Lecture Outline for April 6, 2005


Topic: water balance in animals

Chapter 38 sections 38.2 through 38.5

Figures used in lecture: 38.7, 38.13, 38.14, 38.15, 38.16, 38.17, 38.18

Additional Resources

            The Kidney – anatomy and function

Human Excretory System


Water Balance in Animals

Define/explain: osmoregulation, osmotic stress, kidney, cortex, medulla, ureter, nephron, Bowman's capsule, proximal tubule, loop of Henle, distal tubule, collecting duct,


You should be able to:

1.  Discuss the ways in which water balance differs for fresh water aquatic animals, marine animals, and terrestrial animals.

2.  Discuss kidney function as an organ of osmoregulation in terrestrial animals.  This discussion should include the functions of the following components of the kidney:

            Bowman's capsule

            proximal tubule

            loop of Henle

            distal tubule

            collecting duct


Today’s Lecture (4-6-05)


Different Habitats Present Different Challenges

            freshwater organisms -


            marine organisms -


            terrestrial organisms -



Kidney Structure and Function

Renal artery –


Renal vein –




nephron -


Components of the nephron:

            Bowman’s capsule –



            proximal tubule


            loop of Henle


            distal tubule


            collecting duct –




Glomerular filtrate contains:


Proximal tubule is a recycling center



Control of Kidney Function

Control often involves hormones

Site of control = distal tubule and collecting duct


Control of kidney function During dehydration:




A question…

The filtrate leaving the Bowman’s capsule contains water, nutrients, and waste products.

The water and nutrients must be reabsorbed

Why not filter out the wastes only?