The process of separation, collection and elimination of toxic waste products (especially nitrogenous wastes) from the body Waste products are formed due to catabolism of amino acids, glucose, glycerol and fatty acids.Excreti Unwanted substances like Drugs, pigments, excessive vitamins, CO2, H2O on Excess of inorganic salts, hormones Bilirubin and biliverdin. Kidneys play a major role as an excretory organ in all vertebrates. Skin helps in elimination of urea; inorganic salts and water through sweat glands. Lungs help in the elimination of CO2 and H2O
The process by which the relative proportion of water and solutes (salts, glucose, etc) in the body-fluids and cells are kept constant.Osmoregulatio Osmoregulation controls the n osmotic pressure of body fluids and maintains the volume of blood constant Osmoregulation maintains the necessary required concentration of electrolytes in the body fluids
AMMONOTELISM UREOTELISM URICOTELISM Nitrogenous waste in the Nitrogenous waste in the Nitrogenous waste inform of ammonia form of urea the form of uric-acidformed in the liver by formed in liver by ornithine formed in the liver by thedeamination of amino-acids cycle. (NH2-CO-NH2) ionosinic pathway.least expenditure of energy. relatively more expenditure high expenditure of energy. of energy.highly toxic comparatively less-toxic Uric-acid is non-toxic.highly soluble in water. a good solubility in water. is insoluble water.excreted rapidly in urine excreted at a (comparatively) excreted very slowly slower rate.Dilute urine concentrated urine of thick paste or semi-solid pellets500 ml of water is 50 ml of water forRequired for elimination elimination of 1 gm of urea. 10 ml of water forOf 1 gm of ammonia elimination of one gm
AMMONOTELISM UREOTELISM URICOTELISMAquatic invertebrates mammals like man,whale, land-animals like birds,sponges ,bonyfish, jelly-fish amphibians like frog,aquatic reptiles (lizard, snakes), landaquatic amphibians, reptiles like turtles and snails and insectsaquatic insects etc tortoise and cartilagenous fish.
In man and other mammals, small quantity of uric acid is formed in the body bybreakdown of purine and pyrimidine nitrogen bases of nucleic acid.In some persons, due to defective metabolism, excess uric acid is produced whichgets deposited in joints of bones causing painful arthritis called gout.GUANOTELISM – Arachnids (spiders, scorpions) and penguins excrete mostly guanine(nitrogen base) and hence are called guanotelic.Protonephridia or flame cells -- Platyhelminthes (Flatworms, e.g., Planaria),rotifers, some annelids and the cephalochordate – AmphioxusNephridia -- Earthworms and other annelids..Malpighian tubules -- most of the insects including cockroaches..Antennal glands or green glands -- crustaceans like prawns
KidneysPair of bean shaped, chocolate brownstructures situated in the dorsal side of theabdominal cavity- behind the peritoneum (retroperitoneal)- one on either side of the vertebral-columnbetween the 12th thoracic and 3rd lumbarvertebrae.The right kidney is slightly lower than the leftkidney-11 cms long, 6 cms broad and 3 cms thick-150 grams in males and 135 grams in females
KidneysEach kidney is covered by a fibrouscapsule, over which lies a layer of adiposetissue (peri-renal fat) and the outermostfibrous sheath (renal-fascia).The outer margin of both kidneys isconvex. The inner margin is concave andshows a notch, called hilum.The renal-artery, renal-vein, lymphatic-vessels, nerves, renal-pelvis (upperexpanded end of the ureter) enter thekidney through the hilum.The upper pole of each kidney is broadand has an adrenal (suprarenal) glandattached to it
Ureters Each ureter arises from the hilum ofthe kidney by forming a funnel shapedexpanded renal-pelvis, runsdownwards, enters the bladder wallobliquely (on the dorsal side) andopens into it. Structure : They are a pair ofnarrow, thin-walled muscular tubesmeasuring about 25 cms in length and3-6 mm in diameter.Function: They carry urine from thekidneys to the urinary bladder byrhythmic contraction of its muscle-walls (peristaltic movements).
•Position : It is situated in the pelvic-cavity in Bladderfront of the rectum in the male and in front ofthe uterus in the female. (i.e. the womb, whichlies between the bladder & the rectum).Structure :•It is a median (central), single, hollow, ovoid orpear shaped, distensible muscular sac.It alsoshows a thick layer of smooth muscles calleddetrusor muscles lined by transitionalepithelium that allows expansion.•In the lower part of the posterior wall lies aninverted triangular area called the trigone.Theureters open into the upper lateral angles ofthis area while the opening of the urethra(internal urethral orifice) is located at thelower end (apex of the triangle).Function :•It acts as a temporary reservoir for the storageof urine.•It helps in micturition (urination). (Theprocess of voiding of urine by contraction ofthe bladder wall and relaxation of the urethralsphincters).
UrethraMales : Urethra is 20 cms long extends fromthe lower end (neck) of the bladder (internalurethral orifice) to the tip of the penis(external urethral orifice).In females it is 4 cms long it opensseparately just in front of vagina.The flow of urine is guarded by sphincters.The internal urethral sphincter at the neckof the bladder (i.e. internal urethral orifice)is involuntary, while the external urethralsphincter, situated at a lower level (i.e.below prostate gland) is under voluntarycontrol(after 2 years of age).Females: it carries urine only.In males the urethra joins with theejaculatory duct (to form the urinogenitalduct) and carries both urine & semen.
Urine formed by the nephrons isultimately carried to the urinarybladder where it is stored till avoluntary signal is given by the centralnervous system (CNS).This signal is initiated by thestretching of the urinary bladder as itgets filled with urine. In response, thestretch receptors on the walls of thebladder send signals to the CNS The CNS passes on motor messagesto initiate the contraction of smoothmuscles of the bladder andsimultaneous relaxation of the urethralsphincter causing the release of urine. The process of release of urine iscalled micturition and the neuralmechanisms causing it is called themicturition reflex
A longitudinal section through the kidneyshows the following parts from outside in :1) The outer reddish brown cortex,2) The inner pale medulla and 3) The renal-sinusA) MEDULLA :•It is the inner, pale, striated part. It is made up of about 4-14, striated conicalmasses called the renal pyramids. Each pyramid has its base directed outwards(towards the cortex) and its apex inwards(called renal-papillae).B) CORTEX : It forms the outer (peripheral), reddish-brown, granular part.•Parts of the cortical tissue invade themedulla and lie between adjacent pyramidsand are called renal-columns (Bertini’scolumns).
C) RENAL-SINUS : Internally, the hilum leads to aspace called the renal-sinus, which is occupiedby the upper, expanded part of the uretercalled the renal-pelvis. The renal-pelvis divides into two orthree parts called major-calices (single calyx→cup of a flower). Each major calyx divides into 6-20minor-calices. Each minor-calyx is shapedlike a cup.•The papilla of a medullary pyramid fits intothe minor calyx. Each kidney consists of closelypacked microscopic coiled tubular structurescalled nephrons. The nephrons are thestructural and functional units of the kidney.There are about 1.2 million nephrons in eachkidney.
It is double-walled, cup shaped blind-opening inthe cortex. It is about 1.2 mm in widthOuter wall : PARIETAL LAYER : squampous epitheliumInner wall : VISCERAL LAYER : special squamous cells called PODOCYTESThe body of the podocytes rest on feet likeprocesses called ‘pedicels’.The individual legs, have foot processes.The gaps (slits) between the foot processes are inintimate contact with poresin the endothelium ofblood capillaries, through a permeable basementmembrane
GLOMERULUS (BLOOD-SUPPLY) : It is a rounded tuft of bloodcapillariesfound in the cup of theBowman’s capsule. The renal artery(a branch of theabdominal aorta) enters through thehilus, divides and re-divides to formmany branches. One branch called theafferent renal arteriole enters the cupand divides to form the Glomerulus.•The capillaries reunite to form theefferent renal arteriole. It leaves theglomerulus.•The diameter of the efferent arteriole islesser than that of the afferent one.
THE PROXIMAL CONVOLUTEDTUBULE (P.C.T) It is a highly coiled structure,connected to the neck and lies in thecortex.It is lined by cuboidal cells, rich inmitochondria, and having microvilli(brush border to increase surfacearea) and thus help in activereabsorption.
B) THE MIDDLE LOOP OF HENLE : The renal tubule now descendsinto the medulla (thin walled descendinglimb),takes a hair pin turn (the U-shapedloop) and ascends back towards thecortex (thick walled ascending-limb).The ascending limb is not permeable towater.The Henle’s loop is mainly meant forconcentration of urine.
THE DISTAL CONVOLUTEDTUBULE (P.C.T)The D.C.T leads to a straight, largecollecting-tubule. Many nephrons openinto the same collecting tubule. Manycollecting tubules join to form a collectingduct which descends into the medullarypyramids. The medullary pyramids arebasically a bunch of these collectingducts. About 7-8 collecting ducts drainingdifferent nephrons join to form ducts ofBellini, each of which opens into a minorcalyx at the apex (papilla) of a medullarypyramid.
BLOOD SUPPLY :The efferent renal arteriole which leavesthe Bowman’s capsule breaks to formperitubular-capillaries around the wholerenal tubule.The capillaries around the loop of Henleare called as vasa rectae.The capillaries reunite to form a renalvenule and carry the blood away from thenephrons. The renal venules join to formthe renal-vein, which passes out of thekidney to join the inferior vena cava.Functions of the renal-tubule :•Helps in the selective reabsorption ofessential substances like H2O, glucose,salts etc.• Helps in the tubular-secretion ofunwanted substances.
Site : In the malpighian bodyPrinciple: It is a physical process.The diameter ofthe afferent arteriole is bigger than the efferentarteriole thus creating pressure in the glomerulus.The glomerularhydrostatic pressure is the bloodpressure in the glomerular capillaries which isabout 55mm of Hg.The colloidal osmotic pressure of blood which is30 mm of Hg due to the presence of plasmaproteins. It opposes the glomerular (capillary)hydrostatic pressure. The net (effective) filtration pressureThe capsular (filtrate) hydrostatic pressure of EFP = GHP-(BCOP + CHP)glomerular capsule is caused by filtrate =55 - (30 + 15)thatreaches into the Bowmans capsule. It is about = 10 mm of Hg15 mm of Hg.It also opposes theglomerularhydrostatic pressure
The afferent arteriole brings in blood at 625 ml/min.1/5th of it gets filtered.i.e. the ultrafiltration rate is 125 ml/min or about 180 litres/dayThis rate of formation of filtrate is called glomerular filtrate rate (GFR)Process : The epithelial cells of the visceral layer of the Bowman’s cup are called podocytes. Thebody of the podocytes rest on feet like processes called ‘pedicels’. The individual legs, have footprocesses. The gaps (slits) between the foot processes are in intimate contact with pores in theendothelium of blood capillaries, through the permeable basement membrane. This arrangementfacilitates the transfer of fluids.Because of the high blood pressure, about 1/5th of the blood (plasma) gets filtered via these filtrationpaths into the urinary space of the Bowman’s capsule.Final product : The glomerular filtrate, which contains all the constituents of blood (i.e. glucose,amino-acid, salts, water, urea etc.) except blood-cells, plasma-proteins and fats(too big for the pore-size), hence called as deproteinized plasma.
Glucose, Amino acids, P.C.T Active reabsorption Vitamins, Na+,K+,Ca+,PO4- Water (75%), Urea and Cl- Passive reabsorption (ISOTONIC) Desc. Limb Passive reabsorption Water (5%)H2O : PermeableSolutes : Impermeable (Due to Increased medullary (HYPERTONIC) tissue osmotic pressure) At the bend Asc. Limb First Na+ followed by bothH2O : Impermeable Passive reabsorption Na+ and Cl-Solutes : Permeable Cl-, K+ Active reabsorption (HYPOTONIC) D.C.T Water (15%) Passive reabsorption (under the influence of ADH) Water (4%) C.T (HYPERTONIC)
Site : Proximal and Distal convoluted tubule and partially inthe collecting tubule.Principle : Some substances that escape ultra filtration aretaken to the peritubular capillaries and excreted in the filtrate.Process : Ammonia, Creatinine, K+, H+, drugs (e.g penicillin)are excreted in this process.For every K+ or H+ ion excreted a Na +ion is reabsorbed.The H + ion concentration (& thus acid-base balance) can bemaintained.Final product: Concentrated Urine, containing 50% of ureafound in glomerular filtrate.
FLUID BALANCE ELECTROLYTE BALANCEControlled by ADH from the post pituitary Controlled by Aldosterone from the adrenal cortex i) When the amount of water in the •The concentration of Na+, K+, Cl-, Ca+ Mg+,body is less, ADH secretion is increased, HCO3- etc. is regulated by their increased orwhich increases the reabsorption of decreased reabsorption in the P.C.T.water (facultative reabsorption) fromthe distal convoluted tubule and •Calcium ion concentration is maintained bycollecting tubule thereby secreting a CALCITONIN(thyroid gland) andsmall amount of concentrated PARATHORMONE(parathyroid gland).(hypertonic) urine. ALDOSTERONE, a hormone secreted by theii) When the water intake is more, ADH adrenal-gland helps in reabsorption of Na+ bysecretion is decreased, which makes excreting K+ in exchange, in the DCT &the DCT and collecting tubule less collecting tubulepermeable to water and a largeamount of dilute urine is excreted
COMPOSITION OF URINE :a) Volume : Average 1,200-1,500 ml/day.b) Colour : Pale yellow, due to mainly urochrome a bile derivative urobilin &urethrin contribute to it.c) Specific gravity : 1.01 to 1.03.d) Reaction : Slightly acidic (pH 5-7)e) Odour : Ammoniac.f) ConstituentsOrganic : Urea mainly, Uric acid, Ammonia and Creatinine.Inorganic : 95% Water and chlorides, sulphates & phosphates of sodium,potassium, calcium and magnesium. (sodium-chloride is the most abundant of allthese salts).
•Carbohydrates Proteins ketone bodies Blood Bile salts Bile pigments FatsCARBOHYDRATESCarbohydrates present in it such as lactose and fructose.Physiologically in pregnany and lactation, lactose is excreted in pregnant women.Pathologically: if lactose is excreted in the urine, then this is due to lactose intolerance.Glucose could be excreted in the urine in Diabetes mellitus, glucosuria, renal glycosuria etcFructose in essential fructosuriaGalactose in galactosemiaPROTEINS:Secretion of proteins in urine is due to:1- Increase in the permeability of the glomerular capillaries as in nephrotic syndrome etc2- Damage to the capillaries membranes as in glomerulonephritisFollowing proteins can be excreted in abnormal urine:•Albumin•Globulin•Hemoglobin (protein of RBC)•Myoglobin
Albumin and globulin are found in the urine in the condition called proteinuria, also innephrotic syndrome and glomerular nephritis.Hemoglobin is excreted in urinay tract infections.Myoglobin is excreted due to muscular atrophy etc.KETONE BODIESthey are basically three chemicals viz.•acetone•acetoacetic acid•beta hydroxy butaric acidAll the three are the intermediates in the fats metabolism.Increased catabolism of fats is due to•starvation•increased fat intake in diet•decreased carbohydrates in the diet•diabetes ketoacidosis
FUNCTIONS OF KIDNEY:1. By excretion, they eliminate poisonous nitrogenous waste products (like urea, uric-acid, ammonia) in the urine.2. During excretion, they remove unwanted substances like drugs, pigmentsexcessive vitamins etc. from the body.3. By Osmoregulation, they regulate the amount of water and salts i.e. theosmotic pressure of body fluids and maintain the volume of blood constant.4. By Osmoregulation, they maintain a necessary required concentration ofelectrolytes (Na+, K+, Cl-, Ca+) in the blood.5. They regulate the pH and acid base balance of the body by removing excessiveacidic or basic substances (H+ ions concentration) from it.6. During hypotension (low B.P.), they maintain the pressure of the bloodconstant by secreting enzyme renin from it which increases the B.P.7. They help in production of R.B.C.s (erythropoiesis by secreting ‘ renal-erythropoietic factor (REF) i.e. erythropoietininto the blood.8. They help in formation of active form of Vit-D (1,25 dihydroxy cholecalciferol
SKIN AS AN EXCRETORY ORGAN : The skin is double-layered i.e. outer epidermis and inner dermis.Within the dermis are present hair-follicles, sweat glands and sebaceous glands.SWEAT-GLANDS : They are highly coiled glands found more in forehead, armpits, palms and soles of feet.The secretory part (coiled) lies deep below in the dermis and is connected to the skin surface asperspiration pore via a long, narrow duct. They are simple, unbranched, tubular glands.Functions :•They secrete a colourless salty-fluid called sweat carrying excessive water, sodium-chloride, urea, uric-acid, lactic acid, glucose and amino-acids.•Thus it regulates the water-balance, salt-balance, excretion (little urea) and cools down the body(thermoregulation) i.e. water converted into vapour by excessive heat.SEBACEOUS GLANDS :They are alveolar glands present in connection with the hair follicles.Functions :They secrete ‘sebum’, which is rich in waxes, sterols, hydro-carbons and fatty acids.Sebum makes the skin water-proof (due to wax) and has an antiviral & antibacterial activity.
LUNGS AS EXCRETORY-ORGANS :The byproducts of cellular respiration are water&CO2.The partial pressure of CO2 is higher in the deoxygenated blood of alveolar capillaries oflungs, brought from all the parts of the body, than in the alveolar air. Hence it diffusesinto the alveoli and is exhaled out.Our lungs remove large amounts of CO2 (18 litres/day).Water is also lost from the lung surface by evaporation (Vapour). This has a coolingeffect (thermoregulation) in many animals.LIVER : The largest gland in our body, secretes bile-containing substances like bilirubin, biliverdin, cholesterol, degraded steroid hormones, vitamins and drugs.Most of these substances ultimately pass out alongwith digestive wastes and some inurine
The Henle’s loop and vasa recta play a significant role in this. The flow of filtrate in the two limbs of Henle’s loop is in opposite directions and thusforms a counter current. The flow of blood through the two limbs of vasa recta is also in a counter current pattern.The proximity between the Henle’s loop and vasa recta, as well as the counter current inthem help in maintaining an increasing osmolarity towards the inner medullary interstitium,i.e., from 300 mOsmolL–1 in the cortex to about 1200 mOsmolL–1in the inner medulla. Thisgradient is mainly caused by NaCl and urea.NaCl is transported by the ascending limb of Henle’s loop which is exchanged with thedescending limb of vasa recta. NaCl is returned to the medullary interstitium by theascending portion of vasa recta. Similarly, small amounts of urea enter the thin segment ofthe ascending limb of Henle’s loop which is transported back to the medullary interstitiumby the collecting tubule. The above described transport of substances facilitated by thespecial arrangement of Henle’s loop and vasa recta is called the counter currentmechanism.This mechanism helps to maintain a concentration gradient in the medullary interstitium.Presence of such interstitial gradient helps in an easy passage of water from the collectingtubule thereby concentrating the filtrate (urine). Human kidneys can produce urine nearlyfour times concentrated than the initial filtrate formed.
Failure of kidneys to adequately filter toxins and waste products from the blood1. Decrease in the glomerular filtration rate.2. Elevated serum creatinine level.3. Abnormal fluid levels in the body,4. Deranged acid levels, abnormal levels of electrolytes potassium, calcium, phosphate, and (in the longer term) anaemia.5. Depending on the cause, hematuria (blood loss in the urine) and proteinuria (protein-loss in the urine) may occur.6. Long-term kidney problems have significant repercussions on other diseases, such as cardiovascular disease.
Acute Kidney Injury Chronic Renal Failure- Rapidly progressive loss of renal function -Chronic kidney disease (CKD) may develop- Oliguria slowly and initially, show few symptoms.-Pre renal, intrinsic or post renal causes - CKD can be the long term consequence of- body water and body fluids disturbances irreversible acute disease or part of a disease and electrolyte derangement progression-AKI may result from a variety of causes, generally classified as prerenal, intrinsic and postrenal.
Blood drained from a convenient artery is pumped into a dialysing unit after adding ananticoagulant like heparin. The unit contains a coiled cellophane tube surrounded by a fluid (dialysing fluid) havingthe same composition as that of plasma except the nitrogenous wastes. The porous cellophane membrane of the tube allows the passage of molecules based onconcentration gradient.As nitrogenous wastes are absent in the dialysing fluid, these substances freely moveout, thereby clearing the blood. The cleared blood is pumped back to the body through a vein after adding anti-heparinto it.
The stones are solid concretions or calculi (crystal aggregations) formed in the kidneysfrom dissolved urinary minerals.Nephrolithiasis refers to the condition of having kidney stones. Urolithiasis refers to the condition of having calculi in the urinary tract (which alsoincludes the kidneys), which may form or pass into the urinary bladder.Ureterolithiasis is the condition of having a calculus in the ureter, the tube connectingthe kidneys and the bladder.There are several types of kidney stones based on the type of crystals of which theyconsist. The majority are calcium oxalate stones, followed by calcium phosphate stones.More rarely, struvite stones (magnesium amminium phosphate) are produced by urea-splitting bacteria in people with urinary tract infections, People with certain metabolic abnormalities may produce uric acid stones orcystinestones.
URAEMIA :Normal value of urea in blood is 0.01 to 0.03%, but when the level rises to above0.05% then it is called uraemia. It is highly harmful and it may lead to kidneyfailure.NEPHRITIS :It is referred to as Glomerulonephritis or Bright’s disease is the term used fordiseases that primarily involve renal glomeruli like haematuria, proteinuria,hypertenstion, oedema and oligouria.Streptococcal glomerulornephritis is common form seen mostly in childrenchildren of 6 to 16 years. It is due to infection of throat called streptococcalpharyngitis.