The excretory system
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The Excretory System. Excretion- removal of waste produced during body functions. Occurs through: Intestine - digestive wastes, salts Skin (sweat glands)- water, electrolytes Lungs - carbon dioxide, water Kidneys - toxins, water, N cmpds, electrolytes. Urinary System Functions.

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The Excretory System

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The Excretory System


Excretion- removal of waste produced during body functions

Occurs through:

  • Intestine- digestive wastes, salts

  • Skin (sweat glands)- water, electrolytes

  • Lungs- carbon dioxide, water

  • Kidneys- toxins, water, N cmpds, electrolytes


Urinary System Functions

  • maintain water concentration in blood

  • maintain concentration of ions like Na & K

  • form urine

  • influence rate of secretion of hormones like ADH

  • alter pH (acid- base balance)

    Why bother with all of these?


Basic Anatomy of the Urinary System


Gross Anatomy- KIDNEY

  • lie in retroperitoneal position

  • Fat cushion holds it in position

  • medial surface with concave hilus

Not that type….


Gross Anatomy- KIDNEY

  • Cortex- outer and lighter

  • Medulla- inner and darker

1. Cortex region of kidney

2. Medulla region of kidney


Gross Anatomy- KIDNEY

6. Most of the medulla is made up of RENAL PYRAMIDS with a base facing outward and papilla facing the hilus


Gross Anatomy- KIDNEY

7. Cortical tissue dips into the medulla between the pyramids, forming RENAL COLUMNS


Gross Anatomy- KIDNEY

8. Each renal papilla juts into a cup-like CALYX

  • Urine leaving the renal papilla collects here before leaving the body


Gross Anatomy- KIDNEY

9. The calyces join to form the renal pelvis. It narrows as it exits the hilum to become the ureter.


10. BLOOD VESSELS

Renal artery brings ¼ of all blood to kidney/min.

Branches into

Interlobar arteries- extend toward the cortex

Changes names

Arcuate arteries- base of pyramids

Changes names

Interlobular arteries- afferent arterioles that branch into the glomerulus where blood is filtered


10. BLOOD VESSELS (continued)

Efferent arterioles

Peritubular capillaries (vasa recta) Interlobular veinArcuate veinInterlobar veinrenal vein

Blood flows into

But, I am not going to test you on this stuff!


Macroscopic Kidneys

A. Capsule & hilus

B. Renal sinus

1. renal pelvis

2. major calyces

3. minor calyces

C. Renal medulla

1. renal pyramids

a. papilla

2. Renal column

D. Renal cortex


B. Gross Anatomy- URETER

  • 28 cm long

  • Allows urine to travel from kidney to urinary bladder

  • 3 layers of tissue:

    • Mucous lining

    • Smooth muscle middle

    • DWF outer layer


C. URINARY BLADDER

  • behind symphysis pubis

  • mostly smooth muscle aka detrusor muscle lined with transitional epithelium

  • 3 openings: 2 from ureters and one into the urethra

  • Has valve to prevent backflow into kidney

  • Functions

    • urine reservoir

    • aided by urethra, expels urine from body


Male Urethra

Female Urethra


Gross Anatomy- URETHRA

  • 3 cm in females; 20 cm in males

  • Male urethra (URINE) passes through prostate gland where it is joined by 2 ejacuatory ducts (SEMEN) then travels through penis and ends at the urinary meatus at the tip of the penis.

  • In females, completely separate from vagina


4. Micturition- urination

  • Voluntary relaxation of external sphincter muscle of bladder

  • Detrusor muscle contracts

  • Parasympathetic nerve control

  • Incontinence


Microscopic Structure of the NEPHRON

  • Filtering unit of kidney

  • Process blood plasma

  • Form urine

  • 1.25 million per kidney

  • Looks like a funnel with a

    long, winding stem


Components

1. renal corpuscle

2. PCT

3. loop of Henle

4. DCT

5. Collecting tubule & duct

NEPHRON


The Nephron

  • The nephron is the functional unit of the kidney, responsible for the actual purification and filtration of the blood.

  • About one million nephrons are in the cortex of each kidney.


The NEPHRON

RENAL CORPUSCLE- in the cortex

  • Bowman’s capsule

    • Cup-shaped mouth of nephron

  • Glomerulus

    • capillaries in BC

    • Pores (fenestrations)

    • Basement membrane


The Glomerulus


Microscopic Structure of the NEPHRON

PROXIMAL TUBULE- in cortex

  • Closest to BC (“proximal”)

  • Aka PCT (proximal convoluted tubule)

  • Brush border (microvilli) face lumen- increase surface area


cortex

medulla

The NEPHRON

LOOP OF HENLE (LOH)

  • Renal tubule beyond the PCT

    • Descending limb (thin)

    • Sharp turn

    • Ascending limb (thick)

    • Dips into medulla


THE NEPHRON

DISTAL TUBULE

  • Aka DCT (distal convoluted tubule)

  • Beyond LOH (“distal”)

  • Juxtaglomerular apparatus


THE NEPHRON

COLLECTING DUCT

  • Straight tubule joined by distal tubules of several nephrons

  • Fuse to form papillary ducts which deliver urine to the calyces


Overview of KIDNEY FUNCTION

1. FILTRATION

  • Occurs in glomerulus

  • Dependent on Glomerular Filtration Rate (GFR)

  • Filter water and solutes from blood into renal tubule

    • Glucose

    • Amino acids

    • Nitrogen wastes


KIDNEY FUNCTION-Filtration

  • FILTRATION

    • What’s left in the blood?

      • Blood cells

      • Most plasma proteins

    • What causes it?

      • Pressure gradient (high to low)

      • Related to blood pressure


Filtration

GFR is directly dependent on blood pressure.a. If GFR (BP) is too high, filtrate flows too fast and substances are NOT reabsorbed

urine flow increases water is lost blood volume drops  blood pressure drops.

b. If GFR (BP) is too low, filtrate flows too slow and substancesare retained too much

urine flow decreases  water is preserved  blood volume increases  blood pressure increases.


Overview of KIDNEY FUNCTION

2. REABSORPTION

  • Occurs in mostly in PCT and little in LOH, DCT, CD

  • Put good things in the renal tubule back into the blood (peritubular capillaries)

    • Water

    • Electrolytes

    • Nutrients


Overview of KIDNEY FUNCTION

  • REABSORPTION

    • Healthy kidneys reabsorb

      • Glucose (if not…)

      • Amino acids

      • Sodium

      • Water


Overview of KIDNEY FUNCTION

  • REABSORPTION

    • Substances that are NOT reabsorbed fully

      • Things that lack carriers

      • Things that are not lipid soluble

      • Things that are too large

      • Examples: urea, creatinine, uric acid


Overview of KIDNEY FUNCTION

  • REABSORPTION

    • ADH causes the distal and collecting tubules to become more permeable to water

    • This allows hypertonic urine to be formed


Overview of KIDNEY FUNCTION

  • SECRETION

    • PCT mostly

    • Reabsorption in reverse

    • Movement of small molecules out of the peritubular blood and into the tubule for excretion

      • Including K, H, urea, ammonia

      • Dispose certain drugs

      • Helps control blood pH


Review Questions

  • Do you know the names of the structures?

  • What is GFR? What regulates it?

  • Why is reabsorption important?

  • Where is the only place glucose is reabsorbed?

  • Where does ADH act? What does it do?


Making Urine

  • Choose your water solution (Normal or Dehydrated)

  • Fill the cup 2/3 of the way with that solution

  • Add ½ dropper of Urea + vitamins

  • Add ½ dropper of acid

  • Check pH with pH paper

  • If you desire, pimp your urine with 1 dropper of the following:


Answer the following questions on a piece of paper and turn it in?

  • Did you drink the urine?

  • What type did you make?

  • How did it taste?

  • Did it taste like you expected?

  • If you did not drink it, why not? (please provide at least three reasons)


URINE COMPOSITION

  • Water- 95%

  • Other substances- 5%

    • Nitrogen wastes

    • Electrolytes

    • Toxins

    • Pigments

    • Hormones

    • Abnormal stuff like blood, glucose, casts, calculi


URINE COMPOSITION

  • Characteristics

    • Color

    • Compounds

    • Slight odor

    • 4.6-8.0 pH (fresh is acidic)

    • 1.001- 1.035 specific gravity


FLUID, ELECTROLYTE, and ACID-BASE BALANCE

  • FLUID

    • Water accounts for 50-60% total weight (why less in obese people?)

      • 37% of this is ECF

      • 63% of this is ICF


FLUID, ELECTROLYTE, and ACID-BASE BALANCE

  • Mechanisms to maintain fluid balance

    • Volumes of ICP, ECF, plasma, and total volume of water relatively constant

    • Adjust output (urine volume) to intake

    • Adjust fluid intake (liquids we drink, water in food we eat, water formed by catabolism)


Anatomy of Micturition & Incontinence

  • Detrusor muscle with an External and Internal sphincter

  • Normal capacity 300-600cc

  • First urge to void 150-300cc

  • CNS control

    • Pons - facilitates

    • Cerebral cortex - inhibits

  • Harmonal effects - estrogen


Bladder Pressure-Volume Relationship: Or how to hold it


Treatment Options

  • Reduce amount and timing of fluid intake

  • Avoid bladder stimulants (caffeine)

  • Use diuretics judiciously (not before bed)

  • Reduce physical barriers to toilet (use bedside commode)

1


Pessaries


Predisposing conditions to UTI

  • Female

  • Short urethra, proximity to anus, termination beneath labia

  • Sexual activity

  • Pregnancy

    • 2-3% have UTI in preg, 20-30% with asx bacteriuria

  • decreased ureteral peristalsis, temp. incomp ofvesicoureteral valves


Urethritis

  • 􀂃 Acute dysuria, frequency

  • 􀂃 Often need to suspect sexually

  • transmitted pathogens esp. if sx more than 2 days, no hematuria, no suprapubic

  • pain, new sexual partner, cervicitis


Cystitis

  • Sx: frequency, dysuria, urgency, suprapubic pain

  • Cloudy, malodorous urine (nonspec.)

  • Leukocyte esterase positive = pyuria

  • Nitrite positive (but not always)

  • WBC (2-5 with sx) and bacteria on urine microscopy


Nephrolithiasis: kidney stones

  • Supersat. of urine by stone forming constituents

  • Freq. stone types: Calcium (most common), struvite, oxalate, uric acid

  • Risk factors: metabolic disturbances, previous UTI, gout, genetic

  • Incidence = 2-3%

  • Hematuria (rarely dangerous by itself)

  • Dangerous combo = obstruction + infection


Addison’s Disease

Addison's disease occurs when the adrenal glands do not produce enough of the hormone cortisol and, in some cases, the hormone aldosterone


Cystocele

the wall between a woman’s bladder and her vagina weakens and allows the bladder to droop into the vagina

  • mild—grade 1—when the bladder droops only a short way into the vagina.

  • severe—grade 2—the bladder sinks far enough to reach the opening of the vagina.

  • advanced—grade 3—cystocele occurs when the bladder bulges out through the opening of the vagina.


Nocturnal enuresis

  • Hormonal problems.

  • Bladder problems.

  • Genetics.

  • Sleep problems.

  • Medical conditions

  • Psychological problems.


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