What are the major functions of the kidney?
filter 200 liters of blood dailyregulate volume and chemical
makeup of the bloodmaintain the proper balance between water and
salts, and acids and bases
What are some other renal functions?
Gluconeogenesis (generation of glucose) during prolonged
fastingProduction of renin to help regulate BP and
erythropoietin to stimulate RBC productionActivation of vitamin
D - metabolize Vit D to its active form (Vit D3 form = calcitriol)
What are the major nitrogenous wastes?
UreaUric AcidCreatinine
What is normal levels of blood urea nitrogen (BUN)?
6-18 mg/dl
What is Azotemia?
Abnormally elevated BUN (possible renal insufficiency)
What is Uremia?
Severe azotemia-diarrhea, vomiting, dyspnea (labored
breathing), convulsions, coma and death
What is the renal capsule?
fibrous capsule that prevents kidney infection
What is the adipose capsule?
Fatty mass that cushions the kidney and helps attach it to the body wall
What is the renal fascia?
outer layer of dense fibrous connective tissue that anchors the kidney
What do the paired ureters do?
transport urine from the kidneys to the bladder
What is the main function of the urinary bladder?
provides a temporary storage reservoir for urine
True or False?The ureter transports urine from the bladder out
of the body.
False; the urethra transports urine from the bladder out of the body
What are the major calyces and what do they do?
large branches of the renal pelvis
-collect urine draining from papillae
-empty urine into the pelvis
True or False?
Urine flows through the pelvis and ureters to the bladder.
TRUE
Approximately how much of systemic cardiac output flows through the
kidneys each minute?
one-fourth (1200ml)
What is the functional unit of the kidney?
nephron
What is the nephron responsible for?
forming urine
Approximately how many nephrons are in each kidney?
1.2 million nephrons per kidney
What are the two parts of the nephron and what are they responsible for?
1. renal corpuscle - blood filtration
2. renal tubule - processes filtrate into urine
What is glomerular endothelium?
fenestrated epithelium that allows solute-rich, virtually
protein-free filtrate to pass from the blood into the glomerular capsule
What is the proximal convoluted tubule (PCT) do?
reabsorbs water and solutes from filtrate and secretes substances
into it
True or False?
The distal convoluted tubule (DCT) functions more in reabsorption
than secretion.
False; DCT functions more in secretion that reabsorption
What are the two more important cell types in the connecting tubules
and what is their main function?
1. intercalated cells - function in maintaining the acid-base balance
of the body
2. principal cells - help maintain the body's water and salt balance
What type of nephrons makeup about 85% of nephrons and have a general
function of ultrafiltration?
cortical nephrons
What kind of nephrons are involved in the production of concentrated urine?
Juxtamedullary nephrons
True or False?
Every nephrons has 3 capillary beds.
False; every nephron has 2 capillary beds
What are the two capillary beds in every nephron?
glomerulus and vasa recta
Where is the vasa recta capillary network?
branch off the efferent arterioles of juxtamedullary nephrons (those
closest to the medulla), enter the medulla, and surround the loop of Henle.
True or False?
The kidneys filter the body's entire plasma volume 120 times each day.
False; the kidneys filter the body's entire plasma volume 60 times
each day.
What is contained in the filtrate?
all plasma components EXCEPT PROTEIN
What does the filtrate lose in order to become urine?
water, nutrients, and essential ions
What is contained in urine?
metabolic wastes and unneeded substances
What are the three major processes involved in urine formation and
the adjustments of blood composition?
glomerular filtration
tubular reabsorption
secretion
What is the Net Filtration Pressure (NFP)?
The pressure responsible for the filtrate formation
What is the NFP equation?
NFP = HP (hydrostatic pressure) - [COP (glomerular blood pressure) +
HP (capsular hydrostatic pressure)]
What are the levels of BHP, COP, and CP during glomerular filtration?
BHP (blood hydrostatic pressure) - 55 mmHg out
COP (colloid osmotic pressure) - 30 mmHg in
CP (capsular pressure) - 15 mmHg in
NFP - 10 mmHg out
True or False?
The afferent arteriole is larger than the efferent to create less
pressure to create more filtrate.
False; the afferent arteriole is larger than the efferent to create
less pressure to create more filtrate
True or False?
Caffeine dilates the afferent arteriole, causing more urination.
TRUE
What is another word for urination?
mituation
What is the average glomerular filtration rate (GFR) for both kidneys?
125 ml/min
What is the equation for GFR?
GFR = NFP x Kf (constant of 12.5 ml/min)
What is glomerular filtration rate (GFR)?
the volume of filtrate produced by both kidneys/min
What is the average GFR in women?
In men?
Women - 115 ml/min
Men - 125 ml/min
Totals about 180 L/day (45 gallons)
True or False?
Most filtered water must be reabsorbed or death would ensue from
water loss through urination?
TRUE
What happens if the GFR is too high?
needed substances cannot be reabsorbed quickly enough and are lost in
the urine
What happens if the GFR is too low?
everything is reabsorbed, including wastes that are normally disposed of
What two types of control regulate glomerular filtration rate?
intrinsic and extrinsic control
What is the mechanism for intrinsic control?
renal autoregulation
What are the two mechanisms for extrinsic control?
1. neural controls
2. hormonal mechanism (the renin-angiotensin system; antidiuretic hormone)
What is the 1st intrinsic control?
myogenic - smooth muscle - it recoils/contracts when it is stretched/dilated
increased BP causes contraction of the afferent arteriole; restricts
flow to the glomerulus and prevents rising pressure/damage in the glomerulus
What is the 2nd intrinsic control?
flow-dependent tubuglomerular feedback
senses changes in the juxtaglomerular apparatus
What are the granular cells?
juxtaglomerular cells
in the afferent arteriole; smooth muscle; as these contract the
diameter of the afferent arteriole decreases; have secretory granules
containing renin; act as mechanoreceptors
What do the macula densa cells make up?
the walls of the distal convoluted tubules as it touches the capsule
act as chemoreceptors or osmoreceptors
What do mesanglial cells do?
have phagocytic and contractile properties
influence capillary filtration
How do the macula densa cells influence GFR?
Macula densa cells are chemoreceptors and detect NaCl levels in the
distal convoluted tubule filtrate. If the GFR is too high, these cells
cannot detect and absorb NaCl effectively so the levels of NaCl in the
tube itself will be too high. If there is a high level of NaCl in the
tube, these cells will send inflammation signals to the JG cells to
contract to decrease GFR (tubuloglomerular feedback)
What are JG cells stimulated by?
can constrict on their own based on physiology but can also be
stimulated by the central nervous system as well as the sympathetic
nerve fiber (in cases of stress)
What happens when BP increases significantly?
the renin-angiotensin mechanism is activated - renin acts on
angiotensin to release angiotensin I (inactive molecule) - then
converted to angiotensin II (active molecule) by ACE (produced by type
I epithelial cells) - angiotensin II causes mean arterial pressure to
rise and stimulates the adrenal cortex to release aldosterone
What is renin release triggered by?
reduced stretch of the granular JG cells, stimulation of the JG cells
by activates macula densa cells, direct stimulation of the JG cells
via beta 1 adrenergic receptors by renal nerves (SNS), and angiotensin
II which causes constriction of efferent arteriole
How does renin-angiotensin-aldosterone mechanism work?
drop in BP, JG cells release renin, angiotensinogen is released from
the liver, combines with renin to make angiotensin I, converted to
angiotensin II with ACE from the lungs, goes to the hypothalamus which
increases thirst and drinking and also goes to the adrenal cortex
where aldosterone gets released and tells the kidneys to pick up more
sodium chloride which creates more salt and water retention and
elevates BP, angiotensin II also causes vasoconstriction which will
help to elevate BP (slide 49)
What effects does angiotensin II have on urine?
causes constriction of efferent arteriole - increases glomerular BP
and filtration and reduces BP in peritubular capillary - reduces
resistance to tubular reabsorption - tubular reabsorption increases -
urine volume is less but concentration is high