renal system Flashcards
what are the two regions of a nephron?
renal corpuscle
renal tubule
what is the significance of protein in the urine?
consistent presence suggests glomerular of tubular damage
transient proteinuria quite common
can indicate a UTI
what is the chemical symbol for carbonic acid?
H2CO3
what are ketones, and what is indicated by their presence in the urine?
breakdown products of fat metabolism
they indicate the body has run out of glucose
ketones can be very high in diabetes; indicating an insulin deficiency
where is angiotensinogen produced?
the liver
what does RAAS stand for?
renin-angiotensin-aldosterone system
describe the nerve supply of the kidneys
sympathetic fibres regulate renal blood flow according to the body’s requirements
in kidney autoregulation, what mechanisms are used to increase glomerular blood pressure?
dilation of afferent arterioles
constriction of efferent arterioles
contraction of mesangial cells
what two types of water reabsorption occur in the kidneys?
what percentage does each account for?
obligatory 90%
facultative 10%
by what mechanism does the ANS control urination?
the micturition reflex
identify the organs of the urinary system
kidneys
ureters
urinary bladder
urethra
define micturition
the elimination of urine from the body
why don’t plasma proteins pass into the capsular space under normal circumstances?
plasma proteins are too large to pass through pores in glomerular capillaries
damage to which part of a nephron would interfere with hormonal control of blood pressure?
juxtaglomerular complex
describe the epithelium of the Bowman’s capsule
simple squamous epithelium
what are the forces involved in glomerular filtration?
- glomerular hydrostatic pressure
- capsular hydrostatic pressure
- colloid oncotic pressure
what’s the difference between reabsorption and secretion in the kidneys?
reabsorption: tubule → blood
secretion: blood → tubule
what is the functional unit of the kidneys?
the nephron
which parts of the urinary system make up the urinary tract
ureters
urinary bladder
urethra
trace the path of urine from the collecting duct to the urethra
collecting duct minor calyx major calyx renal pelvis ureter urinary bladder urethra
describe the urinary bladder’s muscle
detrusor muscle (smooth muscle)
contracts to expel urine
which three things regulate GFR?
autoregulation
hormonal regulation
autonomic regulation by sympathetic division of the ANS
what kind of epithelium lines the ureters?
transitional
what are the average GFRs for women and men?
women: 115 ml/min
men: 125 ml/min
what is the network of blood vessels surrounding the tubes of the nephron called?
the peritubular capillaries
what is the triangular area within the urinary bladder known as?
the trigone
what are the folds lining the surface of the empty urinary bladder known as?
rugae
what are the components of the renal corpuscle?
the glomerulus and the Bowman’s capsule (aka glomerular capsule)
describe the urethral sphincters
internal urethral sphincter - smooth muscle
external urethral sphincter - skeletal muscle (voluntary)
what is the part of the kidneys where urine collects before exiting via the ureter known as?
the renal pelvis
what are the three internal regions of the kidney?
cortex
medulla
renal pelvis
which artery carries blood to the kidneys for filtration?
the renal artery
where does most tubular secretion occur?
in the DCT (most) and the collecting duct
which segment of the nephron makes the final adjustments to the composition of tubular fluid?
the distal convoluted tubule
describe the epithelium in the thin part of the loop of Henle
simple squamous epithelium
what is filtrate?
the filtered liquid inside the tubes and loos of the nephron
what are the two types of nephron? which is more common?
cortical 85%
juxtamedullary 15%
what are the two special cell types of the juxtaglomerular apparatus/complex?
JG cells
macula densa
what is dysuria?
painful urination
what are the major functions of the renal system?
- regulation of blood volume and pressure
- regulation of blood pH
- regulation of ion concentrations
- nutrient regulation
- detoxification
describe the epithelium of the renal tubule
mainly cuboidal epithelium with microvilli
in which part of the kidneys is the blood filtered and substances selectively reabsorbed back into the blood?
the renal cortex
what gets secreted back into the filtrate from the blood?
drugs
potassium
hydrogen
wastes - creatine, urea, uric acid
how does tubular reabsorption occur?
by simple diffusion (passive)
by carrier proteins (passive or active)
what are the relevant numbers for glomerular filtration pressures?
NFP = 10 mmHg →
(net filtration pressure)
GHP ≈ 50 mm Hg →
(glomerular hydrostatic pressure)
BCOP ≈ 25 mm Hg ←
(blood colloid osmotic pressure)
CsHP ≈ 15 mmHg ←
(capsular hydrostatic pressure)
what are the three concentric layers of connective tissue around the kidneys?
inner to outer:
fibrous capsule (collagen)
perinephric fat capsule (adipose tissue)
renal fascia (dense, fibrous outer layer)
part of the nephron where water is reabsorbed back into the blood?
60-70% in the PCT
25% in nephron loop
the rest in the DCT and collecting tube
where and how does obilgatory absorption of water occur?
by osmosis in the PCT and nephron loop
glomerulus:
afferent arteriole
efferent arteriole
which is wider?
afferent arteriole
what is the papillary duct?
carries fluid from collecting ducts into the minor calyxes
the capsular space separates which layers of the glomerular complex?
parietal and visceral
in which part of the nephron are nutrients reabsorbed?
PCT
describe the layers of the filtration membrane in the glomerulus
filtration slits are formed by three layers:
- fenestrated epithelium of glomerular capillary
- basement membrane
- foot processes of podocyte cells from glomerular capsule
an increase in sodium and chloride in the peritubular fluid affects the descending limb in what way?
elevates osmotic concentrations around descending limb, results in water flow out of descending limb
where and how does facultative reabsorption of water occur?
mainly due to ADH in the DCT and collecting duct
can the permeability of the PCT or nephron loop chang?
what does this represent?
no. reabsorption of water occurs here whenever osmotic concentration of PCT/loop is lower than peritubular fluid.
this represents obligatory water reabsorption
where is the urinary bladder located?
in the pelvic cavity posterior to the pubic symphysis
why is BP higher in glomerular capillaries than systemic capillaries?
because of the different diameters of the afferent and efferent arterioles
what is the juxtaglomerular complex?
a cluster of specialised cells that secrete renin when glomerular BP falls
what occurs when the plasma concentration of a substance exceeds the kidney’s capacity for transporting that substance?
the excess is not reabsorbed, it’s secreted in the urine
what effect does an increase in ADH have on the DCT?
increased ADH = more aquaporins = more water reabsorbed
what is oliguria?
urinary output below 400-500 ml/day
what portions of the nephron are in the renal cortex?
renal corpuscle PCT DCT the proximal portion of the nephron loop the proximal portion of the collecting duct
how do the kidneys regulate blood pH?
they control the reabsorption or loss of both hydrogen ions (H+) and bicarbonate ions (HCO3-)
what is polyuria?
excessive urination
what is the importance of a consistent rate of glomerular filtration?
GFR too low = wastes can’t be excreted, fluid and pH are imbalanced
GFR too high = faster flow and less time for reabsorption, too much stuff lost in urine
what are the two ways we get fluid?
GI tract
cellular respiration
what is GFR?
the amount of filtrate produce each minute
ie mow much/how effectively we filter blood and produce urine
how is the concentration gradient of the renal medulla maintained?
by the removal of solutes and water from the area by the vasa recta
the nephron loop creates the gradient, the vasa recta maintains/stabilises it by redistributing reabsorbed water and solutes
what is the most important system in the regulation of systemic BP?
RAAS
the thick ascending limb of the nephron loop actively pumps what substances into the peritubular fluid?
what is it impermeable to?
sodium and chloride
it’s impermeable to water
what is anuria?
urinary output below 50 ml/day
in the PCT, ions and organic substrates are removed, causing what to occur?
a continuous osmotic flow of water out of the tubule
reduces volume of filtrate; keeps inside and outside of tubule isotonic
what are the three physiological processes performed by the kidneys?
filtration
reabsorption
secretion
when ADH levels in the DCT decrease, what happens to the urine osmotic concentration?
it becomes less concentrated
less ADH = less aquaporins = less water reabsorbed = less concentrated urine (and more of it)
a) renal corpuscle
b) renal capsule
c) glomerular capsule
do you know the difference?
a) initial portion of the nephron (glomerulus and glomerular capsule)
b) fibrous capsule covering the outer surface of the kidney
c) bowman’s capsule - what the filtrate lands in before the PCT
what is a creatinine clearance test used for?
to estimate GFR
what is uric acid?
a waste product formed during the recycling of RNA molecules
what is the presence of leukocytes in the urine called, and what is its significance?
pyuria.
indicates inflammation, often due to infection
pyuria + nitrites in urine = probable UTI
what effect would increased amounts of aldosterone have on the concentration of potassium in the urine?
what is the mechanism of this action?
increased K+ in urine as aldosterone leads to ↑Na+ and ↓K+ reabsorption at kidneys
(aldosterone stimulates Na+/K+ exchange pumps in DCT))
what do macula densa cells do?
sense ↓NaCl flow in DCT and release paracrine factors that affect the diameter of the afferent arteriole
(via the JG complex)
(↓NaCl = low flow)
what is creatinine?
waste product generated in skeletal muscle during muscle contraction
what is the significance of nitrite in the urine?
indicates infection
what is normal pH range for urine?
4.5 - 8
what might an alteration in urine pH signify?
what factor might affect variations within normal limits?
pH is altered in infections - can be higher or lower
within normal limits, pH will depend on diet, time of day
what is the significance of glucose in urine?
glycosuria may indicate diabetes
but temporary glycosuria may occur due to a larger meal, which may overload carrier molecules in nephron and cause excess glucose to be excreted in urine
