1. Human Biology Sylvia S. Mader Michael Windelspecht
Chapter 8 Part 1
Digestive System and Nutrition
Lecture Outline
See separate FlexArt PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes.
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2. Points to Ponder
What are the digestive system structures and their functions?
Where does carbohydrate, protein, and fat digestion and absorption occur?
What are proteins, lipids, carbohydrates, minerals and vitamins needed for?
What is an essential vs. a nonessential nutrient?
What are the 3 accessory organs of digestion?
What is obesity and why is it a problem?
What is LDL and HDL?
What are the components of a healthy diet?
Name and explain 4 eating disorders.

3. What are the main steps in the digestive process?
8.1 Overview of digestion
What are the main steps in the digestive process?
Ingestion: intake of food by the mouth.
Digestion: mechanically or chemically breaking down food into their subunits
Movement: food must be moved along the GI tract in order to fulfill all functions.
Absorption: movement of nutrients across the GI tract wall to be delivered to cell via the blood.
Elimination: removal of indigestible molecules.

4. What are the 4 major layers that make up the wall of the GI tract?
8.1 Overview of digestion
What are the 4 major layers that make up the wall of the GI tract?
Mucosa: innermost layer that produces mucus that protects the lining and also produces digestive enzymes.
Sub mucosa: 2nd layer of loose connective tissue that contains blood vessels, lymphatic vessels, and nerves.
Muscularis: 3rd layer made of 2 layers of smooth muscle that move food along the GI tract.
Serosa: outer lining that is part of the peritoneum.

5. Visualizing the layers of the GI tract
8.1 Overview of digestion
Visualizing the layers of the GI tract
nerve
supply
lymph
vessel
Mucosa
inner mucous membrane
layer modified according
to the digestive organ
Submucosa
broad band of loose
connective tissue that
contains nerves, blood,
and lymphatic vessels
Lumen
central space containing
food being digested
Serosa
thin, outermost tissue
that is the visceral
peritoneum
artery
vein
Muscularis
two layers of
smooth muscle

6. An overview of the digestive system
8.1 Overview of digestion
An overview of the digestive system
Accessory organs
Digestive tract organs
Salivary gland
secrete saliva: contains digestive enzyme
for carbohydrates
Mouth
teeth chew food; tongue tastes and
pushes food for chewing and swallowing
Pharynx
passageway where food is swallowed
Esophagus
passageway where peristalsis pushes
food to stomach
Liver
major metabolic organ:
processes and stores nutrients;
produces bile for emulsification of fats
Stomach
secretes acid and digestive enzyme
for protein; churns, mixing food with
secretions, and sends chyme to
small intestine
Gallbladder
stores bile from liver; sends it to
the small intestine
Small intestine
mixes chyme with digestive enzymes
for final breakdown; absorbs nutrient
molecules into body; secretes
digestive hormones into blood
Pancreas
produces pancreatic juice: contains digestive
enzymes, and sends it to the small intestine;
produces insulin and secretes it into the
blood after eating
Large intestine
absorbs water and salt to form feces
Rectum
stores and regulates elimination
of feces
Anus

7. What is the pathway that food follows?
8.1 Overview of digestion
What is the pathway that food follows?
Mouth
Pharynx
Esophagus
Stomach
Small intestine
Large intestine
Rectum
Anus

8. 8.2 First part of the digestive tract
The mouth
3 pairs of salivary glands secrete salivary amylase that begins carbohydrate digestion.
Tonsils at the back of the mouth and other lymphatic tissues are important in fighting disease.
Contains teeth that begin the mechanical breakdown of food.
The tongue is covered in taste buds and also assists in the mechanical breakdown and movement of food.
The tongue forms a bolus(mass of chewed food) and moves it toward the pharynx.

9. Anatomy of the mouth 8.2 First part of the digestive tract hard palate
soft palate
uvula
tonsil
molars (3)
premolars (2)
canine (1)
incisors (2)

10. Teeth 32 in adults used for mechanical breakdown of food
8.2 First part of the digestive tract
Teeth
32 in adults used for mechanical breakdown of food
(20 deciduous teeth in babies).
Each tooth is made of a crown and a root.
A hard covering called enamel and dentin covers the crown with an inner pulp area with nerves and blood vessels.
Dental caries (cavities) occur when bacteria metabolize sugars and produce acids, so limiting sugar intake and brushing teeth reduces these.

11. Anatomy of a tooth 8.2 First part of the digestive tract enamel crown
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enamel
crown
dentin
pulp
gum
jawbone
root canal
root
periodontal
membrane
cementum

12. The pharynx and esophagus
8.2 First part of the digestive tract
The pharynx and esophagus
Pharynx: is a cavity between the mouth and esophagus that serves as a passageway for food (and air).
Esophagus: is a long, muscular tube that carries food to the stomach.

13. How do we swallow food? Voluntary phase: Involuntary phase:
8.2 First part of the digestive tract
How do we swallow food?
Voluntary phase:
The beginning of food being swallowed from the mouth into the pharynx.
Involuntary phase:
Once the food is in the pharynx swallowing becomes a reflex action perform automatically.
The epiglottis covers the voice box to make sure food is routed into the esophagus.
Food moves down the esophagus through peristalsis (rhythmic contraction).

14. How do we swallow food? 8.2 First part of the digestive tract
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hard palate
food bolus
Soft palate closes
off nasopharynx.
nasopharynx
peristaltic
wave
soft
palate
bolus
epiglottis
Esophagus
is closed.
glottis
Larynx rises and
epiglottis covers
glottis.
Lower gastroesophageal
spincter relaxes and
food enters stomach.
trachea
(airway)
open
esophagus
stomach
esophagus
opens
a. Swallowing
b. Peristalsis

15. Health focus: Heartburn
8.2 First part of the digestive tract
Health focus: Heartburn
Occurs when acids from the stomach pass into the esophagus (acid reflux).
Burning sensation in the esophagus.
Chronic heartburn is called gastro esophageal reflux disease (GERD).
Tips for decreasing heartburn:
Avoid high fat meals.
Don’t overeat.
Eat several small meals rather than the standard 3 larger meals each day.
Exercise lightly.

16. The stomach
The stomach is an enlarged part of alimentary canal and receives food from esophagus.
The stomach like J shape with a thick wall.
Mucous membrane lining stomach contains folds called rugae.
Folds disappear as stomach fills with food.

17. Structure of The Stomach
Its structure is divided into 4 main region:
Funds: bulge
Body : largest region
Antrum:
Pylorus : pyloric sphincters
It has two sphincters:
Cardiac sphincter.
Pyloric sphincter.

18. Function of stomach store food, start digestion of proteins
controls movement of chyme into the small intestine.
Mixing of the food in the stomach produces Chyme.
Mixing movement mainly occurs in the Antrum.
Controlled emptying of gastric content into duodenum.
HCl Secretion gives the stomach a pH of 2 which activates pepsin and helps kill bacteria found in food.

19. c: © Dr. Fred Hossler/Visuals Unlimited
8.3 The stomach and small intestine
Anatomy of the stomach
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esophagus
lower gastroesophageal
sphincter
pyloric
sphincter
Muscularis layer
has three layers
of muscle.
Mucosa layer
has rugae.
c. Gastric pits in mucosa
gastric pit
SEM 3,260x
lower gastroesophageal
sphincter
a. Stomach
gastric pit
gastric gland
cells that secrete
gastric juice
pyloric
sphincter
b. Gastric glands
d. How the stomach empties
c: © Dr. Fred Hossler/Visuals Unlimited

20. The small intestine Averages 6m (18 ft) in length
8.3 The stomach and small intestine
The small intestine
Averages 6m (18 ft) in length
Enzymes secreted by the pancreas into the small intestine digest carbohydrates, proteins, and fats.
Bile is secreted by the gallbladder into the small intestine to emulsify fats.
Digested food is absorbed through large surface area created by numerous villi (finger-like projections) and microvilli.
Amino acids and sugars enter the capillaries while fatty acids and glycerol enter the lacteals (small lymph vessels).

21. Anatomy of the small intestine
8.3 The stomach and small intestine
Anatomy of the small intestine
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Small intestine
Section of intestinal wall
villus
lumen
lacteal
blood
capillaries
villus
microvilli
goblet
cell
lymph
nodule
venule
lymphatic
vessel
Villi
arteriole
(villi): © Manfred Kage/Peter Arnold/Photolibrary; (microvilli):Reprinted from Medical Cell Biology, Charles Flickinger, copyright 1979, with permission from Elsevier.

22. How are nutrients digested and transported out of the small intestine?
8.3 The stomach and small intestine
How are nutrients digested and transported out of the small intestine?
carbohydrate
protein +
pancreatic amylase
bile salts
fat globules
trypsin
emulsification
droplets
peptides
maltase
cell of
intestinal
villus
peptidase
lipase
glucose
monoglycerides
and free
fatty acids
amino acids
pH = basic
pH = basic
pH = basic
chylomicron
lymphatic
capillary
blood capillary
blood capillary
a. Carbohydrate digestion
c. Fat digestion
b. Protein digestion

23. What are the major digestive enzymes?
8.3 The stomach and small intestine
What are the major digestive enzymes?

24. The three accessory organs
8.4 Three accessory organs and regulation of secretions
The three accessory organs
Pancreas
Liver
Gallbladder
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bile canals
branch of
hepatic
artery
bile
central
vein
common hepatic duct
pancreas
pancreatic duct
pancreatic
juice
branch of
hepatic
portal vein
gallbladder b.
bile duct
common bile duct
duodenum a.

25. The pancreas Fished-shaped spongy organ behind the stomach
8.4 The accessory organs and regulation of secretions
The pancreas
Fished-shaped spongy organ behind the stomach
Functions of the pancreas:
1. Secretes enzymes into the small intestine
Trypsin: digests proteins.
Lipase: digests fats.
Pancreatic amylase: digests carbohydrates.
2. Secretes bicarbonate into the small intestine to neutralize stomach acids
3. Secretes insulin into the blood to keep blood sugar levels under control

26. The liver and gallbladder
8.4 The accessory organs and regulation of secretions
The liver and gallbladder
Large metabolic organ that lies under the diaphragm and is made of 100,000 lobules.
Function:
Filters blood from the GI tract thus acting to remove poisons and detoxify the blood.
Removes iron, vitamins A, D, E, K and B12 from the blood and stores them.
Stores glucose as glycogen and breaks it down to help retain blood glucose levels.
Makes plasma proteins and helps regulate cholesterol levels by making bile salts.
Makes bile that is then stored in the gallbladder to be secreted into the small intestine to emulsify fats.
Breaks down hemoglobin.

27. Liver disorders Hepatitis: Inflammation of the liver
8.4 The accessory organs and regulation of secretions
Liver disorders
Hepatitis:
Inflammation of the liver
Caused by Hepatitis A, B, and C
This can lead to liver damage, cancer and/or death
Cirrhosis:
The liver becomes fatty and eventually this tissue is replaced by fibrous scar tissue.
Seen in alcoholics and obese people.
This can lead to liver failure in which the liver cannot regenerate as fast as it is being damaged.

28. How do hormones control digestive gland secretions?
8.4 The accessory organs and regulation of secretions
How do hormones control digestive gland secretions?
gallbladder
liver
stomach
pancreas
secretin
duodenum
CCK
gastrin
blood vessel

29. The large intestine Includes the cecum, colon, rectum and anal canal
8.5 The large intestine and defecation
The large intestine
Includes the cecum, colon, rectum and anal canal
Larger in diameter but shorter than the small intestine
The cecum has a projection known as the appendix that may play a role in fighting infections
Functions to:
Absorb water to prevent dehydration.
Absorbs vitamins (B complex and K) produced by intestinal flora.
Forms and rids the body of feces through the anus.
transverse colon
ascending
colon
small
intestine
descending
colon
cecum
orifice of
appendix
vermiform
appendix
rectum
sigmoid colon
internal anal sphincter
external anal sphincter
anal canal
anus

30. Disorders of the colon and rectum
8.5 The large intestine and defecation
Disorders of the colon and rectum
Diarrhea: increased peristalsis and water is not reabsorbed due to either an infection or nervous stimulation.
Constipation: condition when feces are dry and hard that may be controlled with water and fiber.
Hemorrhoids: enlarged and inflamed blood vessels of the anus due to chronic constipation, pregnancy, aging, and anal intercourse.

31. 8.6 Nutrition and weight control
To understand weight and nutrition we first have to understand nutrients
Nutrients are a component of food that is needed to perform a physiological body function.
Nutrients include:
Carbohydrates
Proteins
Lipids
Minerals
Vitamins

32. Any question? ??????????