Post on 08-Feb-2016
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Function
1. Remove nitrogenous wastes2. Maintain electrolyte, acid-base,
and fluid balance of blood3. Homeostatic organ4. Acts as blood filter5. Release hormones: calcitriol &
erythropoietin
Kidneys as Filters
• Diuretic- lose water; coffee, alcohol• Antidiuretic- retain water; ADH• Aldosterone- sodium & water reabsorption,
and K+ excretion• GFR= 180 liters (50 gal) of blood/day• 178-179 liters are reabsorbed back into
blood• Excrete a protein free filtrate
• Renal Artery• Segmental
Arteries• Interlobar
Arteries• Arcuate
Arteries• Cortical
Radiate Arteries
• Afferent Arterioles
• Glomerular Capillaries
• Efferent Arterioles
• Peritubular Capillaries
• Cortical Radiate Vein
• Arcuate Veins• Interlobar
Veins• Renal Veins
• consist of a long tubule & a ball of capillaries called a glomerulus
• the end of the tubule that surrounds the glomerulus is called Bowman’s capsule
• the remaining parts of the tubule are called the: proximal tubule loop of Henle distal tubule
• the tubule empties into a collecting duct that leads to the renal pelvis
• the renal pelvis opens to the ureter
Nephron
Each kidney contains over 1 million nephrons and thousands of collecting ducts
Nephron
Nephron’s functions: 1. glomerular filtration2. tubular reabsorption3. tubular secretion
Histology of a renal corpuscle
Pressures that drive glomerular filtration
The filtration membrane
Nephron
Composition of Glomerular Filtrate
• Water• Small Soluble Organic
Molecules• Mineral Ions
Boman’s Capsule• filtration occurs as blood pressure
in the capillaries of the glomerulus forces filtrate into Bowman’s capsule
• the process is passive (diffusion)
• the filtrate includes:
• water, salts, bicarbonate (HCO3
–), H+, urea, glucose, amino acids
Proximal Convoluted Tubule
Reabsorbs: water, glucose, amino acids, and sodium.
•65% of Na+ is reabsorbed•65% of H2O is reabsorbed•90% of filtered bicarbonate
(HCO3-)
•50% of Cl- and K+
Loop of Henle
Creates a gradient of increasing sodium ion concentration towards the end of the loop within the interstitial fluid of the renal pyramid.
•25% Na+ is reabsorbed in the loop•15% water is reabsorbed in the loop•40% K is reabsorbed in the loop
Loop of Henle:Descending Limb
• is impermeable to salts but permeable to water
• as filtrate moves through the descending limb, water steadily moves out making the filtrate more & more concentrated this occurs because the osmolarity (salt
concentration) of the interstitial fluid in the renal medulla becomes increasingly greater the further down you go
Loop of Henle:Ascending Limb
• is permeable to salts but impermeable to water
• as filtrate moves through the ascending limb, NaCl moves out making the filtrate more & more dilute
• basically, the purpose of the loop of Henle is to keep the renal medulla region of the kidney at a high osmolarity so water can move passively out of the filtrate in the collecting duct (as we’ll see shortly)
Distal Convoluted Tubule
Under the influence of the hormone aldosterone, reabsorbs sodium and secretes potassium. Also regulates pH by secreting hydrogen ion when pH of the plasma is low.
• only 10% of the filtered NaCl and 20% of water remains
ADH
Antidiuretic hormone:• Produced by posterior pituitary• Targets collecting ducts to be
more permeable to water• Results in more concentrated
urine
Collecting DuctAllows for the osmotic reabsorption of water.
• the collecting duct carries the remaining filtrate back through the renal medulla which is now very high in salt (high osmolarity)
• as the filtrate passes through the collecting duct, water can passively move out how much water moves out depends on the
amount of water needed by the body this is controlled by the hormone ADH
From the original 1800 g NaCl, only 10 g appears in the urine
Urine
Water- 95%Nitrogenous waste:
• urea• uric acid• creatinine
Ions:• sodium• potassium• sulfate• phosphate
Nitrogenous Wastes
Proteins
Amino acids
COOH -NH2
Ammonia Urea Uric Acid
Hormonal Control of Kidney Function
Fig. 18.09
Hormonal Control of Kidney Function
hypothalamus
posterior pituitary
antidiuretic hormone
collecting ducts
aldosterone
Fig. 18.16Regulation of Aldosterone secretion by renin-angiotensin-aldosterone (RAA) pathway
Hormonal Control of Kidney Function
reduced blood pressure and glomerular filtrate
juxtaglomerular apparatus
renin
Hormonal Control of Kidney Function
reninangiotensinogen
angiotensin I
angiotensin II
Hormonal Control of Kidney Function
adrenal cortex
aldosterone
angiotensin II
convoluted tubules
Urinary BladderUrinary Bladder
ureters
internal sphincters
external sphincters
urethra
Bladder1.Mucosa (transitional
epithelium)2.Muscular layer (detrusor
muscle): 3 layers of smooth muscle
3.Fibrous adventia
Internal urethral sphincter:• Smooth muscle• Involuntary control• More superiorly located
External Urethral sphincter:• Skeletal muscle• Voluntary control• Posteriorly located
Sphincter Muscles on Bladder
When bladder fills with 200 ml of urine, stretch receptors transmit impulses to the CNS and produce a reflex contraction of the bladder (PNS)
Diuresis (Micturition)
When is incontinence normal?
Why do doctors ask for a urine sample?
Urinalysis
characteristics:• smell- ammonia-like• pH- 4.5-8, ave 6.0• specific gravity– more than 1.0;
~1.001-1.003 • color- affected by what we eat: salty
foods, vitamins
odor- normal is ammonia-like
diabetes mellitus- smells fruity or acetone like due to elevated ketone levels
diabetes insupidus- yucky
asparagus---
Odor
pH- range 4.5-8 ave 6.0
vegetarian diet- urine is alkaline
protein rich and wheat diet- urine is acidic
Color- pigment is urochromeYellow color due to metabolic breakdown of hemoglobin (by bile or bile pigments)
Beets or rhubarb- might give a urine pink or smoky color
Vitamins- vitamin C- bright yellow
Infection- cloudy
Color
Water: s.g. = 1g/liter; Urine: s.g. ~ 1.001 to 1.030
Specific Gravity
When urine has high s.g.; form kidney stones
Diabetes insipidus- urine has low s.g.; drinks excessive water; injury or tumor in pituitary
Normal Constitutes of Urine
Normal Constitutes of Urine
Glucose- when present in urine condition called glycosuria (nonpathological) [glucose not normally found in urine]
Indicative of:• Excessive carbohydrate intake• Stress• Diabetes mellitus
Abnormal Constitutes of Urine
Albumin-abnormal in urine; it’s a very large molecule, too large to pass through glomerular membrane > abnormal increase in permeability of membrane
Abnormal Constitutes of Urine
Albuminuria- nonpathological conditions- excessive exertion, pregnancy, overabundant protein intake-- leads to physiologic albuminuria
Pathological condition- kidney trauma due to blows, heavy metals, bacterial toxin
Abnormal Constitutes of Urine
Ketone bodies- not normal in urine
Ketonuria- find during starvation, using fat stores
Ketonuria is couples w/a finding of glycosuria-- which is usually diagnosed as diabetes mellitus
RBC-hematuria
Hemoglobin:
Hemoglobinuria- due to fragmentation or hemolysis of RBC; conditions: hemolytic anemia, transfusion reaction, burns or renal disease
Abnormal Constitutes of Urine
Bile pigments-
Bilirubinuria (bile pigment in urine)- liver pathology such as hepatitis or cirrhosis
WBC-
Pyuria- urinary tract infection; indicates inflammation of urinary tract
Casts- hardened cell fragments, cylindrical, flushed out of urinary tract
WBC casts- pyelonephritus
RBC casts- glomerulonephritus
Fatty casts- renal damage
Abnormal Constitutes of Urine
INQUIRY1. List several functions of the kidneys.2. What does the glomerulus do?3. What are several constitutes you should not
find in urine?4. What is specific gravity?5. What two hormones effect fluid volume and
sodium concentration in the urine?6. Where are the pyramids located in the kidney?7. What vessel directs blood into the glomerulus?8. Where does most selective reabsorption occur
in the nephron?
Moment of Zen
KIDNEY
Moment of Zen