Unit 9 Digestive System Notes -- part 1

Unit 9 Part 1 – Upper Digestive System 

I.                  Digestive System 

a.     Principal structure is a tube open at both ends, called the alimentary canal or gastrointestinal tract. 

b.     Food is digested by physical and chemical processes to be used by body cells.  

c.     Food breakdown undergoes 3 processes                                                             

i.      Digestion – Physical or chemical by digestive organs.                                                          

ii.      Absorption – Absorption of nutrients by alimentary canal.                                                       

iii.      Metabolism – Chemical breakdown and use or storage by body cells. 

II.     Digestive Tract 

a.     Lumen – Hollow tube 

b.     4 Layers                  


 i.      Mucosa or mucous membrane – Epithelial tissue, provides protection from body's acids and enzymes and lubrication for materials travelling through digestive tract                                                          

ii.      Submucosa – Contains blood vessels and nerves.                                                        

 iii.      Muscularis – Peristalsis                                                         

iv.      Serosa – Covering of digestive tube held to abdominal cavity by mesentery.  

III.           Mouth / Oral Cavity 

a.     Primary organ / Physical Digestion 

b.     Roof                                                             

 i.      Made up of hard palate (palatine and maxillary bones) and soft palate (muscle).                                                          

 ii.      Uvula prevents food and liquid from entering nasal cavity. 

c.     Floor                                                             

i.      Consists of tongue and its muscles.                                                          

ii.      Frenulum attaches tongue to floor.                                                       

iii.      Tongue divided into root, body, and tip and prepares food into bolus for swallowing.                                                        

iv.      Papillae – Elevations on tongue which contain taste buds 

d.     Walls                                                             

i.      Consist of sides of oral cavity. 

IV.            Teeth 

a.     4 Types                                                             

i.      Incisors (4) Cut food                                                          

ii.      Canines / Cuspids (2) Tear food                                                       

 iii.      Premolars / Bicuspids (4) Crush food                                                        

 iv.      Molars / Tricuspids (6) – Grind food 

b.     20 baby / milk teeth present by age 2

c.     32 permanent teeth present by age 17-24

d.     First tooth present at 6 months and first permanent tooth at about age 6. 

V.               Anatomy of the Tooth 

a.     Crown                                                             

i.      Visible portion covered by enamel, dentin, and cementum.                                                          

 ii.      Center contains pulp cavity (blood, nerves, lymphatic vessels, and connective tissue. 

b.     Neck                                                            

i.      Narrow portion surrounded by gum tissue. 

c.     Root                                                            

i.      Fits into socket of upper or lower jaw. 

VI.            Salivary Glands 

a.     Accessory Organ / Chemical Digestion                                                             

i.      Parotid – Largest, located in front of and below ears.                                                          

 ii.      Submandibular – Open into mouth on sides of frenulum.                                                       

 iii.      Sublingual – Open into floor of mouth. 

b.     Saliva contains mucus and enzyme called amylase.                                                             

i.      Mucus – Moistens food for transport down GI tract.                                                          

ii.      Amylase – Chemical breakdown of carbohydrates.  

VII.        Pharynx 

a.     Primary Organ / Physical Digestion                                                            

i.      Tube like structure for passage of food and air. 

VIII.     Esophagus 

a.     Primary Organ / Physical Digestion                                                            

 i.      Tube which connects pharynx with stomach.                                                          

ii.      Found posterior to the trachea – the esophagus has no rings of cartilage holding it open