Chapter 24: Urinary System (E5)

**Explain how the nephron loop establishes the concentration gradient within the interstitial fluid of the kidney**

**by the countercurrent multiplier of the nephron loop**

What are the Mascula Densa cells of the Juxtaglomerular apparatus? And what is their funciton?

- Group of modified epithelial cells in the wall of the distal convoluted tubule where it contracts the granular cells. Located only in the tubule wall adjacent to granular cells of afferent arteriole and are more narrow and taller than other DCT epithelial cells. -Function: 1. Detect changes in sodium chloride (NaCl) concentration of fluid within the lumen of DCT. 2. Signal granular cells in the afferent arteriole to release renin throug paracrine stimulation.

what is the difference between the cortical nephrons and the juxtamedullary nephrons?

-Cortical nephrons: oriented with renal corpuscles near peripheral edge of cortex and have a relatively short nephron loop that barely penetrates the medulla. the bulk of nephron resides in the cortex. 85% are coritcal nephrons. -Juxtamedullary nephrons: 15% of nephrons are these. Renal corpuscles lie adjacent to the corticomedullary junction and have relatively long nephron loops that extend deep into medulla. important when establishing a salt concentration gradient within interstitial space that lies outside the nephron loop. Collecting loops and collecting ducts allow for regulation of urine concentrations by antidiuretic hormone.

Compare and contrast the female and male urethra

-Female: 1 function to transport urine from urinary bladder to exterior of body. Lumen lined with stratified squamous epithelium 4 cm long and opens outside the body at the external urethral orifice located in female perineum. -Male: both urinary and reproductive functions, serves as a passageway for urine and semen. 19 cm long; 3 parts: prostatic urethra, membranous urethra and spongy urethra.

What is the function of the Juxtaglomerular apparatus (JG)? And what are the main components?

-Helps regulate filtrate formation and systemic blood pressure. - Main components are Granular cells and Macula Densa cells.

What are the Granular cells of the juxtaglomerular apparatus? And what is their function?

-They are modified smooth muscle cells of the aferent arteriole located near entrance into the renal corpuscle. -Functions: 1.) they contract when stimulated either by stretch receptors or by sympathetic division of ANS. 2.) synthesize, store, and release enzyme renin.

Trace the fluid from its formation at the renal corpuscle until it exits the body through urethra

1. capsular space 2. PCT 3. descending limb of nephron loop 4. ascending limb of nephron loop 5. DCT 6. collecting duct 7. papillary duct 8. minor calyx 9. major calyx 10. renal pelvis 11. ureter 12. urinary bladder 13. urethra

What are the 3 major functions of the Urinary system?

1.) Excretion: removal of organic waste products from body fluids. 2.) Elimination: discharge of waste products into enviroment 3.) Homeostatic Regulation: regulates the volume & solute concentration of blood.

What are the 4 tissue layers that surround and support the kidneys?

1.) Fibrous capsule 2.) Perinephric fat 3.) Renal fascia 4.) Paranephric fat

____: (HPc) pressure in the glomerular capsule due to the amount of filtrate already within the capsular space the presence of this filtrate impedes the movement of additional fluid from the blood into capsular space and opposes filtration. Typical value is 18mmHg

Capsular Hysdrostatic Pressure

Component of renal corpuscle: between the parietal and visceral layer of the glomerular capsule receives filtrate, which is modified to form urine.

Capsular space

______: (positive feedback mechanism) involves the nephron loop and is partially responsible for establishing salt concentration gradient within the interstitial fluid.

Countercurrent Multiplier

______:(structure of the urinary bladder) contracts and expels urine from the bladder formed by 3 layers of smooth muscle.

Detrusor Muscle

Component of renal tubule: originates in renal cortex at the end of nephron loops, thick ascending limb and extends to a collecting tubule composed of a simple cuboidal epithelium--> smaller and have only sparse, short, apical microvilli

Distal convoluted tubule (DCT)

Component of renal corpuscle: blood leaves the glomerulus through this

Efferent arteriole

Tissue layer the sourround and supports the kidneys: a layer of collagen fibers that covers outer surface of entire organ

Fibrous Capsule

_____: formed when blood flows through glomerulus and some component of plasma enter capsular space

Filtrate

_____: (renal sinus) cavity formed by convergence of several minor calyxes whcih drain urine from the minor calyx into renal pelvis (2 or 3 combined to form renal pelvis)

Major Calyx

differentitate between the ascending limb and descending limb of the nephron loop: ____: permeable to H2O, impermeable to the movements of salt ou tthe tubule water moved from tubular fluid into interstital fluid as a reuslt, salts retained in tubular fluid. _____: impermeable to water and actively pumps salt out the tubular fluid into interstitial fluid. Result water in tubular fluid and salt moved from tubular fluid into interstitial fluid.

descending limb Ascending limb

______: (external to kidneys) involves nervous system and hormonal regulation which can increase or decrease GFR, respectively.

extrinsic control

______: (within the kidneys) consists of renal regualtion that maintians GFR at a normal level. consist of: Myogenic response and Tubuloglomerular feedback

intirisic control

_____: urination

micturition

Describe how pH is regulated in the collecting tubules

pH of blood and urine is regulated by intercalated cells. As a result of consuming a more acidic diet, newly synthesized HCO3- is reabsorbed into the blood and H+ is secreted into tubular fluid, by type A intercalated cells. Result is an increase in blood pH (more alkaline) and a decrease in urine pH (more acidic) which averages a pH of about 6.0.

Explain how podocytes help filter substances out of the blood.

pedicles of one podocyte interlock with pedicles of a different podocyte, so the membrane covered filtration slits restrict the passages of most small proteins.

______: are octopus like cells that have long "footlike" structures called pedicles.

podocytes

____: (mechanism to evaluate kidney function) measures the volume of plasma that can be completely cleared of a substance in a given period of time ususally in 1 minute

renal clearnace test

_____:(structure of urinary bladder) mucosal folds allow for even greater distension of the bladder wall.

rugae

_______: Long epithelial lined fibromuscualr tubes that transport urine form kidneys to urinary bladder. Averages 25cm inn adults in lenght and retroperitoneal. originate at renal pelvis exits the hilum of kidney extending inferiorly to enter posteriolateral wall at the base of urinary bladder. Wall of ureter composed of 3 concentric tunics: mucosa, muscularis, and adventitia

ureters

Describe the role of ADH in regulating urine concentration

ADH bound to principal cells. Greater amounts of ADH result in larger amounts of H2O reabsorption by principal cells and less H2O remaining in tubular fluid; thus a smaller volume of more concentrated urine is produced.

Component of renal corpuscle: blood that enters the glomerulus through this

Afferent arteriole

What is the average amount of fluid that enters the glomerulus each day and the average amount of fluid urinated each day?

An average of 180L of filtrate is produced daily by the kidneys through the glomerular filtration membrane. 24 hour urine volume is 800 to 2000 mililiters per day.

_____: (OPg) osmotic pressure exerted by the blood due to the unfiltered dissolved solutes it contians. Most important plasma proteins (colloid) opposes filtration because it tends to pull or draw fluids into the glomerulus. Typical volume is 32 mmHg.

Blood Colloid Osmotic Pressue (OPg)

Explain the relationship between the storage and micturition reflex in controlling urination.

Both regulated by sympathetic and parasympathetic divisions of ANS.

_____:(extrinsic factor that regulates GFR) increases GFR to eliminate fluid

Atrial naturetic peptide (ANP)

differntiate between filtrate, urine and tubular fluid.

Filtrate consist of blood plasma, components like nutrients, essential ions, water, some waste mostly protein free. Urine contains metabolic wastes like creatine, urea, uric acid, excess ions but no proteins. Tubular fluid is glomerular filtrate that has been passed through PCT and reabsorption begins.

_____: is when hydrostatic pressure forces water through membrane pores and solute molecules small enough to pass through these pores are carried along. Happens in glomerulus.

Filtration

______: (HPg) blood pressure in the glomerulus. Driving force that pushes water and some dissolved solutes out of the glomerulus and into capsular space of renal corpuscle. Promotes filtration

Glomerular Hydrostatic Pressure (HPg)

Component of renal corpuscle: formed by 2 layers: an internal, permeable visceral layer that directly overlies the glomerular capillaries and an external impermeable parietal layer composed of simple squamous epithelium.

Glomerular capsule (Bowman capsule)

Component of renal corpuscle: a thick tangle of capillary loops called the glomerular capillaries, a capillary network within the renal corpuscle in a kidney.

Glomerulus

_______: are located on either side of the vertebral column, between vertebrae T1 & L3. Main function: produce urine

Kidneys

What are the mechanisms to evaluate kidney function?

Mearsuring glomelular filtration rate and measuring renal plasma clearance

_____: (mechanism to evaluate kidney function) formula: GFR=UV/P U: concentration of inuline in urine V: volume of urine produceed per minute P: concentration of inuline in plasma

Measuring Glomelular filtration rate

______:(reflex in controlling urination) controlled by autonomic and somatic nervous systems. 1.)When the volume of urine retained within the bladder reaches 200ml to 300ml the bladder becomes activated 2.)Baroreceptors send nerve signals through visceral sensory neurons to stimulate the micturition center within the pons. 3.) Micturition center alters nerve signal propagation down the spinal cord and through pelvic splanchnic nerves. 4.) Parasympathetic stimulation causes smooth muscle cells to compose detrusor to contract and internal urethral sphincter to relax.

Micturition reflex

____: (renal sinus) a cup-shaped cavity at the base of the renal papilla, which drains urine from the renal papillae into major calyxes

Minor Calyx

____: (intrinsic factor that regulates GFR) involves the contraction and relaxation of smooth muscle in the wall of afferent arterioles in response to changes in stretch.

Myogenic response

Describe the relationship between NFP, glomerular filtration rate (GFR), the volume of filtrate produced and the volume of urine excreted.

NFP directly influences the GFR. As the NFP increases, the GFR increases as well. increase NFP increases: GFR, amt of filtrate found, solutes and h2o remaining in tubular fluid, and substances in urine.

______: is a microscopic functional filtration unit of the kidney. Each of these consist of 2 major structures: the renal corpuscle and renal tubule

Nephron

Component of renal tubule: originates at a sharp bend in the proximal convoluted tubule, has 2 limbs: descending limb and ascending limb which is continuous with the medulla.

Nephron loop

_____: is aggregated pressure that causes fluid to move out across a blood capillary wall; calculated by substracting net osmotic pressure from hydrostatic pressure. HPg-(OPg+HPc)=NFP

Net filtration pressure (NFP)

Tissue layer that surrounds and supports the kidneys: is the outermost layer surrounding the kidney, it is composed of adipose CT and provides cushoning and stabilization for kidney.

Paranephric fat

Tissue layer that surrounds and supports the kidneys: a thick layer of adipose tissue that surrounds fibrous capsule

Perinephric fat

List the substances that are secreted by the tubular system.

Potassium (K+) Hydrogen (H+) Ammonium (NH4+) Creatinine Urea

Componets of renal tubule: 1st region of the renal tubule originates at the tubular pole of renal corpuscle and composed of a simple cuboidal epithelium with tall apical microvilli, increase absorption area and increase reabsorption capacity.

Proximal convoluted tubule (PCT)

_______: (renal lobe) extensions of the cortex that project into the medulla and subdivide into renal pyramids.

Renal Columns

structure within a nephron, enlarged, bulbous portion of nephron housed within the renal cortex. Composed of 2 structures: glomerulus and glomerular capsule.

Renal Corpuscle

_______: ( renal lobe)is the superficial (outer) portion of the kidneys, in contact with the fibrous capsule. A reddish-brown color and granular.

Renal Cortex

Tissue layer that surrounds and supports the kidneys: dense fibrous outer layer that anchors kidney to surrounding structures. Collagen fibers extend outward from fibrous capsule through perinephric fat to this layer. Posteriorly renal fascia fuses with deep fascia surrounding muscles of body wall. Anteriorly renal fascia forms a thick layer that fuses with peritoneum.

Renal Fascia

_______: (renal lobe) innermost part of the kidney split into sections known as renal pyramids.

Renal Medulla

______: (renal lobe) medially directed apex (tip) of renal pyramid, projects into the renal sinus.

Renal Papilla

_____: (renal sinus) superior funnel shaped end of ureter inside renal sinus. Merges at medial edge of kidney with the ureter. Housed within the space around this are renal artery, renal vein, lymph vessels, nerves, and variable amount of fat.

Renal Pelvis

______: (renal lobe) appear striated or striped. Adult ususally has 8 to 15 of these. wide the base lied at the external edge of the medulla, where it meets the cortex known as the corticomedullary junction. Has grooves that converge at the papillae.

Renal Pyramids

structure within a nephron: makes up the remaining part of a nephron and it is composed of a simple epithelium resting on a basement membrane. Consist of 3 continuous sections: proximal convoluted tubule, neohron loop, and the distal convoluted tubule.

Renal Tubule

Identify the sequence of vascular structures through which blood flows into the kidneys, to the nephron and out of the kidneys

Renal artery Segmental artery Interlobular artery Arcuate artery Interlobular artery Afferent arteriole Glomerulus Efferent arteriole Peitubular cap Interlobular vein Arcuate vein Interlobular vein Renal vein

_____: maximum plasma concentration of a substance that can be transported in the urine

Renal threshold

List the substances that are reabsorbed by the tubbular system.

Sodium (Na+) Water (H2O) Potassium (K+) HCO3- Calcium (Ca2+)

______: (reflex in controlling urination) filling of urinary bladder with urine moves through the ureters fro kidneys. Varying nerve signals conducted by sympathetic axons cause smooth muscle cell of detrusor of urinary bladder wall to relax, allows bladder to accomodate urine. Internal urethral sphincter to contract so urine is retained within the baldder.

Storage Reflex.

____:(extrinsic factor that regulates GFR) activation of sympathetic division results in a decreased GFR through vasoconstriction of afferent arteriole and a decrease surface area of the filtration membrane. Renin and angiotensin II together increase GFR.

Sympathetic nervous system (renin-angiotensin II)

_____ segements of the limbs in the nephron loop have a simple cuboidal epithelium lining.

Thick segment

______ segments of the limbs in the nephron loop have a simple squamous epithelium lining.

Thin segment

What is the primary function of the nephron loop?

To create a gradient for urine concentration and water conservation.

______: is the maximum amount of a substance that cna be reabsorbed across the tubule epithelium in a given time period.

Transport maximum

______: (structure of urinary bladder) posterior triangular area of urinary bladder wall. Functions as a funnel to direct urine into the urethra as the bladder wall contracts to eliminate stored urine.

Trigone

____: fluid in the tubules of the kidney

Tubular fluid

_____: occurs when components within the tubular fluid move by membrane transport processes (diffusion, osmosis, active transport) form renal tubules, collecting tubules and collecting ducts across their walls and return to blood within the peritubular capillaries and vasa recta.

Tubular reabsorption

______: movement of solutes by active transport out of the blood within peritubular and vasa recta capillaries into tubular fluid. Materials moved selectively into the tubules to be eliminated/ excreted form body. secretions results in excretion.

Tubular secretion

_____: (intrinsic factor that regulates GFR) based on the detection of NaCl levels in the tubular fluid (juxtaglomerular apparatus helps maintain normal glomerular bp with this)

Tubuloglomerular feedback

________: extend from the kidneys to the urinary bladder, retroperitoneal. Attach to the posterior abdominal wall. Main fucntion: to transport urine to the urinary system

Ureters

_______: located in females posterior to clitoris and anterior to vaginal orifice. Male runs from internal urethral orifices of bladder to the external urethral orifices located at the tip of glans penis. Main function: conducts urine to exterior, in males also transports semen but not both at the same time.

Urethra

____: analysis of the urine to help assess the state of a person's health. This test can reveal: presence of leukocytes, blood, bacteria or fungi, also nitrituia

Urinalysis

__________: located retroperitoneally in pelvis just posterior to pubic symphysis. Main function: temporarily stores urine prior to urination

Urinary Bladder

______: your bodys liquid waste, mainly made of salt and chemicals called urea and uric acid

Urine