Chapter 42: Gas Exchange and Circulatory System. Presented by: McQuade and Verpooten. Circulatory Systems Reflect Phylogeny. In unicellular organisms Exchanges occur directly with the environment For most of the cells making up multicellular organisms
Chapter 42: Gas Exchange and Circulatory System
Presented by: McQuade and Verpooten
Hemolymph in sinusessurrounding ograns
(a) An open circulatory system
Small branch vessels in each organ
Dorsal vessel(main heart)
(b) A closed circulatory system
Lung and skin capillaries
REPTILES (EXCEPT BIRDS)
MAMMALS AND BIRDS
of right lung
of left lung
and hind limbs
Anterior vena cava
Posterior vena cava
to heart apex.
Pacemaker generates wave of signals to contract.
Signals are delayed
at AV node.
Direction of blood flowin vein (toward heart)
Icons (blood electrolytes
pH buffering, and
Substances transported by blood
Nutrients (such as glucose, fatty acids, vitamins)
Waste products of metabolism
Respiratory gases (O2 and CO2)
Cellular elements 45%
Numberper L (mm3) of blood
Erythrocytes(red blood cells)
Transport oxygenand help transportcarbon dioxide
Leukocytes(white blood cells)
Pluripotent stem cells(in bone marrow)
(a) Normal artery
(b) Partly clogged artery
Figure 42.18a, b
Respiratorymedium(air of water)
Gas Exchange Occurs Across Specialized Respiratory Surfaces
Remember key biological concept….lots of body structure have numerous folds to increase surface area for chemical reaction
Endotherms. While respiratory area depends mainly on the size of the organism and whether it lives in a terrestrial or aquatic environment, endotherms utilize more energy (ATP) and so must do more cellular respiration than a similarly sized ectotherm
(a) Sea star. The gills of a sea star are simple tubular projections of the skin. The hollow core of each gillis an extension of the coelom(body cavity). Gas exchangeoccurs by diffusion across thegill surfaces, and fluid in thecoelom circulates in and out ofthe gills, aiding gas transport. The surfaces of a sea star’s tube feet also function in gas exchange.
Blood flowthrough capillariesin lamellaeshowing % O2
Water flowover lamellaeshowing % O2
Advantages of air
Disadvantages of air
Respiratory surfaces must be large and MOIST
Air dries things out
(a) The respiratory system of an insect consists of branched internaltubes that deliver air directly to body cells. Rings of chitin reinforcethe largest tubes, called tracheae, keeping them from collapsing. Enlarged portions of tracheae form air sacs near organs that require a large supply of oxygen. Air enters the tracheae through openings called spiracles on the insect’s body surface and passes into smaller tubes called tracheoles. The tracheoles are closed and contain fluid(blue-gray). When the animal is active and is using more O2, most ofthe fluid is withdrawn into the body. This increases the surface area of air in contact with cells.
(b) This micrograph shows crosssections of tracheoles in a tinypiece of insect flight muscle (TEM).Each of the numerous mitochondriain the muscle cells lies within about5 µm of a tracheole.
With virtually all body cells within a very short distance of respiratory medium, the open circulatory system of insects is not involved in transporting O2 and CO2
For small insects, diffusion through the trachea brings in enough oxygen and removes enough carbon dioxide to support cellular respiration
Larger insects with higher energy demands ventilate their tracheal systems with rhythmic body movements that compress and expand the air tubes like bellows
Unlike the branching tracheal system of insects, lungs are confined to 1 location
Because the respiratory surface of a lung is not in direct contact with all other body cells, the gap must be bridged by the circulatory system
Branch from thepulmonaryartery(oxygen-poor blood)
Branch from the pulmonary vein (oxygen-rich blood)
The larynx wall is reinforced with cartilage and in most mammals is adapted as a voice box
Inhaled air rushes past vocal chords in the larynx
Sounds are produced when voluntary muscles in the voice box are tensed stretching the chords so they vibrate
Rib cage expands asrib muscles contract
Rib cage gets smaller asrib muscles relax
INHALATIONDiaphragm contracts(moves down)
EXHALATIONDiaphragm relaxes(moves up)
Air tubes(parabronchi)in lung
EXHALATIONAir sacs empty; lungs fill
INHALATIONAir sacs fill
The medulla’s control center
also helps regulate blood CO2 level.
Sensorsin the medulla detect changes
in the pH (reflecting CO2 concentration)
of the blood and cerebrospinal fluid
bathing the surface of the brain.
The control center in the
medulla sets the basicrhythm, and a control centerin the pons moderates it,smoothing out thetransitions between
inhalations and exhalations.
Nerve impulses relay changes in CO2 and O2 concentrations. Other sensors in the walls of the aortaand carotid arteries in the neck detect changes in blood pH andsend nerve impulses to the medulla. In response, the medulla’s breathingcontrol center alters the rate anddepth of breathing, increasing bothto dispose of excess CO2 or decreasingboth if CO2 levels are depressed.
Breathing control centers
Nerve impulses trigger muscle contraction. Nervesfrom a breathing control centerin the medulla oblongata of the brain send impulses to thediaphragm and rib muscles, stimulating them to contractand causing inhalation.
In a person at rest, these nerve impulses result in about 10 to 14 inhalationsper minute. Between inhalations, the musclesrelax and the person exhales.
The sensors in the aorta andcarotid arteries also detect changesin O2 levels in the blood and signal the medulla to increase the breathing rate when levels become very low.
PO2 = 0.21X 760 = 160mmHg
PCO2 = 0.23mmHg
Consists of 4 subunits each with a cofactor called a heme group that has an iron atom at its center
The iron binds the oxygen, thus each molecule of hemoglobin can carry four molecules of oxygen
A typical RBC has 250 million molecules of hemoglobin
The process of loading and unloading oxygen depends on cooperativity of the 4 subunits that make up hemoglobin
Binding of oxygen to 1 subunit induces the others to change shape slightly resulting in higher affinity for oxygen
When 1 subunit unloads oxygen the others quickly revert back to original shape lowering their affinity for oxygen
As with all proteins hemoglobins conformation is sensitive to a variety of factors including pH
Bohr Shift: when a drop in pH lowers the affinity of hemoglobin for oxygen
Because CO2 reacts with H2O to form carbonic acid (H2CO3) an active tissue lowers the pH of its surroundings and induces hemoglobin to release more O2