Unit 4: Urinary
Aldosterone plays a primary role in adjustment of ___ excretion
sodium
renal cortex
-outer zone of parenchyma -about 1 cm thick -has extensions called renal columns that project toward the sinus and divide the medulla into 6-10 renal pyramids. -One pyramid and the overlying cortex constitute one lobe of the kidney.
major calyx
-2-3 minor calyx convergences -2-3 of these converge to form the funnel-like renal pelvis
renal pyramids
-6-10 divisions of the medulla created by the division of the renal columns. -conical -broad base facing the cortex -blunt point (renal papilla) facing the sinus -one pyramid and the overlying cortex constitute one lobe of the kidney
minor calyx
-A cup-shaped cavity at the base of the renal papilla, -drains urine from the renal papillae into the major calyxes -2-3 minor converge to form major calyx
Which are true regarding respiratory compensation?
-It corrects the pH of body fluids by expelling or retaining CO2. -It is effective in correcting for PCO2 imbalances
Calcium does which of the following?
-Participates in bone and tooth development -Acts as second messenger and activates exocytosis during neurotransmission -Acts as a factor for blood clotting -Participates in muscle contraction
What are the major chemical buffer systems of the body?
-The phosphate buffer system -the bicarbonate buffer system -the protein buffer system
Why is it important to maintain the pH of blood and tissue fluids within normal limits?
-The structure and function of macromolecules are pH dependent -Slight deviations from normal pH can shut down metabolic pathways.
renal papilla
-a blunt point of the renal pyramid -faces the sinus -the papilla of each pyramid is nestle in a cup called a minor calyx which collects its urine
Vasa recta
-a network of vessels that supplied the renal medulla -arise from the efferent arterioles of the nephrons closest to the medulla -capillaries of the vasa recta lead into venules that ascend and empty into the arcuate and radiate veins. -capillaries of the vasa recta are wedged into the tight spaces b/t the the medullary parts of the renal tubule, and carry away water and solutes reabsorbed by those sections of the tubule.
glomerulus
-a spheroidal mass of blood capillaries in the kidney that filters plasma and produces glomerular filtrate, which is further processed to form the urine. -lead to by afferent arterioles -enclosed in a sphere called the glomerular capsule -blood leaves by way of efferent arteriole -has a large inlet and a small outlet
Renal Circulation
-account for 0.4% of body weight, but receive 1.1 L of blood per minute (21% of the cardiac output - renal fraction) - for the purpose of waste removal than to meet metabolic needs of kidney. -each supplied by renal artery
Which hormones regulate the amount of water and salt reabsorbed by the DCT and collecting duct?
-aldosterone -antidiuretic hormone -natriuretic peptides
renal artery
-arising from the aorta -just before entering the hilum, divides into a few segmental arteries
urinary pole
-at this pole, the parietal wall of the capsule turns away from the corpuscle and gives rise to the renal tubule
The filtration pressure in the glomerulus is determined by the balance of which two pressures?
-blood hydrostatic -colloid osmotic
By which means can water move from one fluid compartment to another?
-capillary filtration -osmosis
What are possible consequences of hypernatremia?
-edema -hypertension -water retention
fibrous capsule
-encloses the kidney like a cellophane wrapper anchored at the hilum -protects it from trauma and infection
renal columns
-extensions of the cortex -project toward the sinus and divide the medulla into 6-10 renal pyramids
proximal convoluted tubule (PCT)
-part of nephron -one of 4 regions of renal tubule -arises from the glomerular capsule -longest and most coiled of the four regions -dominates histological sections of renal cortex -has a simple cuboidal epithelium w/ prominent microvilli (brush border) -great deal of absorption occurs here -microvilli give epithelium a distinctive shaggy look
Functions of the kidneys
-filter blood and excrete toxic metabolic wastes -regulate blood volume, pressure, and osmolarity by regulating water output -regulate electrolyte and acid-base balance of the body fluids -secrete hormone erythropoietin, which stimulates the productions of red blood cells and this supports the oxygen-carrying capacity of the blood -help regulate calcium homeostasis and bone metabolism by participating in the synthesis of calcitriol -clear hormones and drugs from the blood and thereby limit their action -detoxify free radicals -in conditions of extreme starvation, they help to support the blood glucose level by synthesizing glucose from amino acids
glomerular capsule
-formerly called the Bowman capsule -a double walled capsule around each glomerulus of the kidney; receives glomerular filtrate and empties into the proximal convoluted tubule -parietal (outer) layer is a simple squamous epithelium -visceral (inner) layer consists of elaborate cells called podocytes wrapped around the capillaries of the glomerulus. -two layers separated by a filtrate-collecting capsular space -this space appears as an empty circular or C-shaped space around the glomerulus -the simple squamous epithelium of the capsule becomes simple cuboidal in the tubule
renal pelvis
-funnel like convergence of major calyx. -continues down into ureter
renal parenchyma
-glandular tissue that forms the urine -appears c-shaped in frontal section -encircles a medial cavity, the renal sinus, occupied by blood and lymphatic vessels, nerves, and urine collecting structures. -divided into two zones: -renal cortex -renal medulla
What stimulates the secretion of aldosterone?
-hyponatremia -hypotension -hyperkalemia
fibrous renal fascia
-immediately deep to the parietal peritoneum -binds the kidney and associated organs to the abdominal wall -fused with the peritoneum anteriorly and with the fascia of the lumbar muscles posteriorly
Which result from activation of the renin-angiotensin system?
-increased secretion of aldosterone -increased release of ADH -stimulated thirst -vasoconstriction -increased blood pressure -increased water retention
renal medulla
-inner zone of parenchyma -faces the sinus -divided into 6-10 renal pyramids by renal columns -receives only 1-2% of the total renal blood flow -blood flow supplied by a network of vessels called the vasa recta
Which are functions of potassium?
-it helps produce the resting membrane potentials and action potentials of nerve and muscle cells -it is an essential cofactor for protein synthesis and some other metabolic processes -it is the greatest determinant of intracellular osmolarity and cell volume -it plays a role in cotransport and thermogenesis via the Na-K pump
Principal organs of the urinary system:
-kidneys (2) -ureters (2) -urinary bladder -urethra
perirenal fat capsule
-layer of adipose tissue -cushions the kidney and holds it in place
Renal vein
-leaves the hilum and drains into the inferior vena cava
Kidney position and associated structures:
-lie against posterior abd wall @ lvl of vert T12 to L3. -R kidney slightly lower than L (b/c of space occupied by right lobe of liver above it) -rib 12 crosses the approx middle of L kidney -kidneys are retroperitoneal, along w/ the ureters, urinary bladder, renal artery, and vein, and the adrenal glands
renal sinus
-medial cavity encircled by parenchyma -occupied by blood and lymphatic vessels, nerves, and urine collecting structures -adipose tissue fills the remaining space in the sinus and holds these structures in place
Which are parts of a renal tubule?
-nephron loop -distal convoluted tubule -proximal convoluted tubule -collecting duct
renal plexus
-nerves and ganglia wrapped around each renal artery -follows branches of the renal artery into the parenchyma of the kidney, issuing nerve fibers to the blood vessels and convoluted tubules of the nephrons
nephron
-one of approximately 1 million blood-filtering, urine producing units in each kidney -consists of a glomerulus, glomerular capsule, proximal convoluted tubule, nephron loop, and distal convoluted tubule -supplied by afferent arterioles -each kidney has ~1.2 million nephrons -composed of 2 principle parts: -renal corpuscle (filters the blood plasma) -renal tubule (long, coiled, converts filtrate to urine)
renal corpuscle
-one of two parts of a nephron -filters the blood plasma -consists of the glomerulus and a two-layered glomerular capsule (formerly Bowman capsule) that encloses it
vascular pole(s)
-opposite sides of the renal corpuscle -at this pole the afferent arteriole enters the capsule, bringing blood to the glomerulus, and the efferent arteriole leaves the capsule and carries blood away.
cortical radiate arteries
-originate from arcuate arteries -pass upward into the cortex of kidney -as it ascends through cortex, series of afferent arterioles arise from it
afferent arterioles
-originate from cortical radiate arteries -arise at nearly right angles (like limbs rising from the trunk of a pine tree) -each supplies one functional unit of the kidney called a nephron -leads to a ball of capillaries called glomerulus -significantly larger than the efferent arteriole
arcuate arteries
-originate from interlobar arteries -make a sharp 90 degree bend and travel along the base of the pyramid -gives rise to several cortical radiate arteries
segmental arteries
-originate from renal arteries -further divide into a few interlobar arteries
interlobar arteries
-originate from segmental arteries -penetrates each renal column -travels b/t the pyramids toward the corticomedullary junction -branches again along the way to form arcuate arteries
distal convoluted tubule (DCT)
-part of nephron -one of 4 regions of renal tubule -begins shortly after the ascending limb reenters the cortex -shorter and less coiled than the proximal convoluted tubule, so fewer sections of it are seen in histological sections -has cuboidal epithelium with smooth-surfaced cells, nearly devoid of microvilli -the DCT is the end of the nephron
nephron loop
-part of nephron -one of 4 regions of renal tubule -formerly called loop of Henle -long U-shaped portion of renal tubule found mostly in the medulla -begins where the PCT straightens out & dips toward or into the medulla, forming the descending limb of the loop -at its deep end, the loop turns 108 degrees and forms the ascending limb, which returns to the cortex, traveling parallel and close to the descending limb -loop is divided into thick and thin segments -thick segments: have simple cuboidal epithelium -form initial part of descending limb and part or all of the ascending limb -cells here are heavily engaged in active transport of salts (so they have a very high metabolic activity and are loaded w/ mitochondria, accounting for their thickness) -thin segments: has simple squamous epithelium -forms the descending limb, and in some nephrons, it rounds the bend and continues partway up the ascending limb -cells here have low metabolic activity, but the thin segment of the descending limb is very permeable to water -responsible for maintaining an osmotic gradient in the medulla that helps the body conserve water
renal tubule
-reabsorbs most of the water and solutes that filter out of the blood at the glomerulus -returns the water and solutes back to the bloodstream by way of the peritubular capillaries surrounding it -long, coiled -converts filtrate from blood plasma into urine -one of two principal parts of a nephron -the simple squamous epithelium of the capsule becomes simple cuboidal in the tubule -a duct that leads away from the glomerular capsule and ends at the tip of a medullary pyramid -~ 3cm long & divided into 4 regions: -proximal convoluted tubule -nephron loop -distal convoluted tubule -collecting duct
collecting duct
-receives fluid from many nephrons -one of four regions of renal tubule -receives fluid from the DCTs of several nephrons as it passes back into the medulla -numerous collecting ducts converge toward the tip of a medullary pyramid, and near the papilla, they merge to form a larger papillary duct -about 30 papillary ducts end in pores at the conical tip of each papilla -urine drains from these pores into the minor calyx that encloses the papilla -the collecting and papillary ducts are lined with simple cuboidal epithelium
Which solutes are reabsorbed from the nephron loop?
-sodium ions -potassium ions -chloride
peritubular capillaries
-supplied by efferent arterioles -named for the fact that they form a network around another part of the nephron (renal tubule) -carry the water and solutes from the renal tubule away to the cortical radiate veins, arcuate veins, interlobar veins, and the renal veins, in that order.
efferent arteriole
-supplied by glomerulus -leads to a plexus of peritubular capillaries -smaller than the afferent arteriole
cortical nephrons
-the remaining nephrons farther from the medulla -have relatively short nephron loops that dip only slightly into the outer medulla before turning back or turn back even before leaving the cortex -some of them have no nephron loops at all
Juxtamedullary nephrons
-those nephrons close to the medulla -have very long nephron loops that extend as far as the apex of the renal pyramid -only 15% of the nephrons are juxtamedullary, but they are most solely responsible for maintaining the osmotic gradient in the medulla that helps the body conserve water
Renal clearance is the net effect of which of the following?
-tubular secretion -tubular reabsorption -glomerular filtration
Gross anatomy of kidney
-weighs about 150g -measures about 11cm long, 6cm wide, 3cm thick (about the size of a bar of soap) -the lateral surface is convex, and the medial surface is concave and hasa slit, the hilum, that admits the renal nerve, blood vessels, lymphatics, and ureter. -protected by 3 layers of connective tissue: -fibrous renal fascia -perirenal fat capsule -fibrous capsule -suspended by collagen fibers that extend from the fibrous capsule, through the fat, to the renal fascia -the kidneys drop about 3cm when one goes from lying to sitting. -renal parenchyma (glandular tissue that forms urine) appears c-shaped in frontal section -encircles a medial cavity (renal sinus) occupied by blood and lymphatic vessels, nerves, and urine collecting structures -divided into 2 zones: -outer renal cortex -extensions of cortex: renal columns -inner renal medulla -divided into 6-10 renal pyramids by the renal columns -blunt point facing sinus on end renal papilla -nestled into minor calyx -2 or 3 converge to form major calyx -2 or 3 converge to form renal pelvis -boundary between cortex and medulla: -corticomedullary junctions
Starting at renal papilla, place structures through which urine will flow in order.
1. Minor calyx 2. Major calyx 3. Renal pelvis 4. Ureter
About how many nephrons are in a kidney?
1.2 million
Which term refers to a tissue fluid pH above 7.45?
Alkalosis
azotemia
An elevated BUN. may indicate renal insufficiency and can progress to uremia.
Place the following into the correct order to represent the RAA mechanism.
Angiotensin II Vasoconstriction Elevated blood pressure Angiotensin I Angiotensinogen ACE Aldosterone Renin Drop in blood pressure
Chloride (Cl-), Bicarbonate (HCO3-), and phosphates (Pi) are examples of what?
Anions
Place the following vessels in the correct order to represent the arterial circulation leading up to the glomerulus
Aorta Cortical radiate artery Afferent arteriole Interlobar artery Segmental artery Renal artery Arcuate artery
Name the three important chemical buffer systems in the body.
Bicarbonate, phosphate, and protein
Which is a cation that lends strength to the skeleton, activates muscle contraction, serves as a second messenger for some hormones and neurotransmitters, and is an essential factor in blood clotting?
Calcium
Indicate whether the given act would create water retention or water loss in the body.
Causes water retention: -ADH hypersecretion -dry mouth -renin release -ingestion of water -hyperkalemia Causes water loss: -exercise in a warm climate -aldosterone hyposecretion -increase bp -hyponatremia -decreased renal tubular reabsorption of water
Respiratory compensation involves correcting a pH imbalance by which of the following mechanisms?
Changing pulmonary ventilation rate
What is the most abundant anion in the extracellular fluid?
Chloride
Which ions are the most abundant anions of the ECF and thus make a major contribution to its osmolarity?
Chloride
When is a person in a state of fluid balance?
Daily fluid gains equal losses.
___ is a general term for the process of separating wastes from the body fluids and eliminating them. It is carried out by four organ systems.
Excretion
True or false: Most of the water (65%) is found in the extracellular compartment.
False
True or false: Most of the water (65%) is found in the extracellular compartment.
False The greatest percentage of the body's water is in the intracellular fluid (65%).
___ is the first step of urine formation.
Glomerular filtration There is no "tubular filtration"
Glomerular filtration is highly regulated because of its influence on the amount of substances reabsorbed into the blood and the amount excreted in the urine. The glomerular hydrostatic pressure (HPg) is responsible for forcing materials through the filtration membrane from the blood into the capsular space. Two smaller forces, the blood colloid osmotic pressure (OPg) and the capsular hydrostatic pressure (HPc), work together to oppose HPg. Cumulatively, the difference between these pressures determines the net filtration pressure (NFP), which must be greater than zero for filtration to occur. In diabetes mellitus, decreased or absent insulin does not allow for certain cells in the body to take up and use glucose as an energy source. Consequently, plasma glucose levels become elevated, and this excess glucose can attach to proteins, a process referred to as glycosylation. As a result, basement membranes of a majority of capillaries around the body are thickened and hardened by deposits of glycosylated proteins. The general name for hardening or scarring of the glomeruli within the kidneys is glomerulosclerosis. In diabetic glomerulosclerosis, not only is there thickening of the basement membranes that form one of the layers of the filtration membrane, but there is also proliferation and expansion of the intraglomerular mesangial cells and associated matrix. Most proteins cannot normally cross the filtration membrane due to their large size and the negative charge of the basement membrane. During glomerulosclerosis, however, the filtration membrane becomes a less effective barrier, allowing proteins to enter into the filtrate. Thus, this is one of several conditions that leads to proteinuria, a condition in which proteins leak from blood into the urine.
Glomerular filtration is highly regulated because of its influence on the amount of substances reabsorbed into the blood and the amount excreted in the urine. By being able to control glomerular filtration, the kidney is able to control urine production based on physiologic conditions, such as the state of hydration. Glomerular hydrostatic pressure (HPg) drives the outward movement of materials from the blood into the capsular space through filtrations. Two forces oppose filtration: capsular hydrostatic pressure, and blood colloid pressure. Capsular hydrostatic pressure (HPc) occurs as the filtrate fills the capsular space, resulting in increased pressure. Differences between the osmolarity of the blood within the glomerulus and the filtrate within the capsular space are responsible for the Colloid osmotic pressure (OPg). Both of these pressures oppose the HPg. In order for filtration to occur, the overall pressure moving outward from the glomerulus to the capsular space must be greater than the combined inward pressures. The net filtration pressure is determined by subtracting the net inward pressure forced from the outward HPg. In order for filtration to occur, the net filtration pressure must be greater than zero.
The pH of a solution is determined solely by the concentration of which ion?
Hydrogen
Which term refers to a plasma sodium concentration less than 130 mEq/L
Hyponatremia
Which represents the largest fluid compartment in the body?
Intracellular fluid
Which best describes how aldosterone acts as the "salt retaining hormone"?
It increases the number of Na-K pumps in the nephron.
Which organ can neutralize more acid or base than either the respiratory system or the chemical buffers?
Kidney
Match each component of the juxtaglomerular apparatus with its description.
Mesangial cells → cells between the arterioles and amongst the glomerular capillaries Juxtaglomerular cells → smooth muscle cells within wall of afferent arteriole Macula densa cells → epithelial cells at the end of the nephron loop
Match the pH disorder with its cause.
Metabolic acidosis → Excess production of organic acids i.e. diabetes mellitus and starvation; hyperkalemia; chronic diarrhea; excessive alcohol consumption; aspirin; laxatives Metabolic alkalosis → Rare but can result from chronic vomiting; overuse of antacids; aldosterone hypersecretion Respiratory acidosis → Hypoventilation; apnea Respiratory alkalosis → Hyperventilation due to pain or emotions such as anxiety
Why can the kidneys neutralize more acid or base than any other buffer in the human body?
Only the kidneys actually expel H+ from the body.
Glucose is reabsorbed in the ___
PCT
Describe respiratory compensation in response to alkalosis.
Pulmonary ventilation rate decreases
Describe respiratory compensation in response to acidosis
Pulmonary ventilation rate increases
Correctly label the following anatomical parts of a kidney.
Pyramid of renal medulla Minor calyx Renal papilla Major calyx Renal sinus Renal column
How can the respiratory system compensate for a drop in blood H+ concentrations?
Reduced pulmonary ventilation allows CO2 to accumulate lowering the pH back to normal. Eliminating more CO2 would raise the pH, not lower it.
Select the nephron loop region that is impermeable to water and permeable to salts.
Region B
Correctly label the following components of the urinary system.
Renal vein Right kidney Inferior vena cava Left kidney Urinary bladder Ureter Renal artery Urethra
Drag each label to the appropriate position to identify whether the label is referring to properties of the respiratory or renal compensation mechanism for acid-base balance.
Respiratory compensation: -marked by hypercapnia -increased respiratory rate increases the amount of carbon dioxide expired -the faster acting compensation mechanism -useful for acute imbalances due to surprise or emotional strain -requires hyperpnea to release acid to the environment Renal compensation: -relies on the secretion of H+ -slower to respond pH imbalances but better at restoring a fully normal pH -effective at compensating for pH imbalances that last for a few days or longer
Identify the most accurate cause or outcome of the situation described on each label:
Results from ADH Release: -reduction in urine volume -increased water reabsorption from kidney tubules -increased aquaporin production -drinking water Stimulates ADH Release: -increased blood osmolarity -reduction in total body water
Excretion
The process of separating wastes from the body fluids and eliminating them from the body. It is carried out by four organ systems (respiratory system, integumentary system, digestive system, urinary system)
Which of the following describes the ureters?
They convey urine from each kidney to the bladder
True or false: A newborn baby's weight is as much as 75% water, whereas obese and elderly people's weight is as little as 45% water.
True
The tubular filtrate in the nephron loop and blood within the vasa recta run parallel but in opposite directions. This arrangement is referred to as the countercurrent exchange system. This design, together with urea recycling, is responsible for establishing the interstitial fluid concentration gradient within the medulla. The descending and ascending limbs of the nephron loop vary in permeability. The descending thin limb is highly permeable to water and impermeable to salts while the thick ascending limb is impermeable to water and highly permeable to sodium. Water moves out of tubular filtrate at the descending limb due to osmotic pressure differences between the tubular filtrate and interstitial fluid. This causes the tubular filtrate to become more and more concentrated as it descends. In contrast, the thick ascending limb is impermeable to water but actively pumps salt out of the tubular filtrate. This causes the tubular filtrate to become more and more dilute as it ascends. At the beginning of the nephron loop, the tubular filtrate is essentially isotonic to the interstitial fluid in the cortex. The countercurrent multiplier allows for the tubular filtrate to become much more concentrated (hypertonic) as it descends deeper into the medulla whereas the tubular filtrate becomes hypotonic to the cortex as it ascends and exits the nephron loop.
Unlike the other structures of the nephron, the nephron loop extends into the medullary region of the kidneys, an area of increasing osmolarity. The nephron loop maintains this interstitial fluid concentration gradient through the countercurrent multiplier, the exchange system associated with the vasa recta, and the recycling of urea. Juxtamedullary nephrons function primarily in this way The descending and ascending limbs vary in permeability. The descending limb is permeable to water, and impermeable to sodium. The ascending limb is impermeable to water and permeable to sodium. These differences in permeability dictate osmolarity changes in both the renal filtrate and the interstitial fluid. Deep in the medulla, this results in a multiplying effect of increased sodium concentration, called the countercurrent multiplier. The blood flow in the vasa recta runs opposite to the flow of the tubular fluid, resulting in the countercurrent exchange of materials between these two regions. The opposing flow encourages the movement of water out of the tubular fluid and into the blood at the descending limb, while enhancing the movement of water out of the blood and into the interstitial fluid at the ascending limb. The higher concentration of solutes in the medulla is largely influenced by the high concentration of urea in this region. Urea within the medulla enters the tubular fluid at the permeable thin segment of the ascending limb. Urea continues to travel through the outer impermeable regions of the nephron until it reaches the collecting ducts. This region is permeable to urea, allowing it to exit the tubular fluid and reenter the interstitial fluid of the medulla.
Which system buffers the greatest quantity of acid or base but requires several hours to days to exert an effect?
Urinary system
Which two organ systems form physiological buffers to help stabilize pH by controlling the body's output of acids, bases, or CO2?
Urinary system Respiratory system
The processes of reabsorption and secretion continue to alter the composition of the tubular filtrate throughout the distal convoluted tubule, collecting tubule, and collecting duct. After exiting the collecting duct, no further modification occurs as urine travels through the papillary duct, minor and major calyxes, and the renal pelvis, where urine exits the kidney. The renal pelvis flows into the ureters, through which urine is carried to the bladder. Here, it is stored and intermittently released into the urethra as it exits the body. The composition and volume of urine varies due to multiple factors, including the level of hydration, blood pressure, and hormones. The hormones aldosterone, antidiuretic hormone (ADH), and atrial natriuretic peptide (ANP) have significant influences on the amount of filtered sodium and water remaining in the urine. Adjustments in the amount of water reabsorbed directly affects urine volume, thus each of these hormones plays an important role in regulating urine volume.
Urine volume and composition vary, adjusting to maintain homeostasis. Normal urine composition is approximately 95% water and 5% solutes, including salts, nitrogenous wastes, some hormones, drugs and small amounts of ketone bodies. Once urine is emptied from the collecting ducts no further modification occurs. Urine then travels into papillary ducts that merge into calyces on its way to the renal pelvis, and ultimately to the bladder. The average daily urine output is normally 1-2L. Variation occur due to many variables including fluid intake, hormones, blood pressure, diet, body temperature, use of diuretics, diabetes, and the amount of fluid excreted by other means (e.g. heavy sweating, vomiting_. A minimum of about 0.5L of urine per day is require to eliminate the wastes from the body. (bp increase = increased urine vol./decrease=decrease) (atrial natriuretic peptide increase = increase/decrease=decrease) (fluid intake increase=increase urine/decrease=decrease) (aldosterone increase = decreased urine/decreased aldosterone=increased urine) (ADH increase=decreased urine/ADH decreased=increased urine) Specific gravity and urine pH are common measurements of urine output. Urine specific gravity typically varies between 1.003 to 1.035. If the specific gravity is too low, the urine contains few solutes and represents dilute urine; a high specific gravity represents an increased concentration of solutes. Urine pH levels also vary, typically ranging from 4.5 to 8.0, most commonly 6.0. The pigment urobilin gives urine its yellowish cast, which is most apparent when urine is concentrated. Glomerular filtration, reabsorption, and secretion are dynamic processes within the kidneys by which the blood is cleansed and urine is formed to maintain the proper homeostatic balance of the blood. In addition to urine formation, the kidneys also play a key role in helping maintain homeostatic balance of other physiological processes, such as blood pressure and blood volume.
The urinary system excretes:
a broad variety of metabolic wastes, toxins, drugs, hormones, salts, hydrogen ions, and water.
creatinine
a nitrogenous waste in the urine produced by catabolism of creatine phosphate.
uric acid
a nitrogenous waste in urine produced by the catabolism of nucleic acids
Uremia
a syndrome of diarrhea, vomiting, dyspnea, and cardiac arrhythmia stemming from the toxicity of the nitrogenous wastes. Convulsions, coma, and death can follow within a few days.
metabolic waste
a waste substance produced by the body
A tissue fluid pH below 7.35 is defined as a state of ___.
acidosis
Conditions such as hyponatremia, hypotension, and hyperkalemia stimulate the ___ to secrete aldosterone.
adrenal cortex
The enzyme renin is secreted by the ___ of the kidney from specialized cells called granular cells of the juxtaglomerular apparatus.
afferent arterioles
Normal blood pH is slightly ___.
alkaline
nitrogenous wastes
any nitrogen containing substance produced as a metabolic waste and excreted in the urine; chiefly ammonia, urea, uric acid, and creatinine.
waste
any substance that is useless to the body or present in excess of the body's needs ex: food residue in feces
The water content (as a percentage of total body weight) of a 70kg young male is which of the following?
around 55-60% of total body weight Young adult men average 55% to 60% water and women average slightly less because they have more adipose tissues.
A ___ is any mechanism that resists changes in pH.
buffer
A person is in a state of fluid ___ when daily gains and losses are equal.
balance
Oppositely, major anions include chloride, and phosphates.
bicarbonate
This area is where the filtrate is formed from the ___.
blood plasma
The renal corpuscle is composed of a glomerulus and a ___
capsule
The respiratory system excretes:
carbon dioxide, small amounts of other gases, and water.
Carbon dioxide, when present in in sufficient amounts, will bind to form ___, which is capable of dissociating into bicarbonate and hydrogen ions.
carbonic acid
Sodium, potassium, calcium and hydrogen ions are examples of which of the following?
cations
A substance that binds H+ during times of acidity and releases H+ during time of alkalinity is referred to as a ___.
chemical buffer
The volume of blood plasma from which a particular waste is completely removed in one minute is called renal ___.
clearance
Hormones can alter the amount of water reabsorbed during urine production, allowing the production of either concentration or dilute urine. This is the role of the ___ duct.
collecting
The segment of renal tubule indicated in the figure is the ___ duct
collecting
The ___ receives fluid draining from several nephrons, and carries it through the medulla to papilla.
collecting duct
Each nephron is composed of two parts: a renal ___ and a renal tubule.
corpuscle
Proteinuria occurs when the filtration membrane becomes leaky, allowing proteins to cross. This impacts the blood colloid osmotic pressure by ___ the osmolarity gradient between the blood and filtrate thereby ___ the strength of this pressure.
decreasing; reducing
Electrolyte concentration above or below the normal needed amounts can lead to ___.
disorders
The ___ arteriole carries blood from the glomerulus into the peritubular capillaries.
efferent
The ___ carried blood out of a glomerulus.
efferent arteriole
The digestive system:
eliminates food residue (which is not a process of excretion) but also actively excretes water, salts, carbon dioxide, lipids, bile pigments, cholesterol, and other metabolic wastes.
The process by which water and some solutes in the blood plasma pass from the glomerular capillaries into the capsular apces is called glomerular ___.
filtration
The process by which water and some solutes in the blood plasma pass from the glomerular capillaries into the capsular space is called glomerular ___.
filtration
In the kidney, tubular reabsorption refers to the movement of fluid and solutes where?
from the tubular fluid into the blood
The glomerulus is surrounded by which of the following?
glomerular capsule
The flow of fluid from the point where the glomerular filtrate is formed to the point where urine leaves the body is:
glomerular capsule → proximal convoluted tubule → nephron loop → distal convoluted tubule → collecting duct → papillary duct → minor calyx → major calyx → renal pelvis → ureter → urinary bladder → urethra
In glomerular filtration, blood is filtered to form ___
glomerular filtrate
In glomerular filtration, blood is filtered to form ___.
glomerular filtrate
The capillary bed fed by an afferent arteriole and drained by an efferent arteriole is a ___.
glomerulus
Within the juxtaglomerular apparatus, which cells are smooth muscle cells in the afferent arteriole?
granular cells
Major cations of the body include sodium, potassium, and ___.
hydrogen
Net filtration pressure (NFP) takes into account both blood ___ pressure and colloid osmotic pressure of the capsular fluid and capillary blood.
hydrostatic
Hyperparathyroidism can result in ___, a condition that reduces the membrane permeability to sodium and thus inhibits membrane depolarization.
hypercalcemia
When large quantities of potassium are released from the ICF following massive tissue trauma, ___ results, causing membrane potentials to be abnormally less negative due to a reduced concentration gradient.
hyperkalemia
Plasma sodium concentrations above 145 mEq/L represent ___, a condition that rarely occurs due to equal increases in water.
hypernatremia
Muscular tetanus can occur as a result of ___ brought on by illness or vitamin-D deficiency whereby the muscle and nerve membranes are hyperactive.
hypocalcemia
Due often to excess sweating, diarrhea, or vomiting, ___ causes the cell membrane to be hyperpolarized due to increased concentration gradients.
hypokalemia
The consumption of massive amounts of water in a short time frame can produce ___, resulting from a dilution of sodium in the ECF.
hyponatremia
This state will stimulate ___ osmoreceptors.
hypothalamic
Which best defines osmoreceptors?
hypothalamic neurons that respond to increased solute concentration in the extracellular fluid
Dehydration can lead to ___ blood osmolarity.
increased
Which of the following would not help reverse alkalosis?
induce vomiting
Through ___ of water, a negative feedback system is completed.
ingestion
Which describes the urethra?
it conveys urine from the bladder out of the body
match each component of the juxtaglomerular apparatus with its proposed role in renal autoregulation.
juxtaglomerular cells → dilate/constrict arterioles; release renin Mesangial cells → dilate/constrict glomerular capillaries Macula densa → monitor tubular fluid
The urinary system anterior and posterior view.
labeled
What are the three components of the juxtaglomerular apparatus?
mesangial cells juxtaglomerular cells macula densa
___ may be caused by diabetes mellitus, hyperkalemia; chronic diarrhea and excessive alcohol consumption, whereas ___ is rare and may be caused by chronic vomiting; overuse of antacids and aldosterone hypersecretion.
metabolic acidosis, metabolic alkalosis
Concentrations of these anions and cations are needed in specific amounts to maintain normal ___ of the body.
metabolism
The ___ is the entire functional unit of the kidney, consisting of the glomerulus and renal tubules
nephron
The ___ loop of the nephron acts as a countercurrent multiplier.
nephron
Macula densa cells are found on the
nephron loop
The ___ acts as a countercurrent exchanger, which maintains the concentration gradient in the renal medulla's tissue fluid.
nephron loop
These regions include the proximal and distal convoluted tubules and the ___.
nephron loop
Which segment of the renal tubule acts as a countercurrent multiplier?
nephron loop It has two limbs with fluid flowing in opposite directions (countercurrent) and it "multiplies" the salinity of the medulla by acting salt to the ECF.
Electrolytes are physiologically important because they affect electrical potential across membranes and contribute to ___ of body fluids.
osmolarity
Fluid intake is governed by thirst and it is regulated by a group of hypothalamic neurons called ___, which respond to angiotensin II and to rising osmolarity of the ECF.
osmoreceptors
If a local imbalance between the intracellular and extracellular fluid occurs, water movement called ___ restores the balance. This depends on the relative concentration of solutes in each compartment.
osmosis
If the osmolarity of the tissue fluid rises, water moves ___ the cells.
out of
Antidiuretic hormone provides a means of controlling water ___.
output
Slight deviations from the body's normal ___ range can shut down metabolic pathways as well as alter the structure and function of other macromolecules. Buffer systems help to avoid this.
pH
The concentration of hydrogen ions in body fluid is called ___.
pH
Which property of a solution is determined by the concentration of hydrogen ions?
pH
The ___ plays a significant role in the ICF because phosphates are capable of binding and unbinding H+, depending on current conditions of acidity or alkalinity.
phosphate buffer system
A ___ buffer is a system (for example the respiratory or urinary system) that stabilizes pH by controlling the body's output of acids, bases, or CO2.
physiological
A ___ uses direct elimination of acids, bases, or carbon dioxide from the body in order to adjust systemic acidity.
physiological buffer
The increased osmolarity of the blood stimulates the hypothalamus to stimulate the ___ pituitary to release ADH.
posterior
The kidneys lie against the ___.
posterior abdominal wall
This in turn stimulates the renal tubules to increase reabsorption of sodium and secretion of ___.
potassium
Which ion is the greatest determinant of intracellular osmolarity and cell volume?
potassium
The carboxyl ends of protein chains are capable of buffering H+ as part of the ___.
protein buffer system
ADH will work on the kidneys to ___ water into the blood stream.
reabsorb
Both will result in the ___ of water.
reabsorption
In the kidney, the process by which fluid and solutes from the tubular fluid are reclaimed and returned to the blood is called tubular ___.
reabsorption
Which structure is the filtration apparatus comprised of the glomerulus and its capsule?
renal corpuscle
A nephron consists of what two parts?
renal corpuscle and renal tubule
Which structure is composed of a proximal convoluted tubule, nephron loop, distal convoluted tubule, and collecting duct?
renal tubule
The addition of CO2 to the body fluids raises H+ concentration and lowers pH, while the removal of CO2 has the opposite effect. This is the basis for the strong buffering capacity of which system?
respiratory
A normal respiratory rate is 12-16 breaths per minute. A sustained rate of 40-50 breaths per minute could cause ___.
respiratory alkalosis
Which describes the location of the kidneys?
retroperitoneal at the level of T12 to L3
This stimulation will lead to reduced ___ and the sense of thirst.
salivation
Which determines the direction and extent of osmosis between the intracellular and extracellular compartments?
solute concentrations in the various compartments
corticomedullary junction
the boundary between the cortex and medulla
The primary function of the nephron loop is to generate a medullary ECF osmotic gradient that allows for what?
the concentration of urine
Blood urea nitrogen (BUN)
the expression of the level of nitrogenous waste in the blood. The normal concentration of blood urea is 10 - 20 mg/dL.
What is tubular secretion?
the movement of water and solutes from the blood into the tubular fluid
What is the primary function of the distal convoluted tubule and collecting duct?
the reabsorption of water and salts
Urine flows from the renal pelvis directly into ___.
the ureter
Glomerulosclerosis results in a ___ of the basement membrane.
thickening
What is the role of the collecting ducts?
to adjust the concentration of urine
___ moves substances from tubular fluid to blood.
tubular reabsorption
Aspirin, penicillin, and other drugs are cleared from the blood via the kidneys by which of the following processes?
tubular secretion
Leading away from the corpuscle is the renal ___, which consists of three regions.
tubule
The renal pelvis of each kidney funnels urine into a tube called a ___.
ureter
Urine is conveyed out of the body by a tube called the ___.
urethra
Of the two major physiological buffer systems, the respiratory system can restore the pH quickly, whereas the ___ system can take several hours to days to restore the pH.
urinary
The ___ recta within the medulla of the kidney acts as a countercurrent exchanger.
vasa
Which structure acts as a countercurrent exchanger?
vasa recta
Which structure is the capillary bed that parallels the nephron loop?
vasa recta
A negative feedback system is used until the blood ___ and osmolarity return to normal levels.
volume
The integumentary system excretes:
water, inorganic salts, lactate, and urea in the sweat.