Anatomy Test 3 Urinary System II Lecture

What is one of the main functions of the kidneys?

to make any adjustment needed to maintain body fluid osmotic concentration at around 300 mOsm

What is osmolality?

number of solute particles in 1 kg of water

What is 1 osmol equal to?

1 mole of particle per kg of water

How much urine do the kidneys produce if the body is dehydrated?

small amounts

How much urine do the kidneys produce if the body is overhydrated?

body produces lots of diluted urine

How does the body accomplish this fluctuating urine/water system?

countercurrent mechanism

What is the countercurrent mechanism?

fluid flows in opposite directions in two adjacent segments of same tube with hairpin turn

What are the two types of countercurrent mechanisms?

countercurrent multiplier and countercurrent exchanger

What is the countercurrent multiplier?

interaction of filtrate flow in the ascending/descending limbs of nephron loops of juxtamedullary nephrons

What is the countercurrent exchanger?

blood flow in the ascending and descending limbs of vasa recta

What do these two countercurrent mechanisms work together to do what?

establish and maintain a medullary osmotic gradient

What is a kidney tubule?

functional part of kidney

What is the kidney interstitial?

everything that surrounds tubules

What countercurrent mechanism creates the gradient?

countercurrent multiplier (nephron loop)

What countercurrent mechanism preserves the gradient?

the countercurrent exchanger (vasa recta)

What countercurrent mechanism uses gradient to vary urine concentration?

collecting ducts

What nephrons create the gradient? (countercurrent multipliers

long nephron loops of juxtamedullary nephrons

What is the positive feedback cycle that uses the flow of fluid to multiply the power of salt pumps?

1. salt is pumped out of the ascending limb

2. interstitial fluid osmolality increases

3. water leaves the descending limb

4. osmolality of filtrate in descending limb increases

5. osmolality of filtrate entering the ascending limb

6. repeat

What does the vasa recta do to the gradient?

preserves the gradient

What is the vasa recta permeable to?

highly permeable to both water and solutes

How does the blood within the vasa recta relate to the surrounding fluid?

nearly isosmotic (bc permeable to both water and solutes)

What do the vasa recta act as?

countercurrent exchangers

If you're overhydrated, what happens to your ADH levels?

suppress ADH levels to decrease transcribed aquaporins to let water exit body

If you're dehydrated, what happens to your ADH levels?

lots of ADH and many aquaporins are transcribed, helping your body conserve water

What does the established medullary osmotic gradient do?

can be used to form dilute or concentrated uring

What does overhydration produce?

large volume of diluted urine (urine around 100 mOsm)

What does dehydration produce?

small volume of concentrated urine (around 1200 mOsm)

What are diuretics?

chemicals that enhance urinary output

What are examples of diuretics?

-ADH inhibitors, such as alcohol

-Na+ reabsorption inhibitors such as caffeine

What is urinalysis?

urine is examined for signs of disease or illegal substances

What is renal clearnace?

the clearance volume of plasma refers to the amount of plasma from which the kidneys can effectively remove a specific substance within a designated period

What are renal clearances used to determine?

GFR to help detect glomerular damage

What is chronic renal disease?

defined as GFR less than 60 mL per minute for 3+ months

What is renal failure?

defined as GFR < 15 mL per minute

What does renal failure cause?

uremia (ionic and hormonal imbalances)

What happens in the distal convoluted tubule?

cells respond to aldosterone (salt) and communicate with brain for blood vessel flow

What happens in the proximal convoluted tubule?

secretion and absorption

What is the chemical composition of urine?

95% water and 5% solutes

What are the solutes in urine?

nitrogenous wastes (urea, uric acid, creatine)

What else can be found in the blood?

abnormally high concentrations of any constituent or abnormal components such as blood proteins, WBCs, and bile pigments may indicate pathology

Why is it bad that proteins and cells are not filtered?

because they're supposed to stay in the blood plasma

What is the pigment in urine?

urochrome, from heme

What is the normal pH of urine?

usually 6

What are ureters?

slender tubes that convey urine from the kidneys to the bladder

Where on the spine do the ureters begin?

L2

Where do the ureters enter the bladder?

the base of bladder through posterior wall

What happens as bladder pressure increases?

distal ends of ureters close, preventing backflow of urine

What are the three layers of the ureter wall?

mucosa, muscularis, adventitia

What is the mucosa of the ureter wall?

transitional epithelium

What is the muscularis of the ureter wall?

smooth muscle sheets contract in response to stretch

What does the muscularis of the ureters do?

propels urine into bladder: gravity alone is not enough; must also be pushed by peristaltic wave action of smooth muscle

What does the transitional epithelium in the ureters and bladder function for?

ability to stretch to increased urine flow and storage

What is the function of the bladder?

muscular sac for temporary storage of urine

How is the male bladder different from the female bladder?

males have a prostate that lies inferior to the bladder neck, and females have no prostate

What is the trigone of the bladder?

a smooth triangular area outlined by openings for ureters and urethra (where ureters pierce bladder)

What are the layers of the bladder wall?

mucosa (transitional epithelial), muscularis (thick detrusor muscle), and adventitia (fibrous connective tissue)

What is thick detrusor found in the muscularis layer of the bladder?

smooth muscle bundles in multiple directions to make the muscle stronger

Is the muscularis of the bladder smooth or skeletal muscle?

smooth muscle

What is the urethra?

a muscular tube that drains the urinary bladder

What are the two sphincters of the urethra?

internal urethral sphincter and external urethral sphincter

What is the internal urethral sphincter?

involuntary (smooth muscle) at the bladder-urethra junction

Do we control the internal urethra sphincter?

no

What is the external urethral sphincter?

voluntary (skeletal) muscle surrounding urethra as it passes through the pelvic floor

What is the female urethra's external urethral orifice?

anterior to the vaginal opening

What are the three named regions of the male urethra?

prostatic urethra, membranous urethra, and spongy urethra

What is the prostatic urethra?

within the prostate

What is the membranous urethra?

passes through urogenital diaphragm from prostate to beginning of penis

What is the spongy urethra?

passes through the penis, opens via external urethral orifice

What is urination also called?

micturition or voiding

What ANS system controls contraction of the urethra?

parasympathetic enhances