1. Digestive System

2. Organs of the alimentary Canal
Mouth
Pharynx
Esophagus
Stomach
Small intestine
Large intestine
* Salivary glands, liver, pancreas and gall bladder are accessory organs

3. Food is absorbed from small intestine bloodbody
Main functions:
digestion
Food is broken down:
Mechanically (chewing, bowl movements)
Chemically (enzymes, acids)
2. Absorption
Food is absorbed from small intestine bloodbody
3. Excretion

4. Mouth
Food enters DT through the oral cavity (lined with mucous membranes)
Lips (labia) protect its opening
Cheeks form the lateral walls
Hard palate forms anterior roof
Soft palate forms posterior roof
Uvula: fingerlike projection of soft palate
Tongue occupies the floor of the mouth
Lingual frenulum (fold of mucous membrane) secures tongue to floor of moth and limits its posterior movements

5. Mouth cont. Both types of digestion mechanical and chemical
Salivary glands secrete enzymes that break carbohydrates
Teeth help break down food by chewing

6. Mouth (salivary glands)
Three pairs of salivary glands secrete saliva into the mouth
Parotid glands:
Located close to our ears
Submandibular glands
below the mandible
Sublingual glands
Under the tongue
Saliva is a mixture of mucus and serous fluids
Mucus moistens +helps bind food together into a mass called bolus which eases swallowing
The serous portion contains an enzyme, amylase which begin starch digestion
Saliva also contains Abs which inhibit bacteria

7. Pharynx and Esophagus
Food passes from oral cavity to the pharynx  esophagus  stomach
Esophagus is lined with mucous membranes to allow food to pass easily
Epiglottis flips over the trachea to keep food from entering the trachea

8. Pharynx and Esophagus cont.
Swallowing:
A bolus of food is pressed backward into the pharynx by the tongue. This is the only step that is voluntary - the remaining steps occur by reflex.
Once the bolus reaches the pharynx several actions are initiated, the epiglottis swings backward to cover the larynx.
The tongue presses backward and a peristaltic contraction in the pharynx propels the bolus into the esophagus, where the actual act of swallowing takes place.

9. Esophagus Histology Mucosa: Sub mucosa: Muscularis externa: Serosa:
Innermost, moist layer that lines the cavity (lumen) of the organ
Consists of surface epithelium (stratified squamous)+ small amount of CT (lamina propria) +SM layer
*beyond the esophagus all epithelium is simple columnar
Sub mucosa:
covers the mucosa
Soft C.T layer contains BV, nerve endings, lymphatics
Muscularis externa:
2 Layer of SM cells (longitudinal muscle layer + circular muscle layer)
Serosa:
Outer most layer
Single layer of serous fluid producing cells- visceral peritoneum- covers the external surface of the esophagus
Mesentery is a membrane extension of the visceral peritoneum
S sq epith: resists friction+