ORAL CAVITY-2 This resource is licensed under the Creative Commons Attribution Non-Commercial & No Derivative Works License.

ORAL CAVITY-2 This resource is licensed under the Creative Commons Attribution Non-Commercial & No Derivative Works License

Objectives Recognise and describe a section through an enamel organ, identifying the main features and constituent tissues. Recognise and describe a section of the developing oral cavity (low power), distinguishing between the main structures and their organisation. Recognise and describe different cellular and extracellular components of the developing tooth (low power) appreciating their arrangement and any changes which occur during eruption. Distinguish and describe the characteristic main features of serous, mucous and mixed salivary glands (high power).

SLIDE 10/11 Head Identify at low magnification : Oral cavity. Tongue.
Eyes. Developing nasal cavity. Mandible. Other bones of skull. Developing enamel organs. Developing brain. 1.0 mm

SLIDE 10/11 Head Identify at low magnification : Oral cavity. Tongue.
Eyes. Developing nasal cavity. Mandible. Other bones of skull. Developing enamel organs. Developing brain. 8 6 6 4 3 3 1 7 7 2 5 5 1.0 mm

/11 Head At a higher magnification identify developing teeth and developing mandible. 250 µm

/11 Head At a higher magnification identify developing teeth and developing mandible. T : developing teeth B : bone of mandible T oral cavity T B tongue 250 µm

SLIDE 10/11 Head Identify : 1. Position of dental lamina.
Inner and outer epithelium. Stellate reticulum. Dental papilla. 100 µm

SLIDE 10/11 Head Identify : 1. Position of dental lamina.
Inner and outer epithelium. Stellate reticulum. Dental papilla. oral cavity dental lamina S outer epithelium D mandible inner epithelium S : stellate reticulum D : dental papilla 100 µm

What are the main constituent tissues of an enamel organ?
SLIDE 10/11 Head What are the main constituent tissues of an enamel organ? 50 µm

What are the main constituent tissues of an enamel organ?
SLIDE 10/11 Head What are the main constituent tissues of an enamel organ? What are the main constituent tissues of an enamel organ? Outer epithelium. Stellate reticulum. Inner epithelium which becomes the enamel secreting ameloblast layer. dental lamina outer epithelium S : stellate reticulum S inner epithelium cells elongate becoming ameloblasts dental papilla 50 µm

What type of tissue is stellate reticulum?
SLIDE 10/11 Head What type of tissue is stellate reticulum? dental lamina outer epithelium S : stellate reticulum S inner epithelium cells elongate becoming ameloblasts dental papilla 50 µm

SLIDE 10/11 Head What type of tissue is stellate reticulum?
Stellate reticulum consists of star shaped cells lying between the outer and inner epithelial layers; it has the appearance of connective tissue but is of epithelial derivation. dental lamina outer epithelium S : stellate reticulum S inner epithelium cells elongate becoming ameloblasts dental papilla 50 µm

In the lower jaw identify Meckel’s cartilage.
SLIDE 10/11 Head In the lower jaw identify Meckel’s cartilage. 1.0 mm 250 µm

In the lower jaw identify Meckel’s cartilage.
SLIDE 10/11 Head In the lower jaw identify Meckel’s cartilage. oral cavity tongue E 1.0 mm E : enamel organ Meckel’s cartilage developing mandible 250 µm

What is the origin and function of Meckel’s cartilage?
SLIDE 10/11 Head What is the origin and function of Meckel’s cartilage? 100 µm

What is the origin and function of Meckel’s cartilage?
SLIDE 10/11 Head What is the origin and function of Meckel’s cartilage? The lower jaw is formed in the embryo of cartilage. This cartilage does not undergo ossification, but acts as a model for the deposition of bone from surrounding connective tissue. This cartilage (Meckel’s cartilage) is later resorbed. What is the origin and function of Meckel’s cartilage? Meckel’s cartilage developing mandibular bone 100 µm

/11 Head What is the most prominent feature of the mandibular bone closest to the developing enamel organ? 100 µm 25 µm

/11 Head What is the most prominent feature of the mandibular bone closest to the developing enamel organ? The presence of osteoclasts (giant multinucleated cells derived from monocytes) involved in the resorption of matrix in bone re-modelling. What is the most prominent feature of the mandibular bone closest to the developing enamel organ? B : mandibular bone B osteoclasts B 25 µm

SLIDE 12 Developing molars
At low magnification identify the position of the molar teeth and the labio-gingival groove within the oral cavity. 1.0 mm

At low magnification identify the position of the molar teeth and the labio-gingival groove within the oral cavity. L : labio-gingival groove M : molars M M L oral cavity L tongue M M 1.0 mm

Select a developing tooth sectioned to show most areas from crown to root. 1.0 mm 0.5 mm

Identify : ameloblasts enamel dental papilla odontoblasts gingival epithelium dentine underling alveolar bone 250 µm

Identify : ameloblasts enamel dental papilla odontoblasts gingival epithelium dentine underling alveolar bone gingival epithelium ameloblasts enamel dentine odontoblasts dental papilla alveolar bone 250 µm

At a higher magnification, examine the tooth germ and identify the position of : a). ameloblasts c). enamel. b). odontoblasts d). dentine. 100 µm

At a higher magnification, examine the tooth germ and identify the position of : a). ameloblasts c). enamel. b). odontoblasts d). dentine. A A : ameloblasts B : odontoblasts C : enamel D : dentine C D B 100 µm

Describe the shape and organisation of ; ameloblasts odontoblasts. 50 µm

Describe the shape and organisation of ; ameloblasts A single layer of very long columnar cells, hexagonal in cross section, with elongated basally sited nuclei. odontoblasts. Single layer of elongated columnar cells, at dentine-pulp border. Describe the shape and organisation of ; ameloblasts odontoblasts. ameloblasts enamel dentine odontoblasts 50 µm

What is synthesised by a). ameloblasts? b). odontoblasts? 25 µm

What is synthesised by a). ameloblasts? b). odontoblasts? What is synthesised by a). ameloblasts? Enamel. b). odontoblasts? Dentine. ameloblasts D E E : enamel D : dentine odontoblasts 25 µm

From which type of tissue are a). ameloblasts derived? b). odontoblasts derived? 25 µm

From which type of tissue are a). ameloblasts derived? Epithelium. b). odontoblasts derived? Mesenchyme. 25 µm

In this picture taken under oil immersion identify the position of Tome’s fibres. What are they? 25 µm

In this picture taken under oil immersion identify the position of Tome’s fibres. What are they? Prismatic extensions of apical cytoplasm. Enamel forming secretions pass through these processes. The ameloblasts move backwards as the enamel layer is secreted. In this picture taken under oil immersion identify the position of Tome’s fibres. What are they? ameloblasts Tome’s processes enamel 25 µm

SLIDE 13 Developing incisors
How do the apical surfaces of this developing incisor tooth differ from the molar? apical portion of incisor longitudinal section of incisor 0.5 mm 250 µm

How do the apical surfaces of this developing incisor tooth differ from the molar? The crown of the incisor has only a single cusp, whereas that of the molar may have four, assisting in the grinding of food. apical portion of incisor longitudinal section of incisor 0.5 mm 250 µm

A view towards the root of the incisor. Note the reduced height of ameloblast, odontoblast and matrix layers towards the distal end. 0.5 mm 250 µm

Identify any spaces between the distinct layers of the developing tooth which you consider to be artefacts. 0.5 mm

Identify any spaces between the distinct layers of the developing tooth which you consider to be artefacts. A2 A1 0.5 mm Traces of enamel can be seen, arrowed, but some has been lost during specimen preparation leaving space artefacts A1. Other artefacts A2 can be seen close to the alveolar bone.

Does : a). dentine contain cells? b). enamel contain cells? 100 µm

Does : a). dentine contain cells? No % mineral and 30% collagen and glycoproteins. b). enamel contain cells? No. Composed of crystalline enamel rods. Does : a). dentine contain cells? b). enamel contain cells? ameloblasts enamel (traces of) dentine odontoblasts 100 µm

What term best describes the process of tooth growth. Is it appositional or interstitial? 50 µm

What term best describes the process of tooth growth. Is it appositional or interstitial? Appositional. A : space artefact enamel layer indistinct A A ameloblasts dentine odontoblasts dental papilla 50 µm

What is the position of cells most active in the process of matrix synthesis and how do they differ in shape and organisation from cells nearer the proximal end of the tooth? 0.5 mm 50 µm

What is the position of cells most active in the process of matrix synthesis and how do they differ in shape and organisation from cells nearer the proximal end of the tooth? The thickest layers of enamel and dentine (matrix synthesis) are seen at the proximal end of the tooth. Ameloblasts and odontoblasts cells situated towards this proximal end, become more elongated, an indication of greater synthetic activity. What is the position of cells most active in the process of matrix synthesis and how do they differ in shape and organisation from cells nearer the proximal end of the tooth? ameloblasts 0.5 mm enamel remnants space artefact dentine odontoblasts 50 µm

Dog head – lateral view ▪ Lower lip removed. Upper lip partially removed, remainder everted to expose partially pigmented labial mucosa. Platysma m. (m. cutaneous facei) partially removed. ▪ Identify : m. temporalis, m. masseter, pinna, auricular cartilage partially covered by parotid salivary gland, mandibular salivary gland, mandibular lymph node, cornea, body of mandible, gingivae, incisor, premolar and molar teeth of upper and lower jaw (which teeth are the carnassials?), root of tongue, parotid duct, (where does this open in the oral cavity?), rami buccales et zygomaticus of facial n, (what structures do these nerves innervate?), spinal n. C2.

SLIDE 14 Serous salivary gland (mouse)
Whole section viewed at low magnification. This section also includes some lymphatic tissue. Make sure you can distinguish this. 1.0 mm

Whole section viewed at low magnification. This section also includes some lymphatic tissue. Make sure you can distinguish this. SG SG : salivary gland L : lymphatic tissue L 1.0 mm

Identify : connective tissue capsule, septa; dividing the parenchyma into lobes. duct system. 250 µm

Identify : connective tissue capsule, septa; dividing the parenchyma into lobes. duct system. adipocytes ducts capsule septa lobule lymph node 250 µm

An area from the previous section showing elements of the duct system. Ducts running in the connective tissue septum are termed interlobular ducts. Ducts running within the lobules are termed intralobular ducts. 100 µm

An area from the previous section showing elements of the duct system. Ducts running in the connective tissue septum are termed interlobular ducts. Ducts running within the lobules are termed intralobular ducts. B A : interlobular ducts B : intralobular ducts B A A 100 µm

What epithelium lines the interlobular ducts? 50 µm

What epithelium lines the interlobular ducts? Interlobular ducts : lined by cuboidal to columnar epithelium. What epithelium lines the interlobular ducts? acini of gland intralobular duct blood vessel interlobular ducts septum 50 µm

What epithelium lines intralobular ducts? 50 µm

What epithelium lines intralobular ducts? Striated intralobular ducts lined with cuboidal epithelium. Intercalated intralobular ducts lined with low cuboidal to simple squamous epithelium. What epithelium lines intralobular ducts? striated duct intercalated duct 50 µm

Serous acini : secrete a watery solution rich in proteins. : the cells typically are cuboidal, pyramidal or crescent shaped. : nuclei are spherical and the cytoplasm stains well with H&E stain. 25 µm

SLIDE 16 Mucous salivary gland
Viewed at low magnification this lobed gland is pale staining. The outer connective tissue capsule is visible and large interlobular ducts can be identified. 1.0 mm

Viewed at low magnification this lobed gland is pale staining. The outer connective tissue capsule is visible and large interlobular ducts can be identified. lobules interlobular septum capsule interlobular ducts 1.0 mm

The lobes of the gland contain pale staining mucous acini and intralobular ducts . Large interlobular ducts can be seen in the connective tissue septum. 250 µm

The lobes of the gland contain pale staining mucous acini and intralobular ducts . Large interlobular ducts can be seen in the connective tissue septum. capsule 250 µm intralobular ducts pale staining mucous acini thick connective tissue septum with interlobular ducts and blood vessels

Thick connective tissue septum between the lobules. Identify : interlobular duct. blood vessels. 100 µm

Thick connective tissue septum between the lobules. Identify : interlobular duct. blood vessels. ID : interlobular duct A : arteriole V : venule septum ID A mucous acini V 100 µm

Within the lobules can be seen the striated intralobular ducts. Intercalated ducts are numerous but difficult to see in sections. striated duct 50 µm

Mucous acini : produce a mucous secretion, a viscous mix of glycoproteins. : cuboidal cells filled with mucous droplets giving a ‘foamy’ appearance. : the nucleus is displaced and flattened near the base of the cell. : mucous cells only stain faintly. 25 µm

The next three pictures are of the smaller of the two sections to be found on slide 16. This section is also from a mucous salivary gland and has been stained so that the mucous secreting cells stain blue whilst the duct system has stained orange. 1.0 mm

Identify : capsule connective tissue septa interlobular ducts intralobular ducts 250 µm

Identify : capsule connective tissue septa interlobular ducts intralobular ducts septum between lobules intralobular ducts interlobular ducts capsule 250 µm

High magnification showing the striated intralobular ducts stained orange. intralobular duct mucous acinus 25 µm

SLIDE 15 Mixed salivary gland
Very low magnification view showing most of the section on slide 15. The lobes of the gland are visible with large interlobular ducts and blood vessels running in the connective tissue. The mucous acini again stain lightly. A : area of blood vessels and interlobular ducts A connective tissue septum A 1.0 mm

In this picture taken with the x10 objective, the gland looks quite similar to the mucous secreting salivary gland seen in slide 16 with pale staining acini consisting of cells with a ‘foamy’ appearance. 250 µm

At the next magnification : A thick interlobular connective tissue septum is present. Within the lobule some intralobular ducts can be identified. 100 µm

At the next magnification : A thick interlobular connective tissue septum is present. Within the lobule some intralobular ducts can be identified. connective tissue septum intralobular striated ducts pale staining mucuos acini 100 µm

At a higher magnification : The ‘foamy’ appearance of the mucous cells is evident and the darker staining serous cells can be seen around the outside of the acini. 50 µm

At high magnification most of the mucous acini can be seen to have associated with them darker staining crescent shaped serous cells (serous demi-lunes). 25 µm

At high magnification most of the mucous acini can be seen to have associated with them darker staining crescent shaped serous cells (serous demi-lunes). flattened basal nuclei of mucous cells mucous acinus serous demi-lune 25 µm

Another high magnification view of acini from a mixed gland. Note the capillaries running in the connective tissue between these acini. 25 µm

Another high magnification view of acini from a mixed gland. Note the capillaries running in the connective tissue between these acini. serous demi-lunes Capillaries (easily recognisable from the presence of pink/red staining erythrocytes) 25 µm

Lectures : Oral Cavity. Dr A.Pitsillides.
Lectures : Salivary Glands. Prof N.Stickland. Second Year Histology ORAL CAVITY J.Bredl Gross Anatomy Correlates. Dr S.Frean. Slides and Stains. Tanya Hopcroft. Compressed version /6/7.

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ORAL CAVITY-2 This resource is licensed under the Creative Commons Attribution Non-Commercial & No Derivative Works License.

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