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Osmoregulation & Excretion
Chapter 44, pp. 931-939
From Leonardo da Vinci’s notebooks
An organism’s excretory system
helps regulate the chemical composition
of the body’s principal fluid (blood,
coelomic fluid, or hemolymph)
The excretory system selectively
removes excess water and wastes from
the principal fluid
Excretory systems
Breakdown of proteins and nucleic acids
produces ammonia (a toxin)
Many aquatic
organisms excrete
ammonia, since it
can be effectively
diluted with water
Fig.
44.8
Ammonia NH3
Excretory systems
Breakdown of proteins and nucleic acids
produces ammonia (a toxin)
Mammalian livers
convert ammonia
into urea, which is
much less toxic, and
requires less water to
excrete
Fig.
44.8
Ammonia NH3
Excretory systems
Breakdown of proteins and nucleic acids
produces ammonia (a toxin)
Birds, reptiles, and
some other
organisms convert
ammonia into uric
acid, which is
relatively nontoxic,
and can be excreted
as a semisolid
without much water
loss
Fig.
44.8
Ammonia NH3
Vertebrate Excretory Systems
Key functions:
Filtration
Reabsorption
Secretion
Excretion
Fig.
44.9
Vertebrate Excretory Systems
Blood enters the
kidneys via the renal
arteries and leaves
via the renal veins
Urine (excess water and wastes removed from the
blood) is produced by the kidneys and is conveyed
to the urinary bladder via the ureters
Urine exits the body
via the urethra
Fig. 44.13
Vertebrate Excretory Systems
Each kidney is divided into a
cortex, medulla, and pelvis
Each kidney processes about
1000 L of blood per day!
Fig. 44.13
Vertebrate Excretory Systems
Nephrons = the functional
units of the kidneys
Packed into the renal cortex
and medulla
Fig. 44.13
Vertebrate Excretory Systems
Each kidney has ~ 1 million
nephrons
Fig. 44.13
Vertebrate Excretory Systems
A nephron consists of: a ball of capillaries
known as a glomerulus
Fig. 44.13
Vertebrate Excretory Systems
A nephron consists of: an afferent arteriole that
leads into the glomerulus, and an efferent arteriole
that leads out of the glomerulus
Fig. 44.13
Vertebrate Excretory Systems
A nephron consists of: Bowman’s capsule, that
surrounds the glomerulus and extends into the
proximal tubule, loop of Henle, and distal tubule
Fig. 44.13
Vertebrate Excretory Systems
A nephron consists of: capillaries that surround the
tubules and loop of Henle, and that feed into venules
returning to the renal vein
Fig. 44.13
Vertebrate Excretory Systems
Filtration occurs in Bowman’s capsules: cells and
large molecules remain in the blood, while blood
pressure forces water and small molecules from the
blood into Bowman’s capsules
Fig. 44.13
Vertebrate Excretory Systems
Filtration occurs in Bowman’s capsules: cells and
large molecules remain in the blood, while blood
pressure forces water and small molecules from the
blood into Bowman’s capsules
Vertebrate Excretory Systems
Selective reabsorption returns important nutrients
(glucose, etc.) to the blood, and occurs especially in
proximal and distal tubules
Fig. 44.13
Vertebrate Excretory Systems
Selective reabsorption returns important nutrients
(glucose, etc.) to the blood, and occurs especially in
proximal and distal tubules
Red arrows =
active transport
Blue arrows =
passive transport
Fig. 44.14
Vertebrate Excretory Systems
Selective secretion adds additional waste
molecules to the filtrate, especially in the tubules
Red arrows =
active transport
Blue arrows =
passive transport
Fig. 44.14
Vertebrate Excretory Systems
Reabsorption of water occurs along the tubules,
descending loop of Henle, and collecting duct
Red arrows =
active transport
Blue arrows =
passive transport
Fig. 44.14
Vertebrate Excretory Systems
Reabsorption of water occurs along the tubules,
descending loop of Henle, and collecting duct
Red arrows =
active transport
Blue arrows =
passive transport
Fig. 44.15
Vertebrate Excretory Systems
The descending loop of Henle is permeable to
water, but not very permeable to salt (e.g., NaCl)
Red arrows =
active transport
Blue arrows =
passive transport
Fig. 44.15
Vertebrate Excretory Systems
The ascending loop of Henle is not permeable to
water, but it is to NaCl
Red arrows =
active transport
Blue arrows =
passive transport
Fig. 44.15
Vertebrate Excretory Systems
High concentration of NaCl outside the nephron deep in
the kidneys helps concentrate urine in the collecting duct
Red arrows =
active transport
Blue arrows =
passive transport
Fig. 44.15
Mammalian excretory systems are adapted
to diverse environments
Mammalian excretory systems are adapted
to diverse environments
Mammals that live in environments with plenty of
water have short loops of Henle that cannot produce
concentrated urine
Mammalian excretory systems are adapted
to diverse environments
Mammals that live in very dry environments have very
long loops of Henle that can produce highly
concentrated urine
Hormones and
the Endocrine
System
Chapter 45
The endocrine system = postal
system for the body
The endocrine system = postal
system for the body
Hormones are the chemical messages that:
Regulate aspects of behavior
Regulate growth, development, &
differentiation
Maintain internal homeostatic conditions
4 classes of animal hormones:
Peptide hormones – amino acid chains
Single amino acid derivatives
Steroid hormones – cholesterol based
Prostaglandins – fatty-acid based
The endocrine system = postal
system for the body
Hormones are the chemical messages that:
Maintain internal homeostatic conditions
Regulate growth, development, &
differentiation
Regulate aspects of behavior
4 classes of animal hormones:
Single amino acid derivatives
Peptide hormones – amino acid chains
Steroid hormones – cholesterol based
Prostaglandins – fatty-acid based
The endocrine system = postal
system for the body
Hormones are the chemical messages that:
Maintain internal homeostatic conditions
Regulate growth, development, &
differentiation [often irreversible]
Regulate aspects of behavior
4 classes of animal hormones:
Single amino acid derivatives
Peptide hormones – amino acid chains
Steroid hormones – cholesterol based
Prostaglandins – fatty-acid based
The endocrine system = postal
system for the body
Hormones are the chemical messages that:
Maintain internal homeostatic conditions
Regulate growth, development, &
differentiation [often irreversible]
Regulate aspects of behavior [generally reversible]
The endocrine system = postal
system for the body
Hormone-secreting organs are called endocrine
glands, because they secrete their chemical
messengers directly into body fluids
In contrast, exocrine glands secrete their
products into ducts
Glands that secrete sweat, mucus, digestive
enzymes, and milk are exocrine glands
Since hormones circulate to ALL
cells, how do they act at only
specific sites?
Receptors
Only cells with correct receptors
(target cells) respond to hormones
The target cell response is
idiosyncratic (i.e., it depends on the
type of cell)
Fig. 45.4
Hormones exhibit a diversity of structure and function
Peptides, proteins, glycoproteins, amines,
Table
45.1
Hormones exhibit a diversity of structure and function
Peptides, proteins, glycoproteins, amines, steroids
Table
45.1
Since hormones circulate to ALL
cells, how do they act at only
specific sites?
Receptors
Only cells with correct receptors
(target cells) respond to hormones
Surface receptors
Intracellular receptors
Surface Receptors
Most amino acid-based hormones are water soluble
and target surface receptors
A signal-transduction pathway is a series of molecular
changes that converts an extracellular chemical signal to
a specific intracellular response
Fig. 45.3
Intracellular Receptors
Most steroid hormones are lipid soluble
and target intracellular receptors
An intracellular receptor usually performs the entire
task of transducing the signal within the cell
In almost all cases, this is a transcription factor, and the
response is a change in gene expression
Fig. 45.3
Major
endocrine
organs
and
glands
Fig. 45.6
Hypothalamus-Pituitary Complex
The hypothalamus receives nervous input from
throughout the body
The hypothalamus contains two sets of
neurosecretory cells whose hormonal secretions are
stored in or regulate the pituitary gland
The posterior pituitary stores and secretes two
hormones made by the hypothalamus
The anterior pituitary consists of endocrine cells that
synthesize and secrete at least 6 different hormones
Hypothalamus-Pituitary Complex
Pathway
Example
Stimulus
Suckling
Sensory
neuron
Hypothalamus/
posterior pituitary
Neurosecretory
cell
The hypothalamus-posterior
pituitary provides an example
of a simple neurohormone
pathway
Oxytocin
Blood
vessel
Target
effectors
Response
Smooth muscle
in breast
Milk release
Fig. 45.2b
Hypothalamus-Pituitary Complex
Example
Pathway
Hypothalamic
Stimulus
neurohormone
released in
Sensory response to
neural and
neuron
hormonal
signals
Hypothalamus
Neurosecretory
cell
Blood
capillary
The hypothalamus-anterior
pituitary provides an example
of a simple neuroendocrine
pathway
Prolactinreleasing
hormone
Endocrine
cell of pituitary
Prolactin
Blood
vessel
Target
effectors
Response
Mammary glands
Milk production
Fig. 45.2c
Major
endocrine
organs
and
glands
Fig. 45.6
Pancreas
Exocrine function
Digestive secretions released into
pancreatic duct to small intestines
Endocrine function
Islet cells
Insulin
Glucagon
Pancreas
Exocrine function
Digestive secretions released into
pancreatic duct to small intestines
Endocrine function
Islet cells
Insulin
Glucagon
Pancreas
Exocrine function
Digestive secretions released into
pancreatic duct to small intestines
Endocrine function
Islets of Langerhans – endocrine cells
Insulin
antagonistic hormones
Glucagon
Pancreas regulates blood glucose
Insulin – decrease blood glucose
stimulates uptake by cells – use it or
store it as fat and glycogen
Glucagon increase blood glucose
stimulates release by cells – breakdown
fat and glycogen
Diabetes mellitis
defects in production, release or
response to insulin
Pancreas regulates blood glucose
Insulin – decreases blood glucose
Stimulates uptake by cells – cells use it
or store it as fat and glycogen
Glucagon – increase blood glucose
stimulates release by cells – breakdown
fat and glycogen
Diabetes mellitis
defects in production, release or
response to insulin
Pancreas regulates blood glucose
Insulin – decreases blood glucose
Stimulates uptake by cells – cells use it
or store it as fat and glycogen
Glucagon – increases blood glucose
Stimulates release by cells – breakdown
of fat and glycogen
Diabetes mellitis
defects in production, release or
response to insulin
Pancreas regulates blood glucose
Pathway
Example
High blood
glucose
Stimulus
Receptor
protein
Pancreas
secretes
insulin
Endocrine
cell
Blood
vessel
Target
effectors
Response
Pathway
Stimulus
Pathway
Suckling
Hypothalamic
neurohormone
released in
response to
Sensory
neural and
neuron
hormonal
signals
Hypothalamus
An example of a simple
endocrine pathway
Sensory
neuron
Hypothalamus/
posterior pituitary
Neurosecretory
cell
Posterior pituitary
secretes oxytocin
Blood ( )
vessel
Liver
Glycogen
synthesis,
glucose uptake
from blood
(a) Simple endocrine pathway
Example
Example
Stimulus
Neurosecretory
cell
Hypothalamus
secretes prolactinBlood
releasing
vessel
hormone ( )
Diabetes mellitus (all forms)
Target
effectors
Response
Anterior
pituitary
secretes
Endocrine prolactin ( )
cell
Blood
vessel
Results from defects in the
production, release or
response to insulin
Smooth muscle
in breast
Milk release
(b) Simple neurohormone pathway
Target
effectors
Response
Mammary glands
Milk production
(c) Simple neuroendocrine pathway
Fig. 45.2a
Hormone-like local regulators appear to
be produced by all the body’s cells…
These chemical messengers affect
target cells adjacent to or near their
point of secretion and can act very
rapidly; the process is known as
paracrine signaling
The same
hormones are
found across
diverse taxa
E.g., Insulin is found
in bacteria, fungi,
protists, etc.
E.g., Thyroxin is
found in
many vertebrates;
increases metabolism
in humans & controls
metamorphosis
in amphibians
The same
hormones are
found across
diverse taxa
E.g., Insulin is found
in bacteria, fungi,
protists, etc.
E.g., Thyroxin is
found in
many vertebrates;
increases metabolism
in humans & controls
metamorphosis
in amphibians
The same
hormones are
found across
diverse taxa
E.g., Insulin is found
in bacteria, fungi,
protists, etc.
E.g., Thyroxin is
found in
many vertebrates;
increases metabolism
in humans & controls
metamorphosis
in amphibians