Urinary System AP

Functions of the urinary system

Removal of liquid waste from body fluids

Discharge of waste products

Volume and solute concentration of blood

Covers outer surface of entire organ

Layer of fat surrounding renal capsule

Anchors kidney to surrounding structures

Point of entry for renal artery and renal nerves

Point of exit for renal vein and ureter

Internal anatomy of kidney:

Superficial portion of kidney

Internal anatomy of kidney:

Made up of renal pyramids and columns

6-18 triangular structures in renal medulla

• Apex projects into minor calyces

Tissue separating adjacent renal pyramids

• Extend from cortex into medulla

Ducts that discharge urine into minor calyx

• Cup-shaped drain for urine

Formed by 4 or 5 minor calyces

Large funnel made of 2 or 3 major calyces

• connected to ureter, which drains kidney

What percentage of total cardiac output do the kidneys receive?

Kidney receives blood through what?

What do renal arteries divide into

What do segmental arteries split into?

• These radiate between renal pyramids

  • Supply blood to arcuate arteries between cortex and medulla

What do interlobar arteries split off into?

These branch off from arcuate arteries, delivering blood to cortex

• 90% of blood entering the kidneys is in the cortex

Branch off supplying nephrons with blood

After blood exits the nephrons, where does it enter?

Structural and functional unit within the kidney

• Tubular structures in cortex of each renal lobe where urine production begins

• Each kidney contains over 1 million of these

• Consists of renal corpuscle and renal tubule

Structure consisting of:

• Glomerular capsule

  • Capsular Space

• Glomerulus

Structure consisting of:

• Proximal convoluted tubule (PCT)

• Nephron loop

  • U-shaped tube

  • Extends partially into medulla

• Distal convoluted tubule (DCT)

85% of all nephrons

• Located mostly within cortex of kidney

• Nephron loop is relatively short

• Efferent arteriole delivers blood to peritubular capillaries

  • Which drain into venules into the renal veins

15% of nephrons

• Nephron loops extend deep into medulla

• Peritubular capillaries connect to vasa recta

  • Plays a role in reabsorption and concentration gradients

Forms outer wall of renal corpuscle

• Capsular epithelium

  • Continuous with visceral epithelium

• Encapsulates glomerulus

  • Separated by capsular space

• Connected to proximal convoluted tubules

Knot of over 50 intertwining capillaries

• Blood from afferent arteriole

• Blood leaves by efferent arteriole

The epithelium of glomerulus consists of large cells called:

Exists between adjacent pedicles

• Materials must be small enough to pass between these

What type of process is glomerular filtration:

• Blood pressure forces water and small solutes into capsular space

First segment of renal tubule

• Formed of simple cuboidal cells

  • Microvilli on apical surfaces (assists in reabsorption)

• Absorbs nutrients, ions, water

  • Release them into peritubular fluid

Interstitial fluid around renal tubules

the portion of a nephron that leads from the proximal convoluted tubule to the distal convoluted tubule

• In between descending limb and ascending limb

This portion of the nephron flows toward renal pelvis

• Permeable to water

  • Water movement helps concentrate tubular fluid

This portion of the nephron flows toward renal cortex

• Pumps sodium and chloride ions out of tubular fluid

  • Creates high solute concentrations in peritubular fluid

Final segment of the renal tubule passes between afferent and efferent arterioles

• Epithelial cells lack microvilli

• Has three processes

  • Active secretion of ions, acids, drugs, and toxins

  • Selective reabsorption of sodium and calcium ions from tubular fluid

  • Selective reabsorption of water

    • Concentrates tubular fluid

An endocrine structure that monitors blood volume

• Secretes: Hormone erythropoeitin and enzyme renin

• Formed by:

  • Macula densa cells of DCT, near renal corpuscle

DCT opens into the collecting ducts

• Several collecting ducts:

  • Converge into a larger papillary duct

    • Which empties into a minor calyx

• Transports tubular fluid from nephron to renal pelvis

• Adjusts fluid composition and pH

  • Determines final solute concentration and volume of urine

Glomerular filtration involves a passage across a __________

• There are three components of this membrane

  • Capillary endothelium

  • Dense layer

  • Filtration slits

• Produces filtrate similar to blood plasma

Component of filtration membrane:

• Fenestrated capillaries

  • Prevents passage of blood cells, but allow diffusion

Component of filtration membrane:

• Allows diffusion of small proteins, nutrients, and ions

Component of filtration membrane:

• Finest filters

• Prevent passage of most small plasma proteins

Glomerular filtration is governed by the balance between:

Pushes water and solutes out of blood through filtration membrane

• Efferent arterioles have a smaller diameter than afferent

  • Produces resistance inside and pressure inside glomerular capillaries

  • Averages 50mm Hg

Opposes glomerular hydrostatic pressure

• Pushes water and solutes from filtrate back into the blood

  • Produces from left over filtrate within the glomerular

Difference between glomerular and capsular hydrostatic pressures (35mm Hg)

Pressure resulting from the presence of suspended proteins

• Draw water out of filtrate and into blood

  • Opposing filtration

• Averages 25 mm Hg

All the pressures moving water and dissolved materials

• Hydrostatic and colloid osmotic pressure across glomerular capillaries

Amount of filtrate kidneys produce each minute

• Averages 125 mL/min

• 10% of fluid delivered to kidneys leaves bloodstream and enters capsular spaces

• Glomeruli generate about 180 liters of filtrate per day

Regulation of glomerular filtration:

At the local level

• Maintains glomerular filtration rate despite changes in blood pressure or flow

  • Reduced blood flow or glomerular blood pressure triggers:

    • Dilation of afferent arteriole and glomerular capillaries

  • Rise in renal blood pressure

    • Stretches walls of afferent arterioles

    • Causing arterioles to constrict

      • Decreases glomerular blood flow

Regulation of glomerular filtration:

Sympathetic nervous system

• Mostly consists of sympathetic fibers

  • Activation constricts afferent arterioles

    • Decreases glomerular filtration rate

      • Slows filtrate production

    • May be opposed by autoregulation at local level

Released by the heart due to increased blood volume or pressure

• Trigger dilation of afferent arterioles and constriction of efferent arterioles

  • Elevate glomerular pressures and increase GFR

• Oppose secretion of aldosterone

  • Decrease sodium retention

Main mechanism for increasing blood pressure

• Increases blood volume and pressure thereby increasing GFR

Vasoconstricts the arterioles and precapillary sphincters

• Elevating glomerular pressures and filtration rates

Stimulates secretion of Aldosterone by adrenal cortex

• Accelerates sodium reabsorption

Stimulates thirst

Releases ADH

Increases sympathetic motor tone

These are the functions of what structure:

• Reabsorption of organic nutrients

  • 99% reabsorbed via cotransport and facilitated diffusion

• Active reabsorption of ions

• Reabsorption of water

• Passive reabsorption of ions

• Secretion

Exchange between parallel segments of nephron loop

• Refers to exchange between tubular fluids moving in opposite directions

  • Descending limb flows toward renal pelvis

  • Ascending limb flows toward cortex

• Effect of exchange increases as movement of fluid continues

What reabsorbs the ½ of water and 2/3 of sodium and chloride ions remaining through the process of countercurrent multiplication and exchange

Which limb of the nephron loop is permeable to water and mostly impermeable to solutes

Which limb of the nephron loop is mostly impermeable to water and solutes

• contains active transport mechanisms for sodium and chloride ions

What percent of initial filtrate volume reaches the DCT

What actively transports sodium and chloride ions out of tubular fluid at the distal convoluted tubule

• distal portions contain ion pumps

  • Reabsorb tubular sodium ions in exchange for potassium ion

This is produced by the adrenal cortex, which reduces sodium list in urine

• controls ion pumps and channels for sodium

Circulating levels of these hormones regulate calcium ion reabsorption at the DCT

This occurs when osmotic concentration of peritubular fluid exceeds that of tubular fluid

Water movement that cannot be prevented

• usually recovers 85% of filtrate produced

Controls volume of water reabsorbed along DCT and collecting system

• 15% of filtrate volume

• segments are relatively impermeable to water

  • except in presence of ADH

Hormone that causes special aquaporins to appear in apical cell membranes

• increases rate of osmotic water movement

Higher levels increase:

• Number of water channels and water permeability of DCT and collecting system

Without this water is not reabsorbed

Returns solutes and water reabsorbed in medulla to circulation without disrupting the concentration gradient

• Solute Concentration increases as blood descends into medulla

  • Involves solute absorption and water loss

• Blood flowing toward cortex:

  • Gradually decreases with solute concentration of peritubular fluid

    • Involves solute diffusion and osmosis

Solutes absorbed in descending portion don’t diffuse out in ascending portion

• More water moves into ascending portion than is moved out of descending portion

Carries water and solutes out of medulla

• Balances solute reabsorption and osmosis in medulla

Volume of plasma the kidneys removes a particular substance from in a minute

• Used to estimate glomerular filtration rate

• C = UV/P

What indicates infection in urine

What is the composition of normal urine

What gives urine a yellow color (pigment)

What is the pH range of urine

Pair of muscular tubes

• Begin at renal pelvis

• attached to posterior abdominal wall

• penetrate posterior wall of the urinary bladder

Slit-like rather than rounded

• helps prevent backflow when urinary bladder contracts

What are the 3 layers of ureter

Layer of the ureter:

Transitional epithelium and lamina propria

Layer of the ureter:

Longitudinal and circular bands of smooth muscle

• peristaltic contractions force urine toward urinary bladder every 30 seconds

Layer of the ureter:

Outer connective tissue layer

Continuous with fibrous renal capsule of the kidney

Hollow, muscular organ

• temporary reservoir for urine storage

• Full bladder can contain 1 liter of urine

Several of these stabilize and maintain bladder position

Anchor urinary bladder to pelvic and pubic bone

Triangular area formed by:

• Openings of ureters and the entrance to urethra

  • Internal urethral sphincter

• Acts as a funnel

What are the 4 layers of urinary bladder

Thin walled muscular tube that drains the urinary bladder

• extends from urinary bladder to the exterior of the body

Circular band of skeletal muscle

• Voluntary control and acts as a valve

  • Voluntary relaxation permits micturition

From urinary bladder to tip of penis

• Regions of the male urethra

  • Prostatic urethra passes through prostate gland

  • Membranous urethra short segment that leaves pelvic cavity

  • Spongy urethra from pelvic cavity to external urethral orifice

Epithelial mucous glands form tubules that extend into lamina propria

Lamina propria anchor urethra to surrounding structures

Short

Extends from bladder to vestibule between labia

Lamina propria contains extensive network of veins

Complex is surrounded by concentric layers of smooth muscle

What triggers urination reflex

In pelvic nerves:

Stimulate neurons in wall of bladder

• stimulates detrusor muscle contraction

Allows for voluntary relaxation of external urethral sphincter

• somatic muscles

• causes relaxation of internal urethral sphincter

High levels of sodium

Dehydration, excessive intravenous NaCl

• Thirst, confusion, lethargy progressing to coma, neuromuscular issues

Low levels of sodium

Solute loss, water retention

• Neurological dysfunction, decrease in blood volume and pressure

High levels of potassium

Renal failure, aldosterone deficit, severe tissue injury

• Nausea, vomiting, cardiac arrhythmia, skeletal muscle weakness

Low levels of potassium

Inadequate dietary intake, excessive vomiting or diarrhea

• Cardiac arrhytmia, metabolic alkalosis, mental confusion

High levels of calcium

Hyperparathyroidism, renal disease

• Decreased neuromuscular excitability, skeletal muscle weakness, kidney stones

Low levels of calcium

Burn victims, hypoparathyroidism

• Increased neuromuscular excitability, skeletal muscle cramps, convulsions