L1 Endocrinal function of kidney (P2 Hard)

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Questions and Answers

What is the primary function of the macula densa in the juxta-glomerular apparatus?

To facilitate glomerular filtration by altering podocyte activity

To monitor sodium chloride concentration and flow rate (correct)

To regulate smooth muscle contraction in the afferent arteriole

To secrete renin into the afferent arteriole

Which modified cells are found in the wall of the afferent arteriole of the juxta-glomerular apparatus?

Macula densa cells

Endothelial cells

Granular cells (correct)

Podocytes

Which process is primarily influenced by the interaction between the macula densa and the afferent arteriole?

Prevention of tubular reabsorption

Regulation of glomerular filtration rate (correct)

Secretion of antidiuretic hormone

Increase in urine concentration

What is the consequence of increased NaCl transport detected by the macula densa?

Increase in adenosine release affecting afferent arteriole Signup and view all the answers

Which component of the juxta-glomerular apparatus has a role in vasoconstriction of the afferent arteriole?

Macula densa cells Signup and view all the answers

What role does the kidney play in gluconeogenesis during prolonged fasting?

Synthesizes glucose from amino acids Signup and view all the answers

Which hormone secreted by the kidney stimulates red blood cell production in response to hypoxia?

Erythropoietin Signup and view all the answers

What triggers the secretion of renin by the juxtaglomerular apparatus?

Decrease in blood pressure Signup and view all the answers

What type of substances do prostaglandins secreted by the kidney act as?

Vasodilators and vasoconstrictors Signup and view all the answers

Which of the following factors inhibits renin secretion?

Increased ABP due to elevated blood volume Signup and view all the answers

What is the function of the enzyme 1α-hydroxylase in the kidneys?

Converts 25-hydroxycholecalciferol to 1,25-dihydroxyvitamin D3 Signup and view all the answers

Which of the following best describes the regulation of acid-base balance by the kidneys?

Regulation of internal buffer systems Signup and view all the answers

In chronic renal diseases, what condition related to erythropoiesis may patients suffer from?

Anemia due to reduced erythropoietin secretion Signup and view all the answers

What is the primary functional unit of the kidney?

Nephron Signup and view all the answers

Which type of nephron is primarily responsible for the concentration of urine?

Juxtamedullary nephron Signup and view all the answers

What is the role of the juxtaglomerular apparatus?

Regulation of blood pressure Signup and view all the answers

Which part of the nephron is primarily involved in the reabsorption of water and electrolytes?

Proximal convoluted tubule Signup and view all the answers

What type of cells are found in the collecting tubules affected by vasopressin?

Principal cells Signup and view all the answers

How many nephrons does each kidney contain approximately?

1 million Signup and view all the answers

What structure is formed by a tuft of capillaries surrounded by Bowman's capsule?

Renal corpuscle Signup and view all the answers

Which part of the nephron does not contain a brush border?

Loop of Henle Signup and view all the answers

The renal pelvis connects the kidney to which structure?

Ureter Signup and view all the answers

Which type of nephron is more abundant within the human kidney?

Cortical nephron Signup and view all the answers

What is NOT a function of the kidney?

Filtration of pathogens Signup and view all the answers

What defines the ascending limb of the Loop of Henle?

It has both thin and thick segments. Signup and view all the answers

What stimulates the secretion of renal hormones?

Decrease in blood volume Signup and view all the answers

Study Notes

Renal Module Information

Course code: IMP-07- 20318
Phase: I
Year/semester: 2nd year / Semester 3
Academic year: 2022-2023

Lecture 1: Endocrine Function of the Kidney

Intended Learning Outcomes (ILOs):
- Describe functions of the renal system.
- Identify types of nephrons and their functions.
- Describe the juxtaglomerular apparatus and its significance.

Structure of the Urinary System

The urinary system includes the kidney, renal artery, renal vein, ureter, urinary bladder, and urethra.

Kidney Structure

Composed of 6-18 lobes.
Each lobe consists of a pyramid of medulla covered by cortex.
Renal cortex: Outer layer.
Renal medulla: Inner layer, contains pyramids.
Renal pelvis: Funnel-shaped structure that collects urine from the pyramids.
Ureter: Carries urine from the kidney to the bladder.
Nephron: Functional unit of the kidney (one million nephrons per kidney).

Nephron Structure

Renal corpuscle:
- Glomerulus: Ball of capillaries between afferent and efferent arterioles.
- Bowman's capsule: Expanded blind end of tubules surrounding the glomerulus.
Renal tubules:
- Proximal convoluted tubule (PCT): Highly coiled, in the cortex, one cuboidal cell layer, luminal brush border.
- Loop of Henle: U-shaped, thin descending and thick ascending, in the medulla.
- Distal convoluted tubule (DCT): Highly coiled, in the cortex, one cuboidal cell layer.
Collecting tubules (CT): Cross the entire medulla; multiple DCTs empty into each CT, principle cells affected by vasopressin, I cells secrete acids.

Juxtaglomerular Apparatus

Site: DCT contacts afferent arteriole.
Components:
- Macula densa: Modified cells in the DCT that monitor fluid flow rate (NaCl transport).
- Granular cells: Modified cells in the afferent arteriole wall that monitor flow and secrete renin.

Functions of the Kidney

1. Homeostasis of ECF: Regulates water and electrolyte balance, pH, and osmolarity of extracellular fluid (ECF).
2. Excretion of metabolic wastes: Eliminates urea, uric acid, creatinine, and foreign compounds (e.g., drugs).
3. Gluconeogenesis: Synthesizes glucose from amino acids during prolonged fasting.
4. Regulation of arterial blood pressure: Secretions of renin are important
5. Endocrine functions:
- Secretes erythropoietin: Stimulates red blood cell production.
- Secretes renin: Plays role in salt conservation & controlling blood pressure.
- Converts vitamin D into active form.(1,25-dihydroxyvitamin D3).
- Secretes prostaglandins (PGE2 & PGI2): Regulate glomerular filtration rate and renal blood flow..
6. Regulation of acid-base balance: Eliminates acids generated from protein metabolism; regulates the body's buffer stores.

Renin-Angiotensin-Aldosterone System (RAAS)

Renin: Hormone secreted by the juxtaglomerular apparatus, triggered by factors like low blood pressure.
Converts angiotensinogen to angiotensin I; ACE converts angiotensin I to angiotensin II.

Factors Stimulating Renin Secretion

Renal ischemia (reduced blood supply).
Hypotension and hemorrhage.
Sympathetic stimulation.
Increased blood catecholamine levels.

Factors Inhibiting Renin Secretion

Increased blood pressure.
Increased NaCl or Na reabsorption in the macula densa.
Angiotensin II.
Vasopressin (ADH) and aldosterone.

Erythropoietin

Hormone secreted by peritubular capillaries in response to hypoxia.
Stimulates red blood cell production in bone marrow.
Crucial role in erythropoiesis (red blood cell production).
85% of erythropoietin in the body synthesized by kidneys; deficiency can lead to anemia in renal diseases.

References for Medical Physiology

Ganong, William F. Review of Medical Physiology, 23rd edition. McGraw-Hill, 2011, pp. 640-642.
Guyton, Arthur C., and John E. Hall. Textbook of Medical Physiology, 12th edition. Saunders Elsevier, 2011, pp. 303-306.
Handbook of the Physiology Department, Faculty of Medicine for Girls, Al-Azhar University, p.1:11.

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Description

Test your knowledge on the endocrine function of the kidney, including the structure of the renal system and nephron types. Understand the roles of the juxtaglomerular apparatus and its significance. This quiz is designed for 2nd-year medical students in the Renal Module.