The Digestive System:

Also known as the allomentry canal, it goes from the lips to the anus
transports food to anus
permits mechanical and chemical breakdown of material passed through
non-digestive food is wrapped in feces

The mouth, pharanx, esophogus, stomach, small intestine, large accessory and digestive glands link the wall of the digestive tract
accessory and digestive glands include: salivary glands, liver, pancreas, and the gall bladder

The Mouth:
consists of : the tounge, lingual papillae, teeth, and salivary glands
The Tounge: a muscular organ (skeletal muscle) used in mastification in mouth as well as speech and sound

Lingual Papillae: 4 different types of projections on tounge
circumvallae, fungiform, fillaform, foliate
Fillaform - .2-.3mm long, smallest of the 4 gives the tounge gray clor when full of bacteria (sick)
Fungiform - occur alone, few in number, less abundant than filliform, resemble mushrooms, come up in a straight line alone sulcus, and rounded
Circumvallae - 8-12 in number and are found in a row at the back of tounge, largest of the lingual papillae, slighlty keritanized, contain taste buds
Foliate - Rudamentary in humans, found in rabbits, look columnar, prominent taste buds

Teeth:
also used in mastication
slight role in speech production
there are primary and seconday teeth
about 32 in an adult mouth
there are three portions to a tooth:
crown - visible enaml
root - anchors teeth below gum line
neck - transition from crown to root

tooth also has a pulp cavity in which delecate vessels and nerves rest in a mucous connective tissue in the middle of tooth
cementum/dentin/enamal - hard parts of teeth
enamal and dentin make up the crown while cementum is below the crown
dentin is thickest in crown and covered in a 2-2.5mm coating of enamal ( hardest substanc in body about 90% phosphate) the enaml prevents fractures
Ameloblasts - produce enamal
dentin is a hard, elastic, yellowish and is the bulk and strength of the tooth morphologically similar to bone and is produced by odontoblasts
cementum - similar to bone in morphology - creates a sheet down in the root region - anchors the tooth and provides a protective covering

Saliva:
mixed secretion from large and small salivary glands ( we will not go into detail about small salivary glands)
there are three types of large salivary glands - parotid, submandibular, and sublingual
produce saliva which contains ptaylin that is used to break up simple starches and glycogen
saliva moistens mouth, softens food, and aids in swallowing
it secretes by way of the sympathetic nervous system
they contain serous and mucous and are considered to be a "mixed" gland for this reason

Allomentery Canal:
consists of the esophagus, stomach, small intestine, and large intestine
the lining of the digestive tract from esophagus to colon has layers which thickness and precence varies depending on loction in the body

the layers include:

1. the mucosa - the innermost layer with epitelia lining the lamina propria
2. musularis mucosa - small layer of smooth muscle about 2-3 cell layers thick
3. submucosa - connective tissue layer - made up of loose connective tissue
4. muscularis externa
5. peritoneum - mesothelium epithelium - fibrosa - serosa - about 2-3 cell layers thick

Aurbachs Plexus - layer in between two layers of muscularus externa
meissner's plexus - lies deep in the submucossa, helps regulate peristalsus

Esophagus:
25cm long
carries food from pharnx to stomach
good musculature
consists of stratified squamous keritanized and unkeritanized
tremendous amount of muscle
whole group of glands exist in the esophagus

Stomach:
connects esophagus with the small intestine
food collected in stomach is semi-solid and known as chyme
this is were a major portion of mechanical and chemical food breakdown occurs
the stoamch is divided into the cardiac, fundic, and pyloric regions
the stomach also has four different types of cells - chief cells, parietal cells, mucous cells, and enteroendocrine cells

Small Intestine:
4-5m long
tubular organ from phylorous of stomach to illium of the large intestine
the stomach is divided into three portions the Duodenum, Jejunum and the Ileum
this is where absorbtion of nutrients takes place