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Aids homeostasis by removing cellular wastes and foreign compounds, and maintains salt and water balance of plasma

Urinary system Kidney anatomyRenalcortex

Renalmedulla

Renalpelvis

UreterMedulla

Cortex

Nephrons

Each kidney has about one million nephrons

Afferent arteriole brings blood to glomerulus and then forms efferent arteriole.

Efferent arteriole branches to peritubular capillaries

Let’s make the filtrate...

Blood is filtered at the glomerulus. Water and solutes leave the blood and enter Bowman’s capsule.

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Glomerulus physiologyBowman’s capsule contains podocytes that encircle the glomerulus.

Normally blood cells and plasma proteins are not filtered

Glomerular filtration

Glomerular filtration is similar to ultrafiltration of capillaries

20% of plasma becomes filtrate

Capillaryblood pressure

Osmoticpressure

Hydrostaticpressure

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30 15

Glomerular filtration rate (GFR) determined by:Net filtration pressure and glomerulus permeability

Adjusting GFR

Blood pressure

Radius of afferent arteriole

Decreasing GFR helps retain fluid and salts

Filtrate is adjusted along the nephronDistaltubule

Bowman’scapsule

Proximaltubule

Loop ofHenle

Cortex region

Medulla region

Juxtaglomerular apparatus - helps inadjustments to filtration rate

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180 liters per day are filtered, most is reabsorbed

Reabsorption: filtered substances leave the nephron and enter peritubular capillaries

Secretion: some substances from the peritubular capillaries enter the nephron

Tubular reabsorption and secretion

Everything in the nephron that does not get reabsorbed into the blood leaves as

….urine!!!

So what is urine, then?Reabsorption physiology

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Reabsorption of Na+

(the key to it all…)

Na+ reabsorption (RA) drives the movement of many other substances in the tubule

Water will “follow” Na+

movement

Na+ reabsorption

Page 533Lumen

Proximal tubular cell

Peritubular capillary

Interstitial fluid

Waterchannel

Osmosis

Osmosis

Hydrostaticpressure

When ECF volume is low, need to Na+ RA

Na+ RA at distal and collection tubules with aldosterone. More Na+K+ pumps and Na+

channels are made

Renin is the trigger for eventual release of aldosterone, along a chain of events (renin-angiotensin-aldosterone system or RAAS)

Control of sodium RA

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Jux.App. monitors NaCl and ECF levels

Juxtaglomerular

apparatus

Distal

tubule

Bowman’scapsule

Podocyte

Glomerular

capillaries

Juxtaglomerular

apparatus

Efferent

arteriole

Distal

tubule

Afferent

arteriole

Granular cells

Glomerular

capillaries

Bowman’s

capsule

Hypertension can be due to increased renin leading to more plasma and thus high blood pressure Glucose and AA’s are

cotransported w/Na+ via carriers

Actively RA substances have a “tubular maximum” (when all carriers are used)

Glucose and amino acid reabsorption

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80% of water reabsorption occurs before distal tub. by following Na+

Glucose, amino acids are reabsorbed via cotransporters

If plasma levels get too high, renal threshold is reached (AAs or glucose leave in urine)

Na+ movement allows passive RA of substances.Our old friend, cotransport

H+ and K+, and organic anions are secreted to tubule

K+ secretion is driven by the Na+K+ pump

Tubular secretion

Our body tissues and filtrate are 300 mosm (osmolarity)

We can make urine as dilute as 100 or concentrated as 1200 mosm

Na+ gradient in renal medulla allows for control of urine osmolarity for water balance

Adjusting the concentration of urine

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Loop of Henle functions to set up high osmolarity along the collecting tubule (duct)

Cortex

Medulla

Long loop

of Henle

Collecting

Tubule or Duct

Distal

tubule

Changing the permeability to H20 along the collecting duct controls H2O RA

Vasopressin hormone controls permeability at distal and collecting tubules

Collecting tubule (duct)

65 % of H20 RA is obligatory in the proximal tubule, 15% at Loop of Henle.

20% determined by vasopressin

Collecting duct permeability determines final amount of H2O RA Filtrate has concentration

of 100 mosm/liter

Collecting

tubule

Medulla

Cortex

Concentration of

urine may be up

to 1,200

= permeability to H2O

increased by vasopressin

= passive diffusion of

H2O

= active transport of NaCl

= portions of tubule

impermeable to H2O

*

Needing water

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Collecting

tubule

Medulla

Cortex

Concentration of

urine may be as low

as 100

= permeability to H2O

increased by vasopressin

= passive diffusion of

H2O

= active transport of NaCl

= portions of tubule

impermeable to H2O

*

Too much waterFiltrate has concentration

of 100 mosm/liter

Alcohol inhibits vasopressin

It can also temporarily reduce blood glucose (via liver effects)

Why increased urination from alcohol?

Kidney stones – caused when hard deposits form in the kidney (usually calcium, sometimes uric acid). They can enter the ureter and cause extreme pain.

Urinary tract infection – 2nd most common type of infection. Bacteria introduced to urethra multiply and travel to bladder (cystitis) or further.

Medical problems

End of exam 4 material

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Things I’m assuming you know:

Know layers found throughout alimentary canal (mucosa, submucosa, muscular layers) and the term lumen

Accessory structures (pancreas, liver, salivary glands, other exocrine glands) are a part of the digestive system

What goes on during digestion…

Motility - propulsion and mixing

Secretion of digestive enzymes, bile, mucus, water

Chemical digestion

Absorption

Signaling

Network of nerve fibers that controls digestive activity in gut. “Your 2nd brain”

Intrinsic nerve plexus

Physical digestionMastication - mixes food with saliva

Saliva -

amylase - digests starch

mucus

lysozyme

Down the chute…oral cavity

Tooth decay frombacterial activity on food debris

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Pressure and gustation promotes autonomic impulses to salivary glands

PNS and SNS signals both influence salivary glands

Making saliva...

Bolus touches receptors in the pharynx to stimulate swallowing

Peristaltic contractions push food through the esophagus.

Distention will cause a second wave and saliva release

Storage, physical and chemical digestion

HCl

Mixing in the antrum

Bolus Chyme

Into the ....stomach

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Duodenum

Pyloric sphincter

Movementof chyme

Peristalticcontraction

Gastric emptying

Peristalticcontraction

Mucosaof stomach

Gastricpits

Mucosa

Submucosa

Stomach mucosa

Gastricpit

Gastricglands

Mucosa cells

Chief cells (Pepsinogen)

Parietal cells (HCl)

pH as low as 2

Gastric juices!

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autocatalysis

Digestion

Protein

Peptide fragments

HCI

Pepsinogen Pepsin

Cephalic (“head”) phase - stimuli from the head stimulate chief and parietal cells via intrinsic plexus, gastrin released

Controlling gastric juices..

Gastric phase – proteins, distension at stomach also stimulate gastric secretions via intrinsic plexus

Low protein, low pH is inhibitory, decreasing flow of gastric juices

Controlling gastric juices.. Stomach lining is protected from

gastric secretions by mucus. H+ cannot enter cells

Cells are continually replaced

Protecting the stomach from itself…

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Peptic ulcer - stomach wall injured by acid and enzymes

Injured tissue releases histamine, which stimulates acid production (…not good)

Stomach lining problemsEmptying controlled by duodenum and stomach

Chyme volume promotes emptying

Acid and fats in duodenum prevent gastric emptying

Leaving the stomach…

Duodenum

Pyloric sphincter

Gastroesophageal

sphincter

Movement

of chyme

Peristaltic

contraction

Gastric emptying

Leaving the stomach...

Islets of Langerhans

Pancreas

Cells secrete digestive enzymes

Duodenum

Stomach

Cellssecrete alkaline solution

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An endocrine and exocrine gland

Enzymes: protease, amylase, lipase

Pancreas