Veterinary structure and function

• The heart is divided into four chambers, two atria (right and left) and two ventricles (right and left).
• Terms to know


  • lips
  • cheek
  • hard palate
  • tounge
  • oropharynx
  • vestibule
  • diastema
  • labial
  • buccal
  • linguae
  • papillae
  • parotid
  • mandibular
  • sublingual
• Digestive System


  Includes the mouth, pharynx, alimentary canal and accessory glands
• Alimentary canal


  • Muscular tube consisting of esophagus, stomach, small intestine, large intestine, and anal canal
• Accessory glands


  • Large salivary glands (located in the head), and two large glands (liver & pancreas)
• Function of Digestive System


  To digest and absorb food, to excrete the waste products
• Oral cavity


  Prehension, selection, mastication, and insalivation of food. Extends from the lips to the entrance into pharynx
• Oral cavity


  • Supported by incisive bone, palatine and alveolar processes of maxilla and mandible. Bounded rostrally by the lips, and laterally by cheeks. Its roof is hard palate; ventrally is tongue and under its apex is the floor of oral cavity. Caudally it communicates with oropharynx
• Vestibule


  Space between the lips/cheeks and the teeth/gums
• Diastema


  Interdental space between the incisors and the cheek teeth
• Rostrally, two narrow incisive ducts connect the oral cavity (incisive papillae) with nasal cavity
• Mucous membrane of oral cavity

  • Usually pink, well supplied with blood vessels and in its submucosa contains serous or mucous glands known as labial, buccal, and lingual glands, depending on location
• Lips


  Assist in sucking and prehension of food. Differ in shape and mobility. Attach to the incisive bone and incisive part of mandible, and consist of three layers: external layer (skin), middle layer (muscle, tendons, conn. and adipose tissue), and internal layer (labial mucosa)
• Upper lip of carnivores and small ruminants


  • Divided by distinct median cleft, philtrum
• Cheeks


  • Form lateral wall of buccal vestibules. Caudal portion contain powerful masseter muscle. Consist of three layers: skin, intermediate layer of glands and muscles, and buccal mucosa. In ruminants, it forms cone-shaped cornified papillae, which are also present on lips and directed caudally
• Gums


  Encircle the neck of teeth. In ruminant, the gums are modified to form dental pad (replace upper incisors)
• Hard palate


  • Tough mucosa (in horse contains rich venous plexus). Divided into two halves by a median palatine raphe and transversely directed palatine ridges. Mucosa has no gland
• Tongue


  Supported caudally by hyoid bone. Consists of striated muscle, connective and adipose tissue, some glands, and externally a thick mucous membrane. Shape differs between species. Very mobile and versatile organs. Essential for prehension, sorting of solid food in some animals, intake of liquids, and for sucking. An important tactile organ either by mechanical or by taste buds (chemical selection of food). Necessary to both mastication and deglutition, and it delivers the insalivated bolus into pharynx
• Nerves innervating the tongue

  • Mandibular branch of trigeminal nerve (V)
  • Facial nerve (VII)
  • Glossopharyngeal nerve (IX)
  • Vagus nerve (X)
  • Hypoglossal nerve (XII) - motor
• Forms and Structure of tongue

  • Dorsum linguae - surface, Apex - free rostral portion, Frenulum linguae - median fold, Corpus linguae - body, Radix linguae - root. The tongue lie in intermandibular space (narrow in herbivores). The tongue is anchored to the mandible and hyoid apparatus by the extrinsic lingual muscle. Herbivores and pig - body of tongue has extensive lateral surfaces. Ruminants - torus linguae and fossa linguae. Horse - cartilage bar in the median plane. Dog -median groove (dorsum). Ventral and lateral surfaces -mucous membrane is thin and delicate. On dorsum, mucosa is thick and tough (esp. ruminants & cat)
• Tongue papillae


  • Filiform papillae
  • Conical and lenticular papillae
  • Fungiform papillae
  • Vallate papillae
  • Foliate papillae
• Filiform papillae


  • Soft & horny shape. Ox, sheep, cat –small & directed caudally. Ox & cat –heavily cornified. Carnivores & pig –soft and long at radix. Radix free of papillae in other species
• Conical & lenticular papillae

  • Scattered among filiform (esp. on torus linguae)
• Fungiform papillae


  Contain taste buds. On dorsum (and borders)
• Vallate papillae


  • On dorsum, rostral to root of tongue. Larger than fungiform. Pig & horse -1 pair (large). Carnivores -2-3 pairs. Ox -8-17 pairs. Sheep -18-24 pairs. Goat -12-18 pairs
• Foliate papillae


  On border of tongue. Parallel leaves of conn. tissue
• Lingual muscles


  • Intrinsic lingual muscle (proper) - bulk of tongue, consist of deep and superficial fibres bundles, not attach to the skeleton, run in longitudinal, perpendicular, and transverse directions, can alter the shape of tongue. Extrinsic muscle - originate from skeleton and enter the tongue from behind and below (Genioglossus, Hyoglossus, and Styloglossus)
• Masticatory apparatus


  • Teeth & gums
  • Temporomandibular & symphysial joint of jaw
  • Masticatory muscles (temporalis, masseter, pterygoid)
• Salivary glands


  Parotid, mandibular & sublingual glands. Saliva - serous or mucous. Aids in formation of bolus. Act as lubricant during swallowing. Contain enzyme amylase (ptyalin) – hydrolysis/digest of starch in mouth. Amylase- present in the saliva of pig, and absent in ruminant and dog/cat
• Parotid gland


  • Lighter red. Fills the retromandibular fossa. Dorsally -base of ear, Ventrally -extend into neck & intermandibular space, Medially - common carotid artery, external jugular vein, hyoid bones & its muscles, branches of facial & trigeminal nerves, lymph nodes. In horse it make contact with guttural pouch. In carnivores -small and triangular. In pig -large and triangular. In ruminant -club-shaped. In horse -large and fills retromandibular fossa completely. Duct open on buccal vestibule
• Mandibular gland


  • Between basihyoid and wing of atlas. Partly covered by parotid gland. Dog -oval & >parotid. Pig -oval & <parotid. Ruminants -larger & extend from wing of atlas into intermandibular space. Horse -<parotid, long & narrow. Mandibular duct opens on floor of oral cavity
• Sublingual glands


  Two in number. Lie under mucosa of lateral sublingual recess and lateral surface of tongue
• Zygomatic gland


  In dog = dorsal buccal gland. Medial to zygomatic arch. Duct open into buccal vestibule
• Hard palate


  The roof of the mouth, which separates the oral and nasal cavities.
• Tough mucosa


  A type of mucous membrane that is thick and resistant to wear and tear.
• Horse hard palate


  Contains a rich venous plexus, divided into two halves by a median palatine raphe, and transversely directed palatine ridges.
• Rich venous plexus


  A network of veins that receive blood from the mucous membrane.
• Median palatine raphe


  A narrow band of tissue that runs along the midline of the hard palate.
• Transversely directed palatine ridges


  Ridges of tissue that run horizontally along the hard palate.
• Mucosa of the hard palate


  Does not contain any glands.