Lec 14 Osmoregulation Flashcards
What is diffusion?
The movement of ions and molecles through a medium, from high concentration to low concentration
What is osmosis?
movement of water across semi permeable membrane. Concentration of solutes is greater on one side of the membrane than the other. Movement of water goes from less concentration to greater concentration of solutes.
What does osmotic equilibrium mean?
principal ions found in fluids that are in the body are the same concentration as those in seawater
What is an isotonic environment?
rate of diffusion of water into body is the same as the rate to which it diffuses out.
How did the primitive kidney function?
function to get rid of body waste materials. It was excretory in function rather than osmoregulatory.
What is the law of osmosis
any animal submerge in freshwater with body fluids in greater concentration than surrounding water inevitably take in excess water.
how does the early vertebrates that took to freshwater get waterlogged?
- Absorption through the epithelium covering the gill filaments and mucous membranes of mouth
- swallowing water along with food
What type of mechanism is needed for the Law of diffusion and osmosis in freshwater fishes?
Osmosis: to get rid of excess water
diffusion: mechanism to prevent loss of salts
Vertebrate kidney, eliminates excess water and reclaim salts
What is the vertebrate kidney made of?
Thousands of nephrons
Each nephron has three components, what are they?
- Glomerulus
- Convoluted or nephric tubule
- Longitudinal collecting duct
What is a glomerulus?
Tuft of blood capillaries surrounded by a capsule of tissue called bowman’s capsule.
What is the renal corpuscle?
The glomerulus and capsule.
What does the glomerulus do?
With help of blood pressure, functions to filter water and other fluid substances.
What are the filtered substances called?
Glomerular filtrate.
What does the convoluted tubule?
a duct that collects the glomerular filtrate from glomerulus and transports it to the longitudinal collecting duct.
Substances are reabsorbed by the bloody by means of a second capillary bed. What is it supplied by and drained by?
Supplied by afferent renal venule and drained by efferent renal venule.
What does the longitudinal collecting duct do?
Receives all of the glomerular filtrate from thousand of kidney tubules and dump it into the urinary bladder.
What are the two critical functions of each nephron?
- Glomerular mass, embedded in the bowman’s capsule. Acts as a filter to remove excess water and other substances
- reabsorptive mass surrounds the convoluted tubule and function to reabsorb water and other valuable substances, i.e salts.
What does it mean when an animal exists in hypotonic env?
There’s a higher water concentration in the fish compared to the env.
What do animals do when they exist in hypotonic env to balance itself?
- drinks very little water
- numberous large well developed glomeruli
- reabsorbs salts along the conoluted tubules
- produce large amounts of very dilute urine (5-12% of body weight a day)
Describe the glomerulus
a typical kidney of a freshwater fish that has tens of thousands of large glomeruli and well developed bloody supply. A lot of water passes through it and glomerulus provides a filtrate that can be modified by the kidney tubule.
Describe what the neck region is lined with
Lined with cilia, the ciliary action plays an important role in aiding movement of materials into the tubule. important in low pressure filtration systems of fishes.
What happens at the first proximal segment
reabsorption of many macromolecules, such as glucose and proteins, also excrete organic acids
What occurs at second proximal segment?
Largest region of the tubule, where there is a high metabolic activity, es active transport mechanisms that are reabsorption of many salts
