Renal System Flashcards
What are the structures of the urinary system?
- kidney
- ureters
- bladder
- urethra
Contrast contents of male and female urethra
- male: urine + sperm
- female: urine ONLY (shorter and so easier to get UTIs)
Bladder function
store urine
- What are the two urethral/ bladder sphincters?
- What type of muscle are they?
- How are they controlled?
- internal urethral sphincter- smooth m. under involuntary unconscious control (normally sympathetic NS keeps sphincter constricted to NOT let out urine)(when parasympathetics activate detrusor to contract to start urinating, it also causes sympathetic inhibition, which relaxes IUS)
- external urethral sphincter- skeletal m. under voluntary conscious control. (somatic NS)
both have to be RELAXED for micturition aka voiding aka urination
What part of kidney (medulla or cortex) does most filtration of blood occur?
renal cortex
bc nephron filtering units mainly are here
What part of the kidney (cortex or medulla) is the site of EPO production?
renal cortex
Renal medulla general function
has tubules of the nephron that reabsorb (as well as secrete) substances and concentrates urine
The renal artery brings [____] blood to the kidneys from the [_____]
- oxygenated
- abdominal aorta
The renal [_____] brings [____] blood to the heart
- vein
- filtered deoxygenated
What is the site of filtration?
renal corpuscle = glomerulus + bownman (aka glomerular) capsule
What is the structural and functional unit of the kidney?
the nephrons (bowman’s capsule + tubules)
What is the general blood flow once we get to AA of the kidney’s?
AA brings blood to be filtered to the glomerulus –> filtration occurs in the glomerulus into bowman’s capsule –> 2 paths (1. filtrate moves through PCT, thin descending loop of henle, thick ascending loop of henle, early DCT, late DCT, and the collecting duct –> renal pelvis –> ureter –> bladder –> urethra) (2. some substances go directly through glomerulus and into the EA –> peritubular capillaries (invovled in reabsoprtion and secretion) –> interlobular vein –> arcuate vein –> interlobar vein –> renal vein –> inferior vena cava)
Constriction and dilation of the [___] and [___] control the GFR
- AA
- EA
The consistent [__] pressure in the glomerular capillaries allows for filtration to occur in the glomerulus
high
note: this pressure is maintained by general body arterial pressure as well as AA being always more so dilated (so increase pressure downstream) and EA being more so constricted (so increase pressure upstream)
- What is the capillary within the nephron?
- What part of the kidney (cortex or medulla) is it located?
- What does this capillary do?
- glomerulus
- renal cortex
- filters blood out of the AA INTO bowman’s capsule through blood pressure.
The nephron tubules are surrounded by [___] where substances are [____] back into the capillaries OR [___] into the nephron tubules
- peritubular capillaries
- reabsorbed
- secreted
What are considered the nephron filtrating units?
Where are these located?
glomerulus
located in renal cortex
What are the parts of the nephron invovled in the reabsorption and secretion of substances?
Where are these mainly located?
tubules
in renal medulla (mainly)
How is the kidney able to filter blood?
good blood pressure is maintained throughout body and so at glomerular capillaries to push fluid from the capillaries into bowman’s space
What is ALWAYS freely filtered?
- water and salt
- small organic mlcs: AA, glucose, metabolic nitrogenous waste, electrolytes (Na, K, Ca, Mg), urobilin (makes pee yellow- remnant from bilirubin from way back RBC breakdown), H+/ HCO3-
When substance enters from the glomerular capillaries into bowman’s space, what is it called?
filtrate (NOT final urine)
filtrate has to undergo absorption and secretion to become final urine
What are items that should NEVER be able to be filtered through glomerular capillaries filtration barrier into tubules and so should NEVER be in the final urine?
RBC, WBC, platelets, plasma proteins (ie. albumin, fibrinogen, angiotensin, hormones like insulin)
What are 2 items that ARE freely filtered through glomerular capillaries BUT SHOULD NOT be in the final urine
glucose and amino acids
these should be completely reabsorbed in PCT
What does glucose in the urine mean?
- DM or other kidney issues (too much glucose in blood exceeds transport max in PCT leading to leaking of glucose into the urine)
What does proteins, AA in urine mean?
nephrotic syndrome
What is tubular
* reabsorption?
* secretion?
- reabsorption: helps to concentrate urine; reabsorption of items BACK INTO BLOOD STREAM (into peritubular capillaries first)
- secretion: items FROM peritubular capillaries INTO the renal tubule to be excreted
PCT
* What is secreted?
* What is reabsorbed?
- secreted: H+, creatinine (100% secretion- the rest of it that wasn’t filtered out at time of glomerular capillaries), ammonium, drugs, toxins
- reabsorbed: MAIN SITE OF REABSORPTION: 100% of glucose and AA, 80% of ions [Na, Cl, K, Ca, Mg] and 80% water, bicarb, vitamins, phosphate, urea
What value is a good measurement of renal function?
creatinine clearance bc it should equal GFR (100 mL/ min)- the creatinine that is NOT filtered into bowman capsule from first pass in glomerular capillaries should be ALL secreted into the tube at the PCT.
thin descending loop of henle
* What is secreted?
* What is reabsorbed?
- secreted: urea
- reabsorbed: water through osmosis (passive transport)- following the bunch of solutes that were just reabsorbed in PCT = concentrates urine
The urea reabsorbed in the medullary collecting ducts and secreted in the thin descending loop of henle aid in the osmotic gradient to promote max water reabsorption from filtrate to ultimately concentrate the urine
Purpose of the nephron
- concentrate the filtrate through reabsorb as many solutes and water as can and production of urine
Permeability of nephron segments to water
permeability to water is really permeability to water REabsorbtion
* always water permeable: PCT, thin descending loop of henle (passive transport- osmosis)= concentrates urine
* always water IMpermeable: thic ascending loop of hendle and the early DCT = DILUTES urine.
* variable water permeability based on ADH: late DCT and collecting duct= last leg of concentration of urine.
Aldosterone function
increases number of Na/K ATPase’s on basal membrane and increases number of ENAc (Na channels) and K+ channels and H+ ATPase on apical membrane to increase Na reabsorption (and so water reabsorption) and K+ secretion in the late DCT and CT.
ADH function
inserts aquaporin channels on apical membrane to increase water reabsorption from late DCT and CT.
aka vasopressin
thicc ascending loop of henle
* What is secreted?
* What is reabsorbed?
- secreted: nothing
- reabsorbed: Na/Cl/K, Mg and Ca paracellularly
- impermeability to water = dilutes urine
DCT (early and late)
* What is secreted?
* What is reabsorbed?
- secreted: K+ , H+
- reabsorbed: Cl, Ca, Na (water is ONLY reabsorbed in the LATE DCT and is under the control of ADH, and Na reabsorption in LATE DCT is also under aldosterone control)
Ca reabsorption is increased also by PTH
Collecting duct aka collecting tube
* What is secreted?
* What is reabsorbed?
- secreted: K+/ H+
- reabsorbed: urea, bicarb, Na (dependent on aldoesterone), water (dependent on ADH)
What should final urine mainly consist of?
- water, salts, urea, creatinine, etc..
What should final healthy urine never have?
glucose, AA [ bc even though freely filtered at glomerulus , should be 100% reabsorbed in the PCT]
plasma proteins (ie. albumin, fibrinogen, angiotensin, hormones), WBCs, RBCs, platelets [ bc should NEVER be filtered through the glomerulus in the first place]
What are the functions of the kidneys?
A-acid base (pH) balance thru H secretion and HCO3- reabsorption to maintain pH b/w 7.35 and 7.45
W-ater (fluid) balance
E- ryhtropoiesis through kidney’s cortex making EPO to send to red bone marrow to stimulate RBC production
T-oxin removal: filters metabolic nitrogenous waste from the blood to be excreted into the urine (urea from protein metabolism, uric acid from nucleic acid metabolism, and creatinine from muscle creatine catabolism aka byproduct of quick ATP); modifying and deactivating meds (liver also does this)
B-lood pressure control through fluid (water) and salt balance and RAAS
E- lectrolyte (Na, Cl, K, Ca, Mg) balance
D- active form of vitamin D (calcitrol) synthesis (with OR WITHOUT aid of PTH; with PTH is bc PTH stimulates Ca absorption from intestines and that REQUIRES active Vit D)
What contributes to filtration of blood at the glomerulus?
blood pressure
Go over RAAS system
in ipad under cardiovascular
How is the RAAS system activated?
through decrease in arterial pressure and low blood volume sensed by the juxtaglomerular apparatus inside the kidneys
- What is secreted by the kidney’s when there is a drop in arterial pressure or low blood volume?
- What secretes this substance?
- renin to launch RAAS to increase BP
- granular aka juxtaglomerular cells of the AA of the kidney’s
What is the juxtaglomerular apparatus?
- macula densa of end of thic ascending loop of henle/ start of DCT, extraglomerular mesangial cells, juxtaglomerular cells of AA
What are the intrarenal baroreceptors?
- granular cells aka juxtaglomerular cells of the AA
Explain the steps of urine flow
- renal arteries bring blood to the neprhons (AA brings blood into glomerulus)
- blood is filtered in the glomerulus –> filtrate (all while EA eventually drains into IVC and brings blood back to body)
- filtrate flows through nephron tubules (things are reabsorbed and secreted)
- Collecting tube
- renal papillae
- renal calyx (minor –> major calyx)
- renal pelvix (collects urine)
- ureters
- bladder
- urethra
micturition reflex
- urination and voiding
- detrusor m. stretches –> afferents to sacral spinal cord –> parasympathetic NS efferents stimulate detrusor smooth m and contracts it, all the while causes sympathetic inhibition to the internal urethral sphincter (smooth m.) that detrusor is connected to , leading to it relaxing, and at the same time, the **external urethral sphincter **(skeletal m.) voluntarily relaxes –> urination.
Where in the nephron does reabsorbtion and secretion/excretion take place?
tubules (and peritublar capillaries)
in the renal medulla
