Digestive System

• Digestion?

  ★ The process in which large complex

  molecules (carbohydrates, lipids,

  proteins, nucleic acids) are broken

  down into simpler monomers which

  can be absorbed by the body.
• Mechanical Digestion

  ★ There is no chemical

  change in the food. The

  food is simply broken

  down into smaller pieces

  and mixed with digestive

  juices secreted in the

  body.
• Chemical Digestion

  ★ There is a chemical

  change in the food. The

  polymers are broken

  down into monomers

  commonly by hydrolysis

  reactions.
• Process of Digestion: + Ingestion - getting food into the

  mouth

  + Propulsion - moving foods from one

  region of the digestive system to

  another

  + Absorption - end products of

  digestion is absorbed in the blood or

  lymph

  + Defecation - elimination of

  indigestible substances such as feces
• Alimentary Canal

  ★ Continuously coiled

  hollow tube that runs

  from the mouth to the

  anus.

  ★ Includes mouth,

  esophagus, pharynx,

  stomach, small intestine,

  large intestine, anus.
• Accessory digestive

  organs

  ★ Secrete digestive juices

  by ducts into the

  alimentary canal.

  ★ Includes salivary glands,

  teeth, pancreas, liver,

  gall bladder.
• Mouth

  ★ mastication (chewing of

  food)

  ★ mixing masticated food

  with saliva

  ★ initiation of swallowing food

  by tongue

  A full set of adult teeth is 32

  
  

  Alimentary canal starts here***
• Saliva

  ★ mixture of mucus and

  serous fluids

  ★ contains salivary amylase

  to start digestion

  ★ dissolves chemicals so they

  can be tasted
• Teeth ★ The role is to masticate

  food

  ★ Humans have 2 sets of

  teeth:

  1. Deciduous (baby or

  milk teeth)

  B. 20 teeth are

  fully formed by age

  two
• Esophagus

  ★ runs from pharynx to

  stomach through the

  diaphragm

  ★ conducts food by

  peristalsis (slow rhythmic

  squeezing)

  ★ passageway for food only ★ Epiglottis - prevents

  choking and food going to

  wrong direction.
• Stomach

  ★ acts as a storage tank for

  food

  ★ site of food breakdown ★ delivers chyme (processed

  food) to the small intestine

  ★ Filled with hydrochloric acid

  (hCl) that kills bacteria

  and activates the enzyme

  in the stomach.
• Small Intestine

  ★ site of nutrient absorption

  into the blood

  ★ the body’s major digestive

  organ; all digestion of food

  is completed in this organ.

  1. Duodenum - where liver

  and pancreas are

  connected

  B. Jejunum - middle

  C. Illeum - where

  absorption takes place
• Large Intestine

  ★ Larger in diameter, but shorter

  than the small intestine

  ★ Absorption of water and

  elimination of waste material.

  2 Parts: ★ Colon - absorb remaining water

  contents

  ★ Appendix - accumulation of

  lymphatic tissue that sometimes

  becomes inflamed.

  
  

  Anus is the end of the alimentary canal***
• Liver

  ★ largest gland in the body

  ★ located on the right side of

  the body under the

  diaphragm

  ★ process, breaks, builds and

  stores carbohydrates and

  amino acids

  Accessory organs start here***
• Gall Bladder

  ★ stores bile from the liver by

  a way of the cystic duct

  ★ bile is introduced into the

  duodenum in the process of

  fatty food

  ★ gallstones can cause

  blockages
• Pancreas

  ★ secretes hormones for

  glucose control

  A. Insulin - lowers blood

  glucose

  B. Glucagon - raises

  blood glucose
• Salivary glands are located in the mouth and produce saliva.
• What is nutrient?

  ★ Substance used by the body for growth, maintenance and

  repair. Macronutrients are those which are required in large

  amounts while Micronutrients are required in small amounts.
• Carbohydrates?

  ★ body’s main source of energy

  ★ most are derived from plants except from

  milk and small amounts of glycogen from

  meats
• Lipids?

  ★ saturated fats from animal products

  ★ unsaturated fats from nuts, seeds, and

  vegetable oils
• Proteins?

  ★ complete proteins contains all the

  essential amino acids; most are from

  animal products

  ★ legumes and beans have also proteins, but

  are incomplete.
• Vitamins?

  ★ releasing energy from food

  ★ repair and growth of tissues

  ★ resisting infection and disease

  ★ regulating chemical reactions in the body
• A

  fish, milk, vegetables,

  eggs and cheese eyesight, healthy skin

  C

  fruit and vegetables healthy teeth and gums,

  avoiding scurvy

  B1

  Whole-grain foods, nuts, and meat breaking down

  carbohydrates

  D

  animal products. Also

  made in the body when

  the sun shines on the skin.

  absorbing calcium and

  phosphorous, avoiding rickets.
• Digestive Enzymes are classified by

  the type of food they affect. There are main types:

  A. carbohydrate/amylase -

  breaks carbohydrates into simpler sugars

  B. protease - breaks proteins into amino acids

  C. lipase - breaks fat into fatty acids and glycerol