Renal Physiology Flashcards
How much blood do the kidneys receive each minute?
over a litre
What is the Rate of blood filtration per day?
45 gallons (180L)/day
How much blood do you have in your body?
7 -8 L
How much times is your entire blood volume filtered in a day?
20 - 25x
How much urine is eliminated per day?
1.5 L
What does obligate urine production mean?
Happens regardless of anything else, including dehydration
What is the specialized filtering unit of the kidneys?
Nephrons
Where are the kidneys?
Retroperitoneal in the superior lumbar region
Which kidney is lower than the other and why?
The right kidney is lower due to being crowded by the liver
Where do all the fluids enter and exit the kidney?
The renal hilus
What is the cortex of the kidney?
granular Superficial region
What is the medulla of the kidney?
Internal anatomy of the kidney, contains renal pyramids
What is the renal pelvis?
Flat funnel shaped tube lateral to the hilus
What are the major calyces?
Large branches of the renal pelvis that collect urine draining from papillae and empty it into the pelvis
How much systemic cardiac output flows thought the kidneys each minute?
one-fourth (1200ml)
What is the nerve supply of the kidneys?
The Renal plexus
What is glomerular filtration?
Excess fluid and waste products are filtered into collecting tubules from the blood
How many nephrons does a healthy adult have?
0.8 - 1.5 million
What is the renal corpuscle?
The Glomerulus and it’s capsule, Bowman’s capsule
What is the glomerulus?
Tuft of capillaries associated with a renal tubule
What is Bowman’s capsule?
Blind, cup shaped end of a renal tubule that surrounds the glomerulus
What do the epithelial podocytes of the capsule do?
The openings between the foot processes of the podocytes allow filtrate to pass into capsular space
Why is the afferent arteriole bigger?
More blood comes into the glomerulus than comes out
What are the two types of nephrons?
85% Cortical nephrons
15% Juxtamedullary nephrons
Where are the Juxtamedullary nephrons and what do they do?
Going from cortex into the medulla, they have longer loops of Henle that produce more concentrated urine and have vasa recta surrounding their loop of Henle
What are the two capillary beds of the nephrons?
Glomerulus
Peritubular capillaries
Why is blood pressure high in the glomerulus?
Arterioles are high-resistance vessels, afferent ones are larger than efferent ones, causing heightened pressure and forcing filtrate into the glomerulus to relieve the pressure
What is glomerular filtrate?
It is not urine, it is basically plasma without blood in it
What do the renal tubules reabsorb?
99% of water
All of glucose and amino acids
Most Na+ and Cl-
What is the resulting urine that has been completely filtered?
Metabolic waste and unneeded substances
What are the five segments of the renal tubule?
Proximal Convoluted Tubule Proximal Straight Tubule Thick Ascending Limb Distal Convoluted Tubule Collecting Duct
What occurs in the Loop of Henle?
Water is reabsorbed but ions are not, resulting in more concentrated filtrate, as the loop descends while ions are reabsorbed and water is not as the loop ascends
What is the the usual value of filtrate concentration at the bottom of the loop of Henle?
1200
What is the Counter-Current Multiplier system?
the process of using energy to generate an osmotic gradient between the cortical and medullary regions that enables you to reabsorb water from the tubular fluid and produce concentrated urine
What does the vasa recta of the juxtamedullary nephrons do?
delivers blood to medullary cells and returns water and solutes to general circulation
How do the kidneys maintain water volume?
Through the properties of the Loop of Henle and ADH (Vasopressin)
What is the Juxtaglomerular Apparatus?
Where the distal tubule lies against an arteriole, the arteriole walls have juxtaglomerular cells that surround them
What do juxtaglomerular cells do?
These enlarged smooth muscle cells contain renin which acts as mechanoreceptors to monitor blood volume
What is the Macula Densa?
Tall, closely packed distal tubule cells that are adjacent to JG cells which function as chemo/osmoreceptors and monitor salt levels
What do osmoreceptors in the hypothalamus do?
They sense Na+ concentration and have nerve endings in the posterior pituitary that secrete AHD when Na+ gets high along with causing vasoconstriction
What does ADH do?
Controls the ability of water to pass through the cells in the walls of the collecting ducts, the more ADH the more concentrated urine do to more water being reabsorbed
What is the force contraction of the heart?
The amount by which the heart muscle gets stretched by incoming blood
What does blood pressure depend on?
force contraction of the heart
artery and arteriole contraction
circulating blood volume
What does artery and arteriole constriction do?
Causes more resistance to blood flow, requiring higher blood pressure
What does the circulating blood volume do?
The higher the circulating blood volume, the more the heart muscle gets stretched by the incoming blood
What does the body do to protect losing more fluids during rapid blood loss due to trauma?
Nervous system contracts arteriole, reducing urine production along with the renin-angiotensin-aldosterone system that regulates BP and fluid balance
What happens if the specialized cells (juxtaglomerular and macula dense) sense an imbalance?
Renin is released by the juxtaglomerular cells, the renin converts angiotensinogen into angiotensin 1, this is converted to angiotensin 2 by an angiotensin-converting enzyme (ACE) which is found in the lungs
What does angiotensin 2 do?
Causes blood vessels to contract and elevates blood pressure, it also stimulates the adrenal glands to release aldosterone
What does aldosterone do?
Stimulates more Na+ reabsorption in the distal tubule, which takes water with it. This results in increased circulating blood volume and therefore increased BP due to stretched heart muscle
What does parathyroid hormone (PTH) do?
Increases Ca+ reabsorption from the distal tubule of the nephron to restore blood Ca+ levels, it also takes it from the bones and the intestines
What is Atrial natriuretic peptide (ANP)?
Secreted in response to increased atrial pressure, it causes GRF and increased Na+ filtration without compensatory Na+ reabsorption = Na+ and volume loss
What does Erythropoietin (EPO) do?
Secreted by peritubular cells of renal cortex in response to hypoxia, tells the red bone marrow to make RBCs
What does a diet rich in meats provide to blood?
Acid increase
What does a diet rich in fruits and vegetables provide to blood?
Alkaline increase
How does exercise effect the acid-base balance?
Lactic acid is produced and must either be metabolized or eliminated
How does lung disease effect the acid-base balance?
Blocks the diffusion of oxygen, causing blood to be acidic
How does high altitude effect the acid-base balance?
Causes rapid breathing which makes the blood alkaline
How can the kidney correct any imbalance in the acid-base balance of the blood?
It can remove excess hydrogen (acid) or bicarbonate (base) in the urine
What does the acid-base balancing of the kidney depend on?
The amount of bicarbonate filtered in the glomerulus from the blood relative to the amount of hydrogen secreted by cells in the kidney
What is gluconeogenesis?
Kidneys can hydrolyze glucose-6-phosphate into glucose, it contributes to 40% of glucose synthesis when fasting, compensates for the acidity caused by the production of ketones
What does high-fructose beverages do during or following exercise?
Can induce kidney injury and potentially kidney disease, elicits dehydration and elevates biomarkers of kidney injury
What are the risk factors of kidney stones?
Dehydration
Family History
Foods (Sodium, oxalate, acidic)
Obesity
What are the symptoms of kidney stones?
Block urine flow, renal pain that radiates to groin and testes and worsens with movement, blood/pus in urine, urgency and pain
What is used to treat kidney stones?
NSAIDs or opioids for pain
Antiemetic for nausea/vomiting
Alpha blockers/calcium channel blockers as part of medical explosive therapy
What is Extracorporeal shock wave lithotripsy (ESWL)?
High-energy sound waves that break up kidney stones
What is uretroscopy?
Scope inserted in ureter and bladder to reach the stone or break it
