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What are the four functions of the kidney? Which two are the most critical to maintaining life?
- Removal of toxins, metabolic wastes, excess ions from blood. (Critical)
- Regulation of blood volume, chemical composition, pH (Critical)
- Endocrine functions (renin, erythropoietin)
- Activation of vitamin D
Are the kidneys intraperitoneal or retroperitoneal organs?
Which two kidney (renal) anatomical structures are considered part of the "urine collection" system (collect the urine once it is excreted)?
Calyces and renal pelvis
Why is the kidney such a vascular organ?
Because the kidneys continuously cleanse the blood and adjust its composition so they need a rich blood supply.
What is a nephron?
Structural and functional unit of the kidney that forms urine.
What part of the nephron acts as the blood "filter"? What is the tuft of capillaries within this portion called?
- Renal corpuscle
The glomerulus is an unusual capillary bed because it is fed and drained by ______.
Blood pressure in the glomerulus is extraordinarily high because the afferent arterioles are _________ than the efferent arterioles.
larger in diameter
The ___________ capillaries are low-pressure, porous capillaries adapted to absorption.
The peritubular capillaries are adapted to absorption because they have ______ osmotic pressure and _______ hydrostatic pressure.
In the peritubular capillaries:
What is the cause of this _______ osmotic pressure? What is the cause of the _______ hydrostatic pressure?
- high, all plasma/water is filtered out to leave protein behind
- low, loses all pressure due to friction
What capillaries, which run parallel to the loop of Henle, function in the formation of concentrated urine?
Vasa recta (peritubular capillaries)
The granular cells of the juxtaglomerulus apparatus (JGA) are located in the walls of the ________ and act as ____________ that sense __________ and secrete __________ in response to low blood pressure.
- afferent arteriole
- blood pressure
The macula densa cells of the JGA are located in the wall of the ___________ and act as __________ that sense NaCl content of the filtrate.
- ascending limb
What are the three layers of the filtration membrane of the kidney?
- Fenestrated endothelium of glomerular capillaries
- Visceral membrane of the glomerular capsule
- Gel-like basement membrane
What in the blood gets "filtered" by the filtration membrane (what cannot pass through and stays in the capillaries)?
- formed elements (RBCs, WBCs, platelets)
- plasma proteins (macro molecules)
Glomerular filtration is a _________ mechanical process driven by _________.
- hydrostatic pressure
Why is high glomerular blood pressure so important to kidney function?
to push water and solute out of blood across filtration membrane
What are two mechanisms that are involved with renal autoregulation (intrinsic control of GFR)?
- myogenic mechanism
- tubuloglomerular feedback mechanism
The macula densa cells of the JGA will sense that the NaCl concentration of the filtrate is _________ if GFR decreases, and will inhibit the release of arteriolar vasoconstrictor to increase GFR.
Renin is released by the granular cells of JGA in response to low blood pressure. What are the three triggers for this release?
- Reduced stretch of granular cells
- Stimulation of the granular cells by activated macula densa cells
- Direct stimulation of granular cells via sympathetic nerves
What is the end product of the cascade which is begun by renin catalyzation?
What are the four effects this "end product" (Angiotensin II) has on the kidney which help to increase blood pressure to homestatic levels?
- -Stimulating the reabsorption of Na+
- -Stimulating the hypothalamus to release ADH and activates thirst center
- -Constricts efferent arterioles, decreasing peritubular capillary hydrostatic pressure and increases fluid reabsorption
- -Causes glomerular mesangial cells to contract, decreasing surface area available for filtration
What would happen if there was no tubular reabsorption by the kidney?
Our total plasma volume would be drained away as urine in less than 30 minutes.
Sodium reabsorption, driven by active transport via the _________ pump in the _________ membrane of the cells lining the renal tubules, provides the energy and the means for reabsorbing _______ in the kidneys.
- Na+/K+/ATPase pump
- basolateral membrane
- most other substances
Water is reabsorbed by _______ aided by water-filled pores called _________.
Organic nutrients (glucose, amino acids, vitamins) are reabsorbed by ___________ with sodium at the luminal membrane of tubular cells.
The transport proteins are specific to the substances being reabsorbed and are produced in different numbers depending on the need of the body to retain a filtered solute. For glucose, this number, reflected by its _______ is _________. Because of this, a healthy individual will have __________ glucose in their urine.
The majority of tubular reabsorption takes place in the ________.
proximal convoluted tubule
What is the primary function of the loop of Henle?
to create a medullary osmotic concentration gradient
Which of the two countercurrent mechanisms is responsible for establishing the medullary osmotic (concentration) gradient in the medulla?
What are the differences in permeability between the ascending and descending loops that are responsible for (the countercurrent mechanism)?
- Descending loop is freely permeable to H2O and impermeable to solutes
- Ascending loop is impermeable to H2O and selectively permeable to solutes
Which countercurrent mechanism is responsible for maintaining the medullary osmotic (concentration) gradient in the medulla? What capillaries are involved?
- Countercurrent exchanger
- Vasa recta
What solute is cycled between collecting ducts and ascending loop of Henle that helps maintain the high osmolality in the deep portion of the medulla?
Why does the kidney go to all this trouble to establish this medullary osmotic (concentration) gradient?
Without this gradient you would be unable to raise the concentration of urine above 300 mOsm, permits the control of water reabsorption (water balance) from filtrate in the collecting ducts in order to respond to low blood volume or blood pressure.
What hormone is responsible for controlling water reabsorption from the collecting ducts? What is the direct action of this hormone that permits this function?
- In absence of ADH the collecting ducts remain impermeable to water (no aquaporins)
What type of event would trigger the release of ADH?
Any event that raises plasma osmolality (sweating, diarrhea, reduced blood volume or blood pressure)
Would the urine be dilute or concentrated if large amounts of ADH are circulating in the body? Why?
- ADH inserts aquaporins which result in reabsorption of water, thereby leaving the formed urine concentrated
What are diuretics? What two diseases are they most commonly used to treat?
- Chemicals that enhance the urinary output
- Hypertension and Congestive Heart Failure
The most commonly used diuretic is the powerful "loop diuretic" furosemide (lasix). What is its mechanism of action?
Inhibit formation of the medullary gradient by inhibiting Na+ absorption in the ascending limb of the loop of Henle.
Why does alcohol increase urine volume (and can lead to dehydration in certain circumstances)?
Because alcohol inhibits ADH.
What type of substance will have renal clearance which is equal to glomerular filtration rate (GFR)? What type of substance will have a renal clearance of zero? Give an example.
- A substance that is freely filtered and neither reabsorbed nor secreted by the kidneys. (Inulin)
- A substance that is completely reabsorbed. (Glucose)
What are the renal clearance tests used for?
- To determine GRF (glomerular filtration rate) to:
- -detect glomerular damage
- -follow the progress of renal disease
What two blood test are routinely used to assess renal function? Which is more specific for renal function?
- Creatinine clearance - more specific
- BUN (Blood Urea Nitrogen)
What are the three main causes of chronic renal disease? What part of the nephron is most affected?
- -Diabetes mellitis
What happens to homeostasis when an individual goes into renal failure?
Ionic and pH imbalances occur and wastes accumulate quickly in blood.
What is the treatment for renal failure?
Renal transplant and hemodialysis
What is responsible for the yellow color of urine?
What is the primary component of urine? What is the primary solute? Where does it come from?
- 95% water
- Derived from normal breakdown of amino acids
Is it normal to find protein in urine? How about RBC's or WBC's? Why or why not?
- Because they're too big to get through glomerulus. Indicates pathology.
What is the function of the ureters (why are they like the esophagus)?
Conveys urine from kidneys to bladder.
What causes peristalsis of the ureters?
Response to stretch by urine.
Why is an obstructing renal calculus (stone) so painful?
Increased pressure in kidneys and peristalsis of ureter on sharp calculus.
What two things are known factors that increase the risk of calculus formation?
Dehydration and alkaline urine
What is the function of the urinary bladder? What is the primary component of the bladder wall?
- Temporary storage of urine.
- Thick detrusor muscle (3 layers of smooth muscle)
What are the two urethral sphincters? How are they controlled? Do they contract or relax to allow urine to pass?
- Internal urethral sphincter - involuntary (smooth muscle) - contracts to open.
- External urethral sphincter - voluntary (skeletal muscle) - relaxes to open.
Are urinary tract infections more common in women or men? Why? What is the most common infectious organism? Where does it come from?
- Shorter urethra
- E coli
What are the three fluid compartments/subcompartments in the body? Which contains the most fluid and which the least?
- Intracellular fluid compartment (ICF) 2/3 within cells
- Extracellular fluid compartment (ECF) 1/3 outside cells, divided into 2 parts:
- -interstitial fluid (IF)
Why do males have a higher water content than females?
Higher water content of muscle.
What is the difference between electrolyte and non-electrolyte solutes?
- Electrolytes dissociate into ions in water.
- Non-electrolytes don't dissociate in water.
What is the main extracellular ion (cation)? intracellular ion? Why are these ions located on opposite sides of the plasma membrane?
- Opposite due to plasma membrane and Na+/K+ pumps
What is insensible water loss?
Loss of water through lungs and skin
What are the two mechanisms which maintain water balance (keep osmolality of body fluids within narrow range) by controlling water intake and output?
- Thirst mechanism
- Urinary output
What is the trigger for these two mechanisms to maintain water balance?
- Hypothalamic thirst center osmoreceptors are stimulated by rising plasma osmolality, dry mouth, angiotensin II and baroreceptor inputs, substantial decrease in blood volume or pressure.
- Hypothalamic osmoreceptors sense the ECF solute concentration and trigger or inhibit ADH release.
Why can people not survive for long without drinking?
Because of obligatory water loss through lungs, skin, feces, urine.
What is dehydration? Why is it so dangerous?
- Negative fluid balance due to water output exceeding input over a period of time.
- May lead to mental confusion and ultimately hypovolemic shock.
What electrolyte imbalance usually accompanies overhydration (hypotonic hydration)? Why?
- Because Na+ is the main cation in ECF and becomes more diluted
What is edema? What are its four causes?
- Atypical accumulation of interstitial fluid that leads to tissue swelling.
- -Accelerated fluid loss from blood due to increase capillary hydrostatic pressure
- -Accelerated fluid loss due to increased capillary permeability
- -Hindered fluid return due to an imbalance in colloid osmotic pressures
- -Hindered fluid return due to blocked lymph vessels
How does edema impair tissue function?
By increasing the distance nutrients and oxygen must travel to reach cells.
What are the four reasons that electrolytes (salts) are so important to body homeostasis?
- Controlling fluid movements
- Secretory activity
- Membrane permeability
________ salts have the primary role in controlling extracellular fluid volume and water distribution in the body. What are the two qualities of the cation of these salts that give them this primary role?
- -Most abundant cation in the ECF and only one exerting significant osmotic pressure
- -Cellular membranes are relatively impermeable to Na+
Sodium-water balance is critical to survival because it is linked to __________ and ___________ control mechanisms.
- blood pressure
- blood volume
How does aldosterone cause an increase in blood volume/blood pressure? What hormone does it work in tandem with in the collecting ducts of the kidney to perform this task?
- By causing active reabsorption of remaining Na+ from distal DCT and collecting ducts
- ADH (without aquaporins, water won't follow Na+)
_________, secreted by the granular cells of the JGA starts an enzymatic cascade that produces _________ which prompts the secretion of aldosterone by the adrenal gland.
__________, the chief intracellular cation, is essential for normal ________ functioning.
Imbalances of the chief intracellular cation, both __________ and ________ can lead to sudden death due to disruption of ___________.
- electrical conduction of the heart
Potassium balance is controlled in the ___________ of the kidney by changing the amount of potassium that is __________.
- cortical collecting ducts
- secreted into the filtrate
Why is pH balance so important to body homeostasis?
Because all chemical reactions are influenced by the pH of their fluid environment.
What is the "normal" arterial pH range?
7.35 to 7.45
Concentration of hydrogen ions (pH) is regulated sequentially by what three mechanisms?
- Chemical buffer system
- Brain stem respiratory centers
- Renal mechanisms
What is a chemical buffer?
A system of one or more compounds that acts to resist changes in pH when a strong acid or base is added.
Large amounts of H+ ions are produced as by-products or end products of metabolism intracellularly. Therefore, the 3/4 of all buffering in the body takes place in the cells via the _________ buffer system.
The __________ buffer system is the only important extracellular fluid (ECF) chemical buffer system in the body.
What two organ systems (physiological buffer systems) are incorporated to deal with pH shifts beyond the limits of the chemical buffer systems?
Rising plasma H+ (falling pH) from metabolic processes (metabolic acidosis) causes the respiratory system to _________. This corrects the pH imbalance by removing ___________ from the body, which drives the equilibrium reaction for carrying carbon dioxide in the blood to the _________, reducing the H+ concentration.
- stimulate deeper and more rapid respiration
Respiratory system impairment can cause pH imbalance with hypoventilation causing __________ and hyperventilation causing ___________.
- respiratory acidosis
- respiratory alkalosis
The kidneys are critical to maintaining acid base balance because only the kidneys can prevent metabolic acidosis by ___________.
eliminating other metabolic acids
What are the two most important renal mechanisms for regulating acid-base balance?
- Conserving (reabsorbing) or generating new HCO3-
- Excreting HCO3-
What is the most common cause of acid-base imbalance? What is it due to?
Due to decrease in ventilation or gas exchange (pneumonia, COPD)
What type of acid-base imbalance is hyperglycemic diabetic crisis likely to cause? How would this patient be breathing and would their PCO2 be high or low?
- Metabolic acidosis
- Deep and rapid breathing, PCO2 would be low
What are the male and female gonads (primary sex organs)? What is their function?
- Testes - produce sperm
- Ovaries - produce ova
Why do the testes hang outside the abdominal cavity?
3°C lower than core body temperature necessary for sperm production
Where is sperm stored until ejaculation?
What fills with blood to cause penile erection?
Corpus spongiosum and corpus cavernosa (erectile tissues)
What is a vasectomy and why is it an effective form of birth control?
Cutting and ligating the ductus deferens, cuts off route of sperm.
What produces 70% of the semen volume?
What is BPH and what problem does it cause?
- Benign Prostatic Hyperplasia
- Enlargement of prostate gland, constricts prostatic urethra, results in urinary frequency, urgency and decreased urinary flow.
What are the components of semen? Why does it contain nutrients (fructose)?
- Fructose, ascorbic acid, prostaglandins
- Enhance sperm motility or fertilizing ability
- Alkalinity neutralizes the acid in the male urethra and female vagina to protect sperm
- Antibiotic chemicals destroy certain bacteria
What are the five functions of testosterone?
- Prompts spermatogenesis
- Causes growth to adult size of all accessory reproductive organs (glands, ducts, penis)
- Multiple anabolic effect throughout body
- Basis of sex drive in males
- Secondary sex characteristics
When the oocyte (egg) is expelled from the ovary, what is it released into? How is it transported into the female ductal system (uterine tube)? Where does fertilization occur?
- Peritoneal cavity
- Ciliated fimbriae of infundibulum create currents of peritoneal fluid to move ovulated oocyte into uterine tube.
- Within the uterine tube (ampulla)
Pelvic inflammatory disease (PID) cause what two complications?
Scarring of uterine tubes can cause infertility and ectopic pregnancy
What is an ectopic pregnancy? What can it be a medical emergency?
- Pregnancy that develops outside of the uterus.
- Pregnancy cannot be supported and fetus aborts sometimes with substantial bleeding.
In what layer of the uterine wall does the embryo implant and grow?
By what point has a female produced her lifetime supply of primary oocytes (eggs)?
What happens to the follicle after ovulation? What is its function?
Transformed to glandular structure called corpus luteum, secretes progesterone and estrogen until the placenta takes over at about 3 months gestation.
A surge in levels of what hormones causes ovulation?
What causes the menstrual phase of the uterine cycle?
Rapid drop in estrogen and progesterone levels
What gamete determines the sex of offspring?
The Y chromosome contributed by the male.
What causes menopause?
Declining estrogen levels.