Chapter 11: Human
Organization
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Types of Tissues
• A tissue is composed of specialized cells
that perform a function in the body.
• The human body has four major types of
tissues:
• Epithelial tissue
• Connective tissue
• Muscular Tissue
• Nervous Tissue
• Cancers are classified by the type of
tissue from which they arise:
• Carcinomas – cancers of epithelial tissue
• Sarcomas – cancers of connective tissue
• Leukemias – cancers of blood
• Lymphomas – cancers of lymphatic tissue
• Cancers are more likely to arise in tissues
in which cells divide rapidly.
Epithelial Tissue
• Epithelial tissue (epithelium) is made of
highly packed cells that line the body
surface and inner body cavities.
• Epithelial tissue functions in protection,
secretion, absorption, excretion, and
filtration.
• Epithelial tissue is classified according to
cell type.
• Squamous epithelium is composed of
flattened cells and is found lining the lungs
and blood vessels.
• Cuboidal epithelium contains cube-shaped
cells and is found lining the kidney tubules.
• Columnar epithelium has elongated cells
with nuclei at the bottom of cells and is
found in the digestive tract.
• Ciliated columnar epithelium is found lining
the oviducts.
• Epithelial tissue is also classified
according to the number of layers in a
tissue.
• Simple means the tissue has a single layer
of cells.
• Stratified means the tissue has layers of
cells piled on top of one another.
• Pseudostratified means the epithelium
appears layered but is not.
Simple squamous epithelium
Simple cuboidal epithelium
Simple columnar epithelium
Pseudostratified ciliated columnar
epithelium
• A basement membrane joins epithelium to
an underlying layer of connective tissue.
• Some epithelial cells are glandular and
secrete a product.
• A gland may be a single cell or contain
many cells.
• Mucus-secreting digestive glands are
single goblet cells.
• Exocrine glands secrete products into
ducts, while endocrine glands secrete
directly into the bloodstream.
Junctions Between Epithelial Cells
• Junctions that occur between cells help
cells function as a tissue.
• A tight junction forms an impermeable
barrier between cells.
• A gap junction allows material to pass from
one cell to the next.
• Adhesion junctions adhere cells together
so tissues can stretch.
Connective Tissue
• Connective tissue binds organs together,
provides support and protection, fills
spaces, produces blood cells, and stores
fat.
• Connective tissue cells are separated by
noncellular matrix that ranges from solid to
semifluid.
• The matrix houses fibers of three possible
types.
•
• White collagen fibers contain the protein
collagen; these fibers are flexible and
strong.
• Reticular fibers are very thin, highly
branched collagen fibers that form delicate
supporting networks.
• Yellow elastic fibers contain the protein
elastin; these fibers are more elastic and
not as strong as collagen fibers.
Loose Fibrous and Dense Fibrous
Tissues
• Loose fibrous and dense fibrous
connective tissues have cells called
fibroblasts in a matrix containing collagen
and elastic fibers.
• Loose fibrous connective tissue supports
epithelium and many internal organs.
• Dense fibrous connective tissue, packed
with collagen fibers, is found in tendons
and ligaments.
Loose fibrous connective tissue
Adipose Tissue and Reticular
Connective Tissue
• In adipose tissue, fibroblasts enlarge and
store fat to be used for energy, insulation,
and organ protection.
• Adipose tissue is found beneath the skin
and around certain internal organs.
• Reticular connective tissue forms the
supporting meshwork of lymphoid tissue in
lymph nodes, the spleen, thymus, and
bone marrow.
Adipose tissue
Cartilage
• Cartilage cells lie in small chambers called
lacunae separated by a solid but flexible
matrix.
• Hyaline cartilage contains very fine
collagen fibers and is found at the ends of
bones, in respiratory passages, and in the
nose.
• The fetal skeleton is made of hyaline
cartilage and is replaced by bone.
Hyaline cartilage
• Flexible elastic cartilage has abundant
elastic fibers and is found in the framework
of the outer ear.
• Fibrocartilage has a matrix with strong
collagen fibers.
• Fibrocartilage is found in structures that
withstand tension and pressure, such as
the pads between the vertebrae in the
backbone and the wedges in the knee
joint.
Bone
• Bone is the most rigid connective tissue
with its matrix of calcium and other
inorganic salts and protein fibers.
• Compact bone makes up the shafts of
long bones and consists of cylindrical units
called osteons.
• Osteons contain a central canal through
which blood vessels carry blood and
nutrients to bone tissue.
Compact bone
• In compact bone, cells lie within lacunae
which are interconnected by tiny nutrientdelivering canals called canaliculi.
• The ends of long bones contain spongy
bone.
• Spongy bone contains many bony bars
and plates located along lines of stress,
separated by irregular spaces.
• Spongy bone is strong yet lightweight.
Blood
• Blood is a fluid connective tissue
containing blood cells in liquid plasma.
• Blood has many functions:
• Keeps body chemistry within limits
• Transports nutrients and wastes to cells
• Distributes heat
• Keeps pH and ions in balance
• Protects against blood loss and disease
Blood, a fluid tissue
Components of Blood Plasma
• Inorganic ions:
(electrolytes)
• Gases:
• Plasma proteins:
• Organic nutrients:
• Nitrogenous wastes:
• Na+, Ca2+, K+, Cl2,
HCO3-, HPO42+
• O2, CO2
• Albumins, globulins,
fibrinogen
• Glucose, lipids, amino
acids, phospholipids
• Urea, ammonia
• Formed elements of the blood include:
• Red blood cells – small, biconcave, and
lacking nuclei, with hemoglobin that
transports oxygen
• White blood cells – larger, nucleate, and
fight infection and produce antibodies
• Platelets – fragments of larger cells that
form a plug in damaged blood vessels,
thus helping in the clotting process
Formed elements of blood
Muscular Tissue
• Muscular tissue is made up of cells
called muscle fibers.
• All muscular tissue contains actin
filaments and myosin filaments; the
interaction of these accounts for
movement.
• Three types of vertebrate muscle are
skeletal, smooth, and cardiac.
• Skeletal muscle, under voluntary control,
is attached by tendons to bones and
allows for movement.
• Skeletal muscle fibers are long and
cylindrical with many nuclei just inside the
plasma membrane.
• Actin filaments and myosin filaments form
a striated appearance in skeletal muscle.
Skeletal muscle
• Smooth (visceral) muscle is involuntary
and nonstriated.
• Long, tapered cells, each with a single
nucleus, form layers within the smooth
muscle.
• Smooth muscle is found in the walls of the
digestive tract and in blood vessels.
• Smooth muscle contracts more slowly
than skeletal muscle but can remained
contracted for a longer period.
Smooth muscle
• Cardiac muscle is found only in the walls
of the heart and functions to pump blood.
• Cardiac muscle has striations but is
involuntary.
• Cardiac muscle fibers are branched and
have a single nucleus.
• Cells are bound end to end at intercalated
disks, areas where plasma membranes
between cells contain adhesion junctions
and gap junctions.
Cardiac muscle
Nervous Tissue
• Nervous tissue found in the brain and
spinal cord is made up of cells called
neurons.
• Neurons have three parts:
• Dendrites – carry impulses to the neuron
• Cell body – houses nucleus
• Axon – carries impulse away from cell
• Axons are insulated with myelin; axons are
bound together to form nerves.
• In addition to neurons, nervous tissue
contains neuroglia, cells that support and
nourish neurons.
• Three types of neuroglia are found in the
brain:
• Microglia support neurons and engulf
bacteria and cellular debris
• Astrocytes provide nutrients and secrete a
hormone called glia-derived growth factor
• Oligodendrocytes form myelin.
A neuron and some types of
neuroglia
Body Cavities and Body
Membranes
• The human body is divided into the ventral
cavity and the dorsal cavity.
• During development, the coelom becomes
the ventral cavity, which is divided into
thoracic and abdominal cavities.
• The thoracic cavity contains the pleural
cavities each containing a lung, and the
pericardial cavity housing the heart.
Mammalian body cavities
• The thoracic cavity is separated from the
abdominal cavity by the diaphragm.
• The upper abdominal cavity contains the
stomach, liver, spleen, gall bladder, and
most of the intestines.
• The lower abdominal cavity contains the
rectum, urinary bladder, and the rest of the
large intestine.
• The dorsal cavity contains the cranial
cavity that houses the brain, and the
vertebral canal that contains the spinal
cord.
Body Membranes
• Here the term “membrane” refers to a thin
lining of epithelium overlying a layer of
loose connective tissue.
• Body membranes line cavities and internal
spaces of organs and tubes that open to
the outside.
• There are mucous membranes, serous
membranes, synovial membranes, and
meninges.
• Mucous membranes line the tubes of
digestive, respiratory, urinary, and
reproductive systems.
• Mucus secreted by goblet cells in the
epithelial layer of mucous membrane
protects the body from invasion by
bacteria and viruses.
• Mucus also protects the lining of the
stomach from digestive juices.
• Serous membranes line the thoracic and
abdominal cavities and the organs they
contain and secrete a watery fluid that
lubricates the membranes.
• Serous membranes have specific names
according to their location:
• Pleura - line pleural cavity and cover lungs
• Pericardium - lines pericardial cavity and
covers heart
• Peritoneum - lines abdominal cavity where
it forms a double-layered mesentery.
• Synovial membranes line freely movable
joint cavities.
• They secrete lubricating synovial fluid into
the joint cavity that helps bones move
freely.
• The meninges are membranes in the
dorsal cavity that protect the brain and
spinal cord.
• Meninges are composed of connective
tissue only.
Organ Systems
• Organs work together in organ systems;
all body organ systems work together.
• A single organ may be part of more than
one organ system.
• The integumentary system is made up of
the skin, including an outer epidermis and
an inner dermis.
• Skin covers and protects the body, houses
sensory receptors, and helps in
temperature regulation.
• The integumentary system includes nails,
glands, sensory receptors, and hairs.
• The digestive system consists of the mouth,
esophagus, stomach, small intestine, and large
intestine along with associated organs.
• The digestive system receives and breaks down
food into nutrient molecules that are distributed
to cells.
• The cardiovascular system, made up of the
heart and blood vessels, distributes nutrients,
oxygen, and heat throughout the body, and
helps to remove wastes.
• The lymphatic system consists of lymphatic
vessels that transport lymph, lymph nodes, and
other lymphoid organs,
• This system helps protect again disease by
producing and storing lymphocytes, collects
excess tissue fluid, and absorbs fats from
digestion.
• The immune system consists of all body cells
that protect against disease.
• The respiratory system consists of the lungs and
branched tubes that carry air to them.
• The respiratory system brings in oxygen and
removes carbon dioxide from the body, and
helps regulate pH.
• The urinary system, made up of kidneys, urinary
bladder, and tubes that convey urine, rids the
body of nitrogenous wastes, and regulates fluid
balance and pH.
• The bones skeletal system protect the body and
aid in movement; they also store minerals and
calcium and produce blood cells in bone
marrow.
• The muscular system, made up of the skeletal
muscles, provides movement and generates
heat for the body.
• Smooth muscle and cardiac muscle provide
movement of internal organs.
• The nervous system, made up of the
brain, spinal cord, and nerves, receives
and processes information, and causes
the body to react to stimuli; the nervous
system regulates the activities of the other
organ systems of the body.
• The endocrine system consists of
hormone-secreting glands, helps to
regulate the functioning of other body
systems.
• The reproductive systems produce sperm
and egg cells, allowing humans to produce
more of their own kind.
Integumentary System
• The skin and its accessory organs make
up the integumentary system.
• Skin plays a significant role in
homeostasis by protecting underlying
tissues from trauma, infection, and water
loss, and by helping to regulate
temperature.
• The skin synthesizes vitamin D and
houses sensory receptors.
Regions of the Skin
• The skin has two regions:
• Outer epidermis made up of stratified squamous
epithelium, with waterproof keratin, and pigmentproducing melanocytes
• Inner dermis made up of fibrous connective
tissue with collagen and elastic fibers, blood
vessels, and sensory receptors.
• A subcutaneous layer, composed of loose
connective and adipose tissues, connects the
dermis to underlying organs.
Human skin anatomy
Accessory Organs of the Skin
• Nails, glands, and hair are structures of
epidermal origin even though they are
located in the dermis.
• Nails are a protective covering of the ends
of the fingers and toes; these increase
dexterity.
• Nails grow from cells in the nail root; these
become keratinized as they grow over the
nail bed.
Nail anatomy
• Hair follicles are in the dermis and extend
through the epidermis; arrector pili
muscles allow the hair to become erect.
• Each hair follicle has oil (sebaceous)
glands that secrete moisturizing sebum.
• Sweat (sudoriferous) glands are present in
all regions of the skin and play a role in
temperature regulation.
Homeostasis
• Homeostasis is the relative constancy of
the body’s internal environment.
• Internal conditions fluctuate slightly in
dynamic equilibrium.
• Illness results if internal conditions vary to
a great degree.
• A homeostatic mechanism in the body has
a sensor, a regulatory center, and an
effector.
Homeostasis
Negative Feedback
• Negative feedback is the primary
homeostatic mechanism that keeps a
variable close to its set point.
• A home heating system, with its
temperature set at 68oF (the set point),
operates by negative feedback; many
negative feedback mechanisms in the
body function in a similar manner.
Negative feedback
Regulation of Body Temperature
• The regulatory center for body
temperature is located in the brain’s
hypothalamus.
• When body temperature is below normal,
the hypothalamus sends nervous impulses
to the skin blood vessels and they
constrict, conserving heat.
• If cooling continues, skeletal muscles are
signaled, shivering ensues, generating
heat and raising body temperature.
• When body temperature is higher than
normal, the regulatory center directs skin
blood vessels to dilate, radiating heat to
the outside.
• Sweat glands are also activated, and
evaporation helps to lower body
temperature.
• Temperature drops to normal, and the
regulatory center is inactivated.
Homeostasis and body
temperature regulation
Positive Feedback
• Positive feedback mechanisms bring
about an ever greater change in the same
direction and does not achieve relative
stability; they may have a cut-off point.
• Examples of positive feedback:
• Childbirth and the hormone oxytocin
• Blood clotting
• Digestion of protein in the stomach
• Certain fevers
Homeostasis and Body Systems
• The internal environment of the body
consists of blood and tissue fluid.
• The chemical composition of tissue fluid
remains constant only as long as blood
composition remains constant.
• All systems of the body contribute toward
maintaining homeostasis and therefore a
relatively constant internal environment.
Regulation of tissue fluid
composition
Chapter Summary
• Human tissues are organized into four
groups.
• Epithelial tissues cover the body and line
its cavities.
• Connective tissues bind body parts
together.
• Muscle tissue allows the enter body or its
internal organs to move and contract.
• Nervous tissue conducts nerve impulses.
• The internal organs occur within cavities.
• Major body cavities include the ventral
cavity, with thoracic and abdominal
portions, and the dorsal cavity, which
includes the cranial cavity and vertebral
canal.
• Body membranes line body cavities and
the internal spaces of organs, and include
mucous, serous, and synovial
membranes, and the meninges.
• Organ systems provide coordinated
functions for the body.
• Processing and transporting functions are
provided by the digestive, cardiovascular,
lymphatic, respiratory, and urinary
systems.
• The musculoskeletal system supports the
body and permits movement.
• The nervous system detects changes and
responds to stimuli and controls the
activities of other organ systems.
• The endocrine system produces
hormones, some of which affect the
reproductive system.
• Skin covers and protects the body, houses
sensory receptors, and helps in
temperature regulation.
• Homeostasis is the relative constancy of
the internal environment.
• Most homeostasic mechanisms are by
negative feedback, although some use
positive feedback.
• All organ systems contribute to the
homeostasis of tissue fluid and blood.
Chapter 12: Digestive System
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Digestive system
The Mouth
• Lips and cheeks enclose the mouth.
• Taste buds on the tongue provide the
sense of taste; skeletal muscle in the
tongue allows it to move.
• The roof of the mouth is formed by the
hard and soft palates that separate it from
the nasal cavities.
• The soft palate ends in a finger-shaped
projection called the uvula.
• Tonsils at the back sides of the mouth
protect against infections.
• Tonsillitis results when the tonsils become
inflamed; the infection can spread to the
middle ears.
• Three pairs of salivary glands send saliva
(containing salivary amylase for digestion
of starch to maltose) into the mouth.
The Teeth
• Twenty deciduous (baby) teeth are
replaced by 32 adult teeth.
• Each tooth has a crown and a root.
• The crown has a layer of enamel, dentin,
and an inner pulp with nerves and blood
vessels that extend into the root.
• The tongue mixes the chewed food with
saliva and then forms the mixture into a
mass called a bolus in preparation for
swallowing.
Adult mouth
Longitudinal section of a tooth
The Pharynx
• The air passage and food passage cross
in the pharynx because the trachea is
ventral to the esophagus.
• Swallowing occurs in the pharynx and is a
reflex action.
• During swallowing, the air passage is
usually blocked off by the soft palate and
uvula, and the trachea moves under the
epiglottis to cover the glottis opening to the
windpipe.
Swallowing
The Esophagus
• The esophagus is a muscular tube that
conducts food through the thoracic cavity
and diaphragm into the stomach.
• Peristalsis begins in the esophagus; this
collapsed tube moves the bolus of food
downward after swallowing occurs.
• Heartburn is a burning pain when acidic
stomach contents enter the esophagus.
• No chemical digestion occurs in the
esophagus.
• The entrance of the esophagus to the
stomach is marked by a constriction,
called a sphincter; the sphincter must relax
in order for food to enter the stomach.
• The sphincter prevents food from backing
up into the esophagus.
The Wall of the Digestive Tract
• The digestive tract wall has four layers:
• Mucosa (mucous membrane – secretes
digestive enzymes and mucus),
• Submucosa (loose connective tissue –
houses blood and lymph vessels),
• Muscularis (two layers of smooth muscle for peristalsis), and
• Serosa (serous membrane – secretes
serous fluid to prevent sticking).
Wall of the digestive tract
The Stomach
• The stomach expands to store food.
• Food in the stomach is churned, mixing
the food with gastric juices containing
hydrochloric acid and pepsin for the
digestion of protein to peptides.
• Alcohol, but not food, is absorbed here.
• In 2–6 hours, the soupy chyme leaves the
stomach.
• Ulcers are usually caused by a bacterial
infection.
Anatomy and histology of the
stomach
Ulcer
The Small Intestine
• The small intestine, averaging about 6
meters in length, is small in diameter.
• The first 25 cm is the duodenum that
receives bile from the gallbladder and
pancreatic juice containing pancreatic
lipase and trypsin for digestion of protein
to peptides, as well as lipase for digestion
of fat to glycerol and fatty acids.
• Pancreatic juice contains NaHCO3 that is
basic and neutralizes the acidic chyme.
• Enzymes that finish the process of
digestion are produced by the intestinal
wall.
• Walls of the small intestine have finger-like
projections called villi where nutrient
molecules are absorbed into the
cardiovascular and lymphatic systems.
• Villi have microvilli that increase the
surface area available for absorption.
• The small lymphatic capillary in a villus is
called a lacteal.
Anatomy of the small intestine
Regulation of Gastric Secretions
• Both the nervous system and chemicals
called hormones regulate digestive juice
secretion.
• In response to eating protein foods, the
hormone gastrin is produced by the lower
part of the stomach and flows through the
bloodstream to stimulate the stomach to
produce digestive juice.
• The duodenal wall produces gastric
inhibitory peptide (GIP) to inhibit gastric
gland secretion.
• The hormones secretin and
cholecystokinin (CCK) are produced by
the duodenal wall and stimulate the
pancreas to secrete digestive juice and the
gallbladder to release bile.
• Acidic chyme stimulates the secretion of
secretin, while fatty chyme with protein
triggers CCK release.
Hormonal control of digestive gland
secretions
The Large Intestine
• The large intestine consists of the cecum,
colon, rectum and anal canal.
• The large intestine does not produce
digestive enzymes but does absorb water,
salts, and some vitamins.
• The colon includes the ascending colon,
the transverse colon, the descending
colon, and the sigmoid colon.
• The appendix is an extension of the
cecum.
• Indigestible material is stored in the
rectum until the anus allows defecation.
• Anaerobic bacteria in the feces break
down indigestible material and produce
some vitamins.
• Water tests that show the presence of the
bacterium Escherichia coli indicate water
is contaminated.
Junction of the small intestine and
the large intestine
• Polyps are small growths arising from the
epithelial lining that may be benign or
cancerous.
• Diarrhea and constipation are two
common complaints of the large intestine.
• Causes of diarrhea include infection of the
lower tract and nervous stimulation, both
moving feces more rapidly than normal,
but also causing dehydration if prolonged.
• Water and fiber in the diet can prevent
constipation where the feces become too
dry and hard.
• Hemorrhoids are enlarged and inflamed
blood vessels at the anus; this condition is
associated with chronic constipation.
• Regular elimination reduces the time the
colon wall is exposed to cancer-promoting
agents in the feces and may help prevent
cancer.
Defecation reflex
The Pancreas
• The pancreas produces pancreatic juice,
which contains digestive enzymes for
carbohydrate (pancreatic amylase),
protein (trypsin), and fat (lipase), along
with sodium bicarbonate (NaHCO3) to
neutralize acid in chyme.
• The pancreas is also an endocrine gland
that secretes insulin and glucagon,
hormones that keep blood glucose within
normal limits.
The Liver
• The liver produces bile, which is stored in
the gallbladder.
• Bile emulsifies fats; it is a yellowish-green
substance containing bilirubin from
hemoglobin breakdown and bile salts
derived from cholesterol.
• The liver acts as gatekeeper to the blood
and receives blood from the small intestine
by way of the hepatic portal vein.
Hepatic lobules
• The functions of the liver are many:
• detoxifies blood,
• stores iron and vitamins,
• makes plasma proteins,
• stores glucose as glycogen,
• produces urea from amino acids,
• removes bilirubin after dismantling blood
cells, and
• regulates blood cholesterol level when
producing bile salts.
Hepatic portal system
Liver Disorders
• When a person has a liver disorder,
jaundice may occur.
• Jaundice is a yellowish tint to eyes and
skin, indicating abnormal levels of blood
bilirubin.
• Hepatitis is inflammation of the liver;
different strains of virus cause hepatitis A,
B, etc.
• Cirrhosis is scar tissue that can form when
the liver is diseased or killed by exposure
to alcohol.
The Gallbladder
• The gallbladder is a pear-shaped muscular
organ that stores bile until it is sent to the
duodenum.
• Water is reabsorbed in the gallbladder
making the bile thick and mucus-like.
• Bile enters the duodenum via the common
bile duct.
• Gallstones are crystals of cholesterol.
• Peptidases and maltase, produced by the
small intestine, complete the digestion of
proteins and starches, respectively.
• Glucose and amino acids are absorbed
into the blood capillaries of the villi.
• Fatty acids and glycerol rejoin in the villi to
produce lipoprotein droplets which enter
the lacteals.
• Digestive enzymes speed specific
reactions and function best at a warm
body temperature and optimum pH.
Conditions for Digestion
• For digestion to occur the correct enzyme,
optimum pH, optimum temperature, and
the correct substrate must be present.
• Exact conditions can be determined during
laboratory experiments.
• Most digestive enzymes, aside from
pepsin, require a basic pH.
Digestion experiment
Food guide pyramid: A guide to
daily food choice
Carbohydrates
• Complex carbohydrates from foods like
breads and pasta can be converted to
glucose and used rapidly.
• Body cells can utilize fatty acids as an
energy source, but brain cells require
glucose, thus carbohydrates are an
essential part of the diet.
• Complex, rather than simple,
carbohydrates should make up the bulk of
the diet.
• Simple carbohydrates like table sugar
(sucrose) contribute to energy needs and
weight gain without supplying other
nutrients.
• Insoluble fiber helps regularity and may
help prevent cancer by limiting the time
substances are in contact with the
intestinal wall.
• Soluble fiber combines with bile acids and
cholesterol in the intestine and prevents
them from being absorbed.
Complex carbohydrates
Proteins
• Meat, milk or eggs are complete proteins;
they provide all 20 essential amino acids.
• Because individual vegetables do not
provide all essential amino acids,
vegetarians must be careful to consume a
combination of legumes, grains,
vegetables, seeds and nuts to secure
complementary proteins.
• The amino acid pool relies on continual
uptake; amino acids are not stored.
Ancient versus modern diet of
native Hawaiians
Lipids
• Fat and cholesterol are lipids.
• Lipids, found in fats and oils, should be
used sparingly.
• Current guidelines suggest that fat should
account for 30% or less of daily calories.
• High-density lipoproteins (HDL) carry
cholesterol to the liver and is considered to
be “good”.
• Low density lipoprotein (LDL) takes
cholesterol to the cells and may contribute
to the development of plaque on blood
vessels walls; it is considered to be “bad”.
• Saturated fatty acids lack double bonds
and raise LDL cholesterol levels.
• Linoleic acid and linolenic acid are two
essential fatty acids the body cannot
make; polyunsaturated fats supply these.
Fake Fat
• Olestra looks, tastes, and acts like real fat
but the digestive system cannot digest it;
therefore, it is called “fake fat”.
• However, fat-soluble vitamins are taken up
by olestra and pass through the digestive
system unabsorbed.
• Those who consume olestra have reduced
carotenoids in their blood.
Vitamins
• Vitamins are organic compounds that the
body cannot produce but needs for
metabolic purposes; some are portions of
coenzymes.
• Vitamins A, E, and C are antioxidants that
protect cell contents from damage due to
free radicals.
• Free radicals donate an electron to DNA,
proteins, enzymes, membranes, etc. and
can damage cell structures or cause cancer.
• Vitamin D
• A precursor molecule in skin is converted
to vitamin D after exposure to ultraviolet
(UV) light.
• Vitamin D is modified first in the kidneys
and then the liver until it becomes
calcitriol, which is needed for calcium
absorption in intestines.
• In the U.S., milk is often fortified by vitamin
D.
• Vitamin D is a fat-soluble vitamin.
Illnesses due to vitamin deficiency
Minerals
• The body contains more than 5 grams of
each major minerals and less than 5
grams of each trace minerals.
• Calcium and phosphorus are in bones and
teeth.
• Potassium and sodium are involved in
nerve conduction.
• Trace minerals are critical in various
enzymes and hormones.
Minerals in the body
• Calcium
• Calcium is needed to have strong bones.
• Older women in particular are at risk for
osteoporosis, a degenerative bone
disease due to insufficient intake of
calcium because bone cells are constantly
building and eroding bone tissue.
• Calcium supplement with vitamin D (and
also estrogen for women) can help prevent
this bone loss.
• Sodium
• Most Americans have too much salt in
their diet.
• High sodium intake is linked to
hypertension in some persons.
• About one-third of the sodium we
consume occurs naturally in foods;
another one-third is added during
commercial processing; and the final onethird is added during cooking or at the
table in the form of table salt.
Eating Disorders
• Obesity is defined as a body weight of
more than 20% above the ideal weight for
that person.
• Obesity can have hormonal, metabolic,
and social causes.
• For many, a commitment to a sensible diet
and exercise program can prevent obesity
or a harmful cycle of weight gain-and-loss.
Recognizing obesity
• Bulimia nervosa is characterized by a
restrictive diet, binging, and purging.
• Psychotherapy and antidepressants may
help.
• Anorexia nervosa is characterized by a
distorted body image and feeling fat even
when emaciated.
• It can be life-threatening and carries the
same risks as starvation.
Recognizing bulimia nervosa
Recognizing anorexia nervosa
• The mouth, pharynx, esophagus, stomach,
small and large intestines have distinct
functions and hormones control digestive
gland secretions.
• The pancreas, liver, and gallbladder are
accessory organs of digestion; their
secretions assist digestion.
• The products of digestion are small
molecules, such as amino acids and
glucose, that can cross plasma
membranes.
• Digestive enzymes are specific and have
an optimum temperature and pH.
• Proper nutrition supplies the body with
energy and nutrients, including essential
amino acids and fatty acids, and all
vitamins and minerals.
• Anorexia nervosa, bulimia, and obesity are
primary eating disorders in the United
States.
Lab Ex 19: Platyhelminthes
(flatworms)
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Flatworms
• Flatworms are characterized by the tissue
level of organization and a sac body plan.
• These acoelomates (NO coelom) have
three germ layers, and have all organs
except respiratory and circulatory organs.
• The flat body facilitates diffusion of oxygen
and other molecules from cell to cell.
• Planarians
• Planarians are freshwater, free living,
flatworms.
• Flame cells function in excretion.
• The small brain extends to a ladder
arrangement of nerves.
• Light-sensitive organs (eyespots) are in
the head; planarians exhibit cephalization.
• One organism has both male and female
sex organs – they are hermaphroditic.
Planarian
• Parasitic Flatworms
• Flukes and tapeworms are two classes of
parasitic flatworms; both have intermediate
hosts.
• Flukes are oval to elongate and have suckers at
the anterior end.
• Blood flukes cause schistosomiasis; other
flukes infect the digestive tract, bile duct, and
lungs.
• A tapeworm has an anterior scolex with hooks
and suckers to hold itself inside the gut.
Schistosomiasis
Lab Ex 20: Aschelminthes
(roundworms)
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Roundworms
• Roundworms have the tube-within-a-tube
plan; they are prevalent in soil and some
parasitize animals and plants.
• The pseudocoelom is a body cavity
incompletely lined with mesoderm.
• The fluid-filled interior forms a hydrostatic
skeleton.
• Most species of roundworms have separate
males and females.
Coelom structure and function
• Ascaris
• Ascaris larvae are swallowed and burrow
through the intestinal wall and make their way
through various organs until they reach the
lungs.
• In the lungs, they grow in size for 10 days, then
move up to the throat, and are then swallowed.
• After they mature in the intestine, females
produce eggs that pass out with feces.
Roundworm anatomy
• Other Roundworms
• Trichinosis is a roundworm infection from
eating undercooked pork containing encysted
Trichinella larvae.
• The filarial worm is carried by mosquitoes and
causes elephantiasis by blocking lymphatic
drainage.
• Pinworms are common infections in children.
• Hookworm is a more serious infection seen in
the southern United States.