Urinary System Lecture 1

8/8/2019 Urinary System Lecture 1

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Urinary System

PowerPoint designed by fellow student J.H.

A few extras were added by me.

http://journey2nursing.blogspot.com 2010


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Urinary (Renal) System

Remove cellular waste from blood and transport the wastes to outside thebody

Included organs: 2 kidneys, 2 ureters,1 urinary bladder (transitionalepithelium) and 1 urethra



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Kidneys

Located on either side of vertebral column, high on posterior wall ofabdominal cavity

Right is slightly lower than left

Retroperitoneal - behind the parietal peritoneum- held by adipose (Renal Fat) and connective tissue (Renal Fascia)



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Structures of Kidneys

Renal sinus - hollow with renal papillae

Renal pelvis - ureter expands to create this

Contains major calyx and minor calyx ( one pyramid drains to minor)



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Layers of Kidney

Medulla- inner layer- contains pyramids, papillae and pores

Cortex- outer layer (next to capsule)- contains columns (between pyramids)



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Functions of Kidneys

Remove metabolic wastes from the blood- Proteins, Formed Elements

Regulate RBC by Erythropoetin

Regulate BP by secreting Renin from Juxtaglomerular cells

Regulate blood volume, composition, calcium ion absorption, and pH



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Blood supply of Kidney

Renal artery - branches to- interlobar- arciform- interlobular arteries- afferent arterioles

Efferent arterioles - turn into

- peritublar capillaries- vasa recta

Venous system - blood returns through a series of vessels that correspondto the arterial pathways to inferior vena cava



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Nephrons

Nephrons are the functional units of the kidneys

One million per kidney (approximately)

Types:

Cortical- most numerous, corpuscles near the surface of the kidney

Juxtamedullary- corpuscles near the medulla and the loops dip down

deeper



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Renal corpuscle

Contains :

Glomerulus- ball of blood capillaries

Glomerular (Bowmans) capsule - 2 layers simple squamousepithelium

Visceral layer sticks to glomerulus

- contains cells called podocytes (slit pores) Parietal layer



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Renal Tubules

Proximal convoluted tubule (simple cuboidal epithelium)

Nephron loop (Loop of Henle)- Descending Limb- Ascending Limb

Distal convoluted tubule

Collecting duct - empties into the minor calyces of the renal pelvis

- DCT and CD are impermeable to water without ADH- DCT and CD are impermeable to Na+ without aldosterone

Juxtaglomerular Apparatus - Located at pt of contact b/n DCT and theafferent and efferent arterioles

Cells Present:- Macula Densa- Juxtaglomerular cells

- Renin secretion tells hypothalamus to release ADH



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Blood supply of a nephron

Afferent arteriole - brings blood to glomerulus

Glomerulus - under high pressure (filtration here)

Efferent arteriole - gives rise to peritubular capillary system- Surrounds renal tubule (low pressure)

Peritubular capillary

Vasa recta - capillary loops down into medulla Veins - receive blood from vasa recta



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Urine Formation Urine = Glomerular filtrate - renal absorption + renal secretion

Glomerular filtration - substances filtered out of blood in glomerular capillaries intothe capusle called FILTRATE-125mL of glomerular fluid/min- most is reabsorbed

Filtrate- similar to interstitial fluid

Glomerular capillaries are more permeable than others

Filtration pressure: hydrostatic pressure pushes out of blood, osmotic in blood andhyrdo of capsule pushes back into blood

Filtration rate: due to hydrostatic pressure in glomerular capillaries and varies with

rate of blood flow through glomerulus Varies with diameter of arterioles* decrease in afferent decreases gfr; a decrease

in efferent increases gfr

Osmotic pressure goes up in glomerulus rate goes down

Hydrostatic pressure in glomerular capsule goes up gfr goes down

Regulation of gfr- mostly constant- increase in sympathetic nerve activity decreasesgfr

Autoregulation: ability of an organ or tissue to maintain constant blood flow BP up GFR down

Fluid volume up GFR up

BP down and NaCl down JG appartus secretes renin



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Maintaining of Na

Vasoconstriction

Aldosterone secretion - increases Na absorption and H20 in dct and cd

ADH secretion increases water absorption in DCT and CD

Thirst center in hypothalamus stimulated

All causing BP to go up

ANP from stretching of right atrium of heart causes GFR to go up andincreases Na and H20 excretion by the kidneys = lowering BP



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Tubular Reabsorption

Substances are selectively reabsorbed from filtrate and go to peritubularcapillaries kept in the body (Na actively reabsorbed)

Peritubular Capillaries- permeable contents under low pressure

- PCT - Most reabsorption occurs here due to microvilli

a) Glucose - secondary active transport as Na is reabsorbed

b) amino acids - secondary active transport as Na is reabsorbedc) water - osmosis

d) proteins - pinocytosis (cell drinking)

e) Na actively reabsorbed and water and charged ions follow

All substances reabsorbed by active and secondary active transport havethresholds that will spill over to urine when reached.



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Tubular Reabsorption 2

Nephron loop - regulates urine concentration and volume this depends onmovement of Na.

- Na ions are concentrated in medulla by counterconcurrentmechanism

- Cl- is pumped out by ascending limb Na follows

- NaCl in medulla draws water out of descending limb- NaCl reenters loop in descending limb pumped out by ascendinglimb

- NaCl concentration in medulla is maintained by vasa recta

- NaCl moving in/out of loop keeps us from losing too much H20 inour urine

Filter out 180 liters of urine but only urinate 2 liters per day



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Tubular Reabsorption 3

DCT and Collecting Duct

impermeable to water unless ADH is present

Impermeable to Na unless aldosterone is present

Urea Non polar by product of amino acid metabolism. It crosses by simplediffusion. 50% is excreted in urine. The most abundant solute in urine.

Uric Acid - from the metabolism of nucleic acids, its reabsorbed by activetransport.



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Tubular Secretion

Substances pumped into filtrate

H+ - secreted so pH is often acidic, secreted by active transport inproximal and distal tubules. This is the only way to get H+ out of body.

K+ - secreted passively in distal tubule and CD due to electricalattraction of charges in the lumen of the tubule.



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Urine

95% water

Urea main solute, forms from amino acid breakdown

Uric Acid forms from nucleic breakdown

Creatinine - from creatine phosphate (energy molecule in skeletal muscles)

Other stuff varies due to diet:

Food coloring Oil

Ketones from lipid metabolism

Ions

Amino Acids



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Ureters

Ureters - tubular organ extending from each kidney to bladder

Wall has mucous, muscular, and fibrous layers

Muscular layer allows for peristalsis forcing urine to bladder

Enters into bladder through the back of the trigone in the bladder ( thisarea is not transitional/ not stretchy)



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Urinary bladder

Distensible organ stores urine and forces it into urethra Openings of urethra and ureters are located in the three angles of the trigone

Mucosa layer - transitional epithelial tissue

Muscular layer - forms detrusor muscle which forms internal urethralsphincter

Micturition - process of urinating

Contraction of detrusor muscle and relaxation of external urethral sphincter

Reflex:

Stretch receptors stimulated by distension of bladder wall

Reflex center in sacral portion of spinal cord send parasympathetic impulses todetrusor muscle to relax and urinate

Increased pressure in bladder opens internal urethral sphincter

2

nd

reflex opens external sphincter unless voluntarily controlled Nerve centers in brain stem and cerebral cortex also control urination



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Urethra and dialysis

Urethra - carries urine to outside

Smaller in females empties between labia minora

3 parts in males: prostatic, membranous, penile. Conveys products ofreproductive organs and empties at tip of penis.

Dialysis

CAPD - Continuous Ambulatory Peritoneal Dialysis. Solution put into

abdomen and after several hours it contains substances normallyexcreted in urine. Fluid is removed and replaced

Hemodialysis - blood flows through machine. Waste products leave theblood and enter the machine through diffusion



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Diseases

Polycystic

Glomerulonephritis

Glucosuria glucose in the urine

Nephrotic Syndrome

Cancer

Stones



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Thanks!

A big thank you to my fellow

Anatomy and Physiology

students who provided pictures,

support, and study help.


Urinary System Lecture 1

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