Chapter 6
Overview of Body Systems and
Their Functions
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Anatomy and Physiology
• Anatomy is the branch of science that deals
with the structure of body parts, their forms,
and their organization
• Physiology concerns the functions of body
parts – how they work and what they
accomplish
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Integumentary System
• The skin, and the various accessory structures
that are associated with it, is the largest organ
in the body by surface area
• Integumentary structures include the hair,
nails, sensory receptors, and glands
• Together they make up the integumentary
system
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The Skin
• Certain skin cells called keratinocytes assist
the immune system by producing hormonelike substances that stimulate development of
certain white blood cells (T lymphocytes)
• Specialized cells in the epidermis called
melanocytes produce melanin, a dark pigment
that provides skin color and that also absorbs
the ultraviolet radiation in sunlight
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Skin Layers
• The outer skin layer, called the epidermis, is
composed of stratified squamous epithelium
• The inner layer, or dermis, is thicker than the
epidermis
(continues)
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Skin Layers
• It includes connective tissue consisting of:
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Blood
Collagenous and elastic fibers
Nervous tissue
Smooth muscle
Sebaceous glands
Sweat glands
(continues)
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Skin Layers
• Beneath the dermis is loose connective tissue
that binds the skin to the underlying organs,
forming the subcutaneous layer
(continues)
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Skin Layers
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Musculoskeletal System
• This system actually consists of two different systems
that work closely together to support the frame and
allow movement of the body
• It includes connective tissue, muscles, bones, and
joints
• The muscular system consists of skeletal, smooth, and
myocardial muscles
• The skeletal system consists of bones and joints
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Divisions of the Adult Skeleton
• Axial skeleton
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Skull (8 cranial bones, 14 facial bones)
Middle ear (6 bones)
Hyoid bone (1)
Vertebral column (26 bones)
Thoracic cage (25 bones)
(continues)
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Divisions of the Adult Skeleton
• Appendicular skeleton
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Pectoral girdle (4 bones)
Upper limbs (60 bones)
Pelvic girdle (2 bones)
Lower limbs (60 bones)
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Joints and Structures
• The joints allow the body to be mobile and
flexible
• The capsule or bursa surrounding the joints is
lined with a connective (synovial) membrane
that has fluid inside
• Diseases of the joints are called arthritis
• Osteoporosis is a condition in which bone
mass is reduced
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Nervous System
• The nervous system is composed of the brain,
spinal cord, and nerves
• It is divided into two sections:
– Central nervous system (CNS)
– Peripheral nervous system (PNS)
• The CNS is located in the dorsal cavity, the
brain is enclosed in the cranium, and the spinal
cord is inside the spinal cavity
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The Brain
• The brain is subdivided into the cerebrum,
diencephalon, brainstem, and cerebellum
• The cerebrum consists of 2 cerebral
hemispheres, connected by the corpus
callosum
• The diencephalon contains the thalamus and
hypothalamus
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Peripheral Nervous System
• The peripheral nervous system (PNS) consists
of cranial and spinal nerves
• They branch from the brain and spinal cord to
all body parts
• The PNS is subdivided into the somatic and
autonomic nervous systems
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Autonomic Nervous System
• The autonomic nervous system (ANS)
functions without any conscious effort, and it
regulates the visceral activities that maintain
homeostasis
• It is subdivided into the sympathetic and
parasympathetic nervous systems
• The sympathetic nervous system responds to
stress and emergency situations
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Neurons and Structures
• The neuron is the basic cell of the nervous
system, carrying nerve impulses from one part
of the body to another
• At the junction of the neurons, the continuation
of messages is performed by neurotransmitters,
such as acetylcholine (ACh), which stimulates
the nerve endings
(continues)
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Neurons and Structures
• There are some other neurotransmitters, called
neurohormones, including:
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Cholinesterase
Catecholamines
Serotonin
Endorphins
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Parts of the Neuron
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Special Senses (Eyes and Ears)
• The special senses are those whose sensory
receptors lie within large, complex sensory
organs in the head
• These senses and their respective organs
include:
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Smell (olfactory organs)
Taste (taste buds)
Ears (hearing and equilibrium)
Eyes (sight)
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Eyes
• The eyes contain visual receptors and provide
vision with the assistance of accessory organs
• These accessory organs include eyelids and
lacrimal apparatus
(continues)
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Eyes
• The eye is a hollow, spherical structure about
2.5 centimeters in diameter
• The anterior of the outer layer bulges forward
as the transparent cornea (the “window” of the
eye)
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Parts of the Eye
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Ears
• The ears are the organs of hearing and also
function in the sense of equilibrium
• The outer portion is called the auricle
• The 2nd portion is an S-shaped tube called the
external acoustic meatus
(continues)
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Ears
• These bones transmit sound vibrations from
the eardrum to the oval window
• The auricle of the ear helps to:
– Collect sound waves
– Directs the sound waves into the eardrum (tympanic
membrane)
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The Middle Ear
• The middle ear is an air-filled space that
contains 3 small bones called auditory ossicles
(called malleus, incus, and stapes)
• These bones transmit sound vibrations from
the eardrum to the oval window
• The auditory tube (eustachian tube) connects
the middle ear to the throat (pharynx)
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Parts of the Middle Ear
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The Inner Ear
• The inner ear is a complex system of
connected fluid-filled chambers and a tube
called a labyrinth
• The parts of the labyrinth include:
– Three semicircular canals, which provide a sense of
equilibrium
– One cochlea, which functions in hearing
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Endocrine System
• The endocrine system consists of specialized
cell clusters, glands, hormones, and target
tissues
• It regulates metabolic activities, and along
with the nervous system, it maintains internal
homeostasis
• Endocrine glands secrete hormones, or
chemical messengers, directly into the
bloodstream
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Organs and Hormones
• The major organs of the endocrine system are
the:
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Hypothalamus
Thyroid gland
Adrenal glands
Testes
– Pituitary gland
– Parathyroid glands
– Pancreas
– Ovaries
(continues)
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Organs and Hormones
• Insulin is secreted when blood glucose levels
rise
• Glucagon is released when blood glucose
levels fall below normal
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Hormonal Regulation
• The hypothalamus is the main integrative
center for the endocrine and autonomic
nervous systems
• It helps control some endocrine glands by
neural and hormonal pathways
• The hypothalamus also exerts hormonal
control at the anterior pituitary gland by
releasing and inhibiting hormones and factors,
which arrive by a portal system
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Hormones
• Hormones are natural chemical substances
secreted into the bloodstream from the
endocrine glands that regulate and control the
activity of an organ or tissues in another part
of the body
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Endocrine Glands and
Their Hormones
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Hypothalamus – GnRH, GHRH, TRH
Anterior Pituitary – GH, ACTH, TSH, LH, FSH, PRL
Posterior Pituitary – OT, ADH
Thyroid – T4, T3, Calcitonin
(continues)
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Endocrine Glands and
Their Hormones
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Parathyroid – PTH
Thymus – Thymosin
Pancreas – Insulin, Glucagon
Adrenal Cortex – Cortisol, Aldosterone, Androgens
(continues)
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Endocrine Glands and
Their Hormones
• Adrenal Medulla – Epinephrine, Norepinephrine
• Testes – Testosterone
• Ovaries – Estrogen, Progesterone
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Pituitary Gland
• The pituitary gland is under the control of the
hypothalamus in the brain
• It is small, situated at the base of the brain
• It is also called the “master gland”
• It secretes hormones directly into the
bloodstream to control and regulate the other
endocrine glands
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Anterior Pituitary Gland
• The anterior lobe of the pituitary gland is
particularly important in sustaining life
• It secretes:
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Growth hormone (somatotropin, GH)
Adrenocorticotropic hormone (ACTH)
Thyroid-stimulating hormone (TSH)
Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Prolactin (PRL)
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Posterior Pituitary Gland
• The posterior lobe of the pituitary gland, or the
neurohypophysis, is the release point of
antidiuretic hormone (ADH, or vasopressin)
and oxytocin
• It releases ADH when stimulated by the
hypothalamus
• The hormone acts on the distal and collecting
tubules of the kidneys
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Thyroid Gland
• The thyroid gland is located in the anterior
neck and is the largest of the endocrine glands
• It secretes 3 hormones essential for proper
regulation of metabolism:
– Thyroxine (T4)
– Triiodothyronine (T3)
– Calcitonin
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Parathyroid Glands
• Four tiny parathyroid glands lie along the
posterior surface of the thyroid gland
• They secrete parathyroid hormone (PTH or
parathormone)
• The stimulus for the release of PTH is a low
plasma level of calcium, targeting the bones,
digestive tract (intestines), and kidneys
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Adrenal Glands
• The adrenal glands are located at the top of
each kidney
• They consists of an outer cortex and an inner
medulla
• The cortex synthesizes glucocorticoids
(cortisol), mineralocorticoids (primarily
aldosterone) and androgens
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Pancreas
• The pancreas is one of the accessory organs of
the digestive system, located below the
stomach
• It produces digestive enzymes that are
deposited in the small intestine
(continues)
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Pancreas
• The most important disease involving the
endocrine pancreas is diabetes mellitus, a
disorder of carbohydrate metabolism that
involves either:
– Insulin deficiency
– Insulin resistance
– Both insulin deficiency and resistance
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Gonadal Hormones
• Three main classes of steroid hormones are
produced by gonadal tissues:
– Estrogenic
– Progestational
– Androgenic
• The ovary is the primary site for synthesis and
secretion of estrogen and progestin hormones
in women
(continues)
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Gonadal Hormones
• In men and postmenopausal women, the
principal source of estrogen is adipose tissue
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Ovarian Hormones
• The ovaries are known as gonads
• They produce ova and form endocrine
secretions that initiate and maintain the
secondary sex characteristics in women
• The gonadotropins from the pituitary gland are
responsible for the development and
maintenance of sexual gland functions
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Progesterone
• During a female’s reproductive years,
progesterone is secreted primarily by the
ovarian cells in the corpus luteum at the time
of ovulation
• The greatest amount of progesterone is
secreted during the week after ovulation has
taken place
(continues)
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Progesterone
• It is responsible for the changes in the uterine
endometrium during the 2nd half of the
menstrual cycle
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Testicular Hormone
• The hypothalamus, anterior pituitary gland,
and testes secrete hormones that control male
reproductive functions
• These hormones initiate and maintain sperm
cell production and oversee the development
and maintenance of male secondary sex
characteristics
• Androgens include testosterone and
androsterone
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Cardiovascular System
• The cardiovascular system consists of the heart
and blood vessels
• The heart is a hollow muscular organ located
within the mediastinum, resting on the
diaphragm
• The heart is divided into two atria and two
ventricles
• The right atrium receives blood from the venae
cavae
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Cardiovascular System
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Blood Vessels
• The blood vessels include arteries, capillaries,
and veins
• The heart’s pumping forces blood through the
arteries, which connect to the smaller diameter
vessels
(continues)
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Blood Vessels
• The tiniest tubes, the capillaries, are the sites
that exchange:
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Nutrients
Electrolytes
Gases
Wastes
• Capillaries converge into venules, which in
turn converge into veins that return blood to
the heart
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Blood
• Blood consists of red blood cells, white blood
cells, and platelets suspended in a liquid
known as plasma
• It transports substances between body cells
and the external environment, helping to
maintain a stable internal environment
(continues)
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Blood
• Red blood cells contain hemoglobin, which
combines with oxygen
• White blood cells are either:
– Granulocytes (neutrophils, eosinophils, and basophils)
– Agranulocytes (which include monocytes and
lymphocytes)
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White Blood Cell Actions
• Neutrophils and monocytes phagocytize foreign
particles
• Eosinophils kill parasites and help to control
inflammation and allergic reactions
• Basophils release heparin, which inhibits blood
clotting, and histamine, which increases blood
flow to injured tissues
• Lymphocytes produce antibodies that attack
specific foreign substances
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White Blood Cells
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Lymphatic System
• The lymphatic system, like the cardiovascular
system, includes a network of vessels that
transport fluids
• It is made up of a vast collection of cells and
biochemicals that travel through lymphatic
vessels, as well as the organs and glands that
produce them
(continues)
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Lymphatic System
• Special capillaries called lacteals are located in
the lining of the small intestine where they:
– Absorb digested fats
– Transport the digested fats to the venous circulation
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Lymphatic System and Immunity
• The lymphatic system consists of:
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Lymph
Lymph nodes and vessels
Tonsils
Spleen
Thymus gland
Peyer’s patches (tissue found in the ileum of the small
intestine)
(continues)
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Lymphatic System and Immunity
• Immunity against disease also protects against
toxins and cancer
• When the body’s immune response is not
normal, the result may be:
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Infections
Cancers
Autoimmune disorders
Allergies
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Respiratory System
• The most important function of the respiratory
system is inspiration of oxygen and expiration
of carbon dioxide
(continues)
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Respiratory System
• The respiratory system consists of
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Nasal passages
Mouth
Pharynx
Larynx
Trachea
Lungs
Skeletal muscles of the chest wall
Diaphragm
(continues)
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Respiratory System
• Lung bronchioles end in alveolar ducts and
sac-like clusters called alveolar sacs (alveoli)
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Urinary System
• Cells produce a variety of wastes that are toxic
if they accumulate
• The urinary system removes certain salts and
nitrogenous wastes, and helps maintain the
normal concentrations of water and
electrolytes in body fluids
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Urinary System
• The urinary system consists of:
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Two kidneys
Ureters
Urinary bladder
Urethra
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Nephrons
• A kidney contains about 1 million nephrons
• Each nephron consists of a renal corpuscle
and a renal tubule
• The nephron begins as a double-walled globule
known as Bowman’s glomerular capsule
• A renal corpuscle is composed of a cluster of
blood capillaries called a glomerulus
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Structures of the Nephron
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Digestive System
• The digestive tract is a hollow tube extending
from the mouth to the anus
• Mechanical digestion is the breakdown of
large food particles into smaller pieces by
physical means
• Chemical digestion is the chemical alteration
of food
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Digestive System
• The digestive system basically consists of:
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Mouth
Esophagus
Stomach
Liver
Large and small intestines
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