BIO 211 (UNIT # 3) CH 25: The Urinary System

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Mr Daigle Bio 211 (A&P 2) CCTC Spring 2011

What is a Nephron?

Structural and functional units that form urine.

How many nephrons are their per kidney?

~1 Million.

What are the two main parts of a Nephron?

Glomerulus, and Renal Tubule.

What is a Glomerulus?

Part of a Nephron, that is a tuft of capillaries.

What is a Renal Tubule?

Part of a Nephron, that begins as a cup-shaped glomerular (Bowman's) capsule, surrounding the glomerulus.

What is a Renal Corpuscle?

Glomerulus + its glomerular capsule.

What is the function of a Fenestrated glomerular capillaries?

Allows filtrate to pass from plasma into the glomerular capsule.

What are the Renal Tubules?

Proximal Convoluted Tubule, Loop of Henle, and Distal Convoluted Tubule.

What is the Proximal Convoluted Tubule?

PCT - Functions in reabsorption and secretion. Confined to the cortex.

What is the Loop of Henle?

Thin segment ususally within the descending limb. Freely permeable to water. Thick segment of ascending limb.

What is the Distal Convoluted Tubule?

DCT - Functions more in secretion than reabsorption. Confied to the cortex.

What are Collecting ducts?

Receive filtrate from many nephrons. Fuse together to deliver urine through papillae into minor calyces.

What is the function of the Glomerulus?

Specialized for filtration.

Why is blood pressure high in Glomerulus?

Afferent arterioles are large in diameter than efferent arterioles. Arterioles are high-resistance vessels.

What are Pertibular Capillaries?

Low-pressure, porous capillaries adapated for absorption.

Where do Pertibular Capillaries arise from?

Efferent arterioles.

What do Pertibular Capillaries cling to?

Adjacent renal tubules in the cortex.

What do Pertibular Capillaries empty into?

Venules.

What is the Vasa Recta?

Rect = Straight, Vasa = Vessels. Long vessels parallel to long loops of Henle.

Where does the Vasa Recta arise from?

Efferent arterioles of the juxtamedullary nephrons.

What is the function of the Vasa Recta?

Function in formation of concentrated urine.

How many times a day does the kidneys filter the bodys entire plasma volume?

60 times each day.

What is Filtrate?

Blood plasma minus proteins.

What is Urine?

<1& of total filtrate. Contains metabolic wastes and unneeded substances.

What are the Mechanisms of Urine Formation?

Glomerular filtration, Tubular Reabsorption, and Tubular Secretion.

What is Tubular Reabsorption?

Tubules to blood. Returns all glucose and amino acids, 99% of water, salt, and other components to the blood.

What is Tubular Secretion?

Blood to tubules. Reverse of reabsorption: selective addition to urine.

What is Glomerular Filtration Rate controlled by?

Intrinsic controls and extrinsic controls.

What are the Intrinsic controls of Glomerular Filtration?

Renal Autoregulation - Acts locally wihin the kidney.

What are the Extrinsic Controls of Glomerular Filtration?

Nervous and endocrine mechanisms that maintain blood pressure, but affect kidney function.

What are Intrinsic Controls regulated by?

Smooth muscle in response to stretch.

What is the function of the Proximal Convoluted Tubule?

Site of most reabsorption. 65% of Na+ and water. All nutrients. Ions. Small proteins.

What is the function of the Loop of Henles Descending limb?

H20.

What is the function of the Loop of Henles Ascending Limb?

Na+, K+, and Cl-.

What is the function of the Distal Convoluted Tubule and Collecting Duct?

Reabsoprtion is hormonally regulated - Ca2+ (PTH), Water (ADH), and Na+ (Adosterone and ANP).

Where is Filtrate Diluted?

The ascending loop of Henle.

Where is Filtrate Diluted in the absence of ADH?

Continues into the renal pelvis as dilute urine.

How is conentrated urine formed?

ADH triggers reabsorption of H20 in the collecting ducts.

What is Facultative Water Reabsorption?

Water reabsorption that depends on the pressence of ADH. In the presence of ADH 99% of H20 in filtrate is reabsorbed.

What is the normal color and transparency for urine?

Clear, pale to deep yellow (due to urochrome).

What can alter the color of urine?

Drugs, vitamin supplements, and diet.

What can Cloudy Urine indicate?

A urinary tract infection.

What is the odor of urine?

Slightly aromatic when fresh.

What develops upon standing in Urine?

Ammonia odor.

What may alter the odor of Urine?

By some drugs and vegetables (asaparagus).

What is the pH of Urine?

Slightly acidic (~pH 6, with a range of 4.5 to 8.0)

What can alter the pH of Urine?

Diet, prolonged vomiting, or UTI.

What is the specific gravity of pH?

1.001 to 1.035, depending on solute concentration.

What are Renal Calculi?

Kidney stones form in renal pelvus.

What are Kidney stones formed of?

Crystallized calcium, magnesium or uric acid salts.

What can larger kidney stones do?

Block ureter, cause pressure and pain in kidneys.

What are the risk factors of Kidney stones?

May be due to chronic bacterial infection, urine retention, elevated Ca2+ in blood, higher pH of urine.

How are Kidney Stones treated?

Shock wave Lithotripsy.

What is Shock Wave Lithotripsy?

Ultrasonic shock waves to break up the calculi.

What is the Urinary Bladder?

Muscular sac for temporary storage of urine.

What is the location of the Urinary Bladder in Males?

Prostate gland surrounds the neck inferiorly.

What is the location of Urinary Bladder in Females?

Anterior to the vagina and uterus.

What is a Trigone?

Smooth trigangular area outlined by the openings for the ureters and the urethra. Infections tend to persist in this region.

What are the layers of the bladder wall?

Transitional epithelial mucosa, thick detrusor muscle (three layers of smooth muscle), and fibrous adventitia (peritoneum of superior surface only).

When does the Urinary Bladder Collapse?

When empty; rugae appear.

What does the Urinary Bladder Expand?

During filling, also rises superiorly without significant rise in internal pressure.

What are the Sphincters of the Urethra?

Internal and External.

What is the Internal Urethral Sphincter?

Involuntary (smooth muscle) at bladder-urethra junction. Contracts to open.

What is the External Urethral Sphincter?

Voluntary (skeletal) muscle surrounding the urethra as it passes through the pelvic floor.

How long is the Female Urethra?

3 - 4 cm. Shorter than males.

What is the location of the external urethral orfice in the Female?

Anterior to the vaginal opening, posterior to the clitoris.

What does the female urethra have an increased chance of?

Urinary Tract Infections due to shortness.

What does the Male Urethra Carry?

Semen and Urine.

What are the three regions of the Urethra of the Male?

Prostatic Urethra, Membranous Urethra, and Spongy Urethra.

What is the Prostatic Urethra?

2.5 cm - within prostate gland.

What is the Membranous Urethra?

2 cm - passes through the urogenital diaphragm.

What is the Spongy Urethra?

15 cm - passes through the penis and opens via the external urethral orifice.

What is Micturition?

Urinartion of voiding.

What are the three simultaenous events in Micturition?

Contraction of detruster muscle by ANS, Opening of internal urethral sphincter by ANS, opening of external urethral sphincter by somatic nervous system.

What is Reflexive Urination?

Urination in infants. DIstension of bladder activates stretch receptors. Excitation of parasympahtetic neurons in reflex center in sacral region of Spinal Cord. Contractor of the detruster muscle. Contraction (opening) of internal sphincter. Inhibition of somatic pathways to external sphincter, allowing its relaxation (opening).

What is frequent micturition in infants due too?

Small bladders and less concentrated urine.

Why is incontinence normal in infants?

Control of the voluntary urethral sphincter develops with the nervous system.

What accounts for 80% of all urinary tract infection?

E. coli bacteria.

What can Streptococcal infections cause?

Long term renal damage.

What can STD's do to urinary tract?

Inflame.

What are Diuretics?

Chemicals that enhance the urinary output such as any substance not reabsorbed (carries water out with it), substance that encourages diuresis by inhibiting the release of ADH (alcohol), and substances that inhibit Na+ reabsorption (caffeine).

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