Download 7-2 Body Systems

7-2 Body Systems
Key Concepts
h- What are the structures and functions of the
body's organ systems?
h- How do the body's organ systems help maintain
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Key Terms
• skeleton • joint • integumentary system • heart
• arteries • capillaries • veins • alveoli • kidneys
• bladder • urethra • hormone
homeostasis?
The nervous system is one of the eleven organ systems in the human
body. A system is a group of independent but interrelated parts. Each
of the body's systems has unique structures and functions, and they all
help to maintain homeostasis.
Skeletal System h- The skeletal system has five major functions. It provides shape and support, enables you to move, protects
your organs, produces blood cells, and stores minerals and other
materials until your body needs them. The skeleton is made up of all
the bones in one's body. A joint is a place in the body where two bones
come together. Joints allow bones to move in different ways.
Muscular System The muscular system consists of about 600
muscles. Your body has three types of muscle tissue-skeletal, smooth,
and cardiac. ~ Muscles are responsible for the voluntary and
involuntary movement of body parts. The muscles that are not under
your conscious control are called invpluntary muscles. Involuntary
muscles are responsible for activities such as circulating blood and
digestmg food. The muscles that are under your control are called voluntary muscles.
Integumentary System The integumentary system is made up
of skin and other body coverings such as hair and nails. The skin has
several major functions. ~ The skin covers and protects the body
from injury, infection, and water loss. It also helps regulate body
temperature, eliminate wastes, gather information about the environment, and produce vitamin D.
Digestive System The digestive system is made up of the mouth,
esophagus, stomach, liver, pancreas, gall bladder, and intestines.
~ The digestive system has three main functions. First, it breaks
down food into molecules the body can use. Then, the molecules are
absorbed into the blood and carried throughout the body. Finally,
wastes are eliminated from the body.
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Cardiovascular System The cardiovascular system consists of
the heart, blood vessels, and blood. ~ The cardiovascular system
carries needed substances to cells and carries waste products away
from cells. In addition, blood contains cells that fight disease. The
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skeleton
joint
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integumentary system _ _
heart is a hollow, muscular organ that pumps blood throughout the
body. Blood travels through three kinds of 1;>lood vessels-arteries,
capillaries, and veins. Arteries carry blood away from the heart to the
capillaries. Capillaries are tiny vessels where substances are exchanged
between the blood and body cells. Veins carry blood back to the heart.
Respiratory System ij-,. The respiratory system moves oxygen
from the outside environment into the body. It also removes carbon
dioxide and water from the body. As you breathe in, air passes
through the nose, pharynx, trachea, and bronchi on the way to the
lungs. Inside the lungs, each bronchus divides into smaller and smaller
tubes. At the ,ends of the smallest tubes are bunches of alveoli, tiny sacs
of lung tissue surrounded by capillaries. There, oxygen and carbon
dioxide gases are exchanged.
Excretory System The excretory system consists of the kidneys,
ureters, urinary bladder, and urethra. ij-,. The excretory system collects wastes produced by cells and removes them from the body. The
two kidneys are the major organs of the excretory system. Each kidney
contains about a million nephrons, tiny structures that filter wastes
such as urea from the blood. The wastes are eliminated in urine. Urine
is stored in the bladder, a saclike organ, until it is released through a
small tube called the urethra. ij-,. Excretion maintains homeostasis
by keeping the body's internal environment stable and free of harmfullevels of chemicals.
Immune System Your body has several lines of defense against
pathogens, or disease-causing organisms. In the first line of defense,
the surfaces of the skin, breathing passages, mouth, and stomach function as barriers, preventing most pathogens from entering the body.
Pathogens that get past the barriers trigger the second line of defense
known as the inflammatory response, in which white blood cells
known as phagocytes fight the disease. If the phagocytes do not
destroy the pathogen, the immune system responds with specialized
white blood cells called lymphocytes that target specific pathogens.
This third line of defense is known as the ,immune response.
Endocrine System The major glands that make up the endocrine
system are the hypothalamus, pituitary, thyroid, parathyroid, adrenal,
thymus, and pancreas. The endocrine system also includes the ovaries
in females and testes in males. ij-,. The endocrine system produces
, chemicals that control many of the body's daily activities. The
endocrine system also regulates long-term changes such as growth
and development. The chemical product of an endocrine gland is
called a hormone. Hormones turn on, turn off, speed up, or slow
dOW'"l the activities of different organs or tissues.
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78
heart
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/
arteries
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capillaries
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veins
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alveoli
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kidneys
-:-
Reproductive System h
The human reproductive system's
function is to produce new offspring by sexual reproduction. The
male reproductive system is specialized to produce sperm and the hormone testosterone. Its structures include the testes, scrotum and penis.
The role of the female reproductive system is to produce eggs and, if
an egg is fertilized, to nourish a baby until birth. The organs of the
female reproductive system include the ovaries, fallopian tubes,
uterus, and vagina.
bladder
Maintaining Homeostasis h
The syste~s of the body each
perform functions that are important for the 'body to maintain
homeostasis. Without the organ systems, the body could not survive
and meet its needs.
urethra
Section 7-2 Assessment
hormone
1. Making Analogies
nescribe how a body system is like an ecosys-
tem.
2. Predicting How might the structure andfunction of the integumentary system be impaired bynot applying sunscreen? What
other body system might be affected?
3. Sequencing Describe the process by which gases are exchanged,
in the respiratory system.
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Study Guide
Check (V') the concepts and terms you know.
oh
Section 7·1 Body Organization and
Homeostasis
o KEY TERMS· tissue· organ· organ system
o
o
o
• homeosta,sis • stimulus· response • impulse
• nerve
h The human body is organized from least to
most complex structures-from cells to
tissues, to organs, and to organ systems.
h Homeostasis is the process by which an
organism's internal environment is kept
stable in spite of changes in the external
environment.
h The nervous system receives information.
about what is happening both inside and
outside your body. By directing the way
your body responds to this information,
the nervous system helps maintain homeostasis.
o
o
o
o
Section 7·2 Body Systems
o KEY TERMS· skeleton· joint· integumentary
o
o
o
The digestive system breaks down food
into molecules the body can use. Then, the
molecules are absorbed into the blood and
carried throughout the body. Finally,
wastes are eliminated from the body.
h The cardiovascular system carries needed
substances to cells and carries waste products away from cells. In addition, blood
contains cells that fight disease.
h The respiratory system moves oxygen from
the outside environment into the body. It
also removes carbon dioxide and water
from the body.
h The excretory system collects wastes pro.
duced by cells and removes them from the
bod~
.
h Excretion maintains homeostasis by keeping the body's internal environment stable
and free of harmful levels of chemicals.
O· h The endocrine system produces chemicals
that control many of the body's daily activities. The endocrine system also regulates
long-term changes such as growth and
development.
o &---7 The human reproductive system's function
is to produce new offspring by sexual
reproduction.
.
h The systems of the body each perform
functions that are important for the body
to maintain homeostasis.
system· heart· arteries· capillaries· veins
• alveoli· kidneys· bladder· urethra
• hormone
h The skeletal system provides shape and
support, enables you to move, protects
your organs, produces blood c~lls, an?
stores minerals and other matenals until
your body needs them.
h Muscles are responsible for the voluntary
and involuntary movement of body parts.
h The skin covers and protects the body .
from injury, infection, and water loss. It
also helps regulate body temperature,
eliminate wastes, gather information about
the environment, and produce vitamin D.
o
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80