Digestive System

Digestive Process

1. Ingestion2. Movement of food3. Digestion4. Absorption5. Defecation

Humans track = Alimentary Canal30’ of digestive tract!

General Histology

• 4 tissue layers (in to out)– Mucosa – inner lining of track– Submucosa – binds to muscle layer. Contains

numerous blood and lymph vessels for absorption contains nerves that control tract secretion

– Muscularis – voluntary skeletal muscle in upper (mouth, pharynx and upper esophagus) and involuntary smooth in rest.]

– Serosa – secretes serous fluid to allow tract to glide easily against other organs

General Histology

• All organs are covered in peritoneum made of large folds containing blood and lymphatic vessels and nerves.

Parietal – lines abdominal cavity

Visceral – covers digestive organs

Movements of the Alimentary Canal

• Mixing – caused by rhythmic contractions of smooth muscle in small segments of the tube

• Propelling – caused by wavelike contractions called peristalsis (click for awesome video!!!)

– Circular muscle changes tube diameter– Longitudinal muscle changes tube length

Mechanical verses Chemical

• Mechanical digestion occurs by breaking, tearing, or churning (teeth, churning of stomach…)• Chemical digestion involves

chemicals in tract breaking food down (starch into glucose by amalyse)

Nervous Control of Tract

• Controlled mainly by Vagus nerve of A.N.S.• Parasympathetic nerve –

increases digestive activity• Sympathetic nerve – decreases

activity

4 classes of essential nutrients

Essential Amino Acids: most animals require 8 that they cannot synthesis.

• Missing 1 or more can cause protein deficiency…the most common type of malnutrition.

4 classes of essential nutrients

Essential Fatty Acids: animals can synthesize most f.a. exception: Cannot make certain unsaturated f.a.

Ex: humans require linoleic acid for membrane phospholilpids

4 classes of essential nutrients

Vitamins: organic molecules required in very small amounts

• Serve as co-enzymes• Classified as water-soluble or fat-soluble

See page 795

4 classes of essential nutrients

Minerals• Inorganic nutrients required in small amounts

that cannot be synthesized• Vertebrates need large amounts of Ca and P

for bone building and nerve and muscle function.

• Page 796

Issues with missing nutrients• Undernourishment – result of a diet

consistently supplied with less chemical energy than the body requires

–Body uses up stored fats and carbohydrates–Body starts to use protein as fuel»Causes muscles to waste»Brain may become protein deficient

Death or irreversible damage can occur

Issues with missing nutrients

• Malnourishment – long term absence of one or more essential nutrients–Can cause deformities, disease, or even

death.– Ex. Lack of phosphorus in cattle = broken

bones–Humans eating a mostly rice diet can cause

vitamin A deficiency = blindness or death.

Goiter – thyroid gland effected by an iodine deficit

BODY STORY: GERMS

Molecular gastronomy is a sub discipline of food science that seeks to investigate, explain and make practical use of the physical and chemical transformations of ingredients that occur while cooking, as well as the social, artistic and technical components of culinary and gastronomic phenomena in general.