Function of the kidneys:

• Remove hydrogen ions to control blood pH
• Control blood volume (plasma levels)
  • Kidneys only interact with the plasma portion of the blood.
• Ion concentration in the blood (sodium, calcium, etc.)
• Detoxifies (filters out toxicity in the blood)
• regulate blood volumes with ADH (DIRECTLY regulates water intake)
• regulates blood pressure through water retention and RENIN
• stimulates RBC production
• during extreme starvation, they break down proteins

Structure of the kidneys:

• Towards your back, behind parietal peritoneum (covering)
• Renal artery & renal vein = branch from vena cava & aorta
• Renal/fibrous capsule = thin outer surface surrounding the kidney 
• Renal cortex = outer layer of kidney
• Renal medulla = inner layer of kidney
• Renal pyramids = sections of the renal medulla 
• Renal pelvis = large, funnel-shaped structure in center of the kidney; collects urine from major calyces

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Urinary System:

• 2 kidneys, 2 ureters, bladder, urethra

  

Kidney Blood Flow:

• Blood IN from RENAL ARTERY → Blood OUT from RENAL VEIN

• Urine out from ureter

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pH (of kidneys): 4-7

Kidney failure: Too much CO₂ in blood

• Kidneys and lungs get rid of CO₂ 

Causes of kidney failure: 

• Acidosis (pH below 7.35)
• Alkalosis (pH above 7.45)

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Medulla is HYPERTONIC to cortex

Cortex is HYPERTONIC to medulla

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In pancreas, alpha & beta cells secrete glucagon & insulin

• Acinar cells secrete digestive enzymes

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Macula densa 

• chief cells that secrete renin hormone for sensory & regulatory functions maintaining body fluids, electrolyte homeostasis & blood pressure.

• respond to the sodium concentration in the fluid within the distal tubule.

• detects blood pressure and blood volume

• If GFR (glomerular filtration rate) is low, renin is secreted to make GFR to go up

• Detects changes in osmolarity using chemoreceptors (chemicals) in distal tubule or baroreceptors (pressure) with macula densa cells

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Renin: hormone secreted by macula densa

• Controls blood pressure & maintain potassium & sodium levels
• Released when LOW BLOOD PRESSURE
• Causes ADH/vasopressin (antidiuretic): increases water reabsorption in kidney by inserting aquaporin channels at collecting ducts
• Produces ALDOSTERONE: angiotensin II → stimulates release of aldosterone (INDIRECTLY regulates water intake)

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Nephron: filtering units in the kidney; located between the cortex & medulla

Glomerulus: beginning of nephron where FILTRATION OCCURS

• how much PLASMA = how much URINE
• AFFERENT arteriole/vessels: carry blood TOWARDS glomerulus; branch of renal
• EFFERENT arteriole/vessels: take blood containing nitrogenous waste AWAY from glomerulus

Bowman’s capsule: contains glomerulus; filters blood from the glomerular capillaries

Proximal tubule: BEGINNING of nephron, reabsorbs glucose

Loop of Henle: U-shaped portion of tubule in medulla that recovers water & NaCl from urine from filtrate

• Ascending Limb/loop: drains urine into distal tubule; maintains low intracellular concentration of sodium & promotes passive entry of sodium at the luminal membrane. Becomes impermeable to water and the cells actively reabsorbs solutes from the luminal fluid so that water is not reabsorbed and ions are ready to be reabsorbed.
• Descending Limb/loop:

Distal tubule: end of nephron before collecting duct; ion absorption and water reabsorption

• DIURETICS OCCURS (water pills rid your body of salt/sodium & water) → inhibit the NaCl transporter in distal tubule

Collecting duct: END of nephron; drainage & stores urine

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Urine Flow

Nephron→ Collecting Duct→ Minor Calyx→Major Calyx→ Ureter→ Urinary Bladder→ Urethra 

Adrenal gland: secretes ALDOSTERONE (antidiuretic) and ADRENALINE (epinephrine); cortisol 

• Urine: produced by nephrons
• NO PROTEIN in urine
  • Renal failure: high PROTEIN in urine
  • Diabetes: high GLUCOSE in urine (sugar is in bloodstream & cells are unable to take from the bloodstream = cells lack sugar intake) 
  • Keto diet: cells use fats instead of sugar for ATP
  • EXTREME STARVATION: KIDNEYS BREAK DOWN PROTEIN
  • So, glucose is primarily used. If no glucose is available, fats are broken down. If no fats, break down muscle/protein.

 Recta: Long, hairpin-shaped blood vessels parallel to loop of Henle; slows rate of blood flow to maintain osmotic gradient for WATER REABSORPTION 

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Urine Analysis: Clear Cut Lab 

Urine testing: looks for RBCs, WBCs

• RBCs should NOT be found in urine- NO cells should be found in urine (small amounts are okay). If large amounts are found, it is called proteinuria aka renal failure

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Pituitary gland- all this gland does is make hormones (primary endocrine gland) , however the kidney, liver, lungs also make hormones← (secondary endocrine gland) 

So lungs, for example, primary role is breathing but lungs are the secondary endocrine gland.

Know the difference between primary and secondary glands

Thymus Gland, Pituitary Gland, Adrenal Gland← Primary endocrine glands

Lungs, kidneys ← Secondary Endocrine glands

When people fast, very often people find ketones (essentially when you break down fats)  in urine. If you do find ketones in urine, it could be because you’re fasting, or you’re diabetic because your body doesn’t have sugar to go after so it has to go through fats. 

• When you’re diabetic, you have sugar in your body, it’s just in the wrong place; it’s in your blood, not the cell← the cell can’t pick up the sugar. 

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• Specific Gravity← how concentrated your urine is as compared to water. Higher specific gravity, meaning the higher the number of 1← 1 is water so anything higher than 1 is concentrated. Higher the number is, higher the concentration. 

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• About 1 million nephrons in the kidney

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• GFR is detected by macula densa cells

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• Urinary tract infection (UTI): difficult to diagnose because when we open the cap to do the urine sample, airborne particles contaminate it. You can’t say that anyone who has bacteria in the urine has an UTI. Everyone has bacteria in their urine, but there is a limit. Too much bacteria=infection 

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• Bowman's Capsule

  • contains the glomerulus

• Where does filtration occur?

  • Glomerulus only

• Pancreas

• Urine flow order

• Adrenal gland

  • secretes hormones such as aldosterone and epinephrine

• Vassa recta

  • Function
  • similar to peritubular capillaries, trap sodium chloride to ensure medulla is hypertonic to cortex so reabsorption can work

• Afferent and efferent vessels

  • AG like DNA (afferent has granular cells)

• Different tests in urinalysis (look for WBC and RBC)

  • what is abnormal and normal
  • glucose in urine is abnormal

• The descending thin loop is a primary site of water absorption. In contrast, the ascending loop is permeable to ions rather than water.

  • Loop of Henle contains the ascending and descending loops

• No cells should be found during urinalysis, signaling renal failure

• Pituitary gland

  • secretes hormones ONLY>>>>Primary endocrine gland

• Primary endocrine glands

  • Thymus gland
  • Pituitary gland
  • Adrenal gland

• Secondary endocrine glands

  • Lungs
  • Kidneys

• When people fast, they find ketones (think keto, ketones)

  • Ketones are byproduct of fat breakdown
  • Can cause ketoacidosis
  • High ketone levels can signal DIABETES
  • Cells do not receive glucose, glucose is sitting in bloods
  • Cells resort to metabolic breakdown of lipids

• Specific gravity means how concentrated urine is compared to water

  • Specific tests can measure specific gravity
  • >1 means more concentrated

• A million nephrons in the kidney

• UTI is very difficult to diagnose because of contamination of bacteria

• Nephrons are the units of the kidneys and are responsible for filtering blood and forming urine

  • consists of renal corpuscle and renal tubule
  • Two main nephrons: cortical and juxtamedullary

• Capillary vessel supply: glomerulus, peritubular capillary bed, vasa recta

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