Chapter 25 - Urinary Flashcards
Name the 5 functions of the kidney
- Removal of toxins, metabolic waste, excess ions from blood
- Regulation of blood volume, chemical comp and pH
- Gluconeogenesis
- Endocrine Functions
- Activation of vitamin D`
What are the endocrine functions of the kidney?
1) Production of erythropoietin (triggered by hypoxia)
2) Production of renin
What cavity are the kidneys in?
Outside of abdominal cavity in retroparitoneal
What is the outer region of the internal kidney called? What does it look like?
Renal Cortex
Granular appearance
What is the inner area of the internal kidney called?
Renal Medulla
What is found within the medulla?
Medullary pyramid
Papilla
Major Calyces
Renal Pelvins
Describe the medullary pyramids
Cone-shaped, separated by renal columns
Where is the papilla? What is its role?
Tip of medullary pyramid, releases urine into minor calyx
Where do the major calyces collect and empty urine into?
Collect from minor calyces, empty into renal pelvis
Where does the renal pelvis collect and empty urine?
Collect from ureter, empty into ureter bladder
How is the kidney supplied with blood?
Renal arteries from aorta
How much blood is delivered to each kidney per minute?
25% of cardiac output
What is a nephron?
Structural and functional unit of kidney
What are the 2 main parts of the nephron?
Glomerulus
Renal Tubule
What is the glomerulus?
tuft of capillaries
What is included with the renal tubule?
Starts with bowman’s capsule and then onward
How many nephrons are classified as corticol nephrons? Where are they found?
85% of nephrons, found in cortex
Describe juxtamedullary nephrons. What do they produce?
Have extra long loops of Henie diving into medulla, excessive thin segments
Concentrated urine production
What make up the nephron capillary beds?
Glomerulus Capillaries
Pertibular capillaries
Vasta Recta
What is the path of the glomerulus?
Afferent arteriole, glomerulus, efferent arteriole
What is the role of the glomerulus?
Filtration
How is blood pressure at the glomerulus? How do afferent compare to efferent?
High blood pressure
Afferent are larger in diameter than efferent
What are arterioles?
High resistance vessels
What type of pressure system are peritubular capillaries? What are they adapted for?
Low pressure system for absorption
Where are peritubular capillaries located?
After efferent arterioles
Cling closely to renal tubules
What do peritubular capillaries empty into?
Venules
What is the vasa recta?
Long vessel loops that parallel the loops of henle
Where do the vasa recta come from?
Efferent arteriole from the Juxtamedullary nephron
What is the function of the vasa recta?
formation of concentrated urine with juxtamedullary nephrons
What is the filtration membrane?
Porous membrane between blood and capsular space
What are the 3 parts of the filtration membrane?
Fenestrated endothelium of glomerular capillaries
Basement Membrane
Podocytes
What do podocytes have?
Foot processes and filtration slits
What are the parts of the renal tubule?
Proximal convoluted tubule
Loop of Henle
Distal Convoluted Tubule
Collecting Ducts
What type of cells and parts make up the proximal convoluted tubule?
Cuboidal cells
Dense microvilli on cell borders
large mitochondria
What is the function of the proximal convoluted tubule (PCT)?
Reabsorption
Secretion
What kidney region is the PCT and DCT located?
cortex
Where does the loop of Henle enter?
medulla
What type of limbs does the loop of henle have?
Descending thin segment
Ascending thick segment
What type of cell makes up the thin segment of the loop of henle? How permeable is this tissue?
Simple squamous epithelium
Freely permeable to water
What type of cell makes up the thick segment of the loop of henle?
Cuboidal and columnar
What type of cells make up the distal convoluted tubule? What is their role?
cuboidal cells, very few microvilli
for secretion
What does the collecting duct receive from nephrons?
Receives filtrate from many nephrons
How and where does the distal proximal tubule deliver urine?
Fuses together to deliver urine through papillae into minor calyces
How many times do the kidneys filter the body’s entire plasma volume?
60 times per day
What is filtrate?
Blood plasma minus the proteins and blood cells
What % of filtrate is urine? What is urine?
Less than 1% of total filtrate
Urine is metabolic waste and unneeded substances
What is the GFR?
Glomerular Filtration Rate
Volume of filtrate formed per minute by the kidney
What is the JGA? How many do we have?
juxtaglomeular apparatus
2
What is the juxtaglomeular apparatus important for?
Filtrate formation
blood pressure
What are the 2 main parts of the juxtaglomeular apparatus
Portion of ascending limp of henle
Afferent Arteriole
How many types of afferent arteriole cells are there? What are they?
3
Granular Cells
Macular Densa
Extraglomerular mesangial cells
What are the granular cells?
Enlarged smooth muscles of afferent arteriole
What are the roles of the granular cells?
Secrete Renin
Sense blood pressure by acting as mechanoreceptor
What is the macular densa?
Tall, closely packed cells of the ascending limb of loop of henle
What is the function of the macula densa?
Act as chemoreceptor by sending NaCL concentration of filtrate
What does a high GFR indicate?
Not enough time to reabsorb NaCl, meaning NaCl levels in filtrate are high
What happens when GFR is high?
Triggers release of vasoconstriction to narrow afferent arteriole to lower GFR
What are extraglomerular mesangial cells?
Interconnecting cells with gap junctions that pass signals between macula densa and granular cells
How is the renin-angiotensin mechanism triggered?
Triggered when granular cells of JGA are stimulated to release renin
What does renin cause?
Conversion of angiotensinogen to angiotensin I
What is angiotensin I converted to?
Angiotensin II
What is the role of angiotensin II?
Causes mean arteriole pressure to increase
Stimulates reabsorption of Na+
Constricts efferent arterioles
How does angiotensin II stimulate Na+ reabsorption?
- Acts directly on renal tubule
- Trigger release of aldosterone and ADH
- Activates thirst center
Who produces ADH?
hypothalamus
What happens when efferent arterioles are constricted?
Decreases pertibular capillary pressure and increases fluid reabsorption
What type of process is tubular reabsorption?
Selective transepithelial process with active and passive pathways
What happens during tubular reabsorption?
- All organic nutrients are reabsorbed
2. Water and ion reabsorption are hormonally regulated
What hormones regulate water and ion reabsorption?
ADH
Aldosterone
What are the two pathways of the selective transepithelial process?
Transcellular
Paracellular
What does the reabsorption of Na+ allow?
Provides energy and means for reabsorbing most materials
How is sodium reabsorbed?
- Organic nutrients via active transport
- water via osmosis and aquaporins
- Cations via diffusion
What is the site of most reabsorption?
Proximal Convoluted Tubule (PCT)
What is reabsorbed via the PCT?
65% of sodium and water
All organic nutrients
IONs
small proteins
What is reabsorbed via the descending loop of henle?
H20
What is reabsorbed via the ascending loop of henle?
Sodium, potassium, Chloride
How is reabsorption in the distal convoluted tubule regulated?
Hormonally
Aldosterone for sodium
PTH for calcium
Who secretes ADH? How does ADH reabsorb water?
Pituitary Gland, Insertion of aquaporins
What is tubular secretion?
Reabsorption in reverse, movement from pertibular capillaries back into filtrate
What is reabsorbed via tubular secretion?
K H NH4 (Amonia) Creatine Organic Acids
What does tubular secretion allow for?
Disposal of substances bound to plasma proteins - urea and uric acid, potassium
How does tubular secretion control blood pH?
Gets rid of H or HCO3
Where/when is urine diluted?
Ascending loop of henle in the absence of ADH
In the formation of concentrated urine, what does ADH trigger?
Reabsorption of H20 in collecting ducts in the presence of ADH
What are diuretics?
Chemicals that enhance urinary output
What are 3 types of diuretics?
Osmotic diuretics
ADH inhibitors
Na+ Reabsorption Inhibitors
What is renal clearance?
volume of plasma that is cleared of a particular substance (usually inulin) in a given time
What are renal clearance tests used for?
- Determine GFR
- Detect glomelular damage
- Track progress of renal disease
What is the role of the ureter?
Transport urine from kidney to bladder
Where does the ureter enter the bladder?
Enter via base of bladder
How is the ureter affected by pressure?
Valves close when bladder pressure increases
What is the urinary bladder?
muscular sac for temporary storage of urine
What is the urethra? What are the two sphincters?
Muscular tube
- Internal Urethral Sphincter
- External Urethral Sphincter
What is the internal urethral sphincter? How does it function?
Involuntary
Contracts to close
What is the external urethral sphincter?
Voluntary, surrounds urethra
How long is the female urethra?
3 to 4 cm
What does the male urethra carry?
semen and urine
What are the 3 parts of the male urethra?
Prostatic Urethra
Membranes urethra
Spongy urethra
What is the longest part of the male urethra?
Spongy urethra (15cm)
What must occur simultaneously for micturition to take place?
Contraction of detrusor muscle via ANS
Opening of internal urethral sphincter by ANS
Opening of External urethral sphincter by Somatic NS
What is the chemical composition of urine?
95% water, 5% solute
What are nitrogenous wastes?
Urea
Uric Acid
Creatine
What are the solutes found in urine?
Na K PO4 SO4 Ca Mg HCo3
What is chronic renal disease? What are it’s causes
GFR less than 60 ml/min
Nitrogenous waste accumulates in blood creating acidic blood ph
Caused by diabetes and high blood pressure
What is normal GFR?
120-125 ml/min
What is renal failure? What is the treatment?
GFR less than 15 ml/min
FIltration stops completely, waste builds up in blood, blood pH imbalanced
Treatment; dialysis or transplan
What is incontinence?
Unconrollable urine caused by stress or overfill
What is renal caliculi?
Kidney stones formed in renal pelvis
What are kidney stones made up?
calcium, magnesium, urin acid salts
Why are causes kidney stones?
CHronic bacterial infection
urine retention
high blood calcium
high urine pH
The _____ cells of the JGA secrete ___ when blood pressure is low
Granular, Renin
The majority of reabsorption occurs in the ____
Proximal convoluted tubule
