Four main layers of the GI tract
- tunica mucosa
- tunica submucosa
- tunica muscularis
- tunica serosa
Tunica Muscosa
-intermost layer of GI tract
-Has three sublayers
epithelial lining = stratified, +/- keratin
lamina propria = loose CT
muscularis mucosae = smooth muscle
Tunica submucosa
- consists of dense irregular CT with blood vessels, lymph vessels, and nerve plexus
- may contain glands and lymphatic tissue
Tunica muscularis
- AKA muscularis externa
- two or more layers of smooth m.
- inner circular and outer longitudinal layer
- CT between the two muscle layers contain blood vessels, lymph vessels, and nerve plexus
Tunica serosa
- thin layer of loose CT rich in blood vessels, lymph vessels, and adipose tissue
- covered by simple sqaumous epithelium = mesothelium
- only for intraperitoneal organs - it’s tunica adventitia when overing retroperitoneal organs
What kind of tissue makes up the lips?
- folds of fibroelastic tissue
- skeletal tissue
Hard Palate
- bony roof of mouth
- covered by mucosa-stratified squamous epithelium w/ keratin
- ridges or rugae
In ruminants, the hard palate is a thick keratin layer called what?
dental pads
Soft Palate
- ruminants
- posterior fibrous and muscular extension of hard palate
- separates oral cavity from nasopharynx
In which direction are the mass of striated muscle fibers oriented in the tongue?
oriented in all directions
What is the lyssa?
cord like structure extending along ventral midline of tongue
consists of dense collagenous tissue, fat, skeletal m., and occasionally cartilage
well developed in carnivores
Four types of tongue papillae
- filiform
- fungiform
- vallate
- foliate
T/F: All tongue papillae have sensory fuction.
False.
All except filiform
gustatory
concerned with tasting or the sense of taste
Filiform papillae
- fairly small, cover most of surface
- elongated conical shape
- heavily keratinized
- provide friction to help move food
- no taste buds = non-gustatory
Fungiform papillae
- larger, less common
- mushroom shaped
- lightly keratinized
- interspersed among filiform p.
- few taste buds are present
Foliate papillae
- several parallel ridges on each side of tongue
- non-keratinized epithelium
- leaf-shaped
- few taste buds
- gustatory glands (Ebner’s glands) open into the sulcus
- rudimentary in humans
- commonly seen in rabbits, hares
Vallate (circumvallate) papillae
- largest papillae
- 8-12 arranged in pairs
- round in shape
- surrounded by a deep furrow (moat)
- numerous taste buds on lateral surface
- gustatory glands open into the sulcus
5 broad categories of tastants
- salty = sodium ions
- sour = hydrogen ions from acids
- sweet = sugars and related compounds
- bitter = alkaloids and certain toxins
- umami = glutamate
Brachydont Teeth
- “brachy” = short
- do not grow after completion of eruption
- have a crown, neck, and root
ex - carnivores
Hypsodont Teeth
- “hypso” = height
- continuously erupting
- do not have definite crown, neck, and root
ex - ruminant cheek teeth, all equine teeth, rodent incisor teeth, canine teeth of pigs, elephant tusk
Enamel
- hardest component of human body
- consists of 96% hydroxyapatite
- no collagen present
- secreated by ameloblasts
What secretes enamel?
ameloblasts
Dentin
- harder than bone
- consists of 70% hydroxyapatite
- Type I collagen present
- secreted by odontoblasts
