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Human Digestion -Ch. 21.1. Section Objectives: Interpret the different functions of the digestive system organs. Outline the pathway food follows through the digestive tract. Identify the role of enzymes in chemical digestion . Human Digestion.

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human digestion ch 21 1

Human Digestion -Ch. 21.1

Section Objectives:

Interpret the different functions of the digestive system organs.

Outline the pathway food follows through the digestive tract.

Identify the role of enzymes in chemical digestion.

human digestion
Human Digestion
  • This part of the life process of NUTRITION-> process by which an organism obtains and utilizes food
overview food processing occurs in four stages
Overview: Food processing occurs in four stages
  • Ingestion: taking in food
  • Digestion: mechanical and chemical breakdown of food so that it can be absorbed by the cells
  • Absorption: cells lining the digestive tract take up (absorb) small nutrient molecules
  • Elimination: undigested material passes out of the digestive tract
human digestion a 2 part process that changes food into a form useable by the body cells
Human Digestion~ a 2 part process that changes food into a form useable by the body cells
  • 1. Mechanical digestion – physical breakdown of large pieces of food into smaller ones
  • 2. Chemical digestion – hydrolysis – the splitting of large insoluble molecules in small, soluble molecules with the use of water and enzymes ( in other words; breaking complex molecules into simple ones)

The process of chemical digestion ( hydrolysis) is regulated by enzymes

examples of chemical digestion
Examples of chemical Digestion:
  • 1. Carbohydrates+ water -> simple sugars (glucose for instance)
  • 2. Proteins+ water -> amino acids
  • 3. Lipids+ water -> 3 fatty acids +gylcerol
human digestive system
HUMAN DIGESTIVE SYSTEM
  • Human digestive tract = GI (gastrointestinal) Consists of a continuous one way food tube (mouth to anus)
mouth
Mouth
  • Functions
    • mechanical digestion
      • teeth
        • break up food
    • chemical digestion (saliva)
      • amylase enzyme
        • digests starch
      • mucus
        • protects soft lining of digestive system
        • lubricates food for easier swallowing
      • buffers
        • neutralizes acid to prevent tooth decay
      • anti-bacterial chemicals
        • kill bacteria that enter mouth with food

All thatin spit!

human digestive system8
HUMAN DIGESTIVE SYSTEM
  • 1. Mouth: (oral cavity) ingests food
  • 2. Teeth: function in mechanical breakdown of food, increases surface area of food for enzyme action
  • 3.Tongue: acts as a plunger to push food back into the throat (pharynx) taste buds are located on the surface of the tongue
slide9

mouth

break up food

digest starch

kill germs

moisten food

human digestive system10
HUMAN DIGESTIVE SYSTEM
  • 4. Pharynx: food is pushed by tongue to back of throat, initiates swallowing – food is now in the form of a bolus
    • Epiglottis: flap that prevents choking
  • 5. Esophagus: muscular tube that moves food from mouth to the stomach by process of peristalsis:wave of muscular contractions that moves chewed food to stomach
swallowing not choking
Swallowing (& not choking)
  • Epiglottis
    • flap of cartilage
    • closes trachea (windpipe) when swallowing
    • food travels down esophagus
  • Peristalsis
    • involuntary muscle contractions to move food along
stomach
Stomach
  • Functions
    • disinfect food
      • hydrochloric acid = pH 2
        • kills bacteria
    • food storage
      • can stretch to fit ~2L food
    • digests protein
      • pepsin enzyme

But the stomach is made out of protein!

What stops the stomach from digesting itself?

mucus secreted by stomach cells protects stomach lining

slide13

stomach

kills germs

break up food

digest proteins

store food

mouth

break up food

digest starch

kill germs

moisten food

sphincter

sphincter

ulcers
Ulcers

Free of H. pylori

Colonized by H. pylori

  • Used to think ulcers were caused by stress
    • tried to control with antacids
  • Now know ulcers caused by bacterial infection of stomach
    • H. pylori bacteria
    • now cure with antibiotics

inflammation of stomach

inflammation of esophagus

H. pylori

cell damaging proteins

(VacA)

inflammatory proteins

(CagA)

cytokines

helper T cells

neutrophil cells

white blood cells

small intestine
Small intestine
  • Functions
    • digestion
      • digest carbohydrates
        • amylase from pancreas
      • digest proteins
        • trypsin & chymotrypsin from pancreas
      • digest lipids (fats)
        • bile from liver & lipase from pancreas
    • absorption
      • nutrients move into body cells by:
        • diffusion
        • active transport

This iswhere all thework is done!

absorption in small intestines
Absorption in Small Intestines
  • Absorption through villi & microvilli
    • finger-like projections
    • increases surface area for absorption

SMALL INTESTINES6 meters long,but can stretchto cover a tennis court

slide17

small intestines

breakdown food

- proteins

- starch

- fats

absorb nutrients

mouth

break up food

digest starch

kill germs

moisten food

stomach

kills germs

break up food

digest proteins

store food

liver

produces bile

- stored in gall bladder

break up fats

pancreas

produces enzymes to

digest proteins & starch

pancreas accessory organ
Pancreas ~ accessory organ
  • Produces digestive enzymes
    • digest proteins
      • trypsin, chymotrypsin
    • digest starch
      • amylase
    • digest lipids
      • lipase
  • Buffers
    • neutralizes acid from stomach

smallintestine

pancreas

slide19

pancreas

produces enzymes to

digest all foods

mouth

break up food

digest starch

kill germs

moisten food

stomach

kills germs

break up food

digest proteins

store food

liver gall bladder accessory organs
Liver & Gall Bladder ~accessory organs
  • Produces bile
    • breaks up fats
    • gallbladder only stores bile
      • that’s why you can have your gall bladder removed

bile contains colors from old red blood cells collected in liver =

iron in RBC rusts & makes feces brown

slide21

liver

produces bile

- stored in gall bladder

break up fats

mouth

break up food

digest starch

kill germs

moisten food

stomach

kills germs

break up food

digest proteins

store food

pancreas

produces enzymes to

digest proteins & starch

large intestines colon
Large intestines (colon)
  • Function
    • re-absorbs water
      • use ~9 liters of water every day in digestive juices
        • if don’t reabsorb water would die of dehydration
      • > 90% of water re-absorbed
        • not enough water re-absorbed
          • diarrhea
          • can be fatal!
        • too much water re-absorbed
          • constipation
      • reabsorb by diffusion
you ve got company
You’ve got company!
  • Living in the large intestine is a community of helpful bacteria
    • Escherichiacoli:E.coli
      • digest cellulose
        • digests fruits & vegetables
      • produce vitamins
        • vitamin K & B vitamins
      • BUT generate gases
        • by-product of bacterial metabolism
        • methane, hydrogen sulfide
        • STINKY!

PEE-YOO!

slide24

large intestines

absorb water

mouth

break up food

digest starch

kill germs

moisten food

stomach

kills germs

break up food

digest proteins

store food

liver

produces bile

- stored in gall bladder

break up fats

small intestines

breakdown food

- proteins

- starch

- fats

absorb nutrients

pancreas

produces enzymes to

digest proteins & carbs

rectum
Rectum
  • Last section of large intestines
    • eliminate feces through anus
    • what’s left over?
      • undigested materials
        • mainly cellulose from plants
        • called roughage or fiber
        • keeps everything moving & cleans out intestines
      • masses of bacteria

So don’t forget to wash your hands!

appendix
Appendix

Vestigial organ

some digestive homeostasis disorders
SomeDigestive Homeostasis Disorders
  • 1.Constipation– person has uncomfortable or infrequent bowel movements results from sluggish peristalsis that allows excess water to be removed from feces (fecal matter hardens)- may result from insufficient fiber in diet
  • 2. Diarrhea– opposite of constipation– associated with intestinal disturbances caused by infections or stress– prolonged diarrhea may result in severe dehydration
  • 3. Gall stones– small hard particles made of cholesterol which form & collect in gall bladder- may block the bile duct and cause pain
  • 4. acid reflux -backflow of stomach contents upward into esophagus
  • 5. appendicitis- inflammation of appendix
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