Palate Hard palate – anterior portion of mouth’s roof; formed by maxillae and palatine bones Soft palate – posterior portion of mouth's roof; formed by two muscular arches: Palatoglossal arch - extends from palate to tongue anterior to palatine tonsils Palatopharyngeal arch - extends from palate to pharyngeal wall posterior to palatine tonsil

Figure 24.5 Structures of the mouth (oral cavity)

Salivary Glands General Saliva Functions: Keeps the oral and pharyngeal mucous membranes moist. Lubricates and dissolves food. Starts carbohydrate chemical digestion. Most saliva is secreted by salivary glands. Some saliva comes from buccal glands in the mucous membrane that lines the mouth. Minor salivary glands include labial, buccal, lingual and palatal glands which make a small contribution to saliva.

Salivary Glands Outside the mouth  ducts  oral cavity Parotid glands - below ear, over masseter; parotid ducts open into vestibule beside 2nd maxillary molar. Submandibular glands - under mandible; submandibular ducts open lateral to lingual frenulum Sublingual glands - floor of mouth deep to tongue; lesser sublingual ducts open into floor of mouth

Figure 24.6 The three major salivary glands – parotid, sublingual, and submandibular

Salivary Glands Salivary gland cells are organized into acini. Acini: small saclike cavities (clusters) in a gland surrounded by secretory cells. Serous acini - secrete a watery fluid Mucous acini - secrete a slimy, mucus secretion Parotid glands – serous acini only Submandibular glands – mostly serous acini and a few mucous acini Sublingual glands - mostly mucous acini and a few serous acini

Figure 24.6b Histology of the submandibular gland

Composition and Functions of Saliva 99.5% water 0.5% solutes (salts, gases, mucous, ions, enzymes, lysozyme, IgA) Functions: Lubricate food for easier swallowing Dissolve food for tasting Moistens mucous membranes Bicarbonate ions buffer acidic foods Salivary amylase begins chemical digestion of starch (maltose) Lysozyme  antibacterial IgA  1st line of defense

Salivation The secretion of saliva. Salivation is under ANS control Moistens mucous membranes Assists speech Almost all salivary components are reabsorbed Dehydration – conserve water by not producing saliva

Salivation Increase salivation Sight, smell, sounds, thoughts/memory. Tongue stimulation  taste buds Salivatory nuclei in brainstem increase salivation Parasympathetic nerve impulses stimulate saliva Facial (VII) and glossopharyngeal (IX) nerves. Stop salivation Sympathetic nerves inhibit salivation

Tongue Composed of skeletal muscle covered with mucous membrane. Forms oral cavity’s floor. Participates in chewing, swallowing, and speech. Glands on tongue’s dorsum secrete lingual lipase

Tongue Lingual frenulum - attaches tongue to mouth’s floor Tongue-tied Ankyloglossia Abnormally short frenulum Speech impediment Can be surgically repaired

Tongue Papillae cover upper surface (dorsum) and sides. Projections of lamina propria Some contain taste buds

Figure 11.7 Muscles that Move the Tongue - FYI

Teeth Project into the mouth Alveolar processes of mandible and maxilla Covered by gingivae

Teeth Fibrous connective tissue Anchor Shock absorber Adapted for mechanical digestion. A typical tooth consists of crown, neck, and root. Composed primarily of dentin, which encloses the crown’s pulp cavity the roots’ root canals. Root’s dentin is covered by cementum Cementum attaches root to periodontal ligament Fibrous connective tissue Anchor Shock absorber

Figure 24.7 A typical tooth and surrounding structures Talk about the four things highlighted as those haven’t been mentioned yet through notes.

Tooth Types Incisors – chisel shaped; cutting Cuspids (canines) – pointed; tearing Premolars – bicuspid; crushing and grinding Molars – four cusps; crushing and grinding

Dentition There are two sets of teeth in an individual’s lifetime: Deciduous (primary) teeth 20 teeth that start erupting at 6 months Permanent (secondary) teeth 32 teeth that erupt between 6 and 12 years of age

Figure 24.8 Deciduous (primary) dentition and times of eruptions

Figure 24.8b Permanent (secondary) dentition and times of eruptions

Digestion in the Mouth Mechanical digestion (mastication or chewing) Breaks into pieces Mixes with saliva  bolus Chemical digestion Amylase Begins starch digestion at pH of 6.5 or 7.0 found in mouth When bolus & enzymes hit the pH of 2.5 (gastric juices), hydrolysis ceases Lingual lipase Secreted by glands in tongue Begins breakdown of triglycerides into fatty acids and glycerol once it reaches the acidic pH in the stomach

PHARYNX

Pharynx “Throat” – but don’t call it that… Figures 23.2 / 24.10 Pharynx “Throat” – but don’t call it that… Funnel-shaped tube extending from internal nares to the esophagus and larynx Skeletal muscle lined by mucous membrane. 3 parts: Nasopharynx – only respiratory fnc Oropharynx – digestive and respiratory fnc Laryngopharynx – digestive and respiratory fnc

Figure 23.2 The pharynx

Pharynx Deglutition or swallowing is facilitated by saliva and mucus Starts when bolus is pushed into the oropharynx Sensory nerves send signals to deglutition center in brainstem Soft palate is lifted, epiglottis is bent Ingested food  mouth  oropharynx  laryngopharynx  muscular contractions  esophagus  stomach

ESOPHAGUS

Esophagus Secrete mucus and transport food to the stomach. Figure 24.1 Esophagus Secrete mucus and transport food to the stomach. Collapsible muscular tube = flexible In front of vertebrae Posterior to trachea Posterior to the heart Connects pharynx to stomach Pierces diaphragm at hiatus