Respiratory System 1
Outline Respiratory structures Gills Air-Breathing Animals Amphibians and Reptiles Mammals Birds Structures and Mechanisms of Breathing 2
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 44.19(TE Art) O Epidermis CO 2 2 CO 2 O 2 Epidermis Papula O 2 CO 2 Spiracle Trachea O 2 CO 2 CO 2 Blood vessel O 2 CO 2 O 2 CO 2 O 2 Blood vessel Alveoli 3
Air is 21% oxygen 78% nitrogen Gases Less than 1% carbon dioxide and other gases Nitrogen gas usually ignored because it is not part of the respiratory process 4
The Gill as a Respiratory Structure External gills provide a greatly increased surface area for gas exchange. disadvantages are that they must be moved constantly and are easily damaged Gills of bony fish located between buccal cavity and opercular cavity 5
Bony Fish Respiration 6
7
The Gill as a Respiratory Structure Buccal cavity can be opened and closed by opening and closing the mouth. Opercular cavity can be opened and closed by movements of the operculum. ram ventilation blood flows in an opposite direction to the flow of water, thus maximizing oxygenation of blood gill arches countercurrent flow 8
Structure of a Fish Gill 9
Respiration in Air-Breathing Animals Gills replaced in terrestrial animals because: air is less buoyant than water water vapor diffuses into the air through evaporation Two main terrestrial respiratory organs: tracheae lung Lungs use a uniform pool of air in constant contact with gas exchange surface. 10
Respiration in Amphibians and Reptiles Lungs of amphibians are formed as saclike outpouching of the gut. Amphibians force air into their lungs creating positive pressure. fill buccal cavity with air, and then close mouth and nostrils and elevate floor of oral cavity Reptiles expand their rib cages by muscular contraction and take air into lungs via negative pressure breathing. 11
Amphibian Lungs 12
Respiration in Mammals Lungs of mammals packed with alveoli. Air brought to alveoli through system of air passages. Inhaled air taken to the larynx, passes through glottis into the trachea. Bifurcates into right and left bronchi which enter each lung and further subdivide into bronchioles that deliver air into alveoli. 13
Human Respiratory System 14
Mammalian respiratory systems Nose and mouth air is warmed and humidified Mucus in the nose cleans the air of dust Pharynx Larynx vocal cords Trachea glottis (opening to trachea) protected by epiglottis, rings of cartilage, cilia and mucus trap particles Lungs 15
Trachea branches into 2 bronchi Bronchioles surrounded by circular muscle to dilate or constrict passage Alveoli site of gas exchange One cell thick Coated with extracellular fluid for gases to dissolve Surfactant prevents alveoli from collapsing 16
Respiration in Birds Bird lung channels air through tiny air vessels called parabronchi, where gas exchange occurs. unidirectional flow When air sacs are expanded during inspiration, they take in air. When they are compressed during expiration, they push air into and through the lungs. 17
Respiration in Birds Avian respiration occurs in two cycles. Each cycle has an inspiration and an expiration phase. Cross-current flow has the capacity to extract more oxygen from the air than a mammalian lung. 18
How A Bird Breathes 19
Structures and Mechanisms of Breathing The outside of each lung is covered by a visceral pleural membrane. Second parietal pleural membrane lines inner wall of thoracic cavity. pleural cavity between the two membranes 20
Sternocleidomastoid muscles contract (for forced inspiration) Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 44.28(TE Art) Inspiration Expiration Muscles contract Diaphragm contracts Muscles relax Abdominal muscles contract (for forced expiration) Diaphragm relaxes (a) (b) 21
Hemoglobin and Oxygen Transport Hemoglobin is a protein composed of four polypeptide chains and four organic heme groups. iron atom at center of each heme group Hemoglobin loads up with oxygen in the lungs, forming oxyhemoglobin. As blood passes through the capillaries, some of the oxyhemoglobin releases oxygen and become deoxyhemoglobin. 22
Carbon Dioxide Transport by the Blood 23