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Questions and Answers
What is the primary function of kidneys in the excretion process?
What is the primary function of kidneys in the excretion process?
How do kidneys contribute to maintaining water balance in the body?
How do kidneys contribute to maintaining water balance in the body?
Which of the following waste products is NOT excreted by the kidneys?
Which of the following waste products is NOT excreted by the kidneys?
What hormone do kidneys secrete to stimulate erythrocyte production?
What hormone do kidneys secrete to stimulate erythrocyte production?
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In response to a decrease in plasma sodium concentration, how do kidneys adjust their function?
In response to a decrease in plasma sodium concentration, how do kidneys adjust their function?
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Which hormone is primarily responsible for stimulating the production of thrombocytes?
Which hormone is primarily responsible for stimulating the production of thrombocytes?
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What is the primary structural and functional unit of the kidney?
What is the primary structural and functional unit of the kidney?
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Which component of the nephron is responsible for the filtration of blood?
Which component of the nephron is responsible for the filtration of blood?
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How do the kidneys help regulate blood pressure in the long term?
How do the kidneys help regulate blood pressure in the long term?
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Which layer of the kidney contains the renal columns?
Which layer of the kidney contains the renal columns?
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What is the primary function of the Bowman capsule?
What is the primary function of the Bowman capsule?
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Which statement accurately describes the composition of the glomerular capillaries?
Which statement accurately describes the composition of the glomerular capillaries?
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What is the estimated normal Glomerular Filtration Rate (GFR) in an adult human?
What is the estimated normal Glomerular Filtration Rate (GFR) in an adult human?
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Which of the following substances is NOT filtered through the glomerular capillaries?
Which of the following substances is NOT filtered through the glomerular capillaries?
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What maintains glomerular filtration pressure?
What maintains glomerular filtration pressure?
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Flashcards
Excretion
Excretion
The elimination of unwanted substances and waste products from the body. Examples include removal of toxins, excess water, and metabolic byproducts.
Kidneys
Kidneys
The organs responsible for filtering waste products from the blood and producing urine.
Urea
Urea
A waste product formed from the breakdown of amino acids. It is filtered by the kidneys and excreted in urine.
Homeostasis
Homeostasis
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Hematopoietic function of the kidney
Hematopoietic function of the kidney
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What is a glomerulus?
What is a glomerulus?
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What is Bowman's capsule?
What is Bowman's capsule?
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What is erythropoietin?
What is erythropoietin?
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What is the proximal convoluted tubule?
What is the proximal convoluted tubule?
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What is renin?
What is renin?
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Afferent & Efferent Arterioles in Bowman's Capsule
Afferent & Efferent Arterioles in Bowman's Capsule
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Bowman's Capsule Structure
Bowman's Capsule Structure
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Podocytes
Podocytes
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Glomerular Filtration Membrane
Glomerular Filtration Membrane
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Glomerular Filtrate
Glomerular Filtrate
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Study Notes
Renal System
- The renal system is responsible for eliminating unwanted substances and metabolic waste from the body.
- Other organs involved in excretion include the liver, lungs, skin, and gastrointestinal tract (GIT).
- The renal system has a high excretory capacity. It eliminates water, salts, and wastes, and removes heat from the body.
- The renal system consists of kidneys, renal arteries, renal veins, ureters, urinary bladder, and urethra.
Introduction
- Excretion is the process of eliminating unwanted substances and metabolic wastes from the body.
- The liver excretes bile pigments, heavy metals, drugs, toxins, bacteria, etc., through bile.
- The GIT excretes food residues in the form of feces.
- The lungs remove carbon dioxide and water vapor.
- The skin excretes water, salts, and some wastes; removes heat from the body.
Renal System - Anatomy
- The kidney is a tubular gland formed of 3 layers: outer cortex, inner medulla, and renal sinus.
- The inner medulla contains medullary or Malpighian pyramids.
- The renal sinus comprises the upper expanded portion of the ureter (renal pelvis), subdivisions of the pelvis (major and minor calyces), branches of nerves, arteries, and veins, and loose connective tissue and fat.
Kidney Function
- Kidneys maintain homeostasis through:
- excreting metabolic waste products (urea, uric acid, creatinine, bilirubin).
- maintaining water balance regulating urine volume.
- maintaining electrolyte balance, specifically sodium concentration in relation to water balance.
- maintaining acid-base balance eliminating metabolic acids (sulfuric and phosphoric acids).
Kidney - Hematopoietic Function
- The kidney secretes erythropoietin (stimulates red blood cell production) and thrombopoietin (stimulates thrombocyte production).
Kidney - Endocrine Function
- Hormones secreted include: erythropoietin, thrombopoietin, renin, and 1,25-dihydroxycholecalciferol (calcitriol).
Kidney - Regulation of Blood Pressure
- Kidneys play a crucial role in long-term regulation of blood pressure.
- Regulation is achieved by regulating the volume of extracellular fluid and via the renin-angiotensin mechanism.
Kidney - Regulation of Blood Calcium Level
- Kidneys activate 1,25-dihydroxycholecalciferol into vitamin D, which is necessary for calcium absorption from the intestines.
Nephron
- The nephron is the structural and functional unit of the kidney.
- Each kidney contains approximately 1 to 1.3 million nephrons.
- Each nephron has two parts:
- The renal corpuscle or Malpighian corpuscle, which filters blood and initiates urine formation. It further divides into glomerulus and Bowman's capsule.
- The renal tubule, which continues from the Bowman's capsule, is comprises of the proximal convoluted tubule, loop of Henle, and distal convoluted tubule.
Glomerulus
- The glomerulus is a tuft of capillaries enclosed by Bowman's capsule.
- Glomerular capillaries arise from the afferent arteriole.
- The afferent arteriole branches into smaller capillaries which rejoin to form the efferent arteriole that leaves Bowman's capsule.
Bowman's Capsule
- Bowman's capsule is a capsular structure surrounding the glomerulus.
- It has two layers: inner visceral layer and outer parietal layer.
- The visceral layer covers the glomerular capillaries.
- Parietal layer is continuous with the wall of the tubular portion of the nephron.
- The space between the visceral and parietal layers forms the lumen of the tubular portion.
Functional Histology of Malpighian Corpuscle
- Glomerular capillaries are made up of a single layer of endothelial cells containing pores (fenestrae or filtration pores), with a diameter of 0.1 μm.
- Both layers of Bowman's capsule comprise a single layer of flattened epithelial cells with cytoplasmic extensions called pedicles or foot processes, resting on the basement membrane.
- Epithelial cells with pedicles are called podocytes.
- Podocyte pedicles are separated by cleft-like spaces called slit pores.
Urine Formation
- Glomerular filtration is the process by which blood is filtered through the glomerular capillaries.
- The filtration membrane comprises the glomerular capillary membrane, basement membrane, and visceral layer of Bowman's capsule.
- The filtered fluid is called glomerular filtrate.
Glomerular Filtration Rate (GFR)
- GFR is the sum total of filtrate formed by all the nephrons in both kidneys within a specific time.
- Normal GFR is about 125 mL/minute or 180 L/day.
- GFR depends on three pressures: glomerular capillary pressure (PGC), colloidal osmotic pressure (πGC), and hydrostatic pressure in the Bowman's capsule (PBC).
Factors Affecting Glomerular Filtration
- Increased systemic arterial blood pressure and renal blood flow increases GFR.
- Increased plasma proteins concentration and urinary tract obstruction decrease GFR.
Tubular Reabsorption
- Definition: The process by which water and other substances are reabsorbed from the renal tubules back into the blood.
- Essential substances (glucose, amino acids, vitamins) are completely reabsorbed.
- Unwanted substances (metabolic wastes) are not reabsorbed and are excreted.
- Reabsorption occurs in almost all parts of the nephron's tubular portion.
- Proximal convoluted tubule reabsorbs 88% of the filtrate
- The process depends on absorption forces.
Mechanisms of Tubular Reabsorption
- Active transport: Substances move against the electrochemical gradient, requiring energy (ATP).
- Passive transport: Substances move along the electrochemical gradient without needing energy.
- Bulk flow through pressure gradients.
- Hydrostatic pressure in peritubular capillaries (Pc)
- Hydrostatic pressure in renal interstitium (Pif)
- Colloid osmotic pressure in peritubular capillaries (πc) (proteins)
- colloid osmotic pressure in the renal interstitium (πif) (proteins)
Regulation of Tubular Reabsorption
- Glomerulotubular balance: Balance between filtration and reabsorption of solutes and water.
- Nervous factors: Activation of the sympathetic nervous system (vasoconstriction of efferent arterioles), increasing reabsorption, and influencing renin production (indirectly).
- Hormonal factors: Various hormones (aldosterone, angiotensin II, antidiuretic hormone) affecting sodium and water reabsorption.
Tubular Secretion
- Substances are transported from blood into the renal tubules.
- Examples: Potassium, ammonia, hydrogen ions, and urea.
Tubular Excretion
- The final product of tubular processing (containing wastes, and water) passes through the renal collecting ducts, ureters, and the urinary bladder—awaiting elimination from the body.
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Description
This quiz covers the functions and anatomy of the renal system, including the excretion processes and the role of various organs. Test your knowledge on how the kidneys and associated structures contribute to waste elimination in the body.
