Histology of the Oral Cavity, Lip & Tongue PDF

Histology of oral cavity, lip and tongue By: Dr. Moustafa Al Sawy Dr. Shaimaa Mohamed Amer MBBCH, M.SC. M.D HISTOLOGY MBBCH, M.SC. M.D HISTOLOGY Associate Professor of Histology &...

Histology of oral cavity, lip and tongue By: Dr. Moustafa Al Sawy Dr. Shaimaa Mohamed Amer MBBCH, M.SC. M.D HISTOLOGY MBBCH, M.SC. M.D HISTOLOGY Associate Professor of Histology & Cell Biology Associate Professor of Histology & Cell Biology Certified Medical Educator  Learning objectives Knowledge : Learning Objectives At the end of the lecture , the student will be able to: 1.Describe the histological structure of oral cavity, lip & tongue. 2.List lingual papillae and mention characteristic histological features & functions of each.  The Digestive System The digestive system includes the alimentary tract and secretory organs. The alimentary tract is divided into three functional parts : 1-Oral cavity: consists of lips, cheeks, tongue, teeth and gums. 2-Simple passages: (oropharynx, esophagus & anal canal). For transport of food or its residue from one part to another with minimal metabolic activity. 3-Digestive tract: (stomach, Small intestine & Large intestine). For digestion & absorption of food. The secretory organs: include salivary glands, pancreas and liver.  The oral cavity *The oral cavity is lined with non-keratinized stratified squamous epithelium. Except: Had palate and gingiva: Stratified squamous keratinized Dorsum of tongue: Stratified squamous partially keratinized Red margin of lip: Stratified squamous with very thin keratin *The roof of the mouth consists of hard palate anteriorly and soft palate posteriorly. The soft palate has a core of skeletal muscle and numerous glands in its submucosa. *The palatine uvula is a small conical process which extends downward from the soft palate having the same structure of the soft palate. The gum (gingiva) surrounds each tooth and attached directly to the periosteum of alveolar bone.  The lip (wedge shaped) *It is made of central core of skeletal muscle fibers arranged in different directions. *Its outer surface is covered by thin skin formed of epidermis and dermis containing hair follicles, sweat and sebaceous glands. *Its internal surface is lined by a mucous membrane (epithelium & corium). The epithelium of the internal surface is non keratinized stratified squamous, and corium is loose connective tissue having muco-serous glands( the labial glands).  The lip The Red Margin (Vermillion zone) of the lip: *It is a transitional zone between skin& mucous membrane. *It is covered by modified skin (with thin keratin) with no hair follicles, sweat or sebaceous glands. *The C.T. dermis forms deep papillae that contain numerous blood capillaries responsible for the pinkish red color of lip. *It is rich in nerve endings rendering the lip very sensitive.  Lip Skin epidermis dermis Red Muscles margin corium labial glands epithelium Mucous membrane  The tongue *It is a muscular organ, made of a core of striated muscle fibers, arranged in three directions (longitudinal, horizontal & vertical). *The mucous membrane, covering the surface of the tongue, is made of a C.T. corium (lamina propria) strongly adherent to the muscle and is covered by stratified squamous epithelium. *The dorsal surface of the tongue is rough due to the presence of lingual papillae and is divided into an anterior 2/3 and a posterior 1/3 by an inverted V – shaped depression (sulcus terminalis). While the ventral surface of the tongue is smooth.  Lingual Papillae Definition: They are projections of the mucous membrane, on the dorsum of the tongue, present only on the anterior 2/3 of the dorsum. Structure: They are made of a central core of C.T., covered by stratified squamous epithelium (some keratinized and some non). Types: There are 4 types in the tongue: 1.Conical (Filiform). 2.Fungiform. 3. Circumvallate. 4.Foliate.  Lingual Papillae 1- Conical (Filiform) Papillae: They are numerous, highly keratinized, conical in shape with no taste buds cover the anterior 2/3 of dorsum of the tongue. 2-Fungiform Papillae: *They are scattered between the conical especially on the margin of the tongue. *They are rounded, with a basal constriction. Their C.T. core is highly vascular. They have few taste buds.  Lingual Papillae 3- Circumvallate Papillae: *They are found along V-shaped line of the dorsum of the tongue at the junction between the anterior 2/3 & posterior 1/3. *They are few in number about 8-12 in number. *They are large and rounded with constricted bases. *They have numerous taste buds & serous Von Ebner’s glands which are accessory salivary glands. *Their ducts open into the trenches, around the circumvallate papillae.  Lingual Papillae 4- Foliate Papillae: *They are formed of parallel ridges separated by deep grooves of C.T. covered by stratified squamous epithelium. *They have many taste buds. *They help licking of milk & watery materials. *They are present on posterior part of the tongue. *They are well developed in animals like rabbit and rudimentary in man. Lingual Papillae  Lingual Papillae Taste Sensations: *Taste may be detected regionally in the tongue without any structural differences in taste buds. *Sweet & Salty are detected at the tip of tongue. *Sour (Acids) are detected at the sides. *Bitter is detected in circumvallate papillae. Glands of the tongue: 1-Von-Ebner's glands are serous glands, found underneath the circumvallate papillae. 2- Mucous glands are present in the corium of the posterior part of the tongue. Lingual tonsils: They are masses of lymphoid tissue found in the mucous membrane of the posterior 1/3 of the dorsum of the tongue.  Taste Buds Def: They are neuroepithelial, pale , oval flask-shaped bodies, concerned with taste sensation. Site: They are found in papillae of tongue (fungiform, circumvallate & foliate), soft palate, pharynx & epiglottis. *They open on surface by gustatory pores.  Taste Buds Structure: 1-Gustatory or hair (taste) cells. They are long cells with microvilli project through gustatory (taste ) pore. Their basal parts have numerous vesicles & surrounded by fine (non-myelinated) sensory nerve fibers. 2-Sustentacular cells. They are supporting in function, have long microvilli and lightly stained nuclei , they may be two types. 3-Basal cells They are short, present at the base and act as stem cells for the previous types.  Gustatory pore Microvilli hair cells Basal cells Sensory NF Mechanism of taste sensation: Substance is dissolved in saliva passes to the pores, affects the microvilli of hair cells, initiating nerve impulse which is transmitted to brain. Taste Buds Taste Buds  Medical Application Carcinoma of the lip is the most common oral cavity malignancy, with almost 95% of cases being squamous cell carcinoma. Treatment involves equally effective surgical excision or radiation therapy, the choice depending on tumor size.  Medical Application Cleft palate (palatoschisis) is a common birth defects. It is resulting from failure of fusion of palatal plates in the roof of the mouth during early fetal development. It may be unilateral or bilateral, involving the soft palate only, or extending forward through the hard palate. Cleft lip (cheiloschisis), a fissure of the lip beneath the nostril in which the nasal cavity opens into the mouth. Treatment of clefts is based on the clinical severity and typically involves multiple surgeries from infancy to late adolescence to restore normal function and physical appearance.  Medical Application Immune defenses in the oral cavity cannot protect against all infections. Pharyngitis and tonsillitis are often due to the bacterium Streptococcus pyrogenes. White excrescences or leukoplakia on the sides of the tongue can be caused by Epstein-Barr virus. Oral thrush, a white exudate on the tongue’s dorsal surface, is due to a yeast (Candida albicans) infection and usually affects neonates or immunocompromised patients.  Medical Application Black hairy tongue: Often a result of poor oral hygiene, black hairy tongue is a condition where dead cells build up on the tongue’s surface to create a dark, furry-like appearance. Glossitis: A condition that results in a swollen, inflamed, or discolored tongue, glossitis can be caused by a number of factors. Oral thrush: Characterized by small white bumps and patches on the surface of the tongue, it is a yeast infection that can be treated with antifungal medication.  Case Scenario A 48-year-old man complains of painful ulcers in his mouth. Physical examination reveals multiple shallow ulcers covered by a fibrinopurulent exudate on the inner surface of the upper lip and cheek. The patient is subsequently diagnosed with aphthous stomatitis, an inflammation of the oral mucosa. Which of the following types of epithelium lines the internal aspect of lip ? (A) Keratinized stratified squamous (B) Nonkeratinized stratified squamous (C) Simple columnar (D) Simple squamous (E) Stratified columnar Any Questions? References: 1.Basic Histology: Text & Atlas. Editor: Luiz Carlos Junqueira, MD, PhD; Jose Carneiro, MD, PhD. 14th Ed. 2. Wheatear’s functional histology. A text & color atlas.15th Ed. 3.AMBOSS platform. Thank You