Urinary System Flashcards
Renal ptosis
kidneys drop
Floating kidney
suspensory collagen fibers break (Connective tissue
anchors the kidney and surrounding adipose to abdominal wall)
unilateral renal agenesis
some people (1 in 5000) born with only 1 kidney
Things that can cause kidney failure from kidney disease (unexpectedly…no before kidney failure):
High BP; damage small blood vessels in kidney
Diabetes; excess blood glucose leads to kidney vascular damage and micro and macroalbuminuria
Aspirin / acetaminophen / ibuprofen
Congenital problems; polycystic renal disease
Renal corpuscle
(glomerulus and Bowman’s capsule;
comprised of parietal and visceral layer) – filters the
blood (filtration); produces filtrate
Proximal convoluted tubule
returns good filtered substances to the blood (reabsorption)
Loop of Henle
helps conserve water and solutes (reabsorption of water)
Distal convoluted tubule
rids the body of additional wastes (secretion)
Collecting duct
carries urine from cortex toward renal papilla (water balance, can reabsorb water as needed)
parietal layer of the bowman’s capsule:
simple squamous epithelium on exterior of the capsule
Visceral layer of the bowman’s capsule:
podocytes, wrap around glomerular capillaries
Afferent arteriole
delivers unfiltered blood to the glomerulus. wider diameter vessel that leads into the glomerulus
Efferent arteriole
transports filtered blood away. blood that’s been filtered out through the glomerulus goes back into the bloodstream (stuff that needs to be reabsorbed from filtrate will happen later in the proximal convoluted tubule)
Mesangial Cells:
Supporting cells in the glomerulus (stationed between podocytes)
-specialized cells derived from smooth muscle
-Can phagocytize things
-Contain actin filaments: Can contract
-Respond to AngII, ADH
(May make renin?)
Glomerular capillary endothelium contains _____
basement membrane
fenestrated
Anuria
Low urine output
glomerular filtration rate (GFR)
The volume of filtrate formed by both kidneys per minute
Glomerular Filtration Membrane consists of:
- Glomerular capillary endothelium with fenestrae (deepest)
- Basement membrane
- Podocytes (visceral membrane of
Bowmans capsule)
glomerular hydrostatic pressure (GHP)
Forces water and dissolved solutes/ small particles
out into the glomerular capsule into the pericapsular
space (all but most plasma proteins, blood cells and
platelets; lose about 1% of albumin)
blood colloid osmotic pressure (BCOP)
tends to draw water out of the filtrate and into
the plasma; it thus opposes filtration
The net filtration pressure (NFP)
the net pressure acting across the glomerular
capillaries. It represents the sum of the
hydrostatic pressures and the colloid osmotic
pressures. Under normal circumstances, the
net filtration pressure is approximately 10 mm
Hg. This is the average pressure forcing water
and dissolved materials out of the glomerular
capillaries and into the capsular space.
GHP – (CHP + BCOP) = 55 – (15+30) = 10 mm Hg
(even small decreases in blood pressure at glomeruli can decrease GFR, if drops to 40 filtration stops and can cause acute renal failure)
Capsular hydrostatic pressure (CsHP)
force of filtrate fluid
against the wall of the capsule (= 15 mm Hg)
Melanuria
dark urine
Peritubular fluid
filtrate that has been reabsorbed into space around peritubular capillaries
Most tubular fluid is reabsorbed into peritubular space and referred to as peritubular fluid
Apical (luminal) membrane
faces tubule lumen
Basolateral membrane
often is
anchored to underlying
tissue/fascia; BUT in tubular
organs or structures in the
body this faces the interstitial
space / body cavity
Reabsorption
the process of
moving a substance from the
filtrate in the tubule lumen into
the peritubular fluid into the
peritubular capillary
Filtration
occurs in the glomerulus. Does NOT require energy. Driven by the differences in pressure
Afferent arteriole to glomerulus across podocyte into capsular fluid exits into tubule lumen
Reabsorption
substances in the lumen of the nephron can then be
reabsorbed across the apical membrane of the tubules – through the
cytosol – across the basolateral membrane into the interstitial fluid
and then into the peritubular capillaries to re-enter blood
Tubular fluid to peritubular fluid (interstitial fluid) into peritubular capillary
Secretion
The body can get rid of substances that are too large to be filtered by secreting them from the blood into the tubule lumen to be lost from the body in urine
Peritubular capillary into peritubular fluid into the tubule lumen
Excretion
Elimination of wastes from the body
Tubule fluid into collecting duct, into ureters, into bladder, into urethra, out the body
Glucose is absorbed in the PCT by a ____
sodium-glucose co-transporter
pyel
trough or pelvis
What cells are found in the collecting duct?
Principal cell: main sodium reabsorbing cells (influenced by hormones–ADH)
Intercalated cell: cells that mediate secretion and bicarbonate reabsorption
What cells are found in the papillary duct (duct from collecting ducts to minor calyces)?
columnar cells (Hormones influence permeability of papillary duct)
Facultative (optional) water reabsorption (10-15% of water reabsorption) – occurs
in ____ and ___.
Without ____ epithelium is impermeable to water.
With ____ epithelium is permeable to water, make ____ urine and ____ water.
DCT and collecting tubules; ADH
ADH; concentrated; conserve
Three metabolic wastes:
Urea (most abundant organic waste, most from
breakdown of amino acids, produce ~21 g/d)
Creatinine (from breakdown of creatine phosphate in
skeletal muscle, make ~1.8 g/d, all excreted in urine)
Uric acid (from recycling of nitrogenous bases from
RNA, make ~480 mg/d)
Juxtaglomerular Apparatus (JGA) components:
Juxtaglomerular (JG) cells, macula densa, and (extraglomerular) mesangial cells
Juxtaglomerular (JG) cells
Enlarged, smooth muscle cells in walls of afferent arteriole
Act as mechanoreceptors
Macula densa
Tall, closely packed distal tubule cells
Lie adjacent to JG cells
Function as chemoreceptors / osmoreceptors
Mesangial cells (extraglomerular, part of the JGA):
Have phagocytic and contractile properties
Influence capillary filtration
Vasopressin / Angiotensin II affect mesangial cell contraction
RAAS
renin-angiotensin-aldosterone-system
JG cells surrounding afferent arterioles make
____ (enzyme) –
_____ converts ______ into
________ (inactive precursor)
_______ is then converted into
________ (hormone) by _______ (ACE)
ACE is richly expressed in the capillaries
of the lungs and is found in the kidney
Renin
Renin; angiotensinogen; Angiotensin I
Angiotensin I; Angiotensin II; angiotensin
converting enzyme
Angiotensin II
systemic vasoconstriction, stimulates aldosterone (salt) and ADH (water) production. Works on proximal convoluted tubule.
most vasoactive
Has a direct effect on the PCT to increase Na reabsorption
Increases GFR by increasing renal perfusion pressure
Constricts systemic blood vessels (arteriolar vasoconstriction)
Stimulates aldosterone production from adrenal glands
Stimulates posterior pituitary to make ADH (water reabsorption from collecting tubule)
More Na and Cl reabsorption from nephron, more K+ secretion into nephron tubule
Stimulates sympathetic activity
Blood volume increases, BP goes up, GFR goes up
Aldosterone
salt retention in distal tubule and collecting duct (principle cells). produced by adrenal cortex. stimulated by angiotensin II and stretch receptors in heart and low sodium.
Synthesis from adrenal cortex (mineralocorticoid from zona glomerulosa)
Increases Na and Cl reabsorption and K excretion; leads to water retention
Works on distal kidney tubules, principal cells of collecting duct
Steroid hormone
Synthesized by adrenal cortex; acts on the kidney
Is a mineralocorticoid
Role is to increase BP - by conserving sodium, secreting potassium and increases blood pressure
Synthesis stimulated by angiotensin II, ACTH and potassium levels (all of these increase when sodium deficient) and by plasma acidosis
Stretch receptors in the heart also sense decreased BP and stimulate adrenal gland to release aldosterone
Acts on distal tubule and collecting duct -principal cells
Antidiuretic Hormone (ADH) = Vasopressin
water reabsorption, posterior pituitary, in response to angiotensin II or high osmolality (solute content in blood)
Increases water reabsorption in collecting duct and DCT – by stimulating aquaporin production in apical membrane
Released by posterior pituitary in response to increased osmolality of plasma or stimulation by Angiotensin II
Is a neurohypophyseal hormone
Role is to increase BP - by conserving water and constricting blood vessels
nInduces aquaporin translocation into apical membranes in collecting duct and distal convoluted tubule
Erythropoietin (EPO)–
Synthesized by the JG cells in response to Hypoxia
Increases RBC production in the bone marrow
More RBC more capacity to transport oxygen
Calcitriol (1,25(OH)2D)
Synthesized in the PCT
25(OH)D-DBP taken into PCT cell by megalin / cubulin receptor(receptor mediated endocytosis)
25(OH)D can be used inside the cell to make calcitriol because 1-alpha hydroxylase enzyme (CYP27B1 gene) is present in the PCT
If calcitriol is not needed, 25(OH)D can by hydroxylated at the 24-position by 24-hydroxylase in the PCT (CYP24A1 gene)
Atrial natriuretic peptide and brain
natriuretic peptide
Synthesized by cardiac cells in
response to increased blood volume or increased blood pressure
Work to reduce fluid volume by inhibiting ADH (lose more fluid, reduce plasma volume, less concentrated urine)
Reduce thirst so not taking in fluid
Cause peripheral vasodilation (lower BP, reduce GFR)
What are the 2 most common health
problems that lead to CKD?
Hypertension
Diabetes
Less than 2% of older patients with CKD
require renal replacement therapy – why?
Die from cardiovascular disease
What changes that occur with CKD
increase the risk of heart failure?
Can’t maintain fluid balance – heart
must pump larger amount of fluid that
the kidneys cannot get rid of
As heart fails there is reduced blood
flow to kidneys so their ability to
function decreases
List 3 biochemical findings that could be
used to provide evidence of altered renal
function in those with CKD?
- Proteinuria
- Micro and macroalbuminuria
- Elevated serum creatinine
- Reduced glomerular filtration rate (rate at
which the kidney filters the blood) - Alterations in serum metabolites
- Elevated cystatin C – newer test
elevated Cystatin C blood test may be a good marker of GFR bc
-filtered only by glomerulus
-not secreted by renal tubules
-generated at a consistent rate by all cells in the body
What 2 hormones can the body use to regulate P homeostasis and where are
these made?
FGF23 - osteocyte / PTH – parathyroid glands
What does high P do to increase risk of cardiac disease?
High serum P associated with vascular calcification, get arterial stiffness, can narrow the lumen of the arteries. High P stimulates vascular smooth muscle cells to undergo osteochondrogenic differentiation and calcify
Link between vascular calcification and osteogenesis; regulators of bone formation in vascular plaques
What 2 hormones may explain the
anemia that is found in those with CKD and
where are these hormones produced?
What are some of the non-hormonal
reasons for this anemia?
Erythropoietin (EPO) – made in kidney
Hepcidin – made in liver from inflammation caused by CKD
Fe deficiency anemia
Blood loss from dialysis
Decreased RBC half-life
How can anemia be treated
according to the article issues of iron
management in the hemodialysis
patient?
Intravenous iron, bypass the gut
Average dose of Fe 914 mg a month IV
Typically absorb 1-2 mg Fe/d = 30-60 mg per month
What form of Fe would be
found in the blood in those with
iron overload?
What tissues are most at risk?
NTBI: non-transferrin bound iron (free floating serum iron); taken up by ZIP14
pancreas and liver
FGF23 from osteocyte:
*Increases from high P
*Inhibits P absorption from gut
*Inhibits P reabsorption from kidney
*Inhibits PTH release
*Inhibits 1-alpha hydroxylase in kidney
Calcitriol from kidney:
*Increased by PTH- low Ca
*Decreased by high P
*Increases bone resorption
*Inc Ca/P absorption gut
*Inhibit PTH secretion
*Stimulate FGF23 production
PTH from 4 PTH glands:
*Increases from low Ca/ high P
*Increases calcitriol production kidney
*Inhibits P reabsorption from kidney
*Increases Ca reabsorption from kidney
*Increases Ca/P release from bone
