Urinary System

Kidney

• Two bean shaped in retroperitoneal cavity
• surrounded by adipose tissue and fibrous CT
• size fist, weighs 4 to 6 lbs
• cortex region "bark"
• medulla region "marrow"
• Hilum- depression on medial border

Ureter

• 2 hollow muscular tubes: 16-18" long
• carries urine from kidney to the bladder

Urinary Bladder

• a hollow, muscular sac
• temporary reservoir for urine
• Trigone: a triangular region at the base, the place where the ureters enter and the urethra exit

Urethra

• a tube that carries urine from the bladder to the outside of the body
• Urination: process of expelling urine through the urethra (voiding)
• urinary meatus: the external opening of the urethra
• Female: 1.5" long, Male: 8" long
• Male: urethra runs through the prostate gland to the meatus at the tip of the penis

How the kidneys produce urine

Renal arteries

• blood enters kidneys from aorta by the way of the R & L renal Arteries

Arterioles

• smallest arteries
• blood passes slowly and constantly

Renin

• BP falls in kidney, produces renin
• contracts arterioles: to increase pressure and normal blood flow

Glomeruli

• each arteriole leads to tiny blood vessels (glomeruli)
• collection of tiny capillaries formed in the shape of a ball
• 1 million glomeruli in the cortex region of each kidney

Filtration

• urine is produced by filtration
• blood passes through the glomeruli, water, salts, and urea and other wastes leave the blood stream

Creatinine and Uric Acid

• waste products leave the blood stream

Glomerular (Bowman) capsule

• cup-like structure that surrounds each glomerulus
• waste products collect in the Bowman Capsule
• The walls of the glomeruli prevent large substances (proteins and blood cells) from filtering into the capsule
• Protein and blood cells normally do not appear in the urine.

Renal Tubule

• a twisted tube attached to Glomerular capsule
• As water, salts, urea and other wastes pass through renal tubule, most of the water, all of the sugar, and some salts return to the bloodstream
• All collecting tubules lead to the renal pelvis

Reabsorption

• the active process of reabsorption ensures that the body retains essential substances such as sugar, water and salts

Secretion

• the final process in the formation of urine
• the waste products of metabolism become toxic if allowed to accumulate in the body
• The waste products (drugs, acids, potassium) leave the body in urine

3 steps in the formation of urine

• Glomerular filtration
• Tubular Reabsorption
• Tubular Secretion

Nephron

• Combination of a glomerulus and a renal tubule forms a unit
• Each kidney contains about 1 million nephrons

Leaving the Body

• The renal pelvis narrows into the ureter
• the ureter carries the urine to the urinary bladder
• the bladder temporarily stores urine
• as bladder fill, pressure increases at the base of the bladder
• individual notices a need to urinate and voluntarily relaxes the sphincter muscles so urine can be passes out of the body