SCIE 3001
1 - Nature of Living Things
1.4 Human Organ Systems and Health
4 - Cycles and Seasons
5 -Structure of the Earth, and Earth Movements

Unit 1 - Living Things

1.4 Human Organ Systems and Health

Cells, Tissues, and Organs

1. Living things are made of cells which are orginized as tissues to form organs.

  • All living things are made of cells.
  • The cell is the smallest unit of life.
  • A tissue is large groups of cells all doing the same function.
  • One kind of tissue is made up of one kind of cell.
    • Hair tissue is made up only of hair cells.
    • Nerve tissue is made up only of nerve cells.
    • Sweat gland tissue is made up only of sweat gland cells.
  • Living things have many different kinds of cells which make up many different kinds of tissue.
  • The are four different kinds of tissues
    • Epithelial- protect the body from injury and infection. Example the skin and the inner surfaces of the body such as the surface of the lungs, stomach, intestines, and blood vessels.
    • Connective- strong but may also stretch to frame and support our bodies. Includes bone, cartilage, and fatty tissue.
    • Nerve - Send information from one part of our bodies to another by collecting information from our sensory organs or passing this information to other organs.
    • Muscle - Muscle tissues contract and relax. There are three types of muscle cells.
      • Voluntary muscles move by choice and are attached to our skeletons.
      • Ssmooth muscle are the muscles of our lungs, stomach, and intestines.
      • Cardiac muscle are in the heart.
  • Organs are groups of tissues that work together to do a particular task(s).
    • Skin is an organ made of hair tissue, oil and sweat gland tissues, nerve tissue, blood tissue, and many other tissues.
    • Eyes are organs made of nerve tissue, blood vessel tissue, muscle tissue, lens tissue, pupil tissue, and many more types of tissues.
    • Stomach is an organ made up of smooth muscle, connective tisue, nervous tissue, blood and epithelial tissue.
sstomach tissues

The digestive system is a group of organs working together to convert food into energy and basic nutrients to feed the entire body. Food passes through a long tube inside the body known as the alimentary canal or the gastrointestinal tract (GI tract).

The alimentary canal is made up of the:

  1. oral cavity
  2. pharynx,
  3. esophagus
  4. stomach
  5. small intestines (duodenum and Illium)
  6. large intestines.

In addition to the alimentary canal, there are several important accessory organs that help your body to digest food but do not have food pass through them.

Accessory organs of the digestive system include the

  1. teeth
  2. tongue,
  3. salivary glands
  4. liver
  5. gallbladder
  6. pancreas.

To achieve the goal of providing energy and nutrients to the body, six major functions take place in the digestive system:

  1. Ingestion
  2. Secretion
  3. Mixing and movement
  4. Digestion
  5. Absorption
  6. Excretion


Food begins its journey through the digestive system in the mouth.

Inside the mouth are many accessory organs that aid in the digestion of food—

  1. Tongue
    • Made up of several pairs of muscles covered in a thin, bumpy, skin-like layer
    • The taste buds on the surface of the tongue detect taste food
    • Helps to push food toward the back part of the mouth for swallowing
  2. Teeth
    • 32 small, hard organs to cut, chop and grind food.
    • Made of a bone-like substance called dentin and covered in a layer of enamel.
    • Teeth are living organs and contain blood vessels and nerves
  3. Salivary glands.
    • 3 sets of salivary glands
    • Produce saliva which helps to moisten food and begins the digestion of carbohydrates.
    • Saliva lubricates food as it passes through the mouth, pharynx, and esophagus

Pharynx or throat

  1. Funnel-shaped tube connected to the back of the mouth.
  2. Passes chewed food from the mouth to the esophagus.
  3. Plays an important role in the respiratory system, as air from the nasal cavity passes through the pharynx on its way to the lungs.
  4. Serves two different functions so it has a flap of tissue known as the epiglottis that acts as a switch to route food to the esophagus and air to the larynx.


  1. Muscular tube connecting the pharynx to the stomach
  2. Has a muscular ring called a sphincter to close of the end of the esophagus and trap food in the stomach.


  1. The stomach is a muscular sac that is located on the left side of the abdominal cavity
  2. In an average person, the stomach is about the size of their two fists placed next to each other. S
  3. Storage tank for food so that the body has time to digest large meals properly.
  4. Aso contains hydrochloric acid and digestive enzymes

Small Intestine

  1. A long, thin tube about 1 inch in diameter and about 10 feet long T
  2. Takes up most of the space in the abdominal cavity. C
  3. Coiled like a hose and the inside surface is full of many ridges and foldswhich maximize the digestion of food and absorption of nutrients.
  4. By the time food leaves the small intestine, around 90% of all nutrients have been extracted from the food that entered it.

Liver and Gallbladder

  1. The liver is an accessory organ of the digestive system
  2. The liver has many different functions in the body, but the main function of the liver in digestion is the production of bile and its secretion into the small intestine.
  3. The gallbladder stores and recycles excess bile from the small intestine so that it can be reused for the digestion of subsequent meals.


  1. Large gland about 6 inches long and shaped like short, lumpy snake
  2. Secretes digestive enzymes into the small intestine to complete the chemical digestion of foods.

Large Intestine

  1. Llong, thick tube about 2 ½ inches in diameter and about 5 feet long.
  2. Asorbs water and contains many symbiotic bacteria that aid in the breaking down of wastes to extract some small amounts of nutrients.
  3. Feces in the large intestine exit the body through the anal canal.


Concept by Kishore Lal. Programmed by Kishore Lal... Copyright © 2015 Kishore Lal. All rights reserved.