Digestion and Absorption

Teeth

hard, mineralized structures located in the mouth that are used for chewing and tearing food; plays a crucial role in the mechanical breakdown of food

Incisors

Front teeth, for cutting food; commonly found in herbivores, omnivores.

Canines

Also known as fangs or tusks, sharp teeth for piercing, tearing, and holding food; they are most prominent in carnivores, such as dogs and cats

Premolars

Located behind the canines; for shearing or grinding, depending on the diet of the animal; carnivores have sharp-edged ones for slicing meat, while herbivores have flat ones for breaking down plant material

Molars

These are the largest and strongest teeth, designed mainly for grinding; herbivores, like cows and horses, rely heavily on molars to process fibrous plant material

Tongue

a muscular organ with fibers in three directions, allowing extreme mobility to move food for chewing, swallowing, and, in some animals, grasping food and grooming

Epiglottis

A flap-like structure made of cartilage located at the base of the tongue; 
prevents food and liquid from entering the trachea (windpipe) during swallowing

Vallate Papillae

Large, round papillae located at the back of the tongue, containing taste buds that detect bitter flavors

Torus of the Tongue

A raised area, more prominent in some animals, that aids in moving food within the mouth for chewing and swallowing

Filiform and Conical Papillae

Tiny, hair-like structures that help with gripping and moving food; they do not contain taste buds

Fungiform Papillae

Mushroom-shaped papillae that contain taste buds, mainly detecting sweet and salty flavors

Tip of Dorsum

The front part of the tongue, which plays a key role in taste, food manipulation, and initial digestion

Pharynx

the shared passage for food and air, and it is located behind the mouth and nose

Normal Respiration (Breathing)

Air passes through the nasal cavity and pharynx into the trachea (windpipe) to reach the lungs; The epiglottis stays open, allowing air to flow freely into the trachea

Deglutition

When swallowing, food moves from the oral cavity into the pharynx and then into the esophagus (food pipe); the soft palate moves up to block the nasal cavity so food doesn’t go up the nose; the epiglottis closes over the trachea, preventing food from entering the airway and ensuring it goes into the esophagus

Esophagus

a muscular tube that connects the pharynx (throat) to the stomach; doesn’t have true sphincters (valves), but muscles that control flow at the top (near the throat) and bottom (near the stomach) to prevent food from moving in the wrong direction

Peristalsis

muscle contractions that allow food to move down the esophagus

Esophagus smooth muscle

Found in the lower part of the esophagus in some animals; works automatically without conscious control; helps move food toward the stomach through slow, rhythmic contractions (peristalsis)

Esophagus striated muscle

Found in the upper part of the esophagus in most animals; allows some control over swallowing, especially in species like cattle and dogs

Carnivore stomach type

fully glandular

Fundic (gastric) glands

Secrete hydrochloric acid (HCl) and pepsinogen to aid digestion; glandular stomach region

Pyloric glands

Produce mucus and gastrin (a hormone that stimulates digestion); glandular stomach region

Ruminant stomach regions

Rumen, reticulum, omasum, and abomasum ("true stomach“)

Abomasum ("true stomach“)

functions like a glandular stomach, secreting digestive enzymes; stomach region of ruminants

Small intestine

functions in digestion and nutrient absorption; long, narrow tube that connects the stomach to the large intestine

Duodenum

receives digestive fluids from the pancreas (enzymes) and liver (bile) to help break down food

Jejunum and ileum

the two lower segments of the small intestine, located after the duodenum that mainly absorb nutrients

Villi

Tiny finger-like projections on the inner walls of the small intestine that increase surface area; covered with intestinal cells; maximize absorption

Mucosal Fold

The innermost layer of the small intestine; intestinal cells form the brush border, which contains enzymes that help with the final breakdown of nutrients before absorption

Serosa

The outer protective layer of the small intestine that reduces friction between organs

Longitudinal Smooth Muscle

Shorten the intestine to move food forward

Circular Smooth Muscle

Contracts to mix food and push it along the intestine

Submucosa

A small intestine layer that contains blood vessels, lymph vessels, and nerves that support digestion and absorption

Muscularis Mucosa

A thin muscle layer that moves the mucosa and helps villi move to improve absorption

Large intestine

responsible for fermentation, water absorption, and feces formation; consists of the cecum, colon, rectum, and anus; varies between species based on their diet and digestive needs

Cecum

Ferments food (especially in herbivores); section of the large intestine

Colon

Absorbs water and nutrients, with different shapes depending on the species; section of the large intestine

Rectum

Stores feces before elimination; section of the large intestine

Anus

Controls waste expulsion through a muscular sphincter; section of the large intestine

Large intestine of cattle (Ruminants)

Fermentation mainly occurs in the rumen; the cecum is present, but digestion happens mostly in the spiral colon (ansa spiralis); the spiral colon helps absorb remaining nutrients from fermentation

Large intestine of horses (Non-Ruminant Herbivores)

Fermentation happens mainly in the large cecum and colon; the cecum is very large and comma-shaped; the small colon (descending colon) absorbs water and forms feces

Large intestine of pigs (Omnivores)

Have a moderately developed cecum and colon for fiber digestion; the spiral colon (ansa spiralis) allows for extra fermentation time

Pancreas

a glandular organ located in the abdomen behind the stomach that releases proteases into the small intestine; lipase breaks down triglycerides into free fatty acids, monoglycerides, and glycerol