Chapter 2- salivary glands

Salivary Gland anatomy and histology

1. D R : Mohanad Rahman Alwan Anatomy of the Mouth (2) Q A P 2 0 7 0 4

2. The Tongue The tongue is a muscular organ in the mouth. It forms part of the floor of the oral cavity and part of the anterior wall of the oropharynx. The apex of tongue is anterior part in oral cavity and directly s its b ehind the incisor teeth The root of t o n gue is at t a che d t o th e mand i ble and the hyoid bone.

3. The Tongue It is covered with moist, pink tissue called mucosa. Tiny bumps called papillae give the tongue its rough texture. Thousands of taste buds cover the surfaces of the papillae. Ta s t e b u d s are collections of nerve-like cells that connect to nerves running into the brain.

4. The Tongue Its ventral surface is covered by non- keratinized stratified squamous epithelium and the dorsal surface is covered by various papillae.

5. Dorsal surface of tongue

6. Dorsal surface of tongue (oral part) The oral part of the tongue has a velvety appearance, since its mucous membrane is covered by small projections called Papillae. Most of papillae are pointed filiform papillae: look like “hooks” that are composed of hard keratinized epithelium. The fungiform papillae: Mushroom-shaped and slightly higher than surrounding filiform papillae. To the naked eye, they appear as red spots on the tongue, containing taste buds at their base. The circumvallate papillae are much larger than fungiform papillae, with numerous taste buds.

7. Dorsal surface of tongue (oral part)

8. Dorsal surface of tongue (pharyngeal part) The pharyngeal surface of the tongue lies just behind a row of very large vallate papillae which form the sulcus terminalis . The muco s a coveri n g the p h aryng e al surfac e of tongue is irregular contour because of the many small nodules of lymphoid tissue in the submucosa. These nodules are collectively the lingual tonsil

9. Dorsal surface of tongue

10. Dorsal surface of tongue

11. Muscles of the tongue The muscles of the tongue can be divided into: Extrinsic muscles Intrinsic muscles (allow for shape change with fibers in various directions) ( superior longitudinal, inferior longitudinal ,transverse and vertical muscles )

12. Extrinsic muscles of tongue There are four major extrinsic tongue muscles: Hyoglossus Styloglossus Genioglossus Palatoglossus

13. Muscles of the tongue Extrinsic muscles serve to move the tongue about in the oral cavity. Intrinsic muscles act to change the shape of the tongue.

14. Extrinsic muscles Muscle Origin Insertion Innervation Function Genioglossus Superior mental tubercles Body of hyoid; entire length of tongue Hypoglossal nerve [XII] Protrudes tongue; depresses center of tongue Hyoglossus Greater horn and adjacent part of body of hyoid bone Lateral surface of tongue Hypoglossal nerve [XII] Depresses tongue Styloglossus Styloid process (anterolateral surface) Lateral surface of tongue Hypoglossal nerve [XII] Elevates and retracts tongue Palatoglossus Inferior surface of palatine aponeurosis Lateral margin of tongue Vagus nerve [X] (via pharyngeal branch to pharyngeal plexus) Depresses palate; moves palatoglossal fold toward midline; elevates back of the tongue

15. Blood supply of tongue Arterial blood supply : The ma i n art ery is the w hich a e x t ern a l lingual artery branch of the carotid artery . Venous drainage Dorsal lingual and deep lingual veins.

16. Lymphatic of the tongue Tip of tongue to submental LN group. Rest of anterior 2/3 of tongue to submandibular LN group and deep cervical LN group Posrerior 1/3 of tongue to deep cervical LN group

17. Sensory innervations The anterior 2/3 of the tongue is carried by : The lingual nerve , a major branch of the mandibular nerve (a branch of the trigeminal nerve, (CN V) for general sensation. The chorda tympani (a branch of the facial nerve (CN VII) that runs in the lingual nerve) for taste.

18. Sensory innervations The posterior 1/3 of the tongue and the vallate papillae are supplied by the glossopharyngeal nerve (CN IX) for both general sensation and taste. Vagus Nerve (CN X)– Taste of Posterior Part Motor innervations Muscles of the tongue are innervated by the hypoglossal nerve ( the twelfth cranial nerve, (CN XII)

19. Sensation of Taste Structure of Taste Buds Each Taste Bud is a bundle of receptor cells. It contains about 40 cells which are the modified epithelial cells Cells are divided into 4 groups 1) Type 1 cells 2) Type 2 cells 3) Type 3 cells 4) Type 4 cells

20. Types of Taste Sweet Taste- Produced by Organic Substances like Monosaccharides, Polysaccharides, Glycerol, Aldehydes, Ketones. Salt Taste- Produced by Chlorides and Nitrates of Na, K & Ammonia. Sour Taste- Produced because of Hydrogen ions. • Bitter Taste- Produced due to organic substances like Strychnine, Morphine, Piric Acid, Bile Salts, Salts of Ca, Mg & Ammonium. • Umami - Produced due to Glutamate, particularly Monosodium Glutamate.

21. Pal a te Palate is a roof of the mouth; the partition separating the nasal and oral cavities. consisting of an anterior bony portion ( hard palate ) and a posterior muscular portion ( soft palate )

22. Pal a te Hard Palate (anterior 2/3) Bones : Maxilla ( P ala t ine processes + Palatine Bone) Assists the tongue in chewing

23. Pal a te Soft palate (posterior 1/3) Mobile fold formed mostly of skeletal muscle Closes off the nasopharynx during swallowing Uvula projects downward from its free edge

24. Salivary Glands The salivary glands are exocrine glands, glands with ducts, that produce saliva. They secrete amylase , an enzyme that breaks down starch into maltose.

25. Salivary Glands Three pairs of extrinsic glands: parotid, submandibular, and sublingual. Intrinsic salivary glands scattered throughout the oral mucosa (Nose, lip, buccal mucosa, palate, pharynx). > 400 minor salivary glands

26. Salivary Glands

27. Parotid Gland The parotid gland is found below the level of the external auditory canal, between the mandible and the   sternocleidomastoid Muscle. Parotid Duct Arises from anterior border 1.5 cm inferior to Zygomatic arch 4-6 cm in length

28. Submandibular Gland It is a salivary gland located beneath the floor of the mouth It lies along the medial aspect of the mandibular body It is hook shaped It is divided into superficial and deep lobes, which are separated by the mylohyoid muscle. Wharton’s duct: About 5cm in length.

29. Sublingual Glands They lie anterior to the submandibular gland under the tongue, beneath the mucous membrane of the floor of the mouth. sublingual gland is immediately lateral to the submandibular duct The ducts of the sublingual glands are called Bartholin’s ducts .

30. Blood Supply of Salivary Glands Blood Supply to the parotid gland originate from the external carotid artery. The submandibular and sublingual glands are supplied by branches of the facial and lingual arteries. Veins from the parotid gland drain into the external jugular vein, and those from the submandibular and sublingual glands drain into lingual and facial veins.

31. Functions Protection . lubricant (glycoprotein) Buffering ( phosphate ions and bicarbonate) Digestion Antimicrobial. L ysozyme hydrolyzes cell walls of some bacteria Maintenance of tooth integrity ( calcium and phosphate ions) Tissue repair . B bleeding time of oral tissues shorter than other tissues Taste. s olubilizing of food substances that can be sensed by receptors

32. Composition of Saliva: 97-99.5% water pH 6.75-7.0 Sodium, potassium, chloride, phosphate, and bicarbonate Mucin Salivary amylase

33. 39 Regulation of Salivary secretion Simple or unconditioned: The presence of food in the mouth results in reflex secretion of saliva. Stimulus: presence of food in the mouth. Receptors: taste buds. Afferent: nerves from taste buds carry impulses to salivary center. Centre: salivary center in medulla oblongata (in brain stem). Efferent: autonomic nerves supplying salivary glands.

34. CLASS ACTIVITY Draw a diagram shows Salivary glands nerves Innervations

35. Questions?