Copyright © 2010 Pearson Education, Inc. THE HUMAN BODY: AN ORIENTATION CH. 1A.

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THE HUMAN BODY: AN ORIENTATION CH. 1A

Overview of Anatomy and Physiology

• Anatomy: Study of the structure/parts

• Physiology: The study of function at many levels

• Function always reflects structure; What a structure can do depends on its specific form

Levels of Structural Organization

• Chemical: atoms and molecules

• Cellular: cells and their organelles

• Tissue: groups of similar cells

• Organ: contains two or more types of tissues

• Organ system: organs that work closely together

• Organismal: all organ systems

Cardiovascularsystem

OrganelleMoleculeAtoms

Chemical level Cellular level

Tissue levelTissues consist of similartypes of cells.

Organ levelOrgans are made up of different typesof tissues.

Organ system levelOrgan systems consist of differentorgans that work together closely.

Organismal levelThe human organism is made upof many organ systems.

Smooth muscle cell

Smooth muscle tissue

Connective tissue

Blood vessel (organ)

HeartBloodvessels

Epithelialtissue

Smooth muscle tissue

Figure 1.1

Homeostasis

• Definition: Maintenance of a relatively stable internal environment despite continuous outside changes

• Homeostasis is maintained by homeostatic control mechanisms which involve at least three components: receptor, control center, effector

Components of a Homeostatic Control Mechanism

1. Receptor (sensor)

• Monitors the environment and senses stimuli

2. Control center

• Receives input from receptor

• Determines the set point at which the variable is maintained

• Determines appropriate response

3. Effector

• Receives output from control center

• Provides the means to respond

• Response acts to reduce or enhance the stimulus (feedback)

Stimulusproduceschange invariable.

Receptordetectschange.

Input: Informationsent along afferentpathway to controlcenter.

Output:Information sent alongefferent pathway toeffector.

Responseof effectorfeeds backto reducethe effect ofstimulusand returnsvariable tohomeostaticlevel.

Receptor Effector

ControlCenter

BALANCE

Afferentpathway

Efferentpathway

IMBALANCE

Figure 1.4

Negative Feedback

•When the response of a control mechanism reduces or shuts off/stops the original stimulus, this is called negative feedback

• Example:

• Regulation of body temperature

Sweat glands activated

Shiveringbegins

StimulusBody temperaturerises BALANCE

Information sentalong the afferentpathway to controlcenter

Afferentpathway

Efferentpathway

Information sentalong the efferentpathway toeffectors

Information sentalong the efferentpathway to effectors

StimulusBody temperature falls

ReceptorsTemperature-sensitivecells in skin and brain

EffectorsSweat glands

EffectorsSkeletal muscles

Control Center(thermoregulatory

center in brain)

Control Center(thermoregulatory

center in brain)

ResponseEvaporation of sweatBody temperature falls;stimulus ends

ResponseBody temperature rises;stimulus ends

Positive Feedback

•When the response of a control mechanism enhances or exaggerates the original stimulus, this is called positive feedback

• Example:

• Enhancement of labor contractions by oxytocin

Anatomical Position

• Purpose:

• Standard anatomical body position:

• Body erect

• Feet slightly apart

• Palms facing forward

Cervical

(a) Anterior/Ventral

OrbitalNasalOral

ThoracicAxillary

SternalAbdominalUmbilicalPelvicInguinal

Upper limbAcromialBrachial (arm)AntecubitalAntebrachial (forearm)Carpal (wrist)

Digital

Lower limbCoxal (hip)Femoral (thigh)PatellarCrural (leg)Fibular

Tarsal (ankle)ThoraxAbdomenBack (Dorsum)

Cervical Back (dorsal)

(b) Posterior/Dorsal

Scapular Vertebral Lumbar Sacral Gluteal

Upper limb AcromialBrachial (arm) Olecranal

Digital

Femoral (thigh) Popliteal Sural (calf) Fibular

Calcaneal Plantar

Cephalic

Occipital (back of head)

Body Planes and Sections

• Sagittal plane

• Divides body vertically into right and left parts

• Produces a sagittal section

• Midsagittal (median) plane

• Lies on midline

• Parasagittal plane

• Not on midline

Body Planes

• Frontal (coronal) plane

• Divides body vertically into anterior and posterior parts

• Transverse (horizontal) plane

• Divides body horizontally into superior and inferior parts

• Produces a cross section

Transverse plane

Median (midsagittal) plane

Frontal plane

Spleen

Pancreas

Vertebralcolumn

Spinal cord

Subcutaneous fat layerBody wall

Rectum IntestinesLeft andright lungs

Liver HeartStomach

SpleenArm

(a) Frontal section (through torso)

(b) Transverse section (through torso, inferior view)

(c) Median section (midsagittal)

Body Cavities

• Two Large Cavities:

• Dorsal cavity encloses the CNS

• Two subdivisions:

• Cranial cavity

• Encases brain

• Vertebral cavity

• Encases spinal cord

Body Cavities

• Ventral cavity

• Houses soft internal organs (viscera)

• Two subdivisions (separated by diaphragm):

• Thoracic cavity

• Abdominopelvic cavity

Cranialcavity

Dorsalbodycavity

Vertebralcavity

Cranialcavity

Vertebralcavity

Abdomino-pelviccavity

Ventral bodycavity(thoracic andabdominopelviccavities)

Abdominal cavity(contains digestiveviscera)

Diaphragm

Pelvic cavity(contains urinary bladder, reproductive organs, and rectum)

ThoracicCavity

(a) Lateral view (b) Anterior view

Dorsal body cavityVentral body cavity

Ventral Body Cavities

• Thoracic cavity subdivisions:

• Two pleural cavities

• Each houses a lung

• Mediastinum

• Contains pericardial cavity

• Also contains the esophagus and aorta

• Pericardial cavity

• Encloses heart

Ventral Body Cavities

• Abdominopelvic cavity subdivisions:

• Abdominal cavity

• Contains stomach, intestines, spleen, and liver

• Pelvic cavity

• Contains urinary bladder, reproductive organs, and rectum

Cranialcavity

Dorsalbodycavity

Vertebralcavity

Cranialcavity

Vertebralcavity

Abdomino-pelviccavity

Ventral bodycavity

Abdominal cavity

Diaphragm

Pelvic cavity

Thoraciccavity

(a) Lateral view (b) Anterior view

Dorsal body cavityVentral body cavity

Epigastricregion

Umbilicalregion

Rightlumbarregion

Leftlumbarregion

Righthypochondriac

region

Lefthypochondriac

region

Hypogastric(pubic)region

Right iliac(inguinal)

region

Left iliac(inguinal)

region

Gallbladder

Ascending colon oflarge intestine

Small intestine

Appendix

Diaphragm

Stomach

Descending colonof large intestine

Transverse colonof large intestine

Initial part ofsigmoid colon

Urinary bladder

(a) Nine regions delineated by four planes (b) Anterior view of the nine regions showing the superficial organs

Nine Abdominopelvic Regions

Copyright © 2010 Pearson Education, Inc. THE HUMAN BODY: AN ORIENTATION CH. 1A.

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