Chapter 3
Anatomy for
Nutrition’s Sake
 2010 Cengage-Wadsworth
Introduction to the
Human Body
• The body is
composed of
millions of cells.
• Each cell is a selfcontained living
entity.
• The body cells
need:
 Energy (or fuel)
 Oxygen
 Water
 Nutrients
• Cells: the
smallest units in
which
independent life
can exist. All
living things are
single cells or
organisms made
of cells.
 2010 Cengage-Wadsworth
Introduction to the
Human Body
A typical cell
 2010 Cengage-Wadsworth
A membrane encloses
each cell’s contents.
A separate inner membrane
encloses the cell’s nucleus.
These fingerlike projections are
typical of cells that absorb
nutrients in the intestines.
Inside the nucleus, the
Genetic material, DNA,
contains the genes. The
genes control the
inheritance of the cell’s
characteristics and its dayto-day workings. The DNA is
faithfully copied each
time the cell duplicates
itself.
On these membranes,
instructions from the
genes are translated
into proteins that
perform
functions in the body.
Many other structures
are present. This is a
mitochondrion, a structure
that takes in nutrients and
releases energy from them.
Fig. 3-1, p. 76
Introduction to the
Human Body
• Cells are organized into tissues
designed to perform specialized tasks.
Some of these tasks include the
formation of muscles and organs.
• Several organs work cooperatively to
form a body system.
 The digestive system consists of organs and
tissues working together to supply energy,
water, and essential nutrients to every body
cell.
 2010 Cengage-Wadsworth
Digestive System
• Hypothalamus:
The hypothalamus monitors the
body’s conditions & sends signals to
the brain’s thinking portion, the
cortex, which decides on actions.
Detects fuel
deprivation
Generates
nerve impulses
that signal
hunger to the
conscious part
of the brain
 2010 Cengage-Wadsworth
Cortex
Hypothalamus
Spinal cord
Fig. 3-2, p. 77
Digestive System
• The gastrointestinal (GI) tract supplies
the body with a constant supply of
water and nutrients by controlling:
 Passage of food through GI tract
 Secretion of digestive juices and enzymes
 Digestion of food
 Absorption of water and nutrients
 Circulating blood through digestive system
to distribute absorbed substances
 2010 Cengage-Wadsworth
Digestive
System
•Each part of the
digestive tract has
specific functions
such as:
Basic passage of food
Temporary storage
unit
Digest food
Absorb food
The digestive system
 2010 Cengage-Wadsworth
 2010 Cengage-Wadsworth
Salivary
glands
Esophagus
Stomach
Liver
Mouth
Tongue
Airway to lungs
Gallbladder
Pancreas
Pancreatic
duct
Pyloric
sphincter
Bile duct
Colon
(large
intestine)
Small
intestine
Appendix
Rectum
Anus
Fig. 3-3a, p. 78
 2010 Cengage-Wadsworth
The Mouth
• Digestive process begins in the mouth
through mechanical digestion
(physically breaking down foods).
 Breaks down indigestible membranes and
uncovers nutrient-rich portion of foods.
 Exposes surface area of food to digestive
enzymes.
 Contains salivary glands which secrete
digestive enzymes and help to moisten food
and make it easier to swallow.
 2010 Cengage-Wadsworth
Oropharyngeal stage of swallowing
 2010 Cengage-Wadsworth
Nasal
passages
Hard palate
Soft palate
Uvula
Pharynx
Epiglottis
Esophagus
Bolus
Trachea
Tongue
Glottis at entrance of larynx
Fig. 3-6a, p. 81
Swallowing center
inhibits respiratory
center in brain stem
Elevation of uvula
prevents food from
entering nasal passages
Position of tongue
prevents food from
re-entering mouth
Epiglottis is pressed
down over closed
glottis as auxiliary
mechanism to prevent
food from entering
airways
Tight apposition of vocal folds across
glottis prevents food from entering
respiratory airways (viewed from above)
Fig. 3-6b, p. 81
The Mouth
• When food is chewed the mixture of food
particles and saliva is called a bolus.
• The bolus moves from the mouth to the
esophagus through swallowing.
 The first part of swallowing which moves food
toward the pharynx is voluntary.
 After food reaches the pharynx, swallowing is
considered to be involuntary and cannot be
stopped.
 The trachea (windpipe) closes and the
pharynx propels the bolus toward the
esophagus.
 2010 Cengage-Wadsworth
The Esophagus
• No digestion takes place in the esophagus.
• Food passes from the mouth to the stomach
and travels through the esophagus.
• Sphincters open and close to allow the bolus
to pass.
 Sphincter: a circular band of muscle fibers that
constrict a passage or close a natural opening in the
body.
• Peristalsis: Longitudinal and circular muscle
layers of the esophagus rhythmically push the
bolus down the esophagus.
 2010 Cengage-Wadsworth
The Stomach
• Three jobs of the stomach:
 Stores food until it can be processed.
 Forms chyme: the semi-liquid blend of food
and gastric secretions that forms in the
stomach during digestion.
 Controls movement of chyme into the small
intestine at a rate suitable for digestion and
absorption by the small intestine.
• An empty stomach holds about 3
tablespoons but can stretch to about
one liter for holding food and drinks.
 2010 Cengage-Wadsworth
The Stomach
•Food passes through the
gastroesophageal
sphincter to enter the
stomach.
•Peristalsis causes the
stomach to churn, mixing
the food with hydrochloric
acid (HCL) and gastric
secretions to form chyme.
•The pyloric sphincter
controls the emptying of
the stomach.
Anatomy of the stomach
 2010 Cengage-Wadsworth
Esophagus
Gastroesophageal
sphincter
Pyloric
sphincter
Smooth
muscle
Stomach
folds
Duodenum
Fig. 3-7, p. 83
The Stomach
Mixing of stomach contents and emptying of the stomach
 2010 Cengage-Wadsworth
Stomach
Esophagus
1
Gastroesophageal
sphincter
Pyloric sphincter
Duodenum
4
3
2
Movement
of chyme
Peristaltic
contraction
Gastric emptying
Direction of
movement
of peristaltic
contraction
6
5
Peristaltic
contraction
Gastric mixing
Fig. 3-8, p. 84
The Stomach
• The stomach empties in about four
hours.
Liquids pass the quickest. Solids stay
until mixed with stomach secretions.
Carbohydrate passes more quickly
than protein. Fat takes the longest to
digest.
• The rate of emptying is controlled
by the central nervous system
(CNS) and hormonal mechanisms.
 2010 Cengage-Wadsworth
Digestive Tract Secretions
 2010 Cengage-Wadsworth
The Small Intestine
• The small intestine is about 20 feet
in length.
• It is smaller in diameter than the
large intestine, thus the name
“small” intestine.
• It finishes the job of digestion and
absorption of nutrients.
 2010 Cengage-Wadsworth
The Small Intestine
• Chyme must touch the walls to make
contact with secretions and be absorbed
at the proper places.
• Peristalsis moves chyme through the
small intestine.
 Stimulated by fiber
 Slowed by fat
• The ileocecal valve controls the flow of
contents going into the large intestine.
 2010 Cengage-Wadsworth
The Small Intestine
• The small intestine works to break
down food and nutrients to their
smallest absorbable components.
• This breakdown is complex, requiring
many chemical reactions:
 Hormonal messages tell the gallbladder to
send its emulsifier, bile.
 Hormones send messages to the pancreas
to release the neutralizer, bicarbonate.
 Pancreatic and intestinal enzymes act to
break bonds of larger nutrients.
 2010 Cengage-Wadsworth
The Small Intestine
Bile: a compound made from
cholesterol by the liver, stored in the
gallbladder, and secreted into the
small intestine. It emulsifies lipids to
ready them for enzymatic digestion.
Emulsifier: a compound with both
water-soluble and fat-soluble portions
that can attract lipids into water to
form an emulsion.
 2010 Cengage-Wadsworth
The Small Intestine
• After breakdown, these nutrient
components are able to cross
through the absorptive cells lining
the small intestine and enter the
blood and lymph supply.
• These cells are selective and
efficient as they absorb enough
nutrients to nourish all the body’s
other cells.
 2010 Cengage-Wadsworth
The Small Intestine
• The intestinal tract lining contains
an enormous absorbing surface.
Villi: fingerlike projections of the
sheet of cells that line the GI tract;
the villi make the surface area much
greater than it would otherwise be.
Microvilli: tiny hairlike projections
on each cell of the intestinal tract
lining that can trap nutrient particles
and translocate them into the cells.
 2010 Cengage-Wadsworth
Details of the lining of the small intestine
 2010 Cengage-Wadsworth
Stomach
Small
intestine
Folds with villi
on them
A villus
Capillaries
The wall of the
small intestine
Is wrinkled into
thousands of
folds and is
carpeted with
villi.
This photograph
shows part
of a human
intestinal cell
with microvilli.
Lymphatic
vessel
Muscle layers
beneath folds
Between the villi
tubular glands secrete
enzyme-containing
intestinal juice.
Artery
Vein
Lymphatic vessel
Microvilli
Three cells of a villus.
Each cell is covered
with microvilli.
Fig. 3-9, p. 87
The Small Intestine
• Simple sugars and water-soluble vitamins
are absorbed high in the small intestine
because they require no special handling.
• Nutrients released more slowly are
absorbed further down.
• When the mixture reaches the large
intestine, water, fiber, and dissolved
minerals are all that is left.
• The lymphatic system and circulatory
systems take over the job of transporting
nutrients.
 2010 Cengage-Wadsworth
The Large
Intestine
• The large intestine is
about 1.5 meters
long and is larger in
diameter than the
small intestine.
• No digestive enzymes
are secreted because
chemical digestion is
complete.
Anatomy of the large intestine
 2010 Cengage-Wadsworth
Transverse colon
Descending
colon
Ascending
colon
Ileocecal
valve
Cecum
Appendix
Rectum
Internal anal sphincter
(smooth muscle)
Sigmoid
colon
External anal sphincter
(skeletal muscle)
Anal canal
Fig. 3-10, p. 88
The Large Intestine
• Naturally occurring bacteria reside in the
large intestine and are responsible for:
 Digestion of some fiber and leftover
carbohydrate.
 Synthesis of absorbable vitamin K.
• Primary functions of the large intestine:
Absorb dissolved minerals and water.
Eliminate waste products.
 2010 Cengage-Wadsworth
The Large Intestine
• Final waste products are mixed with
mucus to form fecal matter.
• Fecal material normally consists of:
water, undigested fiber, bilirubin,
bacteria, small amounts of salt.
• Peristalsis is slower and occurs less
frequently.
• When the rectum fills with feces, the
defecation reflex expels the waste
products.
 2010 Cengage-Wadsworth
Accessory Organs
of Digestion
•Organs outside the
digestive tract
contribute digestive
juices through a
common bile duct
into the small
intestine.
•The organs are:
Liver
Gallbladder
Pancreas
Accessory organs of digestion
 2010 Cengage-Wadsworth
Bile duct
from liver
Stomach
Duodenum
Hormones
(insulin,
glucagon)
Blood
Duct cells secrete Acinar cells
aqueous sodium secrete digestive
bicarbonate solutionenzymes
Exocrine portion of pancreas
(Acinar and duct cells)
Endocrine portion
of pancreas
(Islets of Langerhans)
The glandular portions of
the pancreas are grossly
exaggerated.
Fig. 3-11, p. 89
The Liver
• The liver determines the metabolic fate
of every nutrient we digest and absorb.
• The liver performs a wide variety of
functions which are essential for life.
• The liver produces bile which helps to
emulsify fat and improve the efficiency
of fat digestion.
 2010 Cengage-Wadsworth
The Gallbladder
• The gallbladder is a sack attached to
the liver where bile is stored and
concentrated.
• Bile empties from the gallbladder into
the common bile duct.
• When chyme with fatty contents enters
the small intestine, a hormone
stimulates the gallbladder to contract
and empty bile into the small intestine.
 2010 Cengage-Wadsworth
The Pancreas
• The Pancreas has both endocrine
and exocrine functions.
Endocrine: a term to describe a
gland secreting or a hormone being
secreted into the blood.
Exocrine: a secretion that is expelled
through a duct into a body cavity or
onto the surface of the skin.
 2010 Cengage-Wadsworth
The Pancreas
• Endocrine functions include:
Secretion of the hormones insulin and
glucagon which regulate blood
glucose levels.
• Exocrine functions include:
Secretion of digestive enzymes which
act on carbohydrates, proteins, fats
and bicarbonate. These are secreted
into the duodenum.
 2010 Cengage-Wadsworth
Metabolism
Breaking Down Nutrients for
Energy:
• Nutrients are absorbed from the
digestive system into the blood
where they converge from
capillaries, into veins and then into
a single large vein.
• This vein carries nutrients to the
liver where they break up into a
vast capillary network.
 2010 Cengage-Wadsworth
Metabolism
• Liver cells process the nutrients:
Converts carbohydrate into glucose.
Stores excess glucose as glycogen or
fat.
Reassembles fats and packages them
for transport or storage.
Alters amino acids as needed to make
protein or other amino acids.
 2010 Cengage-Wadsworth
Metabolism
• Nutrients leaving the digestive
tract by way of lymph as
chylomicrons circulate through the
body.
Cells can withdraw fats.
Some find their way into the blood
and circulate through to the liver.
 2010 Cengage-Wadsworth
Metabolism
• New products of liver metabolism
are released into the bloodstream
and circulate to other cells of the
body. These products are:
Glucose
Fat packaged with protein
(lipoprotein)
Amino acids
 2010 Cengage-Wadsworth
Metabolism
• Surplus fat can be removed by the cells
and made ready for storage.
 The human body has infinite storage
capacity.
• Liver glycogen provides a reserve
supply of glucose.
 The body can draw from this reserve during
intervals when glucose is not ingested and
absorbed.
 This supply lasts about 3 to 6 hours.
 2010 Cengage-Wadsworth
Metabolism
• The storage systems for glucose and fat
ensure that the cells will not go without
energy nutrients except under extreme
conditions.
• Other storage systems include:
 Protein held in an available pool.
 Liver and fat cells store many vitamins.
 Bones provide reserves of calcium and
sodium.
 2010 Cengage-Wadsworth
Metabolism
• The breaking down of body
compounds is known as catabolism.
• When the body needs energy, it
breaks down any or all of the four
basic units:
Glucose
Fatty acids
Glycerol
Amino acids
 2010 Cengage-Wadsworth
Metabolism
• When the body does not require
energy, end products of digestion
are used to build body compounds
in a process called anabolism.
• Catabolism and anabolism are
examples of energy metabolism.
 2010 Cengage-Wadsworth
Functional Food Pyramid
 2010 Cengage-Wadsworth