Presentation on theme: "15. Mouth, teeth, pharynx. Fig. 16.1 Liem, Bemis, Walker & Grande. In Deuterostomes, mouth forms where the archenteron meets the stomodeum (a fold in."— Presentation transcript:
15. Mouth, teeth, pharynx
Fig Liem, Bemis, Walker & Grande. 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.
Pharynx performs respiratory and digestive system functions
The pharynx is the major respiratory structure in early vertebrates. Water high in O 2 and low in CO 2 enters pharynx via mouth and / or spiracle This water is forced across gills and out external gill slits Blood low in O 2 and high in CO 2 is pumped into gills where gas exchange takes place What mechanism makes gases move from water to blood or blood to water? Diffusion gradient
Walker and Homberger The pharynx is highly vascularized to allow it to function in respiration.
13 = hard palate 28 = soft palate palate separates respiration from ingestion 24 = oral cavity but systems cross paths in the pharynx 8= esophagus 33= trachea 27 = nasal cavity 21= vomero- nasal opening
a primary palate – primitive condition for Choanata a primary palate – Still present in Dermochelys Crocodilians evolve A long secondary Palate, as in Alligator a short secondary palate is present in Some turtles Synapsids evolve A long secondary Palate, as in Homo and Canis Surrounds Internal nares
Fig Walker and Homberger – The larynx of the cat A. Longitudinal section – cartilages only B. Lateral view of the laryngeal and tracheal cartilages C. Lateral view of the laryngeal muscles with hyoid added
Walker and Homberger Fig Muscles of the pharyngeal region
Walker and Homberger (thyroid cartilage)
Marieb Tongue – modified hypobranchial muscle anchored by hyoid apparatus Tongue function: 1- food handling 2- taste buds 3- move scent to vomeronasal organ 4- prey capture 5- grooming 6- speech Lingual or glossal refers to tongue Genio refers to chin = Adams apple Mastoid process
Marieb Superior esophageal sphincter Superior esophageal sphincter Function of epiglottis
Basic Terms Used for Feeding Mechanisms of Vertebrates 1. Suspension-feeding (= filter-feeding) - filter small particles (alive or dead, depending on species) out of water column 2. Suction-feeding - open mouth, suck in food 3. Ram-feeding - open mouth, swim over food Ram-Suction Index - compares movement of food relative to movement of feeder 4. Inertial-feeding - inertia of food is used to move it in oral cavity 5. 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 chewing Liem, Bemis, Walker & Grande.
Mastication requires teeth Primitively homodont, and non-occlusal With a variety of tooth attachment types and tooth replacement modes
Some 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 jaw Heterodont - teeth of different shape along the jaw Tooth 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.
Types of Mammalian Teeth and Dental Formulae Incisor teeth (I), typically these are replaced Canine teeth (C), typically these are replaced Premolar teeth (P), typically these are replaced Molar teeth (M), typically these are not replaced Formulae are expressed as type # in upper jaw/# in lower jaw I 5/4, C 1/1, P 2/2, M 4/4 = opossum I 2/2, C 1/1, P 2/2, M 3/3 = humans Liem, Bemis, Walker & Grande. Heterodonty has produced four tooth types:
Fig Carnassial Pair: P4-M1 Liem, Bemis, Walker & Grande. Montre moi vos dents, et je vous dit que vous est