Comparative Vertebrate Anatomy Lecture Notes - Respiratory System PDF

Comparative Vertebrate Anatomy Lecture Notes - Respiratory System Respiration is the process of obtaining oxygen from the external environment & eliminating CO2.  External respiration - oxygen and carbon dioxide exchanged between the external environment & the body cells  Intern...

Comparative Vertebrate Anatomy Lecture Notes - Respiratory System Respiration is the process of obtaining oxygen from the external environment & eliminating CO2.  External respiration - oxygen and carbon dioxide exchanged between the external environment & the body cells  Internal respiration - cells use oxygen for ATP production (& produce carbon dioxide in the process) Adaptations for external respiration: 1 - Primary organs in adult vertebrates are external & internal gills, swim bladders or lungs, skin, & the buccopharyngeal mucosa 2 - Less common respiratory devices include filamentous outgrowths of the posterior trunk & thigh (African hairy frog), lining of the cloaca, & lining of esophagus Respiratory organs:  Cutaneous respiration o respiration through the skin can take place in air, water, or both o most important among amphibians (especially the family Plethodontidae)  Gills (see Respiration in Fishes) o Cartilaginous fishes:  5 ‘naked’ gill slits  Anterior & posterior walls of the 1st 4 gill chambers have a gill surface (demibranch). Posterior wall of last (5th) chamber has no demibranch.  Interbranchial septum lies between 2 demibranchs of a gill arch  Gill rakers protrude from gill cartilage & ‘guard’ entrance into gill chamber  2 demibranchs + septum & associated cartilage, blood vessels, muscles, & nerves = holobranch o Bony fishes (teleosts): (See 'Ventilation in Teleost Fishes')   usuall y have 5 gill slits  operc ulum proje cts back ward over gill cham bers  interb ranch ial septa are very short or absent o Agnathans:  6 - 15 pairs of gill pouches  pouches connected to pharynx by afferent branchial (or gill) ducts & to exterior by efferent branchial (or gill) ducts  Larval gills: o External gills  outgrowths from the external surface of 1 or more gill arches  found in lungfish & amphibians o Filamentous extensions of internal gills  project through gill slits  occur in early stages of development of elasmobranchs o Internal gills - hidden behind larval operculum of late anuran tadpoles Swim bladder & origin of lungs - most vertebrates develop an outpocketing of pharynx or esophagus that becomes one or a pair of sacs (swim bladders or lungs) filled with gases derived directly or indirectly from the atmosphere. Similarities between swim bladders & lungs indicate they are the same organs. Vertebrates without swim bladders or lungs include cyclostomes, cartilaginous fish, and a few teleosts (e.g., flounders and other bottom-dwellers). Swim bladders:  may be paired or unpaired (see diagram above)  have, during development, a pneumatic duct that usually connects to the esophagus. The duct remains open (physostomous) in bowfins and lungfish, but closes off (physoclistous) in most teleosts.  serve primarily as a hydrostatic organ (regulating a fish's specific gravity)  gain gas by way of a 'red body' (or red gland); gas is resorbed via the oval body on posterior part of bladder   may also play important roles in: o hearing - some freshwater teleosts (e.g., catfish, goldfish, & carp) 'hear' by way of pressure waves transmitted via the swim bladder and small bones called Weberian ossicles (see diagram below) o sound production - muscles attached to the swim bladder contract to move air between 'sub-chambers' of the bladder. The resulting vibration creates sound in fish such as croakers, grunters, &midshipman fish. o respiration - the swim bladder of lungfish has number subdivisions or septa (to increase surface area) & oxygen and carbon dioxide is exchanged between the bladder & the blood Source: http://www.notcatfish.com/ichthyology/weberian_apperatus.htm Lungs & associated structures  Larynx o Tetrapods besides mammals - 2 pair of cartilages: artytenoid & cricoid o Mammals - paired arytenoids + cricoid + thyroid + several other small cartilages including the epiglottis (closes glottis when swallowing) o Amphibians, some lizards, & most mammals - also have vocal cords stretched across the laryngeal chamber  Source: http://www.worldzone.net/music/singingvoice/images/glottis.gif  Trachea & syrinx o Trachea  usually about as long as a vertebrates neck (except in a few birds such as cranes)  reinforced by cartilaginous rings (or c-rings)  splits into 2 primary bronchi &, in birds only, forms the syrinx at that point  Lungs o Amphibian lungs  2 simple sacs  internal lining may be smooth or have simple sacculations or pockets  air exchanged via positive-pressure ventilation o Reptilian lungs  simple sacs in Sphenodon & snakes  Lizards, crocodilians, & turtles - lining is septate, with lots of chambers & subchambers  air exchanged via positive-pressure ventilation o Avian lungs - modified from those of reptiles:  air sacs (diverticula of lungs) extensively distributed throughout most of the body  arrangement of air ducts in lungs ----> no passageway is a dead- end  air flow through lungs (parabronchi) is unidirectional o Mammalian lungs:   multichambered & usually divided into lobes  air flow is bidirectional: Trachea primary bronchi secondary bronchi tertiary bronchi bronchioles alveoli  air exchanged via negative pressure ventilation, with pressures changing due to contraction & relaxation of diaphragm & intercostal muscles