Transcript BIOL103 Ch 3 Human Body_for Students

Chapter 3
The Human Body: From Food to
Fuel
BIOL 103
Today’s Topics
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Taste and Smell
GI Tract
Digestion and Absorption
Assisting Organs
Circulation of Nutrients
Signaling Systems: Command, Control, and Defense
– The Hormonal System
– The Immune System
• Influences on Digestion and Absorption
– Psychological, Chemical, Bacterial Influences
• Nutrition and GI Disorders
Taste and Smell: The Beginnings
of our Food Experience
• Sight, smell, thought,
taste, and sound
– Can trigger a set of
responses that prepare
the digestive tract to
receive food
The Gastrointestinal (GI) Tract
• Organization
– Parts (mouth  anus)
• Mouth, esophagus,
stomach, small intestine,
large intestine, rectum
– Accessory organs
1.
2.
3.
4.
Salivary glands
Liver
Gallbladder
Pancreas
Organization of the GI Tract
• Functions:
1. Ingestion (the receipt and softening of food)
2. Transport of ingested food
3. Secretion of digestive enzymes, acid, mucus,
and bile
4. Absorption of end products of digestion
5. Movement of undigested material
6. Elimination of waste material
Organization of the GI Tract
• Structural organization of the GI tract:
– Mucosa (innermost layer)
• Glands and absorptive cells
– Circular muscle and longitudinal muscle
• Mix and move the food
– Sphincter: valve that controls the movement of
food material so that it travels through the GI
tract in only one direction.
Overview of Digestion
• Mouth
– Chewing  break food into smaller pieces
– Saliva  lubricates the food  ___________
• Down the GI tract:
– Physical movement
• _____________________: push food down
• _____________________: move food
forward and backward
Overview of Digestion
Which one is peristalsis? How about
segmentation?
Digestive Enzymes in Chemical Reactions
Overview of Digestion
• Chemical breakdown: (Bolus  _____________)
• Enzymes: proteins that catalyze (speed up)
reactions but are not altered in the process.
– Examples: amylase, lipase, etc.
• Other secretions:
– Stomach Acid
– Base
– Bile
– Mucus
Overview of Absorption
Assisting Organs
1. Salivary glands
– Moisten food
– Supply enzymes
Assisting Organs
2. Liver
– Produces bile
– “Detox center”
– “Chemical factory”:
>500 chemicals as well as
blood proteins, cholesterol,
sugar
– “Dynamic warehouse”:
stores hormones,
cholesterol, minerals, sugar,
etc.
Assisting/Accessory Organs
3. Gallbladder
– Stores and excretes bile
4. Pancreas
– Secretes __________________,
digestive enzymes
– Secretes hormones (_________
and _________________)
Putting it All Together:
Digestion and Absorption
• Mouth
– Enzymes
• _______________
acts on starch
• _______________
_______acts on
fat
– Saliva
• Moistens food for
swallowing 
bolus
Putting it All Together:
Digestion and Absorption
• Esophagus
– Transports food to
stomach
– Esophageal sphincter
or cardiac sphincter
• “Heartburn”
Putting It All Together:
Digestion and Absorption
• Stomach Enzymes:
– Food in stomach triggers gastrin (hormone) stimulates
gastric secretion of HCl and pepsinogen and
movement
– Hydrochloric acid (HCl)/gastric acid
1. kills bacteria
2. prepares protein for digestion
– Pepsinogen (inactive)  Pepsin (active)
– _________: breaks down protein into smaller pieces
– _____________________: some fat digestion
– Intrinsic factor: binds to vitamin B12 to survive the
journey through the acidic stomach
Putting It All Together:
Digestion and Absorption
• Small intestine (~10ft)
– Pyloric Sphincter
– Sections of small
intestine:
• Duodenum
• Jejunum
• Ileum
– Main role: chemical
digestion and absorption
Putting It All Together:
Digestion and Absorption
• Nutrient digestion:
– Acidic chyme in duodenum stimulates release of
two hormones by intestinal mucosa:
1. Secretin:
–Goes to pancreas to release release
bicarbonate
–Goes to stomach to inhibit release of HCl,
pepsinogen, and stomach motility
2. CCK (cholescystokinin):
–Release pancreatic enzymes (e.g. lipase)
–Contract the gallbladder to release bile
–Goes to stomach to reduce motility
Putting It All Together:
Digestion and Absorption
• Small intestine
– Completes absorption:
• Folds, villi, microvilli expand
absorptive surface
• Most nutrients absorbed here
• Fat-soluble nutrients 
lymphatic system (lymphatic
vessel in the intestinal villus
known as lacteals)
• Water-soluble nutrients 
bloodstream.
Putting It All Together:
Digestion and Absorption
• Large Intestine
– Ileocecal valve
– Sections
• Cecum, colon, rectum,
and anal canal
– Digestion
• Peristaltic movement is
slow, taking 18-24 hours
for material to travel
• Some bacterial activity
(e.g. fiber digestion)
Beans, Beans, Beans!
• Beans are made up of oligosaccharides (e.g.
raffinose and stachyose), a component of fiber.
• They are ignored until they are met by 700+
species of bacteria in your large intestine.
– Bacteria digests these sugars  gases
accumulate  flatulence
Putting it All Together:
Digestion and Absorption
• Large Intestine:
– Absorption
• Water
• Na, K, Cl
• Vitamin K (produced by
bacteria)
– Elimination at anal
sphincter
• Feces: 60% solid
(bacteria, dietary fiber,
digestive secretions),
40% water
Circulation of Nutrients
• Vascular system
– Veins and arteries
– Carries oxygen and water-soluble nutrients to
tissues
– Removes wastes
• Lymphatic system
– Vessels that drain lymph
– Carries fat-soluble nutrients
– Empties into the bloodstream near the neck
Circulation of Nutrients
• Excretion and elimination
– Once destination cells have used up the oxygen
and nutrients, carbon dioxide and waste products
are picked up by blood and transported to:
1. Lungs
–Excrete water and carbon dioxide
2. Kidneys filter blood
–Excrete waste; maintain water and ion
balance
Summary of Digestion and
Absorption of Nutrients in
the Human Body
Review!!!
Signaling Systems:
Command, Control, and Defense
• Nervous system
– Regulates GI activity
• Enteric nervous system: nerves located in the
gut wall
–“the brain”
• Autonomic nervous system: part of central
nervous system that controls organ function
–Responses to sight, smell, thought of food
by enhancing GI movement and secretion
–Parasympathetic: “rest and digest”
Signaling Systems:
Hormonal System
• Hormonal system
– Hormones: chemical messengers from tissues that
travel in the bloodstream to target tissue to cause
an effect
1. Increases or decreases GI motility and secretions
1. Influence your appetite by sending messages to
your CNS
• Thus, your CNS and hormones work together to
coordinate movement and secretions of the GI tract.
Influences on Digestion and Absorption
• Psychological influences
– Taste, smell, and
presentation of food
• Chemical influences
– Type of protein you eat and
the way it is prepared
• Bacterial influences
– Hydrochloric acid kills most
bacteria
Nutrition and GI Disorders
• Constipation (< 3x/week)
– Hard, dry, infrequent stools
– Reduced by high fiber, fluid intake, and exercise
• Diarrhea (> 3x/day)
– Loose, watery, frequent stools
– Symptom of diseases/infections  peristalsis
– Can cause dehydration
– Broth, tea, toast, and other low-fiber foods can
help reduce diarrhea
Nutrition and GI Disorders
• Diverticulosis
– Pouches along colon
develop as people age
• 10-25% people 
pouches become infected
– High-fiber diet reduces
formation:
• Low-fiber diet  harder
stools  more pressure
on colon  weak spots
bulge outwards and form
pockets
Nutrition and GI Disorders
• Heartburn/GERD
– Chronic heartburn 
GERD
– Reduced by smaller
meals, less fat
– Smoking weakens the
esophageal sphincter
– Being overweight often
worsens symptoms
Nutrition and GI Disorders
• Irritable Bowel Movement (IBS): disruptive state
of intestinal motility with no known cause
– Causes abdominal pain, diarrhea, or
constipation and cramps
– Stress and certain foods aggravate the
symptoms
– Can usually be controlled by diet and lifestyle
modifications
• Stress management
Nutrition and GI Disorders
• Colorectal cancer: cancer in colon or rectum
– Fiber-rich diet may reduce risk
– ____ leading cause of cancer-related deaths in
the US
– Eating a lot of red meat and low fiber food can
increase risks
• Gas
– Most foods that contain carbohydrates can
cause
Nutrition and GI Disorders
• Ulcers
– Pain in the upper
abdomen
– Can cause nausea,
vomiting, loss of appetite,
and weight loss
– Cause: Bacteria (H. pylori)
and over-usage of NSAIDS
(aspirin, ibuprofen)
Nutrition and GI Disorders
• Functional Dyspepsia:
– Chronic pain in the upper abdomen not due to
any obvious physical cause (such as
inflammation of the esophagus, peptic ulcer, or
gallstones)
– Treat with medicine and stress reduction