Renal Physiology: Kidney Function

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Questions and Answers

Which part of the nephron is primarily responsible for the filtration process?

Collecting duct

Proximal convoluted tubule

Glomerulus (correct)

Loop of Henle

What is the main functional difference between cortical and juxtamedullary nephrons?

Cortical nephrons have longer loops of Henle

Cortical nephrons are primarily situated in the renal medulla

Juxtamedullary nephrons extend deeper into the renal pyramids (correct)

Juxtamedullary nephrons are less effective in urine concentration

Which segment of the renal tubule follows the Loop of Henle?

Distal convoluted tubule (correct)

Proximal convoluted tubule

Thick descending limb

Collecting duct

Which component of the nephron is primarily responsible for reabsorbing water and ions?

Loop of Henle Signup and view all the answers

What are the main anatomical components that make up the renal corpuscle?

Glomerulus and Bowman’s capsule Signup and view all the answers

What is the primary function of erythropoietin secreted by the kidneys?

Stimulate erythrocyte production Signup and view all the answers

Which structure is NOT a part of the nephron?

Renal pelvis Signup and view all the answers

What triggers the release of renin from the juxtaglomerular cells of the kidneys?

Decreased blood pressure Signup and view all the answers

The renal cortex is primarily involved in which of the following functions?

Filtration of blood Signup and view all the answers

Which of the following best describes the role of kidneys in maintaining internal homeostasis?

Balancing water and inorganic ions Signup and view all the answers

What initiates the micturition reflex in the bladder?

Stretching of the bladder walls Signup and view all the answers

At what bladder volume does the pressure rise above the threshold level to trigger micturition?

400-500 ml Signup and view all the answers

What is the role of the internal sphincter during the micturition reflex?

It opens to allow urine flow Signup and view all the answers

Which of the following correctly describes a consequence of abnormal urine volume?

Dehydration and electrolyte imbalance Signup and view all the answers

What is the primary function of smooth muscle contractions in the ureters?

To propel urine towards the bladder Signup and view all the answers

What is the primary function of juxtamedullary nephrons?

Concentrate and dilute urine Signup and view all the answers

Which structure is NOT part of the juxtaglomerular apparatus?

Efferent arterioles Signup and view all the answers

How does the loop of Henle of juxtamedullary nephrons differ from that of cortical nephrons?

It is longer and extends into the inner cortex Signup and view all the answers

What is the location of cortical nephrons within the kidney?

Outer part of the cortex Signup and view all the answers

Which statement about the glomerulus in juxtamedullary nephrons is correct?

It is larger than the glomerulus in cortical nephrons Signup and view all the answers

Which type of nephron contains a rich sympathetic nerve innervation?

Cortical nephron Signup and view all the answers

What is the ratio of cortical to juxtamedullary nephrons in the human kidney?

90% cortical to 10% juxtamedullary Signup and view all the answers

What is the primary role of the macula densa in the juxtaglomerular apparatus?

Sense changes in volume and NaCl concentration Signup and view all the answers

Study Notes

Kidney Function

Regulates water and inorganic ion balance in the body.
Excretes metabolic waste products and foreign chemicals through urine for internal homeostasis.
Secretes hormones like:
- Erythropoietin: Controls erythrocyte production.
- Renin: Produced by juxtaglomerular cells, regulates formation of angiotensin.
- 1,25-dihydroxyvitamin D3: Influences calcium balance.

Anatomical Characteristics of the Kidney

Composed of renal cortex, renal medulla, and renal pelvis.
Functional unit is the nephron, with about 1 million nephrons per kidney.
Each nephron consists of:
- Renal Corpuscle:
  - Glomerulus: Tuft of capillaries.
  - Bowman’s Capsule: Surrounds glomerulus.
- Renal Tubule:
  - Proximal Convoluted Tubule
  - Loop of Henle: Thick and thin limbs.
  - Distal Convoluted Tubule.

Types of Nephrons

Cortical Nephrons:
- ~85% of all nephrons.
- Located in the outer cortex.
- Short loops of Henle.
- Rich sympathetic innervation.
- Function primarily in reabsorption and secretion.
Juxtamedullary Nephrons:
- ~15% of all nephrons.
- Located closer to renal medulla, with long loops of Henle extending deeply.
- Forms vasa recta for blood supply.
- Function in concentrating and diluting urine.

Juxtaglomerular Apparatus (JGA)

Composed of macula densa, mesangial cells, and juxtaglomerular cells.
Macula Densa: Senses changes in NaCl concentration and volume of tubular fluid; informs glomerulus.
Juxtaglomerular Cells: Secrete renin to regulate blood pressure.
Functions in Tubulo-glomerular Feedback to regulate glomerular filtration rate.

Renal Circulation

Blood flow is approximately 1200 ml/min, making up 20-25% of cardiac output.
Blood distribution:
- Cortex: 94%
- Outer medulla: 5-6%
- Inner medulla: minor.

Micturition (Urination)

Urine flows through the ureters to the bladder due to smooth muscle contractions in the ureter walls.
The bladder stores urine and facilitates intermittent ejection during urination.
Micturition involves:
- Filling the bladder until pressure exceeds 400-500 ml.
- Activation of the micturition reflex to empty the bladder.

Micturition Reflex

Bladder capacity ranges from 250 to 400 ml.
Increased volume stretches the bladder walls, initiating the reflex:
- Parasympathetic stimulation causes bladder contraction.
- Internal sphincter opens, and external sphincter relaxes, leading to urination.

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Description

This quiz focuses on the various functions of the kidneys, including the regulation of water and ion balance, excretion of metabolic waste, and hormone secretion. Test your understanding of these critical renal processes that maintain homeostasis in the body.