The Human Body: An Orientation

Chapter 1

Part 2

Maintaining Life

Necessary Life Functions

Survival Needs

Homeostasis

Necessary Life Functions• Maintaining Boundaries– Inside must be distinct

from outside• Movement– Locomotion– Movement of substances

• Responsiveness– AKA “irritability”– Ability to sense changes in

environment and respond• Digestion– Breakdown and delivery of

nutrients

• Metabolism– Chemical reactions

within body cells• Excretion– Removes wastes from

body and requires many organs

• Reproduction– Production of future

generation• Growth– Increasing of cell size

and number

Survival Needs

• Nutrients– Taken in via diet– Give energy and maintain cells– Chemicals for energy and cell building– Includes carbohydrates, proteins, lipids, vitamins, and

minerals

• Oxygen– Required for chemical reactions

Survival Needs (con’t)

• Water– Obtained through diet– Lose by evaporation from lungs, skin, and excretion– 60 – 80% of body weight– Provides for metabolic reactions

• Normal (stable) body temperature• Atmospheric pressure – must be appropriate

Homeostasis

Describes the ability to maintain relatively stable internal condition even though the

outside world changes continuously.

Indicates a dynamic state of equilibrium, or balance.

Homeostatic Control Mechanisms

• Communication in the body is accomplished chiefly by the nervous and endocrine systems.

• Variable – factor or event being regulated• Receptor – sensor that monitors the environment

and respond to changes• Control center – analyzes the input it receives and

then determines the appropriate response• Effector – provides a means for response to the

stimulus

Negative Feedback Mechanism

• The output of the system shuts off the original stimulus or reduces its intensity.

• This mechanism causes the variable to change in a direction opposite to that of the initial change, returning it to its “ideal” value.

• All negative feedback systems have the same goal: to prevent sudden severe changes.

Positive Feedback Mechanism

• The result of response enhances or exaggerates the original stimulus so that the activity is accelerated.

• “Positive” because the change occurs in the same direction as the initial disturbance, causing the variable to deviate further and further from the original value.

• Control infrequent events that don’t require continuous adjustments!!

The Language of Anatomy

Special terminology is used to prevent misunderstanding

• Exact terms are used for:

• Position

• Direction

• Regions

• Structures

Anatomical Position

• Anatomical reference point

• Body is erect with feet slightly apart

• “Standing at attention” pose

• Palms face forward and thumbs point away from body

Directional Terms

Allow us to explain exactly where one body structure is in relation to another.

Orientation and Directional TermsOrientation and Directional Terms

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Orientation and Directional TermsOrientation and Directional Terms

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Regional Terms

• Used to designate specific areas within the major body divisions.

• Two divisions:1. Axial part – head, neck, and trunk

2. Appendicular part – limbs

BodyBody

LandmarksLandmarks

Anterior

BodyBody

LandmarksLandmarks

Posterior

Body Planes

• Plane – flat surface• Most frequent body planes:– Sagittal Plane

• Vertical plane that divides body into right and left• Midsagittal – exactly on midline• Parasagittal – offset from midline

– Frontal Plane• Divides body into anterior and posterior• AKA “coronal” plane

– Transverse Plane• Horizontal plane• Divides into superior and inferior parts

Body Planes

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Body Cavities

Axial portion of the body:

Dorsal Body Cavity

• Protects nervous system• 2 Subdivisions:– Cranial cavity – encases brain– Vertebral cavity – encases spinal cord

Ventral Body Cavity

• 2 Subdivisions:– Thoracic cavity is subdivided into pleural cavities, the

mediastinum, and the pericardial cavity• Surrounds ribs and muscles• Pleural cavity – houses lungs• Pericardial cavity – houses hearts, esophagus and trachea• Mediastinum – contains the pericardial cavity, and surrounds

the remaining thoracic organs

Ventral Body Cavity

– 2 Subdivisions: (con’t)

– Abdominopelvic cavity• Separated from thoracic cavity by the dome-shaped diaphragm• It is composed of two subdivisions

– Abdominal cavity – contains stomach, intestines, spleen, and liver, and other organs

– Pelvic cavity – lies within the pelvis and the contains bladder, reproductive organs, and rectum

Membranes in the Ventral Body Cavity

• Serosa (serous membrane)– Thin, double-layered membrane– Parietal serosa – membrane lining cavity walls– Visceral serosa – covers organs

• Serous fluid– Separates serous membranes– Allows sliding without friction

Ventral Body Cavity MembranesVentral Body Cavity Membranes

• Parietal serosa covering the body walls

• Visceral serosa covering the internal organs

• Serous fluid separates the serosae

Other Body Cavities• Oral and digestive– Mouth and cavities of the digestive organs

• Nasal– Located within and posterior to the nose

• Orbital– House the eyes

• Middle ear– Contains bones (ossicles) that transmit sound

vibrations

• Synovial– Joint cavities

Abdominopelvic Regions • 1. Right Hypochondriac: Liver, gall bladder, small intestine,

ascending colon, transverse colon, right kidney • 2. Epigastric: Esophagus, stomach, liver, pancreas, small

intestine, transvers colon, right and left adrenal glands, pancreas, right and left kidneys, right and left ureters, spleen

• 3. Left Hypochondriac: Stomach, tip of liver, tail of pancreas, small intestines, transverse colon, descending colon, pancreas, left kidney, spleen

• 4. Right Lumbar: Tip of liver, gall bladder, small intestine, ascending colon, right kidney

• 5. Umbilical: Stomach, pancreas, small intestine, transverse colon, pancreas, right and left kidneys, right and left ureters

Abdominopelvic Regions (con’t)• 1. Right Hypochondriac: Liver, gall bladder, small intestine,

ascending colon, transverse colon, right kidney • 2. Epigastric: Esophagus, stomach, liver, pancreas, small

intestine, transvers colon, right and left adrenal glands, pancreas, right and left kidneys, right and left ureters, spleen

• 3. Left Hypochondriac: Stomach, tip of liver, tail of pancreas, small intestines, transverse colon, descending colon, pancreas, left kidney, spleen

• 4. Right Lumbar: Tip of liver, gall bladder, small intestine, ascending colon, right kidney

• 5. Umbilical: Stomach, pancreas, small intestine, transverse colon, pancreas, right and left kidneys, right and left ureters

Abdominopelvic Regions

Abdominopelvic Quadrants

• Quadrants are named according to subject’s pt. of view– Right upper– Left upper– Right lower– Left lower