Module 9: KUB, RBF, Tubules, Hormones And Renal Function Tests (a) Flashcards
Renal system Overview
-Primary Functions
- Maintain stable internal environment for optimal cell tissue metabolism — Ex Blood pressure*
- Balance solute and water transport
- Excrete metabolic waste products
- Conserve nutrients
- Regulate serum pH
Renal system Overview
-Endocrine Functions?
- Renin — Important for regulation of BP
- Erythropoietin — Production of erythrocytes in response to low oxygenation
- 1,25-dihydroxyvitamin D3 — important in metabolism of calcium — performs gluconeogenesis in renal cortex
- Forms urine
Nephron
-Info
- Functional unit of the kidney
- Superficial cortical nephrons — 85% of all nephrons — located on outer edge
- Midcortical nephrons
- Juxtamedullary nephrons — Concentrate urine and secrete renin - EACH kidney contains 1.2 million nephrons
Glomerulus
-Info
- Afferent arteriole — Supplies glomerulus w/ blood
- Efferent arteriole — Returns blood to systemic blood flow — Away from glomerulus
- Juxtaglomerular apparatus **
- Controls renal blood flow, glomerular filtration, and renin secretion
Glomerulus
-Juxtaglomerular Apparatus
- Control renal blood flow, glomerular filtration, and renin secretion
- Juxtaglomerular cells — Specialized cells located around afferent arterioles
- Macula densa — Specialized sodium and chloride sensing cells — Found in distal convoluted tubules where afferent and efferent arterioles enter glomerular space
Glomerulus & Juxtaglomerular Apparatus
-Function
- Juxtaglomerular cells — Surround afferent arteriole — Distal tubule and afferent arteriole come into contact
- Macula Dens — Line the Distal tubule — Measure sodium concentration of urine being excreted — Regulates sodium concentration
- Glomerulus — Tuft of capillaries surrounded by Bowman’s capsule —
—Space between glomerulus and Bowman’s capsule is the Bowmans Space — Filtrate (Mostly water) is in this space
—Filtrate in Bowman’s space should NEVER contain PROTEIN when kidney is healthy
Glomerulus
-3 layers?
- Endothelial cell layer — forms lumen and comes into contact with blood — contains pores that allow for particles to pass through
- Basement Membrane — Selectively permeable & NEGATIVELY charged (Repels negatively charged material) Ex of Neg charged is: ALBUMIN
—Damage to Basement membrane removes Negative charge — Allows proteinuria and hematuria** - Visceral Capillary Epithelium — Contains foot processes of podocytes — Interlocking fingers serve as filtration slits
Bladder
-Components
- Detrusor muscle — “basket weave” of smooth muscle — muscle fibers run in different directions to cause bladder to contract
- Trigone — Smooth triangular region where 2 ureters and urethra sit
- Transitional epithelium — Allows bladder to expand and contract — Provides interface between urinary space and underlying vasculature
Urethra
-Components
- Internal sphincters — autonomic regulation; parasympathetic fibers— smooth muscle located at junction of bladder & Urethra
- External sphincter — Voluntary control — striated skeletal muscle — Skeletal motor neurons in pudendal nerve (L4 -S3)
- Female Urethra — 3 to 4 cm long — Increased UTI’s in female
- Male urethra — 18 to 20 cm long
Renal Blood Flow
-Process
- Kidneys receive 1000 to 2000 ml/min of blood
- GFR
- Filtration of plasma into bowman space
- 120 to 140 ml of plasma per minute
- DIRECTLY related to perfusion pressure in the glomerular capillaries** - If MAP decreases or renal artery vascular resistance increases, renal blood flow decreases*
Glomerular Filtration
-Process
- Glomerulus is freely permeable to water and relatively impermeable to large colloids such as plasma proteins
- Size and electrical charge are important factors that affect permeability
—Positive-charged particles permeate the membrane more readily than neutral or Negative-charged particles**
Glomerular Filtration
-Net Filtration Pressure**
- Combined effect of forces favoring and forces opposing filtration
- Favoring Forces — Capillary hydrostatic pressure
- Opposing Forces — Oncotic pressure in the capillary AND hydrostatic pressure in Bowman capsule
- Glomerular Filtration Results in — NET POSITIVE FILTRATION 10mmHg leaving glomerulus into proximal convoluted tubule
Renal Blood Flow Regulation Systems
-3 Methods
- Auto regulation
- Myogenic mechanism
- Tubuloglomerular feedback - Neural Regulation
- Hormonal Regulation
- RAAS
- Natruiretic Peptides
Renal Blood Flow Regulation & GFR
-Auto-Regulation
- Goal is to maintain constant GFR when atrial pressure is between 80 to 180mmHg
- As SBP increases, afferent arterioles constrict preventing an increase in filtration pressure**
—Also prevents wide fluctuations in the systemic arterial pressure from being transmitted to glomerular capillaries
Renal Blood Flow Regulation
-Auto-regulation — Myogenic Mechanism (Stretch)
- As atrial pressure declines, stretch on the afferent arteriolar smooth muscle decreases
—Afferent arteriole relaxes and glomerular perfusion INCREASES
Renal Blood Flow Regulation
-Auto-Regulation Tubuloglomerular Feedback
- When sodium filtration increases (As sensed by the macula densa*), GFR needs to be decreased
- Macula densa cells stimulate afferent arteriolar VASOCONSTRICTION
Juxtaglomerular Granular Cells
-Function?
- Related to Hormonal aspect of regulation — Also sense STRETCH
—When BP is low, these cells release RENIN — This converts Angiotensinogen into Angiotensin-1 — SYSTEMIC vasoconstriction
Renal Blood Flow Regulation
-Neural Regulation
- Sympathetic Nervous System — Sympathetic stimulation causes Afferent arteriole to vasoconstrict, which decreased GFR
- Baroreceptors Reflex — Measures BP in carotid artery and aortic arch — Activated with BP decreases — Causes afferent arteriole to vasoconstrict — Causes reduction of GFR and increase in BP
- Severe hypoxia
- Carotid and aortic chemoreceptors are stimulated d/t SEVERE HYPOXIA — Causes GFR reduction d/t sympathetic stimulation
- Increased BP allows for increase blood flow and oxygenation to lungs
Renal Blood Flow Regulation
-Hormonal Regulation
- RAAS
—Increases systemic arterial pressure & increases sodium reabsorption - RENIN — Enzyme is formed and stored in afferent arterioles of juxtaglomerular apparatus
—Renin helps form angiotensin-1
Renal Blood Flow Regulation
-Where is RENIN formed/Stored?
- Renin enzyme is formed and stored in afferent arterioles of the juxtaglomerular apparatus
—Renin helps form angiotensin-1** - Renin is released when:
— BP decreases, Sodium decreases (Macula densa cells), Sympathetic stimulation, Prostaglandin stimulation
Renal Blood Flow Regulation
-Renin Function
- Converts Angiotensinogen into Angiotensin-1
Renal Blood Flow Regulation
-Hormonal Regulation RAAS — Angiotensin-II
- Stimulates secretion of aldosterone by adrenal cortex**
- POTENT vasoconstrictor
- Also stimulates ADH (AKA vasopressin) secretion and thirst
- Aldosterone — Increases BP by increasing sodium/chloride reabsorption by distal convoluted tubules and collecting ducts
—Fluid will follow the reabsorption and increase BP - Vasopressin — increases WATER permeability by distal convoluted tubule and collecting ducts
—Causes Increase of WATER being reabsorbed instead of secreted
Renal Blood Flow Regulation
-Hormonal Regulation — Aldosterone
- Aldosterone — Increases BP by increasing sodium/chloride reabsorption by distal convoluted tubules and collecting ducts
—Fluid will follow the reabsorption and increase BP
Renal Blood Flow Regulation
-Hormonal Regulation — Vasopressin
- Vasopressin — increases WATER permeability by distal convoluted tubule and collecting ducts
—Causes Increase of WATER being reabsorbed instead of secreted