resulting fluid, called filtrate.
The renal tubule consists of three parts: the proximal tubule, the nephron loop (also called the loop of Henle), and the distal tubule.

Urine Formation

Urine is produced in the nephrons of the kidneys by three processes: filtration, reabsorption, and secretion.
Filtration removes small molecules and ions from the blood, including about 20% of the blood's fluid and small dissolved molecules.
Reabsorption returns to the blood nearly all the water, ions, and organic nutrients that were previously removed during filtration.
The collecting duct carries urine through increasingly concentrated interstitial fluid within the renal medulla, allowing water to leave the urine and enter the interstitial fluid by osmosis, producing concentrated urine.

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Description

A biology quiz covering the process of fertilization, implantation, and the role of the placenta in reproduction. Topics include sperm and egg nuclei union and human reproductive cycles.