Chapter 44Chapter 44

Osmoregulation Osmoregulation and excretion and excretion

OsmoregulationOsmoregulation and and excretion excretion

Osmoregulation is the regulation of solute Osmoregulation is the regulation of solute particles and balancing water loss and gainparticles and balancing water loss and gain

Excretion is the removal of nitrogen Excretion is the removal of nitrogen containing waste from metabolismcontaining waste from metabolism

Osmoregulation and excretion are both Osmoregulation and excretion are both homeostatic processeshomeostatic processes

OsmolarityOsmolarity Osmoregulation functions based on the movement Osmoregulation functions based on the movement

of solute particles between internal fluids and of solute particles between internal fluids and external environmentexternal environment

Osmolarity continuedOsmolarity continued Osmolarity the concentration of solute in a Osmolarity the concentration of solute in a

solution (same as osmotic pressure solution (same as osmotic pressure o When the two solutions have the same When the two solutions have the same

osmolarity, the solutions are Isoosmotic osmolarity, the solutions are Isoosmotic o If the two concentrations are unequal the If the two concentrations are unequal the

greater concentration of solutes is greater concentration of solutes is hyperosmotichyperosmotic

o The more dilute concentration is The more dilute concentration is hypoosmotichypoosmotic

OsmoregulationOsmoregulation Animals that do not regulate their Animals that do not regulate their

internal osmolarity are osmoconformersinternal osmolarity are osmoconformers Occurs in animals that live in stable aquatic Occurs in animals that live in stable aquatic

environmentsenvironments Osmoregulators adjust their osmolarity to Osmoregulators adjust their osmolarity to

create a difference between membranescreate a difference between membranes Allows organism to live in diverse Allows organism to live in diverse

environment but costs energy to transport environment but costs energy to transport solutessolutes

Amount of energy expended depends on the Amount of energy expended depends on the solution the organism is immersed solution the organism is immersed

OsmoregulationOsmoregulation

Animals vary in the in change in external Animals vary in the in change in external molarity they can survive molarity they can survive animals that can not handle a large change in animals that can not handle a large change in

osmolarity are stenohalineosmolarity are stenohaline animals that are euryhaline can handle a large animals that are euryhaline can handle a large

change in osmolaritychange in osmolarity a common euryhaline example is salmona common euryhaline example is salmon

Adaptations of marine and Adaptations of marine and freshwater animalsfreshwater animals

Most marine animals are osmoregulatorsMost marine animals are osmoregulators Vertebrate Fish drink large amounts of water Vertebrate Fish drink large amounts of water

and uses gills to remove sodium chlorideand uses gills to remove sodium chloride Other minerals are moved through the kidneysOther minerals are moved through the kidneys

Cartilaginous fish, such as sharks, retain their Cartilaginous fish, such as sharks, retain their waste and are hyperosmoticwaste and are hyperosmotic

Freshwater fish are immersed in a Freshwater fish are immersed in a hypoosmotic environment and they excrete hypoosmotic environment and they excrete dilute urine to prevent salt lossdilute urine to prevent salt loss

AnhydrobiosisAnhydrobiosis A dormant state that A dormant state that

allows organisms to allows organisms to “hibernate” in extreme “hibernate” in extreme environments environments Sugars such as trehalose Sugars such as trehalose

allow for organisms to allow for organisms to survive with only 2% of survive with only 2% of water as their body masswater as their body mass

Land organism adaptations Land organism adaptations

Plants and animals utilize waxes to reduce Plants and animals utilize waxes to reduce dehydrationdehydration Camel’s fur helps insulate the body from heatCamel’s fur helps insulate the body from heat

Desert dwellers are nocturnalDesert dwellers are nocturnal Animals rely on drinking water and using Animals rely on drinking water and using

water generated from cellular respiration to water generated from cellular respiration to maintain homeostasismaintain homeostasis

Transport epitheliaTransport epithelia

Epithelial cells help regulate the movement of Epithelial cells help regulate the movement of solute particlessolute particles They may connect to the outside environment or They may connect to the outside environment or

form channels for regulation (albatross’s salt form channels for regulation (albatross’s salt glands).glands).

Waste managementWaste management

The digestion of macromolecules produces The digestion of macromolecules produces ammonia; a very toxic compoundammonia; a very toxic compound

Some animals excrete ammonia but most Some animals excrete ammonia but most expend energy to convert it to less toxic expend energy to convert it to less toxic compounds. compounds.

AmmoniaAmmonia

Requires the accompaniment of plenty of Requires the accompaniment of plenty of water when secretedwater when secreted

Aquatic species secrete ammonia through Aquatic species secrete ammonia through their entire body surfacetheir entire body surface

UreaUrea

Is 100,000 times less toxic than ammonia and Is 100,000 times less toxic than ammonia and requires less water when it is excretedrequires less water when it is excreted However, energy must be used to convert it to However, energy must be used to convert it to

ureaurea Mammals, most amphibians, sharks, some Mammals, most amphibians, sharks, some

marine bony fishes and turtles secrete ureamarine bony fishes and turtles secrete urea

Uric acidUric acid

Is insoluble in water and can be excreted as a Is insoluble in water and can be excreted as a semisolid semisolid Requires even more energy than urea to produceRequires even more energy than urea to produce

Insects, land snails, reptiles, and birds excrete Insects, land snails, reptiles, and birds excrete this wastethis waste

Evolutionary trends of waste removalEvolutionary trends of waste removal

Urea can diffuse out of shell-less eggs while Urea can diffuse out of shell-less eggs while the eggs of birds and reptiles use uric acid. the eggs of birds and reptiles use uric acid.

The type of waste produced also depends on The type of waste produced also depends on habitathabitat

Finally, the amount of waste excreted Finally, the amount of waste excreted depends on diet.depends on diet.

Excretory ProcessExcretory Process Filtration - movement of water and solutes

known as the filtrate across a selective permeable membrane.

Selective Reabsorption - reabsorption of valuable solutes from the filtrate.

Secretion – toxins and excess ions are extracted from body fluids and added to the excretory tube.

Excretion – filtrate is excreted from the body as urine.

Protonephridia: Flame-Bulb SystemsProtonephridia: Flame-Bulb Systems

Flatworms have an excretory system called Flatworms have an excretory system called Protonephridia , consisting of a branching Protonephridia , consisting of a branching network of dead-end tubules.network of dead-end tubules.

These are capped by a flame bulb that draws These are capped by a flame bulb that draws water and solutes from the interstitial fluid, water and solutes from the interstitial fluid, through the flame bulb, and into the tubule through the flame bulb, and into the tubule system.system.

The urine in the tubules exits through The urine in the tubules exits through openings called nephridiopores.openings called nephridiopores.

MetanephridiaMetanephridia

Consists of internal openings that collect body Consists of internal openings that collect body fluids from the coelom through a ciliated fluids from the coelom through a ciliated funnel, the nephrostome, and release the funnel, the nephrostome, and release the fluid to the outside through the fluid to the outside through the nephridiopore. nephridiopore.

Malpighian TubesMalpighian Tubes

Insects and other terrestrial arthropods have Insects and other terrestrial arthropods have organs called Malpighian tubules.organs called Malpighian tubules.

These open into the digestive system and These open into the digestive system and dead-end at tips that are immersed in the dead-end at tips that are immersed in the hemolymph. hemolymph.

This system is highly effective in conserving This system is highly effective in conserving water and is one of several key adaptations water and is one of several key adaptations contributing to the tremendous success of contributing to the tremendous success of insects on land. insects on land.

Vertebrate KidneysVertebrate Kidneys The kidneys of vertebrates usually function in The kidneys of vertebrates usually function in

both osmoregulation and excretion.both osmoregulation and excretion. the kidneys of most vertebrates are compact, the kidneys of most vertebrates are compact,

nonsegmented organs containing numerous nonsegmented organs containing numerous tubules arranged in a highly organized manner. tubules arranged in a highly organized manner.

The vertebrate excretory system includes a The vertebrate excretory system includes a dense network of capillaries intimately dense network of capillaries intimately associated with the tubules, along with ducts and associated with the tubules, along with ducts and other structures that carry urine out of the other structures that carry urine out of the tubules and kidney and eventually out of the tubules and kidney and eventually out of the body.body.

Function of the Mammalian KidneyFunction of the Mammalian Kidney

renal artery – supplies kidney with bloodrenal artery – supplies kidney with blood renal vein – drains blood supply from kidneyrenal vein – drains blood supply from kidney urine exits kidney through duct called ureter, urine exits kidney through duct called ureter,

drains into the urinary bladder, and exits the drains into the urinary bladder, and exits the body through the urethra. body through the urethra.

Regions of the NephronRegions of the Nephron

There are two regions, the renal cortex and There are two regions, the renal cortex and the renal medulla.the renal medulla.

The nephron consists of a single long tubule The nephron consists of a single long tubule and ball of capillaries called the glomerous.and ball of capillaries called the glomerous.

Bowmans capsule surrounds the glomerous.Bowmans capsule surrounds the glomerous.

Path of the FiltratePath of the Filtrate

From Bowmans capsule goes through three From Bowmans capsule goes through three regionsregions

Proximal tube- reabsorption of bicarbonate Proximal tube- reabsorption of bicarbonate ions helps regulate the bloods pH. Solutes ions helps regulate the bloods pH. Solutes actively transport out of the filtrate leaving it actively transport out of the filtrate leaving it more dilute causing water to follow by more dilute causing water to follow by osmosis. This water and filtrate reenter the osmosis. This water and filtrate reenter the blood.blood.

Path of the Filtrate Cont.Path of the Filtrate Cont.

Loop of Henle – concentration of solutes Loop of Henle – concentration of solutes increases, water reabsorbed into blood. In the increases, water reabsorbed into blood. In the ascending loop the surrounding fluid becomes ascending loop the surrounding fluid becomes more dilute. Water can not pass through but more dilute. Water can not pass through but sodium chloride can. Sodium chloride diffuses sodium chloride can. Sodium chloride diffuses out, further diluting filtrate.out, further diluting filtrate.

Path of the Filtrate Cont.Path of the Filtrate Cont.

Distal tube – Substances are reabsorbed Distal tube – Substances are reabsorbed including bicarbonate ions from the distal including bicarbonate ions from the distal tube to regulate body pH. Hydrogen ions and tube to regulate body pH. Hydrogen ions and other toxins are secreted into the filtrate to other toxins are secreted into the filtrate to further adjust the body’s pH. further adjust the body’s pH.

The distal tube empties into collecting duct The distal tube empties into collecting duct which is drained into renal pelvis where it is which is drained into renal pelvis where it is drained by the ureter.drained by the ureter.

Path of the Filtrate Cont.Path of the Filtrate Cont.

Cortical nephrons make up 80% of the Cortical nephrons make up 80% of the nephrons in the human kidney. They have nephrons in the human kidney. They have reduced loops and are confined to the renal reduced loops and are confined to the renal cortex. cortex.

Path of the Filtrate Cont.Path of the Filtrate Cont.

Juxtamedullary nephrons have well developed Juxtamedullary nephrons have well developed loops that extent deep into the renal medulla. loops that extent deep into the renal medulla. Only mammals and vertebrates have these. Only mammals and vertebrates have these. The nephrons of other vertebrates lack loops The nephrons of other vertebrates lack loops of Henle. These nephrons allow mammals to of Henle. These nephrons allow mammals to produce urine that is hyperosmotic to body produce urine that is hyperosmotic to body fluids, an adaptation that is important for fluids, an adaptation that is important for water conservation.water conservation.

Blood Vessels Associated with the Blood Vessels Associated with the NephronNephron

Afferent arterioles supply each nephron with Afferent arterioles supply each nephron with blood.blood.

Capillaries converge forming efferent Capillaries converge forming efferent arteriole.arteriole.

Vessel subdivides again, forming the Vessel subdivides again, forming the peritubular capillaries, which surround the peritubular capillaries, which surround the proximal and distal tubules.proximal and distal tubules.

Vasa recta are the capillaries that serve the Vasa recta are the capillaries that serve the loop of Henle.loop of Henle.

Water Conservation by Water Conservation by KidneyKidney

The osmolarity of the urine excreted The osmolarity of the urine excreted by the kidney is up to 4 times as by the kidney is up to 4 times as concentrated as the osmolarity of concentrated as the osmolarity of human blood. human blood.

How is this possible?How is this possible? The loops of henle is greatly The loops of henle is greatly

responsible for the osmotic responsible for the osmotic gradient that concentrates urine. gradient that concentrates urine.

Loops of Henle produce regions of high Loops of Henle produce regions of high osmolarity in the kidney, allowing osmolarity in the kidney, allowing water to be extracted by the filtrate.water to be extracted by the filtrate.

Figure 44.15 Figure 44.15 Descending limb: Produces a saltier filtrateDescending limb: Produces a saltier filtrate Ascending limb: Allows for diffusion of Ascending limb: Allows for diffusion of

NaCl to maintain high osmolarity of kidney.NaCl to maintain high osmolarity of kidney. Descending and Ascending limbs work Descending and Ascending limbs work

together to maintain gradient of together to maintain gradient of osmolarity.osmolarity.

Water Conservation by Water Conservation by Kidney (cont’d)Kidney (cont’d)

Loop of Henle as Loop of Henle as Countercurrent Multiplier Countercurrent Multiplier

SystemSystem Since energy must be used to Since energy must be used to

transport the NaCl from the filtrate transport the NaCl from the filtrate in the upper part of the ascending in the upper part of the ascending limb of the loop, the loop of Henle is limb of the loop, the loop of Henle is known as a countercurrent known as a countercurrent multiplier system.multiplier system.

Helps maintain osmotic gradient Helps maintain osmotic gradient between the medulla and cortex. between the medulla and cortex.

Regulation of Kidney Regulation of Kidney FunctionFunction

Antidiueretic hormone (ADH)Antidiueretic hormone (ADH) Renin-angiotensin-aldosterone Renin-angiotensin-aldosterone

system (RAAS)system (RAAS) Atrial natriuretic factor (ANF)Atrial natriuretic factor (ANF)

Antidiueretic hormone Antidiueretic hormone (ADH)(ADH)

Produced in hypothalamus of the brain, Produced in hypothalamus of the brain, stored and released from posterior stored and released from posterior pituitary gland.pituitary gland.

When osmolarity of blood rises above 300 When osmolarity of blood rises above 300 mosm/L, more ADH is released into the mosm/L, more ADH is released into the bloodstream, amplifying water absorption bloodstream, amplifying water absorption by increasing the permeability of the by increasing the permeability of the epithelium.epithelium.

Uptake of additional water is still needed Uptake of additional water is still needed to improve osmolarity. to improve osmolarity.

Juxtaglomerular Juxtaglomerular apparatus (JGA)apparatus (JGA)

A type of tissue that supplies blood to the A type of tissue that supplies blood to the glomerulus.glomerulus.

Used when blood pressure or blood volume in Used when blood pressure or blood volume in the arteriole drops.the arteriole drops.

The peptide angiotensin II (formed by renin) The peptide angiotensin II (formed by renin) functions as a hormone and raises blood functions as a hormone and raises blood pressure by constricting the arterioles. pressure by constricting the arterioles. Leads to the release of aldesterone which makes Leads to the release of aldesterone which makes

the nephons’ distal tubules reabsorb more water the nephons’ distal tubules reabsorb more water and sodium, increasing blood volume and pressure.and sodium, increasing blood volume and pressure.

All together known as renin-angiotensin-All together known as renin-angiotensin-aldosterone system (RAAS).aldosterone system (RAAS).

Atrial natriuretic factor Atrial natriuretic factor (ANF)(ANF)

A peptide that opposes the RAAS A peptide that opposes the RAAS and decreases blood pressure by and decreases blood pressure by inhibiting release of renin.inhibiting release of renin.

Examples of Environmental Examples of Environmental Adaptations of the Adaptations of the Vertebrate KidneyVertebrate Kidney

Mammals excrete very hyperosmotic urine Mammals excrete very hyperosmotic urine so they have longer loops of henle. so they have longer loops of henle.

Birds and other reptiles have uric acid as Birds and other reptiles have uric acid as the nitrogen waste molecule, which can be the nitrogen waste molecule, which can be excreted as a paste, reducing urine volume.excreted as a paste, reducing urine volume.

Amphibians can reabsorb water across the Amphibians can reabsorb water across the epithelium of the urinary bladder.epithelium of the urinary bladder.

Marine bony fishes excrete little urine, so Marine bony fishes excrete little urine, so they must get rid of double charged ions by they must get rid of double charged ions by excreting them with urine. excreting them with urine.