Mouth Anatomy: Tongue, Teeth and Palate

Mouth Cavity

• The mouth opens at the lips and connects to the throat.
• Boundaries are defined by lips, cheeks, hard and soft palates, and the glottis.
• Divided into two sections: vestibule (area between cheeks and teeth) and oral cavity proper (mostly filled by the tongue).

Tongue

• A large muscle attached to the mouth floor by the frenulum linguae.
• Positions and mixes food.
• Contains taste receptors.
• Important for food intake and initial digestion.
• Crucial for speech formation in humans.

Teeth

• Key structures for tearing and grinding food.
• Two sets:
  • Milk teeth (20): 2 incisors, 1 canine, 2 molars on each side of upper and lower jaws.
  • Permanent teeth (32): 2 incisors, 1 canine, 2 premolars, 3 molars on each side of upper and lower jaws.

Palate

• Separates the mouth from the nasal cavity.
• Allows separate passages for air and food.
• Involved in speech sound formation by modifying air passage.

Salivary Glands

• Three pairs of glands:
  • Parotid gland (1): Below the ear, duct opens into vestibule.
  • Sublingual gland (2): In the mouth.
  • Submandibular gland (3): In the mouth.

Pharynx

• Fibromuscular tube connecting the mouth and the base of the skull.
• Ends below the level of C5.
• Located behind nose and mouth.
• Divided into three parts (nasopharynx, oropharynx, laryngopharynx):
  • Nasopharynx: Located between the base of the skull and soft palate. It is continuous with the nasal cavity and conditions inspired air.
  • Oropharynx: Located between the soft palate and superior border of the epiglottis.
  • Laryngopharynx: The most distal part, found between the superior border of the epiglottis and the inferior border of the cricoid cartilage (C6), continuous with the esophagus.

Esophagus

• Fibromuscular tube (approximately 25cm).
• Transports food from the pharynx to the stomach.
• Originates at the inferior border of the cricoid cartilage (C6).
• Pierces the diaphragm at the level of T10.
• Extends to the cardiac orifice of the stomach (T11).
• Three constrictions:
  • At junction with pharynx (upper esophageal sphincter).
  • Where it crosses the aortic arch and left main bronchus.
  • At its entry into the diaphragm (lower esophageal sphincter).

Stomach

• Most distensible part of the gastrointestinal tract (GIT).
• Intraperitoneal digestive organ between the esophagus and duodenum.
• 'J' shape, with lesser and greater curvatures.
• Anterior and posterior surfaces are smooth and rounded with peritoneal covering.
• Four anatomical divisions: cardia (superior opening), fundus (rounded portion), body (large central portion), and pylorus (area connecting to the duodenum).

Relations of Stomach

• Superior: Esophagus, left dome of diaphragm.
• Anterior: Liver, gall bladder, anterior abdominal wall, diaphragm, greater omentum.
• Posterior: Left kidney, left suprarenal gland, spleen, splenic artery, pancreas.

Small Intestine

• Approximately 6 meters long in the average person.
• Assists in the digestion and absorption of ingested food.
• Extends from the pylorus of the stomach to the ileocecal junction.
• Meant the large intestine at the ileocaecal valve.
• Divided into three anatomical parts: duodenum, jejunum, ileum.

Duodenum

• The most proximal portion of the small intestine.
• Derived from the Latin "duodenum digitorum" (meaning twelve fingers).
• Runs from the pylorus of the stomach to the duodenojejunal junction.
• Divided into four parts (superior, descending, inferior, ascending), forming a C-shape around the head of the pancreas.
• Receives openings from the common bile duct and the pancreatic duct.

Jejunum and Ileum

• The distal two parts of the small intestine (jejunum 2/5, ileum 3/5).
• Intraperitoneal.
• Attached to the posterior abdominal wall by mesentery.
• Jejunum starts at the duodenojejunal flexure; ileum ends at the ileocaecal junction.
• Ileocaecal valve: prevents reflux of material back into the ileum.

Large Intestine

• Divided into different parts including the cecum, vermiform appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anal canal.
• Primarily absorbs water and electrolytes.
• Stores undigested materials until expulsion as feces.
• Approximately 150cm long.

Liver

• Second largest organ (after the skin).
• Largest gland (average weighing 1500g).
• Located under the diaphragm in the right upper abdomen, extending to the midabdomen.
• Wedge-shaped with a soft consistency, pink-brown color.
• High vascularity and easily friable.
• Four lobes: right, left, caudate, and quadrate.
• Separated by a deep transverse fissure (porta hepatis) which transmits vessels, nerves, and ducts.

Liver Surfaces

• Diaphragmatic surface: Smooth, convex, fits beneath the diaphragm
• Visceral surface: Irregular, moulded by surrounding organs and in contact with various abdominal structures (e.g., right kidney, right adrenal gland, right colic flexure, transverse colon, first part of duodenum, gallbladder, esophagus, and stomach).

Liver Ligaments

• Several ligaments attach the liver to surrounding structures formed by a double layer of peritoneum.
• Include: falciform ligament, coronary ligament, triangular ligament, lesser omentum.

Liver Blood Supply

• Hepatic artery proper (25%): Supplies non-parenchymal structures (arterial blood), arising from the coeliac trunk.
• Hepatic portal vein (75%): Supplies the liver with partially deoxygenated blood (carrying nutrients absorbed from small intestine).
• Venous drainage: Through hepatic veins which enter the inferior vena cava.

Biliary System

• Gallbladder: Sac-like organ in the right hypochondrial region, intraperitoneal.
  • Concentrates and stores bile produced by the liver, and releases it in response to cholecystokinin.
  • Parts include fundus, body, and neck.
• Biliary tree: Series of ducts allowing newly synthesized bile from the liver to be concentrated and stored in the gallbladder (prior to release into the duodenum).
  • Key ducts include common hepatic duct, cystic duct, and common bile duct.
  • Common bile duct joins the main pancreatic duct at the hepatopancreatic ampulla (ampulla of Vater) and opens into the duodenum via the major duodenal papilla.
  • The sphincter of Oddi regulates the flow of bile and pancreatic secretions.

Pancreas

• Abdominal glandular organ with both digestive (exocrine) and hormonal (endocrine) functions.
• Located deep within the upper abdomen, in the epigastrium and left hypochondrium, posterior to the stomach and concavity of duodenum.
• Parts include head, neck, body, and tail.

Spleen

• Large lymphoid organ in the upper left abdomen (left hypochondrium).
• Roughly the size of a fist.
• Acts as a blood filter (removing old red blood cells) and plays a role in immune responses by producing lymphocytes.
• Located under the cover of the diaphragm and left 9, 10, 11 ribs.
• Not normally palpable (except when enlarged).
• Two surfaces:
  • Diaphragmatic surface: Faces diaphragm and ribcage.
  • Visceral surface: Faces other abdominal viscera (e.g., stomach, left kidney, and spleen).

Explore the anatomy of the mouth cavity, including the tongue's role in taste and speech, teeth structure, and the palate's separation of the mouth from the nasal cavity. Learn about salivary glands and their function in digestion.