Osmoregulation

chapter 48

what are the 4 main body fluids

intracellular: most of body fluid

extracellular: interstitial fluid, lymph, and blood plasma

interstitial: forms from blood plasma and bathes all cells

plasma: transport nutrients, gases, waste products, and other materials

how does body fliud vary with age

infants have the highest percentage; elderly have the lowest

what holds a large amount of water

muscle tissue
skeletal muscle 75%

loss off skeletal muscle mass often occurs with.

aging

electrolyte function

forms ions in solution

electrolyte example

Na+, Cl-, K+

osmosis

diffusion of water through selectively permeable membranes

osmotic pressure

pressure exerted on the hypertonic side of membrane to prevent net movement of water from hypertonic side

osmolarity

number of osmoles of solute per liter of solution
-number of particles produced when a solute dissolve

example of osmolarity

-a mole of NaCl (2 osmoles) in a solution produces a mole of Na+ and a mole of Cl-

-both ions affect osmotic pressures of solution

Osmoregulation

organisms control concentration of water, salts (ions), and metabolites in solutions to maintain homeostasis levels

what does osmoregulation require to occur

active regulation of osmotic pressures

example of metabolites

glucose, vitamins, amino acids

function of excretory system

remove and regulate metabolic waste including water, CO2, and nitrogenous compounds

Major excretory waste products

ammonia, urea, uric acid

what is Nitrogenous waste a result of?

protein breakdown and are excreted or reabsorbed

Ammonia nitrogenous waste

habitat: live in or have access to water

toxicity: highly toxic and disrupts pH and chemical reactions

Animals: all animal groups

Urea nitrogenous waste

Habitat: living in or having access to water

Toxicity: less toxic than ammonia, requires less water for excretion

Animals: all major animal groups (some terrestrial planarians & mammals)

Uric Acid

Habitat: limited or no access to water (could be terrestrial dwellers or shelled embryos)

Toxicity: very little, excreted as semisolid paste, almost no water required

Animals: reptiles, birds, frogs, insects
cockroaches-recycle nitrogen source when low protein diet
gout-build up in joints

what is the relationship between nitrogenous wastes

ammonia urea uric acid
More E to Produce —-—————————→
←————————--More water needed to excrete

Osmoconformer

Isosmotic (solute/liter) with environment

Animals using Osmoconformer osmoregulation

mainly marine invertebrates

Osmoregulator

maintain water and or ionic balance independent of environment

animals using Osmoregulator osmoregulation

Some marine invertebrates (costal
vertebrates

what are the main functions of osmoregulatory and excretory structures in invertebrates?

Osmoregulation and excretion-regulating water and solute balance and removing nitrogenous waste

what are nephridiopores

surface openings through which waste exits from nephridial tubules

what type of excretory structure is used by protists

contractile vacuole

what does contractile vacuole do

collects and expels excess water by contraction to maintain osmotic balance

what invertebrate group uses renette cells for osmoregulation

nematodes

what are Renette cells

specialized excretory cells in nematodes; may include associated tubules to help eliminate waste

which animals have protonephridia

acoelomates and some coelomates like flatworms (Platyhelminthes) and some annelids

what is the basic structure of protonephridia

branching tubules connected to flame cells

what are flame cells

specialized cells with cilia that draw interstitial fluid into the tubules

what is the role of cilia in flame cells

they create currents that pull fluid into the tubules

where does fluid exit in protonephridia

through nephridiopores

what is the composition of urine in protonephridia

often ypoosmotic but can be modified

how do most nitrogenous wastes exit in animals with protonephridia

across the body surface

which animals use metanephridia

coelomates like most annelids, mollusks and crustaceans

how do metanephridia differ from protonephridia

they are open at both ends and use a funnel-like opening

what is the role of the funnel cell in metanephridia d

draws fluid from the coelom into the tubule

how is fluid moved in metanephridia

cilia push fluid through tubules; solutes are reabsorbed or secreted

where does urine exit in metanephridia

through nephridiophores

what is the composition of urine in metanephridia

can be hypertonic and is modifiable by surrounding capillaries

how is the fluid modified in malpighian tubules

as it passes through the tubule and rectum, useful solutes and water are reabsorbed

where are Malpighian tubules located

they extend from the gut wall into the body cavity (interstitial space)

what is the function of Malpighian tubules

active transport of ions and uric acid into the tubule; water follows by osmosis

where does the modified fluid empty

Into the gut for final modification and excretion.

What can the urine from Malpighian tubules be?

Hypoosmotic, isosmotic, or hyperosmotic—depending on water conservation needs.

What animals use antennal glands?

Crustaceans (e.g., crayfish).

What is the function of antennal glands?

Remove excess water and ions from the blood; involved in osmoregulation and excretion.

What is the role of salt glands?

Excrete excess salt from the body, especially in marine animals.

What is an example of an animal with salt glands?

Marine birds and reptiles.

What is the main osmoregulatory and excretory organ in most vertebrates?

The kidney.

What are the two main roles of kidneys in vertebrates?

Excreting nitrogenous waste and regulating salt/water balance in urine.

What other structures help excrete waste in vertebrates besides the kidney?

Gills, skin, and specialized salt glands (in some species).

Are freshwater fish hypertonic or hypotonic to their environment?

Hypertonic—body fluids have more solutes than the surrounding water.

What do freshwater fish kidneys look like?

Large glomeruli that produce large amounts of dilute urine.

How much nitrogenous waste is excreted via urine in freshwater fish?

About 10%; the rest is excreted by gills.

How do gills assist in osmoregulation in freshwater fish?

Special gill cells actively transport salts into the body from the environment.

Do freshwater fish drink water?

No

Does water tend to enter or exit the body of freshwater fish?

Enters passively due to osmosis.

Are saltwater bony fish hypertonic or hypotonic to seawater?

Hypotonic—body fluids have fewer solutes than the seawater.

How do marine bony fish osmoregulate with their kidneys?

They have small or absent glomeruli and excrete very little urine.

How do gills help marine fish osmoregulate?

Gills excrete ammonia and excess salts.

Do saltwater bony fish drink water?

Yes—they drink seawater to compensate for water loss.

Does water tend to enter or leave the body of saltwater fish?

Leaves passively due to osmosis.

How do cartilaginous fish maintain osmotic balance?

They accumulate urea in tissues, making their body fluids hypertonic to seawater.

How do the kidneys function in cartilaginous fish?

Well-developed; excrete large volumes of dilute (hypotonic) urine.

Do cartilaginous fish drink seawater?

Some do with food, but not as much as bony saltwater fish.

Does water tend to move into or out of cartilaginous fish?

Into the body (due to their hypertonic fluids).

How do saltwater-drinking vertebrates manage excess salt?

They use salt glands to remove excess salt from the blood without losing water.

Where are salt glands located in marine birds and reptiles?

Near the eyes, nose, or tongue, depending on the species.

What do salt glands excrete?

Concentrated salt solutions.

How do marine mammals regulate salt and water balance?

By producing highly concentrated urine through efficient kidney function.

Why do marine mammals excrete so much urea?

Their high-protein diet generates large amounts of nitrogenous waste.

How do marine mammals conserve water while excreting urea?

Their kidneys concentrate urine to remove waste without excessive water loss.

What are the main structures of the human urinary system?

Kidneys, ureters, urinary bladder, and urethra.

What is the function of the kidneys?

To filter blood, remove waste, and produce urine.

Where is urine produced?

In the kidneys.

What is the pathway of urine from production to exit?

Kidneys → Ureters → Urinary bladder → Urethra → Out of body.

How many kidneys do humans have?

Two.

What do the kidneys regulate besides waste?

Water balance, salt levels, blood pressure, and pH.

What tube carries urine from each kidney to the bladder?

The ureter.

What is the role of the ureters?

Carry urine from the kidneys to the urinary bladder.

How does urine move through the ureters?

By peristalsis (wave-like muscle contractions).

What is the function of the urinary bladder?

To store urine until urination.

Is the bladder under voluntary or involuntary control?

Both: smooth muscle (involuntary) and external sphincter (voluntary).

What is the function of the urethra?

Carries urine from the bladder to the outside of the body during urination.

How does the urethra differ between males and females?

• Males: Longer urethra; shared with reproductive system.

• Females: Shorter urethra; only for urinary function.

What is the medical relevance of urethra length in females?

Shorter urethra increases risk of urinary tract infections (UTIs).

What is the functional unit of the kidney?

The nephron.

What are the two major parts of the nephron?

The renal corpuscle and the renal tubule.

What structures make up the renal corpuscle?

The Bowman's capsule and the glomerulus.

What is the Bowman's capsule?

A cup-shaped structure that surrounds the glomerulus and collects filtrate.

What is the glomerulus?

A cluster of fenestrated capillaries where blood filtration begins

Where are all glomeruli located?

In the renal cortex.

What are podocytes?

Specialized cells that surround the glomerular capillaries and help with filtration.

What are the main regions of the renal tubule?

• Proximal convoluted tubule (PCT)

• Loop of Henle (nephron loop)

• Distal convoluted tubule (DCT)

What is the function of the proximal tubule?

Reabsorption of water, ions, and nutrients back into the blood.

What happens in the loop of Henle?

Water and salt are reabsorbed to help concentrate urine.