Presentation on theme: "Why oxygen is import Most animals satisfy their energy requirement by oxidation of food, in the processes forming carbon dioxide and water Oxygen is most."— Presentation transcript:
Why oxygen is import Most animals satisfy their energy requirement by oxidation of food, in the processes forming carbon dioxide and water Oxygen is most abundant element in the earth’s crust (49.2%) In atmosphere Per liter water (15 0 C, 1 atm) O % 7.22 ml CO2 0.03% ml N % 16.9 ml Argon 0.93% Total100%
760 mm Pressure at sea level Mercury (Hg) Pressure exerted by atmospheric air above Earth’s surface Vacuum
Oxygen is added to atmosphere: Photosynthesis (dominant) Photodissociation of water vapor Oxygen is removed from atmosphere: Living organism respiration Oxidizing of organic matter, rocks, gases and fossil fuels Oxygen and carbon dioxide in physical environment
"Global warming" is a real phenomenon: Earth's temperature is increasing. True False
Fig. 11-2, p.464
Solubility of oxygen decreases with increasing water temperature and salinity Temperature Fresh water Sea water ml O 2 /L water Normoxic water: 100% saturated with oxygen Hypoxic water contains less oxygen than normoxic water Anoxic water contains no dissolved oxygen Oxygen and carbon dioxide in physical environment
Transport O 2 and CO 2 in living systems Diffusion is common mechanism for transport both O 2 and CO 2 across the body surface To maximize the rate of gas transfer Large respiratory surface area Small diffusion distance
bronchial tree The lungs contain many branching airways which collectively are known as the bronchial tree
The trachea and all the bronchi have supporting cartilage which keeps the airways open. Bronchioles lack cartilage and contain more smooth muscle in their walls than the bronchi, for airflow regulation The airways from the nasal cavity through the terminal bronchioles are called the conducting zone. The air is moistened, warmed, and filtered as it flows through these passageways.
The pulmonary arteries carry blood which is low in oxygen from the heart to the lungs. These blood vessels branch repeatedly, eventually forming dense networks of capillaries that completely surround each alveolus. oxygen and carbon dioxide are exchanged between the air in the alveoli and the blood in the pulmonary capillaries. Blood leaves the capillaries via the pulmonary veins, which transports the oxygenated blood out of the lungs and back to the heart.
Alveoli ~ 300 million air sacs. –Large surface area (60 – 80 m 2 ). Each alveolus is 1 cell layer thick. Total air barrier is 2 cells across (0.5 m). 3 types of cells: Alveolar type I: –Structural cells. Alveolar type II: –Secrete surfactant.
Ventilation Mechanical process to move air in and out of the lungs. O 2 of air is higher in the lungs than in the blood, O 2 diffuses from air to the blood. C0 2 moves from the blood to the air by diffusing down its concentration gradient. Gas exchange occurs entirely by diffusion. Diffusion is rapid because of the large surface area and the small diffusion distance.
Three types of cells: 1. simple epithelium cells 2. alveolar macrophages 3. surfactant-secreting cells The wall of an alveolus is primarily composed of simple epithelium, or Type I cells. Gas exchange occurs easily across this very thin epithelium. The alveolar macrophages, or dust cells, creep along the inner surface of the alveoli, removing debris and microbes. The alveolus also contains scattered surfactant-secreting, or Type II, cells.
Water in the fluid creates a surface tension. Surface tension is due to the strong attraction between water molecules at the surface of a liquid, which draws the water molecules closer together. Surfactant, which is a mixture of phospholipids and lipoproteins, lowers the surface tension of the fluid by interfering with the attraction between the water molecules, preventing alveolar collapse. Without surfactant, alveoli would have to be completely reinflated between breaths, which would take an enormous amount of energy.
The wall of an alveolus and the wall of a capillary form the respiratory membrane, where gas exchange occurs.
Summary The lungs contain the bronchial tree, the branching airways from the primary bronchi through the terminal bronchioles. The respiratory zone of the lungs is the region containing alveoli, tiny thin-walled sacs where gas exchange occurs. Oxygen and carbon dioxide diffuse between the alveoli and the pulmonary capillaries across the very thin respiratory membrane.
Three main factors: 1.The surface area and structure of the respiratory membrane. 2. Partial pressure gradients 3. Matching alveolar airflow to pulmonary capillary blood flow
Fig , p.480 Atmospheric pressure (the pressure exerted by the weight of the gas in the atmosphere on objects on the Earth’s surface—760 mm Hg at sea level) Lungs (represents all alveoli collectively) Pleural sac (space represents pleural cavity) Thoracic wall (represents entire thoracic cage) Airways (represents all airways collectively) 756 mm Hg 760 mm Hg Atmosphere 760 mm Hg Intrapleural pressure (the pressure within the pleural sac—the pressure exerted outside the lungs within the thoracic cavity, usually less than atmospheric pressure at 756 mm Hg) Intra-alveolar pressure (the pressure within the alveoli—760 mm Hg when equilibrated with atmospheric pressure)
Fig , p.481 Thoracic wall Numbers are mm Hg pressure. Transmural pressure gradient across thoracic wall = atmospheric pressure minus intrapleural pressure Transmural pressure gradient across lung wall = intra-alveolar pressure minus intrapleural pressure Lung wall Airways Pleural cavity (greatly exaggerated) Lungs (alveoli)
Fig , p.482 Accessory muscles of inspiration (contract only during forceful inspiration) Muscles of active expiration (contract only during active expiration) Internal intercostal muscles Abdominal muscles Major muscles of inspiration (contract every inspiration; relaxation causes passive expiration) Diaphragm External intercostal muscles Ribs Sternum Scalenus Sternocleidomastoid
Fig a, p.483 Contraction of external intercostal muscles causes elevation of ribs, which increases side-to-side dimension of thoracic cavity Inspiration Before inspiration Elevation of ribs causes sternum to move upward and outward, which increases front-to-back dimension of thoracic cavity Contraction of diaphragm Contraction of external intercostal muscles External intercostal muscles (relaxed) Diaphragm (relaxed) (a) Lowering of diaphragm on contraction increases vertical dimension of thoracic cavity Elevated rib cage Sternum
Fig bc, p.483 Active expiration (c) (b) Contraction of internal intercostal muscles flattens ribs and sternum, further reducing side-to-side and front-to-back dimensions of thoracic cavity Contraction of abdominal muscles causes diaphragm to be pushed upward, further reducing vertical dimension of thoracic cavity Relaxation of diaphragm Return of diaphragm, ribs, and sternum to resting position on relaxation of inspiratory muscles restores thoracic cavity to preinspiratory size Position of relaxed abdominal muscles Contraction of abdominal muscles Relaxation of external intercostal muscles Contraction of internal intercostal muscles Passive expiration
Fig , p.486 An alveolus H 2 O molecules
Fig , p.489
Fig , p.490
Factors affecting the exchange of oxygen and carbon dioxide during internal respiration: 1.The available surface area 2. Partial pressure gradients. 3. The rate of blood flow in a specific tissue.
Oxygen and Carbon Dioxide Transportation The blood transports oxygen and carbon dioxide between the lungs and other tissues throughout the body. These gases are carried in several different forms: 1. dissolved in the plasma 2. chemically combined with hemoglobin 3. converted into a different molecule
Hemoglobin and 0 2 Transport 280 million hemoglobin/ RBC. Each hemoglobin has 4 polypeptide chains and 4 hemes. Each heme has 1 atom iron that can combine with 1 molecule O 2 Each hemoglobin can combine with 4 molecule O 2 Combine reversibly with O 2 depend on P O2
the affinity of hemoglobin for oxygen decreases as its saturation decreases Hemoglobin's affinity for oxygen increases as its saturation increases
Hemoglobin Oxyhemoglobin: –Normal heme contains iron in the reduced form. Reduced form of iron can share electrons and bond with oxygen. Deoxyhemoglobin: –When oxyhemoglobin dissociates to release oxygen, the heme iron is still in the reduced form.
Hemoglobin Hemoglobin production controlled by erythropoietin. Production stimulated by P 02 delivery to kidneys. Loading/unloading depends: –P 02 of environment. –Affinity between hemoglobin and 0 2.
Oxygen dissociation curve describes the relation between percent of saturation and the partial pressure of oxygen (S-shape, sigmoid) At high P O 2, a large amount of O2 is bound At low P O 2, only small amount of O2 is bound Oxyhemoglobin Dissociation Curve
Hemoglobin saturation is determined by the partial pressure of oxygen S-shaped curve
Oxyhemoglobin Dissociation Curve Loading and unloading of 0 2. Steep portion of the curve, small changes in P 02 produce large differences in % saturation (unload more 0 2 ). Decreased pH, increased temp., and increased 2,3 DPG, increase CO 2 affinity of Hb for 0 2 decreases. Shift to the right greater unloading. Bohr effect
Muscle Myoglobin Slow-twitch skeletal fibers and cardiac muscle cells are rich in myoglobin. –Has a higher affinity for 0 2 than hemoglobin. Acts as a “go-between” in the transfer of 0 2 from blood to the mitochondria within muscle cells. May also have an 0 2 storage function in cardiac muscles.
Human fetal hemoglobin contains chains, which has a high O2 affinity than adult hemoglobin In humans, the oxygen affinity of blood decrease for about 3 months after the birth
This reaction is catalyzed by the enzyme carbonic anhydrase.
C0 2 transported in the blood: –HC0 3 - (70%). –Dissolved C0 2 (7%). –Carbaminohemoglobin (23%). –HCO 3 - is high in plasma than in erythrocytes –CO 2 enters and leaves the blood as molecular CO 2 rather than HCO 3 - C0 2 Transport
Chloride Shift at Systemic Capillaries H C0 2 H 2 C0 3 H + + HC0 3 - At the tissues, C0 2 diffuses into the RBC, reaction shifts to the right. Increased [HC0 3 - ] in RBC, HC0 3 - diffuses into the plasma with assistance of band III protein. RBC becomes more +. Cl - diffuses in (Cl - shift). HbC0 2 formed, give off 0 2.
At Pulmonary Capillaries H C0 2 H 2 C0 3 H + + HC0 3 - At the alveoli, C02 diffuses into the alveoli, reaction shifts to the left. Decreased [HC0 3 - ] in RBC, HC0 3 - diffuses into the RBC. RBC becomes more -. Cl - diffuses out (Cl - shift). Hb0 2 formed, give off HbC0 2.
Summary O2 is transported in two ways: dissolved in plasma, and bound to hemoglobin as oxyhemoglobin The O2 saturation of hemoglobin is affected by: PO2, pH, temperature, PCO2, and DPG CO2 is transported in three ways: dissolved in plasma, bound to hemoglobin as carbaminohemoglobin, and converted to bicarbonate ions Oxygen loading facilitates carbon dioxide unloading from hemoglobin. This is known as the Haldane effect. When the pH decreases, carbon dioxide loading facilitates oxygen unloading. The interaction between hemoglobin's affinity for oxygen and its affinity for hydrogen ions is called the Bohr effect.
Fig , p.513 Respiratory control centers in brain stem Pons Medulla Pre-Bötzinger complex Dorsal respiratory group Ventral respiratory group Pons respiratory centers Medullary respiratory center Apneustic center Pneumotaxic center
Fig , p.513 Input from other areas–– some excitatory, some inhibitory Diaphragm Phrenic nerve Not shown are intercostal nerves to external intercostal muscles. Spinal cord Medulla Inspiratory neurons in DRG (rhythmically firing) + +