THE HUMAN BODY
AN ORIENTATION
An Overview
of
Anatomy and Physiology
Anatomy
• Study of the structure of body parts and
their relationships to each other
• Anatomy: Greek meaning to cut apart
Physiology
• Study of the function of body parts
• How all the body parts work and carry
out their life-sustaining activities
Topics of Anatomy
• Gross (macroscopic) anatomy: the study of structures large
enough to be seen with the naked eye
• Regional anatomy: all the body structures (muscles, bones, blood
vessels, nerves, etc.) in a given body region , such as the abdomen
or leg, are examined at the same time
• Systemic anatomy: body is studied system by system
– Example: when studying the cardiovascular system, you would examine
the heart and the blood vessels of the entire body
• Surface anatomy: internal body structures as they relate to the
overlying skin
– Used when identifying the bulging muscles beneath a bodybuilder’s
skin, and clinicians use it to locate appropriate blood vessels in which to
feel pulses and draw blood
Topics of Anatomy
• Microscopic anatomy: the study of structures
that are too small to be seen with the naked eye
– Cytology: study of individual cells
– Histology: study of tissues
• Developmental anatomy: the study of the
change in body structures over the course of a
lifetime
– Embryology: concerns developmental changes that
occur before birth
Topics of Anatomy
• Specialized Branches of Anatomy
– Pathological anatomy: study of structural
changes associated with disease
– Radiographic anatomy: study of internal
structures using specialized visualization
techniques (X-rays or special scanning
devices)
– Molecular biology: study of biological
molecules
Topics of Physiology
• Considers the function of specific organ
systems:
– Examples:
• Renal physiology: concerns kidney function and urine
production
• Neurophysiology: explains the workings of the nervous
system
• Cardiovascular physiology: examines the operation of the
heart and blood vessels
• While anatomy provides us with a static
image of the body’s architecture, physiology
reveals the body’s dynamic nature
Topics of Physiology
• Focuses on cellular and molecular
events:
– Individual cells and the chemical reactions
that go on within them
– Principles of physics which helps to explain
electrical currents, blood pressure, and the
way muscles use bones to cause body
movements
Complementarity of Structure and
Function
• Function is dependent on structure, and the
form of a structure relates to its function:
– What a structure can do depends on its specific
form
– Examples:
• Bones can support body organs because they contain hard
mineral deposits
• Blood flows in one direction through the heart because the
heart has valves that prevent backflow
• Lungs can serve as a site for gas exchange because the
walls of their air sacs are extremely thin
Levels of Structural Organization
• (1):Chemical level is the
simplest level of
organization:
– Atoms, tiny building blocks of
matter, combine to form
molecules such as water and
proteins
– Molecules combine in
specific ways to form
organelles, which are the
basic unit of living cells
– Cells are the smallest units
of living things
• All cells have some common
functions, but individual cells
vary widely in size and shape,
reflecting their unique
functions in the body
Levels of Structural Organization
•
•
(2):Cellular level: smallest unit of
life, and varies widely in size and
shape according to the cell’s
function
(3):Tissue level: groups of similar
cells having a common function
– Four basic tissue types: each
tissue type has a characteristic
role in the body
• Epithelium: covers the body
surface and lines its cavities
• Muscle: provides movement
• Connective: supports and
protects body organs
• Nervous: provides a means of
rapid internal communication by
transmitting electrical impulses
Levels of Structural Organization
•
(4):Organ level: made up of discrete
structures that are composed of a
least two groups of tissues that work
together to perform a specific function
in the body
–
•
(5):Organ system level: a group of
organs that work closely together to
accomplish a specific purpose
–
•
Stomach: epithelium lining, muscles,
blood vessels, connective tissues,
nerve fibers, etc.
Respiratory and circulatory system,
digestive and circulatory systems
(6):Organismal level: the total of all
structures working together to promote
life
–
The living human being
Levels of Structural Organization
Maintaining Life
Necessary Life Functions
• (a): Maintaining Boundaries: allows an organism to
maintain separate internal and external environments, or
separate internal chemical environments
– Integumantary System or Skin
• (b): Movement: allows the organism to travel through
the environment, and allows transport of molecules
within the organism
– Skeletal, Circulatory, Muscular Systems
• (c): Responsiveness: or irritability, is the ability to detect
changes in the internal or external environment and
respond to them
– Muscular System
ORGAN SYSTEMS
Maintaining Life
Necessary Life Functions
• (d): Nervous System:
– Responsiveness to external and internal
environments by activating muscles and glands
• (e): Endocrine System:
– Regulating body functions such as: growth,
reproduction, and nutrition
• (f): Cardiovascular System:
– Transportation of nutrients, waste, gases, and
hormones throughout the body
ORGAN SYSTEMS
Maintaining Life
Necessary Life Functions
• (g): Lymphatic System/Immunity:
– Body defenses
• (h): Respiratory System:
– External and internal gas exchanges
• (i): Digestive System:
– Breakdown and absorption of nutrients
ORGAN SYSTEMS
Maintaining Life
Necessary Life Functions
• (j): Urinary System:
– Absorption of waste from the blood and
elimination
• (k): Male Reproductive System:
– Production of sperm
• (l): Female reproductive System:
– Production of eggs
ORGAN SYSTEMS
Maintaining Life
Necessary Life Functions
• Digestion is the process of breaking down food
into molecules that are usable by the body
• Metabolism includes all chemical reactions
that occur in the body
• Excretion is the process of removing wastes
• Reproduction is the process of producing more
cells or organisms
• Growth is an increase in size in body parts or
the whole organism
Examples of selected interrelationships
among body organ systems
• Integumentary system
protects the body as a whole
from the external environment
• Digestive and respiratory
systems, in contact with the
external environment, take in
nutrients and oxygen,
respectively, which are then
distributed by the blood to all
body cells
• Elimination of metabolic
wastes is accomplished by the
urinary and respiratory
systems
ORGAN SYSTEMS
Survival Needs
• The ultimate goal of all body systems is to maintain life
• Life is extraordinarily fragile and requires that several
factors be present:
– These factors are called survival needs and include:
• Nutrients: consumed chemical substances that are used for energy
and cell building
• Oxygen: required by the chemical reactions that release energy
from foods
• Water: most abundant chemical substance in the body, provides an
environment for chemical reactions and a fluid for secretions and
excretions
• Normal body temperature: required for the chemical reactions of
the body to occur at the proper rate
• Atmospheric pressure: must be within an appropriate range so
that proper gas exchange occurs in the lungs
Homeostasis
• The ability of the body to maintain a
relatively constant internal environment,
regardless of environmental changes:
– Body temperature
– Blood pH
Homeostatic Control Mechanisms
• Communication within the
body is essential for
homeostasis
– Accomplished chiefly by the
nervous and endocrine
systems
• All homeostatic control
mechanisms have at least
three interdependent
components:
• 1. Receptor: type of sensor
that monitors the environment
and responds to changes,
called stimuli, by sending
information (input) to the
second component (control
center)
Homeostatic Control Mechanisms
• 2. Control Center:
– Information flows from
the receptor to the
control center along the
afferent pathway
– Structure that determines
the set point (level or range
at which a variable is to be
maintained) for a variable,
analyzes input, and
coordinates an appropriate
response
• Variable: the regulated
factor or event
Homeostatic Control Mechanisms
•
3. Effector:
– Provides the means for the control
center’s response (output) to the
stimulus
– Structure that carries out the
response directed by the control
center
– Information flows from the
control center to the effector
along the efferent pathway
– The results of the response
then feed back to influence the
stimulus, either depressing it
(negative feedback) so that the
whole control mechanism is
shut off or enhancing it
(positive feedback) so that the
reaction continues at an even
faster rate
CONTROL SYSTEM
Negative Feedback Mechanisms
• Most homeostatic control mechanisms are
negative feedback mechanisms
• In these systems, the output shuts off the
original stimulus or reduces its intensity
– These mechanism cause the variable to change in
a direction opposite to that of the initial change,
returning it to its “ideal” value
• Both the nervous system and the endocrine
system are important to the maintenance of
homeostasis
• The goal of negative feedback mechanisms is
to prevent sudden, severe changes in the body
Negative Feedback Mechanisms
• Home heating system connected to a temperaturesensing thermostat
– Thermostat houses BOTH the receptor and the control center
– If thermostat is set at 20oC (68oF), the heating system (effector)
is triggered ON when the house temperature drops below that
setting
– As the furnace produces heat and warms the air, the
temperature rises, and when it reaches 20oC or slightly higher,
the thermostat triggers the furnace OFF
• This process results in a cycling of “furnace-ON” and “furnace-OFF”
so that the temperature in the house stays very near the desired
temperature of 20oC
– Your body thermostat, located in a part of your brain called
the hypothalamus, operates in a similar fashion
Negative Feedback Mechanisms
•
•
•
To carry out normal metabolism,
body cells need a continuous
supply of glucose, their major fuel for
producing cellular energy, or ATP
Blood sugar levels are normally
maintained around 90 milligrams (mg)
of glucose per 100 millimeters (ml) of
blood
Rising glucose levels stimulate the
insulin-producing cells of the pancreas,
which respond by secreting insulin into
the blood
–
Insulin accelerates the uptake of
glucose by most body cells
•
•
It also encourages storage of excess
glucose as glycogen in the liver and
muscles
Consequently, blood sugar levels
ebb back toward the normal set
point, and the stimulus for insulin
release diminishes
NEGATIVE FEEDBACK
Negative Feedback Mechanisms
•
Glucagon, another pancreatic
hormone, has the opposite effect of
insulin
–
–
–
Its release is triggered as blood sugar
levels decline below the set point
Glucagon secretion is stimulated
Glucagon targets the liver, causing it to
release its glucose reserves from
glycogen into the blood
•
•
Consequently, blood sugar levels
increase back into the homeostatic
range
There are hundreds of Negative
Feedback Mechanisms (regulation
of heart rate, blood pressure, rate
and depth of breathing, and blood
levels of oxygen, carbon dioxide,
and minerals)
NEGATIVE FEEDBACK
Positive Feedback Mechanisms
• Result or response enhances the original stimulus so
that the activity (output) is accelerated
• A positive feedback mechanism causes the variable to
change in the same direction as the original change,
resulting in a greater deviation from the set point
• Positive feedback mechanisms typically activate events
that are self-perpetuating
– Once initiated, have an amplifying effect
• Most positive feedback mechanisms are not related
to the maintenance of homeostasis
– Homeostatic imbalance often results in disease
Positive Feedback Mechanisms
• Examples:
– Enhancement of labor contractions during
birth:
• Oxytocin, a hypothalamic hormone, intensifies
labor contractions during the birth of a baby
– Causes the contractions to become more frequent
and more powerful until the baby is finally born, an
event that ends the stimulus for oxytocin release and
shuts off the positive feedback mechanism
Positive Feedback Mechanisms
• Examples:
– Blood clotting:
• Blood clotting is a normal
response to a break in the
lining of a blood vessel
• 1. Once vessel damaged
has occurred
• 2. Blood elements called
platelets immediately
begin to cling to the
injured site
• 3. Platelets release
chemical that attract more
platelets
• 4. This rapidly growing
pileup of platelets initiates
the sequence of events
that finally forms a clot
POSITIVE FEEDBACK
Homeostatic Imbalance
• Homeostasis is so important that most
disease is regarded as a result of its
disturbance, a condition called
Homeostatic Imbalance
– Causes:
• As we age, our body’s control systems become
less efficient
• Negative feedback mechanisms become
overwhelmed and destructive positive feedback
mechanisms take over
Language of Anatomy
Anatomical Position and Directional Terms
• To describe body parts and position
accurately, we need an initial reference point
and must indicate direction
• The anatomical reference point is a standard
body position called the Anatomical Position
• Anatomical Position: position in which the
body is:
– Erect with feet only slightly apart
– Palms face forward
– Thumbs point away from the body
REGION TERMS
REGION TERMS
Language of Anatomy
Anatomical Position and Directional Terms
• In anatomical position, right and left refer
to the right and left sides of the person
viewed—NOT those of the observer
• In anatomy, anatomical position is always
assumed, regardless of the actual position
of the body
Language of Anatomy
Anatomical Position and Directional Terms
• Directional terms are used to explain
exactly where one body part is in relation
to another
– Example:
• The ears are located on each side of the head to
the right and left of the nose
• Using anatomical terminology, this condenses to,:
– The ears are lateral to the nose
– Saves words and is less ambiguous
– Anatomical meanings are VERY PRECISE
Orientation and Directional Terms
Orientation and Directional Terms
Orientation and Directional Terms
Regional Terms
• There are two fundamental divisions of the
body:
– Axial region:
• Makes up the main axis of our body
• Includes the head, neck, and trunk
– Appendicular region:
• Consists of the appendages, or limbs
• Attached to the body’s axis
• Consists of the upper and lower limbs
• Regional terms are used to designate specific
areas within the major body divisions
– The common term for each of these body regions
is provided (in parentheses)
REGION TERMS
REGION TERMS
Body Planes and Sections
•
For anatomical studies, the
body is often sectioned (cut)
along a flat surface called a
plane
– Body planes are flat surfaces that
lie at right angles to each other
• Sagittal plane: a vertical plane
that separates the body into right
and left parts
– Median, or midsagittal plane:
lies exactly along the body’s
midline
– Parasagittal plane (para=near):
lies offset from the midline
• Frontal plane: a vertical plane
that separates the body into
anterior and posterior parts
• Transverse, or horizontal, plane:
a plane that runs horizontally from
right to left, and divides the body
into superior and inferior parts
BODY PLANES
Body Planes and Sections
• Transverse, or horizontal, plane: a plane that runs
horizontally from right to left, and divides the body into
superior and inferior parts
– Many different transverse planes exist, at every possible level
from head to foot
• Transverse section, or cross section, is a cut made along the
transverse plane
– Oblique sections are cuts made at angles between the horizontal and
vertical planes
• The ability to interpret sections made through the
body, especially transverse sections, is important in
the clinical sciences
– New medical imaging devices produce sectional images
rather than three-dimensional images
BODY PLANES
Body Cavities and Membranes
• Within the axial portion of the body are two
large cavities called the dorsal and
ventral body cavities
• Body cavities are spaces within the body
that are closed to the outside and contain
the internal organs
BODY CAVITIES
BODY CAVITIES
Dorsal Body Cavity
• The space that houses the central nervous
system, and has two subdivisions: the
cranial cavity and the vertebral cavity
– Cranial cavity is within the skull, and
encases the brain
– Vertebral, or spinal, cavity is within the
vertebral column, and encloses the spinal
cord
BODY CAVITIES
BODY CAVITIES
Ventral Body Cavity
• Is anterior to and larger than the dorsal cavity and has two main
subdivisions: the thoracic cavity, and the abdominopelvic cavity
– Houses the body organs collectively called the viscera (viscus=an organ
in a body cavity), or visceral organs
– Thoracic cavity:
• Is a superior division of the ventral cavity that is further subdivided into the
lateral pleural cavities that surround the lungs
• Thoracic cavity also contains the medulla mediastinum, which includes the
pericardial cavity surrounding the heart and the space surrounding the other
thoracic structures (esophagus, trachea, and others)
– Diaphragm Muscle separates the Thoracic and Abdominopelvic
Regions
– Abdominopelvic Regions and Quadrants:
• Inferior to the Thoracic Cavity
• There are nine abdominopelvic regions used primarily by anatomists
• There are four quadrants used primarily by medical personnel
BODY CAVITIES
BODY CAVITIES
Membranes in the Ventral Body Cavity
•
The walls of the ventral body cavity and the outer surfaces of the organs it
contains are covered by a thin, double-layered membrane, the serosa, or
serous membrane
– Serous membranes, or serosae, cover the inner walls of the ventral cavity and
the outer surfaces of organs
• Serous membranes secrete and are separated by a thin layer of lubrication fluid called
serous fluid, which allows organs to slide without friction along cavity walls and
between each other
– Parietal serosa lines the body cavity walls, and is named for the specific cavities
it is associated with
– Visceral serosa covers the outer surfaces of organs, and is named for the
specific organs it is associated with
•
•
•
•
•
•
Parietal pericardium lines the pericardial cavity
Visceral pericardium covers the heart within that cavity
Parietal pleura lines the walls of the thoracic cavity
Visceral pleura covers the lungs
Parietal peritoneum is associated with the walls of the abdominalpelvic cavity
Visceral peritoneum covers most of the organs within that cavity
SEROUS MEMBRANE
• Parietal pericardium
lines the pericardial
cavity
• Visceral pericardium
covers the heart
within that cavity
SEROUS MEMBRANE
Membranes in the Ventral Body Cavity
• You can visualize the
relationship between
the serosal layers by
pushing your fist into a
limp balloon
– The part of the balloon that
clings to your fist can be
compared to the visceral
serosa clinging to the
organ’s external surface
– The outer wall of the
balloon then represents the
parietal serosa that lines
the walls of the cavity
SEROUS MEMBRANE
Homeostatic Imbalance
• When serous membranes are inflamed,
they typically produce less lubricating
serous fluid
– This leads to excruciating pain as the organs
stick together and drag across one another,
as anyone who has experienced pleurisy
(inflammation of the pleurae: thoracic cavity)
or peritonitis (inflammation of the peritoneal:
abdominal cavity)
Abdominopelvic Regions
• Because the abdominopelvic
cavity is large and contains
several organs, it helps to
divide it into smaller areas for
study
– Cavity divided into 9 regions
• Umbilical region: centermost
region deep to and
surrounding the umbilicus
(navel)
• Epigastric region: located
superior to the umbilical
region (epi=upon, above;
gastri=belly)
• Hypogastric (pubic) region:
located inferior to the
umbilical region (hypo=below)
ABDOMINAL REGION
ABDOMINAL REGIONS
Abdominopelvic Regions
• Right and left iliac, or
inguinal regions: located
lateral to the hypogastric
region (iliac=superior part of
the hip bone)(inguinal=groin:
between thigh and trunk)
• Right and left lumbar
regions: lie lateral to the
umbilical region (lumbus=loin:
between ribs and pelvis)
• Right and left
hypochondriac regions: flank
the epigastric region laterally
(chondro=cartilage)
ABDOMINAL REGION
ABDOMINAL REGIONS
Quadrants
• Medical personnel usually
use a simpler scheme to
localize the abdominopelvic
cavity organs
• In this scheme, one
transverse and one median
sagittal plane pass through the
umbilicus at right angles
– The resulting quadrants are
named according to their
positions from the subject’s
point of view:
•
•
•
•
Right upper quadrant (RUQ)
Left upper quadrant (LUQ)
Right lower quadrant (RLQ)
Left lower quadrant (LLQ)
ABDOMINAL REGION
Other Body Cavities
• Oral and digestive cavities are continuous cavities that extend from
the mouth through the digestive system to the anus
• Nasal cavity is within and posterior to the nose
– Part of the respiratory system
• Orbital cavities (orbits) in the skull house the eyes
• Middle ear cavities are within the skull just medial to the eardrums,
and house the bones that transmit sound vibrations to the inner ears
• Synovial cavities are joint cavities
– Enclosed within fibrous capsules that surround movable joints (elbow
and knee)
– Lined with a lubricating fluid-secreting membranes
• Secrete a lubricating fluid that reduces friction as the bones move across
one another
OTHER CAVITIES
Medical Imaging
•
•
•
•
•
•
•
•
•
X-ray (radiograph)
CAT: Ccomputerized axial tomography
Xenon CT
DSR: Dynamic spatial reconstruction
DSA: Digital subtraction angiography
PET: Positron emission tomography
Sonography (ultrasound imaging)
MRI: Magnetic resonance imaging
MRS: Magnetic resonance spectroscopy
IMAGING