2The pharynx forms just posterior to that point. In Deuterostomes, mouth forms where the archenteron meets the stomodeum (a fold in ectoderm).The pharynx forms just posterior to that point.Early in ontogeny and phylogeny it has associated gill structures.Fig. 16.1Liem, Bemis, Walker & Grande.
4The pharynx is the major respiratory structure in early vertebrates. Water high in O2 and low in CO2 enters pharynx via mouth and / or spiracleThis water is forced across gills and out external gill slitsBlood low in O2 and high in CO2 is pumped into gills where gas exchange takes placeWhat mechanism makesgases move from water toblood or blood towater?Diffusion gradient
5Walker and Homberger The pharynx is highly vascularized to allow it to function in respiration.Walker and Homberger
6palate separates respiration from ingestion but systems cross paths 8= esophagus13 = hard palate33= trachea28 = soft palate21= vomero-nasal opening24 = oral cavity27 = nasal cavitypalate separatesrespiration fromingestionbut systemscross pathsin the pharynx
8a primary palate – primitive condition for Choanata a shortsecondarypalate ispresent inSome turtlesCrocodilians evolveA long secondaryPalate, as inAlligatora primary palate –Still present inDermochelysSynapsids evolveA long secondaryPalate, as inHomo and CanisSurroundsInternal naresa primary palate – primitive condition for Choanata
9A. Longitudinal section – cartilages only Fig Walker and Homberger– The larynx of the catA. Longitudinal section – cartilages onlyB. Lateral view of the laryngeal and tracheal cartilagesC. Lateral view of the laryngeal muscles with hyoid added
10Walker and HombergerMuscles of the pharyngeal regionFig. 7-20
12Tongue – modified hypobranchial muscle anchored by hyoid apparatus Tongue function:1- food handling2- taste buds3- move scent tovomeronasal organ4- prey captureMastoidprocess5- grooming6- speechLingual or glossal refers to tongueGenio refers to chin= Adam’s appleMarieb
13Function of epiglottis SuperioresophagealsphincterSuperioresophagealsphincterFunction of epiglottisMarieb
14Basic Terms Used for Feeding Mechanisms of Vertebrates 1. Suspension-feeding (= filter-feeding) - filter small particles (alive or dead, depending on species) out of water column2. Suction-feeding - open mouth, suck in food3. Ram-feeding - open mouth, swim over foodRam-Suction Index - compares movement of food relative to movement of feeder4. Inertial-feeding - inertia of food is used to move it in oral cavity5. Transport - movement of food within oral cavity (by water currents in aquatic vertebrates or tongue in tetrapods)6. Mastication - physical reduction of food size by chewingLiem, Bemis, Walker & Grande.
15Mastication requires teeth Primitively homodont, and non-occlusalWith a variety of tooth attachment typesand tooth replacement modes
16Some Important Terms for Teeth Polyphyodont - multiple generations of tooth replacement (most vertebrates)Diphyodont - two sets of teeth: milk and permanent (most mammals; incisor, canine and premolar teeth are replaced)Monophyodont - a single set of teeth (e.g., cetaceans)Homodont - teeth of similar shape along jawHeterodont - teeth of different shape along the jawTooth plate or Toothplate - at least two uses are common:1. Many individual teeth fused together at their bases; separate cusps are still visible (e.g., in pharynx of fishes)2. Fusion of individual teeth during ontogeny: separate cusps may not still be visible (e.g., lungfishes, chimaeras)Liem, Bemis, Walker & Grande.
17Types of Mammalian Teeth and Dental Formulae Heterodonty has produced four tooth types:Types of Mammalian Teeth and Dental FormulaeIncisor teeth (I), typically these are replacedCanine teeth (C), typically these are replacedPremolar teeth (P), typically these are replacedMolar teeth (M), typically these are not replacedFormulae are expressed as type # in upper jaw/# in lower jawI 5/4, C 1/1, P 2/2, M 4/4 = opossumI 2/2, C 1/1, P 2/2, M 3/3 = humansLiem, Bemis, Walker & Grande.
18Carnassial Pair: P4-M1 “Montre moi vos dents, et je vous dit que vous est”Carnassial Pair: P4-M1Fig. 16.6Liem, Bemis, Walker & Grande.