Digestive System - Animal Anatomy II

Triadan System quadrant numbering convention

Quadrant 100s = Upper Right; Quadrant 200s = Upper Left; Quadrant 300s = Lower Left; Quadrant 400s = Lower Right.

Adult equine dental count and formula

$36 - 42$ teeth total; represented by formula $2 \times (I\,3/3 \quad C\,1(0)/1(0) \quad P\,3(4)/3 \quad M\,3/3)$

Wolf tooth

The upper first premolar in horses, present in some individuals.

Adult ruminant dental count and formula

$32$ teeth total; represented by formula $2 \times (I\,0/4 \quad C\,0/0 \quad P\,3/3 \quad M\,3/3)$, lacking upper incisors, upper canines, and first premolars.

Equine dental points wear locations

Sharp points formed on the lateral side of the upper cheek teeth and the medial side of the lower cheek teeth.

Floating the teeth

The equine procedure of periodically filing down sharp enamel points formed on cheek teeth.

Peg teeth

Two small auxiliary incisors located directly behind the upper primary incisors in rabbits.

Rabbit cheek teeth count

$6$ upper premolars, $4$ lower premolars, $6$ upper molars, and $6$ lower molars.

Malocclusion in rodents

The overgrowth of continuously growing, open-rooted incisors caused by jaw misalignment and improper occlusion.

Rabbit molar malocclusion effects on the tongue

Abnormal wear forms sharp spikes or spurs that angle toward, penetrate, or entrap the tongue, hindering swallowing.

Brachodont teeth key characteristics and occurrence

Low-crowned or simple teeth found in humans, carnivores, pigs, and ruminant incisors that stop growing after eruption.

Three anatomical components of a brachodont tooth

Crown (above the gums), neck (level with the gums), and root(s) (below the gums).

Characteristics of Hypsodont teeth

Ever-growing teeth that have no distinct neck. They continue to grow.

What animals have hypsodont teeth?

Ruminant cheek teeth, pigs canines or tusks, teeth of horses and teeth of rodents and rabbits.

Canine Teeth Dental Formula and Characteristics

12 incisors, 4 canines, 16 premolars, and 10 molars. 2(I 3/3, C 1/1, P 4/4, M 2/3)

What are the Carnassial Teeth?

Upper 4th premolar and the lower 1st molar teeth are the largest teeth, known as the Carnassial Teeth. These teeth slide past each other cutting up ingested food.

What happens when there’s an abscesion of the Carnassial Teeth?

It produces a fistula which erupts below the animal’s eye. It had 3 roots so it must be separated before being extracted.

Feline Teeth and Dental Formula

Adult teeth - 30. 12 incisors, 4 canines, 10 premolars and 4 molars.

2 ( I 3/3, C 1/1, P 3/2, M 1/1) = 30

Feline Carnassial Teeth

Upper 4th premolar and 1st lower molar.

Nerves of the mandible and maxilla

Trigeminal nerve supplies motor stimulation to the muscles of mastication

Extrinsic tongue muscles

anchor tongue in place

Buccal cavity

The opening to the oral cavity containing the teeth and tongue.

Vestibule

Space between the outer surface of teeth and surrounding lips and cheeks.

Oral cavity boundaries

Space bordered by teeth laterally and rostrally, and hard/soft palate dorsally.

Oral fissure

The opening into the oral cavity, with boundaries marked by the lips.

Prehension

The process of bringing food into the oral cavity.

Cheeks

Form the lateral walls of the vestibule.

Layers of lips and cheeks

Outer haired skin, middle muscle and fibroelastic tissue, and inner mucosa.

Middle muscular layer of lips and cheeks

Consists of muscles of mastication that contribute to biting strength.

Philtrum

The cleft that divides the two halves of the upper lip.

Philtrum depth variations

Shallow in equines and deeper, more prominent in carnivores.

Hard palate

Rostral roof of the mouth made of palatine, maxillary, and incisive bones.

Soft palate

Caudal roof of the mouth made of muscle and connective tissue.

Pharynx division

Divided by the soft palate into the oropharynx and nasopharynx.

Soft palate function during swallowing

Raised to close off the nasal passage and prevent food from entering.

Buccal tooth surface

Surface facing the cheek.

Labial tooth surface

Surface facing the lips.

Lingual tooth surface

Surface facing the tongue.

Palatal tooth surface

Surface facing the hard palate.

Mesial tooth surface

Surface facing the midline or center of the dental arch.

Distal tooth surface

Edge facing away from the center of the dental arch.

Occlusal or masticatory surface

Surfaces on upper and lower teeth that come together when closed.

Body of the tongue

Long and slender part that links the apex with the root.

Mandibular salivary gland

Located under the tongue and caudal to the angle of the jaw, secreting mixed fluid.

Sublingual salivary gland

Located under the tongue with the mandibular gland, secreting mixed fluid.

Functions of saliva

Lubrication, antibacterial action, pH regulation, thermoregulation, and enzymatic digestion.

Where are teeth found?

Found in sockets or cavities called alveoli.

How are teeth held in place?

The periodontal ligament

What is the crown?

It projects above the gums (gingiva)

Whats the apex?

Tip of the roots, where blood vessels and nerves enter the tooth.

Intrinsic muscles of tongue

TMJ movements

Extension, flexion, and translation (lateral and rostral movement of the mandible).

Pharynx tracts

Serves as a part of both the gastrointestinal tract and the respiratory tract.

Esophagus pathway

Travels dorsal to the trachea, moves to the left, and passes through the thoracic cavity and diaphragm to enter the stomach.

Esophagus muscle composition by species

Skeletal throughout in dogs, horses, and ruminants, but the distal esophagus changes to smooth muscle in cats and primates.

Parotid gland secretion

Serous in most species, accounting for about half of the total volume of saliva produced.

Tonsils location and function

Located in the pharynx to protect the animal against some diseases.

Lysozyme function

enzyme found in saliva, controls bacterial population in oral cavity

Amylase function

found in mainly omnivores & some avian species. Assists in breakdown of starchy carbohydrates

What is translation?

Movement of mandible to the side (laterally) & forward (rostrally)

Whats the epiglottis?

part of laryngeal cartilage that covers the glottis during act of swallowing

Where is the opening of the eustachian tube located?

Pharynx

What does the opening of the eustachian tube do?

Equalizes atmospheric pressure with the pressure of the middle ear

The inside of the esophagus is what?

Is lined by mucosa that is formed into folds, allowing for
expansion or dilation necessary when food passes through it

What is the cardiac sphincter?

Thickening at gastric end of esophagus prevents the highly acidic
contents of stomach from backflowing or refluxing into esophagus & damaging mucosa

Where is the medulla oblongata located?

In the brainstem

What does the brainstem have to do with the salivary glands?

Brainstem regulates parasympathetic & sympathetic activity of the salivary glands

Swallowing/Deglutition definition

The process by which food from the oral cavity is transported to the stomach or reticulorumen.

2nd phase: the pharyngeal stage: involuntary reflex controlled by the swallowing center in brainstem

Once the swallowing reflex begins, it cannot be stopped.

A wave of muscle contractions moves across pharynx, pushing food bolus into esophagus

Breathing stops momentarily & epiglottis covers glottis, preventing food from entering trachea

3rd phase: esophageal state: involuntary reflex

The presence of food in the esophagus stimulates the swallowing center to initiate peristalsis.

What is peristalsis?

pattern of muscle contraction, involving the circular muscle layer in esophagus that propels food through GI tract

The abdominal cavity consists of what 3 peritoneum’s?

Visceral, parietal and connecting peritoneum.

What is the Visceral Peritoneum?

surfaces of organs are covered by this serous membrane

What does the Parietal Peritoneum do?

Covers abdominal body wall

What does the connecting peritoneum do?

connect organs to parietal peritoneum and to one another.

Mesentery

suspends the intestines from the abdominal wall

Omentum

double-layered connecting peritoneum that links the stomach to the abdominal wall or other organs.

Purpose - store fat and assist with insulating the abdomen.

Production of intrinsic factor

Required for Vitamin B12 absorption in small intestine

Chyme

Food in a semi-liquid state

Monogastric Stomach characteristics

Simple stomach with one chamber, c shaped organ

Main blood supply in monogastric stomach

Celiac artery, first branch off the of the abdominal aorta

Stomach drainage

The veins leaving the stomach travel thru the portal vein to the liver

Rugae

Transient folds of gastric mucosa

What does the rugae allow the stomach to do

Allow the stomach to expand when it is filled with food, increasing surface area for absorption

What is the gastric mucosa made of, and what does it contain?

Simple columnar epithelium. Contain surface mucous cells: produce a layer of mucus to help protect the stomach from acid produced

Where does the esophagus enter?

The cardia, which has closer proximity to the heart.

Glandular portion of the stomach can be divided into 3 parts:

Cardia, Fundus and Pylora

What is the fundus?

dome-shaped, blind-ended sac; adjacent to cardia. Fundus can expand to store food after its been consumed. Leads into body of stomach, contains different glandular cells.

What is the pylorus?

Distal part of stomach

Gastric emptying rate

Controlled by strength of pyloric antral muscle contractions.

Ruminant Stomach

Consists of 4 chambers, first three chambers: forestomach

Rumen, Reticulum and Omasum, nonglandular

True stomach of ruminants:

Abomasum, glandular

Where is cellulose degraded?

Rumen and reticulum

What is the rumen and reticulum responsible for?

Fermentation

Rumen characteristics

Contains many microorganisms, assist with breaking down carbohydrate substances that make up structural part of plants.

Extends from diaphragm to pelvis when full

Referred to as “paunch” - large volume

Reticulum characteristics

Lies against diaphragm

Resembles honeycomb

Esophageal Groove

Links esophagus with the omasum, important in young ruminants.

When young nurses, the groove folds in and turns into a tube, going straight to omasum and abomasum

Omasum

Absorption of water & salts takes place here.

Has many leaves

Folds of mucosa that have many papillae on their surfaces

Located on right side of abdominal cavity

Abomasum

true stomach, located on right side of abdomen.

Contains various glands - Secrete substances such as pepsinogen, & hydrogen & chloride ions

Motility of Ruminant Stomach

Begins with mastication

saliva contains bicarbonate & phosphate and is alkaline
Bicarbonate helps neutralize acids produced by fermentation