Lab Practical Urinary System

Position of the kidneys relative to the body wall and the rib cage

deep to the posterior body wall and at about the level of the 11th and 12th rib

Which kidney lies just a bit lower than the other? Why?

the right because the liver is located on the right side and displaces the right kidney inferiorly

What space do the kidneys lie in?

retroperitoneal space

What layers are the kidneys surrounded by (closest → farthest)?

1. renal capsule

2. cushioning adipose fat

3. renal fascia holding the kidneys and surrounding fat in place

What is the “concave inside” of the bean shape of the kidney?

renal hilus

What parts arise from the renal hilus of the kidney?

ureter, blood vessels, and nerves

What do the renal arteries arise directly from? What makes this important?

the abdominal aorta, they carry a large amount of blood at the full arterial pressure to the kidneys

What connects the kidneys and the ureters?

the renal pelves

What do the renal pelves arise from?

the renal hilus

What do the extensions of the renal pelvis form going into the kidney?

the calyces

What region of the kidney are the glomeruli located?

cortical/cortex region

What region of the kidney do the loops of Henle dip through as they complete their circut?

medullary pyramids

What is the function of the capsule around the kidneys?

provides shape and contains the great pressure generated hydrostatically by the BP (as well as osmotically in some regions)

The kidney is a “______” (bloated/swollen) organ of life…why?

turgid, because of the BP

Why does the cadaver kidney not bear real resemblance to the living organ?

due to the rapid physical, cellular, and structural degradation that occurs after the cessation of blood flow and the onset of brain death

What is an odd traumatic occurrence that can happen to a kidney?

it can be fractured

Why is the mucosa of the bladder “crinkled”?

to allow the bladder to stretch and expand as it fills with urine. These folds, known as rugae, exist when the bladder is empty, allowing it to increase capacity significantly without damaging it

What are the layers of the urinary bladder (inside → out)?

1. mucosa

2. muscularis

3. fibrous adventitia

What parts are a part of the trigone?

2 ureteral openings and the bladder neck at the exit of the urethra

What part of the bladder is an important clinical region because of the frequency of UTIs that persist there?

the trigone

What level are the internal and external urethral sphincters at?

the level of the muscular pelvic floor

What is important about the shape of the muscles that form the spincters?

they are circular rings

What is the working unit of the kidney? What does it do?

the nephron; produces and processes urine

What is at the head of the nephron?

the renal corpuscle

What are the two sub-elements of the renal corpuscle?

the glomerulus and Bowman’s capsule

How does urine begin forming and where does it occur?

pressure filtrate of plasma is excreted into the renal corpuscle

What word can describe the glomerular capillaries and what do they do?

fenestrated, they allow fluid to pass through into the renal corpuscle

What is the pathway of fluid through the renal corpuscle?

capillary wall → basement membrane (between capillary wall and capsule) → filtration slits made by podocytes

Where are podocytes found and what do they do?

in the visceral layer of the Bowman’s capsule and wrap around the glomerular capillaries to create filtration slits for fluid

Where does initial urine processing take place?

the proximal convoluted tubule

What mainly occurs during the initial urine processing in the proximal convoluted tubule?

reabsorption of glucose, A.A., urea, and some ions

What does the passage of partially processed filtrate into the loop of Henle produce?

a cortical-to-medullary conc. gradient

What is the purpose of the cortical-to-medullary conc. gradient?

it produces a concentrated urine in the loop of Henle

What does the loop of Henle consist of?

a descending limb and ascending limb

What are the different segments of the limbs in the loop of Henle and what are their characteristics?

thin segments → permeable to water, thick segments → less permeable to water

Where does the forming urine pass into after the loop of Henle?

the distal convoluted tubule (DCT)

What are the main tasks of the distal convoluted tubule (DCT)?

active and passive reabsorption of ions and the water which follows them

Where does the urine pass after going through the distal convoluted tubule (DCT)?

the collecting duct

Where does the collecting duct “dive” down through?

the kidney parenchyma from the cortical region into the medullary pyramid

What part of the kidney pathway establishes the conc. gradient?

the loop of Henle (cortical-to-medullary conc. gradient)

What does the conc. gradient from the mechanisms in the Loop cause?

water to be reabsorbed passively from the collecting duct back into the renal tissue

When are the collection ducts permeable to water?

in the presence of ADH

If the collection ducts are permeable to water, where does it move?

water moves osmotically from the forming urine in the collection duct out of the kidney tissues and back into circulation

If ADH is not present in the collecting duct, where will water be found?

the water will be found in the urine (as diluted, high-volume urine) because the collecting duct becomes impermeable to water. Without ADH, water cannot be reabsorbed into the bloodstream, leaving the filtered water inside the tubule

How does the kidney conserve and regulate water retention/loss?

through the presence or non-presence of ADH affecting whether water can move out or stay in the collecting ducts

What forces the blood through the filter of the glomerulus into the Bowman’s capsule?

the high BP

What absorbs water, glucose, and A.A. alongside other nutrients in the kidney?

the PCT

What part of the kidney is where water is reabsorbed?

descending limb

What part of the kidney is where solute is reabsorbed?

ascending limb

What part of the kidney “fine tunes” the filtrate?

the DCT

What part of the kidneys is where ADH acts and where urine is taken to the ureters and eventually the bladder?

the collecting duct

What are the 2 types of nephrons shown on the model?

cortical and juxtamedullary

Where do the renal corpuscles of the cortical nephrons lie?

the corpuscles are well out in the cortex

Where do the renal corpuscles and the loops of the juxtamedullar nephrons lie?

the corpuscles are right next to the cortical/medullar border and the loops lie deep in the medullary pyramid

How do the 2 types of nephrons differ?

in terms of their functions relative to water conservation

Full pathway of kidney vasculature

renal artery → branches over cortical-medullary boundary OR branches into arcuate arteries → interlobar arteries, afferent arterioles of the glomerulus, and capillary networks

What are the arcuate arteries?

a series of arches over each of the pyramidal regions of the kidneys stemming from the branches over the cortical-medullar boundary

What are the interlobar arteries?

branches from over the cortical-medullar boundary that travel the “thickness” of the kidney

What are the afferent arterioles of the glomerulus?

branches from the arcuate arteries that head “upward” into the cortex

What primarily occurs in the renal corpuscle?

the filtrate is formed, which is comprised of the earliest stages of urine formation

What is the glomerulus and what is it fed/drained by?

a bundle of capillaries in the renal corpuscle fed by an afferent arteriole and drained by an efferent arteriole

Which arteriole in the glomerulus has a larger diameter AND is more notably fenestrated?

the afferent arteriole

What does the fenestration of the arterioles in the glomerulus provide?

“filtration slits” through which water and small molecules can move from the circulation into the capsule but leave blood cells and proteins behind in the blood

Both the afferent and efferent arterioles are ___-_______ vessels and cause a _____ pressure drop

high resistance, large

What does the smaller efferent arteriole diameter maintain in the glomerular capillaries?

a high filtration pressure

How is the filtrate formed related to the fenestrated capillaries?

it is formed by the actual pushing out mechanism through the fenestrated capillaries before being collected in Bowman’s capsule

What does the distal tubule go past while moving the filtrate in the kidneys?

the macula densa cells of the juxstaglomerular apparatus

What is the function of the juxstaglomerular apparatus system?

monitors the final ionic composition of forming urine by modifying the filtration rate to compensate

Full pathway of fluid in the kidney

glomerulus → glomerular capillary wall→ basement membrane (between capillary wall and capsule) → Bowman’s capsule → filtration slits made by podocytes → proximal convoluted tubule (PCT) → loop of Henle (both descending and ascending limbs) → distal convoluted tubule (DCT) → collecting duct → kidney parenchyma → medullary pyramid