Human Digestion -Ch. 21.1

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.

2
Human Digestion

• This part of the life process of NUTRITION-gt
  process by which an organism obtains and utilizes
  food

3
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

4
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

5
Examples of chemical Digestion

• 1. Carbohydrates water -gt simple sugars (glucose
  for instance)
• 2. Proteins water -gt amino acids
• 3. Lipids water -gt 3 fatty acids gylcerol

6
HUMAN DIGESTIVE SYSTEM

• Human digestive tract GI (gastrointestinal)
  Consists of a continuous one way food tube (mouth
  to anus)

7
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!
8
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

9
(No Transcript)
10
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

11
Swallowing ( not choking)

• Epiglottis
• flap of cartilage
• closes trachea (windpipe) when swallowing
• food travels down esophagus
• Peristalsis
• involuntary muscle contractions to move food
  along

12
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
13
mouth ?break up food ?digest starch ?kill
germs ?moisten food
sphincter
sphincter
14
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
15
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!
16
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
17
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
18
Pancreas accessory organ

• Produces digestive enzymes
• digest proteins
• trypsin, chymotrypsin
• digest starch
• amylase
• digest lipids
• lipase
• Buffers
• neutralizes acid from stomach

smallintestine
pancreas
19
mouth ?break up food ?digest starch ?kill
germs ?moisten food
stomach ?kills germs ?break up food ?digest
proteins ?store food
20
Liver Gall Bladder accessory organs

• Produces bile
• breaks up fats
• gallbladder only stores bile
• thats 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
21
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
22
Large intestines (colon)

• Function
• re-absorbs water
• use 9 liters of water every day in digestive
  juices
• if dont reabsorb water would die of
  dehydration
• gt 90 of water re-absorbed
• not enough water re-absorbed
• diarrhea
• can be fatal!
• too much water re-absorbed
• constipation
• reabsorb by diffusion

23
Youve got company!

• Living in the large intestine is a community of
  helpful bacteria
• Escherichia coli 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!
24
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
25
Rectum

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

So dont forget to wash your hands!
26
Appendix
Vestigial organ
27
Some Digestive 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