Transcript AP excretory

Regulating the Internal
Environment
Animals need to regulate:
1.
Water/solute concentration of body fluids
– Body fluids-total amount of fluids in the body
• Intracellular-amount of fluids found inside the cells, blood
cells, and other tissue
• Extracellular-amount of fluids found outside of the cells
– Plasma-extracellular fluids found in the circulatory
system
– Interstitial fluid-fluids found between the cells outside
the circulatory system
2.
3.
pH
temperature
• The excretory system is a regulatory system that
helps to maintain homeostasis within the body
• Homeostasis is the dynamic constancy of the
internal environment
• The excretory system eliminates wastes and
functions in osmoregulation.
• Osmoregulation is the control of salt and water
balance
• Osmoconformers
– Do not actively adjust their internal osmolarity
• Osmoregulators
– Animals whose body fluids are not isotonic with
the external environment must manipulate solute
concentrations in their body fluids
Osmoregulation involves:
1. Osmosis-diffusion of H2O across a
membrane due to a concentration
gradient
• remember, hyper/hypo/isotonic
2. Excretion- process of an organism
ridding their bodies of metabolic wastes.
This process also helps regulate Salt
Balance.
Animals have to get rid of
nitrogen
• The metabolism of proteins and nucleic acids
produces toxic by-products
ammonia
• Ammonia:
– a small and very toxic molecule
– can be transported and excreted only in a
very dilute solution
• Many animals convert ammonia to urea
(mammals and amphibians) or uric acid (birds
and reptiles), which are much less toxic, but
require ATP to produce
Maintaining Extracellular Fluid
• Urinary/Excretory system:
– keeps volume and composition of
extracellular fluid within tolerable ranges
– regulates solute movement between
internal fluids and the external
environment
• interacts with the digestive, respiratory, and
circulatory systems to fulfill these tasks
Urinary System Interactions
food, water intake
oxygen intake
DIGESTIVE
SYSTEM
nutrients,
water,
salts
RESPIRATORY
SYSTEM
oxygen
elimination
of carbon
dioxide
carbon
dioxide
CIRCULATORY
SYSTEM
URINARY
SYSTEM
water,
solutes
elimination
of food
residues
rapid transport
to and from all
living cells
elimination of
excess water,
salts, wastes
Aquatic animals:
-excrete ammonia which can readily cross
membranes and then be flushed from the
body
1. Many Marine invertebrates - lack a
specialized excretory system, most waste
diffuses across a membrane. The sea is an
isotonic solution so salt balance is no problem
EXCEPT if the organism is put in fresh water
or a hypotonic solution. The animal most
likely will lose salts and fluids and die
2. Marine fish - their body fluids are diluted
(or hypotonic) in comparison to their
environment (sea water)
-Marine fish tend to lose water to their
environment
-Compensation
1. Marine fish drink water to replace H2O loss
2. Gills secrete ammonia not urine
Gain of water and
salt ions from food
and by drinking
seawater
Excretion of
salt ions
from gills
Osmotic water loss
through gills and other parts
of body surface
Excretion of salt ions
and small amounts
of water in scanty
urine from kidneys
Osmoregulation in a saltwater fish
3. Fresh water fish – their body fluids are
concentrated (or hypertonic) in
comparison to their environment
- Fresh water fish tend to gain water from
their environment
- Compensation
- almost never drink H2O
- Fish excrete a dilute urine, therefore
keeping more salts in the body
Osmotic water gain
through gills and other parts
of body surface
Uptake of
water and some
ions in food
Uptake of
salt ions
by gills
Osmoregulation in a freshwater fish
Excretion of
large amounts of
water in dilute
urine from kidneys
Terrestrial animals:
**must fight desiccation (drying out)
-compensation
1. drinking H2O
2. food with H2O
3. H2O is a by product respiration
-Mammal and amphibians form Urea
and finally urine
-Birds and reptile form uric acid which is
insoluble and less H2O is needed for
excretion. Also will not toxify embyos in
eggs.
Proteins
Nucleic acids
Amino acids
Nitrogenous bases
—NH2
Amino groups
Most aquatic
animals,
including most
bony fishes
Ammonia
Mammals, most
amphibians,
sharks, some bony
fishes
Urea
Many reptiles
(including
birds), insects,
land snails
Uric acid
Ammonia
• Animals that excrete nitrogenous wastes as
ammonia need lots of water
• They release ammonia across the whole
body surface or through gills
Urea
• The liver of mammals and most adult
amphibians converts ammonia to less toxic
urea
• The circulatory system carries urea to the
kidneys, where it is excreted
Uric Acid
• Insects, land snails, and many reptiles,
including birds, mainly excrete uric acid
• Uric acid is largely insoluble in water and
can be secreted as a paste with little water
loss
Excretory Processes
• Most excretory systems produce urine by
refining a filtrate derived from body fluids
• Key functions of most excretory systems:
– Filtration: pressure-filtering of body fluids
– Reabsorption: reclaiming valuable solutes
– Secretion: adding toxins and other solutes from
the body fluids to the filtrate
– Excretion: removing the filtrate from the system
Protonephridia: Flame-Cell
Systems - flatworms
• A protonephridium is a network of dead-end
tubules lacking internal openings
• The smallest branches of the network are
capped by a cellular unit called a flame bulb
• These tubules excrete a dilute fluid and
function in osmoregulation
LE 44-10
Nucleus
of cap cell
Cilia
Interstitial fluid
filters through
membrane where
cap cell and tubule
cell interdigitate
(interlock)
Tubule cell
Flame
bulb
Protonephridia
(tubules)
Tubule
Nephridiopore
in body wall
Metanephridia
• Each segment of an earthworm has a pair of
open-ended metanephridia
• Metanephridia consist of tubules that collect
coelomic fluid and produce dilute urine for
excretion
LE 44-11
Coelom
Capillary
network
Bladder
Collecting
tubule
Nephridiopore
Nephrostome
Metanephridium
Malpighian Tubules
• In insects and other terrestrial arthropods,
Malpighian tubules remove nitrogenous
wastes from hemolymph and function in
osmoregulation
• Insects produce a relatively dry waste
matter, an important adaptation to terrestrial
life
LE 44-12
Digestive tract
Rectum
Hindgut
Intestine
Midgut
(stomach)
Malpighian
tubules
Feces and urine
Salt, water, and
nitrogenous
wastes
Anus
Malpighian
tubule
Rectum
Reabsorption of H2O,
ions, and valuable
organic molecules
HEMOLYMPH
The Vertebrate Excretory System
• Kidneys (function in both excretion and
osmoregulation), ureters, urinary
bladder, urethra, renal artery, renal vein
• Also…
– Lungs: excrete carbon dioxide
– Skin: excretes water, salts, and a small
amount of urea (in sweat)
Water Gains and Losses
Water Gains
• Absorption from
gut
• Metabolism
Water Losses
• Urination
• Cell secretions
• Sweating
• Water in feces
Solute Gains and Losses
Solute Gains
• Absorption from
gut
Solute Losses
• Urinary
excretion
• Cell secretions
• Respiration
• Respiration
• Sweating
• Metabolism
Controlling Water Gain & Loss
• Urinary excretion provides the
most control over water loss
• Concentration of urine can be
varied
Components of
Urinary System
• Pair of kidneys
• Pair of ureters
• Urinary bladder
• Urethra
• Anytime you see the
terms “nephr” or renal
it has something to do
with the kidneys
Urinary Excretion
• Urine flows from each kidney to a ureter
• Ureters deliver urine to bladder
• Contraction of the smooth muscle of the
bladder forces urine out of the body into the
urethra
• Skeletal muscle surrounds urethra; allows
voluntary control of urination
Function of Kidneys
• Filter water, mineral ions, wastes from
the blood
• Adjust filtrate concentration and return
most to blood
• Remaining water and solutes in filtrate
constitute urine
Structure of Kidney
• Renal capsule
surrounds kidney
• Two regions
– Outer renal cortex
– Inner renal medulla
• Renal pelvis collects
urine and funnels it to
ureter
Figure 42.4a
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Posterior vena cava
Renal artery and vein
Kidney
Renal
medulla
Renal
cortex
Renal
pelvis
Aorta
Ureter
Urinary bladder
Urethra
Ureter
Excretory organs and
major associated blood
vessels
JuxtaCortical
medullary nephron
nephron
Afferent
arteriole
Glomerulus
from renal
Bowman’s capsule
artery
Proximal tubule
Peritubular capillaries
Renal
cortex
Collecting
duct
20 µm
Renal
medulla
To
renal
pelvis
Nephron
Section of kidney from a rat
Kidney structure
SEM
Efferent
arteriole from
glomerulus
Distal
tubule
Branch of
renal vein
Descending
Loop limb
of
Henle Ascending
limb
Collecting
duct
Vasa
recta
Filtrate and blood flow
Nephron
• Functional unit of
the kidney
Bowman’s
capsule
(red)
distal
tubule
• Each consists of
a renal tubule and
associated
collecting
duct
proximal
tubule
loop of
Henle
capillaries
Figure 42.4c
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Humans - There are over 1,000,000 nephrons
in each kidney. 1,100-1,200 L of blood flows
through the kidneys each day.
-blood is delivered via an efferent arteriole to a
capillary bed called the glomerulus.
-The blood leaves the glomerulus via the
afferent arteriole forming a second capillary bed
called the peritubular capillaries that surrounds
the nephron. --The blood then leaves the
nephron via the a venule.
-
Urine Formation
Hormone
action
Filtration
Tubular
secretion
Tubular
reabsorption
Excretion
Figure 42.5
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Leaky Glomerular Capillaries
• Glomerular capillaries
have large pores
• Fluid leaks from
glomerular capillaries
into kidney tubules
Renal corpuscle
(Bowman’s capsule + glomerular capillaries)
Figure 42.5
Page 748
Filtration Rate Varies
• Increased blood pressure increases
glomerular filtration
• Flow volume to kidneys changes in
response to neural, endocrine, and local
changes
Most Filtrate Is Reabsorbed
• Each day, about 180
liters of filtrate flows out
of glomerulus into
tubules
• 1 to 2 liters excreted
• Most filtrate is
reabsorbed into blood
peritubular
capillaries
Tubular Reabsorption
• Ions move from the filtrate in tubule
lumen into the interstitial fluid
• Sodium ions are actively pumped out of
the proximal tubule into the interstitial
fluid
• Chloride ions follow; they are passively
transported
Tubular Reabsorption
• Ion flow creates an osmotic gradient; it
is saltier outside the tubule than inside
• Water flows down the osmotic gradient,
from the tubule lumen into the interstitial
fluid
• Peritubular capillaries pick up the water
and ions from the interstitial fluid
Amino acids, vitamins, proteins, and
glucose are reabsorbed in the PCT.
Tubular Reabsorption
interstitial fluid
filtrate in tubule
Na+
Na+
Na+
Cl-
Na+
Na+
Na+
H2O
peritubular
capillary
sodium pump
Figure 42.6
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Tubular Secretion
• The opposite of reabsorption
• Molecules are transported out of the
peritubular capillaries, through tubule
cells, and into the filtrate
• Eliminates H+ ions, metabolites, and
toxins
Proximal tubule
NaCl Nutrients
HCO3–
K+
H2O
H+
NH3
Distal tubule
H2O
NaCl
K+
HCO3–
H+
CORTEX
Descending limb
of loop of
Henle
Filtrate
H2O
Salts (NaCl and others)
HCO3–
H+
Urea
Glucose; amino acids
Some drugs
Thick segment
of ascending
limb
NaCl
H2O
OUTER
MEDULLA
NaCl
Thin segment
of ascending
limb
Key
Collecting
duct
Urea
NaCl
Active transport
Passive transport
INNER
MEDULLA
H2O
Osmolarity of
interstitial
fluid
(mosm/L)
300
300
100
300
100
CORTEX
Active
transport
H2O
H2O
NaCl
400
NaCl
300
300
400
400
H2O
200
H2O
Passive
transport
OUTER
MEDULLA
H2O
NaCl
H2O
NaCl
H2O
INNER
MEDULLA
H2O
400
600
H2O
H2O
NaCl
900
NaCl
NaCl
H2O
600
H2O
Urea
700
H2O
Urea
900
H2O
Urea
1200
1200
600
1200
Urine Formation
Hormone
action
Filtration
Tubular
secretion
Tubular
reabsorption
Excretion
Figure 42.5
Page 748
• http://www.biologymad.com/resources/kidney.swf
Regulation of Kidney Function
• The osmolarity of the urine is regulated by
nervous and hormonal control of water and
salt reabsorption in the kidneys
Hormones:
1.Antidiuretic hormone (ADH) increases water
reabsorption in the distal tubules and
collecting ducts of the kidney making urine
more concentrated and conserving water
– Acts on collecting ducts; makes walls more
permeable to water
Osmoreceptors
in hypothalamus
Thirst
Hypothalamus
Drinking reduces
blood osmolarity
to set point
ADH
Increased
permeability
Pituitary
gland
Distal
tubule
STIMULUS
The release of ADH is
triggered when osmoreceptor cells in the
hypothalamus detect an
increase in the osmolarity
of the blood
H2O reabsorption helps
prevent further
osmolarity
increase
Collecting duct
Homeostasis:
Blood osmolarity
2. The renin-angiotensin-aldosterone system (RAAS)
is part of a complex feedback circuit that functions
in homeostasis controlling blood pressure and
volume
•
If low blood volume or low blood pressure:
a) Aldosterone - Stimulates reabsorption of sodium
(H2O follows) in the Distal Convoluted Tubule ,
increasing blood volume and therefore pressure
b) Kidneys can also secrete an enzyme (resin)
which is converted to Angiotensin which helps
control blood pressure by causing arterioles to
constrict
Homeostasis:
Blood pressure,
volume
Increased Na+
and H2O reabsorption in
distal tubules
STIMULUS:
The juxtaglomerular
apparatus (JGA) responds
to low blood volume or
blood pressure (such as
due to dehydration or
loss of blood)
Aldosterone
Arteriole
constriction
Adrenal gland
Angiotensin II
Distal
tubule
Angiotensinogen
JGA
Renin
production
Renin
Thirst
• Osmoreceptors detect changes
• Activate thirst center in hypothalamus
and ADH-secreting cells
• Angiotensin II acts on brain to promote
thirst and ADH secretion
3. Another hormone, atrial natriuretic factor
(ANF), opposes the RAAS
• The walls of the atria of the heart release
ANF in response to increase in blood
volume and pressure.
• ANF inhibits the release of rennin from the
JGA and inhibits NaCl reabsorption by the
collecting ducts
Variation in Urinary Systems
• Structure of vertebrate urinary systems
varies in details
• Adapted to particular habitats
• Freshwater fish must deal with
continuous influx of water by osmosis
• Marine fish must deal with continuous
loss of water
Length of Loop of Henle
• Longer loop of Henle allows an organism to
produce a very steep osmotic gradient and the
more water that is conserved or retained by the
body
• Kangaroo rats have very long loops of Henle.
Kidney Disorders
• Glomerulonephritis
– Infection of glomeruli leads to chronic
inflammation that damages kidney
• Kidney stones
– Uric acid and calcium salts settle out of
urine, form hard deposits that can lodge in
ureter or urethra
Renal Failure
• Both kidneys are damaged to the point
where they are nonfunctional
• Fatal if not treated
• Dialysis is used to restore normal solute
balances temporarily
• Transplant is only way to fully restore
function
Acid-Base Balance
• Kidneys work in concert with
buffering systems to keep pH in
normal range
• Normal range is 7.37 to 7.43
• Normal metabolism produces an
excess of H+
Buffer Systems
• Weak acid and weak base that can
reversibly bind and release ions
• Bicarbonate-carbon dioxide buffer
system can neutralize excess H+
Regulating Blood pH (1)
• Involves secretion of H+ and
reabsorption of HCO3- (bicarbonate)
• HCO3- in filtrate combines with H+ to
form carbonic acid (H2CO3)
• H2CO3 becomes CO2 and H2O, which
are reabsorbed into blood from filtrate
Regulating Blood pH (2)
• In blood, HCO3 dissociates to form
HCO3- and H+
• The H+ can be secreted into proximal
tubule, while the HCO3- remains in
blood, thus increasing blood pH
• H+ can also combine with K+ or
ammonia and leave body in urine
Core Temperature
• Internal temperature of an animal’s body
• Must be maintained within a narrow
range for normal enzyme function
– Human body temp is 37C or 98.6F on
average
• Heat gains and losses must be kept in
balance
THERMOREGULATION
• Thermoregulation – homeostatic process
where body temperature is maintained
• VASOCONSTRICTION & VASODILATION
– making blood vessels smaller or larger to
shunt blood to areas of the body
ENDOTHERM METHODS
• Shivering – involuntary muscle contraction
that generates heat
• Goose bumps – muscles at base of hairs
raise hairs off of skin creating a pocket of
warmer air near skin
• Sweating – water evaporating removes heat
energy from the skin
• Panting – loss of body heat as water
evaporates from moist surfaces of resp.
tract (birds, dogs, bears)
Maintaining Temperature
• Peripheral thermoreceptors in skin
• Thermoreceptors deeper in body
• Feed input to hypothalamus
• Hypothalamus sends messages to
effectors by way of nervous system
Response to Heat Stress
• Peripheral vasodilation
• Sweating
• Panting
Response to Cold
• Peripheral vasoconstriction
• Pilomotor response –moving the hairs
• Shivering response
• Nonshivering heat response
Fever
• Part of response to tissue damage
• Hypothalamus resets body thermostat
at higher temperature
• Moderate fever can promote healing
and need not be suppressed
ECTOTHERM METHODS
• CONDUCTION – direct transfer of heat
between molecules of objects in contact
(lizard on a hot rock)
• CONVECTION – transfer of heat by
movement of air or liquid past a surface –
blood moving heat from extremities to the
core
• RADIATION – sun
• EVAPORATION – cooling effect