Respiration Chapter 24

Types of Respiratory Systems Respiration is the uptake of oxygen and the simultaneous release of carbon dioxide. Most primitive animal phyla obtain oxygen directly from their environments through diffusion. More advanced phyla have specific respiratory organs: Gills, tracheae, and lungs

Gas exchange in animals CO2 O2 Gill filament CO2 Body wall O2 Gill Fish Blood vessels Flatworm Tracheoles Trachea O2 Trachea Mammalian lung Blood vessels Alveoli Mammal CO2 O2 Spiracles CO2 O2 CO2 Spiracle Terrestrial arthropod

Respiration in Aquatic Vertebrates Water always moves past a fish’s gills in one direction. Gill raker Gill arch Water Gill filaments Lamellae with capillary networks Direction of water flow Direction of blood flow Vein Artery

Respiration in Aquatic Vertebrates Blood (85% O2 saturation) Countercurrent exchange Concurrent exchange Water (50% Water (100% O2saturation) Blood (50% No further net diffusion 50% 60% 70% 80% 90% (b) Blood (0% Water(15% 10% 20% 30% 40% 85% 100% 15% (a) Water(100% Moving the water past the gills in the same direction permits countercurrent flow. This process is an extremely efficient way of extracting oxygen. Blood flows through a gill filament in an opposite direction to the movement of water. The blood in the blood vessels always encounters water with a higher oxygen concentration, resulting in the diffusion of oxygen into the blood vessels.

Respiration in Terrestrial Vertebrates Lungs are less efficient than gills because new air that is inhaled mixes with old air already in the lung. But there is so much more oxygen in air than in water.

Respiration in Terrestrial Vertebrates The lungs of mammals possess on their inner surface many small chambers called alveoli, which greatly increases surface area for the diffusion of oxygen. (a) Amphibian (b )Reptile (c) Mammal Alveoli Bronchiole

Respiration in Terrestrial Vertebrates Flying creates a respiratory demand for oxygen that exceeds the capacity of the saclike lungs of even the most active mammal. Birds have evolved the most efficient lung. An avian lung is connected to a series of air sacs outside of the lung. Lung Trachea Anterior air sacs (a) Posterior (b) Inspiration Parabronchi of lung Expiration Cycle 1 Cycle 2 http://youtu.be/kWMmyVu1ueY

Respiration in Terrestrial Vertebrates This creates a unidirectional flow of air through the lungs. Blood flow and airflow are not opposite but flow at perpendicular angles in crosscurrent flow. Avian lungs Mammalian lungs Uniform pool Cross current Counter current Fish gills Blood (c)

The Mammalian Respiratory System Nasal cavity Nostril Glottis Larynx Trachea Right lung Pharynx Epiglottis Left lung Left bronchus In the mammalian respiratory system, air passes in and out of the lungs, which are housed in the thoracic cavity. Air is warmed and filtered as it flows through the nasal cavity. It passes next through the pharynx, then the larynx (or voice box), then to the trachea, or windpipe.

The Mammalian Respiratory System From there, air passes through several branchings of bronchi in the lungs and then to the bronchioles. The tissue of the lungs is divided into tiny air sacs called alveoli; through these thin-walled cells, gas exchange with the blood occurs. Blood flow Smooth muscle Bronchiole Pulmonary arteriole Pulmonary venule Alveolar sac Alveoli Capillary network on surface of alveolus

The Mammalian Respiratory System The mammal respiratory apparatus is simple in structure and functions as a one-cycle pump. A diaphragm muscle separates the thoracic cavity from the abdominal cavity. Each lung is covered by a thin, smooth membrane called the pleural membrane. This membrane adheres to another pleural membrane lining the walls of the thoracic cavity, basically coupling the lungs to the thoracic cavity.

The Mammalian Respiratory System Air is drawn into the lungs by the creation of negative pressure. The active pumping of air in and out is called breathing. During inhalation, muscular contraction causes the chest cavity to expand. During exhalation, the ribs and diaphragm return to their original position.

Key Biological Process: Breathing 1 2 3 Pair Pair Pair Inhalation Exhalation Chest cavity expands Plung Plung Plung Diaphragm relaxed Diaphragm relaxed Diaphragm contracts Plung > Pair Plung = Pair Plung < Pair Before inhalation, the air pressure in the lungs (Plung) is equal to the atmospheric pressure (Pair). During inhalation, the diaphragm contracts, and the chest cavity expands downward and outward. This increases the volume of the chest cavity and lungs, which reduces the air pressure inside the lungs, and the air from outside the body flows into the lungs. During exhalation, the diaphragm relaxes, decreasing the volume of the chest cavity. The pressure increases in the lungs, forcing air out of the lungs.

How Respiration Works: Gas Exchange Oxygen moves through the circulatory system carried by the protein hemoglobin. Hemoglobin molecules contain iron, which binds oxygen in a reversible way. Heme group Beta (β) chains Oxygen (O2) Iron (Fe++) Alpha () chains

How Respiration Works: Gas Exchange Hemoglobin molecules act like little sponges for oxygen. At the high O2 levels that occur in the blood supply at the lung, most hemoglobin molecules carry a full load of O2. In the tissues, the O2 levels are much lower, so hemoglobin gives up its bound oxygen. In the presence of CO2, the hemoglobin assumes a different shape that gives up its oxygen more readily.

How Respiration Works: Gas Exchange CO2 must also be transported by the blood. About 8% simply dissolves in the plasma. 20% is bound to hemoglobin but at a different site than where O2 binds. The remaining 72% diffuses into the red blood cells. In order to maintain the gradient for CO2 to leave the tissues and enter the plasma, the CO2 levels in the plasma must be kept low.

How Respiration Works: Gas Exchange The enzyme carbonic anhydrase combines CO2 with water to form carbonic acid (H2CO3). This acid dissociates into bicarbonate (HCO3–) and H+. Bicarbonate also acts as buffer in the blood plasma. In the lungs, the reverse reaction takes place, and CO2 is released.

The Nature of Lung Cancer Lung cancer is one of the leading causes of death among adults. Mutations to two tumor-suppressing genes are implicated in the development of cancer. Rb codes for Rb protein, which acts as a brake on cell division. p53 codes for p53 protein, which detects damaged or foreign DNA and prevents its replication.

The Nature of Lung Cancer Smoking causes lung cancer. The annual incidence of lung cancer is much higher for smokers than for nonsmokers. Changes in the incidence of lung cancer have mirrored changes in smoking habits. Many types of mutagens are found in cigarette smoke that can damage genes. The p53 gene is damaged in 70% of lung cancers. Smoking also leads to nicotine addiction.

Incidence of lung cancer in men and women 1 Per capita cigarette consumption Lung cancer death rates per 100,000 3000 2500 2000 1500 1000 500 1900 10 20 30 40 50 60 70 80 90 Males Cigarette consumption 30years Lung cancer deaths Time Females 100 2010 1910 1920 1930 1940 1950 1960 1970 1980 1990 960 Incidence of lung cancer in men and women