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37 Cards in this Set
- Front
- Back
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Functions of the Urinary System
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• Alters blood composition, pH,
volume, pressure • Maintains blood Osmolarity • Excretes wastes & foreign substances • Produces hormones • System consists of: 2 kidneys 2 ureters 1 urinary bladder 1 urethra |
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Functions of the Kidneys
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• Regulation of blood ionic
composition • Regulation of blood pH • Regulation of blood volume • Regulation of blood pressure • Regulation of blood glucose level • Maintenance of blood osmolarity • Production of hormones • Excretion of wastes & foreign substances |
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External Anatomy of the Kidneys
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- concave medial border with renal
hilum - 3 tissue layers around kidney: • renal capsule (deep) • adipose capsule • renal fascia (superficial) |
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Internal Anatomy of the Kidneys
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- renal cortex (superficial)
• renal columns - renal medulla (deep) • renal pyramids - renal lobe = pyramid + overlying cortex + ½ of each adjacen column - parenchyma = cortex + pyramid = functional part of kidney • nephron—functional unit of kidney; 1 million per kidney • urine flows from nephron --> collecting duct--> papillary ducts --> minor/major calyces --> renal pelvis --> ureter --> bladder - renal sinus •part of renal pelvis, calyces, & branches of blood vessels/nerves |
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Blood & Nerve Supply of the Kidneys
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- kidneys compose 0.5% of total
body mass, but receive 20-25% of cardiac output - renal artery --> afferent arteriole --> glomerulus --> efferent --> arteriole - glomerulus • capillary network formed from 1 afferent arteriole per nephron - peritubular capillaries • surround tubular parts of nephron in cortex - vasa recta (longer pertubular capill) • long, loop-shaped capillaries extend from some efferent arterioles • supply tubular portions of nephrons in medulla - peritubular venules --> renal vein - renal ganglion & renal plexus • sympathetic nervous system; mostly vasomotor nerves |
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Flow of Filtrate thru a Nephron
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Filtrate thru...
Glomerulus into Bowman's Capsule in Cortex --> to Renal Tubule --> PCT --> loop of Henle (descending limb) --> Loop of Henle (ascending limb) --> DCT --> Collecting Duct Then... dumps into (CD) & then called URINE! |
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Parts of a Nephron
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• renal corpuscle
- Glomerulus & Glomerular (Bowman’s) capsule in cortex • renal tubule - proximal convoluted tubule (PCT) in cortex - Loop of Henle (nephron loop; descending & ascending limbs) in cortex & medulla - Distal convoluted tubule (DCT) in cortex |
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Types of Nephrons
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• Cortical nephrons (80-85%)
- renal corpuscles in outer part of cortex; - have short loop of Henle mainly in cortex; just dips into medulla • Juxtamedullary nephrons (15-20%) - renal corpuscles lie deep in cortex (close to medulla); - have long loop of Henle that extends into deepest region of medulla; - Loop of Henle as thin & thick ascending limbs |
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Histology of Nephron
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• Glomerular capsule
(simple squamous) - visceral & parietal layers with space inbetween - visceral layer has modified simple squamous cells called Podocytes that have pedicels (little feet that wrap around) |
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Histology of Collecting Duct
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• Renal tubule & Collecting duct
- PCT—simple cuboidal with brush border - Loop of Henle (descending limb & 1st part of ascending) —simple squamous - Loop of Henle (rest of ascend limb) -simple cuboidal to low columnar - Juxtaglomerular apparatus —where end of ascending limb (macula densa) contacts afferent arteriole (modified smooth muscle cells = juxtaglomerular cells) - DCT—mostly principal cells (with receptors for ADH & aldosterone) - CD--simple columnar epithelium |
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3 Stages of Renal Physiology
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1) Glomerular Filtration
- water & most solutes in blood plasma move into glomerular capsule --> renal tubule 2) Tubular Reabsorption - 99% of water is reabsorbed as well as many solutes - return to blood as it flows through peritubular capillaries & vasa recta 3) Tubular Secretion - wastes, drugs, & excess ions secreted by tubular & duct cells into fluid; substances removed from blood |
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Glomerular Filtration
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Glomerular filtrate—
fluid that enters capsular space Filtration fraction— fraction of blood plasma in afferent arterioles that becomes glomerular filtrate (16-20% is typical) |
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Glomerular Filt:
The Filtration Membrane |
- filtration membrane
= endothelial cells of glomerular capsule + podocytes of visceral layer; 0.1μm thick • allows filtration of water & small solutes; -prevents filtration of plasma proteins, blood cells, & platelets |
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3 Barriers of Filtration Membrane
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1) Glomerular endothelial cells
(with fenestrations) 2) Basal lamina 3) Filtration slits (formed by pedicels of podocytes) |
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Filtration Membrane Details
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- volume of fluid filtered by renal
corpuscles is much larger than in other capillaries of the body because… • glomerular capillaries have a large surface area • filtration membrane is thin & porous • blood pressure in glomerular capsule is high (efferent arteriole is smaller than afferent arteriole) |
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Net Filtration Pressure (NFP):
- Pressure that promotes Filtration GBHP |
Glomerular blood hydrostatic
Pressure (GBHP): • blood pressure in glomerular capillaries; ~55mm Hg • promotes filtration (Positive, forces H2O thru slits) |
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NFP:
CHP |
Capsular hydrostaticpressure (CHP)
• pressure against filtration membrane by fluid already in capsular space & renal tubule; ~15mm Hg • opposes filtration |
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NFP:
BCOP |
Blood colloid osmotic pressure (BCOP):
• due to presence of proteins in blood plasma; ~30mm Hg • opposes filtration -(part suspended in blood slows filtration) |
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NFP (Equation)
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NFP= GBHP - CHP - BCOP
NFP= (55+) - 15 - 30= 10mmHg Pressure |
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Glomerular Filtration Rate (GFR)
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- GFR =
amount of filtrate formed in all renal corpuscles per min (125mL/min for avg male; 105mL/min for avg female) - regulated by: (1) adjusting blood flow into/out of glomerulus & (2) altering glomerular capsule surface area -Arterioles dilate O=GFR SLOWER -b/c blood has more space to flow -Arterioles constrict o=FASTER GFr |
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3 mechanisms of regulation
(Table 26.2) |
• renal autoregulation
- myogenic mechanism - tubuloglomerular feedback • neural regulation - sympathetic autonomic nervous system (NE) • hormonal regulation - angiotensin (decreases GFR) - atrial natriuretic peptide (increases GFR) **Kidneys can regulate selves, but NS & Endocrine syst can work together for homeostatic regulation* |
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Principles of Tubular
Reabsorption & Secretion |
- PCT contributes the most to
reabsorption - Reabsorbed substances --> water, glucose, amino acids, urea, Na+, K+, Ca2+, Cl-, HCO3- ,HPO4(2-) - Secreted substances --> H+, K+, NH4+, creatinine, drugs |
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Reabsorption & Secretion in the
Proximal Convoluted Tubule |
- largest amount of solute & water
reabsorption from filtrate • 65% of water, Na+, K+ • 100% of organic solutes (glucose, amino acids) • 50% of Cl- • 80-90% of HCO3- • 50% of urea (liver converts toxic ammonia -> Urea) • variable amount of Ca2+, Mg2+, HPO4 (2-) - secrete variable amounts of H+, NH4+, urea - solute reabsorption in PCT promotes osmosis |
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Reabsorption in the Loop of Henle
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- reabsorbs…
• 15% of water in descending limb, 0% in ascending limb • 20-30% of Na+, K+ • 35% of Cl- • 10-20% of HCO3- • variable amount of Ca2+, Mg2+ - reabsorption of water via osmosis is not automatically coupled to reabsorption of solutes • part of loop is relatively impermeable to water; leads to independent regulation of volume & osmolarity of body fluids |
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Reabsorption in the Early Distal
Convoluted Tubule |
- reabsorbs…
• 10-15% of water • 5% of Na+ • 5% of Cl- - major site where PTH stimulates reabsorption of Ca2+ |
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Reabsorption & Secretion
in the Late Distal Convoluted Tubule & Collecting Duct |
- principal cells reabsorb Na+ &
secrete K+ - intercalated cells reabsorb K+ & HCO3-, and secrete H+ - amount of water & solute reabsorption and amount of solute secretion, vary depending on body’s needs |
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Hormonal Regulation of Tubular
Reabsorption & Tubular Secretion (Table 26.4) |
- renin—angiotensin—aldosterone system
- antidiuretic hormone - atrial natriuretic peptide - parathyroid hormone |
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Urinalysis
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- volume & physical/chemical/
microscopic properties - urine = 95% water + 5% solutes - characteristics of normal urine (Table 26.5) - characteristics of abnormal urine (Table 26.6) |
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Blood Tests
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- blood urea nitrogen (BUN)
• as glomerular filtration rate ↓, BUN ↑ - plasma creatinine (BUN Level is LOW=kidney function well, has less waste & creatine) |
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Renal Plasma Clearance
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- volume of blood that is cleared of a
substance per unit of time (mL/min) • high values indicate efficient excretion, low values indicate inefficient excretion (Rate High #= kidney's working well) Measured By: Timed Collection of Urine & Analysis of it's composition |
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Urine Transport, Storage, Elimination...
Ureters |
- transport urine from renal pelvis to
urinary bladder via peristaltic contractions, hydrostatic pressure, & gravity - no valves, but pressure from fluid in bladder closes ureter openings in bladder to prevent backflow - mucus protects ureter cells from contacting urine |
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Urinary Bladder
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- hollow, distensible, muscular organ
with folds of mucosa called rugae - 700-800mL capacity - internal & external urethral sphincters |
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The Micturition Reflex
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- Micturition:
= discharge of urine from the bladder; urination, voiding - when bladder volume reaches 200-400mL, the increased pressure activates stretch receptors - micturition center in sacral spinal cord segments S2 & S3 is activated - usually we consciously urinate before the reflex occurs |
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Urethra
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- transports urine from bladder to
exterior of body - carries only urine in females; carries urine & semen in males |
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Hemodialysis
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- direct filtration of patient’s blood by
removing wastes & excess electrolytes/fluid… and then returning the cleansed blood to the patient |
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Disorders:
Nephroptosis, Edema, Glucosuria & Urinary Incontinence |
• Nephroptosis
- inferior displacement or dropping of kidney • Edema - abnormally high volume of interstitial fluid • Glucosuria - glucose in the urine • Urinary incontinence - lack of voluntary control over micturition |
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Disorders:
Kidney Stones (Renal Calculi), Uremia & Glomerulonephritis |
• Kidney stones (Renal calculi)
- crystals of salt precipitate from urine • Glomerulonephritis - inflammation of glomeruli • Uremia - toxic levels of urea in blood from kidney malfunction |
