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Chapter 3 / Body Systems 71
Blood vessels
Intestines
contractions
(peristalsis)
Wall of heart
the heart
Involuntary Slow, sustained
Tapered at both ends
Single nucleus
Nonstriated
Involuntary Pumps blood out of
Branching networks
Single nucleus
Light striations
Nucleus
Intercalated
discs
Voluntary Movement of skeleton Attached to bones
Long, cylindrical
Multinucleated
Nucleus
Heavy striations
Nucleus
Type of
Muscle Cell Cell Characteristics Control Function Location
Smooth
Cardiac
Skeletal
72 INTRODUCTION TO MASSAGE THERAPY
resting lengths allows sufficient space between muscle cells
for adequate blood circulation and nutrient–waste exchange,
thus enhancing the health of the tissues. Reflexive and
mechanical techniques are covered in detail in the Massage
Strokes and Flow and Therapeutic Applications chapters.
Cardiac Muscle
Cardiac muscle is another type of muscle tissue that is found
only in the walls of the heart. It has light striations and only
one nucleus per muscle cell, but the cells branch together
at tight junctions and gap junctions called intercalated (inTER-kuh-lay-ted) discs. The gap junctions allow the electrical impulses that signal muscle contraction to move quickly
across the heart. Cardiac muscle contracts involuntarily, which
is why our heart continues to beat while we are asleep and
why we cannot consciously control the contractions.
Smooth Muscle
Smooth muscle, sometimes called visceral muscle, has cells
that are nonstriated and tapered at both ends. Each smooth
muscle cell has only one nucleus and is involuntarily controlled. Although it provides a weaker contraction than
skeletal or cardiac muscle, it can sustain contractions for a
longer time. Smooth muscle tends to be arranged in layers, and the fibers of each successive layer run in a different
direction than those in the previous layer. Figure 3-13 illustrates smooth muscle layering in the stomach. These layers
alternate contractions to produce peristalsis, which is the
wavelike pulsating contraction that propels substances along
a tube in the body. For example, the digestive tract has layers
of smooth muscle that push its contents in one direction,
from the mouth toward the anus, via peristalsis.
Nervous Tissue
Nervous tissue has a specialized structure that serves as the
communication path for controlling activity within our bodies. The nervous tissues send electrochemical impulses to
and from different parts of the body to receive stimuli and
trigger bodily responses. The structural components that
make up the brain, spinal cord, and nerves include two kinds
of nervous tissue cells called neurons (NOO-rahnz) and neuroglia (noo-ROH-glee-uh).
Neurons
A neuron , or nerve cell, is a specialized cell that is the
basic unit of nervous tissue. A neuron has a unique structure with three basic parts: a body, a single axon, and
dendrites (Fig. 3-14). The body of the neuron is similar
Dendrites
Cell body
Nucleus
Oblique muscle layer
Ring muscle layer
Longitudinal muscle layer
Figure 3-13. Layering of smooth muscle in the stomach.
Myelin
Neuromuscular
junction
Muscle
Figure 3-14. Basic nerve cell structure.
Axon
covered with
myelin sheath
Chapter 3 / Body Systems
73
to other cells because of its generally rounded shape that
holds the nucleus and other cytoplasmic organelles.
Unlike other cells, the cytoplasm and plasma membrane
have long branches that protrude from the body of the
cell that receive and send the electrochemical impulses
of nerve signal transmission. Dendrites are the processes
radiating out from the cell body that receive electrochemical nerve impulses from other neurons and carry them to
the cell body. Neurons usually have a lot of dendrites and
can receive input from many other neurons. The axon is
a long, single process radiating out from the body of the
neuron that conducts nerve impulses from the cell body
to another cell. Axons can also branch to carry impulses to
many cells at once. The process of nerve signal transmission is like a chain of communication in which the dendrites receive the signal and pass it along to the cell body,
and then the axon carries the signal from the cell body to
another neuron, where it is received by the dendrites of
the second neuron, and so on. Massage activates this chain
of communication in a number of ways. For example,
when we first touch our clients, the tactile input stimulates
an electrochemical impulse to travel along the plasma
membrane from the dendrites, toward the cell body, out
the axon, and then to another neuron. The impulse continues to travel along the neurons until it reaches the
central nervous system (CNS), at which point the client’s
body responds to the initial touch. The client’s response
will be influenced by your professionalism, standards of
care, and respect for the client’s physical and conceptual
boundaries, discussed in the chapter covering Ethics and
Professionalism.
Some neurons are covered with a white, fatty material called myelin. It functions as insulation, significantly
increasing the speed of nerve impulses. When myelinated
nerves lose their myelin or the myelin becomes hardened,
nerve transmission may become problematic. Myelinated
axons appear as white fibers that, when grouped together, are called white matter. Groups of unmyelinated
nerve cells are called gray matter. Figure 3-15 is a cross
section of the spinal cord, showing the gray matter of the
nerve cell bodies and the white matter made of myelinated axons.
Ventral horn
Spinal pia mater
Subarachnoid
space
Spinal arachnoid
mater
Spinal dura mater
Dorsal horn
Spinal canal
Gray matter
(nerve cell bodies)
DORSAL
Lateral horn
White matter
(myelinated axons)
Dorsal root
Dorsal root ganglion
Spinal nerve
Ventral root
(6X)
VENTRAL
Figure 3-15. Cross section of the spinal cord, showing the gray and white matter. (Reprinted from Bear MF, Connors
BW, Parasido MA. Neuroscience: Exploring the Brain. 2nd ed. Philadelphia: Lippincott Williams & Wilkins, 2001.)
74 INTRODUCTION TO MASSAGE THERAPY
Neuroglia
Neuroglia, also called glial (GLEE-uhl) cells, are connective tissue
cells that support and protect neurons, connect them to blood
vessels, produce myelin, destroy and remove pathogens and cellular debris, and help circulate the cerebrospinal fluid (CSF). They
are structurally similar to neurons but cannot transmit impulses.
Tissue Membranes
Membranes are thin sheets of tissues with many different
characteristics that give rise to different functions:
• Serve as a covering for the outside of the body
• Serve as a covering for organs
• Serve as an anchor for organs
Figure 3-16. Locations of epithelial
membranes. (A) Serous. (B) Mucous.
(C) Cutaneous.
• Act as a partition between structures
• Serve as a lining for tubes of cavities in the body
• Reduce friction between structures
Membranes can be fragile, tough, or transparent, and
some contain cells that secrete lubricating fluids. There are
two general classifications of membranes: epithelial and
connective tissue membranes.
Epithelial Membranes
Epithelial membranes are constructed with an epithelium that
is integrated onto an underlying layer of connective tissue. The
connective tissue layer, in addition to the closely packed epithelial cells, creates strong and protective membranes. There are
three types of epithelial membranes: serous (SEER-us), mucous
(MYOO-kus), and cutaneous (kyoo-TAY-nee-us) (Fig. 3-16).
Parietal pleura
Mucous membrane
of nasal passages
Mucous membrane
of the bronchi in lungs
Mucous
membrane of
the digestive
tract
Visceral pleura
Parietal
peritoneum
Visceral
peritoneum
Parietal pericardium
Visceral pericardium
A. Serous membranes
Cutaneous
membrane
(skin)
C. Cutaneous membraneB. Mucous membrane
Chapter 3 / Body Systems 75
Serous Membranes
Serous membranes are composed of a layer of simple squamous epithelial cells atop a thin layer of areolar connective
tissue. The serous membranes line the ventral (anterior)
body cavities and cover the organs within those cavities.
Serous membranes contain cells that secrete serous fluid, a
thin lubricant that allows organs to move and slip past each
other with minimal friction during normal body movements. Serous membranes have a layered, folded construction that forms two different layers of each membrane.
The parietal (puh-RAHY-eh-tuhl) layer of a serous membrane lines the wall of a body cavity, and the visceral layer
of that same serous membrane covers the organs within
that body cavity.
Three types of serous membranes, shown in
Fig.3-16A, are found in the human body: the pleura (PLURuh), the pericardium (PAIR-ih-KAR-dee-um), and the peritoneum (PAIR-ih-toh-NEE-um). The pleura, or pleural
membranes, are located in the thoracic cavity. The parietal
layer of the pleura lines the interior walls of the thoracic
cavity, and the visceral layer covers the lungs. The pericardium is also located in the thoracic cavity, but its parietal layer
forms the sac that encloses the heart, and its visceral layer
covers the heart muscle itself. The peritoneum is located
in the abdominal cavity. The parietal peritoneum lines the
abdominal cavity walls and the visceral peritoneum covers,
supports, and protects most of the organs and structures
within the abdomen.
Mucous Membranes
Cutaneous Membrane
Cutaneous membrane, commonly called skin, has an outer
layer of stratified squamous epithelial tissue over a layer of
connective tissue (Fig. 3-16C). Functioning primarily to protect the body from the environment, the cutaneous membrane is the only kind that is dry. The skin is discussed in the
section on the integumentary system.
Connective Tissue Membranes
Connective tissue membranes consist of sheets of connective
tissue without an attached epithelium. The different forms of
connective tissue membranes include synovial membranes,
meninges, connective tissue sacs around organs, and fascia.
Synovial Membranes
Synovial (sin-OH-vee-uhl) membranes line the joint cavities,
tendon sheaths, and bursae, which are the small cushioning
sacs located in some of the larger joints. These membranes
secrete synovial fluid, a thick, clear substance that has the
consistency of egg white. This slippery secretion nourishes
the articular cartilage and lubricates and reduces friction in
the following locations:
• At the freely movable joints
• Between muscles
• Between a tendon and ligament
• Between a muscle and a ligament
Mucous membranes are epithelial membranes that line
tubes and spaces that are exposed to the outside of the body.
These membranes are made of simple and/or stratified
epithelium resting on a layer of soft connective tissue and
form continuous linings in the digestive, respiratory, reproductive, and urinary systems. The primary function of most
of these wet membranes is to secrete mucus, a viscous and
sticky substance that moistens and protects the membranes.
Examples of mucous membranes are shown in Fig.
3-16B. In the nasal passages and the bronchi in the lungs,
mucus keeps the passages wet, despite exposure to external
air. The mucus also traps pathogens that enter the respiratory pathway. Ciliated cells in the respiratory tract then sweep
the mucus and foreign particles up and outward, away from
the lungs, to protect us against infection and to get rid of
pathogens that have already entered the respiratory tract. In
the digestive tract, the mucus has several different functions.
It acts as a protective barrier against the strong acids that
break down food. When the mucus barrier breaks down, the
acids can attack the organs, resulting in ulcers and irritation
within the digestive tract. The mucous membranes located
toward the end of the digestive tract secrete mucus that
traps the nutrients made available as a result of our food
being broken down.
Meninges
Meninges (men-IN-jeez) consist of multiple membrane layers that cover the brain and spinal cord. The dura mater,
arachnoid mater, and pia mater are the three meningeal layers that function as protective coverings. These connective
tissue membranes are discussed below, in the section on the
nervous system.
Connective Tissue Coverings
Connective tissue surrounds many anatomical structures in
the form of connective tissue sacs. The heart is encased in
a fibrous membrane sac called the pericardium, the bones
are covered with periosteum, and cartilage is covered with
perichondrium.
Fascia
Fascia (FASH-uh), sometimes called the fascial sheath, is a fibrous
band or sheetlike tissue membrane that provides support and
protection for the body organs. Fascia wraps around everything
in the body, stabilizing, protecting, and supporting organs and mus-
Fascia is very pervasive, forming a sort of three-dimensional
cles.
meshwork throughout the body. A restriction or adhesion in the
76 INTRODUCTION TO MASSAGE THERAPY
fascia is an area where the smooth membrane has been crumpled or kinked with some sort of trauma; additional collagen
fibers are deposited in the area, and a scar is created that pulls the
surrounding fascia toward it. This resultant tension and pulling
action can even affect anatomical structures that are a significant
distance away, causing a number of problems:
• Restricted movement
• Compensation patterns
• Reduced circulation
• Muscular tension
• Pain in areas that seem completely unrelated
This situation is common following surgery. For a couple of
weeks after surgery, the area that was surgically repaired is usually subjected to minimal movement to give the incision a chance
to heal. The fascia has already been disrupted, and without
movement, the body’s healing response deposits fascia on top of
the disruption, essentially fixing the disruption into place with a
fascial adhesion. The three-dimensional nature of fascia creates a
situation where the rest of the fascia is pulled toward the adhesion. For example, clients who have ankle surgery may complain of tightness or restricted movement in the knee. Clients
who have abdominal surgery could feel tightness in the neck or
shoulder. Massage therapy can reduce fascial restrictions, helping to restore normal function to the body. Specific massage
techniques have been especially designed to manipulate the
fascia and are discussed in the Therapeutic Applications chapter.
Superficial fascia is a continuous sheetlike layer
composed of mostly adipose connective tissue with some
interspersed collagen and elastin fibers that provide:
• Energy from the fat stored in the adipose cells
• Protection for the skin
• A passageway for nerves
• A passageway for circulatory vessels
• Thermal insulation
Sometimes called the subcutaneous layer or the hypodermis, superficial fascia lies just beneath the surface of the
skin. It is dense and anchors the skin firmly to underlying
tissues.
Deep fascia is found in and around every skeletal muscle.
It wraps almost every structure of a muscle, starting with
the wrapping around a muscle cell, called the endomysium.
Several wrapped fibers together form fascicles, which are
wrapped in perimysium. The entire muscle, made up of
several fascicles, is wrapped in the epimysium. Figure 3-17
shows the deep fascia surrounding structures of a muscle.
Deep fascia contains no fat and is mostly composed of collagen fibers and some elastin, making it very strong and
a little pliable. It functions to cover, separate, and protect
the muscles. This tissue has a thixotropic quality, meaning
that it is a gelatinous substance that without movement can
thicken, contract, and become less pliable. When the deep
fascia is stiff and contracted, it restricts muscle movement
and circulation within the muscles. On the other hand,
the thixotropic quality also means that deep fascia can be
thinned to a more fluid or liquid state with mechanical
manipulation. Massage therapy can provide the manipulation to thin the deep fascia and encourage movement and
circulation. A special form of deep fascia, thicker than the
muscular coverings and running transversely to the muscle
fibers, is called a retinaculum. Found in small areas that
contain numerous tendons, such as the wrist and ankle,
retinacula hold the tendons down in a particular position
or location.
Anatomy and physiology of the human body is a large and
very complex topic that can easily overwhelm any student.
For that reason, the information is often broken up into
smaller pieces that are more approachable. As mentioned
before, this text presents only an introduction to human
anatomy and physiology, dividing the information into
12separate body systems: integumentary, skeletal, muscular, nervous, cardiovascular, lymphatic, respiratory, digestive,
urinary, endocrine, reproductive, and special senses.
Integumentary System
The integumentary (in-TEG-yoo-MENT-ah-ree) system
includes the skin, hair, nails, and the glands that reside
in or near the skin. Massage therapists should know
about the integumentary structures, particularly the
skin, because the client’s skin is the initial point of physical contact and is touched continually throughout the
massage.
Functions of the Integumentary
System
The main function of the integumentary system is to protect our bodies from the environment, but it also serves as a
means of communication, helps regulate body temperature,
provides a means of excretion, and participates in the formation of vitamin D.
Chapter 3 / Body Systems
77
Tensor
fascia lata
Deep
fascia
Superficial fascia
Iliotibial tract
Fascia lata
Crural fascia
Bursae
Gluteus
maximus
Iliotibial tract Fascia lata
Anterior
Superficial fascia
Fascia lata
(deep fascia)
Anterior
Lateral
Posterior
Figure 3-17. Deep fascia surrounding muscle.
Femur
Lateral
Iliotibial tract
Skin
Superficial
fascia
Tibia
Medial
Crural fascia (deep fascia)
Deep fascia
Deep fascia
Medial
Posterior
78 INTRODUCTION TO MASSAGE THERAPY
Protection
The skin is waterproof and resistant to many chemicals
and bacteria. Its strength and pliability make it tough to
outside physical forces such as sharp edges. Essentially, it
keeps the inside structures in and the outside substances
out. Keratin is a protein in skin cells that makes our skin
water repellant, so water cannot soak through it. Acidic
skin secretions help resist chemical damage and help prevent bacterial growth. Additionally, the skin protects the
body from ultraviolet radiation damage. Coloration cells
in the skin are called melanocytes (meh-LAN-oh-sahytz).
Exposure to sunlight increases the production of melanin,
creating a suntan. The darkening of the skin helps shield
the cell nucleus from ultraviolet damage, like sunglasses
for the DNA.
Communication
Most essential for massage therapy is the skin’s communication function. Cutaneous receptors in the skin detect
touch, pressure, pain, and temperature and send their
sensory signals to the brain and spinal cord for processing.
These structures are made of nervous tissue. In addition to
the skin’s function of transmitting external stimuli to the
inside of our bodies, the color and texture of the skin can
reveal information about the processes going on inside the
body. For instance, a liver dysfunction can lead to excessive
amounts of liver chemicals that make the skin yellowish.
Low levels of oxygen in the blood will cause the skin to
look grayish.
Thermal Regulation
A very important function of the integumentary system is
thermal regulation. The skin helps regulate body temperature via the capillaries, sweat glands, and fat. The body’s
thermostat recognizes a safe range for core body temperature. When the core temperature is too high, the body
responds with vasodilation, or expanding blood vessels,
in the skin. That allows heat to be dissipated by the large
surface of the skin. When the core temperature drops too
low, the body responds with vasoconstriction (blood vessel
constriction) in the skin, which reduces blood flow to the
skin in an effort to conserve heat in the body. Sweat glands
diffuse water through the skin, and in a low-humidity environment, the water evaporates and helps cool the body.
Evaporative cooling is less effective when humidity in the
air is high, because the water from our bodies cannot diffuse
into the air. Subcutaneous fat, or the fat in the superficial
fascia, also acts as a thermal insulator, preventing heat from
being transferred into or out of the body. In cold temperatures, fat keeps body heat in the body and does not allow
the cold external temperatures to affect the internal organs,
which is usually a good thing. However, when it is hot, fat
still keeps body heat in the body, which makes it harder for
the body to dissipate heat and maintain the proper core
temperature.
Excretion
Excretion (ehks-KREE-shun) is a minor role of the integumentary system. Metabolic processes create chemical wastes
that the body cannot use. The body can eliminate unwanted salts and water from the skin via perspiration. Nitrogen
wastes such as urea are also excreted in minimal amounts
through the skin.
Vitamin D Formation
Vitamin D is critical in the process of absorption of calcium
for proper bone growth and normal cell growth. The production of vitamin D is another important function of the
skin. Although we can obtain vitamin D from food sources
such as milk, this is one of two vitamins that can be produced by the body. A form of cholesterol located in the skin,
when exposed to the sun’s ultraviolet rays, is converted into
vitamin D.
Structures of the
Integumentary System
The skin is the main structure of the integumentary system,
but there are also some specialized structures located in or
near the skin, including hair, nails, and cutaneous glands.
The skin, sometimes called the integument, is the largest organ
of the body.
Skin
The skin has a two-layered structure consisting of
the epidermis and dermis (Fig. 3-18). The skin, like all
epithelial membranes, has a layer of epithelial tissue
atop a layer of connective tissue. The epidermis is the
epithelial layer, and the dermis is the connective tissue
layer. The subcutaneous layer, also called superficial fascia or the hypodermis, is another connective tissue layer
beneath the dermis and is sometimes considered part of
the skin.
Epidermis
The outermost layer of our skin, the epithelial layer, is
called the epidermis. It is nonvascular, like all epithelia,
and is composed of up to five layers. From deepest to most
superficial, they are the stratum germinativum, stratum spinosum, stratum granulosum, stratum lucidum, and stratum
corneum. The epidermis is constantly being regenerated,
Chapter 3 / Body Systems
Hair
Epidermal
ridge
Capillary loop
Stratum corneum
Stratum lucidum
Stratum grandulosum
Stratum spinosum
Stratum germinativum
Dermis
Nerve endingNerve ending
Epidermis lifted to reveal
papillae of the dermis
Dermal papillae
79
Epidermis
Epidermis
Sebaceous
Dermis
Figure 3-18. Cross-sectional illustration of skin.
gland
Arrector pili
muscle of hair
Blood vessels
Hair root
Nerve to hair
follicle
which it does rapidly via cell division. Skin cells are formed
in the stratum germinativum, the deepest layer that is closest to the blood vessels in the underlying dermis. The skin
cells slowly progress upward and outward until they reach
the external environment. As they migrate outward, they
accumulate water-repelling keratin and get farther from the
blood vessels that supply nutrients and oxygen. Fortunately
for us, these deteriorated skin cells are sloughed off when
they reach the external environment. It takes approximately
2 to 4 weeks for a cell to migrate through a layer of epidermis, meaning that in 2 to 4 weeks, a person has a completely
new outer layer of skin. This process of renewal keeps our
skin healthy and alive and gives us a water-repellant outer
covering. This constant renewal also helps protect against
cancer by ensuring that damaged cells die before cancer can
develop.
Sweat pore
Papillary layer of dermis
Nerve endings
Reticular layer of dermis
Hypodermis (subcutaneous tissue)
Sweat glands
Adipose tissue
Dermis
The dermis is the layer of connective tissue beneath the epithelium. It is constructed of two layers. The superficial papillary layer is named for its dermal papillae, which are like
spiked mountains that stick up into the epidermis. The papillae are highly vascular structures that provide oxygen and
nutrients to the epidermis that surrounds them. Pain receptors and tactile sensory receptors reside within the dermal
papillae. Beneath the papillary layer is the reticular layer. It is
a dense form of connective tissue that contains blood vessels,
sweat glands, sebaceous glands, and the sensory receptors for
cold, heat, and pressure. The specific sensory receptors are discussed in detail in the nervous system section, but Figure 3-19
illustrates the kinds of sensory reception in the skin. Collagen
and elastin protein fibers give the dermis its toughness and
elasticity. Collagen fibers are hydrophilic, meaning that they
attract water molecules and hold onto them, keeping the skin
80 INTRODUCTION TO MASSAGE THERAPY
Figure 3-19. Five different kinds of sensory recep-
tors in skin.
Pain
Cold Tactile
Heat
Cell bodies
Dendrites
Axons Synapses
sensation
Pressure
hydrated. Elastin fibers give skin elasticity, which is noticeable
in young children. As we age, the collagen and elastin wear
out and diminish, giving us wrinkled, dry skin.
Subcutaneous Layer
The subcutaneous (SUB-kyoo-TAY-nee-us) layer, also known
as the hypodermis or superficial fascia, lies deep to the dermis. It is connected to the dermis with numerous bundles of
elastin protein fibers, so it is difficult to tell where the dermis stops and the subcutaneous layer starts. This fascia binds
the skin to the underlying organs and structures, provides
shock absorption, serves as a thermal insulator, and provides
energy storage. It is highly vascular, has many nerve endings, and contains adipose (fat) cells. The number of fat cells
in a particular person’s superficial fascia varies from one area
of the body to another. For example, the superficial fascia
in the breasts and hips tends to have more fat cells than the
superficial fascia on the hands or elbows. With age or significant weight loss, subcutaneous fat in adipose cells tends to
diminish, and the skin will start to sag.
Nails
Fingernails and toenails are special structures of the skin
(Fig. 3-20A). The free edge of the nail and the body of the
nail are made of hard keratin and are not alive. The nail
body lies upon the nail bed, which is a very thin epidermal
layer over the vascular dermis. This is the part that bleeds
when someone tears a nail too far back. Nails grow from the
root, and their growth rate can be affected by temperature.
The general health of the body can be detected in the nails
because they are the tangible, visible outcome of metabolic
activity. A disease or dysfunction in the body affects homeostasis, and imbalances may show up as a difference in the
quality of the nail. For example, nails that are thin and weak
can be a result of poor nutrition. Nails that appear bluish
can indicate poor circulation in the underlying dermis.
Hair
Hair is present almost everywhere on the body but is more
visible in some areas than in others. It is a nonliving, keratinized protein structure that grows upward from follicles in the
subcutaneous layer. The follicle receives its nutrients from
the blood vessels surrounding it. When fully developed, hair
extends from its root at the base of a long shaft up through
the skin and out into the environment (Fig.3-20B). Hair
provides animals with an additional layer of protection, as
a way of regulating body temperature and as a mechanism
of safety when being faced by a predator. A tiny arrector
pili muscle connects the follicle to the dermis, and when it
contracts, it pushes the hair out farther to make the animal
appear larger (see Fig. 3-18). The same mechanism can trap
air and provide a layer of thermal insulation if the hair is
thick enough. In humans, however, arrector pili muscle contraction usually produces the familiar “goose bumps” on the
skin. What little purpose hair serves for humans includes
light insulation and protection from sunburn. Incidentally,