Renal Fascia

-outer layer of dense fibrous connective tissue
-anchors kidney and adrenal gland to surrounding structures

Perirenal Fat Capsule

-fatty mass surround the kidney
-cushions against blows
-holds it against wall

Fibrous Capsule

-prevents infections in surrounding regions from spreading to the kidneys

What are the 3 distinct regions of the kidney?

1. cortex
2. medulla
3. pelvis

Renal Cortex

-granular appearance
-filled with nephrons which are the functioning unit of the kidney

Renal Medulla

-darkish, reddish brown
-deep to cortex
-pyramids

Renal Pyramids

-cone shaped tissue masses
-made up of collecting tubules and capillaries
-tip of them is the papilla

Renal Columns

-separate the renal pyramids

Renal Pelvis

-funnel shaped tubed continuous with ureter leaving the hilum
-form major calyces which subdivide into minor calyces which collect urine that drains from the papilla thru the pelvis into the ureter to the bladder to be stored

What helps to propel urine by peristalsis?

-smooth muscle that contracts rhythmically to propel urine

Renal Arteries

-divides into 5 segmental arteries and branches to form lobar and the interlobar arteries

What are the branches of the arteries?

-renal arteries
-segmental arteries
-lobar arteries
-interlobar arteries
-arcuate arteries
-small cortical radiate arteries (interlobular arteries)
-afferent arterioles

What is the branches of the veins?

-renal cortex
-cortical radiate
-arcuate vein
-interlobar
-lobar
-renal vein
-empty into inferior vena cava

Renal Plexus

-network of autonomic nerve fibers, ganglia
-provides nerve supply for the kidney and ureter
-supplied by sympathetic fibers which regulate blood flow by adjusting diameter and influencing the formation of urine by the nephron

What is the path of blood flow thru the renal blood vessels?

-aorta-renal artery-segmental artery-lobar arter-interlobar artery-arcuate artery-cortical radiate artery-afferent arteriole-glomerulus (capillaries)-efferent arteriole-vasa recta-cortical radiate vein-arcuate vein-interlobar vein-lobar vein-renal vein-inferior vein cava

Nephron

-structural and functional units of the kidneys
-carry out processes that form urine
-contains a renal corpuscle and tubule

Renal Corpuscle

-consists of tuft of capillaries called the glomerulus and Bowman's capsule

Bowman's Capsule

-completely surrounds the glomerulus

Glomerulus Endothelium

-fenestrated
-exceptionally porous
-allows large amounts of solute-rich to pass from blood into the capsule
-filtrate

Filtrate

-plasma derived fluid
-raw material that the renal tubules process to form urine
-contains everything found in the blood plasma except proteins

What are the 2 layers of the Bowman's Capsule?

1. parietal layer
2. visceral layer

Parietal Layer of the Bowman's Capsule

-simple squamous epithelium
-contributes to the structure, but not the formation of filtrate

Visceral Layer

-contains podocytes

Podocytes

-highly modified, branching epithelial cells
-terminate in the foot processes which cling to the basement membrane
-contains openings between the foot processes called filtration slits which helps filtrate enters the capsular space
-provide for filtration and protect capillaries

What are the 3 major parts of the renal tubule?

1. proximal convoluted tubule
2. nephron loop
3. distal convoluted tubule

Renal Tubule

-increases in length and enhances its filtrate processing capabilities
-single layer

Proximal Convoluted Tubule

-cuboidal epithelial cells
-bear dense microvilli which increase surface area and capacity for reabsorption of water and solutes from the filtrate and secreted substances
-bowman's capsule connects directly to here

Nephron Loop

-AKA the loop of Henle
-descending and ascending limbs
-thick ascending limb
-thin descending limb

Distal Convoluted Tubule

-thinner than the PCT and lack microvilli

Collecting Duct

-principal cells and intercalated cells
-receives filtrate from nephrons
-run thru medullary pyramids
-as they approach the renal pelvis, fuse together to deliver urine thru minor calyces by the papilla

What are the 2 types of cells found in the collecting ducts?

1. principal cells
2. intercalated cells

Principal Cells

-short microvilli
-maintain body's water and sodium balance

Intercalated Cells

-abundant microvilli
-types A and B
-maintain acid base balance of the blood

What 2 classes are nephrons divided into?

1. cortical nephrons
2. juxtamedullary nephrons

Cortical Nephrons

-85% in the kidneys
-located entirely in the cortex

Juxtamedullary Nephrons

-close to the cortex medulla junction
-play a role in the kidneys' ability to produce concentrated urine
-loop of henle that deeply invades the medulla
-extensive thin segements
-draws a lot of water in due to the long loop of henle
-associated with the vasa recta

What 2 capillary beds is the renal tubule of every nephron associated with?

1. glomerulus
2. peritubular capillaries

Glomerulus

-specialized for filtration
-both fed and drained from arterioles (afferent and efferent)
-helps to maintain high pressure needed for filtration
-efferent arterioles feed into peritubular capillaries or vasa recta

What percentage of fluid produced by filtration is reabsorbed by the renal tubule cells and returned to the blood in the peritubular capillary beds?

-99%

Peritubular Capillaries

-cling to renal tubules
-empty into venules
-low pressure so they can readily absorb solutes and water from the tubule cell as they are reclaimed from the filtrate

Vasa Recta

-efferent arterioles from these long straight vessels that extend deep into the medulla paralleling the loop of henle
-form concentrated urine
-ladder affect signaling exchanges

Why do the particular capillary beds need low pressure?

-we need to be able to absorb and secrete the correct amount

Why is pressure high in the glomerulus?

-arterioles are high resistance vessels
-to push out filtrate

What would stop you from making filtrate?

-destruction of bowman's capsule

Juxtaglomerular Complex (JGC)

-region where the most distal portion of the ascending limb of henle lies against the afferent arteriole feeding the glomerulus

What are the 3 cells in the JGC?

1. macula densa
2. granular cells
3. extraglomerular mesangial cells

Macula Densa

-tall, closely packed cells in the ascending limb
-chemoreceptors that monitor NaCl content of the filtrate entering the distal convoluted tubule
-osmoreceptors

Granular Cells

-are in the arteriolar walls
-enlarged smooth muscle cells with secreting granules containing renin
-mechanoreceptors that sense the BP in the afferent arteriole

Mesangial Cells

-between the arteriole and tubule cells
-interconnected by gap junctions
-pass regulatory signals between macula dense and granular
-digest proteins that are on the filtration membrane
-influence capillary filtration
-

What does resistance in afferent arterioles do?

-protects glomeruli from fluctuations in systemic blood pressure
-if it constricts, it slows down the blood flow which brings down the blood pressure

What does resistance in efferent arterioles do?

-reinforces high glomerular pressure
-reduces hydrostatic pressure in peritubular capillaries
-if this constricts it bring the pressure up

What are the 3 processes of urine formation?

1. glomerular filtration
2. tubular reabsorption
3. tubular secretion

Glomerular Filtration

-takes place in the renal corpuscle and produces a cell and protein free filtrate
-glomerulus to bowman’s capsule

Tubular Reabsorption

-process of selectively moving substances from the filtrate back into the blood
-takes place in the renal tubules and collecting ducts
-anything that is not reabsorbed becomes urine
-tubules to arterioles

Tubular Secretion

-process of selectively moving substances from the blood into the filtrate
-secretion into tubular

Urine

-contains uneeded substances such as excess salts and metabolic wastes

Glomerular Filtration

-passive process in which hydrostatic pressure forces fluids and solutes thru a membrane
-filtration membrane is more permeable
-high BP
-higher net filtration pressure
-plasma proteins are not filtered and are used to maintain oncotic pressure of the blood
-albumin

Filtration Membrane

-lies between the blood and the interior of the glomerular capsule
-porous membrane that allows free passage of water and solutes smaller than plasma proteins
-fused to podocyte

What are the 3 layers of the filtration membrane?

1. fenestrated endothelium
2. basement membrane
3. foot processes of podocytes of the glomerular capsule

Fenestrated Endothelium

-allow all blood components except blood cells to pass thru

Basement Membrane

-between the other two layers
-blocks all but the smallest proteins while permitting solutes to pass
-glycoproteins give it a negative charge
-

Foot Processes of Podocytes of the Glomerular Capsule

-contain filtration slits between their foot processes
-slit diaphragms: thin membranes that extend across the filtration slits that prevent almost all macromolecules of the them traveling farther

What does keeping the plasma proteins in the capillaries do?

-maintains the colloid osmotic (oncotic) pressure of the glomerular
-prevents loss of all its water
-prescence of proteins or blood cells in the urine usually indicates a problem with the filtration membrane

What two outward pressures affect filtration?

1. hydrostatic pressure in glomerular capillaries
2. colloid osmotic pressure in the capsular space

Hydrostatic Pressure in Glomerular Capillaries

-glomerular blood pressure
-chief force pushing water and solutes out of the blood and across the filtration membrane
-high and remains high across the entire capillary bed

How does the glomerular blood pressure stay high?

-glomerular capillaries are drained by a high resistance efferent arteriole that feeds them
-filtration occurs along entire length of each glomerular capillary and reabsorption does not occur as it would

Colloid Osmotic Pressure in the Capsular Space

-pull filtrate into the tubule

What are the two inward pressures that inhibit filtrate formation?

1. hydrostatic pressure in the capsular space
2. colloid osmotic pressure in glomerular capillaries

Hydrostatic Pressure in Capsular Space

-pressure exerted by filtrate
-much higher than hydrostatic pressure surrounding most capillaries because filtrate is confined in a small space with a narrow outlet

Colloid Osmotic Pressure in Glomerular Capillaries

-pressure exerted by the proteins in the blood

Net Filtration Pressure

-largely determines the glomerular filtration rate
-blood pressure is influenced by this
-the glomerular hydrostatic pressure – oncotic pressure of glomerular blood combined with the capsular hydrostatic pressure
-can be controlled by changing the diameter of the afferent arterioles

Glomerular Filtration Rate

-volume of filtrate formed each minute by the combined activity of all 2 million glomeruli of the kidneys
-proportional to the net filtration pressure
-proportional to total surface area available for filtration
-proportional to filtration membrane permeability

Total Surface Area Available for Filtration

-glomerulus capillaries have a huge surface area
-can fine tune GFR by contracting to adjust the total surface area available for filtration

Filtration Membrane Permeability

-thousands of times more permeable than other capillaries because of their fenestrations

What happens if the GFR is damaged or scarred?

-affects the rate of things going thru it
-decrease GFR
-proteins show up in the urine

What influences NFP?

-BP, GFR
-GFR is directly proportional to the NFP
-changes in the GFR normally results from changes in the glomerular blood pressure

What happens if GFR is too high?

-needed substances cannot be reabsorbed quickly enough an are lost in the urine

What happens if GFR is too low?

-everything is reabsorbed, including wastes that are normally disposed of

What 2 controls help regulate glomerular filtration?

1. intrinsic controls (renal autoregulation)
2. extrinsic controls

Renal Autoregulation

-adjusting its own resistance to blood flow
-kidney can maintain a nearly constant GFR despite fluctuations in systemic arterial blood pressure

What are the 2 types on renal auto regulation?

1. myogenic mechanism
2. tubuloglomerular feedback mechanism

Myogenic Mechanism

-contracts when stretched and relaxes when not stretched
-rising BP stretches vascular smooth muscle in the arteriolar walls, causing the afferent arterioles to constrict
-which restricts blood flow into the glomerulus and prevents glomerular blood pressure from rising to damaging levels
-low BP causes dilation of afferent arterioles and raises glomerular hydrostatic pressure

Tubuloglomerular Feedback Mechanism

-directed by the macula dense of the juxtaglomerular complex
-responde to filtrate NaCl concentration

What happens when GFR increases?

-not enough time for reabsorption and the concentration of NaCl in the filtrate remains high
-macula dense cells respond by releasing vasoconstrictor chemicals that cause intense constriction of the afferent arteriole
-reduce blood flow into glomerulus
-decreases the NFP and GFR, which slows the flow of filtrate and allowing more time for filtrate processing

What happens if there is a low concentration of NaCl?

-slow flowing filtrate inhibits ATP release from macula dense cells
-causes vasodilation of the afferent arterioles
-allows more blood to flow into the glomerulus
-increasing NFP and GFR

What are the 2 extrinsic controls?

1. sympathetic nervous system controls
2. renin angiotensin aldosterone mechanism

Sympathetic Nervous System Controls

-when the volume of the ECF is normal and sympathetic is at rest, renal blood vessels are dilated
-when ECF is low (hypovolemic shock), shunt blood to organs and neural controls override auto regulatory mechanisms
-reduce renal blood flow

What happens when blood pressure falls?

-norepinephrine is released by sympathetic nerve fibers and epinephrine is released by medulla which causes vascular smooth muscle to constrict
-increase peripheral resistance
-which brings BP up

Renin Angiotensin Aldosterone Mechanism

-bodys main mechanism for increasing blood pressure

What 3 pathways of the low blood pressure causes the granular cells to release renin?

1. direct stimulation of granular cells
2. stimulation of the granular cells by input from activated macula densa cells
3. reduced stretch granular cells

Direct Stimulation of Granular Cells

-cause the granule cells to release renin

Stimulation of the Granular Cells by Input from Activated Macula Densa Cells

-low BP (vasoconstriction) of the afferent arterioles by the sympathetic nervous system reduces GFR
-slows down the flow of filtrate thru the renal tubules
-when macula dense cells sense low NaCl concentration, signal granular cells to release renin
-release less ATP

Reduced Stretch of Granular Cells

-granular cells act as mechanoreceptors
-a drop in arterial pressure reduces the tension in the granular cells' plasma membranes and stimulates them to release more renin

Prostaglandin

-vasodilators produced in response to sympathetic stimulation and angiotensin II
-are thought to prevent renal damage when peripheral resistance is increased

Nitric Oxide

-vasodilator produced by the vascular endothelium

Adenosine

-vasoconstrictor of renal vasculature
-works when BP is high

Endothelin

-a powerful vasoconstrictor secreted by capillary cells
-raise systemic BP

Tubular Reabsorption

-quickly reclaims most of the tubule contents and returns them to the blood
-begins as soon as the filtrate enters the proximal tubules

Active Tubular Reabsorption

-requires ATP either directly (primary active transport) or indirectly (secondary active transport)

Passive Tubular Reabsorption

-encompasses diffusion, facilitated diffusion, and osmosis
-move down their electrochemical gradients

Sodium Transport Across the Basolateral Membrane

-Na is transported out of the tubule cell by primary active transport
-water sweeps Na into adjacent peritubular capillaries
-low hydrostatic pressure and high osmotic pressure

Sodium Transport Across the Apical Membrane

-active pumping of Na from the tubule cells results in a strong electrochemical gradient that favors its entry at the apical via secondary active transport
-pump maintains the intracellular Na concentration low levels
-K pumped into tubules diffuse into interstitial fluid

Transcellular Route

-transported substances move through the apical membrane, cystol, basolateral membrane of the tubule cell and then endothelium to the peritubular capillaries

Paracellular Route

-between the tubule cells

Secondary Active Transport

-created by NaK pump
-glucose, amino acids, ions, and vitamins
-Na moves down its concentration gradient

Passive Tubular Reabsorption of Water

-movement of Na establishes a strong osmotic gradient, water moves by osmosis into the peritubular capillaries
-aquaporins

Aquaporins

-aid passive tubular reabsorption of water
-act as water channels across cell membranes
-always present in the tubule cell membranes
-PCT

Obligatory Water Reabsorption

-presence of aquaporins obliges the body to absorb water in the proximal nephron regardless of over or under hydration

Why does glucose show up in the urine?

-pass it thru the kidneys and pushes out through the kidney and then we reabsorb most of it, but why does it go into the urine?
-because in the luminal membrane, you have a transport maximum, only a certain number of glucose receptors
-void out the glucose because it can’t take as much
-lack spaces in the membrane to absorb it
-because of TM

Facultative Water Reabsorption

-water reabsorption that depends on ADH

Transport Maximum

-for nearly every substance that is reabsorbed using a transport protein in the membrane
-reflects number of transport proteins in the renal tubules available to carry a substance

PCT and Mechanism

-reabsorb glucose, amino acids, and Na and water
-electrolytes
-uric acid and urea

Nephron Loop and Mechanism

-water
-Na Cl K
-Ca Mg

DCT and Mechanism

-Na Cl
-Ca

Collecting Duct

-Na K HCO Cl
-water
-urea

What is the water rule concerning the ascending and descending limb?

-leaves the descending but not the ascending
-opposite for solutes, not absorbed in the descending, but both in the ascending

ADH

-anti diuretic hormone
-urine output
-makes the principal cells of the collecting ducts more permeable to water by causing aquaporins
-ADH determines number of aquaporins which results in how much water is reabsorbed
-increases urea reabsorption by collecting ducts

What happens when the body is over hydrated?

-ECF osmolarity decrease
-decrease ADH secretion
-makes ducts impermeable to water

Aldosterone

-reabsorption of the remaining Na
-little to no urine leaves the body
-increase blood volume, BP by enhancing Na reabsorption
-reduces K concentrations
-Na enter, K moves out

Hyperkalemia

-decrease blood volume or blood pressure
-causes adrenal cortex to release aldosterone to the blood

Atrial Natriuretic Peptide

-reduces blood Na, decreasing blood volume, decreasing BP

Parathyroid Hormone

-increases reabsorption of Ca

Tubular Secretion

-reabsorption in reverse
-moves selected substances (H, K, NH, creatinine) from the peritubular capillaries thru the tubule cells into the filtrate

What 4 ways is tubular secretion important?

1. disposing of substances
2. eliminating undesirable substances
3. ridding the body of excess K
4. controlling blood pH

Disposing of Substances

-plasma proteins are not filtered, so they substances they bind to are not filtered so they must be secreted

Eliminating Undesirable Substances

-urea and uric acid

Ridding the body of Excess K

-all K is reabsorbed
-all K in urine comes from aldosterone drive active tubular secretion

Controlling Blood pH

-renal tubule cells secrete more H into the filtrate and retain and generate HCO
-blood pH rises and the urine drains of the excess H
-when its too basic, Cl is reabsorbed

What are the 2 countercurrent mechanisms that determine urine concentration and volume?

1. countercurrent multiplier
2. countercurrent exchanger

Countercurrent multiplier

-interaction between the flow of filtrate thru the ascending and descending limbs of the loop of Henle

Countercurrent Exchanger

-flow of blood thru ascending and descending parts of the vasa recta

Medullary Osmotic Gradient

-countercurrent mechanisms that establish and maintain an osmotic gradient extending from the cortex thru the depths of the medulla
-allows kidneys to vary urine concentration

Countercurrent Multiplier

-descending loop of Henle:
-is relatively impermeable to solutes except fro water
-is permeable to water
→ the ascending loop of Henle
-is permeable to solute
-is impermeable to water
-collecting ducts in the deep medullary regions are permeable to urea

Countercurrent Exchanger

-preserves medullary gradient
-prevents rapid removal of salt from the medullary interstitial space
-removes reabsorbed water
-volume of blood at the end of the vasa recta is higher than at the beginning

Formation of Diluted Urine

-overhydrated, ADH production decreases and the osmolarity of urine falls
-if aldosterone is present, the DCT and collecting ducts can removed Na and dilute more
-dehydrated, ADH is released and solute concentration of urine increases

Formation of Concentrated Urine

-ADH inhibits diuresis
-99% of the water in filtrate is reabsorbed due to an increased number

Diuretics

-chemicals that enhance the urinary output include:
-any substance not reabsorbed
-substances that exceed the ability of the renal tubules to reabsorb it
-substances that inhibit Na reabsorption
-diuretics

What are 4 types of diuretics?

- high glucose levels: carries water out with the glucose
-alcohol: inhibits the release of ADH
-caffeine and most diuretic drugs: inhibit Na ions (furosemide or Lasix) and -Diruil; inhibit Na associated symporters in the ascending loop of Henle so you cannot establish a medullary gradient
-people take it:
-lose weight
-hypertension high BP because they void out water
-CHF
-Congestive heart failure

Renal Clearance

-refers to the volume of plasma from which the kidneys clear a particular substance in a given time

Color of Urine

-clear, plae to deep yellow
-concentrated urine has a deepr yellow color
-drugs, vitamin supplements, and diect can change the color fo urine
-cloudy urine may indicate infection of the urinary tract

Odor of Urine

-fresh urine is slightly aromatic
-standing urine develops an ammonia odor due to breakdown of urea
-some drugs and vegetables (aspargus and mercaptan) alter the usual odor

pH of Urine

-slightly acidic (pH 6) with a range of 4.5 to 8.0
-diet can alter pH

Specific Gravity of Urine

-dependent on solute concentration
-ranges from 1.0001 to 1.035
-used to tell if the person is dehyradted

Ureters

-tubes covered with smooth muscle
-carry urine to bladder

Urinary Bladder

- smooth, collapsible, muscular sac that temporarily stores urine
-males: prostate gland surrounds the neck inferiorly
-females: anterior to the vagina and uterus
-as the baby develops, it puts pressure on the bladder, so it can’t expand as much as it used to so you pee a lot
-when you go for an ultrasound of the uterus which lies underneath, drink water, so you can inflate bladder, and see it

What happens when you hold your bladder?

-when you hold you bladder, the detrusor muscle becomes strained so when you go pee, you don’t empty your bladder all the way, so wait around and drink when you get there

Trigone

- triangular area outline by the opening for the ureters and the urethra

Reflux

-urine going back into kidneys

Male Urethra

-urethra runs thru prostate gland
-prostate gland: semen formation
-prostate gland can get enlarged (BPH: benign prostatic hypertrophy) collapses the urethra causing poor streaming of urine (they can’t get it out) so they take medication to shrink it up
-urethra shares the ejaculatory duct