CH 3: The Human
Body; A Nutrition
Perspective
Chapter Overview
 This
chapter covers everything from cell
structure to all of the systems of the body!

This is the content of BIO 100 in one chapter!
 We
will focus on the digestive system and
systems that directly relate to the function
of this system..
Sections Covered

While we may touch on content in other
sections, we will focus on:
 Cardiovascular & lymphatic system (3.4)
 Endocrine system (3.6)
 Digestive system (3.8)
Cardiovascular & Lymphatic
Systems
 CV
and lymphatic system circulate fluids in
the body
 CV system

Heart and blood vessels
 Lympahtic

system
Lympahtic vessels and lymph nodes
Blood
 Blood

is made of:
Plasma – fluid portion of blood

Water soluble nutrients are dissolved in the
plasma

Red blood cells
 White blood cells
 Platelets
 Proteins and other substances

Fat soluble nutrients are often carried by water
soluble proteins
CV System –
 Heart




more detail than we have time for
 -> Lungs
Veins bring deoxygenated blood to the right
side of the heart
Right side of the heart pumps deoxygenated
blood to the lungs
Blood returns to the left side of the heart
oxygenated
Left side of heart pumps blood to entire body
by way of arteries
•
Blood Vessels
 Blood
leaves heart through an artery
(aorta)

Vessels branch in to smaller and smaller vessels


Smallest blood vessel is the capillary
Exchanges of gases, nutrients and wastes between
body cells and the CV system occur at the capillary
level
CV System & Digestive Tract
 CV
system transports nutrients to the cells
of the body
 Water soluble nutrients are absorbed in to
capillaries in the small intestine (SI)
 Capillaries merge to form the portal vein
 Portal vein transports nutrients to the liver

#7 on page 90
Lymphatic System
 Lymph


vessels transports:
white blood cells
excess fluid between cells
• Returns the fluid to the blood

fat soluble nutrients absorbed from the SI
 Lymph

vessels branch to form lacteals
Fat soluble nutrients are absorbed in to
lacteals – page 91
Lymphatic System
 Lymph
vessels leaving the SI merge with
veins near the heart

Fat soluble nutrients in the lymph enter the
blood, go through the heart and lungs and are
then circulated in the blood
Endocrine System
 Endocrine
glands secrete hormones
 Hormones enter the blood and bind to
target cells

Cells with receptors for the hormone
 Binding
triggers a change in the target
cells/organ

See table 3-2 on page 93
Endocrine System
Digestive System (finally)

Functions: Digestion, Absorption,
Elimination

Digestion – process of breaking down
foods to release nutrients
•

Goal is to break nutrients into absorbable units
2 types of digestions:
1. Mechanical
2. Chemical (enzymatic)
Overview Digestive System
– movement of nutrients out
of GI tract into blood or lymph
 Absorption


Water soluble nutrients 
Fat soluble nutrients 
– elimination of undigested
foods (feces)
 Excretion
Overview Digestive System
 Structure

Gastrointestinal (GI) Tract
Continuous tube from mouth to anus
• See board and page 97
GI Tract
Anatomy
Digestive Tract
 Layers

of GI tract organs
Serosa (outermost)
• Interface between GI tract and lymph & blood

Muscle Layers
• Longitudinal muscles
• Circular muscles

Submucosal and Mucosal and layers
(innermost)
• Nerves, blood and lymph vessels
• Cells of the mucosal layer produce secretions
Mouth
– teeth, tongue, salivary glands
 Secretions
 Structure



Saliva
Mucus
Salivary amylase
 Digestion


Mechanical ….
Enzymatic/chemical ….
 tongue pushes food 
pharynx  ……
 Swallow
Esophagus

Structure – 12” tube


UES and LES
Function


Transports food from mouth to stomach
Peristalsis and gravity aid food movement

Secretions -- mucus
 Digestion


Mechanical (limited)
Enzymatic/chemical – starch digestion continues
Stomach
 Structure
….page 101
 Secretions …..
 Digestion ……


Mechanical
Enzymatic/chemical
Stomach

Structure –
muscular sack
that can expand
 extra muscle
layer to aid in
the mechanical
digestion of
food (pg 101)
Stomach Related Secretions
1.
2.
3.
Gastrin – hormone that stimulates
stomach to release secretions
Hydrochloric Acid (HCl) -- unravels
proteins, kills bacteria, activates
pepsinogen
Pepsinogen – once activated, begins
protein digestion
Stomach Related Secretions
Mucus – secreted by goblet cells,
protects stomach, moistens food
4.
Intrinsic factor (IF) – IF binds vitamin
B-12
5.
•
Required for B-12 to be absorbed
Stomach related Function
secretions
Gastrin
HCl
Pepsinogen
Mucus
Intrinsic Factor
Stomach - Digestion

Mechanical
• Stomach muscles grind food into a paste called
chyme

Enzymatic/chemical
• Proteins uncoiled
• Protein digestion to polypeptides begins
• Starch digestion stops (why??)
Small Intestine (SI)
 Function
1.
– The SI is where:
the majority of digestion to absorbable units
occurs
• Digestion of carbohydrates, fats, and proteins
• Vitamins and minerals do not need digestion
2.
Nutrients are absorbed into either capillaries
or lacteals
Small Intestine

Structure – see page 102

Length – 10 feet (~ 21’-22’ long when relaxed)
 Layers …..
 Mucosal folds, villi, microvilli ….
 Goblet cells and crypts – create secretions
 Lacteals and capillaries ….

Sections
• Duodenum
• Jejunum
• Ileum
Small Intestine
The Small Intestinal Villi
The Small Intestinal Villi
Small Intestines
 Secretions
1.
of the SI
Mucus
• Secreted by ____________ cells
2.
Digestive enzymes that finish the digestion
of carbs, fats, and proteins
• Secreted from crypts
Small Intestine
 Secretions

of the SI, cont’d
Hormones
• Secretin …
• CCK ….
• Gastric-inhibitory peptide …
Small Intestine - Hormones

Secretin – produced when chyme enters SI
• stimulates pancreatic secretions

*CCK – produced when fat enters SI
• Stimulates _________to release ______
• Slows GI motility (slows peristalsis)
• *Cholecystokinin

Gastric–inhibitory peptide – produced
when chyme enters SI
• Slows stomach secretions
• Slows GI motility
Secretions of SI
Mucus
Digestive Enzymes
Secretin
CCK
Gastric inhibitory
peptide
When Secreted and
Function
Secretions into SI
 Pancreatic


secretions:
Released in response to ________
Sodium bicarbonate
• Neutralizes acidic chyme

Digestive enzymes that begin the digestion of
carbs, fats, and proteins
Secretions into SI
 Liver



and Gall Bladder
Liver makes bile
Gall bladder concentrates and stores bile
Bile is released into SI in response to the
hormone _______
 Function
of bile:
Secretions into SI
Sodium bicarbonate
Digestive Enzymes
Bile
Secreted by and
Function
Small Intestine
 Digestion


- Mechanical
Peristalsis pushes food through SI
Segmentation mixes chyme with digestive
enzymes
• Also breaks up food mass into smaller masses

Bile emulsifies fats
Peristalsis & Segmentation
Muscular Action
of Digestion
Segmentation
SI - Digestion
 Mechanical


digestion
Muscle action breaks food into smaller and
smaller pieces
Bile emulsifies fats
 Chemical/Enzymatic

Pancreatic and SI enzymes digest carbs, fats,
and proteins to absorbable units
SI - Absorption
 Absorbed


into capillaries (blood)
Digested carbohydrates and proteins
Minerals
• Some require helper proteins/cells on walls of SI to
be absorbed
Water soluble vitamins
 Blood takes nutrients to the liver for processing
after absorption (pg 90)

SI - Absorption
 Absorbed
into lacteals (lymph)
Digested fats
 Fat soluble vitamins
 Cholesterol
 Nutrients travel through lymph system to chest
area where lymph and blood join
 Nutrients enter blood and travel through body

SI Review
What is the
relationship
between the
structure of the
SI and its
function?
Large Intestine or Colon
 Undigested
foods (fiber) enter into colon
 Unabsorbed nutrients pass into colon

E.g. calcium, iron, cholesterol trapped in fiber
Colon
 Structure

Ileocecal sphincter connects colon to SI
• Appendix is a little pouch near beginning of colon


Colon is ~5-6’ long, “wraps around” SI
Wider diameter than SI
• No villi or microvilli
• No digestive enzymes

Pages 104/105
Colon
 Secretions


Mucus
Bacteria living in colon
• Digest small amounts of fiber and undigested
nutrients
• Often produce…...
Colon
 Absorption

Water, salts, vitamins made by bacteria are
absorbed into __________ (answer is either
capillaries or lacteals. Which one is it?..you
know!)
 Fiber


attracts water
Too little fiber in diet 
Too much fiber in diet 
Rectum and Anus
 Feces
pass from colon into rectum
 Rectum stores feces until excretion occurs
 Feces exit body via anus

2 anal sphincters
• Internal and external anal sphincters