Physiology of Liver and Renal Function in Drug Elimination

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Questions and Answers

What percentage of the liver's blood supply is derived from the hepatic artery?

15%

50%

75%

25% (correct)

Which of the following best describes the composition of a portal triad?

Portal vein, hepatic vein, and lymphatic vessel

Hepatic sinusoid, central vein, and bile duct

Hepatic artery, hepatic vein, and bile duct

Portal vein, hepatic artery, and bile duct (correct)

Which cells lining the liver sinusoids are phagocytic macrophages?

Endothelial cells

Hepatocytes

Kupffer cells (correct)

Canalicular cells

Into which structure does blood from the central veins ultimately drain?

Inferior Vena Cava (D) Signup and view all the answers

What is the primary function of the liver canaliculi with respect to drug elimination?

Pumping drugs into bile (B) Signup and view all the answers

Which of the following is NOT a typical function of the liver?

Production of red blood cells outside of specific disease states (A) Signup and view all the answers

The liver functions as a digestive organ, endocrine organ, a hematologic organ and:

An excretory organ (C) Signup and view all the answers

What type of blood flows through the portal vein?

Oxygen-depleted blood from the digestive tract (A) Signup and view all the answers

Which of the following is NOT a primary function of the liver as an excretory organ?

Production of erythropoietin (C) Signup and view all the answers

Approximately what percentage of cardiac output is delivered to the kidneys?

25% (B) Signup and view all the answers

The renal pyramids are located in which region of the kidney?

Medulla (B) Signup and view all the answers

Which division of the autonomic nervous system innervates the kidneys?

Sympathetic (D) Signup and view all the answers

The peritubular capillaries directly wrap around the:

Proximal and distal convoluted tubules (D) Signup and view all the answers

Which of these structures filters fluid from blood into Bowman's capsule?

Glomerulus (D) Signup and view all the answers

What is the external landmark used to locate the kidneys?

Costovertebral Angle (C) Signup and view all the answers

The activation of which vitamin is a function of the kidney?

Vitamin D (B) Signup and view all the answers

Which segment of the nephron is primarily responsible for creating a hypo-osmotic filtrate?

Ascending loop of Henle (C) Signup and view all the answers

What is the primary effect of Antidiuretic Hormone (ADH) on the collecting tubule?

Passive transport of water (D) Signup and view all the answers

Which component of the glomerular filtration rate (GFR) equation represents oncotic pressure in the Bowman's capsule?

π<del>BC</del> (B) Signup and view all the answers

What is the role of macula densa cells in regulating GFR?

They sense changes in sodium concentration. (A) Signup and view all the answers

In the reabsorption of glucose, what protein facilitates glucose movement out of the tubular cell into the interstitial space?

GLUT2 (D) Signup and view all the answers

Which of the following is NOT directly transported across the renal epithelium during acid-base balance regulation?

HCO$_3^-$ (A) Signup and view all the answers

Which of the following is a primary function of the proximal convoluted tubule?

Reabsorption of two-thirds of filtered water and electrolytes (C) Signup and view all the answers

What condition can lead to excessive GFR and hyperfiltration?

High serum glucose (D) Signup and view all the answers

Which of the following is the primary mechanism by which ADH increases water reabsorption in the kidneys?

Translocating aquaporin 2 channels to the apical membrane (B) Signup and view all the answers

What is the main physiological effect of Atrial Natriuretic Peptide (ANP) on sodium and water reabsorption in the kidneys?

It decreases sodium and water reabsorption. (B) Signup and view all the answers

Which of the following locations is primarily responsible for potassium excretion in the kidneys?

Distal tubule and collecting duct (B) Signup and view all the answers

A patient's urinalysis reveals the presence of WBC casts. Which of the following conditions is most strongly suggested by this finding?

Pyelonephritis (D) Signup and view all the answers

Which transporter is directly involved in moving K^+^ into tubule cells?

Na^+^-K^+^ pump (B) Signup and view all the answers

What is the effect of aldosterone on potassium excretion in the kidneys?

It increases potassium excretion. (B) Signup and view all the answers

What are the key hormones involved in the reabsorption of sodium and water?

Aldosterone and Angiotensin II (AII) (A) Signup and view all the answers

What is the approximate rate of decline in GFR after age 40?

10% decrease per decade (B) Signup and view all the answers

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Study Notes

Drug elimination involves metabolism (biotransformation) and excretion.
Liver and kidneys are major drug-eliminating organs.
Hydrophilic drugs are readily excreted by the kidneys.
Lipophilic drugs are transformed by the liver into more water-soluble metabolites for excretion by the kidneys or bile.

Overview of Liver Structure and Function

Liver is vital for fat digestion, carbohydrate storage, blood detoxification, and protein production.
Dual blood supply: 25% from hepatic artery, the remainder from portal vein (oxygen-poor, rich in absorbed substances from the gut).
Portal triads (portal veins, hepatic arteries, and bile ducts) associate with afferent blood vessels.
Blood from hepatic artery and portal vein combine in hepatic sinusoids, then drains into central veins, which merge into the hepatic vein.
Hepatic cells lining bile canaliculi produce bile.
Liver has a complex lymphatic drainage system.

Summary of Normal Liver Function

The liver functions as a digestive, endocrine, hematologic, and excretory organ.
Digestive: Bile salt secretion for fat digestion; Processing and storage of absorbed fats, carbohydrates, proteins; Processing and storage of vitamins and minerals.
Endocrine: Metabolism of glucocorticoids, mineralocorticoids, and sex hormones; Regulation of carbohydrate, fat, and protein metabolism.
Hematologic: Temporary storage of blood; Removal of bilirubin; Hematopoiesis (in some diseases); Synthesis of blood clotting factors.
Excretory: Excretion of bile pigment, cholesterol; Synthesis of urea; Detoxification of drugs and foreign substances.

Drug Elimination and Biotransformation Reactions

Liver drug metabolism is flow and site-dependent: varies in enzyme quantity, blood flow, and diseases.
Enzymes like mixed-function oxidases (e.g., CYP enzymes) and non-CYP enzymes are involved in drug oxidation and reduction.
Conversion into more polar metabolites increases elimination speed.
Lipid-soluble drugs are reabsorbed; polar metabolites are not readily reabsorbed and excreted.
Some metabolites are pharmacologically active or toxic. Prodrugs require biotransformation.

First-Pass Effects and Biliary Clearance

First-pass effect: Oral drugs are metabolized in the liver or intestines before reaching systemic circulation, reducing bioavailability.
Enterohepatic circulation: Drugs excreted in bile may be reabsorbed by intestines and returned to the liver.
Many drugs excreted in bile are metabolites (often glucuronide conjugates).
Biliary clearance (CLbiliary) measures drug removal by biliary secretion.
Drug excretion in bile can be clinically significant, as it affects absorption, recycling.

Kidney Physiology

Kidneys are located just below the diaphragm.
Each kidney has a hilum (point where blood vessels, lymphatic vessels, nerves enter/exit).
Blood supply is significant, approximately 25% cardiac output.
Renal blood supply - the majority goes through the cortex, a smaller amount goes through the medulla.
Nephrons: Functional units of the kidneys, essential for glomerular filtration, reabsorption, and secretion.
Glomerulus: Filters fluid from blood into Bowman's capsule; prevents blood cells and protein passage.
Proximal convoluted tubule: Transports filtered water, electrolytes, bicarbonate, glucose, amino acids, and vitamins to interstitial fluid.
Descending Loop of Henle: Transports water, concentrates the filtrate
Ascending loop of Henle. Actively transports Na+, K+, and Cl-, creating a hypo-osmotic filtrate.
Distal convoluted tubule: Transports Na+, Cl-, water, and urea; responsive to aldosterone, site for macula densa regulation of GFR.
Collecting tubule: Passive transport of water under ADH influence. Secretes H+ and K+.
Glomerular filtration rate (GFR): Rate of filtration. Normal GFR is 125 ml/minute. Factors affect filtration pressure (blood volume, pathological states).

Regulation of Blood Volume and Osmolality

Hormones regulate these through tubular reabsorption.
ADH (antidiuretic hormone): Increases water reabsorption.
Aldosterone: Increases sodium and water reabsorption
ANP (atrial natriuretic peptide) and Urodilatin: Decrease reabsorption..

Renal Function Tests & Diagnostic Tests

Urinalysis of serum creatinine and blood urea nitrogen (BUN).
Glomerular filtration rate (GFR) measurements, assessing renal function. Using creatinine clearance.
Imaging, blood tests, and biopsy.

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Description

This quiz covers the pre-class readings on liver and renal physiology related to drug elimination. It highlights the processes of metabolism and excretion, focusing on the roles these organs play in handling hydrophilic and lipophilic drugs. Understanding these mechanisms is essential for studying pharmacology and drug therapies.