Lecture 11: The Urinary System Flashcards
what is urine
-clear, sterile liquid, different substnaces
-95% water and 5% solutes
-concentration dpends on: osmotic movement of H2O across walls or tubules and collecting ducts
what are the nitrogenous wastes (solutes found in urine)
-urea: from amino acid breakdown; largest solute component
-uric acid: from nucleic acid metabolism
-creatinine: from metabolite of creatine phosphate
what are some other normal solutes foundin urine
-Na+, K+, PO43–, and SO42–, Ca2+, Mg2+ and HCO3–
-abnormally high concentrations of any constituent, or abnormal componenets such as blood proteins, WBCs, and bile pigments, may indicate pathology
what are some abnormal urinary constituents (components)
albumin, glucose, RBCs, ketone bodies, bilirubin, urobilinogen, casts, microbes
What is glucose (in urine)
Presence of glucose in urine-glucosuria (gloo-kö-SOO-ré-a)-usually indicates diabetes mellitus. Occasionally caused by stress, which can cause excessive epinephrine secretion. Epinephrine stimulates breakdown of glycogen and liberation of glucose from liver.
What are RBCs (in urine)
Presence of red blood cells in urine-hematuria (hem-a-TOO-re-a)— generally indicates pathological condition. One
cause is acute intlammation or urinary organs due to disease or irritation trom kidney stones. Other causes: tumors, trauma, kidney disease, contamination of sample by menstrual blood.
What are ketone bodies (in urine)
High levels of ketone bodies in urine-ketonuria (ke-to-NOO-re-a) —may indicate diabetes mellitus, anorexia,
sorvation, or too lucie carDon vorate in dier
What is bilirubin (in urine)
When red blood cells are destroyed by macrophages, the globin portion of hemoglobin is split off and heme is converted to biliverdin. Most biliverdin is converted to bilirubin, which gives bile its major pigmentation. Above-normal level of bilirubin in urine is called bilirubinuria
What is urobilinogen (in urine)
Presence of urobilinogen (breakdown product of hemoglobin) in urine is called urobilinogenuria (‘-rö-bi-lin’ -o-je-NOO-re-a). Trace amounts are normal, but elevated urobilinogen may be due to hemolytic or pernicious anemia, infectious hepatitis, biliary obstruction, jaundice, cirrhosis, congestive heart failure, or infectious mononucleosis.
What are casts (in urine)
Casts are tiny masses of material that have hardened and assumed shape of lumen of tubule in which they formed, from which they are flushed when filtrate builds up behind them. Casts are named after cells or substances that compose them or based on appearance (for example, white blood cell casts, red blood cell casts, and epithelial cell casts that contain cells from walls of tubules).
What are microbes (in urine)
Number and type of bacteria vary with specific urinary tract infections. One of the most common is E. coli. Most common fungus is yeast Candida albicans, cause of vaginitis. Most frequent protozoan is Trichomonas vaginalis, cause of vaginitis in females and urethritis in males.
what are the 4 different normal physical characteristics of urine
- colour and transparency
- odor
- pH
- specific gravity
what is normal colour and trnasparency of urine
-clear/transparent
-cloudy may indicate urinary stract infection
-pale to deep yellow from urochome: pigment from hemoglobin breakdown, yellow colour deepends with increased concentration
-abnormal colour: (pink, brown, smoky) can be cause by certain foods, bile pigments, blood, drugs
what is normal odor of urine
-slightly aromatic when fresh
-develops ammonia odor upon standing: bacteria metabolize urea
-may be altered by some drugs or vegetables
-disease may alter smell: pts with diabetes may have acetone smell to urine
what is the normal pH or urine
-Urine is slightly acidic (~pH 6, with range of 4.5 to 8.0)
-Acidic diet (protein, whole wheat) can cause drop in pH
-Alkaline diet (vegetarian), prolonged vomiting, or UTIs can cause
an increase in pH
what is the specific gravity of normal urine
-Ratio of mass of substance to mass of equal volume of water
(specific gravity of H2O = 1)
-Ranges from 1.001 to 1.035
where does urine trnasportation, storage, and elimination take place
takes place in urinary tract
-ureters
-urinary bladder
-urethra
what are the ureters
-Paired muscular tubes
-Connect kidneys to urinary bladder
-Begin at renal pelvis and pass over psoas major
-Penetrate posterior wall of urinary bladder at oblique angle
-Ureteric orifices: slit-like rather than rounded, which Prevents backflow of urine when urinary bladder
contracts
describe the three layers of the ureter wall
- Inner mucosa – transitional epithelium and lamina propria
- Middle muscularis – longitudinal and circular bands of smooth muscle
- Outer Adventitia (CT layer) – continuous with fibrous capsule and peritoneum
what is the peristaltic actions of smooth muscles in the urinary system
~ every 30 seconds
-Begin at renal pelvis
-Sweep along ureter
-Forcing urine toward urinary bladder
-Rate of peristalsis adjusted to rate of urine formation
describe the anatomy of the urinary bladder
-Muscular sac for temporary storage of urine
-On pelvic floor posterior to pubic symphysis
-Males: prostate inferior to bladder neck
-Females: anterior to vagina and uterus
-Has openings for ureters and urethra
-Trigone: Smooth triangular area outlined by openings for ureters and urethra, Infections tend to persist in this region
describe the layers of the urinary bladder
- Mucosa: transitional epithelial mucosa
- Muscular layer: thick detrusor muscle which contains three layers of smooth muscle: Inner and outer longitudinal layers with circular middle layer
- Fibrous adventitia, except on superior surface where it is covered by peritoneum
what is the urine storage capacity
the bladder:
-Collapses when empty and rugae appear
-Expands and rises superiorly during filling without significant rise in internal pressure
-Moderately full bladder is ~12 cm long and can hold ~ 500 ml (1 pint)
-Can hold twice that amount if necessary but can burst if overdistended
what is the urethra and what does its epithelium consist of
-Muscular tube that drains urinary bladder
Epithelium – consists of:
-Mostly pseudostratified columnar epithelium, except:
-Transitional epithelium (urothelium) near bladder
-Stratified squamous epithelium near external urethral orifice
describe the two sphincters of the urethra
- internal urethral sphincter: involuntarily controls opening and closing of urethra
- external urethral sphincter: in deep muscles of perineum (voluntarily controls opening and closing of urethra
what does the male urethra carry and what are its regions
-Carries semen and urine; ~ 20 cm long
Three Regions:
1. Prostatic urethra (2.5 cm): within prostate
2. Membranous urethra – intermediate part (2 cm): passes through urogenital diaphragm from prostate to beginning of penis
3. Spongy urethra (15 cm): passes through penis; opens via external urethral orifice
describe the female urethra
-3–4 cm; tightly bound to anterior vaginal wall; carries urine
-External urethral orifice: anterior to vaginal opening; posterior to clitoris
what is the comparison between the male and femlae urethra
-it is 5x longer in males than females
-it is dividied into three segments in males but is only one short tube in females
-the urethra is a common duct for the urinary and reproductive system in males. these two system are entirely seperate in females
what is micturition (urination or voiding)
-Discharge of urine involves voluntary and involuntary muscle contractions
-Stretch receptors trigger a spinal reflex, which we learn to control in childhood
-Urethra carries urine from the internal urethral orifice to the exterior of the body
describe micturition in infants
-Lack voluntary control over urination
-Necessary corticospinal connections are not yet established
what is incontinence
-Inability to control urination voluntarily
-May be caused by trauma to internal or external urethral sphincter
describe the urine voiding reflex
-Involves spinal reflexes and pontine micturition center
-When bladder contains about 200 mL of urine, urge to urinate appears
-Stretch receptors send impulses to pontine micturition center (PMC), initiating sacral spinal reflexes: detrusor contracts, internal & externa; urethral sphincters relax
describe the urine storage reflex
I-nvolves spinal reflexes and pontine storage center
-Afferent impulses from stretch receptors in urinary bladder stimulate
sympathetic outflow: inhibiting contraction of detrusor & Stimulating contraction of internal urethral sphincter
-pontine storage center inhibits urination by: decreasing parasympathetic activity, and contracting external urethral sphincter
what is the formation of dilute or concentrated urine
-Medullary osmotic gradient can now be used to form
dilute or concentrated urine
-Without gradient, would not be able to raise urine concentration > 300 mOsm, to conserve water
-Overhydration produces large volume of dilute urine
-ADH production decreases; urine falls ~100 mOsm
-If aldosterone (not shown) present, DCT and collecting duct cells remove Na+ and other ions are removed → H2O dilute to ~50 mOsm
describe the formation of dilute urine
-Glomerular filtrate and blood have same osmolarity at 300 mOsm/L
-But tubular osmolarity changes due to medullary conc. gradient
-When dilute urine is formed, osmolarity in the tubule:
* Increases in the descending limb
* Decreases in the ascending limb
* Decreases more in the collecting duct
-Thick Ascending Limb: Symporters actively resorb Na+, K+, Cl–, Low water permeability, Solutes leave & water stays in tubule
-Collecting Duct: Low water permeability in absence of ADH
what causes the formation of concentrated urine
-Dehydration produces small volume of concentrated urine
-Maximal ADH is released; urine rises to ~1200 mOsm
-Severe dehydration: 99% water reabsorbed and returns to the blood
-Movement of H2O also carries urea into the medulla, contributing to its osmolarity
describe the formation of concentrated urine
-juxtamedullary nephrons with long loops
-Osmotic gradient is created by the countercurrent multiplier
-Solutes pumped out of ascending limb, but water stays in tubule
-Medulla osmolarity is increased
-In presence of ADH, collecting ducts become very permeable to
water
-Tubular fluid there becomes very concentrated
what are diuretics
-Chemicals that enhance urinary output:
-ADH inhibitors, such as alcohol
-Na+ reabsorption inhibitors (and resultant H2O reabsorption), such as caffeine or drugs for hypertension or edema
-Loop diuretics inhibit medullary gradient formation
-Osmotic diuretics: substance not reabsorbed, so water remains in urine; for example, in diabetic patient, high glucose concentration pulls water from body
what are urinary tract infections (UITs)- causes
-improper toilet habits: wiping bacl to front after defecation, short urethra of females can allow fecal bacteria to easily enter urethra
-most UTIs occur in sexually active women: 40% of women get urinary tract infections. intercourse drives bacteria from vagina and external genital region toward bladder; use of spermicides magnifies problem
what is urethritis
inflammation of urethra
what is cysitis
inflammation of bladder
what is trigonitis
inflammation of trigone
-symptoms: painful urination, pelvic pain, blood in urine, urgent need to urinate
-causes:
a) hormonal imbalances, estrogen and progesterone may play a role in the cellular changes that occur with pseudomembranous trigonitis
b) prolong use of catheter irritates the floor
c) recurrent UTIs
what is anuria
abnormally low urinary output (less than 50ml/day)
-may indicate that glomerular blood pressure is too low to cause filtration
-renal failure and anuria can also result from situations in which nephrons ston functioning
-examples: acute nephritis, transfusion reactions, and cursh injuries
describe the effects of aging on the urinary system
Age-related changes:
-Nephrolithiasis (formation of calculi)
-Decrease in number of functional nephrons
-Reduction in GFR
-Reduced sensitivity to ADH
-Problems with urinary reflexes:
-External sphincter loses muscle tone
-Control of urination can be lost due to a stroke, Alzheimer’s disease, and other CNS problems
-In males, urinary retention may develop
Beta oxidation and the urinary system
The kidney is a highly metabolic organ and requires a large amount of ATP to maintain its filtration-reabsorption function, and mitochondrial fatty acid β-oxidation serves as the main source of energy to meet its functional needs
