Anatomy of the Digestive System

Digestive System

• The digestive system consists of the alimentary canal, which is a tube that extends from the mouth to the anus.
• The alimentary canal includes several organs such as the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.
• Tonsils are masses of lymphoid tissue located on both sides of the back of the throat.
• The stomach is a sac-like organ that secretes digestive enzymes to break down food.
• The stomach has four distinct parts: rumen, reticulum, omasum, and abomasum.
• The rumen is the first compartment of the stomach and is responsible for breaking down cellulose in plant cell walls.
• The small intestine is a long, thin tube where most of the nutrient absorption takes place.
• The large intestine is also known as the colon and is responsible for water absorption and electrolyte absorption.

Urogenital System

• The urogenital system consists of the kidneys, ureters, urinary bladder, and urethra.
• The kidneys are bean-shaped organs that filter waste and excess fluids from the blood.
• The ureters are narrow tubes that connect the kidneys to the urinary bladder.
• The urinary bladder, also known as the vesica urinaria, is a muscular sac that stores urine.
• The structure of the bladder includes a lining of epithelial cells, a layer of connective tissue, and a layer of smooth muscle.
• The urethra is a tube that connects the urinary bladder to the outside of the body, allowing urine to be excreted.

Teeth

• Types of teeth: Incisor, Canine, Premolar, Molar
• Wolf tooth: Upper first premolar tooth in horses
• Carnassial teeth: Sectorial teeth in carnivores, located at the 4th upper premolar tooth and 1st lower molar tooth
• Tooth structure: Enamel, Dentin, Cement
• Parts of a tooth: Corona dentis (Crown), Collum dentis (Neck), Radix dentis (Root)
• Brachyodont type: Short crowned, found in humans, carnivores, pigs, ruminants, and equine (canine)
• Hypselodont type: Long crowned, found in equine and ruminants (cheek)

Mouth

• Labia oris: Upper lip (Labium superius), lower lip (Labium inferius)
• Modifications of upper lip: Planum nasolabiale in ox, Rostral disc in pig
• Bucca: Lateral, with buccal glands
• Lingual frenulum: Thin band of tissue connecting tongue to floor of mouth
• Gums: Gingiva, dental pad in ruminants
• Palatum durum: Hard palate with raphe palati and rugae palatinae
• Papilla incisiva: Small median swelling on upper incisor
• Vomeronasal organ: Blind-ending canal lined by olfactory mucosa, influences mating and social behavior

Tongue

• Structure: Radix linguae (Root), Corpus linguae (Body), Apex linguae (Apex)
• Frenulum linguae: Mucosal fold connecting tongue to oral floor
• Sulcus medianus: Median groove on dorsal aspect of canine tongue
• Foliate papillae: Small, vertical folds on the tongue's posterolateral sides, found in horse and pig
• Other papillae: Vallate, lenticular, conical, fungiform, and filiform

Salivary Glands

• Function: Produce saliva, aid digestion, keep mouth moist, and support healthy teeth
• Minor salivary glands: Labial, buccal, and zygomatic glands
• Major salivary glands: Parotid, Mandibular, and Sublingual glands
• Location and duct openings of major salivary glands vary by species