Structure of The Kidney

Objectives Define the term excretion and explain the importance of removing waste material from the body Describe the process which forms urea from amino acids Describe the general structure of the kidney, the nephron, and associated blood vessels

Excretion What waste material do we produce? CO2 released through lungs Feces released through digestive tract Urine released through kidneys All are poisonous materials (toxins) Where do they come from? CO2 cellular respiration Feces material not absorbed by body Urine forms from urea; produced by the liver from excess amino acids

It All Starts In The Liver After absorption, food molecules are assimilated Assimilation to become a useful part of a cell or organ Roles of the Liver Glycogen is made from excess blood glucose Amino acids used to make proteins Fatty acids/glycerols are made into fat Form cholesterol from fat Excess amino acids deaminated; forms urea

Deamination: Forming Urea What are our major sources of energy? Carbohydrates, Fats, and Proteins How are carbs and fats stored? Proteins? Glycogen and fat (adipose tissue) Deamination removal of for amino group from an amino acid to form a keto acid and ammonia (NH3) Keto acids can form glucose and fat Ammonia is toxic

Deamination: Forming Urea To prevent damage from ammonia build up, ammonia instantly combines with CO2 and produce urea and H2O Urea passes from the liver into the blood plasma and then filtered out through the kidneys Uric Acid minor nitrogenous excretory product made from the breakdown of DNA

Structure of the Urinary System Renal artery takes unfiltered blood to kidneys Renal vein takes filtered blood from kidneys Kidney bean-shaped network of filtering units called nephrons Ureter carries urine from kidneys to bladder Bladder elastic storage area for urine Urethra carries urine from bladder to outside the body

Layers of a Kidney 2 main roles of kidneys: Removal of urea Regulating water levels, ion levels, and pH of blood (homeostasis) Capsule tough outer layer to protect kidney from damage 3 main areas of a Kidney Cortex contains all glomerulus, renal capsules, and area where ultrafiltation occurs Medulla contains kidney tubules and collecting ducts, and area where reabsorbtion occurs Pelvis where all collecting ducts meet to carry waste away through ureters

Glomeruli K L Cortex M Collecting ducts N Medulla O Pelvis

Structure of a Nephron Nephron (kidney tubule) filtration unit a kidney Renal (Bowman’s) capsule cup-shaped site where arterial blood is filtered Blood comes in from arteriole Glomerulus splitting capillaries in capsule to increase filtering rate Filtered blood leaves through the arteriole

Ultrafiltration Renal capsule filters urea, H2O, and small molecules from the blood Reabsorption pulls important molecules and H2O back into blood 3 layers of Filtration walls inside renal capsule have small gaps; only small molecules get through Blood cells are too big Blood pressure helps force waster material through filter and out of the blood (125 ml/min)

Reabsorption What inside the filtrate? What do we need back? Urea Water Glucose Na + / Cl-; Ions What do we need back? Glucose and Ions Capillaries wrapped about nephrons reabsorb glucose and ions into the blood Water is reabsorbed in the collecting ducts depending on your blood water levels Hydrated clear/light yellow Dehydrated dark yellow

Kidney Failure What happens when the kidneys shut down? Urea builds up in body Toxic levels effect organs; death What can cause kidneys to fail? Physical damage Blood clots; blockage in tubes Kidney Stones Toxins; Alcohol and Drugs Genetics; DNA Disease How do we know kidneys are damaged? Blood in urine Large proteins in urine Pain and illness

Living With One Kidney What does living with one kidney mean? More urea in blood Higher blood pressure More stress on remaining kidney Toxins have longer effects; alcohol and drugs Greater chance of losing other kidney What options do you have if you lose both kidneys? Dialysis Kidney Transplant

Kidney Dialysis Kidney dialysis machine filtering blood outside the body Machine draws out blood from vein Inside machine; blood passes by several dialysis membranes; Urea drawn out of blood into dialysis fluid (dialysate). How? Diffusion 3) Dialysis fluid is contains salt and sugar. Why? No diffusion; glucose/salts stays in blood 4) Filtered blood returns to body vein 3-4 hours; 2-3 times a week What diet must you have? Low-Protein = Less Urea

Kidney Transplant Kidney Transplant surgically replacing the damaged kidney with the healthy kidney of a donor What are the major difficulties with transplants? Donor match kidney must be excepted by body (donor should be related to you or similar in DNA) Drugs can lower white blood count to help kidney acceptance Might get really sick Dangerous surgeries always have a risk of killing the patient Expensive lots of money needed to get kidney and pay the hospital; plus after hospital care