Exam 3 Flashcards
Functions of the Kidney
- Eliminates nitrogenous waste
- Regulates blood ionic composition
- Regulates blood pH
- Regulates blood volume
- Releases erythropoietin and calcitriol
- Excretes wastes and foreign substances
- Detoxifies free radicals and certain drugs
Glomerulus
Ball of capillaries in the renal corpuscle
Glomerular Capsule/Bowman’s Capsule
Performs the first step in filtration of blood to form urine
Located in the renal corpuscle
Proximal Convoluted Tubule
Beginning of the nephron
Regulates the pH of the filtrate by exchanging hydrogen ions for bicarbonate ions
Secretes creatinine
Descending Loop of Henle/Nephron Loop
Thin limb
Low permeability to ions and urea, high permeability to water
Water passes by osmosis from tubule to ECF, leaving NaCl
Ascending Loop of Henle/Nephron Loop
Thick and thin segment
Drains urine into the distal convoluted tubule
Has pumps that cotransport Na, K, and Cl into ECF
Distal Convoluted Tubule
End of the nephron
Responsible for the reabsorption of sodium, water, and secretion of hydrogen potassium
Collecting Duct
- Consists of a series of tubules and ducts that connect the nephrons to the ureter
- Participates in electrolyte and fluid balance through reabsorption and excretion (regulated by aldosterone)
- Concentrates urine
Pathway Flow of Glomerular Filtrate
- Glomerular capsule (capsular filtrate)
- PCT (tubular fluid)
- Nephron loop
- DCT
- Collecting duct
- Papillary duct (urine)
- Minor calyx
- Major calyx
- Renal pelvis
- Ureter
- Urinary bladder
- Urethra
Ureters Function and Physiological Valve
Drain urine from bladder to urethra
Valve is a fold of bladder mucosa by hydrostatic backpressure that prevents the backflow of urine
Serosa
Tissue of a serous membrane
Mucosa
Mucous membrane
Bladder Location
Muscular sac on the floor of the pelvic cavity, inferior to the peritoneum and posterior to the pubic symphysis
Bladder Mucosa Epithelium
Transitional epithelium
Detrusor of Bladder
Muscularis that consists of three layers of smooth muscle
Trigone of Bladder
Openings of two ureters and urethra from this smooth-surfaced triangular area
3 Urethral Regions for Males
- Prostatic Urethra
- Membranous Urethra
- Spongy Urethra
Cystitis
Bacterial contamination of the urethra is more common in females because of their shorter urethra and location of orifice
Blood Supply to the Nephron
Artery –> Capillary –> Artery –> Capillary –> Vein blood flow
3 Basic Processes by the Nephron
- Glomerular filtration
- Tubular reabsorption
- Tubular secretion
Glomerular Filtration
Portion of blood plasma is filtered into the kidney
Capillary exchange
Tubular Reabsorption
Water and useful substances reabsorbed into the blood
Tubule to Blood
Tubular Secretion
Wastes are removed from the blood and secreted into the urine
Blood to Tubule
Difference Between Blood and Glomerular Filtrate
Blood plasma contains large molecules and protein that are not present in glomerular filtrate
Layers of the Glomerular Filter
- Fenestrated endothelium
- Basement membrane
- Filtration slits
Fenestrated Endothelium
Highly permeable, but blood cells do not pass through
Basement Membrane
Excludes molecules larger than 8nm
Filtration Slits
Numerous extensions known as pedicels
Large anions cannot pass
Podocytes
Cells that wrap around the capillaries of the glomerulus
What substances are allowed/not allowed to pass through the glomerular membrane?
Pass: urea, glucose, insulin
Do not pass: albumin and hemoglobin
Glomerular Filtration Rate
10.5-12.5 mL/min
180 L/day
Reabsorption
Process of reclaiming water and solutes from the tubular fluid and returning them to the blood
Occurs until the plasma level reaches a specific concentration known as the renal threshold
What substances are reabsorbed in tubular reabsorption?
- Sodium
- Water
- Glucose/amino acids
- Potassium
- Urea
Where does reabsorption take place?
In the glomerulus
Where is the majority of glomerular fluid reabsorbed?
Proximal convoluted tubule
Where is reabsorption a non-hormone-dependent process?
Distal convoluted tubule
In what part is reabsorption regulated by hormones?
Collecting duct
What is the “transport maximum”/”renal threshold”?
Concentration of a substance dissolved in the blood above which the kidneys begin to remove it into the urine
Location of Countercurrent Mechanism
Nephron loop
What substances are reabsorbed through the descending nephron loop and ascending nephron loop?
Descending: water
Ascending: sodium, potassium, and chlorine
How is the reabsorption related to osmolarity of the interstitial fluid of the medulla?
Descending: raises osmolarity
Ascending: lowers osmolarity
What creates high osmolarity of the medullary interstitial fluid?
Water leaves descending limb through osmosis and leaves NaCl behind
What substances are secreted into glomerular filtrate?
- Potassium
- Hydrogen
- Ammonium
- Creatinine
- Urea
- Some hormones and drugs
Bicarbonate Buffer System Formula
CO2 + H2O H2CO3 HCO3 + H+
How can the nephrons affect body pH?
Proximal tubule regulates pH by exchanging H+ for bicarbonate until a state of acid/alkaline base is attained
Normal Components of Urine
- Urea
- Chloride
- Sodium
- Potassium
- Creatinine
Causes of Glycosuria
Elevated blood glucose levels
Causes of Proteinuria
Caused by kidney disease that can allow proteins such as albumin to leak
Causes of Hematuria
UTIs can cause blood cells to leak into the urine
Causes of Pyuria
White blood cells can be found in the blood during infections
Causes of Ketouria
Metabolic abnormalities, dietary conditions
Causes of Bacteriuria
Bacteria in the urine can be caused by UTIs
Stimulus for Antidiuretic Hormone
Dehydration, loss of blood volume, and rising blood osmolarity stimulate arterial baroreceptors and hypothalamic osmoreceptors to stimulate the posterior pituitary to secrete ADH
Mechanism for Antidiuretic Hormone
ADH makes the collecting duct more permeable to water, so water reenters the blood and tissues instead of the urine
Stimulus for Aldosterone
Salt-retaining hormone secreted by the adrenal cortex when blood sodium concentration falls or potassium concentration rises
Mechanism for Aldosterone
Acts on the thick segment of the ascending loop, DCT, and cortical portion of the collecting duct to stimulate the segments to reabsorb Na and secrete K
Water and Cl follow Na
Stimulus for Atrial Natriuretic Peptide
Secreted by the heart in response to high blood pressure
Mechanism for Atrial Natriuretic Peptide
- Dilates afferent arteriole and constricts efferent arteriole to increase the GFR
- Antagonizes the renin-angiotensin-aldosterone mechanism by inhibiting renin and aldosterone secretion
- Inhibits secretion of ADH
- Inhibits NaCl reabsorption
Stimulus for Renin
Drop in blood pressure stimulates the release of renin
Secreted from the juxtaglomerular kidney cells, stimulated by the macula densa
Mechanism for Renin
Restores perfusion pressure in the kidneys
Combines with angiotensinogen to form angiotensin I
Stimulus for Angiotensin
Stimulated by renin and low blood pressure
Causes vasoconstriction and increases blood pressure
Erythropoietin
Produced in the kidney
Stimulated by drop in O2 pressure
Dilute Urine Mechanism
Water reabsorbed in the thin limb, ions reabsorbed in the thick limb
Osmolarity of Dilute Urine
Low
Specific Gravity of Dilute Urine
High
Concentrated Urine Mechanism
Principal cells and ADH can remove water from the urine if interstitial fluid has a high osmolarity
Cells in the collecting duct reabsorb more water and urea when ADH is increased
Osmolarity of Concentrated Urine
Low
Specific Gravity of Concentrated Urine
Low
Renin-Angiotensin-Aldosterone Mechanism
Involved in the regulation of plasma sodium concentration and arterial blood pressure
Ultimately want to raise blood pressure
ACE Inhibitors
Prevent the body from creating angiotensin II and relaxes blood vessels and reduces the amount of water reabsorbed by the kidneys
Diuretic Effects
Help your body get rid of unneeded water and salt by increasing the amount of salt and water that comes through the urine
Diuretic Uses
Used for high blood pressure, heart failure, kidney and liver problems, and glaucoma
Fluid Compartments (%)
65% ICF
35% ECF
Categories of ECF
25% interstitial fluid
8% blood plasma and lymph
2% transcellular fluid
Sources of Water
Metabolic and Preformed
Metabolic Water Production Formula
C6H12O6 + 6 O2 —> 6 CO2 + 6 H2O
Gains of Water in a Day
700 mL/day in food
1600 mL/day in drink
Losses of Water in a Day
1500 mL/day as urine 200 mL/day as feces 300 mL/day as expired breath 100 mL/day as sweat 400 mL/day as cutaneous transpiration
Hypovolemia
Occurs when proportionate amounts of water and sodium are lost without replacement
Dehydration
Occurs when the body eliminates significantly more water than sodium
Fluid Excess
Both sodium and water are retained and the ECF remains isotonic
Fluid Sequestration
A condition in which excess fluid accumulates in a particular location
Electrolyte Concentration in the Blood
Chlorine and sodium are very abundant
Electrolyte Concentration in ICF
Potassium, magnesium, and phosphorus are very abundant
Three Buffering Systems
- Bicarbonate Buffer System
- Phosphate Buffer System
- Protein Buffer System
Phosphate Buffer System Equation
H2PO4 HPO4^2 + H+
Protein Buffer System Equation
COOH —> COO + H+
Protein Buffer System
More concentrated than either bicarbonate or phosphate buffers
Amounts for about three-quarters of all chemical buffering in the body fluids
Respiratory Control of pH
HCO3 + H+ —> H2CO3 —> CO2 + H2O
How does buffering control pH?
Buffers resist changes of pH in the body fluids
How does secretion control pH?
Secretion involves decreasing the rate of hydrogen ions secreted into the urine and the rate of bicarbonate ion reabsorption
Insensible Water Loss
Water loss due to water that passes through the skin and is lost by evaporation
Sensible Water Loss
Urination
Obligatory Water Loss
The minimal amount of fluid loss from the body that can occur
Respiratory Acidosis
Respiratory failure where the lungs cannot remove enough of the carbon dioxide in the body
Respiratory Alkalosis
Increased respiration elevates the blood pH beyond the normal range and reduces carbon dioxide levels in the blood
Metabolic Acidosis
When the body produces excessive quantities of acid or when the kidneys are not removing enough acid from the body
Metabolic Alkalosis
Decreased hydrogen ion concentration, leading to increased bicarbonate
Mucosa Cells in the Esophagus
Stratified squamous
Mucosa Cells in the GI Tract
Simple columnar