The Urinary System

System Overview Consists of: Kidneys Ureters Urinary bladder Urethra

System Functions Removes certain salts and nitrogenous wastes from blood Helps maintain normal concentrations of water and electrolytes within body fluids Regulates the pH and volume of body fluids Helps control red blood cell (RBC) production and blood pressure

Kidneys - Function Remove substances from the blood Form urine Help regulate some metabolic processes by secreting hormones: Erythropoietin-RBC Renin-Blood Pressure

Kidneys - Location Either side of the vertebral column In a depression on the posterior wall of the abdominal cavity Between 12th thoracic and 3rd lumbar vertebrae Left kidney is usually higher Behind the parietal peritoneum Held in place by CT and adipose

Kidney Structure Hilium Renal pelvis Renal papillae Renal medulla Calyces Renal papillae Renal medulla Renal cortex Nephrons

Kidney Blood Supply Renal arteries Renal veins From abdominal aorta Branches in kidney to form afferent arterioles Renal veins Join the inferior vena cava

Nephron Structure Renal corpuscle Renal tubules Glomerulus Glomerular (Bowman’s) capsule Renal tubules Nephron loops (loop of Henle) Dump filtrate into collecting ducts  calyces

Blood/Urine Pathways

Urine Formation Urine is a product of nephron activity. It is formed by 3 processes: Glomerular filtration Tubular reabsorption Tubular secretion

Glomerular Filtration Produces filtrate (mostly water) Pressure for filtration comes from blood pressure Filtrate is similar to blood plasma

Urine Composition Reflects the amounts of water and solutes that the kidneys must eliminate or retain to maintain homeostasis Contains urea, uric acid, electrolytes, traces of amino acids Average urine volume 0.6-2.5 L/day Volume depends on fluid intake, temperature, relative humidity, emotional state, respiratory rate, body temperature Abnormal components: Glucose, proteins, hemoglobin, ketones, and blood cells

Urine Elimination Nephron  collecting ducts  calyces  renal pelvis  ureter  urinary bladder  urethra  outside of the body

Ureters About 25 cm long Extend from renal pelvis to the underside of the urinary bladder Muscular walls propel urine by peristalsis Flap-like fold acts as valve into the bladder

Urinary Bladder Hollow, distensible, muscular organ Stores urine Forces urine into the urethra Behind the symphysis pubis Trigone

Bladder Stone Removal (Rough)

Bladder Stone Removal (Smooth)

Bladder Location in Females

Male and Female Bladder

Micturition Aka urination Reflex triggered by stretching of the bladder: Detrusor muscle contracts. Abdominal wall and pelvic floor muscles contract. Voluntary relaxation of external urethral sphincter Reflex center located in the spinal cord. Reflex accompanied by sense of urgency. Bladder holds 600 ml,but urge begins at 150-300 ml.

Urethra Tube that conveys urine from the bladder to the outside of the body Contains urethral glands that secrete mucus into the urethral canal Incontinence

Dialysis Treatment