Renal Physiology

The kidneys maintain the body’s internal environment by regulating the _____ of the extracellular fluid, the _____, _____, and _____ of the blood, maintaining _____ balance, excreting _____, producing _____ and _____, and carrying out _____ if needed.

Volume; pressure; osmolarity; pH; ion; waste; erythropoietin; renin; gluconeogenesis

The kidneys are part of the _____ system, which also includes the ureters, which are responsible for _____ urine from the _____ to the _____; the urinary bladder, which acts as a temporary _____ reservoir for urine; and the urethra, which transports urine to the _____.

Urinary; transporting; kidneys; urinary bladder; storage; outside of the body

_____ are considered the functional units of the kidney.

Nephrons

The kidney is split into an outer _____, which contains _____ nephrons, and an inner _____, which contains _____ nephrons.

Cortex; cortical; medulla; juxtamedullary

Nephrons are comprised of two main parts: the _____ and the _____.

Renal corpuscle; renal tubule

The renal corpuscle of a _____ functions to create _____ and is located in the renal _____.

Nephron; filtrate; cortex

The renal tubule of a _____ functions to modify _____ and turn it into _____. Renal tubules begin in the _____, pass into the _____, then return back to the _____.

Nephron; filtrate; urine; cortex; medulla; cortex

Filtrate refers to _____ that is brought into a nephron, containing everything except _____. Filtrate acts as the precursor for _____.

Plasma; proteins; urine

The renal corpuscle of a _____ consists of a _____ surrounded by a _____/_____.

Nephron; glomerulus; glomerular/Bowman’s capsule

The renal tubule of a _____ consists of the _____, then the _____/_____, then the _____, then the _____.

Nephron; proximal convoluted tubule; nephron loop/loop of Henle; distal convoluted tubule; collecting duct

The renal artery divides many times, eventually leading to the _____. The afferent arteriole leads into the _____, which contains capillaries specialized for filtration. Unlike other capillary beds, these capillaries are both _____ and _____ by the afferent arteriole, making this a _____.

Afferent arteriole; glomerulus; fed; drained; portal system

Blood leaves a glomerulus via an _____ and flows into the _____.

Efferent arteriole; peritubular capillaries

Blood pressure in the glomerulus is _____ because the afferent arterioles are _____ in diameter than the efferent arterioles, and because the arterioles are high-_____ vessels.

High; larger; resistance

The two types of nephron capillary beds are _____ and _____.

Peritubular capillaries; vasa recta

Peritubular capillaries are a type of _____ that consist of porous capillaries adapted for the _____ of water and solutes. These arise from the _____ arterioles, and are found in the renal _____, carrying blood back to the _____.

Nephron capillary bed; absorption; efferent; cortex; renal veins

Vasa recta are a type of _____ that consist of long, thin-walled vessels found along the _____/_____ of nephrons in the _____. These also arise from _____ arterioles, but specifically those serving _____ nephrons. They function in the formation of _____ urine.

Nephron capillary bed; nephron loops/loop of Henle; medulla; efferent; juxtamedullary; concentrated

Glomerular filtration occurs in the _____. During glomerular filtration, fluid from the blood plasma is filtered out of the glomerular capillaries and into the _____/_____, which produces a _____ that is free of _____ and _____.

Renal corpuscles; glomerular/Bowman’s capsule; filtrate; proteins; cells

Tubular reabsorption takes place in the _____ and _____ and functions to return most of the substances found in the _____ to the _____.

Renal tubules; collecting ducts; filtrate; blood

Tubular secretion moves _____ substances from the _____ to the _____ in the _____ and _____.

Selected; blood; filtrate; renal tubules; collecting ducts

The filtration membrane is responsible for separating the _____ in the _____ from the _____ in the _____. From deep to superficial, the three layers of the filtration membrane are the _____, the _____, and the _____.

Blood; glomerular capillaries; filtrate; glomerular capsule; capillary endothelium; basement membrane; foot processes

The capillary endothelium is the _____ layer of the filtration membrane. This layer contains _____ that prevent _____ from passing.

First; fenestrations; cells

The basement membrane is the _____ layer of the filtration membrane. The basement membrane contains a _____ that prevents _____ from passing.

Second; negative charge; proteins

The foot processes of the podocytes of the _____ is the _____ layer of the filtration membrane. This layer prevents _____ from passing.

Glomerular capsule; third; macromolecules

Glomerular filtration is a _____ process.

Passive

Outward pressures refer to those that _____ filtrate formation. These include the _____ pressure in the _____ and the _____ pressure in the _____.

Promote; hydrostatic; glomerular capillaries; colloid osmotic; Bowman’s space

Hydrostatic pressure in the glomerular capillaries is a type of _____ pressure that essentially represents glomerular blood pressure. This is the _____ force pushing water and solutes out of the blood. This pressure is generally _____ because the diameter of the efferent arteriole is _____ than the afferent arteriole.

Outward; primary; high; smaller

The Bowman’s space colloid osmotic pressure is a type of _____ pressure that is normally _____ because there should not be _____ in the filtrate.

Outward; zero; proteins

Inward pressures refer to those that _____ filtrate formation. These include _____ pressure in the _____ and _____ pressure in the _____.

Inhibit; hydrostatic; Bowman’s capsule; colloid osmotic; capillaries

Hydrostatic pressure in the Bowman’s capsule is a type of _____ pressure that refers to the pressure of the _____ in the capsule.

Inward; filtrate

Colloid osmotic pressure in the capillaries is a type of _____ pressure that refers to the _____ force of _____ found in the _____.

Inward; pulling; proteins; blood

The net filtration pressure (NFP) refers to the _____ of inward and outward pressures and represents the pressure responsible for _____.

Sum; filtrate formation

Glomerular filtration rate (GFR) refers to the _____ of filtrate formed every _____ by _____ kidney(s). This is a measure of kidney function. This is approximately equal to 180 L/day, or about 45 gallons. Our total blood volume is filtered every 40 minutes, and must be _____ immediately.

Volume; minute; both; reabsorbed

GFR is directly proportional to the total _____ available for filtration, the _____ of the filtration membrane, and the _____, the latter of which is primarily affected by _____ and the most _____.

Surface area; permeability; net filtration pressure; hydrostatic pressure of the glomerular capillaries; variable

GFR remains relatively _____ over a wide range of _____.

Constant; blood pressures

GFR is controlled primarily by regulating blood flow through the _____.

Renal arterioles

GFR can increase if resistance in the afferent arteriole _____ or resistance in the efferent arteriole _____.

Decreases; increases

GFR can decrease if resistance in the afferent arteriole _____ or resistance in the efferent arteriole _____.

Increases; decreases

GFR is subject to _____, which maintains a relatively constant GFR when _____ fluctuates in the range of _____. This constant GFR is important as it allows the kidneys to continue making _____ and maintaining _____ homeostasis.

Autoregulation; MAP; 80 to 180 mmHg; filtrate; extracellular

Autoregulation helps protect the glomerular _____ from damage.

Filtration membrane

The two major autoregulatory mechanisms are the _____ and _____.

Myogenic response; tubuloglomerular feedback

The myogenic response is a type of _____ that refers to the _____ ability of the _____ in the blood vessels to respond to changes in _____.

Autoregulation; intrinsic; smooth muscles; pressure

In the myogenic response, local smooth muscle contracts in response to an _____ in blood pressure, resulting in the _____ of the blood vessels. This causes the afferent arteriole to _____, restricting blood flow _____ the glomerulus. If blood pressure _____, then the afferent arterioles _____.

Increase; stretching; vasoconstrict; into; decreases; dilate

Each nephron has one juxtaglomerular complex/apparatus, which is where the _____ of the _____ passes between the _____ and _____ near the _____. The juxtaglomerular capsule consists of the _____ and _____.

Ascending limb; loop of Henle; afferent arteriole; efferent arteriole; glomerulus; macula densa; granular cells

The macula densa that are part of the _____ contain _____ that sense the _____ content of the _____.

Juxtaglomerular complex; chemoreceptors; NaCl; filtrate

The granular cells that are part of the _____ contain _____ that sense the _____ in the _____ and contain _____, a type of _____.

Juxtaglomerular complex; mechanoreceptors; blood pressure; afferent arteriole; renin; enzyme

Tubuloglomerular feedback is a type of _____ and _____-dependent mechanism directed by the _____ cells of the _____.

Autoregulation; flow; macula densa; juxtaglomerular complex

As blood pressure and GFR increase, the flow rate of the filtrate _____. This causes reabsorption time to _____, leading to _____ levels of NaCl in the filtrate. This is detected by the _____, which release _____ in response and cause the afferent arteriole to _____, resulting in a _____ in blood pressure and GFR and _____ in reabsorption time.

Increases; decrease; high; macula densa; ATP; vasoconstrict; decrease; increase

As blood pressure and GFR decrease, the _____ cells release _____ in order to cause the afferent arteriole to _____.

Macula densa; nitric oxide; vasodilate

In addition to _____ autoregulation, _____ and _____ also influence GFR. This external factors can _____ autoregulation, especially during situations involving major changes in blood _____ and blood _____.

Local; hormones; autonomic neurons; override; volume; pressure

The _____ nervous system can influence GFR via the _____ of renal arterioles, _____ renal blood flow and _____ GFR.

Sympathetic; vasoconstriction; decreasing; decreasing

Hormones that affect GFR include angiotensin II, which results in _____, and prostaglandins, which result in _____.

Vasoconstriction; vasodilation

_____ is responsible for reclaiming most of the tubular contents and returning them to the blood.

Tubular reabsorption

About 180 L of water is filtered per day, but only 1 to 2 L is excreted as urine. This filtration increases when we are _____ and decreases when we are _____. Obligatory water loss refers to the _____ and is equal to a minimum of 400 mL.

Well-hydrated; dehydrated; minimum volume of water that must be excreted to rid the body of wastes

The _____ is the site of the most reabsorption. Reabsorption in this area is _____. Reabsorption in this area involves all _____, such as _____ and _____; most _____ and _____; many _____; and almost all _____ and some _____, which are later _____ back into the filtrate.

Proximal convoluted tubule; unregulated; nutrients; glucose; amino acids; Na+; water; ions; uric acid; urea; secreted

Reabsorption in the _____ is _____, like the proximal convoluted tubule. In the _____, water can leave, but solutes cannot. In the _____, solutes can leave, but water cannot.

Loop of Henle; unregulated; descending limb; ascending limb

Reabsorption in the _____ and _____ is regulated by _____. Antidiuretic hormone causes the cells of the _____ to insert _____ into the apical membranes, _____ water reabsorption. Aldosterone increases _____ reabsorption. Atrial natriuretic peptide is released by _____ cells if blood _____ or _____ is elevated, _____ blood sodium.

Distal convoluted tubule; collecting duct; hormones; collecting duct; aquaporins; increasing; Na+; cardiac atrial; volume; pressure; decreasing

Reabsorption can occur via a _____ route or _____ route.

Paracellular; transcellular

Paracellular reabsorption refers to when substances travel _____ cells.

Between

Transcellular reabsorption refers to when substances travel _____ cells using _____. Much transcellular reabsorption occurs through _____ using _____, which relies on the action of _____, which help maintain _____.

Through; transporters; secondary active transport; Na+; Na+/K+ pumps; concentration gradients

Reabsorption may be active or passive. _____ is absorbed via active transport. This creates an electrochemical gradient that drives _____ reabsorption, which then causes _____ to move by osmosis. Other permeable solutes such as _____ are then reabsorbed via diffusion or _____ pathways.

Na+; anion; water; urea; paracellular

The peritubular capillaries favor reabsorption because hydrostatic pressure is _____ and colloid osmotic pressure is _____, favoring movement _____ the capillaries.

Low; high; into

In the tubule lumen, Na+ is _____ and glucose is _____. In the tubule cells, Na+ is _____ and glucose is _____. In the interstitial fluid, Na+ is _____ and glucose is _____.

High; low; low; high; high; low

During sodium-linked reabsorption, Na+ moving _____ its electrochemical gradient uses the _____ to pull glucose _____ its concentration gradient via _____. Glucose can then _____ out of tubule cells using a _____ via _____, while Na+ is pumped _____ the cells using the _____ via _____.

Down; SGLT protein; against; cotransport; diffuse; GLUT protein; facilitated diffusion; out; Na+/K+ pump; primary active transport

Saturation refers to the maximum rate of renal transport that occurs when _____.

All carriers are occupied by a substrate

The transport maximum (T_m) refers to the renal transport rate at _____, reflecting the number of available _____ in the renal tubules. When carriers for a solute are _____, excess solute is excreted in the _____, e.g. _____.

Saturation; carriers; saturated; urine; glucose

Tubular secretion occurs almost completely in the _____, where select substances are _____ moved from the _____ into the _____.

Proximal convoluted tubule; actively; peritubular capillaries; filtrate

Tubular secretion is important for the disposal of certain substances, such as _____ and other metabolites, that are bound to _____; elimination of undesirable substances that were _____ reabsorbed, such as _____; ridding of excess _____ via the effects of _____; and controlling blood _____ by altering the amounts of _____ or _____ in the urine.

Drugs; plasma proteins; passively; urea; K+; aldosterone; pH; H+; HCO₃^-

Excretion is equal to _____.

Filtration - reabsorption + secretion

Urine does not change composition after leaving the _____. Urine is collected and stored in the _____ until _____, or the process of urination. Two _____ control urine flow from the bladder.

Collecting ducts; urinary bladder; micturition; sphincters

A simple spinal reflex controls micturition. _____ receptors in the walls of the bladder send signals to the spinal cord, which then cause _____ fibers to induce _____ in the bladder. At the same time, _____ neurons to the _____ are inhibited, resulting in _____. This reflex can be overridden by the _____ and _____ via _____ control.

Stretch; parasympathetic; smooth muscle contraction; somatic; external urinary sphincter; relaxation; brainstem; cortex; voluntary

The body must maintain _____ balance, meaning that what enters the body must be excreted if not needed, and maintaining _____ is critical.

Mass; extracellular fluid osmolarity (ECF)

Changes in ECF osmolarity cause _____ movement. An increase in ECF osmolarity will cause cells to _____, while a decrease in ECF osmolarity will cause cells to _____, and changes in cell _____ can impair function.

Water; shrink; swell; volume

Multiple systems integrate fluid and electrolyte balance. These include the respiratory and cardiovascular systems, which typically result in _____ responses and are under _____ control, as well as the kidneys, which typically result in _____ responses and are under _____/_____ control.

Fast; neural; slow; endocrine/neuroendocrine

Females are made of relatively _____ water than males due to their higher _____ content and lower _____ mass. The total body water in adults averages about _____.

Less; fat; skeletal muscle; 40 L

The two main fluid compartments of the body are the _____ compartment, or the fluid _____ cells, that accounts for about _____ of our total body fluid; and the _____ compartment, or the fluid _____ cells, that accounts for about _____ of our total body fluid. The latter includes _____ and the _____ found _____ cells.

Intracellular fluid (ICF); inside; 2/3; extracellular fluid (ECF); outside; 1/3; plasma; interstitial fluid; between

Our intake of water primarily occurs through _____ via food and beverages, but it can also result from _____ or _____.

Ingestion; metabolism; intravenous injection

Our loss of water primarily occurs through _____ (about 60%), _____, _____ water loss through the _____ and _____, _____, and _____ causes such as _____, _____, and excessive _____.

Urine; feces; insensible; skin; lungs; perspiration; pathological; diarrhea; vomiting; sweating

The kidneys help maintain water balance by adjusting _____. While they can _____ excess water and _____ water, they cannot _____, which must be mediated through _____.

Urine output; excrete; conserve; replace lost water; intake

Filtrate entering the _____ is considered _____ the body unless it is _____.

Nephron; outside; reabsorbed

Severe fluid loss can lead to decreases in _____ and _____.

Blood pressure; renal filtration

The renal _____ is responsible for creating _____ urine by creating a high _____, which _____ water from the _____.

Medulla; concentrated; osmotic gradient; pulls; collecting duct

The osmolarity of urine represents _____. Urine with a low osmolarity has _____ water content and is relatively _____, while urine with a high osmolarity has _____ water content and is relatively _____.

How much water is excreted in the urine; high; dilute; low; concentrated

Diuresis refers to the process of _____.

Removing excess water in the urine

The concentration of urine is primarily regulated in the _____ and _____.

Distal convoluted tubule; collecting duct

Urine becomes dilute when _____ are reabsorbed and _____ remains in the filtrate.

Solutes; water

Urine becomes concentrated when _____ is reabsorbed, which requires _____.

Water; aquaporins

As fluid flows through the nephron, it loses _____ in the descending limb of the loop of Henle via _____. Fluid then loses _____ in the ascending limb in the loop of Henle via _____. This causes fluid leaving the loop of Henle to be more _____ than the fluid entering the loop of Henle. Once fluid reaches the _____ and _____, the permeability of water is subject to _____ control.

Water; osmosis; Na+; active transport; dilute; distal convoluted tubule; collecting duct; hormonal

_____/_____ is responsible for controlling water reabsorption. This makes the _____ more permeable to water, causing water to be _____.

ADH/vasopressin; collecting duct; reabsorbed

ADH exhibits a graded effect, meaning that the _____.

Concentration of the urine is matched to the body’s needs

ADH/vasopressin activates a _____, which causes the cells of the _____ to insert _____ found in _____ into the apical membrane via _____, causing water to be reabsorbed in the blood.

cAMP second messenger system; collecting duct; aquaporins; storage vesicles; exocytosis

The most potent stimulus for ADH release is an _____. _____ in the _____ are responsible for detecting these changes and then triggering ADH release from the _____. A decrease in _____ and a decrease in _____ due to a decrease in _____ can also result in the release of ADH.

Increase in plasma osmolarity; osmoreceptors; hypothalamus; posterior pituitary; blood pressure; atrial stretch; blood volume

ADH secretion exhibits a _____ pattern, where less urine is produced at _____ than during the _____, and morning urine is more _____. Reduced ADH at _____ may contribute to _____.

Circadian; night; day; concentrated; night; bed-wetting

High medullary osmolarity creates an _____ for water reabsorption, pulling water from the _____ back into the _____. Without this gradient, water cannot leave the _____ effectively.

Osmotic gradient; nephron; bloodstream; collecting duct

The _____ creates and maintains the medullary osmotic gradient and consists of the _____ and _____.

Countercurrent system; loop of Henle; vasa recta

Osmolarity is equal to _____.

Osmoles of solute divided by liters of water

Within the countercurrent system, the loop of Henle is responsible for _____ the gradient and acting as countercurrent _____. The vasa recta is responsible for _____ the gradient and acting as countercurrent _____. The collecting ducts are responsible for _____ the gradient to adjust _____.

Creating; multipliers; preserving; exchangers; using; urine osmolarity

The loop of Henle acts as a countercurrent _____. The descending limb is permeable to _____, allowing _____ to leave via _____ and the filtrate to become _____. The ascending limb is permeable to _____, allowing _____, _____, and _____ to leave via _____. This causes the medulla to become _____ and the filtrate to become _____.

Multiplier; water; water; osmosis; concentrated; solutes; Na+; K+; Cl-; active transport; hyperosmotic; dilute

The loop of Henle has a multiplier effect when the _____ creates the medullary gradient, causing the _____ to respond by losing water. _____ filtrate travels to the _____, and the gradient is progressively amplified the _____ filtrate flows into the medulla. This creates an _____ that enables water reabsorption in the _____.

Ascending limb; descending limb; concentrated; ascending limb; deeper; osmotic gradient; collecting duct

The vasa recta is responsible for _____, preventing the _____ of the medullary osmotic gradient.

Removing water; dilution

The vasa recta acts as a countercurrent _____, as it is _____ permeable to water and solutes. The vasa recta removes reabsorbed _____ while also preserving medullary _____.

Exchanger; highly; water; solutes