Urinary System

Question 1

What are the organs and structures of the urinary system?

Answer 1

The kidneys, the ureters, the urethra and the bladder

Question 2

What are functions of the kidneys?

Answer 2

Fluid homeostasis, filtration of wastes and homeostasis of blood volume and chemical makeup

Question 3

Which glands sit atop the kidneys?

Answer 3

The adrenal glands

Question 4

Describe kidney anatomy…..

Answer 4

the kidneys are bean shaped, about the size of a can of of soup and weigh approx 5 ounces … They are located in the lumbar region between the T12 and L-3 vertebra. The renal hilus is a cleft on the medial concave (curves inward) that leads to a space called the renal sinus. Ureters, blood vessels and nerves are located in the sinus and entering the kidney at the hilus.

Question 5

What are the three layers of specialized tissue protecting the kidney surface ?

Answer 5

The outer renal fascia - dense fibrous connective tissue that keeps the kidney in place inside the abdominal cavity The adipose capsule- fatty layer that protects the kidney from trauma The renal capsule - tough fibrous outer skin of the kidney which protects it from injury and infection

Question 6

What are the three regions of the kidney?

Answer 6

The cortex, the medulla and the pelvis

Question 7

What does the renal cortex consist of ?

Answer 7

This is the outer region that is just inside the renal capsule. It has a number of projections called cortical columns that extend down between the renal medulla pyramids. Located within the renal cortex are the glomerular capsule and the distal and convoluted tubule sections of the nephrons along with associated blood vessels.

Question 8

What does the renal medulla consists of ?

Answer 8

This is a region below to the renal cortex- it is divided into sections called pyramids that point toward the center of the kidney. Located within the medulla are the Loop of Henle and the collecting duct sections of the nephrons.

Question 9

What does the renal pelvis consist of ?

Answer 9

The renal pelvis is the centermost section of the kidney near the renal hilus. It is a funnel shaped tube that connects to the ureter as it leaves the hilus. This is done through extensions of the renal pelvis called calyces- these collect urine which drains continuously into the renal pelvis and then into the ureter, which transports it to the bladder for storage.

Question 10

How many ml of blood are delivered to the kidney per minute?

Answer 10

The renal arteries deliver about 1200 ml of blood per minute directly from the abdominal aorta which amounts to 20% of the cardiac output.

Question 11

What are the branches of the renal arteries?

Answer 11

The renal arteries branch into 5 segmental arteries which divide further into lobar arteries then further into interlobar arteries which pass between the renal pyramids. The interlobar arteries then divide into the arcuate arteries which branch into several interlobular arteries that feed into the afferent arterioles that supply the glomeruli. After filtration occurs the blood moves into the efferent arterioles and either the peritubular or vasta recta capillaries and then drain into interlobular veins which converge sequentially into arcuate then interlobar veins then to the renal vein which exits the kidney

Question 12

Why are the kidneys are innervated by many blood vessels?

Answer 12

So that they can filter the blood to regulate its composition.

Question 13

How do the kidneys and the nervous system collaborate?

Answer 13

They interact via the renal plexus whose fibers follow the renal arteries to reach the kidney. Input from the sympathetic nervous system adjusts the diameter of the renal arteries thereby regulating renal blood flow.

Question 14

What is the pathway of blood from the renal artery to the renal vein within the kidney?

Answer 14

Renal Artery → Segmental Artery → Lobar artery → Interlobar Artery → Arcuate Artery → Interlobar Artery → Afferent arteriole, (8) Glomerular capillaries, (9) Efferent arteriole, (10) Peritubular or Vasa recta capillaries, (11) Interlobular vein, (12) Arcuate vein, (13) Interlobar vein, (14) Renal vein

Question 15

What is the basic structural and functional unit of a kidney and how many are there in each kidney?

Answer 15

The nephron - there are about a milliion present in each kidney.

Question 16

What are the functions of a nephron?

Answer 16

To control the concentration of water and soluble materials by filtering the blood, reabsorbing needed materials and excreting the rest as urine thereby eliminating wastes from the body, regulating blood volume, pH and pressure, controlling levels of electrolytes.

Question 17

What are the two parts of a nephron?

Answer 17

The Renal corpuscle and the Renal tubule, which are connected, by way of the tubule to associated collecting ducts.The renal corpuscle filters the blood, the renal tubule reabsorbs needed materials and the collecting ducts carry the remaining material away as urine to be excreted.

Question 18

What composes the renal corpuscle of the nephron?

Answer 18

The glomerulus which is a tiny network of blood capillaries surrounded by the glomerular Bowman’s capsule,a double-walled simple squamous epithelial cup.

Question 19

What is unique about the glomerular capillaries?

Answer 19

They are extremely porous and are the only arteriolds in the body which lie between two arterioles. (the afferent arteriole and the efferent arteriole) rather than between an artery and a vein.

Question 20

What is the difference between afferent and efferent arteriole?

Answer 20

The afferent arteriole brings blood to the glomerulus and the efferent arteriole takes blood away from the glomerulus.

Question 21

What causes blood to exit the blood and go into the glomerular (Bowman’s) capsule ?

Answer 21

The afferent arteriole, which is fed by the interlobular artery, is much larger in diameter than the efferent arteriole causing an extremely high blood pressure in the glomerular capillaries forcing water and solutes out of the blood and into the glomerular capsule (as glomerular filtrate) and subsequently into the renal tubule.

Question 22

What are the three parts of the renal tubule ?

Answer 22

The proximal convoluted tubule, the loop of Henle and the distal convoluted tubule.

Question 23

What does the proximal convoluted tubule do ?

Answer 23

The highly coiled proximal convoluted tubule which is specialized to reabsorb water and many solutes from the glomerular filtrate into the low-pressure peritubular capillaries which surround the renal tubule as well as secrete certain unwanted substances.

Question 24

What does the loop of Henle do ?

Answer 24

The loop of Henle has an initial descending limb followed by the ascending limb. The descending limb allows water loss and the ascending limb allows salt (NaCl) loss.

Question 25

What does the distal convoluted tubule do ?

Answer 25

The highly coiled distal convoluted tubule allows hormonally controlled reabsorption of water and solutes but mostly secretion of unwanted substances

Question 26

What happens to the filtrate as it makes it way through the tubule of the nephron?

Answer 26

The filtrate (which is now urine) from several tubules then drains into a collecting duct, many of which converge to form papillary ducts which drain into the calyces and subsequently into the renal pelvis and out of the kidney by way of the ureter.

Question 27

Where are the nephrons of the kidney located ?

Answer 27

Most (about 85%) of the kidney nephrons are located mainly in the cortex (except for a portion of their loop of Henle which extends into the medulla). The remaining nephrons, called juxtamedullary nephrons, pass deeply into the medulla because of their location and their longer loops of Henle.

Question 28

What three capillary beds are nephrons associated with?

Answer 28

the glomerular capillaries, the peritubular capillaries and the vasa recta

Question 29

Talk about the glomerular capillaries…

Answer 29

They are very porous and They have a high pressure , which makes them specialized for filtration. These properties force solutes and fluids out of the blood into the Bowman’s (glomerular capsule)

Question 30

Approx what percent of the glomerular filtrate is reabsorbed through the renal tubule?

Answer 30

99% is reabsorbed and returned to the blood in the returned to the blood in the peritubular capillary bed.

Question 31

Peritubular capillaries…

Answer 31

These arise from the efferent arterioles as they leave the glomerulus. The peritubular capillaries closely follow the renal tubules and drain into the interlobular vein. Because of their porosity and low pressure, the peritubular capillaries are adapted for absorption reclaiming water and solutes from the filtrate.

Question 32

Vasa Recta capillaries…

Answer 32

This third set of capillaries known as the vasa recta follow the loops of Henle of the juxtamedullary nephrons in the medulla.

Question 33

What three processes must occur for urine formation?

Answer 33

Filtration, reabsorption and secretion. Filtration takes place in the renal corpuscle of the nephron. Reabsorption and secretion take place in the renal tubules.

Question 34

How many gallons of glomerular filtrate are removed daily from the blood plasma? How much is reabsorbed and how much becomes urine?

Answer 34

About 47 gallons of glomerular filtrate containing the water, nutrients, and essential ions are removed daily from the blood plasma; but by the time filtrate has entered the collecting ducts, it has lost most of its water, nutrients, and essential ions and now is about 0.5 gallon of urine, containing mostly wastes with the other 99% being returned to the blood

Question 35

How often do the kidneys filter the entire blood plasma per day?

Answer 35

about 60 times each day- about 25% of the resting body energy is used to subsequently excrete the wastes as urine

Question 36

What kind of filtration is the glomerular filtration ?

Answer 36

Filtration in the glomerulus takes place across the very porous membrane that lies between the capillaries and the interior of the glomerular capsule. Mechanical because it filters according to size. It doesn’t require energy- in which fluids and solutes (such as water, glucose, amino acids, and nitrogenous wastes) are forced through the membrane by the high hydrostatic blood pressure in the capillary bed.

Question 37

What is the formula for urinary excretion?

Answer 37

Filtration- resabsorption + secretion = excretion

Question 38

What is GFR ? What is its normal rate ? What enables the GFR?

Answer 38

Glomerular filtration rate. The normal GFR is 120-125 ml/min or 180 L/day. This is enabled by the huge surface area of glomerular capillaries, the large degree of filtration membrane permeability and the moderate net filtration pressure.

Question 39

What increases and decreases the glomerular filtraion

Answer 39

The GFR is increased by an increase in the arterial (and glomerular) blood pressure in the kidneys and is decreased by an increase in glomerular osmotic pressure most often caused by dehydration.

Question 40

Why is it important to maintain a relatively constant GFR?

Answer 40

Maintenance of a relatively constant GFR is important for adequate reabsorption of water and other needed substances from the filtrate and filtration of wastes since if flow is very rapid, needed substances cannot be adequately reabsorbed and if flow is too slow nearly all of it is reabsorbed, including most of the wastes that are normally disposed of.

Question 41

What are three mechanisms that regulate the renal flow and thereby, the GFR?

Answer 41

Renal autoregulation, nervous system control and hormone control.

Question 42

What does renal autoregulation entail?

Answer 42

The kidney controlling its own rate of blood flow. through the regulation of the diameter of the afferent and the efferent arterioles. By means of this autoregulatory system, the kidney can maintain a fairly constant GFR despite variations in the arterial blood pressure of the rest of the body.

Question 43

How does the nervous system work to control the renal blood flow?

Answer 43

Occasionally it becomes necessary to divert blood to the heart, brain and skeletal muscles and during these times the renal autoregulatory system may be superseded by nervous system controls. In this event, a narrowing of the afferent arterioles is caused by sympathetic nerve fibers and release of epinephrine by the adrenal medulla with a subsequent decrease renal flow and the GFR

Question 44

How does hormone control regulate the GFR?

Answer 44

A third mechanism, one that is hormonal in nature, controls the renal flow. This is the renin-angiotensin mechanism in which the enzyme renin is released by the juxtaglomerular cells in response to a drop in the body’s blood pressure or direct stimulation of the JG cells by the renal sympathetic nerves. Renin causes constriction of the afferent and efferent arterioles, a rise in the body’s blood pressure and also stimulates the release of aldosterone thereby causing the renal tubules to reclaim more sodium ions (and subsequently water) from the filtrate. All of these effects result in an increased GFR and reabsorption of more water and sodium from the filtrate.

Question 45

What happens to most of the contents of the glomerular filtrate which enter the renal tubule?

Answer 45

Most is reabsorbed back into the blood of the peritubular capillaries. Otherwise the entire plasma would be drained away as urine within an hour.

Question 46

What are the three membrane barriers that reabsorbed substances must go through to enter into the peritubular capillaries?

Answer 46

the luminal and basolateral membranes of the renal tubules and the endothelium of the peritubular capillaries.

Question 47

What substances of the glomerular filtrate are actively reabsorbed in the renal tubule?

Answer 47

Substances reclaimed by active tubular reabsorption including glucose, amino acids, lactate, vitamins, and most ions (particularly Na+) move by diffusion into the tubule cells and then are actively carried into the interstitial space between the tubule and the peritubular capillaries. The substances then move passively into the peritubular blood because of its low hydrostatic pressure Organic nutrients such as glucose and amino acids are completely reabsorbed to maintain or restore normal plasma concentrations. Reabsorption of water and many ions are hormonally regulated and may be passive or ATP-driven. Substances reclaimed by passive tubular reabsorption (diffusion, facilitated diffusion, and osmosis, no use of ATP) do so to follow Na+ ions which were actively reabsorbed. This is the case for most negatively charged anions such as Cl- which diffuse into the peritubular capillaries to restore electrical neutrality both in the filtrate that they leave and plasma of the peritubular capillaries. Water also moves passively into the peritubular capillaries by osmosis because of the difference in osmotic pressure established by the movement of Na+ ions. As water leaves the renal tubules, it creates a concentration gradient which causes other substances such as urea to move to the peritubular capillaries by osmosis.

Question 48

What happens if the active carriers of a substance become saturated (all bound to the substance they transport) ?

Answer 48

The substance, even though it normally is absorbed, will be abnormally excreted in urine. even though the renal tubules are still functioning normally. his is the cause of large amounts of glucose being lost in the urine of individuals with uncontrolled diabetes mellitus.

Question 49

What substances are not reabsorbed and why ?

Answer 49

Some substances such as creatinine, and uric acid which are nitrogenous end products of protein and nucleic acid metabolism are not reabsorbed either because they lack carriers, are lipid insoluble or are too large to pass through membrane pores of the tubule cells.

Question 50

Urinary bladder characteristics

Answer 50

Hollow, muscular, flexible pouch that stores urine. Both ureters empty into it. Has three tissue layers- outer adventitia is a fibrous connective tissue, the middle layer is the detrusor muscle with inner/outer longitudinal layers and middle circular layer, the inner mucosal layer is composed of transitional epithelium.

Question 51

How much urine can a bladder hold?

Answer 51

The bladder is pyramidal shaped when empty but swells when storing urine to become pear shaped. When full it can hold about 500 ml but if necessary, the bladder can hold about 1000 ml.

Question 52

What is the trigone in the urinary bladder?

Answer 52

The smooth, triangular center region of the bladder

Question 53

How does the bladder hold various amounts of urine?

Answer 53

It is flexible and elastic- the muscular tissue layer of the detrusor is able to stretch and thin to allow varying amounts of urine to be store. The bladder is pyramid shaped when empty but swells to become pear shaped upon increasing amounts of urine. This function allows the bladder to store more urine without an increase in internal pressure.

Question 54

What is micturition known as ?

Answer 54

aka Urination, the act of emptying the bladder

Question 55

Which branch of the renal artery goes between the pyramids of the renal medulla?

Answer 55

The interlobar arteries

Question 56

Which arteries feed the afferent arterioles which feed the glomerulus?

Answer 56

The interlobular arteries

Question 57

Multiple nephrons join together at __________

Answer 57

The collecting ducts

Question 58

The filtration pressure is controlled by what two pressures-

Answer 58

The Blood Hydrostatic pressure (how much is the pressure inside the capillary) and the Blood colloid osmotic pressure(based on presence of proteins in filtrate )

Question 59

What vessels can the kidney control to perform its autoregulation of the Glomerular filtration rate ?

Answer 59

It can control the diameter of the Afferent Arteriole, the diameter of the Glomerulus and the diameter of the Efferent arteriole

Question 60

Vasoconstriction

Answer 60

In nervous system regulation of the GFR, The adrenal gland releases epinephrine and causes a decrease in the GFR. If this reaction is long term, it can causes hypoxia to glomerular cells and kidney damage

Question 61

The RAA system is in place to …..

Answer 61

cause a rise in blood pressure when the kidney detects abnormally low blood pressure. The Renin-Angiotensin-Aldosterone System (hormonal control of the GFR)

Question 62

In the descending limb of the loop of Henle

Answer 62

there are specialized pores that allow water to come through and not salt. This creates various pressures called osmotic pressures of this portion of the medulla

Question 63

The Distal convoluted membrane is very sensitive to the

Answer 63

hormone Aldosterone

Question 64

Proximal Convoluted Tubule Absorption Characteristics

Answer 64

Greatest amount of renal tubular reabsorption occurs in the PCT. all of the glucose and amino acids are reabsorbed and about 65% of the Na+, 65% of the water, 90% of the bicarbonate (HCO3-), 50% of the chloride (Cl-) and 50% of potassium (K+) are reclaimed from the glomerular filtrate along with most of the calcium (Ca+2), phosphate (PO4-3) and magnesium (Mg+2).

Question 65

Loop of Henle Characteristics

Answer 65

A descending limb that allows for water loss. A ascending limb that allows for NaCl loss. This regulates the kidney’s ability to form dilute and concentrated urine another 25% of the Na+, 15% of the water, and 40% of the K+ is reabsorbed into the peritubular capillaries.

Question 66

Distal Convoluted Tubule and the Collecting Ducts

Answer 66

After reabsorption in the proximal convoluted tubule and the loop of Henle, about 10% of the Na+ and Cl- and 20% of the water remain in the filtrate once it reaches the DCT. Hormones have a target effect on this region of the tubule. Hormones can reclaim nearly all of the water and Na+ when necessitated by abnormal blood pressure or blood volume or low Na+ concentration or high K+ concentration in the extracellular fluid.

Question 67

What is ADH?

Answer 67

Antidiurectic Hormone , secreted by the posterior pituitary, causes the collecting ducts to become more permeable with the subsequent reabsorption of more water into the peritubular capillaries. It promotes water retention and a much more concentrated urine.

Question 68

What is aldosterone?

Answer 68

A hormone secreted by the posterior pituitary gland that causes collecting ducts to become more permeable with the subseqent reabsorption of more water into the peritubular capillaries.

Question 69

What happens in tubular secretion?

Answer 69

This is the last process of the excretion process. Certain unwanted substances within the peritubular capillaries must be secreted back into the filtrate. This includes urea and uric acid, excessive potassium ions, drugs like penicillin, bicarbonate ions and H+ to control blood pH. Substances move from the blood of the peritubular capillaries through cells in all sections of the tubule and cortical collecting ducts into the filtrate.

Question 70

In the end urine is a composition of _______

Answer 70

Filtration, Reabsorption and Secretion processes combined

Question 71

Body needs ……..

Answer 71

Constant Solute Concentration Not to lose H20 in urine Maintain homeostasis , that steady state

Question 72

What is osmotic concentration?

Answer 72

The amount/concentration of solutes that are in the filtrate filtrate or in the blood

Question 73

What happens as you move down the descending limb of the loop of Henle

Answer 73

The osmotic pressure increases because while water is leaving, salt is not able to leave, which increases the osmotic pressure

Question 74

What is countercurrent flow?

Answer 74

The flow of filtrate is one way within the loop of Henle and the flow of blood within the adjacent Vasa Recta capillaries is the opposite way. This flow maintains an osmotic gradient that allows for the kidneys to greatly vary urine concentration to maintain body fluid homeostasis.

Question 75

Maintaining the osmotic gradient in the loop of Henle is important because ………

Answer 75

allows the filtrate to be more concentrated. The osmotic gradient helps control what flows in and out of the filtrate.

Question 76

What is the solute concentration of the filtrate as it begins to go down the descending limb?

Answer 76

The solute concentration of the filtrate is 300 mosm at the beginning of the descending limb, 1200 mosm at the hairpin turn and 100 mosm at the top of the ascending limb where it becomes the distal convoluted tubule. The result of these concentration differences is the establishment of a gradient of about 900 mosmol in the surrounding interstitial fluid of the cortex (lower osmolaity) and the inner medulla (higher osmolarity).

Question 77

What maintains the renal medulla gradient ?

Answer 77

The renal medulla gradient is maintained by the vasa recta which parallel the juxtamedullary loops of Henle. These capillaries know as vasa recta contain hairpin loops and carry blood at a very slow rate enabling them to passively interact with the surrounding interstitial fluid which maintains the gradient which has been established in the medullary interstitial space

Question 78

In what conditions is ADH released?

Answer 78

ADH is released in response to dehydration conditions (such as excessive water loss through sweating or diarrhea, or reduced blood volume or blood pressure or hemorrhage) so as to allow the body to retain up to 99% of the water in filtrate.

Question 79

What do diuretics do ?

Answer 79

Diuretics cause a greater flow of urine and therefore increase urinary output.

Question 80

Why is urine concentration and volume altered by the kidneys?

Answer 80

To maintain a relatively constant total solute concentration of body fluids. This is accomplished by the countercurrent flow of filtrate through the loop of Henle and the flow of blood through the limbs of its adjacent vasa recta blood vessels.

Question 81

What color is urine?

Answer 81

A pale, clear to deep yellow color depending on hydration of body. Yellow is caused by pigment urochrome, which is a byproduct of the metabolic breakdown of hemoglobin. Abnormal colors may result from drugs or foods like beets or rhubarb or be caused by the presence of bile pigments or blood in the urine. Cloudy urine (due to the presence of pus) may indicate a urinary tract infection.

Question 82

What is the normal pH of urine?

Answer 82

4.5- 8.0 with a diet high in citrus, vegetables, or dairy causing a higher (basic) pH and a diet high in protein causing a lower (acidic) pH.

Question 83

What is the chemical composition of urine?

Answer 83

Urine contains about 95% water with about 5% solutes of varying amounts of which the most abundant is usually urea (~2%) one of several nitrogenous wastes which also include uric acid, creatinine and ammonia. Other common solutes of urine include sodium, potassium, phosphate, and sulfate calcium, magnesium, chloride and bicarbonate ions.

Question 84

Ureters

Answer 84

Carry urine from the kidneys to the urinary bladder. Are composed of 3 tissue layers- The inner lining, made of transitional epithelium, is continuous with the kidney’s lining. The middle layer is two sheets of muscle, one longitudinal and the other circular. The outer adventitia layer is fibrous connective tissue. Contains ureterovesical sphincters to help prevent the backward flow of urine toward the kidney

Question 85

Question 86