Download Chapter six Internal Fluids and Respiration

Chapter six
Internal Fluids and Respiration
Dr. Mohamed Ibrahim Abdi
“Soojeede”
Master of HSM at KU
INTRODUCTION
• Single-celled organisms live in direct contact with
their environment. They obtain nutrients and
oxygen and release wastes directly across the cell
surface. These organisms as so small that no
special internal system of transport.
• Most other multicellular organisms, because of
their size, activity, and complexity, need a
specialized circulatory system to transport
nutrients and respiratory gases to and from all
tissues of the body.
Internal Fluid Environment
• The body fluid of a single-celled organism is
cellular cytoplasm, a liquid-gel substance in which
the various membrane systems and organelles
are suspended.
• In multicellular animals body fluids are divided
into two main phases, intracellular and
extracellular.
– The intracellular phase (also called intracellular fluid)
is the collective fluid inside all the body’s cells.
– The extracellular phase (or fluid) is the fluid outside
and surrounding the cells.
• In animals having closed circulatory systems
extracellular fluid is further subdivided into
blood plasma and interstitial (intercellular)
fluid.
– Blood vessels contain plasma,
– whereas interstitial fluid, or tissue fluid as it is
sometimes called, occupies spaces surrounding
the cells in the body. Interstitial fluid is constantly
formed from plasma by filtration through capillary
walls.
Composition of the Body Fluids
• All these fluid spaces—plasma, interstitial, and
intracellular—differ from each other in solute
composition, but all have one feature in common: they
are mostly water.
• Body fluids contain many inorganic and organic
substances in solution. Principal among these are
inorganic electrolytes and proteins. Sodium, chloride,
and bicarbonate ions are the chief extracellular
electrolytes, whereas potassium, magnesium, and
phosphate ions and proteins are the major
intracellular electrolytes.
• The two subdivisions of extracellular fluid—plasma and
interstitial fluid—have similar compositions except that
plasma has more proteins.
Composition of Blood
• Among invertebrates that lack a circulatory system
(such as flatworms and cnidarians) it is not possible to
distinguish a true “blood.” These forms possess a clear,
watery tissue fluid containing some phagocytic cells, a
little protein, and a mixture of salts similar to seawater.
The “blood” of invertebrates with open circulatory
systems is more complex and is often called
hemolymph (Gr. haimo, blood, L. lympha, water).
In vertebrates, blood is a complex liquid tissue
composed of plasma and formed elements, mostly red
cells (also called corpuscles), suspended in plasma.
Types of Circulatory Systems in
Animals
• Simple Circulatory Systems
• The circulatory system varies from simple systems in invertebrates
to more complex systems in vertebrates. The simplest animals, such
as the sponges (Porifera), do not need a circulatory system
because diffusion allows adequate exchange of water, nutrients,
and waste, as well as dissolved gases (figure a).
• Fish Circulatory Systems
• Fish have a single circuit for blood flow and a two-chambered heart
that has only a single atrium and a single ventricle (figure a). The
atrium collects blood that has returned from the body, while the
ventricle pumps the blood to the gills where gas exchange occurs
and the blood is re-oxygenated; this is called gill circulation. The
blood then continues through the rest of the body before arriving
back at the atrium; this is called systemic circulation.
Amphibian Circulatory Systems
• In amphibians, reptiles, birds, and mammals, blood flow is
directed in two circuits: one through the lungs and back to
the heart (pulmonary circulation) and the other
throughout the rest of the body and its organs, including
the brain (systemic circulation).
• Amphibians have a three-chambered heart that has two
atria and one ventricle. The two atria receive blood from
the two different circuits (the lungs and the systems). There
is some mixing of the blood in the heart's ventricle, which
reduces the efficiency of oxygenation.
• There are another Amphibians which are unique in that
they have a third circuit that brings deoxygenated blood to
the skin in order for gas exchange to occur; this is called
pulmocutaneous circulation.
Reptile Circulatory Systems
• Most reptiles also have a three-chambered heart similar to
the amphibian heart that directs blood to the pulmonary
and systemic circuits. The ventricle is divided more
effectively by a partial septum, which results in less mixing
of oxygenated and deoxygenated blood. Some reptiles
(alligators and crocodiles) are the most primitive animals to
exhibit a four-chambered heart.
• Mammal and Bird Circulatory Systems
• In mammals and birds, the heart is also divided into four
chambers: two atria and two ventricles. The oxygenated
blood is separated from the deoxygenated blood, which
improves the efficiency of double circulation and is
probably required for the warm-blooded lifestyle of
mammals and birds.
Mammalian Heart
• The mammalian heart is a muscular organ
located in the thorax and covered by a tough,
fibrous sac, the pericardium.
Blood returning from the lungs collects in the
left atrium, passes into the left ventricle, and
is pumped into the body (systemic)
circulation. Blood returning from the body
flows into the right atrium, and passes into
the right ventricle, which pumps it into the
lungs.
Respiration
• Energy bound up in food is released by oxidative
processes, usually with molecular oxygen as the
terminal electron acceptor. Physiologists find it
is suitable to distinguish two separate but
interrelated respiratory processes:
– cellular respiration, the oxidative processes that occur
within cells, and
– external respiration, the exchange of oxygen and
carbon dioxide between the organism and its
environment.
Problems of Aquatic and
Aerial Breathing
• The two great arenas of animal evolution water and land—
are vastly different in their physical characteristics. The
most obvious difference is that air contains far more
oxygen—at least 20 times more—than does water.
• The most advanced fishes with highly efficient gills and
pumping mechanisms may use as much as 20% of their
energy just extracting oxygen from water. By comparison,
the cost for mammals to breathe is only 1% to 2% of their
resting metabolism.
• In general evaginations of the body surface, such as gills,
are most suitable for aquatic respiration; invaginations,
such as lungs and tracheae, are best for air breathing.
Respiratory Organs
• Gas Exchange by Direct Diffusion
Protozoa, sponges, cnidarians, and many worms respire
by direct diffusion of gases between organism and
environment. We have noted that this kind of cutaneous
respiration is not adequate when the cellular mass
exceeds approximately 1 mm in diameter.
• Gas Exchange Through Tubes: Tracheal Systems
Insects and certain other terrestrial arthropods
(centipedes, millipedes, and some spiders) have a highly
specialized type of respiratory system, It consists of a
branching system of tubes (tracheae) that extends to all
parts of the body. The smallest end channels are fluidfilled tracheoles, less than 1 um in diameter. Air enters
and diffuses out the tracheal system through valvelike
openings (spiracles).
Efficient Exchange in Water: Gills
• Gills of various types are effective respiratory
devices for life in water. Gills may be simple
external extensions of the body surface, such as
dermal papulae of sea stars. Most efficient are
internal gills of fishes and arthropods.
• Fish gills are thin filamentous structures, richly
supplied with blood vessels arranged so that
blood flow is opposite to the flow of water across
the gills. This arrangement, called countercurrent
flow, provides the greatest possible extraction of
oxygen from water.
Gas Exchange through: Lungs
• The most airbreathing vertebrates possess lungs, highly
vascularized internal cavities.
– Amphibian lungs vary from simple, smooth-walled, baglike
lungs.
– The total surface available for gas exchange is much
increased in lungs of reptiles which are subdivided into
numerous interconnecting air sacs.
– Most elaborate of all are mammalian lungs complexes of
millions of small sacs, called alveoli, each veiled by a rich
vascular network.
– In birds, lung efficiency is improved vastly by adding an
extensive system of air sacs. that serve as air reservoirs
during ventilation.