Urinary System

Urinary System Functions of Urinary System: Excretion- removing nitrogenous wastes, certain salts and excess water from blood. Maintain acid-base balance Secrete waste products in the form of urine – remove waste from body Eliminate urine from bladder

What if kidneys are not working properly? Toxic wastes would accumulate in the cells, poisoning them

Reasons for elevated BUN

Kidneys Bean-shaped organs                                                                                                                          Bean-shaped organs Located between peritoneum and the back muscles (RETROPERITONEAL) Renal Pelvis- funnel shaped structure at the beginning of the ureter

Medulla Inner, striated layer Striated cones (divisions) are renal pyramids Base of each pyramid faces cortex, while apex empties into cuplike cavities called calyces

Cortex Composed of millions of microscopic functional units called nephrons

Nephrons Functional unit of the kidney Over 1 million in each kidney which comprise 140 miles of filters and tubes Parts include: Bowman’s capsule Glomerulus Proximal convoluted tubule Loop of Henle Distal convoluted tubule Collecting tubule

Nephron structure Afferent arteriole – blood from renal artery enters through this… Bowman’s capsule – double-walled hollow capsule – surrounds glomerulus Glomerulus – knotty ball formed from afferent arterioles finely dividing – contains 50 separate capillaries Proximal convoluted tubule – twisted tubular branch off Bowman’s capsule

Nephron structure cont’d Loop of Henle – proximal convoluted tubule descends into the medulla forming large loop Distal convoluted tubule – ascending limb of Henle’s loop Collecting tubule – distal tubule opens into collecting tubule

Urine Formation in the Nephron 1- Filtration 2. Reabsorption 3- Secretion

Filtration First step in urine formation Blood from renal artery enters glomerulus High blood pressure in glomerulus forces fluid (Filtrate) to move into Bowman’s capsule (function of glomerulus is to filter substances from the blood) Filtrate does not contain plasma proteins or RBCs- they are too big Bowman’s capsule filters out 125cc of fluid/min. – 7500cc/hour As filtrate continues through nephron, 90% of water is reabsorbed

Reabsorption Water and useful substances are reabsorbed in proximal convoluted tubule If blood levels of certain substances are high (glucose, amino acids, vitamins, sodium) then those substances will not be reabsorbed Useful substances filter out of the renal tubules and back into the capillaries around the tubules = reabsorption

Filtration

Secretion Opposite of reabsorption Secretion transports substances from blood into collecting tubules Substances include creatinine, hydrogen ions, potassium ions, and some drugs Electrolytes are selectively secreted to maintain body’s acid-base balance

Urinary Output Average= 1500 ml/day Urinalysis- examination of urine to determine presence of blood cells, bacteria, acidity level, specific gravity and physical characteristics (color, clarity and odor) Normal in urinalysis = Ammonia not normal = glucose, blood, pus

Ureters One from each kidney Carry urine from kidney to bladder Smooth muscle tube with mucous membrane lining Peristalsis pushes urine down ureters The tubes that connect the kidneys and bladder.

Path of urine formation Afferent arteriole - Glomerulus – Bowman’s capsule – proximal convoluted tubule – loop of Henle – distal convoluted tubule – collecting tubule – renal pelvis - ureter

Urinary Bladder Hollow, muscular organ – in the pelvic cavity Made of elastic fibers and involuntary muscle Stores urine- usually about 500cc Emptying urine (voiding) is involuntary but controlled through nervous system (voluntary) Function = store and aid in elimination of urine Urine leaves through urethra to outside opening = Urinary Meatus

Chemical Control Reabsorption of H2O in distal convoluted tubule controlled by ADH (antidiuretic hormone) Secretion and regulation of ADH controlled by hypothalamus Diuretics inhibit reabsorption of H2O Medications can replace chemicals created by body i.e. renin = diuretic Production of urine is controlled by ADH and aldosterone

Chemical Control https://www.boundless.com/physiology/textbooks/boundless-anatomy-and-physiology-textbook/the-urinary-system-25/urine-241/regulation-of-urine-concentration-and-volume-1178-831/

Renin Urinary System Whereas adrenaline and noradrenaline enhance vasoconstriction, aldosterone influences the filtration function of the kidneys. The kidneys retain more sodium and water in the body and excrete more potassium. The vasopressin from the pituitary gland prevents the excretion of water without affecting the electrolytes sodium and potassium. In this way, the overall volume of blood in the body is increased: more blood is pumped through constricted arteries, which increases the pressure exerted on the artery walls – the blood pressure.

Chemical Control Aldosterone: promtoes excretion of potassium and hydrogen ions and reabsorption of sodium ions; acting on the distal tubules and collecting ducts of the nephron, increasing reabsorption of ions and water in the kidney, to cause the conservation of sodium, secretion ofpotassium, increase in water retention, and increase in blood pressure and blood volume If blood pressure drops too low, or blood volume gets too low, or too concentrated (not enough water in it), ADH released

ADH When the blood becomes more concentrated, as happens when an animal is deprived of water, ADH is secreted and causes more water to be absorbed from the collecting ducts so that concentrated urine is produced. When plenty of water has been consumed, and the blood is dilute, no ADH is secreted and no or little water is absorbed from the collecting ducts, so dilute urine is produced.

Chemical Control Diuretics increase urinary output by inhibiting reabsorption of water

Nervous Control Direct control through nerve impulses on kidney blood vessels Indirect control through stimulation of endocrine glands, whose hormonal secretions will control urinary secretion

Disorders of the Urinary System Renal Calculi (Kidney Stones) Made of crystals of calcium phosphate and uric acid Gradually they get larger until they block ureters…can causey hydronephrosis First symptom- severe pain Other symptoms- nausea and vomiting, frequency, chills, fever, hematuria Diagnosis- by symptoms, ultrasound, or x-ray Rx- increase fluids to flush out stone, medications, and if needed- lithotripsy

Lithotripsy Surgical procedure to remove kidney stones                                         Surgical procedure to remove kidney stones Shock waves hit dense stones and break them up Done on outpatient basis

Nephritis Inflammation of the kidney (kidney infection) Incontinence = Involuntary urination

Updated July 29, 2005        Cystitis Inflammation of the mucous membrane lining of the urinary bladder Most common cause- E. Coli Symptoms- Dysuria (painful urination), lower abd pain, and frequency Usually in females (shorter urethra) Rx- antibiotics

Dialysis (Hemodialysis) Used for kidney failure Involves the passage of blood through device with semipermeable membrane Dialysis serves as substitute kidney… replaces filtration Blood from patient flows through machine and is filtered Can be done at home or in clinic Takes 2-4 hours, 2-3 times a week

Kidney Transplant As a last resort Involves donor organ from someone with a similar immune system Main complication- rejection

Terminology Enuresis- bedwetting Incontinence – involuntary urination Gylcosuria- sugar in urine Nocturia- frequent urination at night Polyuria- large amounts of urine Anuria- no urine produced Hematuria- blood in urine Diuretic- drug or substance to increase urine production Oliguria – decreased urine production (sign of kidney failure)