Urinary System Flashcards
What is the funtional unit of the kidney?
Nephron, or uriniferous tubule (depends on how you view it
How many nephrons in the kidney?
Around 2 million
How much of cardiac output is recieved by the kidneys?
20-25%
How do the blood supplies to the lobes of the kidney relate?
They do not cross over, each stays in localized lobe
What is the hilum of the kidney?
Concave region where renal pelvis is located
What does the hilum contain?
Renal arteries, veins, lymph vessels, and nerves
Describe the renal pelvis
Cone-shaped expansion of the upper end of the ureter
What does the pelvis connect?
Major renal calyces
What is the superficial layer of kidney consisting of renal corpuscles and convoluted tubules called?
Renal cortex
What is a renal column? What do they run between?
An extension of cortical tissue. Run between adjacent renal pyramids
What are medullary rays?
Straight tubules that extend from base of renal pyramid into the cortex
What makes up the bulk of the renal medulla?
Renal pyramids, thin limbs of henle and collecting tubules
Where is the renal papillla?
At the apex of each renal pyramid
What does the renal pyramid project into? What is the name of its perforated tip?
Projects into minor caly lumen, tip is called area cribrosa
What is in the renal interstitium
Sparse connective tissue of the kidney, fibroblasts, mononuclear cells, some erythropoietin
What produces erythropoietin? Where are these cells located?
Fibroblasts, near peritubular capillaries
What is the kidney very important to in terms of blood flow?
Kidneys control blood pressure in a variety of ways
What kinds of cells are present in the medulla
Pericytes along blood vessels to loops of Henle
Interstitial cells between loops of henle, connecting ducts, and vasa recta
What do interstitial cells contain? What can they produce?
Contains elongated nuclei with lipid droplets, may synthesize medullipin I which eventually forms a vasodilator through liver modfication
Each lobe of the kidney is made up of multiple _______
Lobules
What is a renal lobule?
Area of cortex bounded on either side by interlobular artery. Nephrons all drain into the same connecting duct
What are the parts of a nephron?
Renal corpuscle, proximal convoluted tubule, loop of Henle, distal convoluted tubule
Which has longer loops of Henle, the cortical nephrons or the juxtamedullary nephrons?
The juxtamedullary nephrons
What are the nephrons for?
Exchanging water, salt, and urea
What are cortical and juxtamedullary nephrons classified by?
Location (cortex or near medulla)
Which type of nephron has peritubular capillaries?
Cortical nephrons
What do the long loops of Henle of juxtamedullary nephrons associate with (blood supply?)
Vasa recta
What kind of nephron establishes the concentration gradient of the interstitial space of the medulla?
Juxtamedullary nephrons
Which contains a greater volume, PCT or DCT?
Proximal convoluted tubule is much larger than distal convoluted tubule
What is the structural difference between DCT and PCT?
Distal convoluted tubule has apically located nuclei and no brush border
What is the epithelium of collecting tubules?
Simple cuboidal epithelium
Where are all glomeruli?
The renal cortex
What is the outer stripe of the outer medulla?
Only thick limbs and connecting ducts, no thin limbs
What is the inner stripe of the outer medulla?
Mixture of thick and thin limbs, along with collecting ducts
What area of the kidney has only thin limbs?
The inner medulla
How often would a section of blood pass through the kidney?
Approx. every 4-5 minutes
List the divisions of the renal artery down to the efferent arterioles along with where they are located in the kidney
Renal artery (hilum) -> interlobar arteries (between renal pyramids) -> arcuate arteries (along corticomedullary juntion) -> interlobular arteries (cortical tissue between medularry rays) -> afferent arterioles (enter glomerulus) -> efferent arterioles
What are the differences between typical blood circulation and renal circulation?
Kidneys pass through two sets of capillaries, one at the glomerulus, one after the efferent arteriole
What do afferent arterioles supply?
Glomerular capillaries
What do efferent arterioles supply?
Peritubular capillary network - come from afferent - give rise to peritubular capilarry netork and vasa recta depending on the nephron
Describe the course of vasa recta
Straight path into medulla and renal papilla - form capillaries, loop back and increase diameter approaching corticomedullary boundary
What does venous drainage mirror?
Arteriole blood supply
Trace venous drainage from superficial and deep cortical veins to kidney hilum
Superficial = Stellate -> Interlobular -> arcuate -> interlobar -> renal vein
Deep = Deep cortical veins -> Interlobular -> arcuate -> interlobar -> renal vein
What are the parts of the renal corpuscle?
Glomerulus and Bowman’s capsule
What is the lining of Bowman’s capsule?
Parietal - simple squamous epithelium - outer wall
Visceral – modified simple squamous epithelium composed of podocytes covering glomerular capillaries
What forms filtration slits?
Processes of podocytes wrapping around capillaries
What are the poles of the renal corpuscle
Vascular pole (afferent and efferent) and urinary pole(space continuous with proximal convoluted tubule
Where does the distal convoluted tubule come up?
Right between afferent and efferent artery
Where is the macula densa in the nephron?
The distal convoluted tubule
What do you call the capillary network inside of bowman’s capsule?
Capillary tuft
What is special about the basal lamina of the fenestrated endothelium of capillaries?
Shares basal lamina with podocytes - contribute to protection and filtration
What is another name for Bowman’s space?
Urinary space
What is the macula densa?
Specialized portion of distal convoluted tubule primarily involved in sensing sodium chloride ions
What is the brush border of the proximal convoluted tubule extremely sensitive to?
Osmolarity changes - ruffles up when kidney shuts down post mortem. Appears as debri in PCT
What are mesangial cells?
Connective tissue between glomerular capillaries that helps turn over basement membrane
Why does basement mebrane need to be “turned over”?
It is serving as a filter so it needs to be changed or “cleaned”
Do mesangial cells have role in blood flow?
Yes - minor
What can mesangial cells produce?
Prostaglandins, endothelins
What do mesangial cells respond to?
Angiotensin II and ANP
How do mesangial cells lend support to capillaries
Proliferate and synthesize matrix material and collagen
What kind of filter is a podocyte?
Macromolecular and charged filter
What is a filtration slit?
Spaces between pedicels with filamentous diaphrams that bridge slit
What are the 2nd degree processes of a podocyte?
Pedicel - visceral layer of bowman’s capsule
What is a podocyte?
A modified epithelial cells that have 1st and second degree processes that form visceral layer of Bowman’s capsule
Is there typically one or more than one podocyte on a capillary?
Typically more than one
What contributes to the negative charge in glomerular epithelium?
Podocalyxin - a sialoglycoprotein that extends into glycocalytx coat of podocyte
What makes up the renal filtration barrier?
Fenestrated endothelium, basal lamina, filtration slits w/t diaphrams
What protein makes up filtration slits? What is it anchored to? What does it repel? What does it allow through?
Nephrin (IgB superfamily) anchored to actin filamints by CD2AP. Repels negatively charged proteins or large proteins. Allows passage of H20, ions, small molecules
What is the epithelial cells of the Proximal convoluted tubule? What else helps it resorb important valuable filtrates?
SImple cuboidal epithelium with microvillus brush border, pinocytotic vesicles, and abundant lysosomes. Also has infoldings of plasma membrane - all designed to resorb
What does PCT reabsorb
Glucose, amino acids, small proteins, 80% of NaCl
Is there an osmolarity change in ultrafiltrate in PCT
No
How do mesangial cells contribute to immune response?
Immunoglobulins can enter mesangial matrix and induce cytokine production
What is the epithelium of the pars recta?
Simple cuboidal epithelium (pars recta is same as descending limb)
Epithelium of ascending limb?
Cuboidal epithelial cells with apically located nuclei
What compartmentalizes the mitochondria in the ascending thick limb?
Infoldings of the basal plasma membrane
What is the macula densa a part of?
The juxtaglomerular apparatus / ascending limb
What is the distal convoluted tubule most similar to histologically?
The ascending thick limb of Henle’s loop
How do DCT cells compare to the PCT?
Shorter with wider lumen and no brush border
What part of the nephron absorbs Sodium ions and transfers potassium, ammonium, and hydrogen ions into the interstitium?
Distal Convoluted tubule
Where is the juxtaglomerulr apparatus located?
The vascular pole of the renal corpuscle
What are juxtaglomerular cells?
Modified smooth muscle cells in walls of afferent (mainly) arteriole.
What do juxtaglomerular cells detect? What do they secrete?
Sense changes in blood pressure. Secrete renin
What are macula densa cells? What do they detect and secrete?
Epithelial cells of distal tubule with elongated closely packed nuclei. Sense changes in NaCl and low salt. Secrete renin. May be associated to JC cells via gap junctions
What innervates JG cells? What stimulates renin?
Sympathetic nerve fibers.
Norepinephrine and dopamine secreted by symp fibers
What other cell (besides JG and macula densa) is present in the JG apparatus?
Extraglomerular mesangial cells
What are other names for extraglomerular mesangial cells?
Pole cushion/lacis cells
What do extraglomerular mesangial cells connect to and how?
Connect to each other and JG cells via gap junctions
How does Renin ultimately stimulate DCT tubule epithelial cells to resorb Na & water?
Renin converts angiotensin to angiotensin I. Angiotensin I is converted to Angiontensin II in lung capillaries. AT-II simulates release of aldosterone in adrenal cortex. Aldosterone stimulates DCT epithelial cells to resorb Na + H20 to raise blood volume and pressure
WHat ultimately controls DCT resorbtion?
Sympathetic system
Where are extraglomerular mesangial cells found?
Between afferent and efferent glomerular arterioles
What can stimulate the renin-angiotensin-aldosterone system?
Drops in extracellular fluid, renal blood pressure, or sodium chloride in macula densa
Name the five regions of the collecting duct
Connecting tubule and cortical collecting duct, outer medularry collecting duct and inner medullary collecting duct, and papillary duct (duct of Bellini. “And” groups can be lumped together
What are cell membranes of collecting duct rich in?
Aquaporins for water resorbption
Do collecting ducts stain more or less strongly than PCT and DCT tubules?
Stain more lightly than PCT/DCT
Are collecting tubules located in the cortex or medulla?
They are in both!
What histological structure are collecting tubules located in?
Medullary rays
What are the two types of epithelium in the collecting tubules?
Principal (light) cells and Intercalated (dark) cells
Describe Principal cells
Cuboidal cells with round central nucleus and central cilium (only seen in EM)
Describe dark cells
Medullary **
What is a duct of Belliini
Very large collecting tubule deep in kidney
What is the area cibrosa?
Region of renal pyramid with 10-25 openings where urine flows into minor calyx
Where is most filtrate resorbed? What is resorbed in this region? Is there osmolarity change?
PCT - glucose, a.a., small proteins, NaCl and water, Calcium and H20.
No osmolarity change
What is absorbed in descending thick limb?
H20 - NaCl is NOT
WHat is reabsorbed in the ascending thin limb? What is secreted?
NaCl in - NOT H20, urea moves into tubule
**`
What is inflammation of the glomeruli called?
Glomerulonephritis
What can cause glomerulonephritis?
What can cause the direct causes of glomerulonephritis?
What automimmune disorder targetting can target the glomerular components
Can be a proliferation of podocyes and mesangial cells and leukocyte infiltrate.
Can occur from streptococcal infection somewhere else in the body due to deposits of immune complexes.
Also possible from immune or autoimmune disorders (lupus).
Anti-GBM antibodies against collagen Type IV
What can indicate glomerulonephritis? What are the long term effects?
Blood or protein in urine, decreased urine output, chronic form destroys glomeruli and leads to renal failure
What disease is characterized by destruction of epithelial cells lining a specific area of nephron? What is the most common area for this?
Acute tubular nephrosis, often occurs in pars recta of PCT
What are the two types of Acute tubular necrosis?
Ischemic (shock, crush, bacterial) or toxic (poisons, heavy metals, organic solvents, antibact./antifungal, nonsteroidals) *****
What is reduced blood flow to kidneys causing decreased golerular filtration and tubular ischemia?
Chronic renal failure
What are some changes to the kidneys that may occur?
DOes diabetes insipidus involve insulin?
No, it involves hyopthalamus
What results in diabetes insipidus?
The destruction of the paraventricular and supraoptic nuclei in hypothalamus that synthasize antidiuretic hormone
What does diabetes insipidus do to the kidney?
Decreased ability of kidney to concentrate urine due to reduced ADH
What are the classic symptoms of diabetes insipidus
Polydipsia, dehydration, polyuria
Kidney stones
**8
Struvite stone
What kind of muscle is in the ureter?
Smooth muscle
What kind of epithelium is in the ureter?
Transitional epithelium
Which has more muscle, the proximal or distal portion of the ureter?
Distal (entire extra layer of smooth muscle)
Is the ureter muscle contraction uniform?
No, it is peristaltic
What can the transitional epithelium of the urinary bladder do?
Rapidly divide more plasma membrane surface area as bladder distends
Layers of the kidney
What is the plaque of umbrella cells?
Thickened plasma membrane in luminal plasma membrane that can be flattened
Elliptical vesicles
Distended bladder
How many layers of muscle does the urethra have?
2 - inner longitudinal and outer circular
How does the epithelium of the urethra in the male change during its different sections
Prostatic section - transitional epithelium
Membranous and cavernous portions - pseudostratified or stratified columanr epithelium)
End of cavernous urethra - stratified squamous epithlium
What portion of urethra in males contains glands of Littre and recieves ducts of the bulbourethral glands?
The penile urethra
What is the change in epithelium of the female urethra
Starts lined by transitional epithelium and transitions to psudeostratified columanar and stratified squamous nonkeratinized epithelium. May contain glands of Littre
How does the descending thick limb differ from PCT in terms of contents of cells?
Fewer lysosomes and smaller mitochondria, however, still maintains a prominent brush border
What is the lining of the thin limb of Henle? What is characteristic about the nuclei?
Simple squamous epithelial cells. Nuclei bulge into the lumen
What is a diuretic that can inhibit the reabsorption of NaCl in the ascending thick limb
Furosamide
