Anatomy – the study of the form or structure and arrangement of body parts and their relationships
Physiology – the study of the functions of the body parts or structures and their relationships in maintaining
Levels of Structural Organization
The human body consists of levels of structural organization that are associated with one another.
There are six levels of structural organization:
I. chemical level – It is the simplest level and it includes all of the chemical substances essential for maintaining life. These substances are made up of atoms.
An atom is the
smallest unit of matter. Matter is anything that takes up space and has mass. Atoms combine to form molecules, which may be simple or complex. Different types of molecules combine to form or~anelles (“little organs”). Organelles are specific structures that carry out specific functions.
2. cellular level – The cell is the basic unit of structure and function and of life. Cells vary in size, shape, and function and may contain many types of organelles.
3. tissue level – Tissues are groups of similar cells that
perform a specific function.
There are four major types of tissues in the human body:
epithelial tissue – It is found lining body
cavities and covers the surface of the body.
It functions in protection, secretion, and excretion.
b. connective tissue – It is found on the surfaces of and in organs and tissues and functions in protection, support, and attaching organs and tissues to each other and to the walls of body cavities.
c. muscle tissue – It functions in the movement of
body parts and organs, and in the movement of substances
throughout the body.
There are three major types of muscle tissue:
skeletal muscle – It is found attached to and
covering bones and it functions in body
cardiac muscle – It is located in the heart
wall and functions in the contraction and
relaxation of the heart as it beats.
smooth muscle – It is located in the walls of
internal or visceral organs and it functions
in moving substances throughout the body.
nervous tissue It is located in the brain and spinal cord, and extends to various tissues and organs. It functions in transmitting electrical or nerve impulses from the external and internal environments to the brain and spinal cord where it is interpreted and a response occurs.
4. organ level – Organs are groups of two or more types of tissue working together to perform a specific function.
5. organ system level – ~ sTstems are groups of organs
that work closely together to perform a common function.
There are eleven organ systems in the human body:
6. organismal level – It is the highest level of structural
organization and it consists of groups of organ systems working together to maintain body structure and function. Organ systems work together to maintain an internal environment that is fairly constant, stable, or balanced. This is referred to as homeostasis (“to stay the same”). Changes do occur, but within very narrow ranges or limits.
Body parts or structures function efficiently in maintaining metabolic processes and when the survival needs are within certain limits or optimum levels.
The survival needs include:
water, oxyqen, nutrients, an appropriate bod~ temperature, and atmospheric pressure. Water is necessary for chemical reactions, excretion, and secretion. Oxyqen is required for many of the metabolic reactions that break down nutrients and provide energy. Nutrients provide energy for cells and cell processes. Bod~ temperature must be maintained within a certain range for chemical reactions and cell processes to perform efficiently.
If the body temperature falls too low or increases too high, chemical reactions will slow down or may stop. Atmospheric pressure is the force of air on the body surface by the weight of air. It is important in breathing and in the exchange of oxygen and carbon dioxide in the lungs. To maintain homeostasis there are control mechanisms. Control mechanisms consist of three parts:
i. receptor – It responds to sensory stimuli
internal and external environments. The information is sent along afferent pathways to the control center.
2. control center – It consists of the brain and spinal cord which interpret and analyze the information and determine an appropriate response. Information is then sent along efferent
pathways to the effector.
3. effector – It consists of tissues, organs, or glands that perform a motor response to the original stimulus that was received by the receptor. The response involves a feedback mechanism. If the response slows down or inhibit~ the stimulus it is a neqative feedback mechanism. If the response speeds up or enhances the stimulus, it is a positive feedback mechanism.
mechanisms for homeostasis in the human body are negative feedback mechanisms.