A&P 2: Renal Flashcards
What are the 8 functions of the kidneys?
Ionic composition Blood pH Blood volume BP Blood osmolarity Hormones Blood glucose
What ions does the kidney help regulate?
Na K Ca2 Cl HPO42
Kidney’s regulate blood pH by excreting __ ions and saving __ ions
Excrete- H
Saves- HCO3
Kidney’s maintain a relatively constant osmolarity close to ____
300 mOsm/L
What are three hormones the kidney excretes and their function?
Renin- inc Bp
Calcitriol- inactive Vit D
Erythropoietin- stims RBC production
What can the kidney use, similar to the liver, to help maintain blood glucose levels?
AA glutamine for gluconeogenesis
What are the 4 wastes the kidney excretes and where do the waste products come from?
Ammonia/urea- deamination of aa
Bilirubin- Hgb catabolism
Creatinine- breakdown of creatinine in muscles
uric acid- nucleic acid catabolism
Where are kidneys located within the body?
Retroperitoneal space
Between T12-L3
Protected by 11 and 12 rib
What are the 3 external layers of the kidney and what are their functions?
Renal fascia- dense CT that anchors in place
Adipose capsule- protects and holds in place, surrounds capsule
Renal capsule- protective smooth transparent CT, continuous w/ ureters, maintains kidney shape
What does the term Cortex encompass?
Contains all glomeruli and convoluted tubules of nephrons
Makes columns between pyramids
What does the term Medulla encompass ?
Contains LoH and collecting ducts
Collection of ALL renal pyramids
Pyramids belong to what part of the kidney?
How many are in each kidney?
Portion of medulla
8-18/kidney
What does the term Papilla encompass?
Narrow apex of pyramid
Contains papillary duct leading to minor calyx
What does the term Columns encompass?
Space between renal pyramids
Portion of renal cortex
Function of Lobe?
What structures make up a “lobe”?
Functional region of the kidney
Pyramid medulla + cortex + 1/2 of adjacent column (cortex)
Function of Minor Calyx?
How many are in each kidney?
Small urine collection chambers from papilla
8-18/kidney
Function of Major Calyx?
How many per kidney?
Larger chamber for collecting urine from minor calyces
2-3/kidney
Major Calyx are extensions of what structure?
Ureters
Function of Renal Pelvis?
Collection point from major calyces
Mixes all urine from entire kidney
Connects to ureter outside of kidney
What is the Renal Sinus?
Spaces of adipose tissue w/ blood and nerves
What structure meet the kidney at the Renal Hilum?
Ureter emerges
Blood/lymph vessels
Nerves
Renal blood flow is ______mL/min
1200
600mL/kidney
What is the total amount of blood in adults?
4500-5500mL
What is the specialized capillary inside of the kidneys and what is it’s function?
Glomerulus, tufted
Allow filtration, no reabsorption
What is the sequence of blood flow from Aorta->kidney-> heart?
Aorta Renal Artery Segmental Artery Interlobar artery Arcuate Artery Interlobular arter Afferent Arteriole Glomerulus Vasa Recta (jux nephrons only) Interlobular Vein Arcuate Vein Interlobar Vein Renal Vein Inferior Vena Cava ARS IAI AGE PVI AIR I
Interlobular arteries are AKA ?
Interlobular veins are AKA ?
Radial arteries
Radial veins
How does blood enter and exit the kidney to be filtered?
Enters corpuscle, filtered in glomerulus, exits corpuscle into capillary system
When blood is in the ______ capillaries, it still has the same properties as blood in any other body location
Pertibular capillaries/vasa recta
The pressures in the pertibular capillaries/vasa recta allows for what mechanism?
Secondary filter
Where is filtrate first found?
Where does it flow to after?
Glomerular capsule (Bowmans's capsule) Tubule->collecting ducts
Filtrate is not called urine until it leaves what structure?
Collecting ducts
What has a larger diameter, Afferent or Efferent arteriole?
Afferent- larger
Efferent- smaller, forms back pressure
What is the functional unit of the kidney?
Nephron
What are the two parts of a nephron?
Renal Corpuscle
Renal Tubule
What are the two parts of the Renal Corpuscle?
Glomerulus
Glomerular Capsule
What are the three parts of the Renal Tubule?
PCT- attached to capsule
LoH- middle
DCT- distant from capsule, empties into collecting ducts
Corpuscle and both convoluted tubules reside in the ______
Cortex
Only the ____ extends into the renal medulla
LoH
What are the two types of nephrons?
Cortical nephron
Juxtamedullary nephron
What type of nephron is the majority?
Cortical- 85%
What are the subcomponents of the Cortical Nephron?
Renal corpuscles lie in outer portion of renal cortex
Short LoH, barely dips into medulla before returning to renal medulla
Peritubular capillaries only
What are the subcomponents of Juxtamedullary nephrons?
Renal corpuscles that lie deep in cortex
Long LoH
Peritubular capillaries that give rise to Vasa Recta
Justamedullary nephrons make up __% of total nephrons?
15%
What is the Vasa Recta of the Jux. Nephrons?
Capillary bed that extends into medulla surrounding the LoH
How do Cortical peritubular capillaries return back to systemic circulation?
After proximal/convoluted tubules, flow into interlobular veins, then to systemic circ.
What part of the kidney causes dilute or concentrated urine?
Juxtamedullary nephron long LoH
How do Juxtamedullary peritubular capillaries return to systemic circulation?
Vasa Recta- goes deep into renal medulla along LoH
Allows flow out of capillaries into filtrate and out of filtrate into capillaries
What kidney structure is extremely important for keeping a constant osmotic pressure gradient?
Juxtamedullary Vasa Recta
What are the characteristics of the Afferent Arteriole?
Arteriole into corpuscle/glomerulus
Wider lumen, thicker walls w/ greater capability to constrict/dilate
What are podocytes?
Modified simple squamous epitherlial cells w/ projections (pedicels) that wrap around glomerular capillaries
What is the ball of twine-like capillary structure that buds off an afferent arteriole?
Glomerulus
What are the characteristics of the Efferent Arteriole?
Arteriole leaving corpuscle/glomerulus
Brings blood w/ larger solutes into peritubular capillaries and back into systemic circulation
Have a smaller lumen and thinner walls which aids in back-pressure needed for filtration
A single layer of epithelial cells forms the entire wall of what three things?
Glomerular Capsule
Renal Tubule
Ducts
What is the histology of the PCT?
Sinple cuboidal w/ microvili on the apical surface (facing the lumen)
What is the histology of the LoH?
Think descending and ascending made of simple squamous
Thick ascending- simple cuboidal to columnar
Histology of the DCT?
Most- simple cuboidal
Last part- Principal cells: receptors for ADH and aldosterone; Intercalated cells- role in blood pH
What is the histology of the Collecting Duct?
Simple cuboidal w/ principal and intercalated cells
What two places are Principal and Intercalated cells located?
Last part of DCT
Collecting Duct
What are the 3 functions nephrons and collecting ducts perform?
Glomerular filtration
Tubular reabsorption
Tubular secretion
Define Glomerular Filtration
Water and solutes in blood moves across glomerulus wall into Bowmans capsule and into tubules
Define Tubular Reabsorption
Water and solutes in tubule system can be reabsorbed
How much of filtrate is reabsorbed and where does it happen?
99% in tubular reabsorption
Define Tubular Secretion?
Peritubular capillaries and vasa recta give final chance for wastes to be transferred into filtrate
Adults make ___ L of filtrate per day compared to a normal urine output of ___ L
150-180L/day of filtrate
1-2L of urine
What form the leaky barrier in the capsule?
What is it’s function?
Glomerular capillaries and podocytes
Allows water/solutes to pass into capsular space
Prevents- proteins, RBCs, platelets from getting into capsular space
What are the 3 layers of the filtration membrane?
Fenestrations of endothelial cells- prevents blood from passing
Basement membrane/Basal lamina- prevents large proteins from passing
Slit membranes between pedicels- prevents filtration of most other proteins
What are Mesangial Cells and what are their function?
Glomerular capillaries
Regulate surface area for filtration
Relaxed= max SA
Contracted= reduced SA
Define GBHP
Glomerular blood hydrostatic pressure- pressure in glomerulus pushing outward into capsular space
Define CHP
Capsular hydrostatic pressure- pressure by fluid in capsular space pushing inward on visceral glomerular membrane, “back pressure”
Opposing filtration pressure
Define BCOP
Blood colloid osmotic pressure- pressure due to proteins (albumin) in blood plasma
Pulls on fluid to keep them in glomerulus
Opposes filtration
Define NFP and the equation
Net Filtration Pressure NFP= GBHP-CHP-BCOP NFP pressure is supposed to promote filtration \+ = filtration - = no filtration
Normal NFP is the pressure that causes a normal amount of ____ to filter from ____->______
blood plasma
glomerulus
capsular space
What is the average GFR for an adult?
What happens if it’s too fast?
Too slow?
125mL/min
amount of blood filtered by kidney’s glomeruli into capsular space per time
Fast= filtrate passes too quickly, substances not reabsorbed
Slow= all filtrate reabsorbed and wastes no excreted efficiently
How is GFR calculated?
Estimation
Serum creatinine levels plus age, race, weight, gender
How is a creatinine clearance test conducted?
What if it’s low?
With 24 hour urine collection sample
Low urine level= kidney’s not filtering creatinine correctly, kidney damage
What patient population has a higher serum creatinine level?
Afro-Caribbean due to increased muscle mass and higher rates of muscle breakdown
21% higher than normal level for non-black PTs
GFR is directly related to what?
Pressures that determine net filtration pressure
If GBHP drops by even 10mmHg, what happens to filtration?
Filtration in glomerulus stops
What are mechanisms that regulate GFR?
Renal auto regulation- innate w/in kidney
Neural regulation- SNS input/lack of
Hormonal- Angiotensin II, ANP
Kidneys help regulate their own GFR through what two mechanisms?
Myogenic mechanism- increased BP causes afferent stretching, smooth muscle contraction of afferent arteriole, reduced renal blood flow, reduced GFR (inc BP=myogenic constriction=compensating vasodilation)
Tubuloglomerular feedback- Juxtaglomerular apparatus. GFR inc=rate through tubules increased
Reduced Na, Cl and water
Macula densa sense increased levels of ions in filtrate, inhibits release of NO, afferent arterioles constrict, lowers GFR, lowers GFR rate through tubules
What kidney regulation process helps preserve nephron integrity from a sudden/abrupt increase of BP?
Myogenic mechanism
Define Juxtaglomerular Apparatus
What does it contain?
Ability to affect systemic BP through auto regulation of tubuloglomerular feedback
Contains: one JGA per nephron in walls of afferent arteriole
Macula densa cells- walls of DCT
Lacis cells, located between a/efferent arterioles and DCT
Define Lacis cells
Modified mesangial cells
What are the two functions of the JGA?
Detect low BP (lack of stretch in afferent wall)
Synthesize, store and secrete renin
Where are macula densa cells located?
DCT
What are the two functions of macula densa?
Detect increase in NaCl in FILTRATE
Release ATP, adenosine that contract afferent arteriole, reduces GFR
What are the 3 components of the Justaglomerular apparatus?
These components together make up what concept?
Macula Densa
Juxtaglomerular cells
Lacis cells
Tubuloglomerular feedback
What does tubuloglomerular feedback regulate?
BP within kidneys and eventually, systemic BP
Kidney blood vessels are only supplied by what NS?
Sympathetic
At rest- low
Exercise/fight: Constriction of afferent, decreased flow to glomerulus, decreased GFR
What two processes protect the nephrons from sudden BP increases?
Myogenic mechanism
GFR neural regulation
What are the two hormones that control regulation of GFR?
Angiotensin II- reduces GFR
ANP- increases GFR
How does Angiotensin II create its effect on GFR?
Potent vasoconstrictor
Acts on efferent arteriole
Reduces renal flow
How does ANP create its effect on GFR?
Secreted by atria in response to increased volume
Vasodilates afferent and efferent, increases GFR
When does passive movement occur?
Pressure gradients allow flow from high->low w/out ATP (glomerular filtration)
When does active movement occur?
Moving solutes against a gradient w/ help of ATP expenditure (Na/K pump)
What three structures can reabsorb filtrate?
Where does the majority occur?
Renal Tubule
Renal Ducts
PCT- reabsorbs the most
What are solutes that are actively and passively reabsorbed?
Glucose AA Urea Na K Ca Cl Ma Bicarb Phosphates
What distal structures “fine tune” the reabsorption process?
LoH
DCT
Collecting duct
If small protein and peptides are passed through the glomerular filter, how are they usually reabsorbed?
Pinocytosis
Tubular reabsorption occurs through what two processes?
Paracellular- PASSIVE movement between adjacent tubule cells, 50% of reabsorption
Transcellular- PASSIVE and ACTIVE movement through the tubule cell itself
Define Apical Membrane
Lumen side of the cell
Define Basolateral Membrane?
Interstitial side of the cell
Define Obligatory Water Reabsorption and where does it occur?
90% of water reabsorption by kidneys occurs through the reabsorption of Na, Cl and glucose
Occurs in PCT and descending LoH
What drives obligatory water reabsorption?
Solute reabsorption via osmosis
What areas of the kidney are ALWAYS permeable to water?
PCT
Descending LoH
Obligatory water reabsorption accounts for 90% of reabsorbed fluid, what happens to the other 10%?
Facultative water reabsorption
What regulates Facultative Water Reabsorption and where does it occur?
Regulated by ADH
Occurs in late DCT and Collecting Ducts
Tubular secretion gives the final chance to secrete what substances?
H K Ammonium Creatinine Drugs like penicilin
If antibiotics/drugs were to be secreted into filtrate, where would the transfer occur?
Tubular secretion, from capillaries (peritubular/vasa recta), interstitial and tubule cells to filtrate
What happens to most of the ammonia made in the body?
Converted to urea in liver
What is urea’s beneficial component to the body?
Significant in creating/maintaining osmotic gradient in renal medulla
Where is the majority of bicarbonate reabsorbed?
PCT
Since Bicarbonate can’t be reabsorbed in tit’s complete form, what steps have to happen first?
H + HCO3= H2CO3 Carbonic Acid
H2CO3 disassociates into CO2 and water
CO2 diffuses into tubule cells and joins with H2O forming H2CO3 in tubule cells where it dissociates into H and HcO3
For every H+ secreted into tubular lumen, how many bicarb and Na are reabsorbed?
One and One
The largest amount of solute and water reabsorption from filtered fluid occurs where?
What are the solute %s that are reabsorbed?
PCT
100% of glucose, aa and vitamins
80-90% of Bicarb
65% Na, K and water
50% Cl and urea
How is Na moved out of tubules and into interstitial fluids?
Actively with Glucose and AA co-transported w/ Na
How does urea and Cl ions move from filtrate into interstitial fluid?
Passively
What happens when Na and Cl move into interstitium?
Osmotic imbalance, causing water to be obligated to move out of filtrate into interstitium by osmosis which often brings K and Ca
Why are cells in PCT and descending LoH especially permeable to water?
Aquaporin 1 channels- protein water channels that increase rates of water movement
Define Solvent Drag
Osmosis of water bringing K and Ca with it in the PCT
What effects does PTH have on the kidneys and reabsorption?
Stimulates PCT to secrete phosphate
Stimulates calcitriol (Vit D) to be made in PCT and absorbed in blood
Stimulates cells in DCT to absorb more calcium
How does calcitriol exert it’s effect on Ca absorption?
Calcitriol circulates in intestines to cause more Ca from digestive system to be absorbed
Where is solute and water reabsorption independently regulated?
Entire LoH
NOT in PCT
Where is filtrate diluted or concentrated?
Descending- mostly water reabsorption and solute secretion, concentrates
Ascending- no water absorption, solute absorption, dilutes
What happens in the thin portion of the Ascending LoH?
Passively permeable to small solutes, impermeable to water
Solutes move out of tubule, water remains causing first dilution of filtrate
After the end of the first dilution process in the Ascending LoH, is the filtrate hyper or hypoosmotic?
Hypo
What happens in the thick portion of the Ascending LoH?
Active reabsorption of K, Na, Cl but region is IMPERMEABLE to water
Filtrate moves up ascending limb and dilutes even more
What events occur in the late portion of the DCT?
90-95% of filtered solutes/water have been reabsorbed and returned to circulation
Amount of reabsorption of solutes/water in the DCT is dependent on what?
Body feedback
Hormonal
Osmoreceptor
How are the DCT and PCT similar in regards to Na reabsorption?
How is the DCT different?
Completed by active transport
Cells impermeable so water doesn’t follow Na by osmosis
ADH can cause principal cells in DCT and collecting ducts to become permeable
How does ADH trigger Principal cells and Collecting Ducts to reabsorb water?
ADH causes cells to generate Aquaporin 2 channels in apical membrane of cells lining the tubule
With ADH present, what is the concentration of urine?
Where does the presence of ADH cause an osmotic imbalance?
ADH present, small quantity of highly concentrated urine
DCDuct
What cascade occurs when ADH is present and causes an osmotic imbalance?
Forces urea reabsorption
Urea assists with increasing high osmolarity in interstitial fluid
Where does Urea Recycling occur?
Reabsorbed in Distal Collecting Duct
Secreted in descending LoH
If ADH is at max secretion levels, how much urine output will there be?
400-500mL very concentrated urine
When blood pressure/volume stabilizes, what occurs with ADH?
Decline, removing Aquaporin-2 molecules from Principal cells
What happens to Principal Cells when aldosterone is present?
Na reabsorption
K secretion
What causes aldosterone to be released?
Hyperkalemia
Angiotensin II- low BP
Principal cells are responsible for secretion of __ and reabsorption of __?
K
Na
What stimulates the two different Intercalated cells?
Osmoreceptor readings in reference to pH and K levels
What are the two types of intercalated discs and what are their functions?
Type A:
Secrete H
Reabsorb Bicarb and K
Type B:
Reabsorb of H
Secrete Bicarb
Secrete K
Where does ANP have its effect?
How does it carry out this effect?
DCT
Collecting Ducts
Inhibits reabsorption of Na and water (inc urine output)
Inhibits RAAS
RAAS is activated when low BP/volume is sense where?
Afferent arteriole
What is the cascade of events when the RAAS is activated?
Low pressure sensed at afferent arteriole
Juxtaglomerular cells release renin
Hepatocytes release angiotensiogen
Renin cleaved 10 aa peptides off of angiotensinogen making Angiotensin-1 which goes to lungs
Converted to Angiotensin-2 by ACE and is now ACTIVE
Angiotensin II affects renal physiology in what 3 ways?
Decreases GFR by constricting afferent arteriole
Enhances Cl, Na and water reabsorption in PCT by Principal cells
Stimulates release of aldosterone from adrenal cortex
Regulation of plasma osmolarity and volume are the responsibility of what areas in the kidneys?
LoH:
Descending= permeable, concentration of urine, concentrating filtrate
Ascending= diluting urine, impermeable
DCT and Collecting ducts= final dilution/concentration
Absence of ADH= _____ urine
Presence of ADH= _____ urine
Absent= diluted Present= concentrated
What is normal color for urine?
Yellow or amber
What is urine turbidity?
Transparent when voided, become cloudy with time
What is urine’s odor?
Mildly aromatic, become ammonia like with time (bacteria turning urea->ammonia)
What is normal urine pH range?
4.6-8.0 w/ 6.0 being average
What are some dietary factors that can alter urine pH?
High protein increases acidity
Vegetarian increases alkalinity
What is normal urines specific gravity?
1.001-1.035
lower=hydrated
higher the solute, higher the SpecG. value
Water accounts for _% of urine
Solutes account for _%
What are the solutes?
95%
5%
Urea, creatinine, uric acid, urobionogen
Fatty acids, pigments, enzymes, hormones
Where does uric acid and urobilinogen come from to get into urine?
Uric acid- break down of nucelic acids
Urobilinogen- breakdown of Hgb
What are the two blood tests for testing urine function?
Blood Urea Nitrogen- BUN increases when GFR severely reduces
Plasma creatinine- no use for creatinine in f body
What are normal levels for BUN and plasma creatinine?
BUN= 7-20mg/dL
1.6mg/dL
Define Renal Plasma Clearance
Volume of plasma in mL that can be completely cleared of a substance per time unit
What is a great measure of true GFR?
What is a good estimate for GFR?
Insulin- plant polysaccharide
Creatinine clearance
What is the sequence of urine flow from kidney to elimination?
Collecting ducts Papilla Papillary ducts Minor calyces Major calyces Renal pelvis Ureter Bladder Urethra
Where do ureters meet with kidneys?
Pass obliquely into posterior/inferior aspect of bladder
Define anti-reflux mechanism
When bladder is full, it pulls down which closes valves to ureters
What are the 3 layers of ureters?
Adventitia- anchors ureters to tissues and contains blood/lymph vessels and nerves
Muscularis- provides paristalsis
Mucosa- transition epithelium w/ goblet cells to protect mucosa from acidity
What is the bladders shape when empty and full?
Collapsed
Pear shaped
What is the bladders anatomical location?
Posterior pubic symphisis Anterior rectum (males) Anterior vagina Inferior uterus Held by peritoneal folds
What are the 3 layers of the bladder?
1: Serosa- visceral peritoneum
2: Adventitia- covers post/inferior surface and continuous w/ ureter
Muscularis- detrusor muscle
3: Mucosa- uroepitheroium, rugae, transitional epitherlium,
What are the 3 layers of the detrusor muscle?
Inner longitudinal
Middle circular
Outer longitudinal
What happens when detrusor muscle is relaxed and contracted?
Relaxed= bladder filling Contracted= forced emptying
What part of the renal system is a huge sight for development of cancer cells?
Transitional epithelium of bladder
Define trigone
Smooth triangular bladder floor w/ ureteral openings in posterior corners and urethral opening in the anterior corner
Define the Internal Urethral Sphincter
Inferior aspect of the bladder
Extension of detrusor muscle w/ involuntary control by parasymp. NS
Located just above prostate in males
Define External Urethral Sphincter
Skeletal muscles of deep perineal muscles and pelvic floor
Below prostate in males
Opening of external urethra in females
What are the 3 parts of the male urethra?
Prostatic
Membranous
Spongy
What are the characteristics of the Prostatic urethra?
Smooth muscle forming internal urethral sphincter
Contains openings for prostatic fluids and sperm
What are the characteristics of the Membranous Urethra?
Shortest region
Passes through urogenital diaphragm
Skeletal muscle forms external urethral sphincter
What are the characteristics of the Spongy Urethra?
Longest region
Contains bulbourethral openings- Cowpers glands, delivers alkaline fluid to neutralize urethra acidity
What does the mucosa of the female urethra consist of?
Epithelium and lamina propria
Transitional epithelium near bladder
Middler section is pseudo/stratified columnar
External urethra is non-keratinized stratified squamous
What initiates the mechanism for urination?
What is the sequence of events?
Parasympathetic
Involuntary contraction on detrusor muscle
Internal urethral sphincter opens, urine moves from bladder to urethra
Sensation to urinate is sent/received
Voluntary contraction of external urethra sphincter prevents urination until appropriate time
Voluntary relaxation of external sphincter allows for urination
Why do humans wear diapers as babies and geriatrics?
Learned control to contract/relax external urethra sphincter and pelvic muscles to over ride weak spinal muscles which are normally contracted
No conscious thought as infant
Weak muscles as a geriatric
What effects does nephron deterioration cause with age?
Kidney shrinkage
Decreased renal flow/GFR
Why does increased incidence of calculi occur with age?
Decreased thirst sensation
What influences can cause polyuria and nocturia?
BPH
Prostate cancer
Hematuria
Dysuria
