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An Introduction to the Structure and Function of the Body
Chapter 1
o Anatomy- Derived from two Greek words that mean "a cutting up." Study of body parts of an organism, their relationships and function is called anatomy. o Dissection- The process of cutting the body apart. o Physiology- The study of the functions of living organisms and their parts. o Cytology- The study of structure, function and development of cell. o Disease- A condition of the body result from abnormalities of body structure or function that prevents the body from maintaining the internal stability that keeps us alive and healthy. o Pathology- The scientific study of disease. Structural Levels of Organization The body as a whole (organism) is a unit constructed of the following smaller units (from simple to complex): Atoms and molecules—chemical level of organization Cells—The smallest structural and functional unit of body; organizations of various chemicals that can live and reproduce independently. Tissues—An organization of group of cells of similar or different types that perform a common function. Organs—A group of several different kinds of tissues arranged so that they can act together as a unit to perform a special function. Systems—an organization of varying numbers and kinds of organs arranged so that they can together perform complex functions for the body.
Anatomical Position
The anatomical position is a reference position that gives meaning to the directional terms used to describe the body parts and regions. Reference position in which the body is standing erect with the feet slightly apart and arms at the sides with palms turned forward. The head also points forward, as do the feet, which are aligned at the toe and set slightly apart. Supine and prone are terms used to describe the position of the body when it is not in the anatomical position. In the supine position the body is lying on back and the face upward, and in the prone position the body is lying on chest and the face downward.
Anatomical Directions
The following directional terms are used in describing relative positions of body parts Superior and inferior : Superior means toward the head also means upper, above ; inferior means toward the feet, also means lower, below. For example, the lungs are located superior to the diaphragm, whereas the stomach is located inferior to the diaphragm Anterior and posterior : anterior means "front" or "in front of"; posterior means "back" or "in back of." Ventral ( toward the belly) can be used in place of anterior and dorsal (toward the back) can be used for posterior. For example, the nose is on the anterior surface of the body, and the shoulder blades are on its posterior surface.
image) called a midsagittal plane. Frontal —a frontal also referred to as coronal plane is a length wise plane running from side to side. A frontal plane divides the body or any of its parts into anterior and posterior (nose in the front from the back) portions. Transverse —a transverse plane is a horizontal or crosswise plane that divides the body or any of its parts into upper and lower portions.
Body Cavities
The two major body cavities are called the ventral (anterior) and dorsal (posterior) body cavities. A. Ventral cavity
- Thoracic cavity : The upper part of the ventral cavity includes the thoracic cavity or chest cavity. It is divided into a. Mediastinum—midportion of thoracic cavity (space between two lungs); heart with roots of great vessels and trachea located in mediastinum b.Pleural cavities— Pleura is a double layered covering of the lungs. Right lung located in right pleural cavity, left lung in left pleural cavity.
- Abdominopelvic cavity : The lower part of the ventral cavity includes an abdominal cavity and a pelvic cavity which is actually a single cavity knowns as the abdominopelvic cavity, because no physical partition separates them.
a. Abdominal cavity contains stomach, intestines, liver, gallbladder, pancreas, and spleen b.Pelvic cavity contains reproductive organs, urinary bladder, and lowest part of intestine The diaphragm separates the thoracic cavity from abdominopelvic cavity Abdominopelvic regions To make it easier to locate organs in the large abdominopelvic cavity, anatomists have divided the abdominopelvic cavity into four quadrants. The midsagittal and transverse planes pass through the navel (umbilicus) and divide the abdominopelvic region into these four quadrants- a. Right upper or superior b. Right lower or inferior c. Left upper or superior d.Left lower or inferior. The abdominopelvic cavity is also subdivided into nine regions defined as follows: Upper abdominopelvic regions—the right and left hypochondriac regions and the epigastric (above the stomach) region lie above an imaginary line across the abdomen at the level of the ninth rib cartilages. Middle regions—the right and left lumbar regions and the umbilical region lie below an imaginary line across the abdomen at the level of the ninth rib cartilages and above an imaginary line across the abdomen at the top of the hip bones. Lower regions—the right and left iliac (or inguinal) regions and the hypogastric ( (below the stomach) region lie below an imaginary line across the abdomen at the level of the top of the hip bones.
Homeostasis and Feedback loop
Homeostasis is what physiologists call the relative constancy of the internal environment. It is the ability of an organism to maintain its optimal internal environment by constantly responding to stimuli. The temperature, salt content, acid level (pH), fluid volume and pressure, oxygen concentration, and other vital conditions within the body must remain within acceptable limits to maintain homeostasis. Because the activities of cells and external disturbances are always shifting the conditions inside the body, fluctuations occur frequently. Therefore, the body must constantly work to maintain or restore stability, or homeostasis. Metabolism : A sum total of process required by an organism to grow, maintain and reproduction. To accomplish such self-regulation, a highly complex and integrated communication control system is required. The basic type of control system in the body is called a feedback loop. The body uses negative feedback loops and, less often, positive feedback loops to maintain or restore homeostasis Both feedback loops involve a sensor, a control center, and an effector. The sensor detects the change in the regulated condition and sends information to the control center, which responds by initiating certain changes that are then sent to the effector, which influences the controlled condition. The control center compares the present condition to the homeostatic condition the body is trying to maintain. For example: When you ride a bike, your eyes are the sensors, your brain is the
