Student Renal Presentation 2012

8/13/2019 Student Renal Presentation 2012

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HAP Renal, 20121

The Renal System

Learning Outcomes

1. Identify the component parts of the renal system.2. Describe the gross anatomy of the kidney and the anatomy

of a nephron.3. Explain the mechanisms that underpin the formation of

urine; filtration, selective reabsorption, and secretion.

4. Discuss the physical characteristics and normalconstituents of urine in relation to urinalysis

5. Describe the structure and functions of the ureters,bladder and urethra and describe the mechanics andcontrol of micturition.

6. Briefly consider how renal function changes across thelifespan in healthy individuals


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Anatomy and Physiology of theRenal System

Macroscopic Structure

Kidneys

Ureters Urinary Bladder Urethra

Kidneysform urine, the rest of system concernedwith eliminating it

Complete labeling exercise of urinary system(handouts to be given in class)


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Kidneys

2 kidney bean shaped organs in upper abdomen -

contain NEPHRONSinvolved in urine formation Blood supplied by RENAL ARTERY and drained by

RENAL VEIN

Covered and protected by a fibrous capsule

Has 3 distinct regions (REFER TO YOUR BOOK);

RENAL CORTEX (glomeruli, Bowmans capsule andconvoluted tubules

RENAL MEDULLA (loops of Henle and collectingducts

RENAL PELVIS central area where urinecollects

Divided into 8 lobes


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HAP Renal, 20125http://www.neok12.com/diagram/Urinary-System-01.htm


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Renal System (contd)

URETERS2 muscular tubes which transport

urine from kidney to bladder, fluid moved viasmooth muscle contraction or PERISTALSIS

BLADDERa contractable bag in anterior part

of pelvic cavity which collects urine. Made up oftransitional epithelium and can expand when full holds up to 800mls

URETHRA muscular tube which leaves thebladder at lowest point, moves urine from bladderto outside of body, length varies in male andfemale


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Kidney Functions

1) Elimination of waste products

2) Control of fluids, electrolytes and acid-basebalance

3) Regulation of renal and systemic BP (renin-angiotensin system)

4) Stimulate RBC formation (erythropoiesis)5) Activation of Vitamin D


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Microscopic Structure

NEPHRONSare the functional unit of the kidney 2 million nephrons in each kidney and called the

RENAL TUBULES Responsible for;

Urine production Fluid balance Electrolyte balance Acid base balance (homeostasis of blood pH)

The tubule carries out the above by way of 3distinct processes called filtration,reabsorptionand secretion which occur at specific sites alongthe tubule (nephron)


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Processes of Urine Formation in Nephron

(1) Filtration or simple filtrationBlood in glomerular capillaries is filtered through vessel

walls(like a sieve) to form a filtrate consisting of waterand small molecules; electrolytes, amino acids, glucosehormones, creatinine, urea, uric acid and drugs

(2) Reabsorption

Selected substances from the filtrate are reabsorbedback into blood via peritubular capillaries, moves eitherpassively (H2O) or by active transport (Na, Cl and K),and hormones can affect this eg. ADH, aldosterone,renin, & angiotensin ll)

(3) SecretionSome substances may not be cleared from blood by

filtration so active transport moves these moleculesinto filtrate at the DCT & collecting ducts, Eg. Uric

acid, creatinine, H+, K+, ammonia, penicillin etc.


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Anatomy and Function of Nephron (1)

Glomerulusa network of capillaires sitting withina cup-like structure or capsule, and involved inprocess of filtration

Glomerular Capsule or Bowmans capsule adouble walled epithelium cup that surrounds theglomerulus, its specialised cells (with gaps) help infiltration of blood and formation of filtrate

Proximal Convoluted Tubule (PCT)first part ofnephron tubule after filtration and site of mostreabsorptionand some secretion


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BowmanssCapsule or

RenalCorpuscle

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Anatomy and Function of Nephron (2)

Loop of Henle ascending and descending limbs oftubule, concerned with reabsorptiononly

Distal Convoluted Tubule (DCT) site of Na+(sodium) reabsorptionand some secretion

Collecting Duct several DCTs empy urine into asingle collecting duct, lots of collecting ducts then

converge and empty into the calyces of the renalpyramids (look at diagram), and on into the renalpelvis and ureters Reabsorptionand Secretionoccurs here


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A Nephron in Action

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Movement of Urine from Collecting

Ducts The urine moves from the collecting ducts to the

bladder via the following pathway;

1. Collecting duct

2. Papilla of medulla

3. Minor or lesser _____________

4. Major or greater __________

5. Renal _____________

6. U_____________

7. Bladder


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Micturition Pathway

Basically: simple reflex (easily noted in infants)

Sensory pathways When 250ml urine stretch receptors are

stimulated excite sensory parasympathetic fibres Information relayed to the sacral area of the spine

for integrationMotor pathway AT THE SAME TIME Parasympathetic motor neurones are excitedcontract the detrusor muscle bladder pressure

internal sphincter opens Motor neurons supplying the external sphincter via

the pudendal nerve are inhibitedso externalsphincter opens & urine flows out (gravity helps too!)


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Control of Micturition

We learn to adapt this simple reflex Bladder wall: sensory fibres convey how full the

bladder is via the spine higher centres of thebrain, the thalamus & cerebral cortex (notestablished until 2yrs old)

An awareness of level of urgency and you can overridethe micturition reflex by: Inhibiting the parasympathetic motor nerve fibres

to the bladder Reinforcing contraction of the external sphincter

As urine volume increases stretch receptor &

nerve activity

sensation of pressure moreuncomfortable When convenient, brain centres remove inhibition and

permit micturition under conscious control After micturition < 10ml urine remains in bladder and

the cycle begins again


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Control of bladder emptying

The neck of the bladder (between bladder & urethra)

has 2 muscular sphincters Are contracted due to CNS stimulation but relaxed in

micturition Internal sphincters

Has involuntarymuscle fibres Normally is contracted Involuntary control

External sphincter Formed of a circular band of voluntarymuscle

This muscle is supplied by the pudendal nerve Normally is contracted Under voluntary control


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Renal Function During the Lifespan of

Healthy Individuals1. In your table group, use your books or computers to

identify a number of changes which occur in the urinarysystem of males and females during the normal lifespan

2. Discuss the effect these changes have on renal/urinaryfunction

3. Feedback to the group

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URINE COMPOSITION

Refer to your urinalysis handout and apply in your DPS

session at the end of the week.

Student Renal Presentation 2012

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