What is the difference between directional and regional terms

The body maintains its internal organization by means of membranes, sheaths, and other structures that separate compartments.

The main cavities of the body include the cranial, thoracic and abdominopelvic also known as the peritoneal cavities. The cranial bones create the cranial cavity where the brain sits. The thoracic cavity is enclosed by the rib cage and contains the lungs and the heart, which is located in the mediastinum. Although no membrane physically divides the abdominopelvic cavity, it can be useful to distinguish between the abdominal cavity, the division that houses the digestive organs , and the pelvic cavity, the division that houses the organs of reproduction.

The more detailed regional approach subdivides the cavity with one horizontal line immediately inferior to the ribs and one immediately superior to the pelvis, and two vertical lines drawn as if dropped from the midpoint of each clavicle collarbone. There are nine resulting regions. Ancient Greek and Latin words are used to build anatomical terms. In which direction would an MRI scanner move to produce sequential images of the body in the frontal plane, and in which direction would an MRI scanner move to produce sequential images of the body in the sagittal plane?

Again, if the body were supine or prone, to produce sagittal sections, the scanner would move from left to right or from right to left to divide the body lengthwise into left and right portions. Skip to content Learning Objectives By the end of this section, you will be able to: Use appropriate anatomical terminology to identify key body structures, body regions, and directions in the body Demonstrate the anatomical position Describe the human body using directional and regional terms Identify three planes most commonly used in the study of anatomy Distinguish between major body cavities.

Figure 1. The regions of the body are labeled in boldface. Directional Terms Certain directional anatomical terms appear throughout this and any other anatomy textbook Figure 1. Anterior or ventral describes the front or direction toward the front of the body. The toes are anterior to the foot. Posterior or dorsal describes the back or direction toward the back of the body.

The popliteus is posterior to the patella. Superior or cranial describes a position above or higher than another part of the body proper.

The orbits are superior to the oris. Inferior or caudal describes a position below or lower than another part of the body proper; near or toward the tail in humans, the coccyx, or lowest part of the spinal column. The pelvis is inferior to the abdomen.

Lateral describes the side or direction toward the side of the body. Key Points Regional terms describe the different parts of the body by the structures and functions of a specific region.

The most basic regional terms are the axial and appendicular regions. Axes use directional terms to describe the location and orientation of a specific region. The directional term lateral is used to describe structures divided by a left-to-right axis. Key Terms ventral : On the front side of the human body or the corresponding surface of an animal, usually the lower surface.

Regional Terms in Anatomy Regional terms describe anatomy by dividing the parts of the body into different regions that contain structures that are involved in similar functions. Two primary terms are used to describe the main regions of the body: The Axial Region makes up the main axis of the human body and includes the head, neck, chest, and trunk.

The Appendicular Region makes up the parts of the human body that connect to the axial region. This includes the limbs and appendages. Axes Describe Relative Positions Another method for describing region An axis uses a straight line between two parts of the body to describe a region of the body with linear direction. Just as the brain and spinal cord make up a continuous, uninterrupted structure, the cranial and spinal cavities that house them are also continuous.

The brain and spinal cord are protected by the bones of the skull and vertebral column and by cerebrospinal fluid, a colorless fluid produced by the brain, which cushions the brain and spinal cord within the posterior dorsal cavity.

The anterior ventral cavity has two main subdivisions: the thoracic cavity and the abdominopelvic cavity see Figure 1. The thoracic cavity is the more superior subdivision of the anterior cavity, and it is enclosed by the rib cage.

The thoracic cavity contains the lungs and the heart, which is located in the mediastinum. The diaphragm forms the floor of the thoracic cavity and separates it from the more inferior abdominopelvic cavity.

The abdominopelvic cavity is the largest cavity in the body. Although no membrane physically divides the abdominopelvic cavity, it can be useful to distinguish between the abdominal cavity, the division that houses the digestive organs, and the pelvic cavity, the division that houses the organs of reproduction. The more detailed regional approach subdivides the cavity with one horizontal line immediately inferior to the ribs and one immediately superior to the pelvis, and two vertical lines drawn as if dropped from the midpoint of each clavicle collarbone.

There are nine resulting regions. A serous membrane also referred to a serosa is one of the thin membranes that cover the walls and organs in the thoracic and abdominopelvic cavities.

The parietal layers of the membranes line the walls of the body cavity pariet- refers to a cavity wall. The visceral layer of the membrane covers the organs the viscera.

Between the parietal and visceral layers is a very thin, fluid-filled serous space, or cavity Figure 1. There are three serous cavities and their associated membranes. The pleura is the serous membrane that encloses the pleural cavity; the pleural cavity surrounds the lungs. The pericardium is the serous membrane that encloses the pericardial cavity; the pericardial cavity surrounds the heart. The peritoneum is the serous membrane that encloses the peritoneal cavity; the peritoneal cavity surrounds several organs in the abdominopelvic cavity.

The serous membranes form fluid-filled sacs, or cavities, that are meant to cushion and reduce friction on internal organs when they move, such as when the lungs inflate or the heart beats.

Both the parietal and visceral serosa secrete the thin, slippery serous fluid located within the serous cavities. The pleural cavity reduces friction between the lungs and the body wall.

Likewise, the pericardial cavity reduces friction between the heart and the wall of the pericardium. The peritoneal cavity reduces friction between the abdominal and pelvic organs and the body wall.

Therefore, serous membranes provide additional protection to the viscera they enclose by reducing friction that could lead to inflammation of the organs. As an Amazon Associate we earn from qualifying purchases. Want to cite, share, or modify this book?