Digestive System

Peritoneum

Lining of the abdomen

Parietal peritoneum

Lines abdominal walls

Visceral peritoneum

Covers organs

Intraperitoneal space

Only small amount of fluid; no organs in this space

Connecting peritoneum

Mesentery and omentum are examples of…

Mesentery

Peritoneum (sheets of connective tissue) that suspends the digestive tube in the abdomen from the dorsal body wall; contains blood, lymph, and nerves; delivers nutrients to intestines

Omentum

Peritoneum that attaches stomach to adjacent organs

Greater omentum

Peritoneum from greater curvature of the stomach to the dorsal body wall

Lesser omentum

Peritoneum from lesser curvature of stomach to liver and duodenum

Digestive system

Takes complex foods and breaks them down into simple nutrient molecules through the digestion process; absorbed into bloodstream; tube that runs from mouth to anus (with accessory organs for digestion and absorption)

Hindgut fermenters

Monogastric herbivores. Simple stomach with the ability to undergo microbial fermentation within the cecum.

Ruminants

Have mixing and fermentation compartments in addition to the stomach; have 3 forestomachs and one true stomach (abomasum)

Mouth, esophagus, stomach, small intestine, large intestine, anus

Digestive tract basic flow in order

Skeletal

Mouth, prehension, pharynx, cranial portion of the esophagus, external anal sphincter are examples of this muscle in the digestive system

Smooth

The wall of the digestive tube is an example of this muscle in the digestive system

Peristatic contractions

Smooth muscle contraction type that moves contents along the digestive tract

Segmental contractions

Smooth muscle contraction type that causes back-and-forth mixing movement; aids in digestion and absorption by mixing the digestive tract contents and slowing their movement through the tract

Oral (buccal) cavity

Bodily cavity where digestion starts; includes lips, tongue, teeth, salivary glands, hard palate, soft palate, and oropharynx

Lips (labia)

Highly sensitive organ; significant sense organ in horses, cattle, and other species; prehension

Parotid

Pair of salivary glands that is located ventral to the ear canals

Mandibular

Pair of salivary glands that is located central to the parotid

Sublingual

Pair of salivary glands that is located medial to the shafts of the mandible just under the base of the tongue

Salivary glands

Glands in animals that have ducts that carry saliva to the oral cavity

Teeth

Physically break down food into smaller pieces (mastication)

Maxilla and incisive bones

The upper arcade of the teeth contains the…

Mandible

The lower arcade of the teeth contains the…

Pointed, blunted

Carnivores have ______ teeth, while herbivores have _____ teeth

Occlusal surface

Surface where teeth come together

Incisors

Most rostal type of teeth; grasping teeth (4)

Canines

Type of teeth located in the corners of incisors; tearing teeth; tusks (3)

Premolars

Cheek teeth or cutting teeth (2)

Molars

Grinding teeth (1)

100

How are the teeth numbered in the right upper arcade?

200

How are teeth numbered in the left upper arcade?

400

How are teeth numbered in the right lower arcade?

300

How are teeth numbered in the left lower arcade?

Dental pad

Strengthened gum covering the incisive bone replacing the upper incisors in ruminants

Lingual Surface

“Inner surface” of the lower arcade that faces the tongue (3)

Palatal surface

“Inner surface” of the upper arcade that faces the hard palate (1)

Labial surface

“Outer surface” that faces the front of the mouth (4)

Buccal surface

“Outer surface” of both arcades that face the cheek (4)

R 3/3, L 3/3

Cat and dog incisor (upper/lower) dental formula

R 3/3, L 3/3

Horse incisor (upper/lower) dental formula

R 0/3, L 0/3

Cow incisor (upper/lower) dental formula

R 1/1, L 1/1

Cat and dog canine (upper/lower) dental formula

R 1/1, L 1/1

Horse canine (upper/lower) dental formula

R 0/1, L 0/1

Cow canine (upper/lower) dental formula

R 4/4, L 4/4

Dog premolar (upper/lower) dental formula

R 3/2, L 3/2

Cat premolar (upper/lower) dental formula

R 3/3, L 3/3

Cow premolar (upper/lower) dental formula

R 3-4/3, L 3-4/3

Horse premolar (upper/lower) dental formula

R 2/3, L 2/3

Dog molar (upper/lower) dental formula

R 1/1, L 1/1

Cat molar (upper/lower) dental formula

R 3/3, L 3/3

Cow and horse molar (upper/lower) dental formula

42

Dogs number of total teeth

30

Cats number of total teeth

32

Cow number of total teeth

40-42

Horses number of total teeth

Living

Teeth are (living/nonliving) structures

Crown

Portion of the tooth that projects above the gingiva (gums)

Root

Portion of the tooth embedded in the bone

Apex

Tip of the tooth root where blood vessels and nerves enter the tooth

Enamel

A thin layer of a white hard material that covers the crown of the tooth; hardest substance in the body

Dentin

Substance that makes majority of the tooth; surrounds the pulp cavity containing nerve and blood supply

Hypsodont

Pattern of dentition characterized by the continual growth of teeth; large amounts of crown under the gum line; examples of animals with this are horses, rabbits, and rats

Brachydont

Pattern of dentition characterized by the lack of continual growth of teeth; occludes animals with tusks; examples of organisms with this are humans, dogs, and cats

Esophagus

Muscular tube that extends from the pharynx to the stomach; enters the stomach at the cardia

Cardiac sphincter

Weak circle of smooth muscle that closes off an opening; stomach expands; fold of stomach against the esophagus acts as a natural valve

Cardia, fundus, body, pylorus

Portions of the stomach in order

Cardia (cardiac)

Portion of the monogastric stomach that blends with the esophagus, small in size; contains a sphincter (2)

Fundus

Portion of the monogastric stomach that is located to the left and dorsal to the cardiac part (3)

Body

Portion of the monogastric stomach that is the large, central area between fundus and pyloric regions (4)

Pylorus

Portion of the monogastric stomach that joins body to the descending duodenum (5)

Pyloric sphincter

6

Ruggae

Multiple, long folds, curvatures in the stomach

Gastric Dilation and Volvulus (GDV)

Condition commonly associated with large meals and causes the stomach to dilate, due to food and gas; stomach can become dilated enough to rotate

Gastropexy

Treatment of GDV; surgical procedure that tacks a stomach to the right side of the inner abdominal wall

Forestomachs

Compartments that food pass through in rumanants before reaching the abomasum

Swallow, regurgitation, swallow, digest

Rumination in order simplified

Rumen

Large fermentative vat; processes plant material into useable energy; series of muscular sacs separated by pillars

Pilars

Long muscular folds or ruminal wall

Reticulum

Small and most cranial compartment; seperated from the rumen by the rumenoreticular fold; honeycomb appearance; surface area increases absorptive surface; portion of rumen

Omasum

When rumenoreticular contractions occur, they move ingesta here; muscular organ; breakdown food particles further; portion of rumen

Hindgut Fermenters

Stomach type of monogastric herbivores; have very large cecum

Small intestine

Site of majority of nutrient absorption into the bloodstream; divided cranial to caudal into duodenum, jejunum, ileum; boundaries cannot be seen grossly; always functioning

Cranial duodenal flexure, descending duodenum, caudal duodenal flexure, ascending duodenum

Portions of the duodenum (cranial to caudal)

Large intestine

Portion of the intestine containing the cecum, colon, and rectum; varies depending on species and diet  Involved in water and electrolyte absorption  Hind gut fermentation : rats, guinea pigs, horses  Stores feces until defecation

Ileocecocolic junction, ascending colon, transverse colon, descending colon

Portions of the colon in order

Mouth, esophagus, stomach, duodenum, jejunum, ileum, ileocecocolic junction, cecum, colon, rectum, anus

Flow of ingesta in order

Mouth, esophagus, stomach, small intestine, cecum, large colon, small colon, rectum

Flow of equine ingesta

Rectum and anus

Portion of the digestive system that marks the end of ingesta; site of feces elimination

Rectum

Terminal end of the large intestine; has mucus secreting glands to lubricate and ease passage; can dilate (and store); contains sensory receptors that respond to expansion

Anus

Composed of internal and external muscular sphincters

Internal anal sphincter

Portion of the anus that is involuntary; responds to stretch receptors; opens to allow passage of feces into the anal canal to stimulate defecation

External anal sphincter

Portion of the anus that is voluntary; opens to complete the elimination process

Anal glands

Musk gland (powerful, foul smelling secretion); located at 5’ and 7’ o’clock positions; connected to the lateral margin of the anus by a small, single duct; expressed when animal defecates or becomes frightened; functions to mark territory and attract mates; can become blocked

Liver

Organ that produces bile acids which aid in fat digestion; filters materials absorbed from GI tract before systematic circulation); largest gland in the body; divided into several hepative lobes (species dependant); hepatic lobes divided into microscopic hepatic lobules

Right lateral, right medial, caudate (next to right lateral lobe), left lateral, left medial, quadrate (between gallbladder and left medial)

Hepatic lobes

Monitors blood content

In the hepatic portal system, the liver…

Small intestine, hepatic portal vein, liver, hepatic vein

Hepatic portal system in order once products of digestion (nutrients) are absorbed