The Urinary System - PowerPoint PPT Presentation

The Urinary System

DeShawn Lowery

Nate Falk

Period 3

• The Urinary system removes certain salts and nitrogenous wastes.
• Helps maintain the normal concentrations of water and electrolytes within body fluids.
• Regulates the pH and volume of body fluids.
• Helps control red blood cell production and blood pressure.

• Kidneys: on the posterior wall of the abdominal cavity.
• Ureters: extends downward behind the parietal peritoneum and runs parallel to the vertebral column.
• Urinary Bladder: within the pelvic cavity, behind the symphysis pubis and beneath the parietal peritoneum.
• Urethra: its wall is lined with mucous membrane and contains a thick layer of smooth muscle tissue.

• Kidneys: Removes substance from blood, form urine, and help regulate certain metabolic processes
• Ureters: transport urine from the kidneys
• Urinary Bladder: Stores urine
• Urethra: conveys urine to the outside of the body.

• The kidneys are high on the posterior wall of the abdominal cavity.
• An adult kidney is about 12 cm long, 6 cm wide, and 3 cm thick.
• The left kidney is usually 1.5 – 2.0 cm higher than the right one.

• A kidney contains a hollow renal pelvis.
• The ureter expands into the renal pelvis.
• Renal papillae project into the renal sinus
• Each kidney divides into a medulla and a cortex

• Maintain homeostasis by removing metabolic wastes from blood and excreting them.
• Regulates…..
• Red blood production
• Blood volume
• Blood pressure
• The volume, composition, and pH of body fluids.

Renal Artery hilum interlobar

arteries arcuate arteries interlobar

arteries afferent arterioles renal vein

• A nephron is the functional unit of the kidney
• A kidney contains about 1 million nephrons.
• It is make up of a renal corpuscle and a renal tubule.

• A renal corpuscle is composed of a tangled cluster of blood capillaries called a glomerulus.
• Glomerular capillaries filter fluid (first step of urine formation).
• Segments of the renal tubule include the proximal convoluted tubule, nephron loop, and distal convoluted tubule, which empties into a collecting duct.
• The collecting duct empties into the minor calyx of the renal pelvis.

• Glomerular Filtration: filtration of plasma by the glomerular capillaries.
• Tubular reabsorption: moves substances from the tubular fluid back into the blood within the peritubular capillary into the renal tubular.
• Tubular Secretion: moves substances from the blood within the peritubular capillary into the renal tubule.

• The first step in urine formation is filtration of substances out of glomerular capillaries and into the glomerular capsule.
• Glomerular filtrate passes through the fenestrate of the capillary endothelium.

• As colloid osmotic pressure in the glomerulus increases, filtration rate decreases.
• As hydrostatic pressure in the glomerular capsule increases, filtration rate decreases.
• The kidneys produce about 125 milliliters of glomerular fluid per minute, most of which is reabsorbed.

• Filtration is due mainly to hydrostatic pressure inside glomerular capillaries.
• The osmotic pressure of plasma and the hydrostatic pressure in the glomerular capsule also affect filtration.

• When the macula densa senses decreased amounts of chloride, potassium, and sodium ions in the distal tubule, it causes juxtaglomerulaar cells to release renin.
• This triggers a series of changes leading to vasoconstriction of afferent and efferent arterioles, which may affect glomerular filtration rate, and aldosterone secretion, which stimulates tubular sodium reabsorption.

• Substances are selectively reabsorbed from glomerular filtrate.
• The peritubular capillaries permeability adapts it for reabsorption.
• Most reabsorption occurs in the proximal tubule, where epithelial cells have microvilli.

• Secretion transports substances from plasma to the tubular fluid.
• Potassium and hydrogen ions are secreted both actively and passively.

• Urine is about 95% water, and it also usually contains urea and uric acid.
• Urine volume varies with fluid intake and with certain environmental factors

• Urea is a by-product of amino acid catabolism.
• Urea enters the renal tubule by filtration, about 50% of it is reabsorbed, and the rest is excreted by urine.
• Uric acid is a product of the metabolism of certain organic bases in the nucleic acids.
• Active transport reabsorbs uric acid. Some uric acid is secreted into the renal tubule.

• Peristaltic waves in the ureter force urine to the urinary bladder.
• The urinary bladder stores urine and forces it through the urethra during micturition.
• Micturition expels urine from the urinary bladder.
• In micturition, the detrusor muscle contracts, along with the abdominal wall and pelvic floor.

• Kidney Stones: kidney stones are formed in uric acid, calcium oxalate, calcium phosphate, or magnesium phosphate, and can form in the collecting ducts and renal pelvis.
• Causes include excess vitamin D, blockage of the urinary tract, or a complication of a urinary tract infection.
• Can be avoided by drinking a lot of water.