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The Human BodyAn 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 complexitySix levels of complexity
o Chemical levelAtoms: smallest building blocks of matterMolecules: combinations of atoms to
make water, sugars, and proteins Atoms combine to form molecules
Nitrogen
oCellular levelMolecules combine to form cells,
which vary in size and shape, reflecting different functions of body
o Tissue levelSimilar 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 levelTissue 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 levelGroup of organs that cooperate to
accomplish a common purpose Ex: digestive system includes esophagus,
stomach, small and large intestines, and moreTotal of 11 organ systems How they work = physiology!
o Organismal levelHighest 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 systemsIntegumentary 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 systemoMuscles of body
Contract or shorten to move skeleton
Maintains postureProduces heat
Skeletal systemoAll bones, cartilages, ligaments
and joints make up skeletal systemProtects and supports body
organsProvides muscle attachment
for movementForms blood cells
(hematopoiesis) in bone marrow
Provides and stores minerals
Nervous systemoBrain, spinal cord, nerves, and
sensory receptorsSpeedy 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 systemoA series of glands that
slowly control body by producing and releasing hormones for growth, metabolism, and reproductionPituitary glandThyroid glandParathyroid glandsAdrenal glandsThymusPancreasPineal glandOvaries (females)Testes (males)
Cardiovascular systemoHeart and blood vessels
Work together to transport materials in blood
–Nutrients–Hormones–Oxygen–Carbon dioxide–Waste
Lymphatic systemo 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 systemoLungs, nasal passages,
pharynx, larynx, trachea, and bronchiSupplies oxygenRemoves carbon dioxide
Digestive systemoMouth, esophagus, stomach,
small and large intestines, liver, pancreas, and rectumBreaks down foodDeliver products to blood
for dispersal to body–Undigested food leaves
body through anus as feces
Reclaim water for bodily use
Urinary(excretory) systemoKidneys, ureters, bladder,
urethraRids 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 systemoMales: scrotum, penis, accessory glands, and ductsoFemales: 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 boundariesThe “inside” remains distinct from
the “outside.” oExamples 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
•MoveMuscle movement is necessary for
o Locomotion: getting us from one place to another, or for moving muscle for safety (hot stove)
oMovement of substances: getting blood, food, and urine through their proper organs
•Respond or be irritatedAbility to sense changes (from
stimuli) and react to themoEx: 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
•MetabolizeChemical reactions within body cells to
oProduce energy in form of ATP (adenosine triphosphate)
oMake body structures like bones and musclesRegulated mainly by hormones secreted
by glands of endocrine system
•ExcreteEliminate excreta (waste) from
digestions and metabolic reactionsUrineFeces
•ReproduceProduce future generations…
oof identical cells in cell division (repair or growth)
oof entire organism
•GrowIncreasing cell size and number
o Must make more cells faster than cells die
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 buildingCarbohydratesProteinsLipidsVitaminsMinerals
HINT: these are all NOUNS!
OxygenoRequired for chemical reactionsCellular respiration
Watero 60-80% of body weight
o Necessary for metabolic reactions
Basal body temperatureo 98.6°F or 37°C
Atmospheric pressureo 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 lifeWhen 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
StimulusoProduces change in variable
DetectionoChange is detected by receptor
Inputo Information is sent from receptor to control
center
OutputoControl center decides what action or
response should be taken
ResponseoAction 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 systemsNervous uses electrical signals delivered by
nervesEndocrine system uses blood borne hormones
• Factor being regulated is called the variable
• All homeostatic control mechanisms have at least three componentsReceptor
oResponds to changes in the environment (stimuli)oSends information to control center via afferent
pathway Afferent approaches control center
Control centeroDetermines set point at which variable should be
maintainedoAnalyzes informationoDetermines appropriate response
EffectoroProvides a means for response to the stimulusoDesired response flows along efferent pathway
Efferent exits control center
• Most homeostatic control mechanisms are negative feedback mechanismsNegative 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°FIf it’s too cold, will heat it up by turning
on heaterIf it’s too warm, will shut off heater until
it levels off
oHypothalamus, located in brain, regulates body temperature
• If stimulus produces desired effect, and body needs it to increase in action, a positive feedback resultsPositive 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, breastfeeding, 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 clotsBody 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 imbalanceAs we age, body organs become less efficient,
and internal conditions less stableoEvents put us at increased risk for illness
and produce changes associated with agingEx: 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 PositionsDirectionsRegionsStructures
Positionso Initial point of reference is
always the standard position called anatomical position regardless of position body happens to be in (like sitting)Body standing erectFeet parallelArms hanging at sides, palms
facing forwardo Two major positions:
Anterior – front of body in anatomical position
Posterior – back of body in anatomical position
RegionsoAnterior body
landmarksSee 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)
DirectionsoUsed to describe body structure is in
relation to another.Superior – toward headInferior – away from head; belowAnterior – toward or at front; in front ofPosterior – toward or at back; behindMedial – toward or at midlineLateral – away from midlineIntermediate – between a more medial
and more lateral structure
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
Structureso Planes and
sectionsMidsagitt
alFrontalTransvers
e
o Body cavities
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