Excretory = Urinary System
Overall functions
• Water homeostasis • Cleanses body of waste such as urea • Keeps pH homeostasis
Anatomy
• Kidneys located in lower back region (nephr- & ren- are roots meaning kidney) • Ureters take urine from kidneys to bladder • Urinary bladder is in the pelvic cavity and stores urine • Urethra transports urine from the bladder to the outside opening of the body
Urine formation is at the microscopic level
• The nephron is the functional unit of the kidney where urine is made • There are millions of these microscopic structures
Nephrons
• Glomerulus is a clump of blood capillaries, where blood is filtered in order to make urine • Filtration is based on size, so a red blood cell would be too large to filter through the wall of the glomerulus
Nephron
• Bowman’s = Glomerular Capsule “catches” the filtered material from the glomerulus • aka the glomerular capsule
Nephron
• Renal tubules are tiny nephron tubes in which substances that are needed in the body can be reabsorbed back into the bloodstream. Some substances, such as drugs, can be secreted directly into the tubules if they are not filtered through the glomerulus.
Nephron
• Renal tubules empty their contents into the collecting ducts that carry the urine out of the kidney
Urine formation controls
• Blood pressure – as blood pressure increases, more blood can move through the glomerulus and urine production increases • Aldosterone – this hormone, made by the adrenal gland, results in sodium (salt reabsorption from the tubules; water follows
Controls
• ADH = Antidiuretic Hormone is made by a part of the brain called the hypothalamus • It causes water reabsorption from the renal tubules and thus the water goes back into the bloodstream. • If alcohol blocks ADH release, why are you thirsty with a hangover?
Urinary pathology
• Cystitis is a bladder infection • More common in women – look at the anatomy & see why • Can be diagnoses through an analysis of the urine called a urinalysis
Renal failure
• Destruction of more than 2/3 of your nephrons • Can you live with only one kidney? • Signs of renal failure are due to uremia – which is the build up of toxic waste products in your blood • Treatments include dialysis and transplant
Transplant