What is the difference between.....Excretion is removal of Defecation is removal ofnitrogenous wastes undigested waste
Types of nitrogenous wastesAMMONIA URIC ACID UREASome living beings waste in Some living Some livingthe form of ammonia. organisms release organisms releaseAmmonia is highly toxic. waste in the form of waste in the formThese organisms are known uric acid. of urea.as ammoniotelic. uric acid is least toxic. Urea is neutral andExamples- These organisms are less toxic.Sponges, coelenterates and called uricotelic. These organismsbony fishes. Examples- are called ureotelic. insects, reptiles and Examples- desert birds. mammals, cartilage ous fishes and humans
EXCRETORY SYSTEM IN HUMANS• The excretory system or the urinary system consists of a pair of kidneys• a pair of ureters• urinary bladder• urethra Location of the Kidney- In the abdominal cavity below the stomach, on either side of the vertebral column. The right kidney is placed slightly lower than the left kidney as it is pushed down by the large right liver lobe.
Blood vessels entering and leaving the kidneyThe descending aorta branches to form the renal artery that enters the kidney, andthe renal vein comes out of the kidney to join the inferior vena cava.Kidneys are bean shaped structures about 10 cm long. The outer side is convex andthe inner margin is concave. In the middle of the concave side a notch is presentthrough which structures enter and leave the kidney. This is called Hilum.
Other Parts of the Urinary SystemURETER URETHRA10-12 inches length, half an inch Narrow tube from bladder to thediameter. exterior.Enters the bladder throughoblique tunnels that function as Sphincters control the urination.valves. Female it is 3-4 cm long and males 18-Carries urine from kidney to the 20 cm long.urinary bladder.URINARY BLADDERPear shaped highly distensiblesac-like reservoir, store urinetemporarily.Present in the pelvic regionOpening to the urethra is guardedby sphincter muscles.Can hold about 0.5 to 1liter ofurine.
Internal Structure of the kidneyTwo distinct regions are seen-Cortex- Outer dark region has a dottedappearance.Medulla- Pale inner region has pyramidlike structures .The pyramids open into small tube likestructures the minor calyx and two orthree minor calyx opens into the a majorcalyx.The all the major calyces opens into thepelvis.The pelvis is the proximal end of theureter that receives the urine from thecalyces.
Structure of the Kidney Tubule• Each kidney is made up ofmicroscopic, coiled tube like units callednephrons or uriniferous tubules.• There are approximately 1.25 to 1.5million nephrons in one kidney.1. The nephron has two parts- A cup shaped body called Malpighian corpuscle or Renal corpuscle.2. A tubular part called renal tubule.Questions:1. What gives Cortex its dotted appearance?2. What gives Medulla a Striated appearance?
PARTS OF THE NEPHRON• Branches of the renal artery withinthe kidney produce afferentarterioles.• Each afferent arteriole leads to anetwork of capillaries calleda glomerulus.• Blood leaves the capillaries of theglomerulus via an efferentarteriole and enters capillaries in themedulla called peritubularcapillaries, which collect much of thewater that was lost through theglomerulus.Venules from the peritubularcapillaries lead to the renal vein, whichexits the kidney and returns blood tothe inferior vena cava.
RENAL TUBULEThe tubular part of the nephron is known asrenal tubule.It has three parts- Proximal convolutedtubule, Loop of Henle and distal convolutedtubule.The proximal part of the renal tubule is highlycoiled and is present in the renal cortex. This partabsorbs water and all the useful salts, aminoacids and glucose.The proximal part extends downwards to form a narrow tubular part- the descendingpart, a loop and an ascending part. This lies in the medulla and mainly absorbs waterfrom the nephric filtrate.The ascending limb leads to a convoluted part the which also lies in the cortex. Thisopens into the collecting tubule. This part excretes some ions and ammonia into thefiltrate.Try this link to lead yourself to a pretty good animation explaining the process. Http://www.biologymad.com/resources/kidney.swf
Urine FormationINVOLVES THREE PROCESSES:ULTRAFILTRATION.- Filtration underhigh pressure. Bowmans capsule actsas ultra-filters. When blood flowsthrough glomerular capillaries- allsubstances (except blood cells andplasma proteins) are filtered. Mainreason for ultrafiltration is thedifference in the size of afferent andefferent arterioles. The efferentarteriole are narrower than the afferentarteriole.TUBULAR REABSORPTION.- TUBULAR SECRETION.- secretion ofabsorption of useful substances from harmful substances from the blood intothe nephric filtrate into the blood. the nephric filtrate by the cells of DCT(diffusion and active transport)
Urine Formation cont.Steps of Urine Formation •Reabsorption of remaining water and Chlorides. BOWMAN’S •Re-absorbs most LOOP OF •Walls secrete K+ and CAPSULE water about HENLE foreign chemicals such •Ultrafiltration 2/3, and much of as penicillin and other •Receives glucose/Na+ / •Some absorption drugus into the glomerular Cl ion. of water and Na+ forming urine Filtrate Glomerulus PCT DCT
Role of Hormones in Urine Formation ADH- Anti Diuretic Hormone, Diuresis means increased production of urine • Results in reabsorption in collecting tubule • Secreted by posterior pituitary gland • It is released in response to high blood Osmolarity. • Increased osmolarity results from water loss and dehydration, thus body needs to retain more water. • ADH allows water to be reabsorbed from collecting tubule and not leave the body. • Water is absorbed by osmosis due to high Medullary hypertonicity. • Lack of ADH causes large amount of dilute urine. A condition called diabetes insipidus. • Question: Why during workout you are suggested to drink limewater instead of plain water?Reabsorption of NaCl from the distal convoluted tubule is controlled by aldosteronefrom the adrenal cortex. One of a group of hormones from theadrenal cortex called mineralcorticoids which regulate salt levels in the body.
Constituents of UrineOrganic Gm/L Inorganic Gm/LUrea 2.3 NaCl 9.0Creatinine 1.5 KCl 2.5Uric Acid 0.7 Ammonia 0.6Others 2.6 Others 2.5• Mainly Urine consists of about 95% WATER and 5% of SOLID wastes dissolvedin it.• Abnormal Constituents in urine1. Blood Cells- Blood passing thru’ Urine due to infection or kidney stone or tumor.2. Glucose/Glycosuria – Excess glucose passing through urine due to DIABETES MELLITUS.3. Albumin – Due to high BP or bacterial infection permeability of Bowman’s Capsule membrane increases.4. Bile Pigments- Anemia, Hepatitis (jaundice) or liver cirrhosis.