Part 3 Kidney and Excretion Ch. 14 Part 3 Kidney and Excretion

Major Organs to Know Kidney Liver producing hormones absorbing minerals filtering blood producing urine Liver Detoxification of blood

Excretion Removal of unwanted metabolic products made in body cells Toxic Excess molecules 2 biggest waste products: Carbon Dioxide Review respiratory Produced by AEROBIC respiration Dissolves in water  weak acid (carbonic acid) Too much = decrease pH = BAD Carried to lungs in blood plasma and expired and released when we breath out Nitrogenous Excretory Products Urea From catabolism of protein Produced in liver Carried in blood plasma to liver Leaves in urine Creatinine From breakdown product of creatine phosphate in muscle Made from Creatine (produced in liver using certain amino acids) Most used in muscles as creatine phosphate as ENERGY STORE Excess creatine converted to creatinine and excreted Uric Acid From Catabolism of nucleic acids made from break down of PURINES from nucleotides

Urea Adults produce 25 – 30 grams per day Made from excess amino acids DEAMINATION in liver occurs Removal of amine group form amino acid Amino Acid  Keto acid and Ammonia Keto acid Carbon skeleton of AA Enters KREBS CYCLE for respiration Changed to: glucose, glycogen, or fat Ammonia Soluble and Toxic (build up in blood BAD) What happens to amine group? Hydrogen atom added to Amine group (NH2) to make it NH3 (ammonia) Ammonia immediately converted to UREA (via Urea cycle) Ammonia + Carbon Dioxide = Urea

Step 1 In Liver… Step 2 In Liver…now urea can be carried in blood to kidney Urea will be dissolved with water and leave body as urine…once out of body, it will degrade back to AMMONIA Step 3

Kidney “Renal” pertaining to kidneys MAIN Function process the plasma portion of blood by removing substances from it (or adding) Variety of other Functions: Regulation of Water and inorganic ion balance Removal of metabolic wastes from blood and excrete through urine Removal of foreign chemicals from blood and excretion through urine Gluconeogenesis Production of hormones/enzymes (endocrine glands)

The Kidney Every minute 1300 mL of blood enter the kidneys 1299 mL leave the kidney 1 mL leaves as urine. Location: Posterior (back) Outside the abdominal cavity Behind the peritoneum of abdominal cavity

Structure of Kidney Renal Artery delivers blood TO the kidney Renal Vein blood LEAVES the kidney from here Ureter narrow tube that caries URINE away from kidney to bladder Urethra tube from bladder to outside of body Contains about 1 MILLION subunits called nephrons Nephrons contain: Renal corpuscle

Major Areas of Kidney Capsule Cortex Medulla Pelvis Tough outermost covering of kidney Cortex Beneath outer capsule Contains cup-shaped beginning structure of nephron called the renal capsule contains about one million blood filtering nephrons Medulla Central area of kidney Very SALTY!!!! (Hypertonic)  inner region of the kidney contains 8-12 renal pyramids pyramids empty into the calyx Medullary pyramids – formed by the collecting ducts, inner part of the kidney Pelvis basin-like area that collects urine from the nephrons narrows into the upper end of the ureter Calyx – extension of the renal pelvis; they channel urine from the pyramids to the renal pelvis

Nephron Glomerulus Bowmans Capsule Afferent arteriole Special type of network of capillaries Only oxygenated blood here Components of blood ill be squeezed out through these capillary walls FILTRATE No RBCs or small proteins leave Bowmans Capsule C-shaped structure that surrounds the glomerulus Receives filtrate Beginning of nephron tubes Afferent arteriole Brings blood to glomerulus Efferent arteriole Leaves the glomerulus Leads to there peritubular capillaries (go all around all the tubules of the nephron)

Reabsorption = when molecules LEAVE nephron and go back onto blood Proximal Convoluted Tubule (PCT) In CORTEX of kidney Receives filtrate Bowman’s Capsule Reabsorption of many molecules occurs here Water, glucose, ions, amino acids Sodium-Potassium pump important (Na-K) Co-Transport Symport important (Glucose) Loop of Henle (LOH) Dips into MEDULLA Descending LOH Water reabsorption Passive transport of water Ascending LOH Ion reabsorption (Na and Cl) Active transport Important in osmolarity Distal Convoluted Tubule (DCT) Back in CORTEX Receives filtrate from LOH More reabsorption Important in maintaining blood pressure Collecting Duct Dips back into MEDULLA and eventually into the PELVIS of kidney Receives filtrate from MANY DCT Reabsorption of water Reabsorption of some UREA (to maintain osmolarity of medulla)

How We Make Urine 2 Stages Ultrafiltration Selective Reabsorption Involves filtering small molecules out of blood and into Bowman’s Capsule Molecules flow through nephron and to ureter Selective Reabsorption When useful molecules (amino acids, glucose. Ions) are taken back from filtrate fluid and into the blood