biology 111gervind.faculty.mjc.edu/biology_111/111_lectures/topic 8b ch11b.pdf · chyme to enter...

BIOLOGY 111

CHAPTER 11: Human Body Systems

11.4–11.6 Digestive System

The human digestive system consists of an alimentary canal and

accessory organs:Alimentary canal

11.4) The human digestive system consists of an alimentary canal and accessory

organs.

CORE IDEA: The human digestive system consists of an alimentary canal (divided into organs along

its length) and various accessory organs, including salivary glands and organs that release digestive

juices into the small intestine.

A. Alimentary canal

B. Accessory organs

C. Nutrient absorption in the small intestine

D. Peristalsis

A. Alimentary canal

1. The digestive system consists of an alimentary

canal that is divided along its length into specialized

digestive organs.

• It is a tube-like system that spans from the mouth to the

anus



➢ Mouth

➢ Pharynx

➢ Esophagus

➢ Stomach

➢ Small intestine

➢ Anus

2. Mouth

a. Also called the oral cavity

b. Site of ingestion (eating)

➢ Start of mechanical digestion (cutting, grinding, and mashing)

➢ Start of chemical digestion (via saliva)





3. Pharynx

a. The pharynx is the intersection of the

mouth, esophagus, and trachea (which

leads to the lungs).

3. Pharynx

a. The pharynx is the intersection of the

mouth, esophagus, and trachea (which

leads to the lungs).

b. The epiglottis closes over the trachea so

food and liquid go into the esophagus.

“Going down the wrong pipe” refers to food or

liquid entering the trachea.





4. Esophagus

a. The esophagus is a muscular tube connecting the

pharynx to the stomach.

b. Food moves via muscular contractions called

peristalsis.

5. Stomach

a. Your stomach has elastic folds that can stretch to hold large amounts of

food and liquid.



b. Cells in the stomach secrete

gastric juice.

i. Gastric juice contains enzymes

(such as pepsin) to digest proteins

ii. Gastric juice is very acidic (pH=2).

• The walls of the stomach mix the

food and gastric juice to produce

chyme.

(mechanical and chemical digestion)

5. Stomach



d. A sphincter (ring of muscles)

opens to allow small amounts of

chyme to enter the small

intestine.

6. Small intestine

a. Chemical digestion is completed by enzymes.



6. Small intestine

a. Chemical digestion is completed by enzymes.



b. The organ is narrow but long.

c. This is the primary site of nutrient

absorption.

6. Small intestine

• The Small Intestines have 3 sections:



i. Duodenum

ii. Jejunum

iii. Ileum

6. Small intestine




i. Duodenum:

• This is where digestion is completed

• Secretions from gall bladder and

pancreas finish off digestion

6. Small intestine




ii. Jejunum:

• This is where 90% of nutrients are

absorbed

6. Small intestine




i. Ileum:

• This is where the absorption of

nutrients is completed

• Anything not absorbed by the

jejunum should be absorbed here

7. Large intestine

a. It is larger in diameter but shorter in length.



7. Large intestine

a. It is larger in diameter but shorter in length.



b. Water is absorbed and returned

to the bloodstream.

c. What remains of food is formed

into feces and stored in the

rectum.

d. Large numbers of healthy

bacteria inhabit the large

intestine.

8. Anus

a. Two sphincters—one voluntary, one not—regulate opening the anus.



8. Anus




b. The rectum is the final section of

the colon (feces are stored here)

8. Anus




b. The rectum is the final section of

the colon (feces are stored here)

c. The anus is the opening where

the gastrointestinal tract ends and

exits the body

B. Accessory organs

1. Salivary glands

2. Liver

3. Gallbladder

4. Pancreas



B. Accessory organs

1. Accessory organs secrete specific digestive chemicals into the alimentary

canal via ducts.



2. Salivary glands

a. They secrete saliva into the

mouth.

b. Saliva contains the enzyme

salivary amylase, which breaks

down starch.



3. Liver

a. This secretes bile.

b. Bile helps in the process of fat

digestion.



4. Gallbladder

a. This stores bile produced by the liver. (aids in digestion of lipids)

b. It secretes bile via duct into the

small intestine.

4. Gallbladder

a. This stores bile produced by the liver.



b. It secretes bile via duct into the

small intestine.

5. Pancreas

a. Secretions help neutralize

stomach acid.

b. It continues the chemical

digestion of food.

c. It secretes fluid via duct to the

small intestine.


1. Epithelial tissue lining the small intestine is extensively folded.




1. Epithelial tissue lining the small intestine is extensively folded.

2. Tiny finger-like projections inside are called villi.



3. Each cell has microvilli.

4. Together these features produce a surface

area for absorption.

D. Peristalsis

1. It propels food through the gut



2. There are waves of muscle

contractions.

3. It holds food in place and moves it

forward.

a. Not based on gravity

Food is processed in a series of stages:The processing of food

11.5) Food is processed in a series of stages.

CORE IDEA: Food processing occurs via four stages: ingestion (also called eating), digestion (which

can be mechanical or chemical), absorption (primarily by cells lining the small intestine), and

elimination of undigested wastes.

A. The processing of food

B. Four-stage process


1. To be used by your body, food must be broken down.

a. Your body and your food consist of similar molecules.

b. Breaking down proteins generates amino acids to build new proteins

2. Large pieces of food must be broken down into small molecular building

blocks.



1. To be used by your body, food must be broken down.

a. Your body and your food consist of similar molecules.

b. Breaking down proteins generates amino acids to build new proteins

2. Large pieces of food must be broken down into small molecular building

blocks.


3. These small molecules are

absorbed and used by the body.

4. Unneeded or unabsorbed

substances are passed out as

waste.

B. Four-stage process

1. Ingestion

a. It is also called

eating.

b. It is the first stage

of food processing.

c. All animals ingest

other organisms,

whole or by the

piece.


2. Digestion

a. This is the breakdown of food into molecules small enough to be absorbed

by the body.


i. Proteins must be broken down

into amino acids to be absorbed.

2. Digestion


by the body.




b. There are two kinds of digestion:

i. Mechanical digestion—use of physical

processes to mix, mash, and tear

2. Digestion


by the body.




b. There are two kinds of digestion:

i. Mechanical digestion—use of physical

processes to mix, mash, and tear

ii. Chemical digestion—use of enzymes to

perform hydrolysis

3. Absorption

a. This is the uptake of small nutrient molecules.

b. It occurs primarily in the jejunum of the small intestine.

c. Nutrients enter blood vessels to be transported to all of the body’s cells.

d. Villi increase the surface area for absorption in the small intestine.


3. Absorption

• It is in the villi that “outside meets the inside”

• Capillaries allow digested molecules to enter the bloodstream


4. Elimination

a. This is the disposal of undigested matter from the body.

b. Food waste accumulates as feces.

c. It is eliminated via the anus.


Proper nutrition provides energy and building materials:Eating right

11.6) Proper nutrition provides energy and building materials.

CORE IDEA: A proper diet provides raw materials and energy to cells. Essential nutrients cannot be

produced by the body and so must be eaten. They include minerals, organic vitamins, essential fatty

acids, and essential amino acids.

A. Eating right

B. Essential nutrients

A. Eating right

1. Eating a well-balanced diet helps your body in two ways:

a. It provides the building materials needed for the body’s structures.

b. It provides the energy needed to maintain the body’s functions.


2. The United States Department of Agriculture (USDA) released updated

dietary guidelines called MyPlate in 2011.

a. Recommended amounts of five food groups

i. Fruits, grains, vegetables, protein, and dairy


B. Essential nutrients

1. These are materials the body cannot make itself.

2. The absence of any essential nutrient causes disease.


3. Example

a. Your cells can manufacture 11

different kinds of amino acids.

b. Another nine cannot be made

and must be ingested to avoid

malnutrition.

4. Four classes of essential nutrients

a. Minerals—inorganic chemical elements

i. Some are required in large amounts—calcium.


ii. Some are required in small

amounts—iron.

iii. Too little iron can result in

anemia.

b. Vitamins—organic compounds

i. These are organic nutrients.

ii. Required only in very small amounts


• Lack of any vitamin leads to

disease.

• Some are water soluble

(C and B-complex).

• Some are fat soluble

(A, D, E, and K).

• Lack of vitamin C causes scurvy.

c. Essential fatty acids—required to build several important molecules

i. Required to make fats and other lipids

ii. Many fish are rich in linoleic acid, an omega-6 fatty acid used to make

cell membranes.


d. Essential amino acids—required to build proteins

• Nine amino acids cannot be made and must come from the diet.

• Different foods contain different amino acids.


• Many animal proteins contain all

the essential amino acids.

• Most plant proteins contain a

subset.

• A combination of plant proteins

(grain plus a legume) can provide

all the essential amino acids.

An unbalanced diet or malfunctioning digestive system can lead to

health problems:What can go wrong

11.7) An unbalanced diet or malfunctioning digestive system can lead to health

problems.

CORE IDEA: Health problems can result from a number of abnormalities in the human digestive

system. Additionally, improper diet—resulting in obesity, malnutrition, or eating disorders—can cause

significant health problems.

A. What can go wrong:

B. Gastric bypass

C. Nutritional imbalances:

A. What can go wrong:

1. Acid reflux

• It is also called heartburn.

• It is a backflow of partially digested food from the stomach back into the

esophagus.

• It is also known as gastroesophageal reflux disease (GERD).

• It is treated by lifestyle changes and antacids.



2. Gallstones

a. These are solid crystals of bile.

b. They can obstruct the gallbladder or its ducts.

c. Often, the cure is surgery to remove the gallbladder.



3. Constipation

a. If peristalsis slows down too much, too much water is removed and the

feces becomes compacted.

b. Most commonly this results from lack of exercise and a fiber-poor diet.



4. Appendicitis

a. It is an infection of the appendix by bacteria.

b. The appendix is a small extension of the large intestine.

c. Most people are cured by surgical removal of appendix.



5. Cholera

a. It is an infection by bacterium Vibrio cholerae.

b. It occurs most often from improper sanitation.

c. Bacterium releases toxin that produces diarrhea so severe it can lead to

death.



6. Inflammatory bowel disease

a. It is known also as Crohn’s disease and ulcerative colitis.

b. It is caused by painful swelling (inflammation) of the intestinal wall.



7. Ulcer

a. A coating of mucus prevents gastric juice from harming the stomach lining.

b. Infection by Helicobacter pylori damages mucus lining.

c. Erosion of the stomach lining is a gastric ulcer.

d. Most often it is treated with medication containing bismuth and antibiotics.



biology 111gervind.faculty.mjc.edu/biology_111/111_lectures/topic 8b ch11b.pdf · chyme to enter...

Documents