Chapter 26: The Urinary System

59. Reabsorption processes are linked to the concentration gradient set up for SODIUM ions.

Energy needed to make things move comes from the movement of sodium ions.

27. What are fenestrae?

Fenestrae refer to the large pores located between the endothelial cells of the glomerular capillaries that let materials of a certain size pass through.

Filtration

Occurs when blood pressure nonselectively forces water and other small molecules out of glomerular capillaries and into the Bowman capsule forming a fluid called filtrate.

Ammonia

When bacteria starts to grow in urea, ammonia is made. Unchanged diapers can lead to ammonia formation which leads to diaper rash.

Blood pressure and urine

When blood pressure increases, urine production increases.

Juxtaglomular cells

Form a cufflike arrangement around the arteriole where the afferent enters the RC.

DCT

Join to form a single collecting duct which forms much of the medullary rays and extend through the medulla toward the tips of the renal pyramids.

7 How does perirenal fat function in kidney protection?

Perirenal adipose tissue surrounds the renal capsule and acts as a cushion for the kidney against mechanical shock. The fat also insulates the organ against the loss of heat. Also supplies some cushioning for the kidney.

12. Describe the kidney medulla.

The medulla makes up more of the volume of the internal kidney. Medulla is made up of cone shaped structures called renal pyramids. Medullary rays extend from renal pyramids into cortex. Renal columns project between renal pyramids.

47. Filtration pressure is equal to GLOMERULAR CAPILLARY pressure minus CAPSULE pressure minus COLLOID OSMOTIC pressure.

-Glomerular Capillary Pressure (GCP)=an outward pressure from blood pressing against the capillary walls (aka blood pressure). Forces fluid and solutes out of blood and into Bowman's capsule. -Capsular hydrostatic pressure (CHP)=an inward pressure from the pressure of filtrate accumulation in the Bowman's capsule. -Blood Colloid Osmotic Pressure (BCOP)=inward pressure due to osmotic force of plasma protein within the glomerular capillaries. Proteins resist fluid movement from glomerular capillary into the Bowman's Capsule. Is greater at the end than the beginning of the capillary because of fluid loss and increase in protein concentration.

16. What is the structural and functional difference between juxtamedullary and cortical nephrons?

-The function of juxtamedullary nephrons is to make a more concentrated urine by having longer loops of Henle. Urine is more concentrated. Increase with age. -The function of cortical nephrons is to form a more watery urine by having shorter loops of Henle. Urine is less concentrated. -A typical adult kidney is made up of 15% juxtamedullary nephrons and 85% cortical nephrons.

1. How does the urinary system do the following: (a) regulate blood volume? (b) determine the concentration of blood solutes? (c) determine the pH of extracellular fluid? (d) control blood cell synthesis?

-keeps blood volume stable by controlling the amount of water carried in the plasma. -controls the concentration of blood solutes by either keeping or removing ions like sodium or potassium. -maintains the proper pH of body fluids by keeping or removing hydrogen ions. (7.35) -participates in making red blood cells by secreting a substance called erythropoietin.

25. What is the tubular pathway that the filtrate moves through where reabsorption and secretion occur?

1. Proximal convoluted tubule (PCT) 2. Descending Loop of Henle (DLH) 3. Ascending Loop of Henle (ALH). Is very important for secretion. 4. Distal convoluted tubule (DCT) 5. Collecting tubule (CT)

15. What is the correct 5 structure pathway for urine production and removal?

1.The calyces 2.The renal pelvis (surrounds renal sinus) 3.The ureter (exits the kidney at the hilum) 4.The urinary bladder 5.The urethra

60. At the end of the proximal convoluted tubule (PCT), the volume of the original amount of filtrate is reduced by ___ % by reabsorption processes.

65%

58. What percent of reabsorption occurs in the proximal convoluted tubule?

99%

18. What are the two layers of Bowman's capsule?

A Bowman's capsule is made up of a parietal layer and a visceral layer. The visceral layer is constructed of specialized cells called podocytes which wrap around the glomerular capillaries.

9. Why is a floating kidney dangerous?

A floating kidney can be dangerous because the ureters or blood vessels can become twisted leading to kidney malfunction.

14. What is a renal papilla?

A papilla is the tip of a renal pyramid. • A renal pyramid is the blood filtration apparatus found within a kidney. • There are usually 8-10 renal pyramids in a kidney. • As urine is formed, it "drips" off of the renal papillae into the minor calyces. Urine is made 24-7. • Urine is made continually, sometimes more and sometimes less.

6. What is the renal capsule?

A renal capsule is a tough collagen fiber sac that surrounds each kidney.

17. What two structures make a renal corpuscle?

A renal corpuscle is made up of a cup-shaped Bowman's capsule and a structure that looks like a "bird's nest" which is called a glomerulus located within Bowman's capsule.

20. What is the difference between afferent and efferent arterioles?

An afferent (LARGER) arteriole carries blood into the glomerulus and an efferent (SMALLER) arteriole carries blood away from the glomerulus. Is responsible for making the blood flow through the Renal corpuscle standard and unchanging. Changes in diameter of these arterioles can manage this.

62. The wall of the descending Loop of Henle is permeable to both WATER and some solutes.

As loop of henle descends the wall transforms to simple squamos in the thin segment. Thin segment is highly permeable to water and moderately permeable to urea, Na, and most other ions. Loop of Henle descending and ascending portions is in the medulla of the kidney.

Regulation of Glomerular Filtration Rate

Autoregulation= Maintenance of a very stable glomerular filtration rate (GFR) despite wide fluctuations in sytemic pressure. Is achieved by two processes: Myogenic mechanism and tubuloglomerular feedback.

41. Bladder control involves the voluntary control of which sphincter valve?

Bladder control involves learning to control the voluntary external sphincter valve. Urinary stress incontinence is a malfunction of the external sphincter valve and can be surgically repaired.

Permeability of capillaries

Capillaries have fenestrae (window like openings) and filtration slits (gaps) make the visceral layer of Bowman capsule. The filtration membrane is the capillary endothelium, basement membrane, and podocytes.

52. Define capsule pressure.

Capsule pressure occurs when there is diffusion of other materials besides water out of the filtrate back into the blood of the glomerulus. • Capsule pressure has a value of 10 mm Hg.

51. Define what creates colloid osmotic pressure.

Colloid osmotic pressure happens when water moves from an area of high concentration to an area of low concentration. During filtration, water was forced from the blood into Bowman's capsule and because the water is then more concentrated inside the capsule, it will attempt to move back into the blood of the glomerulus. • Colloid osmotic pressure has a value of 28 mm Hg.

Urinary System

Consists of two kidneys, two ureters, which carry urine from the kidneys to the urinary bladder, a single midline urinary bladder, and a single urethra.

Structure of the nephron

Consists of: 1. renal corpuscle - filters the blood (RC) 2. proximal convoluted tubule - returns filtered substances to the blood (PCT) 3. loop of henle - conserve water and solutes (LOH) 4. distal convoluted tubule - rids blood of additional wastes (DCT)

Tubulogloerular feedback mechanism

Correlates filtrate flow past the macula densa of the juxtaglomerular apparatus to GFR. When densa cells detect increased flow rate cells send a signal to juxtaglomerular cells of afferent arteriole to constrict.

Kidney functions

Excretion, regulation of blood volume and pressure, regulation of the concentration of solutes in the blood, regulation of extracellular fluid pH, regulation of red blood cell synthesis, and regulation of vitamin D synthesis.

21. What is filtrate?

Filtrate is defined as the collection of different substances that leave the blood from the glomerulus and enter through the pores of Bowman's capsule.Glucose, water, ions, amino acids are small enough to go through the pores so are part of the filtrate. Blood cells, proteins, and lipids are too large for the pores so should not be found in the urine.

44. Define filtration. Filtrate formation depends of a ___ gradient.

Filtration is the process in which material from the blood is forced across the filtration membrane into Bowman's capsule. How much filtrate that is formed depends on a pressure difference or gradient between the blood and the pressure within Bowman's capsule.

50. Define what creates the glomerular capillary pressure.

Glomerular capillary pressure comes from blood pressure created by the heart as well as from the constriction and dilation of the afferent and efferent arterioles of the glomerulus. • Glomerular capillary pressure has a normal value of 45 mm Hg. (millimeters mercury)

Loop of Henle

Has an ascending limb and a descending limb.

2. The urinary system is involved with the synthesis of what vitamin?

Helps in making Vitamin D by making precursor molecules that will later be formed into Vitamin D.

55. How does constriction of the afferent arteriorle affect filtration pressure?

If an afferent arteriole constricts, the lack of blood flow through the glomerulus leads to decreased filtration pressure in the glomerulus. The constriction and dilation of the kidney arterioles function in autoregulation of kidney function keeping the effective filtration pressure at 7 mm Hg.

68. If the membranes of the distal convoluted tubule (DCT) and the collecting tubule (CT) are permeable to water, then water will move back into the blood and not end up as urine. What would be the situation if the membranes of the DCT and the CT are not permeable to water?

If the membranes of the distal convoluted tubule and collecting tubule are not permeable to water, then the water stays within the tubules and forms urine.

Myogenic Mechanism

Includes the afferent and efferent arterioles. Smooth muscles act as stretch receptors.

The kidneys anatomy

Is bean shaped and size of a closed fist. Sorts substances from the blood for either removal in the urine or return to the blood.

Proximal Convoluted Tube

Is responsible for the majority of reabsorption. As solute molecules are transported from the nephron to the interstitial fluid, water moves by osmosis in the same direction.

Juxtaglomerular apparatus

Juxtaglomerular cells of afferent arteriole and macula densa cells together are called juxtaglomerular apparatus. Secretes enzyme renin and plays important role in regulation of filtrate formation and blood pressure.

Kidney stones

Known as calculus. Is a solid crystal aggregation. Leading cause of kidney stones is a lack of water. When there is not enough water to dilute the uric acid (component of urine) the pH level in a kidney drops which makes environment in kidney acidic leading to formation of stones. Usually small enough to pass out of the body with the urine, however they can grow to sufficient size and block a ureter. Blocked ureter causes intense pain, most commonly felt in lower back, lower abdomen, and in the groin. Intermittent pain corresponds to the periodic peristaltic contractions of the ureter.

Macula densa

Lying between the afferent and efferent arterioles adjacent to the RC is part of the DCT of the nephron. Cells in this section are the macula densa.

13. Contrast the job and location differences of the major and minor calyces.

Major calyces (plural) or a calyx (singular) are the largest of the drains found within the medulla of the kidney. Calyces drain urine into the collection areas of the kidney. • Urine, which collects in the major calyces, will be moved to the kidney pelvis before it is moved down to the urinary bladder. There are 8-20 minor and 2-3 major calyces • Minor calyces are the smaller of the drains and several of them will join to form a major calyx. Are funnel shaped chambers into which renal papillae extend. • Urine collects in the minor calyces first before it is collected in the major calyces.

63. Water is moved by osmosis from the interior of the descending Loop of Henle and it enters a blood vessel called the VASA RECTA, which collects the water and solutes and carries them away so they cannot collect in the medulla area.

Medulla has to be constant so vasa recta keeps the water from changing the medulla environment.

Papillary ducts

Near the tip of the renal papilla, several collecting ducts merge into a larger-diameter tubule called a papillary duct, which empties into a minor calyx. The RC, PCT, and DCT are located in renal cortex. Collecting ducts, parts of LOH, and papillary ducts are in the renal medulla.

Preeclampsia

Occurs only during pregnancy and the postpartum period and affects both the mother and the unborn baby. Affects 5-8% of all pregnancies. Is a rapidly progressive condition characterized by high blood pressure and the presence of protein in the urine.

Glomerular Nephritis

Permeability of the filtration membrane increases and more protein than normal enters the filtrate increasing COP which results in increased filtration pressure and increase in filtrate volume.

46. Compare the protein composition of filtrate materials that reenter the blood to the filtrate material that enters Bowman's capsule.

Plasma reentering the blood behind the filter is higher in protein than the filtrate entering Bowman's capsule. That is logical because most of the protein molecules are too large to pass through the filtration membrane and so they stay in the plasma and go back into the blood stream.

26. What are podocytes?

Podocytes are specialized cells found in the inside layer of Bowman's capsule that function as filters in the formation of filtrate.

Filtration Membrane in the nephron

Prevents blood cells and proteins from entering the lumen of Bowman capsule. Is more permeable than a typical capillary. Is comprised of: 1. Fenestrae of golmerular capillary 2. Basement membrane between the capillary wall and the visceral layer of Bowman capsule 3. Podocytes of visceral layer of Bowman capsule

23. Define reabsorption.

Re-absorption is the process of returning material collected in the filtrate back into the blood. Occurs when nephron specifically returns water and some filtered substances to the blood.

29. What is renal blood flow per minute?

Renal blood flow through both kidneys is 1200 ml or 1.2 liters of blood/minute. • This means that a person's entire 10-12 pints of blood would pass through their kidney filters every 7-9 minutes.

Arteries and veins of the kidneys

Renal vein exits and joins the inferior vena cava. Associated with the juxtamedullary nephrons are specialized sets of capillaries called vasa recta.

Urine production

Scientists categorize urine formation into three major processes: filtration, tubular reabsorption, and tubular secretion

24. Define secretion.

Secretion is the process of adding certain substances to the filtrate that were not part of the original filtrate.

Proteinuria

Signs and symptoms include: Swelling/edema of the body around the face, hands, and feet. Foamy or bubbly urine. High blood pressure.

66. As the remaining filtrate moves up the ascending Loop of Henle, some solutes will be reabsorbed but not water. Why not?

Since all portions of the ascending loop of Henle are impermeable to water, no water will be reabsorbed here. The thin portion of the ascending loop of Henle is permeable to solutes so some will be diffused into the more dilute interstitial fluid.

53. After colloid osmotic pressure and capsule pressure is subtracted from glomerular capillary pressure, what is the effective filtration pressure?

So effective filtration pressure is calculated by taking glomerular capillary pressure and subtracting colloid osmotic pressure and capsule pressure. • 45 mm Hg - 28 mm Hg - 10 mm Hg = 7 mm Hg • Effective filtration pressure ends up with a value of 7 mm Hg. Glomerular pressure changes affect filtration pressure the most. • Any drastic deviations from the 7 mm Hg will lead to kidney malfunction and can be a health risk.

UTI

Statistically, 1 out of 5 females will develop a urinary tract infection sometime during her lifetime. • Men are 20 times less likely to have a urinary tract infection than a female but a UTI in a male is a more serious infection due to involvement of the prostate gland. • Scientists are somewhat unsure why more females develop urinary tract infections but having a shorter urethra and the closeness of the urethral opening to the vaginal and anal openings may be factors.

11. Describe the kidney cortex.

The cortex is the outside layer and the medulla is the inside layer of the kidney. The cortex is lighter in color than the darker medulla. Amount of blood involved is more than likely the reasoning behind the color difference.

Filtration factors

The driving force of filtration is blood pressure. The importance of filtration is indicated by the large percentage of total cardiac output (blood) that is sent through the kidneys compared with other body organs. The portion of total cardiac output that flows through the kidneys is called renal fraction. It varies from 12 to 30% but averages 21%.

37. Compare the lengths of the urethras in males and females.

The female urethra is 1-2 inches in length and is used to carry urine out of the body. The male urethra is 8-9 inches in length and is used to carry either urine or semen out of the body.

30. What is the function of a ureter?

The function of a ureter is to transport urine from the kidney down to the urinary bladder.

36. What is the function of a urethra?

The function of a urethra is to transport urine from the urinary bladder to the outside.

19. What is a glomerulus? Where is it located? What is the job of a glomerulus?

The glomerulus is a group of blood capillaries that has the function of filtering the blood. Is located inside of the Bowman's capsule. Fluid is filtered from glomerulus into the Bowman's capsule then fluid moves to PCT and is carried away from Bowman's capsule.

10. Define the hilum of a kidney. What structures enter and leave the kidney at the hilum?

The hilum is the indentation on the medial wall of the kidney where the renal artery, renal vein and ureter enter and leave the kidney. Nerves also enter here. Hilum opens up into the renal sinus, a cavity filled with adipose tissue and connective tissue. Structures that enter and leave the kidney pass through the renal sinus.

34. What is the location of internal sphincter valve in relation to the urinary bladder?

The internal sphincter valve is located at the inferior end of the bladder where the urethra joins the bladder. Is only in males. The internal sphincter valve keeps urine in the bladder but will be opened automatically when the capacity of the bladder reaches a certain amount. • The opening and closing of the internal sphincter valve is controlled by the autonomic nervous system.

40. What is the difference in control of the internal sphincter valve and the external sphincter valve?

The internal sphincter valve is under involuntary control meaning that the valve will open automatically when the person decides to relax the external sphincter valve voluntarily.

8. What is the job of renal fascia?

The job of renal fascia is to attach the kidney to the back of the abdominal wall. Is a thin layer of connective tissue. Adipose tissue surrounds the renal fascia.

28. What structures form the juxtaglomerular apparatus?

The juxtaglomerular apparatus is formed by the union of the distal convoluted tubule and the afferent arteriole.

4. Why is the kidneys called retroperitoneal organs?

The kidneys are retroperitoneal organs because they are located behind the parietal peritoneum

45. What kinds of materials make filtrate?

The material called filtrate is made of everything in the blood except for blood cells and plasma proteins, which are too large to go through the tiny holes in the filtration membrane.

49. What kinds of materials are permitted to pass through the glomerular membrane? Because of this, urine (should; should not) ____ contain protein.

The membrane of the glomerulus will only allow the very smallest molecules to pass through, so with that fact in mind, urine should not contain protein.

35. How does the entry points of ureters into the bladder help to prevent "back-flow" of urine into the ureters?

The openings to the ureters are found on the back wall of the bladder because: • so as the bladder fills with urine, the openings to the ureters are pinched closed by the pressure of the accumulating urine. • The pinching off of the ureter openings prevents urine from moving back into the ureters from the urinary bladder and possibly carrying infectious material back up to the kidneys.

5. Which kidney is slightly lower than the other one?

The right kidney is slightly lower than the left because the liver has more dominance on that side of the body.

33. What structures compose the trigone?

The trigone is a term that refers to the triangular arrangement of the two openings of the ureters and the one opening of the urethra found within the urinary bladder. Urinary bladder can hold 1000 ml or more of urine but an over filled urinary bladder should be avoided because stretching causes a loss of tone in the bladder wall.

32. What is the normal storage amount In the urinary bladder?

The urinary bladder normally stores about 400-500 ml of urine before the body feels a need to void. The bladder, however, can hold 1000 ml or more of urine. • A distended bladder should be avoided because stretching of the bladder causes loss of tonicity of the bladder wall. • The bladder wall should help push urine out and the loss of tone may complicate urination.

Ascending loop of henle

Thin segment is more permeable to solutes but impermeable to water. Therefore no additional water exits. Thick segment is not freely permeable to water or solutes (Na, K, and Cl) so they must be actively transported from thick segment to interstitial fluid. Symport is responsible for moving K and Cl with Na across apical membrane.

64. By the time the filtrate reaches the bottom of the Loop of Henle, 15% of the filtrate is removed leaving 20%, leaving the remaining filtrate MORE "salty".

This 20% is what is used to make urine.

42.What process begins urine formation?

Urine formation begins with a process called filtration.

DCT Reabsorption

Water permeability is not constant in the DCT and collecting duct but varies on hormone regulation. Reabsorption of water is via osmosis across DCT wall and collecting duct when ADH is present. ADH causes tubule wall to become more permeable to water.

31. What process moves urine through ureters toward the urinary bladder?

Wave-like contractions called peristaltic contractions occur about every 30 seconds in the wall of the ureter to force 1-2 milliliters of urine down into the urinary bladder.

22. What two processes work on filtrate within the tubular network of a nephron?

Within the tubular network following Bowman's capsule two processes, reabsorption (happens first) and secretion (second) work on the filtrate in the tubular network of the nephron to create urine. What is left over is urine.

NEPHRON

is the histological and functional unit of the kidney. Each kidney contains one to two million nephrons.

3. The urinary system excretes metabolic waste. What is metabolic waste?

rids the body of cellular waste, such as urea and creatine.

43. What process occurs after filtration? Which process completes the process of urine formation?

• After filtration, the process called reabsorption occurs. • Finally, a there is a process called secretion which completes the formation of urine.

54. How does constriction of the efferent arteriole affect filtration pressure?

• If an efferent arteriole constricts, the build-up of pressure in the afferent arteriole leads to increased filtration pressure in the glomerulus.

Loops of Henle

• Kidneys of babies have mostly cortical nephrons so urine produced by a baby is more dilute and not as concentrated. • Later on, after 2 years ad after the kidneys develop more juxtaglomerular nephrons, the urine of a young child becomes more concentrated.

57. What processes are involved in the process of reabsorption?

• Reabsorption processes include passive transport, active transport and co-transport. Reabsorption is the return of water and solutes filtered from blood at renal corpuscle to the blood.

38. Why are females more susceptible to urinary tract infections than males?

• The simplicity of a female urethra leads to some incontinent problems as well as a greater chance for infections but can be easily treated. • The complicated nature of a male urethra has more medical implications, especially involving the prostate gland. More aggressive treatment is needed.

Effective Filtration Pressure

• The variable in this situation is glomerular capillary pressure so even slight deviations in systolic blood pressure can have dramatic effects in the ability of the kidneys to work. • This is why a person going into shock is a medical emergency and medical personnel have to take measures to help the person or their kidneys may be damaged.

39. Define urethritis, cystitis, and pyelitis.

• Urethritis is the infection of the urethra usually by different bacterial forms. Cause pain. • Cystitis is infection of the urinary bladder, often e. coli is the causative agent. Cause pain. • Pyelitis is infection of a kidney, which is a very dangerous infection to have. Kidney loses its ability to filter.