Digestive System

By: Francisco Colina-Salas


Digestion and absorption. Digestion is the breakdown of food into small molecules, which are then absorbed into the body.


  • Mouth: chewing breaks the food into pieces that are more easily digested, while saliva mixes with food to begin the process of breaking it down into a form your body can absorb and use.

  • Esophagus: to carry food, liquids, and saliva from the mouth to the stomach.

  • Stomach: secretes acid and enzymes that digest food.

  • Small Intestine: absorption of nutrients and minerals from food.

  • Large Intestine: absorb water from the remaining indigestible food matter and transmit the useless waste material from the body.

  • Anus: help get rid of the wastes

  • Liver: protein production and blood clotting to cholesterol, glucose and iron metabolism.

  • Pancreas: helps in digestion and regulates blood sugar.

  • Gallbladder: store and concentrate bile, a yellow-brown digestive liquid produced by the liver

Why is the digestion of large molecules essential?

The food molecules have to be small enough to be absorbed by the villi in the intestine through diffusion, facilitated diffusion or active transport and so large food molecules need to be broken down into smaller ones for absorption to occur.

Why are enzymes needed for digestion?

Enzymes are needed in the process of digestion as they are the biological catalysts which break down the large food molecules into smaller ones so that these can eventually be absorbed.

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Food Poisoning

  1. Illness caused by food contaminated with bacteria, viruses, parasites, or toxins

  2. Pain in the abdomen, vomiting, diarrhea, weakness, headaches, etc.

  3. More than 3M US cases per year

  4. Diarrhea medication and Pepto-Bismol


  1. Bowel movements (stools) that are loose and watery

  2. Pain in the abdomen, vomiting, watery or loose stools, sense of urgency to have a bowel movement.

  3. Diarrheal diseases account for 1 in 9 child deaths worldwide.

  4. Let it run its course or take over the counter medicines.

Skeletal System


Supports the body; protects internal organs; allows movement; stores mineral reserves; provides blood cell formation.


  1. Bones: produce blood cells (red marrow= red and white cells) (Yellow marrow= made of fat)
  2. Ligament: fibrous connective tissue which attaches bone to bone, and usually serves to hold structures together and keep them stable.
  3. Muscles : bones & muscles work together for movement
  4. Tendons : thick tissue connecting muscles to bones
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  1. The wear and tear our bones and joints experience over time
  2. Pain, stiffness, swelling, redness, decreased range of motion
  3. Therapy, surgery, pain medication
  4. More than 3M US cases per year


  1. A condition in which bones become weak and brittle
  2. Pain in the back, bone fracture or loss of height
  3. Lifestyle, hormones
  4. More than 3M US cases per year

  • Muscular System


    Permits movement of the body, maintains posture, and circulates blood throughout the body.

    Muscle Contraction

    • An action potential from a motor neuron triggers the release of Ca2+ ions from the sarcoplasmic reticulum
    • Calcium ions expose the myosin heads by binding to a blocking molecule (troponin complexed with tropomyosin) and causing it to move
    • The myosin heads form a cross-bridge with actin binding sites
    • ATP binds to the myosin heads and breaks the cross-bridge
    • The hydrolysis of ATP causes the myosin heads to change shape and swivel - this moves them towards the next actin binding site
    • The movement of the myosin heads cause the actin filaments to slide over the myosin filaments, shortening the length of the sarcomere
    • Via the repeated hydrolysis of ATP, the skeletal muscle will contract
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    1. Uncommon inflammatory disease that causes muscle weakness affecting both sides of your body. Polymyositis can make it difficult to climb stairs, rise from a seated position, lift objects or reach overhead.
    2. The muscle weakness associated with polymyositis involves the muscles closest to the trunk, such as those in your hips, thighs, shoulders, upper arms and neck. The weakness affects both the left and right sides of your body, and tends to gradually worsen.
    3. Medicine, Therapy, Surgery


    1. A weakness and rapid fatigue of muscles under voluntary control
    2. Muscle weakness, fatigue.
    3. 20K to 200K US cases per year
    4. Medication, Plasma Exchange, Thymectomy

    Nervous System


    Control of the body and communication among its parts.


    Central Nervous System: the complex of nerve tissues that controls the activities of the body. In vertebrates it comprises the brain and spinal cord.

    1. Brain
    2. Brain Stem
    3. Spinal Cord

    Peripheral Nervous System: the part of the nervous system that consists of the nerves and ganglia outside of the brain and spinal cord.

    1. Sensory Cells
    2. Motor Cells
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    Alzheimer's Disease
    1. A progressive disease that destroys memory and other important mental functions
    2. Mental decline, difficulty thinking and understanding, mental confusion, disorientation, delusion, inability to create new memories, inability to recognize common things, inability to do simple math, difficulty concentrating, making things up, confusion in the evening hours, or forgetfulness.
    3. More than 3M US cases per year
    4. Medicine, Exercise

    Parkinson's Disease

    1. A disorder of the central nervous system that affects movement, often including tremors.
    2. Tremor in the hands or limbs, can occur at rest, can be postural.
    3. 200K to 3M US cases per year
    4. Antiviral, Exercise