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The Human Body:
An Orientation
Overview of Anatomy and
Physiology
• Anatomy – the study of the
structure of body parts and their
relationships to one another
• How is it constructed?
Physiology
• Physiology – the study of the
function of the body’s structural
machinery or organ systems
• How does it work?
Levels of Structural Organization
• Chemical – atoms combined to
form molecules
• Cellular – cells are made of
molecules
• Tissue – consists of similar types
of cells
• Organ – made up of different
types of tissues
• Organ system – consists of
different organs that work closely
together
• Organismal – made up of the
organ systems
Levels of Structural Organization
Smooth muscle cell
Molecules
2 Cellular level
Cells are made up of molecules
Atoms
Smooth
muscle
tissue
3 Tissue level
Tissues consist of
similar types of
cells
1 Chemical level
Atoms combine to
form molecules
Heart
Cardiovascular
system
Epithelial
tissue
Smooth
muscle
tissue
Connective
tissue
4 Organ level
Organs are made up of
different types of tissues
Blood
vessels
Blood
vessel
(organ)
6 Organismal level
The human organism is
made up of many organ
systems
5 Organ system level
Organ systems consist of different organs
that work together closely
Figure 1.1
Orientation
• Orientation is the position of something
relative to some point.
• The human body is oriented into
–
–
–
–
–
–
–
Directions
Landmarks
Planes
Cavities
Quadrants
Regions
Systems
Directional Terms
• Superior or cranial
toward the head end of the body; upper
(example, the hand is part of the
superior extremity).
Inferior or caudal
away from the head; lower (example,
the foot is part of the inferior
extremity).
• Anterior or ventral
front (example, the kneecap is located
on the anterior side of the leg).
• Posterior or dorsal
back (example, the shoulder blades are
located on the posterior side of the
body).
• Medial
toward the midline of the body
(example, the middle toe is located at
the medial side of the foot).
• Lateral
away from the midline of the body
(example, the little toe is located at the
lateral side of the foot).
• Proximal
toward or nearest the trunk or the point
of origin of a part (example, the
proximal end of the femur joins with
the pelvic bone).
• Distal
away from or farthest from the trunk or
the point or origin of a part (example,
the hand is located at the distal end of
the forearm).
• Superficial
toward the surface
• Deep
away from the surface
• Cephalad
toward the head
• Caudal
toward the tailbone
Figure 1.9
Anatomical Landmarks
• See page 4 for anterior and
posterior landmarks.
• Record those landmarks on the
handout provided.
Body Cavities
• Body cavities are internal chambers
holding vital organs
– Cavities protect vital organs
– Cavities allow organs to change in shape
and size
• Two body cavities
– Dorsal body cavity includes the
cranial cavity and the spinal cavity
– Ventral body cavity includes the
thoracic cavity and the
abdominopelvic cavity
Abdominopelvic Cavity
• The abdominopelvic cavity is lined by
the peritoneum
– The abdominal cavity extends from the
diaphragm to the superior margins of the
pelvis
• liver, stomach, spleen and most of the large
intestine
Abdominopelvic Cavity
– The pelvic cavity is bordered by the
pelvis, with a floor of muscle
• reproductive organs, urinary bladder
and the final portion of the large
intestine
Abdominopelvic Regions
Prefixes, Suffixes, and Roots
•
•
•
•
epi- upon, above
hypo – below
gastric – stomach
iliac – superior part of
the hip bone
• chondro – cartilage
• lumbus – loin
• umbilicus - navel
Decipher the following
words:
1. Hypochondriac
2. Epigastric
3. Hypogastric
Body Systems
• See the handout that describes the
11 body systems.
• Learn the function and organs
found in each system.
Organ Systems Interrelationships
• Organ systems work together to
carry necessary life functions.
• For example
– Digestive and respiratory systems, in
contact with the external
environment, take in nutrients and
oxygen
Necessary Life Functions
• Maintaining boundaries – the
internal environment remains
distinct from the external
– Cellular level – accomplished by
plasma membranes
– Organismal level – accomplished by
the skin
• Movement – locomotion,
propulsion (peristalsis), and
contractility
• Responsiveness – ability to sense
changes in the environment and
respond to them
• Digestion – breakdown of ingested
foodstuffs
• Metabolism – all the chemical
reactions that occur in the body
• Excretion – removal of wastes from the
body
• Reproduction – cellular and organismal
levels
– Cellular – an original cell divides and
produces two identical daughter cells
– Organismal – sperm and egg unite to
make a whole new person
• Growth – increase in size of a body
part or of the organism
Homeostasis
• Homeostasis is the ability to
maintain a relatively stable internal
environment in an ever-changing
outside world
• The internal environment of the
body is in a dynamic state of
equilibrium
• The nervous system and the
endocrine system work together to
maintain homeostasis.
Homeostatic Control
Mechanisms
• The variable produces a change in
the body
• The three interdependent
components of control mechanisms
are:
– Receptor – monitors the
environments and responds to
changes (stimuli)
– Control center – determines the set
point at which the variable is
maintained
– Effector – provides the means to
respond to the stimulus
Homeostatic Control Mechanisms
3 Input:
Information
sent along
afferent
pathway to
Control
center
4 Output:
Information sent
along efferent
pathway to
Effector
Receptor (sensor)
2 Change
detected
by receptor
1
5 Response of
effector feeds
back to influence
magnitude of
stimulus and
returns
variable to
homeostasis
Stimulus:
Produces
change
in variable
Variable (in homeostasis)
Figure 1.4
Negative Feedback
• In negative feedback systems, the
output shuts off the original
stimulus
• Example: Regulation of blood
glucose levels
Negative Feedback
Figure 1.5
Positive Feedback
• In positive
feedback
systems, the
output enhances
or exaggerates
the original
stimulus
• Example:
Regulation of
blood clotting
Figure 1.6
Homeostatic Imbalance
• Disturbance of homeostasis or the
body’s normal equilibrium
• Overwhelming of negative
feedback mechanisms allowing
destructive positive feedback
mechanisms to take over