INTRODUCTION

Chapter 1

Emily and Kaitlyn

The Human Body is the study of anatomy and physiology.  Anatomy is the structure of a part.  Physiology is the function of a part.  Anatomy and physiology are closely connected in that the structure of an organ suits its function.  Well, the structure of the body can be studied at different levels of the organization.   There are five levels: cells, tissue, organs, organ systems, and organisms.

         There are certain terms that are used to describe the location of the body parts, regions of the body and imaginary planes.  Anatomical is when the body is standing erect, with face forward, arms at the side and palms and toes directed forward.  These are some of the Directional Terms that are used to describe the location of the body part.  The human body can be divided into axial and appendicle portions.  The axial portion includes the ear, neck, and trunk.  Appendicle portion of the human body, which includes: the limbs.  To observe the structure of an internal body part, it is customary to section the body along a plane.  A plane is an imaginary flat surface passing through the body.  One of the three planes is a sagittal.  A sagittal plane extends lengthwise and divides the body into right and left portions.  The second is a frontal plane.  The frontal plane also extends lengthwise, but it is perpendicular to a sagittal plane and divides the body or an organ into anterior and posterior portions.  The third plane is the transverse.  Transverse plane is perpendicular to the body's long axis and therefore divides the body horizontally to produce a cross section. 

The Body Cavities and Membranes. First, the body is divided into two internal cavities, they are the following: the posterior body cavity and the anterior body cavity.  The posterior body cavity is subdivided into two parts: cranial cavity and vertebral canal.  The anterior body cavity is subdivided into the superior thoracic cavity and the inferior abdominopelvic cavity. 

         The final organization of the body in this chapter is about Homeostasis.  Homeostasis is the relative constancy of the body's internal environment.  Because of homeostasis, even though external conditions may change dramatically, internal conditions stay within a narrow range.  The negative feedback is the primary homeostatic mechanism that keeps a variable close to a particular value, or set point.  The homeostatic mechanism has three components: a sensor, a regulatory center, and effectors.  The positive feedback is a mechanism that brings about an even greater change in the same direction.  This can be harmful, as when a fever causes metabolic changes that push the fever still higher. 

These are some human systems that work together, which we just talked about.   

~Directions~

Definitions

A frontal plane divides the body into anterior and posterior planes.

Anterior:  a body part is located toward the front of the body.

Posterior:  A body part is located towards the back of the body.

A transverse plane cuts the body horizontally into superior and inferior planes.

Superior:  A body part is located above another body part.

Inferior:  A body part is below another.

A sagittal plane is a vertical cut dividing the body into left and right portions.


The body is divided into two internal cavities, then divided into many smaller cavities.

Homeostasis:  The relative constancy of the body’s internal environment.