The Mammalian Excretory System Principles of Modern Biology

The Mammalian Excretory System Principles of Modern Biology II At Wilkes University Kenneth M. Klemow, Ph. D.

One problem: • Mammalian blood contains metabolic waste products that must be removed without removing useful materials. http: //mdc. mo. gov/kids/out-in/1998/1/back 3. jpg

Another problem: • Terrestrial mammals must maintain a relatively constant osmotic level. • Living on land promotes desiccation; thus must retain water. • Occasionally we have excess water and must excrete it. http: //www. fairfaxcounty. gov/dpwes/image s/recycling/giraffecolor. jpg

The solution • Mammals have an excretory system that removes waste products and maintains osmotic balance.

Mammalian excretory system • Kidneys • Ureters • Urinary bladder • Urethra http: //upload. wikimedia. org/wikipedia/commons/thumb/1/ 18/Illu_urinary_system. jpg/300 px-Illu_urinary_system. jpg

The mammalian kidney • Cortex • Medulla • Renal pelvis • Renal pyramids • Blood vessels • Renal artery • Renal vein • Ureter http: //research. surgery. wisc. ed u/southard/organs/kidney. gif

The mammalian kidney • Have gradient of increasing salinity from cortex to medulla http: //research. surgery. wisc. ed u/southard/organs/kidney. gif

Nephron: basic urineproducing unit of kidney z. Each kidney contains about one million nephrons z. Spans cortex and medulla z. Sac with long tube leading to ureter http: //www. bbc. co. uk/scotland/education/bitesize/stand ard/img/biology/kidney_function 1. gif

Nephron consists of five parts: http: //www. bbc. co. uk/scotland/education/bitesize/stand ard/img/biology/kidney_function 1. gif

Nephron consists of five parts: z. Bowman’s capsule http: //www. bbc. co. uk/scotland/education/bitesize/stand ard/img/biology/kidney_function 1. gif

Nephron consists of five parts: z. Bowman’s capsule z. Proximal tubule http: //www. bbc. co. uk/scotland/education/bitesize/stand ard/img/biology/kidney_function 1. gif

Nephron consists of five parts: z. Bowman’s capsule z. Proximal tubule z. Loop of Henle http: //www. bbc. co. uk/scotland/education/bitesize/stand ard/img/biology/kidney_function 1. gif

Nephron consists of five parts: z. Bowman’s capsule z. Proximal tubule z. Loop of Henle y. Descending branch http: //www. bbc. co. uk/scotland/education/bitesize/stand ard/img/biology/kidney_function 1. gif

Nephron consists of five parts: z. Bowman’s capsule z. Proximal tubule z. Loop of Henle y. Descending branch y. Ascending branch http: //www. bbc. co. uk/scotland/education/bitesize/stand ard/img/biology/kidney_function 1. gif

Nephron consists of five parts: z. Bowman’s capsule z. Proximal tubule z. Loop of Henle y. Descending branch y. Ascending branch z. Distal tubule http: //www. bbc. co. uk/scotland/education/bitesize/stand ard/img/biology/kidney_function 1. gif

Also have collecting duct: z. Collects urine from distal tubule z. Passes through medulla z. Discharges to renal pelvis http: //www. bbc. co. uk/scotland/education/bitesize/stand ard/img/biology/kidney_function 1. gif

And blood vessels http: //www. bbc. co. uk/scotland/education/bitesize/stand ard/img/biology/kidney_function 1. gif

And blood vessels z. Afferent arteriole http: //www. bbc. co. uk/scotland/education/bitesize/stand ard/img/biology/kidney_function 1. gif

And blood vessels z. Afferent arteriole z. Glomerulus http: //www. bbc. co. uk/scotland/education/bitesize/stand ard/img/biology/kidney_function 1. gif

And blood vessels z. Afferent arteriole z. Glomerulus z. Efferent arteriole http: //www. bbc. co. uk/scotland/education/bitesize/stand ard/img/biology/kidney_function 1. gif

And blood vessels z. Afferent arteriole z. Glomerulus z. Efferent arteriole z. Peritubular capillaries http: //www. bbc. co. uk/scotland/education/bitesize/stand ard/img/biology/kidney_function 1. gif

Major processes of nephron z. Filtration z. Secretion z. Reabsorption z. Excretion http: //www. bbc. co. uk/scotland/education/bitesize/stand ard/img/biology/kidney_function 1. gif

At the glomerulus z Blood is filtered y 2000 L/day z Raw urine passes into capsule space y 180 L/day z Remaining blood flows into efferent arteriole http: //coe. fgcu. edu/faculty/greenep/kidney/glomer 3. jpg

At the proximal tubule z Useful molecules (sugars, amino acids, bicarbonate, potassium) are resorbed from filtrate into blood z Na+ is resorbed by active transport z Cl- and water follow passively z Urine is iso-osmotic to blood http: //renux. dmed. ac. uk/Ed. REN/makingi mages/Nephron. S. gif

Making hyperosmotic urine Concentrated

Making hyperosmotic urine Step 1 z In ascending branch, Na+ is resorbed by active transport z Cl- follows passively z Water stays behind z Urine becomes more dilute z Medulla tissue becomes more salty - giving gradient Cl. Na+ http: //renux. dmed. ac. uk/Ed. REN/makingi mages/Nephron. S. gif

Making hyperosmotic urine Step 2 z In descending branch, urine enters salty medulla z Water diffuses from tubule z Urine becomes more concentrated H 2 O http: //renux. dmed. ac. uk/Ed. REN/makingi mages/Nephron. S. gif

Making hyperosmotic urine Step 2 z In descending branch, urine enters salty medulla z Water diffuses from tubule z Urine becomes more concentrated H 2 O Opposite flow in loop of Henle magnifies saltiness in tissue, giving “Countercurrent Multiplier” effect.

Making hyperosmotic urine Step 3 z In distal tubule, urine is hypo-osmotic to blood z H+ and K+ are secreted into tubule z Urine becomes more acidic H+ K + http: //renux. dmed. ac. uk/Ed. REN/makingi mages/Nephron. S. gif

Making hyperosmotic urine Step 4 z In collecting duct, watery urine passes through salty medulla. z H 2 O leaves, assuming antidiuretic hormone (ADH) is present z Urine becomes more concentrated H 2 O http: //renux. dmed. ac. uk/Ed. REN/makingi mages/Nephron. S. gif

Making hyperosmotic urine Step 4 z In collecting duct, watery urine passes through salty medulla. z H 2 O leaves, assuming antidiuretic hormone (ADH) is present z Urine becomes more concentrated H 2 O Note: ADH allows us to retain water under normal circumstances

ADH may not be present z Excessively dilute urine or alcohol in blood cuts off flow of ADH from posterior pituitary z Collecting ducts do not resorb water z Watery urine leaves collecting duct http: //renux. dmed. ac. uk/Ed. REN/makingi mages/Nephron. S. gif

Finally z. Sodium concentrations and blood pressure are regulated by hormones aldosterone and atrial natriuretic hormones z. See P. 1035 -1036 of your text! http: //www. nlm. nih. gov/medlinep lus/images/saltshaker. jpg