Worksheet 10 - Renal system and acid base balance 2 PDF

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Renal system

and Acid base balance

Pre-workshop Activities (To be completed before you come to the workshop)

Learning objectives (renal system) On completion of this topic, you should be able to: 1. Describe the major roles and functions of the components of the urinary system: kidneys, ureters, bladder & urethra 2. Describe the structure of the nephron and the associated blood vessels, and the location of different nephron segments within the cortex and medulla of the kidney 3. Describe the process involved in the formation of urine (glomerular filtration, tubular reabsorption and tubular secretion) and describe the composition of the filtration membrane between the blood and the interior of the glomerular capsule 4. Describe the process of micturition and its neural control 5. Describe the feedback mechanisms that regulate water intake and hormonal controls of water output in urine (ADH) 6. Describe the effects of afferent and/or efferent-arteriolar constriction on glomerular capillary pressure, net filtration pressure and glomerular filtration rate 7. Explain how the kidneys contribute to the long term regulation of extracellular volume and blood pressure, including the roles of renal sympathetic nerves and the reninangiotensin-aldosterone system

Learning objectives (acid base balance) 1. Define the terms acid, base, pH, acidosis and alkalosis 2. Describe the 3 ways in which plasma pH is regulated: chemical buffer systems, the lungs (respiratory system) and the kidneys (changes in excretion of acid) 3. Describe the causes and consequences of acid-base abnormalities (respiratory and renal acidosis/alkalosis)

Objective 1: Describe the major roles of the components of the urinary system: kidneys, ureters, bladder & urethra •

View the presentation: Urinary system - functions

•

Suggested reading from Tortora & Derrickson Chapter 26: ‘overview of kidney functions’ and ‘Anatomy and Histology of the Kidneys’

1. Complete the following table. Organ Major function(s) Kidneys

Bean shaped organs that produce the urine. They are the most functional organ of the renal system, filtering nearly 200L of fluid from our blood stream every day in order to maintain the electrolyte and fluid balance in our internal body environment.

Ureter

2 tubes called ureters and they transport the urine to the bladder

Bladder

Is a temporary storage sac for the urine

Urethra

Is the tube that is responsible for transporting urine outside of the body

2. Label the following diagram of the female anatomy: include bladder, urethra, ureters, and urethra.

3. Label the diagram showing the basic gross anatomy of the kidney. Include the cortex, medulla, pelvis and ureter.

4. Where are the nephrons located in the kidney? The medulla collectively houses the nephrons 5. List and describe the functions of the kidneys: -

Maintain balance between water, salts and acids

-

Produce hormones renin and erythropoietin

-

Regulate volume and chemical composition of blood

-

Gluconeogenesis during prolonged fasting

-

Activation of vitamin D

-

Filter fluid from bloodstream to remove toxins, waste and excess ions

6. How is urine transported from the ureters to the bladder? What is this process called?

As the kidneys produce the urine, the ureters distend, or swell, which stimulates the smooth muscle layer, which is known as the muscularis, to contract which propels the urine into the bladder. This process is called peristalsis, and the strength and frequency of the peristaltic waves is adjusted to the rate of urine formation. 7. Label the following diagram of (a) the male and (b) the female bladder and urethra. Identify the ureters, detrusor muscle, internal urethral sphincter, prostate, urogenital diaphragm, external urethral sphincter and urethra.

8. Urination/micturition is initiated by contraction of which muscle? The contraction of the detrusor muscle squeezes on the urine in the bladder to produce urination (micturition). 9. The internal urethral sphincter is under involuntarily control 10. The external urethral sphincter is under voluntarily control

Objective 2: Describe the structure of the nephron and the associated blood vessels, and the location of different nephron segments within the cortex and medulla of the kidney

•

View the presentation: Renal - nephrons

•

Suggested reading from Tortora & Derrickson Chapter 26: ‘Anatomy and Histology of the Kidneys – the nephron’

11. On the following diagram label the glomerulus, glomerular capsule, Proximal convoluted tubule (PCT), loop of Henle, Distal convoluted tubule (DCT) and collecting duct

12. Complete the following table. Structure Function(s) Glomerulus

Ball of capillaries, very porous in that they let large amounts of solute-rich fluid to pass from the blood into the glomerular capsule.

Glomerular capsule

Cup shaped at the end of the renal tubule; it completely surrounds the glomerulus.

Proximal convoluted tubule (PCT)

Is adapted for absorption, this is where most of the filtrate is reabsorbed back into the blood stream.

Loop of Henle

Used to concentrate and dilute the filtrate.

Distal convoluted tubule (DCT)

Latter part of the nephron tubule

Collecting duct

structures that receive the urine from many nephrons where they then deliver it to the pelvis

13. The renal corpuscle consists of two parts: glomerulus and glomerular capsule.

14. The PCT is adapted for absorption.

15. Once reabsorbed, where are the substances returned to? Into the bloodstream 16. What is the role of microvilli in the tubule segments of the nephron? Increase the surface area for absorption, reabsorbing water and solutes from the filtrate.

17. The functional units of the kidney are the ________________________. They are called ____________________ ____________________ if they are located mainly in the cortex. They are called __________________________ ___________________ if they are located in both the cortex and medulla.

18. The afferent arterioles feed into the

19. The efferent arterioles feed into the ________________________________ capillaries 20. After crossing the filtration membrane, the filtrate flows, in sequence, through what structures before reaching the bladder. (list the structures in order: Glomerular capsular space, ureter, proximal tubule, loop of Henle, distal tubule, collecting duct, renal pelvis)

Together, the glomerulus and the glomerular capsule make the renal corpuscle. The renal tubule has three major parts, the PCT, loop of henle and the DCT. The proximal convoluted tubule is adapted for absorption – this is where most of the filtrate is reabsorbed back into the blood stream. The loop of henle is used to concentrate and dilute the filtrate. The distal convoluted tubule is the latter part of the nephron tubule. Collecting ducts are the structures that receive the urine from many nephrons where they then deliver it to the pelvis

Objective 3: Describe the process involved in the formation of urine (glomerular filtration, tubular reabsorption and tubular secretion) and describe the composition of the filtration membrane between the blood and the interior of the glomerular capsule

•

View the presentation: Urinary system – formation of urine

•

Suggested reading from Tortora & Derrickson Chapter 26: ‘Overview of Renal Physiology’, ‘glomerular filtration’ and ‘Tubular Reabsorption and Tubular Secretion’

21. What is the difference between ‘filtrate’ and ‘urine’ -

Filtrate: what enters the glomeruli (starting product), everything found in blood plasma except for proteins and blood cells. Urine: leaves the body (the waste product), metabolic wastes and unwanted substances.

22. List and describe the 3 processes performed by nephrons to produce urine Occurs at the renal corpuscle. Passive process where Glomerular filtration hydrostatic pressure forces fluids and solutes through a membrane. Tubular reabsorption

Selective process, occurs in the PCT, loop of Henle and the DCT, waste products and excess solutes are not absorbed, from the urine.

Tubular secretion

Substances selectively secreted back into the tubule, fine tuning occurs to keep the body’s chemicals in balance, occurs in the PCT and DCT, active process.

23. Glomerular filtration is a passive process. What does this mean? No energy required, non-selective process in which fluids and solutes are forced through a membrane by hydrostatic pressure. 24. What force is responsible for formation of the filtrate during glomerular filtration?

Hydrostatic pressure exerted as blood flows through the capillaries. It favours filtration as the efferent arteriole has a smaller diameter than the afferent arteriole that feeds into the glomerular space. 25. Large molecules such as plasma proteins and blood cells are excluded from the filtrate. Why? And where do these molecules remain? Large molecules, such as red blood cells and plasma proteins cannot enter as they are too large. Remain in the blood.

26. Small molecules such as glucose, nitrogenous wastes, amino acids and water are included in the filtrate. Where (in the nephron) do these molecules go next? The filtrate includes small molecules that pass freely from the blood into the glomerular filtrate as a result of the pressure difference. 27. Label the structures of the filtration membrane: fenestrations, slit membrane, glomerular endothelial cell, podocyte

28. This filtration membrane permits large or small (circle correct answer) molecules to be filtered. 29. Glomerular filtration depends on 3 main pressures, in the table below describe them and state whether the promote of oppose filtration Description Promote or Oppose filtration Glomerular blood hydrostatic pressure

Glomerular capillary hydrostatic blood pressure, favouring filtration

Promote

Capsular hydrostatic pressure

Fluid in the glomerular capsule exerts a hydrostatic pressure.

Opposing

Blood colloid osmotic pressure

Colloid osmotic force due to the presence of protein in glomerular

Opposing

30. What would happen to the net filtration pressure if the capsular hydrostatic pressure increased? (circle correct response) Increase

/

decrease

31. The cells of the proximal convoluted tubule are the main site of reabsorption. List some of the substances that are reabsorbed in the PCT: Glucose and amino acids along with most other nutrients and ions (including sodium and potassium). Water is also reabsorbed by osmosis, which occurs because it follows the solutes that are reabsorbed. 32. Reabsorption in the PCT is under hormonal control true / false (circle correct answer)

33. The simple squamous cells of the thin descending loop are permeable to water but impermeable to solutes.

34. The ascending limb of the loop of Henle is permeable to ions but impermeable to water.

35. The cells of the DCT undertake the fine tuning of the electrolyte reabsorption.

36. The hormone ADH controls water reabsorption 37. The hormone aldosterone controls the fine tuning of Na+ and K+ reabsorption.

38. Sodium reabsorption in the PCT is the driving force for the reabsorption of most other solutes. Why? Sodium reabsorption provides the energy and the means for reabsorbing most other solutes. The reabsorption of sodium creates an osmotic gradient across the tubule which drives water reabsorption, largely through water channels called aquaporins. 39. List the reasons why some substances are not reabsorbed -

Lack carriers or channels

-

Are not lipid soluble

-

Are too large to pass through the membrane pores

40. The final step in the formation of urine is tubular secretion. This is where substances are selectively moved back into the tubule to become part of the filtrate. 41. Where in the nephron does tubular secretion occur? PCT and DCT 42. List some reasons why tubular secretion is an important process? -

Disposing of substances (such as drugs) which are bound to plasma proteins.

-

Eliminating undesirable substances or end products that have been reabsorbed by passive processes (urea and uric acid).

-

Riding the body of excess potassium ions.

-

Controlling blood ph.

Objective 4: Describe the process of micturition and its neural control

•

View the presentation: urinary system - micturition

•

Suggested reading from Tortora & Derrickson Chapter 26: Urine Transportation, Storage and Elimination – The Micturition Reflex’

43. What structure(s) carry the urine from the kidneys to the bladder? Kidneys via the ureters to the bladder 44. What structure is the storage organ for urine? Bladder

45. What structure carries the urine from the bladder to the outside of the body? Released via the urethra

46. The internal urethral sphincter is composed of smooth muscle and is under involuntary control. 47. The external urethral sphincter is composed of skeletal muscle and is under voluntary control.

48. Where is the detrusor muscle found? Bladder 49. What is the trigger for the initiation of micturition? Stretching of the bladder wall initiates urination, micturition is the voiding or expelling of urine from the bladder.

50. For micturition to occur, what 3 things must happen? -

Contraction of the detrusor muscle The internal urethral sphincter must open involuntary The external urethral sphincter must open voluntary

51. Fill in the table to summarise the events of micturition Structure Muscle Innervation Nervous system activity for type micturition (increased or decreased) Detrusor muscle

Internal urethral sphincter

External urethral sphincter

Smooth muscle

Smooth muscle

Parasympathetic neurons

Causes detrusor muscle contraction

Parasympathetic neurons

Cause internal urethral sphincter opening

Sympathetic neurons

Helps it open, can choose to close

Skeletal muscle

Objective 5: Describe the feedback mechanisms that regulate water intake and hormonal controls of water output in urine (ADH)

•

View the presentation: ADH

•

Suggested reading from Tortora & Derrickson Chapter 26: ‘Tubular Reabsorption and Tubular secretion – Anti Diuretic Hormone’

52. List the 2 compartment that fluid occupies in the body Intracellular fluid (ICF), Extracellular fluid (ECF) 53. Water intake is crudely regulated by what mechanism? ADH hormone

54. What are the three major stimuli for initiation of the thirst mechanism? -

Osmolarity, decrease in saliva, decrease in blood volume

55. What is the major stimulus for ADH secretion?

56. What are the detectors of osmolarity called? _____________________________________

57. Where are these detectors located? ___________________________________________

58. Where is ADH released from? ________________________________________________

59. High levels of ADH secretion will increase / decrease (circle correct answer) water reabsorption, causing urine output to increase / decrease (circle correct answer).

60. Under the following conditions, report the levels of ADH and subsequent urine volume: Hydration ADH Urine volume Urine concentration (high / low)

(small / large)

(concentrated / dilute)

Dehydration

High

Large

Concentrated

Over hydration

Low

Small

Dilute

Objective 6: Describe the effects of afferent and/or efferentarteriolar constriction on glomerular capillary pressure, net filtration pressure and glomerular filtration rate

•

View the presentation: Afferent/efferent

•

Suggested reading from Tortora & Derrickson Chapter 26: ‘Glomerular filtration’

61. Fill in the following table Glomerular

Glomerular filtration

hydrostatic pressure

rate

(increase or decrease) (increase or decrease)

afferent arteriole vaso-constricts and efferent arteriole unchanged

Decrease

Decrease

afferent arteriole vasodilates and efferent arteriole unchanged

Increase

Increase

efferent arteriole vaso-constricts and afferent arteriole unchanged

Increase

Decrease

efferent arteriole vasodilates and afferent arteriole unchanged

Decrease

Decrease

62. Sympathetic stimulation constricts the afferent arterioles which causes an increase / decrease (circle correct answer) in blood flow to the nephron.

Objective 7: Explain how the kidneys contribute to the long term regulation of extracellular volume and blood pressure, including the roles of renal sympathetic nerves and the reninangiotensinaldosterone system • •

View the presentation: blood volume and blood pressure Suggested reading from Tortora & Derrickson Chapter 26: Tubular Reabsorption and Tubular Secretion – Renin-Angiotensin-Aldosterone System’ and Chapter 18: ‘Adrenal Glands mineralocorticoids’

63. Short term regulation of blood pressure is achieved by the sympathetic nervous system. Describe the process following a decrease in blood pressure: Short term is achieved through hormonal, via changes to peripheral resistance. 64. Long term regulation is achieved by the release of the enzyme renin by the juxtaglomerular cells of the nephron. Describe the process following a decrease in blood pressure: Long term is achieved through renin; angiotensin; aldosterone mechanism, indirectly by altering blood volume 65. The reabsorption of sodium back into the peritubular capillaries causes the subsequent reabsorption of water in an effort to even out the osmotic gradient.

66. Granular cells monitor _within the arterioles. 67. The macula densa cells monitor ______________________________________________

68. The juxtaglomerular apparatus of the nephron secretes ______________ in response to a decrease in __________________ pressure.

69. Renin converts the plasma protein angiotensinogen into angiotensin I

70. Angiotensin II is a potent vasoconstrictor of arterioles.

71. The hormone aldosterone regulates water reabsorption in the kidneys through its activity on the reabsorption of sodium ions and secretion of __________________ ions.

Objective 1. Define the terms acid, base, pH, acidosis and alkalosis •

View the presentation: Acid Base

•

Suggested reading from Tortora & Derrickson Chapter 2: ‘Inorganic compounds and Solutions’

1. The acidity or alkalinity of a solution is in units of pH, what is this a measure of in solution? The concentration of hydrogen ions is measured in pH units. 2. Fill in the table pH (high or low)

H+ concentration (high or low)

OH- concentration (high ...