CHAPTER 1

THE HUMAN BODY: AN ORIENTATION

Anatomy and Physiology are complementary sciences that allow one to study, classify, and understand body structures and functions.

Overview of Anatomy and Physiology

Anatomy the study of the structure and shape of the body and its parts and their relationship to one another.

Physiology the study of how the body and its parts work or function.

Relationship between Anatomy and Physiology

Anatomy and Physiology are always relatedParts of body are well organizedEach part has a job to do to make the body

operate as a wholeStructure determines what functions can take

place

Levels of Structural Organization

The human body has many levels of structural complexity

Atoms – building blocks of matter; combine to form many various molecules (water, sugar, proteins)

Cells – smallest units of all living thingsTissues – consist of groups of similar cells that

have a common function

Organ – structure composed of two or more tissue types that performs a specific function for the body.

Organ System – a group of organs that work together to accomplish a common purpose.

Organism – highest level of structural organization; sum total of all structural levels working together to keep us alive.

Organ System Overview

There are eleven organ systems that make up the human body.

Integumentary SystemThe external covering of the body (skin)Protection/waterproofing/regulate body temp

Skeletal SystemConsists of bones, cartilages, ligaments, jointsSupports body/provides framework for muscles

Muscular SystemAll movement relies on muscle contractionOnly includes skeletal muscles

Nervous SystemBody’s fast-acting control systemConsists of brain, spinal cord, nerves, and

sensory receptors Endocrine System

Controls the release of hormones through various glands in the body

Includes adrenals, pituitary, thyroid, pancreas, etc.

Cardiovascular SystemConsists of heart and all blood vesselsCarries oxygen, nutrients, hormones, and other

substances to body tissues in the blood Lymphatic System

Role is to complement the cardiovascular systemHelp to clean the blood and hold cells involved in

immunity Respiratory System

Keeps the body constantly supplied with oxygen and removes carbon dioxide

Consists of nasal passages, pharynx, larynx, trachea, bronchi, and lungs

Digestive SystemBreaks down food to deliver the nutrients to the

blood and removes any extra solid wasteIncludes mouth, esophagus, stomach, small/large

intestines, and other complimentary organs Urinary System

Removes the nitrogen-containing wastes from the break down of proteins

Composed of kidneys, ureters, bladder, and urethra

Reproductive SystemExists primarily to produce offspring and pass on

one’s genetic code to the next generation

Maintaining Life: Necessary Life Functions

Organ systems do not work in isolation; instead, they work together to promote the well-being of the entire body.

We will take a look at eight necessary functions of human life

Maintaining BoundariesInside remains distinct from outsideCellular membranes/Integumentary System

MovementIncludes all the activities promoted by the

musculo-skeletal systemAlso includes internal movement

○ Blood, food, waste

Responsiveness/IrritabilityThe ability to sense changes in the environment

and then react to themMajor responsibility of the nervous system

DigestionThe process of breaking down ingested food into

simple molecules that can then be absorbed into the blood

MetabolismBroad term that refers to all chemical reactions

that occur within body cellsDepends on digestive and respiratory systemRegulated chiefly by hormones secreted by the

endocrine system (Cortisol)

ExcretionThe process of removing wastes from the bodyUrine/feces

ReproductionProduction of offspring on cellular level as well as

organismal levelRegulated very precisely by hormones of the

endocrine system (testosterone/estrogen)

GrowthAn increase in sizeCell constructing activities must occur at a faster

rate than cell destroying activitiesHormones of the endocrine system play a large

role (HGH)

Survival Needs

The body requires certain things to maintain life Water Nutrients/Food Oxygen Normal Body Temperature Normal Atmospheric Pressure

WaterMakes up 60-80% of the human bodyThirst/Dehydration/Hyper-hydration

Nutrients/FoodNeeded for energy and cell buildingCarbohydrates/Proteins/Fats/Minerals/Vitamins

OxygenAll chemical reactions that release energy require

oxygen to be present Normal Body Temp/Atmospheric Conditions

Too Cold (Hypothermia)/Too Hot(Fever/Heat Stroke)High Altitude Sickness

Homeostasis

Homeostasis describes the body’s ability to maintain relatively stable internal conditions even though the outside world is continuously changing.State of equilibrium or balance minor things may

change, but the overall picture remains the sameVirtually all organ systems work together to

maintain homeostasis

Homeostatic Controls

Communication between organ systems is essential to maintaining homeostasis. This communication is accomplished mainly by the nervous (electrical signals) and endocrine systems (hormones).

All homeostatic control mechanisms have at least three components. 1. Receptor

Type of sensor that monitors and responds to changes in the environment (stimuli)

Sends this information to the next component 2. Control Center

Analyzes information received from receptor and determines the appropriate response

3. EffectorProvides the means for the control center’s

response

Negative Feedback MechanismsMajority of control mechanismsNet effect is to shut off the original stimulusThink of heating/AC system in a house

Positive Feedback MechanismsRare in the human bodyTypically control infrequent events that occur

explosively and do not require continuous adjustments

Blood Clotting in response to a cut

The Language of Anatomy

Just like most things, anatomy has its own terminology specifically designed to make it easier to identify body locations and regions.

In order to prevent too much confusion, a set of terms were created that allow body structures to be located and identified clearly with just a few words.

Anatomical Position

Before we can accurately describe body parts and position, we need a starting point to reference.

When using these terms, we will always assume the body is in its standard position.

Anatomical PositionStanding up straight, feet shoulder width apart and

parallel to one another, arms hanging at sides with palms facing forward.

Directional Terms

Directional Terms allows people to explain exactly where one body structure is in relation to another structure. (Table 1.1 page 15)

Superior – toward the head end of the body; aboveInferior – away from the head end; belowAnterior (Ventral) – toward the front of the bodyPosterior (Dorsal) – toward the backside of the bodyMedial – toward the midline of the body; inner sideLateral – away from the midline; outer side

Intermediate – between a more medial and more lateral structure

Proximal – close to the origin of the body part or the point of attachment of a limb to the body

Distal – farther from the origin of a body part or point of attachment of a limb to the body

Superficial (external) – toward the body surfaceDeep (internal) – away from the body surface

Body Planes and Sections

Plane an imaginary line through the body. Since the body is 3D, we can refer to three types of planes.

Sagittal – cut along lengthwise dividing the body into right and left parts

Frontal (Coronal) – cut along lengthwise dividing the body into anterior and posterior parts

Transverse – cut along horizontally dividing the body into superior and inferior parts. Also known as a cross-section.

Body Cavities Dorsal Body Cavity

Has two subdivisions○ Cranial cavity – space inside the skull○ Spinal Cavity – extends from cranial cavity to the end of

the vertebral column

Ventral Body CavityContains all the structures within the chest and

abdomen○ Thoracic Cavity – contains lungs, heart, etc○ Abdominal Cavity – contains stomach, liver, intestines, etc.○ Pelvic Cavity – reproductive organs, bladder