Urinary Flashcards
What are the 8 functions of the kidney?
Regulating total water volume and total solute concentration in water
Regulating ECF ion concentrations
Ensuring long-term acid-base balance
Removal of metabolic wastes, toxins, drugs
Endocrine functions
-Renin - regulation of blood pressure
-Erythropoietin - regulation of RBC production
Activation of vitamin D
Gluconeogenesis during prolonged fasting
What are the 4 organs of the urinary system?
kidney, ureters, urinary bladder, urethra
The R/L kidney is lower because ___
R kidney lower than L because crowded by liver
The renal hilum leads to the ___ where ___ (4) enter/exit.
into the renal sinus where nerves, vessels, lymphatics, ureter enter/exit
the ___ gland rests on top of the kidney
adrenal
What are the layers of surrounding supporting tissue of the kidney? (3) What do they do?
Renal fascia - Anchoring outer layer of dense fibrous connective tissue
Perirenal fat capsule - Fatty cushion
Fibrous capsule - Prevents spread of infection to kidney
the renal cortex appears ___.
granular
The renal medulla is composed of ___ separated by ___.
medullary pyramids separated by renal columns
Compare and contrast the male and female urethras. (2)
- male urethra much longer
- male has 2 functions: urine discharge & secretion semen
Identify the major blood vessels associated with the kidney & trace the path of blood through the kidney - Lab
Trace the path of filtrate/urine from the renal corpuscle to the urethral opening.
peritubular capillaries > PCT > nephron loop > DCT > collecting duct > renal column > minor calyx > major calyx > renal pelvis > ureter
What are the 2 main parts of a nephron?
Renal corpuscle
Renal tubule
The ___ of the kidney allows filtrate formation.
glomerulus
What cells make up the nephron in each part? - image
What are the 2 layers of the glomerular capsule? What cells make up each? What do the visceral layer cells create and allow through into where?
- Parietal layer - simple squamous epithelium
- Visceral layer - podocytes
- Filtration slits between foot processes allow filtrate to pass into capsular space
What are the 3 parts of a renal tubule?
Proximal convoluted tubule
Proximal → closest to renal corpuscle
Nephron loop
Distal convoluted tubule
Where is the PCT confined to? What kind of cells are they made of? What 2 special structures of the cell does the PCT have? What is its functions? (2)
- confined to cortex
- cuboidal cells
- dense microvilli (brush border ↑surface area); large mitochondria
- secretion & absorption
The nephron has a ___ descending limb and ___ ascending limb,
- descending thin limb
- Thick ascending limb
Distal convoluted tubules (DCT) do not have ___. Its function is ___. Where is it confined to?
Cuboidal cells with very few microvilli
Function more in secretion than reabsorption
Confined to cortex
List the three major processes in urine formation and where each occurs in the nephron and collecting system.
Glomerular filtration
- produces cell/protein free filtrate (blood plasma minus proteins)
- takes place in renal corpuscle
Tubular reabsorption
- Selectively returns substances from filtrate in renal tubules/collecting ducts to blood
- takes place in renal tubules/collecting ducts
Tubular secretion
- substances from blood to filtrate in renal tubules and collecting duct
- takes place in renal tubules/collecting ducts
What are the 2 types of cells in the collecting duct? What do they do? Which one has microvilli?
principal - Maintain water and Na+ balance
intercalated - help maintain acid-base balance of blood (microvilli)
What passes the filtration membrane? What does not pass? Does nitrogenous waste pass?
Water, solutes smaller than plasma proteins (glucose, aa, nitrogenous waste) pass; normally no cells pass
Where are the cortical nephrons? Juxtamedullary nephrons? What do juxtamedullary nephrons have? They are important in the production of ___.
-cortical = cortex
Juxtamedullary = invade medulla
- Ascending limbs have thick and thin segments
- vasa recta
- production of concentrated urine
Renal tubules are associated with these 2 capillary beds.
Glomerulus
Peritubular capillaries
Glomerulus vs peritubular capillaries.
BP in the glomerulus is ___ because ___ (2). They are specialized for ___. They are fed and drained by ___
BP in peritubular capillaries is ___ because they contain ___. They are specialized for ___ (2). They are fed by ___ and drained by ___.
Glomerulus
- blood pressure in glomerulus high because
- -Afferent arterioles larger in diameter than efferent arterioles
- -Arterioles are high-resistance vessels
- specialized for filtration
- fed and drained by arteriole
Peritubular capillaries
- low BP because have pores
- for absorption water & solutes
- arise from efferent arterioles and drained into venules
The ___ replaces peritubular capillaries in the juxtamedullary nephrons.
vasa recta
What are the 3 cells that make up the juxtaglomerular complex? (JGC) What are their functions? Which one secretes renin?
- macula densa - sense NaCl content of filtrate
- granular cells - sense blood pressure in afferent arteriole; secrete renin
- extraglomerular mesangial cells - pass signals between macula densa and granular cells
What are the 3 layers of the filtration membrane?
- Fenestrated endothelium
- Basement membrane (fused basal laminae of two other layers)
- Foot processes of podocytes with filtration slits (slit diaphragms repel macromolecules)
Macromolecules that get stuck in filtration membranes are engulfed by
glomerular mesangial cells
Why do plasma proteins remain in the blood? What does this prevent?
maintains colloid osmotic pressure → prevents loss of all water to capsular space
Why is the Glomerular blood pressure high? why this blood pressure is significant for urine formation?
- Because efferent arteriole is high resistance vessel with diameter smaller than afferent arteriole
- allows for the salts to be pushed out of capillaries without reabsorption occuring
What is the outward force affecting filtration? What is it called? What does it promote? Describe the force.
What is the inward force affecting filtrate formation? (2)
What do these 2 forces ultimately create?
Out
- Hydrostatic pressure in glomerular capillaries = Glomerular blood pressure
- Outward pressures promote filtrate formation
- force pushing water, solutes out of blood
In
- Hydrostatic pressure in capsular space (Pressure of filtrate in capsule)
- Colloid osmotic pressure in capillaries (“Pull” of proteins in blood)
sum = Net filtration pressure (NFP)
-55 mm Hg forcing out; 45 mm Hg opposing = net outward force of 10 mm Hg
What is the Glomerular Filtration Rate (GFR)? What increases GFR? (3)
-Volume of filtrate formed per minute by both kidneys
Increase
- NFP
- Total surface area available for filtration
- Filtration membrane permeability
True or false
Most of tubular contents reabsorbed to blood
What is absorbed?
true
All organic nutrients, water, ions reabsorbed
The 2 types of tubular reabsorption are ___ and the 2 routes are ___.
- Includes active and passive tubular reabsorption
- Transcellular or paracellular routes
Describe the trans and paracellular route of tubular reabsorption. Which process is faster?
paracellular faster
In the proximal convoluted tubules (PCT) how is:
- Na+ transported into the IF? what does this create? this allows for ___ at the apical membrane
- how are glucose, aa, some ions, vitamins transported at the apical membrane?
- how is water transported? what does this create?
- how are lipid-soluble substances transported?
- how are other ions & urea transported?
What are the 2 different types of water reabsorption thru aquaporins? How are they different?
obligatory water reabsorption - Aquaporins always present in PCT (proximal convoluted tubule) →
facultative water reabsorption - Aquaporins inserted in collecting ducts only if ADH present (upregulated) →
___ is the site of most reabsorption in the nephron. What is reabsorbed? (5) Which ions? (3) Is uric acid reabsorbed?
proximal convoluted tuble
-nutrients, Na+, water, ions (Cl-, Ca, K), uric acid/urea
In the nephron loop, ___ leaves in the descending limb and ___ in the ascending limb.
descending = water ascending = solutes
Explain why the differential permeability or impermeability of specific sections of the nephron tubules is necessary for urine formation.
to maintain certain levels of ions, nutrients, vitamins, and water; for Ion exchange
Compare and contrast passive and active tubular reabsorption.
- active requires ATP (either primary or secondary active transport)
- passive moves down electrical gradient (facilitated diffusion, osmosis - water, diffusion - ions, fat-soluble substances)
Most reabsorption occurs in the ___. What gets reabsorbed?
proximal convoluted tubule
-K+, H+, NH4+, creatinine, organic acids and bases, HCO3-
What are the functions of tubular secretion? (4)
- Disposes of substances (e.g., drugs) bound to plasma proteins
- Eliminates undesirable substances passively reabsorbed (e.g., urea and uric acid)
- Rids body of excess K+ (aldosterone effect)
- Controls blood pH by altering amounts of H+ or HCO3– in urine
How does an increase in GFR affect systemic blood pressure?
↑ GFR > ↑urine output > ↓ blood pressure, and vice versa
What is the goal of the intrinsic and extrinsic controls? What controls them?
- Goal of intrinsic controls - maintain GFR in kidney
- Act locally within kidney to maintain GFR
- Goal of extrinsic controls - override intrinsic control and maintain systemic blood pressure
- Nervous and endocrine mechanisms that maintain blood pressure
What does a constant GFR allow?
allows kidneys to make filtrate and maintain extracellular homeostasis
What are the 2 types of renal autoregulation (intrinsic control)?
Myogenic mechanism
Tubuloglomerular feedback mechanism
Describe the myogenic mechanism. It is an example of ___ to maintain___. What does this protect against?
- example of intrinsic control to maintain GFR
- ↑ BP → muscle (granular cells) stretch → constriction of afferent arterioles → restricts blood flow into glomerulus
- Protects glomeruli from damaging high BP
Describe the tubuloglomerular feedback mechanism. It is an example of ___ to maintain___. What cells directs its process? What does it respond to?
- example of intrinsic control to maintain GFR
- directed by macula densa cells; respond to filtrate NaCl concentration
- If GFR ↑→ filtrate flow rate ↑→ ↓ reabsorption time → high filtrate NaCl levels → constriction of afferent arteriole → ↓ NFP & GFR → more time for NaCl reabsorption
Under normal conditions at rest. Renal blood vessels are ___, and the ___ mechanisms prevail.
Renal blood vessels dilated
Renal autoregulation mechanisms prevail
For extrinsic control of the sympathetic nervous system, what does a decrease in blood pressure (low ECF) do? (3)
- nor/epinephrine released >
- Systemic vasoconstriction → increased blood pressure
- Constriction of afferent arterioles → ↓ GFR → increased blood volume and pressure
(if time)
Extrinsic Controls: Renin-Angiotensin- Aldosterone Mechanism
What are the 3 pathways to renin release? by which cells? This ultimately does what to the BP?
-release by granular cells
- Direct stimulation (epi) of granular cells by sympathetic nervous system
- Stimulation by activated macula densa cells when filtrate NaCl concentration low
- Reduced stretch of granular cells
- increase BP
aquaporins are always present in the PCT, which results in ___. They are inserted in collecting ducts if ___ is present (upregulated), which results in ___.
- Aquaporins always present in PCT (proximal convoluted tubule) → obligatory water reabsorption
- Aquaporins inserted in collecting ducts only if ADH present (upregulated) 🡪 facultative water reabsorption
Summary of tubular reabsorption and secretion - image.
What is the function of the ureter?
carry urine from kidney to bladder
What is the function of the urinary bladder?
Muscular sac for temporary storage of urine
Relate the anatomy and histology of the bladder to its function.
- Mucosa - transitional epithelial mucosa allows for expansion of detrusor muscles
- rugae also allows for distension
how does the urinary bladder move when it fills with urine and what does it not change?
Expands and rises superiorly during filling without significant rise in internal pressure
The urethra contains which 2 sphincters? What muscles are they made of?
Internal urethral sphincter
-Involuntary (smooth muscle) at bladder-urethra junction
External urethral sphincter
-Voluntary (skeletal) muscle surrounding urethra as it passes through pelvic floor
What is the function of the urethra?
tube through which urine leaves body, allows for urination
What is osmolality? It reflects the ability to cause ___. How do kidneys regulate its homeostasis?
Number of solute particles in 1 kg of H2O (water vs solute amount)
Reflects ability to cause osmosis
Kidneys regulate homeostasis with countercurrent mechanism
What is the purpose of the countercurrent mechanism? (2) What does the loop of henle and vasa recta act as? What does the collecting duct determine?
- Establish and maintain osmotic gradient (osmolality) to keep materials moving from renal cortex through medulla
- Allow kidneys to vary urine concentration
The long nephron loops (loop of henle) of juxtamedullary nephrons create the gradient - They act as countercurrent multipliers.
The vasa recta preserve the gradient - They act as countercurrent exchangers.
the collecting ducts determine the final concentration and volume of urine
The loop of henle act as ___, which means they ___ the gradient. The multiplier depends on 3 properties. One is ___ The other 2 is as follows: In the descending limb, ___ is permeable. Hence osmolality increase/decrease. In the ascending limb, ___ is permeable (specifically these 2 ions are absorbed in the thick/thin segment).
- Countercurrent Multiplier
- create the gradient
- fluid flowing in opposite directions in adjacent parallel sections
Descending limb
- permeable to water that leaves the filtrate
- increases osmolality
Ascending limb
- permeable to solutes so osmolality decreases
- Na and Cl reabsorbed in thick segment
Vasa recta is responsible for the ___, that ___ medullary gradient. It does so by (2).
- countercurrent exchanger, maintains gradient
- removal of salt from interstitial space
- remove reabsorbed water
Describe the mechanism for overhydration/dehydration with ADH - image.
-if dehydrated, not too much water in urine so expel mostly ions
Overhydration = small/large volume dilute/concentrated urine Dehydration = small/large volume dilute/concentrated urine
overhydration = large volume dilute urine dehydration = small volume concentrated urine
Where does urine conveying begin from kidneys to bladder
L2 as continuation of renal pelvis
As bladder pressure increases, ___ close, preventing backflow of urine.
distal ends of the ureters
Describe the role of kidney in vitamin D activation.
PTH stimulates activation of vitamin D by calcitriol by the kidneys, which accelerates Ca ion absorption in the small intestine
Describe the role of kidney in regulating erythropoiesis.
- Erythropoietin (EPO) stimulates formation of erythrocytes
- when kidney cells become hypoxic (O2 deficient) unable to degrade hypoxia-inducible factor (HIF)
- as HIF accumulates, EPO synthesis & release accelerates
Describe the function of the juxtaglomerular apparatus. What are the 3 types of cell found and what do they do? What happens when there is high salt concentration? Low salt?
-function = maintain blood pressure and glomerular flow rate
- macula densa = picks up on the amount of salt in the distal convoluted tubule
- granular cells = senses blood pressure; regulate the constriction/dilation of afferent arteriole
- extraglomerular mesangial cells = pass signals between the macula densa and granular cells
- lots of salt in blood (too much pressure) = granular cells widens artery so not as much hydrostatic pressure & reduces amount of salt being pushed out because so much salt is already there
- less salt = arteries constrict to pull more salt
In the distal convoluted tubule and collecting duct, reabsorption is regulated by ___, specifically (4). Each of these regulate
Reabsorption hormonally regulated Antidiuretic hormone (ADH) – Water Aldosterone – Na+ (therefore water) Atrial natriuretic peptide (ANP) – Na+ PTH – Ca2+
How does ADH affect reabsorption in the DCT & collecting duct? What organ is it released by?
Released by posterior pituitary gland
Causes collecting ducts to insert aquaporins → increase water reabsorption
Aldosterone affects reabsorption in the ___ (2). What does this do? (2)
- Targets collecting ducts and distal DCT
- Promotes synthesis of apical Na+ and K+ channels for Na reabsorption; water follows
- increase blood pressure; decrease K+ levels
atrial natriuretic peptide (ANP) affects reabsorption in the ___ (2). How does this work?
- DCT & collecting duct
- Released by cardiac cells if blood volume or pressure elevated
- Reduces blood Na+ → decreased blood volume and blood pressure
PTH affect reabsorption in the ___ (2). What ion does it re/absorb?
- DCT & collecting duct
- increase Ca2+ reabsorption
What are the 2 different types of water reabsorption thru aquaporins? How are they different?
Aquaporins always present in PCT (proximal convoluted tubule) → obligatory water reabsorption
Aquaporins inserted in collecting ducts only if ADH present (upregulated) → facultative water reabsorption
Explain how the urinary system relates to other body systems to maintain homeostasis.
Muscular/nervous system - regulation of K, Ca, Na in ECF crucial for muscle contractility & neural function
Nervous system - SNS controls renin-angiotensin-aldosterone mechanism
Endocrine - ADH, aldosterone, ANP regulate renal reabsorption of water & electrolytes; produce EPO
most reabsorption is by ____
secondary active transport
alcohol is a dieuretic why?
inhibits ADH
