Ch 25 - The Urinary System
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230 Terms
How many liters of fluid are filtered from blood by the kidneys every single day?
200 Liters
Kidney function?
To maintain the composition of the body’s extracellular fluids by filtering the blood
What is involved when the kidney filters blood? (5 things)
Regulates the total body water volume and concentration of solutes in water
Regulates concentration of ions in ECF
Acid-base balance
Remove toxins, metabolic wastes, and other foreign substances
Hormone production - EPO and renin
Each kidney lies between the _ and _
the parietal peritoneum and dorsal body wall
Kidneys are why type of organ?
retroperitoneal organs
Medial portion of kidney is _
concave
What enters in the renal hilum? (3)
Ureters
renal blood vessels
lymphatics
Where does the adrenal gland sit?
it sits immediately superior to each kidney
What are the supporting external structures of the kidneys? (3)
Renal fascia
Perirenal fat capsule
Fibrous capsule
What is the renal fascia's definition and function?
It is a dense connective tissue and it anchors kidneys to surrounding structures
What is the perirenal fat capsule definition and function?
It is a fat mass surrounding the kidneys and it cushions kidneys from physical trauma
What is the fibrous capsule's definition and function?
It is a thin, transplant capsule, and it prevents disease from spreading to the kidneys from other parts of the body
What are the 3 major internal regions of the kidney’s?
Renal cortex
renal medulla
renal pelvis
What does the renal cortex do?
It provides an area for glomerular capillaries and blood vessel passage, and EPO is produced here.
What does the renal medulla contain?
Contains several renal pyramids
what are renal pyramids filled with? (2)
Packed with capillaries
urine-collecting tubes
What does the renal medulla do? (3)
allows for some water reabsorption
electrolyte balance
disposal of waste and H+ ions.
What is the renal pelvis?
It is the open space in the center of each kidney.
The pelvis branches to form?
Branches to form major calyx
major calyx lead into __ at tip of each renal pyramid
minor calyx
what is the function of the calyx and pelvis?
It collects Urine from the renal medulla
What are the 5 blood supplies to the kidneys?
Renal arteries
Segmental arteries
Interlobar arteries
Arcuate arteries
Cortical radiate arteries
What do renal arteries do?
They deliver blood to the kidneys, and they divide into smaller blood vessels to serve major regions of the kidney
What are segmental arteries?
They are blood vessels that branch off from the renal artery and supply specific regions of the kidney with oxygenated blood
What do the Interlobar arteries do?
They provide a crucial blood supply to the renal lobes so they travel between renal pyramids
What are arcuate arteries?
They are blood vessels that arc over the bases of pyramids.
What are cortical radiate arteries?
They supply blood to renal cortex
How do the veins trace the arterial supply? (in reverse. Name the order)
Cortical radiate veins
Arcuate veins
Interlobar veins
Renal veins
What is a nerve supply to the kidney?
Renal Plexus
What is a renal plexus? what is it made up of? what does it do?
It is an autonomic nerve network, primarily made up of sympathetic vasomotor fibers, that controls blood flow to the kidneys.
Basically adjusts diameter of renal arterioles to adjust blood flow to glomeruli
What is the importance of changing blood flow to the kidneys?
Changing blood flow to the kidneys is crucial for maintaining the kidneys proper function
What is the nephron to the kidney?
It is the functional unit of the kidney
what does a nephron do?
It is responsible for forming filtrate and eventually urine in the kidneys
Each nephron contains a _ and a _
Renal corpuscle and renal tubule
What does a renal corpuscle do?
It filters blood to form the filtrate
What does a renal tubule do?
It reabsorbs some substances from the filtrate and secretes other substances into the filtrate
What happens to anything that is secreted into the filtrate or not reabsorbed from filtrate?
Substances secreted into the filtrate or not reabsorbed in the renal tubules end up in the urine
Where is the renal corpuscle located?
Located entirely within the renal cortex
What are the two subdivisions of the renal corpsucle
Glomerulus
Glomerular capsule
What is a glomerulus?
It is a tuft of capillaries
How does blood enter and leave the glomerulus
Blood enters via the afferent arteriole and leaves via the efferent arteriole
What does it mean when capillaries are very pourous
It means some fluids and substances in the blood can easily be filtered out of the capillary
What is filtrate?
Filtrate is fluid. It is the raw material used to produce urine
What is the glomerular capsule?
It is a double layered structure that completely surrounds glomerular capillaries
What does the inner layer of the glomerular capsule have?
The inner layer has podocytes with foot processes
What is the function and importance of podocytes with foot processes?
It prevents proteins and large molecules from entering the filtrate.
Describe the path of renal tubules and collecting ducts
Begins in the renal cortex, extends into the renal medulla, then returns to the renal cortex
Why is the renal tubules and collecting ducts in a hairpin shape?
This is essential for establishing and maintaining a salt concentration gradient in the renal medulla
What are the subdivisions of the renal tubules and collecting ducts? (4)
Proximal convoluted tubule
Nephron loop
Distal convoluted tubule
Collecting Ducts
What is the proximal convoluted tubule? Location?
It is a large cuboidal epithelial cell with dense microvilli.
It leads immediately off from the glomerulus. Located in the renal cortex.
What two divisions are in the nephron loop?
Descending limb and ascending limb
Where does the nephron loop travel?
It travels between the renal cortex and renal medulla
Where does the descending limb lead?
It leads off from the proximal convoluted tubule.
What is the descending limb permeable and impermeable to?
It is highly permeable to H2O and impermeable to solutes
What is the ascending limb continuous with?
Continuous with the distal convoluted tubule
What is the ascending limb permeable to and impermeable to?
High permeability to solutes and impermeable to H2O
What is the nephron loop function?
It allows the kidneys to vary the concentration of urine according to how much water is reabsorbed at the nephron loop.
Where is the distal convoluted tubule located?
Located in cortex
What is the distal convoluted tubule composed of?
Composed of small cuboidal epithelia
Is the distal convoluted tubule bigger or smaller in diameter than the proximal convoluted tubule?
Smaller diameter than PCT, it contains no microvilli.
What does the microanatomy of the distal convoluted tubule indicate?
It indicates a high degree of active electrolyte transport and reabsorption processes.
What are the important cell types in collecting ducts? (2)
Principal cells
intercalated cells
What do principal cells do?
They maintain Na+ balance in body
What do intercalated cells do?
They help maintain acid-base balance.
What do collecting ducts do?
Each collecting duct receives filtrate from the tubules of multiple nephrons. The collecting ducts fuse together, dump urine into the minor calyces.
What are the types of nephrons? (2)
Cortical Nephrons
Juxtamedullary Nephrons
Where are cortical nephrons located?
Located almost entirely in the cortex. A small portion of the nephron loop is found in the renal medulla
What are juxtamedullary nephrons?
They are nephron loops that deeply invade the renal medulla
How does a change in nephron structure affect urine formation?
It alters the efficiency of filtration, reabsorption, and secretion processes.
What are the capillary beds of nephron?
Glomerulus
Peritubular Capillaries
Vasa Recta
What do the glomerulus do?
It maintains high pressure to increase filtrate production.
What are the peritubular capillaries?
They are low-pressure capillaries arising from the efferent arteriole.
What do peritubular capillaries cling to?
They cling to the proximal and distal tubules of cortical nephrons.
What is the function of the peritubular capillaries?
They reabsorb water and solutes from tubule cells.
Peritubular capillaries empty into __ and then filtered blood returns to circulation
cortical radiate veins
Where is the vasa recta found?
Found only on juxtamedullary nephrons. They run parallel to the long nephron loop.
What does the vasa recta do?
It helps form concentrated urine.
What is the juxtaglomerular complex?
It is a portion of the nephron where the portion of ascending limb lies against the afferent and efferent arterioles.
What is the function of the juxtaglomerular complex?
It regulates blood pressure and filtration rate of the glomerulus
What are the 3 cellular modifications at the juxtaglomerular complex?
Macula densa
Granular cells
Extraglomerular mesangial cells
What are macula densa?
They are chemoreceptor cells
What is the function of macula densa?
They monitor NaCl content of the filtrate entering the distal convoluted tubule
How does the rate of filtrate formation affect NaCl concentration in the distal convoluted tubule?
If the rate of filtrate formation is low, more NaCl is reabsorbed and afferent arteriole vasodilates; If rate of filtrate formation is high, less NaCl is reabsorbed and afferent arteriole vasoconstricts
What are granular cells?
Thrya re specialized smooth muscle cells
Where are granular cells found?
They are found in arteriolar walls of afferent arteriole.
What can granular cells sense?
Can sense blood pressure in the afferent arteriole.
Also stimulated by the macula densa cells
What do granular cells contain?
Contains granules that secrete renin
What does renin affect?
Renin mostly affects the efferent arteriole
Where are extraglomerular mesangial cells?
They are packed between the tubules and arterioles
What is the extraglomerular mesangial cells function?
The function is still unclear.
What is the first step in renal physiology and urine formation?
Step 1: Glomerular filtration
What is glomerular formation?
The production of a cell and protein free filtrate that serves as the raw material for urine
What role does pressure have in glomerular filtration?
The pressure forces fluid out of the glomerular capillary and into the glomerular capsule.
OUTWARD PRESSURE IS ALWAYS HIGH HERE
What does the filtration membrane do?
It allows the passage of water and small solutes into the glomerular capsule.
What does outward pressure promote?
It promotes filtrate formation.
What is hydrostatic pressure in capsular space?
pressure exerted by filtrate that is already in the glomerular capsule
What is colloid osmotic pressure in glomerular capillaries?
They are proteins that are still in capillaries that will “pull” water back in.
What is glomerular filtration rate?
It is the total volume of filtrate formed per minute for all nephrons in the kidney
What are the factors affecting glomerular filtration rate? (3)
Net filtration pressure
Surface area of capillaries
Filtration membrane permeability
The regulation of GFR is tightly regulated for two reasons:
The kidneys need a constant GFR to make filtrate and maintain extracellular homeostasis
Regulating GFR regulates blood pressure in the entire body