Urinary System Flashcards
How is urine made?
By filtering the blood.
What does normal urine contain?
Water, salts, Urea, Metabolites and Small proteins.
What does abnormal urine contain?
Large proteins, RBC and glucose.
To be effective the urinary system needs to be?
Adaptable to meet the bodies changing needs.
What are the main components of the Urinary system?
2 kidneys, 2 ureters, bladder and urethra.
Renal refers to what?
Kidneys.
Where are the kidneys located?
Between T12 and L3 and the 11th and 12th rib.
What is the hilum?
A concave notch on the medial surface of the kidneys. This is where vessels go in and out.
What does retroperitoneal mean?
Located on posterior abdominal wall, covered on anterior side by peritoneum.
What are the three supportive tissue layers that protect the kidneys?
The renal fascia (anterior and posterior), the perirenal fat capsule and the fibrous capsule.
What are the three regions of the kidney?
Cortex, medulla and pelvis.
What are the 6 major structural landmarks of the kidney?
Fibrous capsule
Renal cortex
Renal medulla
Renal pyramid
Renal column
Kidney lobe
What structure makes up majority of the kidney lobe?
Nephrons
What order does urine travel through the system?
Papilla –> minor calyx –> major calyx –> renal pelvis –> ureter.
A special type of imaging, that only shows up in the urine is called?
Pyelogram
Where does filtration occur?
In the cortex of the kidney inside the glomerular capillaries.
Where does the Renal artery arise from?
Abdominal aorta.
What vessel delivers blood from the arteries to glomerulus?
The afferent arteriole.
Where does the efferent arteriole carry blood to and from?
From the glomerulus to the peritubular capillaries.
In what order is blood supply INTO the cortex to be filtered?
Abdominal aorta –> renal artery –> series of arteries –> afferent arteriole –> glomerular capillary.
In what order is blood supply AWAY from the cortex after being filtered?
Glomerular capillary –> efferent arteriole –> peritubular capillaries –> series of veins –> renal vein –> inferior vena cava.
What is the nephron?
Microscopic functional unit of the kidney that filters blood and produces urine.
Which kidney is more inferior?
Right.
How many nephrons per kidney?
1 million.
What are the two types of nephron?
Cortical and Juxtamedullary nephrons.
How are nephrons named?
Based on their location.
What is the function of a nephron?
Selectively filter blood, return stuff into the blood and carry waste away from storage and expulsion.
What is each nephron comprised of?
A glomerular capsule, renal tubules and a collecting duct.
What is each nephron associated with?
A glomerulus and peritubular capillaries.
What is the function of the Glomerular capillaries?
Specialised for filtration, therefore they have thin walls with a single layer of fenestrated endothelial cells.
What vessels feed and drain blood to and from the Glomerular capillaries?
Arterioles.
What is the function of the Peritubular capillaries?
Specialised for absorption, they wrap around the renal tubules. They receive filtered blood from the glomerulus via the efferent arterioles and they also receive reabsorbed filtrate from the nephron.
What is the renal corpuscle?
Where the capillary and nephron meet.
Where is the filtration barrier located?
The renal corpuscle.
What wraps around the glomerulus?
The glomerular capsule.
The Glomerular capsule is composed of what two layers?
Outer parietal layer of simple squamous cells and an Inner visceral layer of podocytes.
Between the two layers of the Glomerular capsule is the capsular space, which receives what?
Receives filtrate.
What are podocytes?
Specialised epithelial cells that surround the glomerular capillaries. They are very branched which creates pedicels which form filtration slits between them. Filtered blood (filtrate) goes through these slits and passes into the capsular space.
What is the filtration barrier?
Membrane that lies between blood and capsular space and allows free passage of water and small molecules and restricts passage of most proteins and RBCs.
What are the three layers of the filtration barrier?
Fenestrated endothelium of glomerular capillary, fused basement membrane and filtration slits between the pedicels of the podocytes.
Which two structures form the renal corpuscle?
Glomerulus and glomerular barrier.
What happens after filtration?
urine is waste fluid and solutes are filtered from the blood. Not everything that is filtered is excreted. Some filtrate is reabsorbed and some of what wasn’t filtered is secreted into the nephron.
Urine = ?
Filtered - Reabsorbed + Secreted
What occurs in the Proximal convoluted tubule (PCT)?
Bulk reabsorption.
What surrounds the PCT?
Peritubular capillaries.
What is the structure of the PCT?
Cuboidal epithelial cells, Dense microvilli (brush border) on luminal membrane, highly folded basolateral membrane, leaky epithelium and many mitochondria for active transport.
Explain the structure of the nephron loop?
Thick and thin ascending and descending limb.
What is the Distal convoluted tubule (DCT)?
Cuboidal epithelium, no brush border, fewer mitochondria. Where reabsorption occurs under the influence by aldosterone.
What is the Collecting Duct?
Where filtrate from several DCTs drain into one collecting duct, which empty at papilla.
What is the structure of the collecting duct?
Wall of simple cuboidal epithelium, principal cells for reabsorption and intercalated cells for acid/base balance.
What is transitional epithelium?
Stratified, rounded cells found along the urinary tract. They are flattened when stretched and used for protection.
What are Ureters?
Arise from each renal pelvis at each hilum, they are small tubes that carry urine from kidneys to the bladder. The ureters descend retroperitoneally through the abdomen.
What process moves urine to the bladder?
Peristaltic waves.
What are the three layers of the Ureter?
Transitional epithelium, muscularis and adventitia.
Why do the ureters run obliquely through the wall of bladder?
They act as a sphincter/valve compressed by increased bladder pressure to prevent backflow.
What does the urinary bladder consist of?
Ureters, Bladder wall, Rugae, Trigone and Urethra.
What is the purpose of Rugae?
Allow for expansion without increasing the pressure.
What is the difference between an empty and fill bladder?
Empty - Pyramidal and lies within the pelvis.
As the bladder fills, it becomes more spherical, it expands superiorly into abdominal cavity and can be palpated above the pubic symphysis.
What is the name of the bladder muscle?
Detrusor muscle.
Why does the bladder have a random network of fibres and no distinct layers?
Because we do not want a motility pattern, we just want to collapse the sac as quickly as possible.
What is the urethra?
Thin walled muscular tube.
What are the epithelial changes in the urethra?
Transitional epithelium near the bladder, columnar and stratified squamous near external opening.
Is the male or female urethra shorter?
Female.
Is the urethra part of the reproductive system?
Yes.
What urethral sphincter is under involuntary control?
Internal.
What is the process of urination?
Bladder fills with urine and expands, an action potential is generated from the stretch receptors to the brain. The urgency of the signals increases as bladder fills more. Internal sphincters then relax, then conscious relaxation of the external sphincter allows for urination.
Why do we need kidneys?
To control what is in our blood and how much blood we have.
What are the major functions of the kidney?
Endocrine
Metabolic
pH regulation
Filter blood
Water homeostasis
Salt/Ion homeostasis
Re-absorption of nutrients
Excretion of medications, toxins and metabolites.
What is the endocrine function of the kidneys?
The kidneys are the detector for the amount of oxygen in our blood and therefore generate EPO production which stimulates bone marrow to produce more red blood cells.
What do the kidneys make glucose from?
Lactate
During fasting, or when the body is under stress what process do the kidneys regulate?
Gluconeogenesis
What function of the kidney is very tightly controlled?
pH regulation
What term describes urine that is too acidic?
Acidosis
What term describes urine that is too alkaline?
Alkalosis
What molecule is the main buffer of the blood?
Bicarbonate.
How is HCO3- (bicarbonate) concentration in the blood controlled?
Exhalation of CO2 from the lungs and reabsorption of HCO3- and secretions of H+ in the kidneys.
How do the kidneys maintain salt/ion homeostasis?
The kidneys secrete potassium (K+) to maintain balance. High potassium leads to hyperkalemia which can stop the heart therefore is lethal.
What is the process of filtering lipophilic drugs and toxins?
They are excreted by the kidneys AFTER metabolism in the liver.
What is the process of filtering hydrophillic drugs and toxins?
Excreted directly by the kidneys .
What are the three basic functions of the nephron?
Filtration, reabsorption and secretion.
What is absorption?
Bringing into the body/blood for the first time (from the GIT)
What is re-absoption?
Bringing a substance BACK into the body/blood (from the kidneys)
What is secretion?
From the blood, via the peritubular fluid and into the nephron (tubular fluid).
What is filtration?
Creates a plasma-like filtrate of the blood.
Where does filtration occur?
in the glomerulus.
Most substances in plasma are freely filtered (pass through filtration barrier) except for what?
Proteins and substances bound to proteins.
What are the major functions of the Proximal tubule?
Bulk re-absorption of ions (sodium) water and nutrients (glucose). And secretion of metabolites, medications and toxins.
What are the major functions of the Nephron loop?
Bulk re-absorption of ions (sodium) and water.
What are the major functions of the Distal tubule and collecting duct?
Fine-tuning of electrolyte and water re-absorption.
What would you see in abnormal urine?
Orange, red, brown or blue/green colour. It would have a sweet taste or smell fruity or rotten. This may indicate increase of ketones or an infection.
Define osmolarity?
The total number of solute molecules in a solution.
Define tonicity?
The effect a solution has on cell volume due to net movement of water.
A swollen cells refers to water?
Hypotonic.
What determines glomerular filtration?
Renal blood flow, filtration barrier and driving forces.
What are the four driving forces for glomerular filtration?
Glomerular hydrostatic pressure, Blood colloid osmotic pressure, capsular hydrostatic pressure and capsular colloid osmotic pressure.
Together the 4 pressures of glomerular filtration determine what?
Net filtration pressure.
What is the filtration fraction?
How much of the kidneys blood (plasma) flow is filtered?
What is the glomerular filtration rate (GFR)?
How much plasma is filtered per minute.
What is filtered load?
How much of a substance is filtered per minute.
What is renal clearance?
How much plasma is cleared of substance per minute.
What is renal clearance used for?
To quantify how a substance is handled by the kidneys and estimate the GFR.
What is the correlation between renal clearance and glucose?
Glucose is all re-absorbed. This means no plasma has been “cleared” of glucose. Therefore no glucose is left to be secreted in the urine.
What are the values for total body water?
male: 60%
female: 55%
What fraction of TBW is extracellular fluid?
1/3
What fraction of TBW is intracellular fluid?
2/3
How much of the extracellular fluid is plasma?
1/5
What controls the balance of TBW?
Urine output.
What are the three important places where water is reabsorbed in the nephron?
Proximal convoluted tubule (PCT), the descending limb and the collecting duct.
What is the ascending limb of the nephron loop permeable too?
Solutes.
How is water reabsorbed in the nephron?
98% of water reabsorption occurs by Bulk (obligatory) water reabsorption in the descending limb and 2-8% is regulated (facultative) water reabsorption which occurs in the collecting duct.
What are the four important places where sodium is reabsorbed in the nephron?
PCT, ascending limb, the distal convoluted tubule (DCT) and the collecting duct (CD).
Where is majority of sodium reabsorbed?
The PCT
What drives water reabsorption in the proximal tubule?
Na+ reabsorption.
What type of epithelium is the proximal tubule?
“leaky”.
What regulates sodium reabsorption?
Aldosterone (RAAS).
What regulates water reabsoption?
Anti-diuretic hormone (ADH).
How is body osmolarity regulated by ADH?
There is a decrease in TBW which causes an increase in ECF osmolarity/ sodium conc. This is detected by osmoreceptors in the hypothalamus. Increased ADH is released from the posterior pituitary. An insertion of aquaporins in apical membrane of the collecting duct cells then increases water permeability and increases water reabsorption. This then decreases urine volume and ECF osmolarity returns to normal.
How does aldosterone regulate ECF volume?
The decrease in blood volume is detected by pressure receptors in the kidney. This causes activation of the release of aldosterone from the adrenal gland. This then increases the sodium channels in apical membrane of collecting duct which results in increase sodium and water reabsorption and blood volume returns to normal.
