HPA Urinary System 2013 Ppt

7/28/2019 HPA Urinary System 2013 Ppt

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Chapter 20

Urinary System

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Location of Kidneys is

Retroperitoneally

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Kidney structure

Composed of 2 layers: Outer: cortex & Inner : medulla

Lateral surface is convex, medial surface deeply concave

Medial side leads into a renal sinus where the entrance is termed the hilum

where blood vessels, nerves, lymphatics and the ureter enter/exit Superior end of the ureter expands to form a funnel shaped sac called the renal

pelvis

i) further subdivided into major calyces and further into minor calyces

ii) renal papillae project into each minor calyx from the renal medulla

The renal medulla is composed of conical masses called renal pyramids The renal cortex forms a shell around the medulla, its tissue dips into the

medulla between the renal pyramids, forming the renal columns

Cortex has its own protective covering called the capsule


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Kidneys

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Renal Blood Vessels

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Functions of the Kidneys

Main function is to regulate the volume,composition and pH of body fluids

Removes wastes which contain nitrogenous and

sulfur containing products of proteinmetabolism

Control the rate of RBC production viaerythropoietin

Regulates blood pressure by secreting renin Regulates absorption of calcium ions by

activating Vitamin D


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Renal Blood Vessels

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Renal Blood Vessels

Renal arteries supply the kidneys

carry about 15 to 30% of the total cardiac output daily

artery enters the kidney via the hilum and begins to branch into smaller

branches called interlobar arteries which pass between the pyramids Become the arcuate arteries and then the interlobular arteries and

eventually end as the afferent arterioles which will lead to the

nephron, the functional unit of the kidney

Blood will return to the IVC via the renal veins


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The Nephron

Each kidney contains about 1 million functional nephrons (at birth)

Each consists of a renal corpuscle and a renal tubule

Each corpuscle consists of:

i) a filtering unit called a glomerulusii) a sac-like structure called a glomerular capsule (Bowmans)

The afferent arteriole will give rise to the glomerular capillaries and blood will

exit the apparatus via the efferent arteriole

Filtration of fluid from the glomerular capillaries is the first step in urine

formation

Capsule composed of a single layer of squamous epithelium for quick filtering

of filtrate

Trailing from the capsule is aproximal convoluted tubule (PCT) then the loop

of Henle then the (DCT) distal convoluted tubule and finally the collecting

tubule : This is the pathway that urine exits the nephron and eventually leads

to the renal pelvis


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Glomerular Capsule

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Nephron and Associated Blood

Vessels

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Renal Cortex and Renal

Medulla

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Juxtaglomerular Apparatus

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The macula densa &

Juxtaglomerular Apparatus Near its origin, the DCT passes between the

efferent and afferent arterioles by touching them

At this point, the epithelial cells of the DCT aretall and tight- these comprise the macula densa

Means next to the glomerulus

Composed of large vascular smooth muscle cells Together with the macula densa, this apparatus

helps regulate the secretion ofrenin


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Types of Nephrons

cortical nephrons

80% of nephrons

juxtamedullary nephrons

regulate water balance

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Blood Supply of Nephron

The capillary loop of the

vasa recta is closely

associated with the

nephron loop of the

juxtamedullary

nephron

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Summary of Blood Flow

Through Kidney and Nephron

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Urine Formation

Glomerular Filtration

substances move from blood to glomerular capsule

Tubular Reabsorption

substances move from renal tubules into blood ofperitubular capillaries

glucose, water, urea, proteins, creatine

amino, lactic, citric, and uric acids

phosphate, sulfate, calcium, potassium, and sodium ions

Tubular Secretion

substances move from blood of peritubular capillaries into renal

tubules

drugs and ions

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Glomerular Filtration

Glomerular filtrate passes through the fenestrae of

the capillary endothelium

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Glomerular Filtration Rate

Net Filtration Pressure = force favoring filtrationforces opposing filtration

(glomerular capillary ( capsular hydrostatic pressure

hydrostatic pressure) and glomerular capillary

osmotic pressure )

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Tubular Reabsorption

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Effect of ADH on

Renal Tubules without ADH, DCT and collecting duct are impermeable to water

with ADH, DCT and collecting duct become permeable to water

with ADH, water is reabsorbed by osmosis into hypertonic medullary

interstitial fluid

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Urea and Uric Acid Excretion

Urea

product of amino acid

catabolism plasma concentration

reflects the amount or

protein in diet

enters renal tubules

through glomerularfiltration

50% reabsorbed

rest is excreted

Uric Acid

product of nucleic acid

metabolism enters renal tubules

through glomerular

filtration

100% reabsorbed

10% secreted and

excreted

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Elimination of Urine

nephrons

collecting ducts renal papillae

minor and major calyces

renal pelvis

ureters

urinary bladder

urethra

outside world

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Ureters

25 cm long

extend downward posterior

to the parietal peritoneum parallel to vertebral

column

in pelvic cavity, join

urinary bladder wall of ureter

mucous coat

muscular coat

fibrous coat20-31


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Location of Male and Female

Urinary Bladders

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Urinary Bladder

Longitudinal section and posterior view of

male urinary bladder

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Cross Section of Urethra

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Male and Female Urethras

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Micturition

bladder distends and stretch receptors stimulated

micturition center activated in sacral portion of spinal cord

parasympathetic nerve impulses cause detrusor muscle tocontract

need to urinate is sensed

voluntary contraction of external urethral sphincter

prevents urination

when decision is made to urinate, external urethral sphincter

relaxes, detrusor muscle contracts, and urine is expelled

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Clinical Application

Glomerulonephritis

common inflammation of glomeruli

may be acute or chronic acute glomerulonephritis usually occurs as an immune reaction

to a Streptococcus infection antigen-antibody complexes deposited in glomeruli and cause

inflammation

most patients recover from acute glomerulonephritis

chronic glomerulonephritis is a progressive disease and often

involves diseases other than that caused by Streptococcus sp. renal failure may result from chronic glomerulonephritis

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Crescenteric Glomerulonephritis

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HPA Urinary System 2013 Ppt

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