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The Digestive System

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Chapter #15 The Digestive System Chapter 15.1 Digestion is the mechanical and chemical breakdown of foods and the absorption of the resulting nutrients by cells. – PowerPoint PPT presentation

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Title: The Digestive System


1
Chapter 15
  • The Digestive System

2
Chapter 15.1
  • Digestion is the mechanical and chemical
    breakdown of foods and the absorption of the
    resulting nutrients by cells.
  • The digestive system consists of the alimentary
    canal, which extends about 9 meters (27 feet or
    900 cm) from the mouth to the anus.

3
Alimentary Canal
  • Mouth
  • Pharynx
  • Esophagus
  • Stomach
  • Small Intestine
  • Large Intestine
  • Rectum
  • Anus

4
  • Mouth Mechanical breakdown of food begins
    chemical digestion of carbohydrates (bread).
  • Salivary glands secrete saliva, which contains
    enzymes that initiate breakdown of carbohydrates.
  • Pharynx connects mouth with esophagus.

5
  • Esophagus peristalsis pushes food to stomach.
  • Peristalsis wavelike motion that propels food.
  • Stomach secretes acid and enzymes. Mixes food
    with secretions to begin enzymatic digestion of
    proteins.

6
  • Small Intestine mixes food with bile and
    pancreatic juice. Final enzymatic breakdown of
    food molecules main site of nutrient absorption.
  • Liver produces bile, which emulsifies fat.
  • Gallbladder stores bile and introduces it into
    small intestine.
  • Pancreas produces and secretes pancreatic juice,
    containing digestive enzymes and bicarbonate
    ions, into sm. Intestine.
  • Accessory organs are organs that are not a direct
    route of the digestive system.

7
  • Large intestine absorbs water and electrolytes to
    form feces.
  • Rectum regulates elimination of feces.
  • Anus eliminates feces.
  • The digestive system is a tube, open at both
    ends, that has a surface area of 186 square
    meters.
  • The main function is to supply body with
    nutrients.

8
15.2 General Characteristics
  • 3 parts of the small intestine
  • Duodenum
  • Jejunum
  • Ileum

9
Alimentary Canal
  • Mucosa or mucous membrane the inner most layer.
    Contains glands that secrete mucus and digestive
    enzymes. Carries on secretion and absorption.
    Also, has projections that increase the surface
    area. Lumenpassageway.
  • Submucosa contains loose connective tissue,
    glands, blood vessels, lymphatic vessels, and
    nerves. Carry away absorbed materials.

10
  • Muscular layer produces the movements.
  • Serosa or serous layer the outer covering of the
    digestive tube. Secretes fluid that lubricates
    the tubes outer surface so organs slide freely
    against one another.

11
15.3 The Mouth
  • The mouth receives food and begins digestion by
    mechanically reducing the size of food and mixes
    them with saliva.
  • Oral cavity includes the chamber between the
    palate and tongue.
  • Palate forms the roof of the oral cavity and is
    made of a hard palate (front) and Soft palate
    (rear).
  • Tongues function is to move food toward the
    palate. Made out of skeletal muscle.

12
  • During swallowing, muscles draw the soft palate
    and uvula upward to separate the oral and nasal
    cavities.
  • Salvia cleanse the mouth and teeth, dissolve
    chemicals necessary to tasting food, and help in
    the formation of food bolus.

13
Tonsils
  • Palatine are lymphatic tissue in the back of the
    mouth, on either side of the tongue and closely
    associated with the palate. Help to fight
    infection.
  • Pharyngeal or adenoids are on the posterior wall
    of the pharynx. They can be removed.
  • Tonsillectomy tonsil are surgically removed.

14
Teeth
  • Humans have 2 sets of teeth.
  • Primary teeth or deciduous usually erupt at
    6months-4 years of age. 20 primary teeth. 10
    upper and 10 lower.
  • Secondary teeth or permanent consist of 32 teeth.

15
  • Good dental hygiene is essential because once
    damaged, enamel cannot be replaced.
  • Enamel cover the crown. White and shiny.
  • Dentin is found beneath the enamel. Dentin is a
    substance similar to bone.
  • Pulp cavity contains blood vessels, nerves, and
    connective tissue.
  • Root canals contains the root.

16
Teeth
  • 4 types of teeth
  • Incisors (Front 4 teeth) bite off pieces of food.
  • Cuspid grasp and tear food.
  • Bicuspids or premolars grind food.
  • Molars grind food.

17
15.4 Salivary Glands
  • The salivary glands secret saliva.
  • Saliva moistens food particles, helps them bind,
    and begins the chemical digestions of
    carbohydrates.
  • Saliva dissolves food so that they can be tasted.
  • 2 types of secretions from the salivary glands.
  • Amylase digestive enzyme in mouth, stomach,
    pancreas.
  • Mucus which binds with food particles to
    lubricate for swallowing.

18
Types of Salivary Glands
  • Parotid glands the largest.
  • Submandibular glands located in the floor of the
    mouth.
  • Sublingual glands the smallest of the salivary
    glands, are on the floor of the mouth.

19
15.5 Pharynx and Esophagus
  • Pharynx connects the nasal and oral cavities with
    the larynx and esophagus.
  • 3 parts
  • Nasopharynx communicates with the nasal cavity
    and provides a passageway for air during
    breathing.
  • Oropharynx is posterior to the soft palate and
    inferior to the nasopharynx. It is the passageway
    for food moving downward from the mouth and for
    air moving to and from the nasal cavity.
  • Laryngopharynx just inferior to the oropharynx,
    is a passageway to the esophagus.

20
  • Epiglottis closes off the top of the trachea
    (windpipe) so food is less likely to enter.

21
15.6 Stomach
  • The stomach is a J-shaped , pouchlike organ that
    hangs inferior to the diaphragm in the upper left
    portion of the abdominal cavity and has a
    capacity of about 1 liter.
  • The stomach has thick folds of mucosal and
    submucosal layers and disappear when the stomach
    wall is distended.

22
Stomach
  • The stomach is divided into four regions.
  • Cardiac
  • Fundic is the area that acts as a temporary
    storage area for ingested food.
  • Body
  • Pyloric
  • Fatty food stay in the stomach the longest.

23
Gastric Secretions
  • Gastric juice
  • Hydrochloric acid
  • Pepsin begins to digest protein
  • Chyme is a semifluid paste of food particles and
    gastric juice.

24
Time Spent in organs
  • Mouth a few minutes
  • Esophagus a few minutes
  • Stomach 4 hours
  • Small Intestine 12 hours
  • Large Intestine 5 hours
  • Total time in digestive system 21 hours.

25
15.7 Pancreas
  • The pancreas make three different enzymes. One
    enzyme break down fats (pancreatic lipase), one
    enzyme break down protein (proteolytic), and the
    third enzymes break down carbohydrates.

26
15.8 Liver
  • The liver is the largest organ in the body it is
    the heaviest organ in the body at around 3
    pounds.
  • It makes the chemical bile.
  • Bile is a green liquid that breaks large fat
    droplets into small fat droplets.
  • Gallbladder is a small, baglike part located
    under the liver. It stores bile until it is
    needed by the small intestine.

27
Hepatitis
  • Hepatitis is an inflammation of the liver.
  • Types of Hepatitis
  • Hepatitis A spreads by contact with food or
    objects contaminated with virus-containing feces.
  • Hepatitis B spreads by contact with
    virus-containing body fluids, such as blood,
    saliva, or semen.

28
  • Hepatitis C is believed to be responsible for
    about ½ the cases of hepatitis. Transmitted in
    blood-by sharing razors or needles, from pregnant
    woman to fetus, or in blood transfusions.
  • Hepatitis D occurs in people already infected
    with hepatitis B. It is blood borne and
    associated with blood transfusions and
    intravenous drug use.

29
  • Hepatitis E virus is usually transmitted in the
    water contaminated with feces.
  • Hepatitis F passes from feces and can infect
    other primates.
  • Hepatitis G accounts for many cases of fulminant
    hepatitis.

30
15.9 Small Intestine
  • Small Intestine is a tubular organ that extends
    from the pyloric sphincter to the beginning of
    the large intestine. This is where most of the
    nutrients are absorbed.
  • Receives secretions from the pancreas and liver.
  • Completes digestion, absorbs the products of
    digestion, and transports the residues to the
    large intestines.

31
  • The small intestines constits of three portions.
  • Duodenum
  • Jejunum
  • Ileum
  • Mesentery suspense the small intestine.
  • Intestinal villi is the inner wall of the small
    intestine appears velvety.
  • ¼ of feces is dead epithelial cells from the sm.
    Intestine.

32
  • The small intestine compared to the large
    intestine is narrower and longer.
  • Heartburn is caused by acid moving from the
    stomach into the esophagus.
  • Animals that do not have a digestive system
    absorb nutrients through their body covering.
    Example Tapeworm.
  • Plant eating animals have longer digestive
    systems because of the intake of cellulose which
    is not absorbed by the intestine.
  • Digestion is the breaking down of food into
    small, usable molecules usually glucose.

33
Digestive enzymes
  • Salivary glands make chemicals that digest only
    carbohydrates.
  • Pancreas makes chemicals that digest fat,
    protein, and carbohydrates.
  • Liver makes chemicals that digest only fat.
  • Stomach makes chemicals that digest only protein.
  • Small intestine makes chemicals that digest
    protein and carbohydrates.
  • Large intestine makes no chemicals to digest food.

34
15.10 Large Intestine
  • Large intestine is so named because its diameter
    is greater than that of the small intestine.
    Large intestine are about 1.5 meters long, and
    begins in the lower right side of the abdominal
    cavity.
  • The large intestine absorbs water and
    electrolytes.

35
  • The 4 parts of the large intestine
  • Cecum is the beginning
  • Colon is divided into 4 portions the ascending,
    transverse, descending, and sigmoid colons. The
    colon is home to 100 trillion bacteria.
  • Rectum extends about 5 cm below the tip of the
    coccyx (tailbone).
  • Anal canal the last 2.5 to 4 cm of the large
    intestine.
  • Feces include materials that were not digested or
    absorbed, water, electrolytes, mucus, intestinal
    cells, and bacteria. Feces is about 75 water.
    Feces pungent odor results from a variety of
    compounds that bacteria produce.

36
15.11 Nutrition and Nutrients
  • Nutrition is the study of nutrients and how the
    body utilizes.
  • Nutrients all the chemicals that food is made up
    of which in include carbohydrates, lipids,
    proteins, vitamins, minerals, and water.
  • Nutrients that human cells cannot synthesize,
    such as certain amino acids, are called essential
    nutrients.

37
Carbohydrates
  • Are organic compounds used primarily to supply
    energy for cellular processes.
  • Found in foods such as starch and sugar
  • Not stored in large amounts in the body
  • Needed in greatest amount each day.
  • Cellulose is a complex carbohydrate that is
    abundant in food- it gives celery its crunch.
    Humans cannot digest so cellulose provides bulk
    (fiber or roughage) which facilitates food
    movement through the digestive system.

38
Lipids
  • Lipids are organic compounds that include fats,
    oils, and fatlike substances.
  • Found in foods such as butter and oil
  • The food that is often stored and used later as
    an energy source.
  • The nutrient stored under the skin and around
    body organs.

39
Protein
  • Proteins are polymers of amino acids with a wide
    variety of functions.
  • Used to form muscle, bone, and skin
  • Food rich in protein include meats, fish,
    poultry, cheese, nuts, milk, eggs, and cereals.

40
Vitamins
  • Are organic compounds that are required in very
    small amounts for normal metabolic processes. Not
    an energy source.
  • Riboflavin and niacin are examples
  • Vitamins allows cells to use carbohydrates and
    proteins.
  • Vitamins are needed for growth and tissue repair.
  • Amount given as RDA. Recommended Daily
    Allowance.

41
Minerals
  • Are elements other than carbon that are essential
    in human metabolism.
  • Found on the Periodic Table. Calcium, iron,
    potassium, sodium, zinc, and magnesium are
    examples.
  • Need in very small amounts
  • May cause anemia or muscle twitching if missing
    from diet.
  • Amount Given as RDA.
  • Not an energy source.

42
Water
  • Water is needed to cool the body, to chemical
    reactions in the body, and to carry away body
    waste.
  • 50 to 60 of the human body is water.
  • The average adult needs about 2 liters of water a
    day.

43
Diets
  • Balanced diet is a diet with the right amount of
    each nutrient.
  • Malnutrition if a persons diet lacks essential
    nutrients or a person fails to use available
    foods.
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