Kidney

What is Kidney and their function or process

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Definition of Kidney/Excretory System :-

Kidney / Excretion system is a process of waste removal in the form produced during metabolic activities.

 

Kidney/Excretory Product’s :-

  1. Ammonia
  2. Urea
  3. Uric Acid
  4. Creatinine
  5. Guana 
  6. Hippuric Acid
  7. Greatine
  8. T.M.A.O.(Trimethyl/Amune Oxide)

Type’s of Organsim :-

  1. Ammonotelic :-
    • NH3
    • Most Toxic
    • Max H2O Needed
    • Readily Soluble in H2O
    • Ammonotelism
  2. Ureotelic :-
    • Urea moderately toxic 
    • Moderately H2O
    • Teretial Amptiuans
    • Example :-  Marune / Fishes
  3. Uricotelic :-
    • Example :- Bird’s , Reptiles, Land snail’s , Land Insect’s.

Human Excretory System :-

  1. A pair of Kidney
  2. A pair of Ureter’s 
  3. Urinary Bladder
  4. Urethra

{Right side kidney is slightly below left side due to above lying liver.}

So… What does the Urinary System Do ?

  • Keep my body balanced !
  • Cleaning the blood (metabolic waste’s N2)
  • Elimination of nitrogenous waste’s.
  • Excess solute’s (Ionic concentration)
  • Excess water (Osmoregulation)

Flow of urine :-

Renal Pyramid’s → Renal Papillae → Minor Cycles → Major Cycles → Pelvis → Ureter → Urinary Bladder → Outside.

Nephrone :-

  • The functional unit of the kidney are called Nephron.
  • Approx 1 million nephron are present in each.

2 Parts of Nephron

  1. Glomerulus :→ Glomerulus of capillaries in Bowman’s Capsule.
  2. Renal Tubule :→ 
    1. Bowman’s Capsule
    2. P.C.T. (Proximal Convoluted Tubules)
    3. L.O.H. (Loop of Henle)
    4. D.C.T. (Distal Convoluted Tubules)

Bowman’s Capsule :-

Bowman’s capsule is a part of the nephron that forms a cup-like sack surrounding the glomerulus. Bowman’s capsule encloses a space called “Bowman’s space,” which represents the beginning of the urinary space and is contiguous with the proximal convoluted tubule of the nephron.

Golomerules + Bowman’s Capsule  = Renal Capsule / Malphigiar

Renal Tubule :-

The renal tubule is a portion of the nephron responsible for homeostasis of fluids and electrolytes in the body. A renal tubule consists of a proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct.

Blood Supply :-

Heart → Aorta → Renal Artery →(enter Kidney) → Approx 1 million Afferent Arterioles → Glomerulus → Efferent Arteriole→ Peri-tubular (P.C.T. + D.C.T.) & Vasa Recta (L.O.H.) → Renal Venules →  Renal → Inferior venacava → Heart.

Types of Nephron :-

Their are 2 types of Nephron

  1. Cortical Nephron
  2. Juxtamedullary Nephron

1. Cortical-Nephrons(80%-85%) :-

  • Loop of Henle
  • No Vasa Recta
  • Major part lies in cortex region.
  • No role in H2O Conservation.
  • Peri-tubular capillaries well developed .

2. Juxta-Medullary Nephrons :-

  • Major role in H2O conservation 
  • Counter current Mechnism.

Physiology Of Excretion :-

  1. Urea Formation :- (Liver) {Liver cell → Hepatocytes → Mitrochondria or Cytoplasma} → {Urea Cycle / Kreb’s Hensleit cycle / Ornithine Cycle}
  2. Urine Formation :- (Kidney)

1. Urine Formation :-

The three steps of urine production are filtration, reabsorption, and secretion. In filtration, molecules and ions pass from the blood to the filtrate within the glomerulus. Reabsorption retains important molecules, glucose, amino acids, ions, and water back into the bloodstream.

  1. Ultra Filtration (Unbiosed Process).
  2. Re-Absorption.
  3. Tubular Secretion.
Ultra Filtration :-

  1. Filtration under High Pressure
  2. Occur’s in Glomerulus + Bowman’s Capsule = Renal Capsule / Malphigiar.
    1. Filtration Membrane 
      1. Endothelium Capillary
      2. Basement Membrane
      3. Podocytes
    2. Glomerular Filtrate
      1. Glucose
      2. H2O
      3. Hormone
      4. Slat’s 
      5. Uric Acid 
      6. Urea
      7. Mineral’s 
      8. Vitamin’s
  • Only Remain in Blood that is called Blood Cell’s & Protein’s.
  • Ultra Filtration is Unbased Process. {Because they remove both substance useful & non-useful substances}
  • 125 ml / minute of Glomerular Filtrate
  • 180{G.F.R. = Glomerular Filtration Rate} ml / day of Glomerular Filtration

Net Filtration Pressure :- Net / Effective Pressure at which Ultra Filtration occur = 10 – 20 mm of Hg {(B.P. Blood Pressure = Increase’s B.P.) , (N.F.P. Net Filtration Rate = Increase N.F.P.)}

2. Re-Absorption :-

  • Re-Absorption is a Absorption of useful substance’s from Nephron Back to Blood. It occur’s in – P.C.T. , L.O.H. , D.C.T. , C.T.
  • Re-Absorption in P.C.T. & L.O.H. is known as Obligatory Re-Absorption.
  • Re-Absorption in D.C.T. & C.D. is known as Facultative Re-Absorption.

Active Re-Absorption :- Glucose , Sodium , Amino Acid.

Passive Re-Absorption :- Remaining Substance’s

  1. P.C.T.(Proximal Convoluted Tubule)
    1. Glucose = 100% 
    2. Amino = 100%
    3. Urea = 50%
    4. Sodium = 70%
    5. Potassium = 70%
    6. Phosphate = 70%
    7. Calcium = 70%
    8. Magnesium = 30%
    9. H2O = 70%
  2. Thick Ascending Limg(T.A.L.)
    1. Sodium = 25%
    2. Potassium = 20%
    3. Calcium = 25%
    4. Magnesium = 60%
  3. Distal Convoluted Tubule(D.C.T.)
    1. Sodium = 5%
    2. Calcium = 8%
    3. Magnesium = 5%
    4. H2O & Urea is Variable
  4. Collecting Duct
    1. Sodium =3%
    2. H2O & Urea is Variable

Counter Current Mechanism:- Done in 3 Level’s 

  • Between Descending L.O.H. & Ascending L.O.H.
  • Between Descending V.R. & Ascending V.R.
  • Between Adjacent Lemb’s of V.R. & L.O.H.

3. Tubular Secretion :-

  • Active Process
  • Blood → Nephrone 
  • Only method of Blood Filtration in which Lack of Glomerule’s.

Excretion :- Filtration – Re-Absorption + Secretion.

Urine :-

95% of volume of Normal Urine is Due to Water.

Organic Component’s :- 

  • Urea
  • Urobilinogen
  • Uric Acid
  • Creatinine
  • Amino Acid
  • Metabolite’s Of Hormone’s

In-Organic Component’s :-

  • Cation’s – Na+ , K+ , Ca++ , 
  • Anion’s – Cl- , SO4- , HCO3- , HPO4+

Regulation Of Kidney Function’s :-

  1. A.D.H. :- Hypothalamus
  2. R.A.A.S. :- JGA (Juxta Glomerular Appaaratus)
  3. A.N.F. :- Heart

1. A.D.H.(Anti Diuretic Hormone) :-

  • Vasopressin (other name) Vessel Contriction
  • Diuresis (Excessive Urination)

Function’s :-

  1. Prevent Excessive Loss of Water in Urine.
  2. Increase Re-Absorption of Water in D.C.T. & C.T.
  3. Vesocontriction (Blood Pressure Increase)

A.D.H. Produced by Hypothalamus

A.D.H. Released by Post Pituitary. 

  • Secreted Under Following Situation
    • Water Loss – Excessive (Sweating , Diarrhoea)

Osmoreceptor’s in Body , Detcet :-

Osmolarity of Blood (During Summer)

When Osmolarity ↑ (Salt ↑) / H2O↓

⇓

Send signal to Hypothalamus

⇓

Hypothalamus produce A.D.H.

⇓

Effect D.C.T. + C.T.

⇓

H2O Re-Absorption Increase from D.C.T. + C.T.

⇓

Less Urine Formation

Osmolarity of Blood (During Winter)

H2O Level Normal

⇓

No A.D.H.(Anti Diuretic Hormone’s)

⇓

H2O Lost in Urine 

⇓

More Urination

2. R.A.A.S.(Renin Angiotension Aldosyerone System) :-

Renin :- Kidney

Angiotension :- Liver

Aldosyerone :- Adrenal cortexdd

RAAS is stimulated by → Low B.P. (G.F.R. is decrease)(Na+ is also decrease)

  • Juxta Glomerular Cell secrete Renin (When Na+ level decrease)
  • Macula Densa Cell detect Na+ level in blood .

When B.P. decrease (Na+)

↓(Hypotension)

Detected by Macula Densa

↓

Stimulates J.G.C. to release RENIN

↓

Angiotensinogen(In-Active) → Secreated by Liver

↓

Angio-Tension 1 (Less Potent){Angio – Veso , Tension – Constrictor}

↓(Angiotension Converting)

Angio-Tension 2(Strong / More potent) Enzyme (Lungs) 

  1. Angio
    1. Blood Vessels → Increase Vasocontriction → B.P. Increase’s
    2. Adrenal Cortex → Aldosterone → Increase Na+ Re-Absorption from D.C.T. + C.T. → H2O Re-Absorption → Blood Volume Increase’s → Blood Pressure Increase’s.
    3. Post Pituitary

3. A.N.F. (Atrial Natriuretic Factor) :-

When B.P. Increase (Hypertension)

ANF Secreted by ↓ Artrial Wall’s

Heart / Atrial Muscles release A.N.F.

↓  

Suppress R.A.A.S.

↓

Na+ & H2O Loss in Urine 

↓

B.P. Decrease’s (Diuresis) Excessive Urination.

Micturition :-

Practise of voiding / Emptying Bladder

Urine :- Slightly Acidic pH is 6.8 (Max. Capacity 350 – 500 ml)

150 ml Generate’s Feeling to void .        ⇒     Maximum Full Generate Strong urge to Void.

Micturition Reflex :-

  • In Urinary Bladder stretch receptor’s are present they will send signal to brain through the sensory neuron.
  • At this time Detrusor muscle’s will be contraction.
  • Stretch receptor’s are present in the wall’s of Bladder.
  • Brain send message / signal to Detrussor Muscle’s and Uretheral sphincter’s for Void the Urine.

Ureter’s & Urinary Bladder :-

Kidney Bladder
Kidney Bladder

The urinary bladder is a hollow, spherical-shaped organ that holds urine (pee). For most people, it can hold 500-700 mL (about two cups) of pee. When you need to use the restroom, muscles in your bladder contract (tighten) and sphincter muscles in your urethra relax, allowing pee to flow out of your body.

Role of Kidney in Blood Formation :-

When Hypoxia occurs (Pressence Of O2 decrease’s in Air) {∴ At Higher Altitude the Count of R.B.C. will as Increased}

↓

Stimulate’s Kidney to Produce Erythropoetin. {It required at leats 3-6 month 4-5 → 8 million/mm3}

                                    ↓

Stimulated Red Bone Marrow 

↓

Increase R.B.C.(Red Blood Cell’s) Production.