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