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The Human Body
An Overview
A. ANATOMY
• From Latin tomy (to cut) and ana (apart)
• It’s the study of structure and shape of the body
and its parts
• Two types:
– Gross anatomy: large structures, easily observable
– Microscopic anatomy: small structures only visible
with microscope
Gross Anatomy
Microscopic anatomy
B. LEVELS OF STRUCTURAL ORGANIZATION
• Structural complexity
Six levels of complexity
o Chemical level
Atoms: smallest building blocks of matter
Molecules: combinations of atoms to make
water, sugars, and proteins
- Atoms combine to form molecules
Nitrogen
o Cellular level
Molecules combine to form cells, which
vary in size and shape, reflecting different
functions of body
o Tissue level
Similar types of cells group to form tissues
- Four basic tissue types:
> Epithelial tissue (skin, membranes)
> Connective tissue (tendons, cartilage, ligaments and
bone)
> Muscular tissue (muscles)
> Neural tissue (spinal cord, brain matter)
o Organ level
Tissue or multiple tissues that form a structure
that performs a specific function
- Ex: small intestine is made out of all four tissue
types
o Organ system level
Group of organs that cooperate to accomplish a
common purpose
- Ex: digestive system includes esophagus, stomach, small
and large intestines, and more
Total of 11 organ systems
- How they work = physiology!
o Organismal level
Highest level of organization
- Human organisms have similar organ systems
and chimpanzees, but very different organ
systems than mosquitoes
C. PHYSIOLOGY
• Studies functions (how it works) of human
body and its parts
– Anatomists observe structures while
physiologists employ experimentation
• Organ systems
Integumentary system
o External covering of the body (skin)
Protects deeper tissue from injury
or infection
Synthesizes vitamin D
excretes salts and urea in
perspiration
helps regulate body temperature
contains pain, temperature, and
pressure receptors for
environmental cues
Muscular system
o Muscles of body
Contract or shorten to move
skeleton
Maintains posture
Produces heat
Skeletal system
o All bones, cartilages, ligaments and
joints make up skeletal system
Protects and supports body
organs
Provides muscle attachment for
movement
Forms blood cells (hematopoiesis)
in bone marrow
Provides and stores minerals
Nervous system
o Brain, spinal cord, nerves, and sensory
receptors
Speedy control system that responds
to external stimuli
– Light
– Sound
– Temperature changes
– Pain
– Pressure
Central nervous system (brain and
spinal cord) assesses information and
responds by activating appropriate
effector (muscles or glands)
Endocrine system
o A series of glands that slowly
control body by producing and
releasing hormones for growth,
metabolism, and reproduction
 Pituitary gland
 Thyroid gland
 Parathyroid glands
 Adrenal glands
 Thymus
 Pancreas
 Pineal gland
 Ovaries (females)
 Testes (males)
Cardiovascular system
o Heart and blood vessels
Work together to transport
materials in blood
– Nutrients
– Hormones
– Oxygen
– Carbon dioxide
– Waste
Lymphatic system
o Lymphatic vessels, lymph nodes,
spleen, and tonsils
Returns fluid leaked from blood
back to blood vessels
Lymph nodes (and others) help
cleanse blood and store cells
involved in immunity
Respiratory system
o Lungs, nasal passages, pharynx,
larynx, trachea, and bronchi
Supplies oxygen
Removes carbon dioxide
Digestive system
o Mouth, esophagus, stomach, small
and large intestines, liver, pancreas,
and rectum
Breaks down food
Deliver products to blood for
dispersal to body
– Undigested food leaves body
through anus as feces
Reclaim water for bodily use
Urinary(excretory) system
o Kidneys, ureters, bladder, urethra
Rids body of waste products
– Nitrogen-containing urea and
uric acid from breakdown of
proteins and nucleic acids
Maintains body’s water and
salt/electrolyte balance
Regulates acid-base balance of
blood
Reproductive system
o Males: scrotum, penis, accessory glands, and ducts
o Females: ovaries, uterine tubes, uterus, and vagina
Sole purpose is to produce offspring
Major Organs
D.LIFE FUNCTIONS
• Organ systems work together to promote health
and well-being of entire body. Must be able to
provide eight functions necessary for living. A
healthy body must …
HINT: these are all VERBS!
• Maintain boundaries
The “inside” remains distinct from the
“outside.”
o Examples include
a cell’s environment maintained by the cell
membrane
the integumentary system protecting organs from
desiccating (drying out), from bacteria and
viruses, from heat and sunlight, and from
chemicals
• Move
Muscle movement is necessary for
o Locomotion: getting us from one place to another, or
for moving muscle for safety (hot stove)
o Movement of substances: getting blood, food, and urine
through their proper organs
•Respond or be irritated
Ability to sense changes (from stimuli) and
react to them
oEx: is automatically removing hand from broken
glass (painful stimulus) that cuts – involuntary
response
oEx: when decrease in oxygen levels detected
(mountains), response is to increase breathing rate to
obtain more oxygen
• Digest
Breakdown of nutrients and absorption into
blood for delivery to all body cells
• Metabolize
Chemical reactions within body cells to
oProduce energy in form of ATP (adenosine
triphosphate)
oMake body structures like bones and muscles
Regulated mainly by hormones secreted by
glands of endocrine system
• Excrete
Eliminate excreta (waste) from digestions and
metabolic reactions
• Reproduce
Produce future generations…
o of
identical cells in cell division (repair or
growth)
o of entire organism
• Grow
Increasing cell size and number
o
Must make more cells faster than cells die
HINT: these are all NOUNS!
E. SURVIVAL NEEDS
• In order to maintain the eight functions for living,
the human body must have the following items:
Nutrients
oChemicals for energy and cell building
Carbohydrates
Proteins
Lipids
Vitamins
Minerals
Oxygen
oRequired for chemical reactions
Cellular respiration
Water
60-80% of body
weight
o Necessary for
metabolic reactions
o
Basal body temperature
o 98.6°F or 37°C
Atmospheric pressure
o Standard atmospheric pressure (on earth at
sea level is 760 mmHg or 29.92 inHg)
F. HOMEOSTASIS
• Maintenance of a stable internal environment = a
dynamic state of equilibrium
• Homeostasis must be maintained for normal body
functioning and to sustain life
When needs are being adequately met, body is
functioning smoothly, body demonstrates homeostasis
All organ systems partake in maintaining homeostasis
• Homeostatic imbalance – a disturbance in
homeostasis sets off chain reaction of events
Stimulus
o Produces change in variable
Detection
o Change is detected by receptor
Input
o Information is sent from receptor to control center
Output
o Control center decides what action or response should
be taken
Response
o Action or response feeds back to influence magnitude
of stimulus and returns variable to homeostasis
Overview of Homeostasis
• The body communicates chiefly through
nervous and endocrine systems
Nervous uses electrical signals delivered by
nerves
Endocrine system uses blood borne hormones
• Factor being regulated is called the variable
• All homeostatic control mechanisms have at least
three components
Receptor
o Responds to changes in the environment (stimuli)
o Sends information to control center via afferent pathway
 Afferent approaches control center
Control center
o Determines set point at which variable should be maintained
o Analyzes information
o Determines appropriate response
Effector
o Provides a means for response to the stimulus
o Desired response flows along efferent pathway
 Efferent exits control center
• Most homeostatic control mechanisms are negative
feedback mechanisms
Negative feedback
oIncludes most homeostatic control mechanisms
oShuts off the original stimulus, or reduces its intensity
oWorks like a household heating system with set point
of 72°F
If it’s too cold, will heat it up by turning on heater
If it’s too warm, will shut off heater until it levels
off
o Hypothalamus, located in brain, regulates
body temperature
• If stimulus produces desired effect, and body needs it to
increase in action, a positive feedback results
Positive feedback
oIncreases the original stimulus to push the variable
even farther away from set point
oIn the body this only occurs in blood clotting, birth of
a baby, and protein digestion
 Cut on hand = stimulus (wasn’t there prior and is not part
of body set-point)
 Factor in blood starts to form blood clots
 Body wants MORE blood clots so positive feedback
mechanism takes over
- MORE blood clotting factors are in play until wound
heals
• Homeostasis is SO important that most disease is a
result of homeostatic imbalance
As we age, body organs become less efficient, and
internal conditions less stable
oEvents put us at increased risk for illness and
produce changes associated with aging
Ex: elastin in connective tissue of skin makes it
able to resume shape after stretching, like a
rubber band
- As we age, elastin production decreases
and/or breaks down, so skin loses ability to
resume shape
G. ANATOMICAL LANGUAGE
• Can’t always describe body as left and right or top
and bottom because so many protrusions and
bends. Have specific terminology to describe
locations of the body.
• Exact terms are used for
Positions
Directions
Regions
Structures
Positions
o Initial point of reference is always the
standard position called anatomical
position regardless of position body
happens to be in (like sitting)
Body standing erect
Feet parallel
Arms hanging at sides, palms facing
forward
o Two major positions:
Anterior – front of body in anatomical
position
Posterior – back of body in
anatomical position
Regions
o Anterior body
landmarks
See page 13 of book
(don’t need to know
for test)
o Posterior body
landmarks
 See page 13 of book
(don’t need to know for
test)
Directions
opposites
opposites
opposites
o Used to describe body structure is in relation to
another.
Superior – toward head
Inferior – away from head; below
Anterior – toward or at front; in front of
Posterior – toward or at back; behind
Medial – toward or at midline
Lateral – away from midline
Intermediate – between a more medial and more
lateral structure
opposites
opposites opposites
 Proximal – close to origin of body part or point
of attachment of a limb to the body trunk
 Distal – farther from origin of a body part or
point of attachment of a limb to the body trunk
 Superficial – toward or at body surface
 Deep – away from body surface; more internal
 Supine – lying face upwards
 Prone – lying face down
Structures
o Planes and
sections
 Midsagittal
 Frontal
 Transverse
o Body cavities