Digestive System (Oral Cavity to Stomach) Flashcards
What is the digestive system comprised of?
Oral cavity and alimentary canal
Alimentary canal
Includes esophagus, stomach, small and large intestines and several glands
Hollow tube with 4 layers
What are the layers of the alimentary canal?
- T. mucosa
- T. submucosa
- T. muscularis
- T. Serosa (CT covered by mesothelium) / T. adventitia
What is included in the oral cavity?
Lips, palate, teeth, tongue and salivary glands
Epithelium of the lip and cheek (oral cavity)
Outer surface: Strat. squamous keratinized with hair
Inner surface: Strat. squamous non-keratinzed (dogs) and keratinized (ruminants and horses)
Hard palate
Strat. squamous keratinized (thick in ruminants and forms the dental pad rostrally)
Blended lamina propria and submucosa covering bony tissue
Soft palate
Strat. squamous on oral side
Pseudostrat. ciliated on nasal side
Blended lamina propria with lymphatic tissue
What are the functions of the tongue?
Mastication, taste, licking and suckling
Mucosa form papillae
Filiform (keratinized in horses, ruminants and cats, most numerous, no TB)
Fungiform (mushroom shape)
Foliate (RABBITS, leaf shape)
Circumvallate
Conical and lenticular (lent. only in ruminants, lentil shape)
Mechanical papillae
Filiform
Conical
Lenticular
Gustatory
Circumvallate (taste buds on lat. side)
Foliate (TB on lat. side)
Fungiform (few TB on dorsal side)
How many planes does the skeletal muscle on the tongue have?
3: longitudinal, vertical and transverse
What glands are present on the tongue?
Serous/ mucous (VonEdner associated with circumvallate papillae)
Lyssa (tongue)
Fatty tissue and muscle in CT capsule
Dog, cat and pig
Horse tongue
Dorsal lingual cartilage (hyaline) with CT
(fibroelastic CT and fat)
Ruminants tongue
Torus linguae (thickened mucosa on caudal dorsal aspect)
Lenticular papillae
Birds tongue
Lingual bone
Taste bud
Bell-shaped
Taste cells, supporting cells, and nerve fibers innervating taste cells
4 taste qualities: sweet, salt, bitter and acid
What are the salivary glands?
Parotid, mandibular, sublingual, zygomatic (canivores) and molar (cats)
Parotid
Serous
Striated ducts
Saliva
Contains amylase which starts the carbohydrate digestion in the oral cavity
What do teeth consist of?
Soft tissues (pulp cavity and periodontal ligament)
Hard tissues (enamel, dentin and cement)
Enamel
Covers the crown
Hardest substance in the body
Acellular and avascular
Have prisms synthesized by ameloblasts (non-regernative)
Dentin
Skeleton of the tooth
Living and regenerable
Have dentinal tubules and inter-tubular tissue
What are the tubules of dentin composed of?
Calcified matrix containing collagen fibers
Synthesized by odontoblasts lining the inner pulp cavity
Cementum
Covers dentin of the root
Consists of calcifed matrix with collagen fibers synthesized by cementocytes
Periodontal ligament
Dense CT with no mineral
Fibers penetrate as Sharpey’s fibers on one side and insert to bony alveolus on the other
Dental pulp
Jelly-like, with fibers
CT cells, BVs, and nerve fibers
Lined by odonoblasts
Brachydont
Simple
Crown covered by enamel and root by cementum
Teeth in man, carnivores and swine (except canine) and incisors in ruminants
Hypsodont
Complex
Cement covers root and crown
All teeth in horse and rodents, molars in ruminants, pig canines
Tunica mucosa in the esophagus
Strat. squamous non-keratinized in man and dog
Strat. squamous keratinized in all other domestic species
Submucosa in esophagus
Mucous glands
Short cranial segment of horse, cat and ruminants
Cranial half only in pig
Throughout the dog
T. Muscularis in esophagus
Skeletal throughout dog and ruminants
Skeletal in first two-third, mix of smooth and skeletal in middle , then smooth distally in other species
Serosa/adventitia in esophagus
Serosal covering in the thoracic and abdominal part
Adventitial in the cervical part
How is the stomach classified?
Simple, compound monogastric and compound polygastric
Simple stomach
Rugae (mucosa and submucosa), gastric pits, simple columnar with mucus cells (secrete alkaline)
Glands in lamina propria
TJs
Simple stomach in the dog and cat
Cardiac (small), fundic and pyloric parts
No cutaneous
Simple stomach in the pig
Largest cardiac
Small cutaneous part (strat. squamous keratinized)
Simple Stomach in the horse
Very large cutaneous part
Demarcation with the glandular part (margoplicatus)
Compound stomach
Rumen, reticulum, omasum: cutaneous part modified to form papillae, fermentation of cellulose to form volatile fatty acids
Abomasum: structurally similar to simple stomach
What are the functions of the simple stomach?
Continue the digestion of carbohydrate
Add acidic fluid to the food
Transform the food into a chyme
Promote the initial digestion of proteins with enzymes pepsin and secrete hormones
What are the 3 regions of the simple stomach?
Cardia, fundus, pylorus
How long does it take mucous cells to be replaced?
every 3-4 days
What cell types are present in the simple stomach?
Mucous cells
Chief cell (zygomatic)- pepsinogen
Parietal cell
Argentaffin cell (gastrin and secretin)
Parietal cell
Secretes HCl
Intrinsic factor in human (deficiency–> anemia)
Supports B12 absorption
What are the protective mechanisms for the stomach?
- Alkaline mucous surface coat
- Alkaline intestinal fluid
- Fully developed junctional complexes
- Regeneration of epith.
- Vomiting reflex
- Immunological defense
Fundic glands
Predominant gastric glands
Has a isthmus, neck and base
Has all cells
Stem cells of the fundic gland
Found in isthmus and neck regions
Continuously divide
Replace aging cells of the gastric epith.
Parietal cells of the fundic gland
Large, eosinophilic, triangular, upper half of fundic gland
Many mitochondria and intracellular canaliculi
Secrete HCL
What stimulates HCL production
Gastrin and parasympathetic stimulation
Chief cells
Lower half of fundic gland
Basophilic cytoplasm and zymogen granules
Secretes pepsinogen
Argentaffin (enteroendocrine) cells
Diffuse endocrine cells (APUD)
Bases of gastric glands
Secretes gastrin, secretin, cholecystokinin
Cardiac glands
Localized in a narrow zone around and near the esophageal opening into the stomach
Mostly mucous cell types, some parietal
Occupy half in pig
What is the function of cardiac glands?
Mucus production that protects the esophageal lining from gastric HCL
Pyloric glands
Almost half of the stomach in dog and cat
Only mucus cells
Deeper gastric pits
Branched and coiled glands
What is the function of the pyloric glands?
Produce mucus
Rumen
Cutaneous mucosa forming finger-like conical papillae
Function is to ferment food by microorgs
Reticulum
Cutaneous mucosa, honeycomb structure
Function is to break down food
Omasum
Cutaneous mucosa and submucosa form primary and secondary folds
Function is to breakdown food
