AN INTRODUCTION TO THE HUMAN BODY
A.ANATOMY AND PHYSIOLOGY DEFINED
Anatomy (from the Greek “anatome” = to cut up, dissect)
What do you mean when you speak of the anatomy of the body?
You are referring to the study of structures and the relationships between structures.
Physiology (from the Greek “physis” = nature)
What do you mean when you speak of the physiology of the body?
You are referring to the functions of the body parts.
These two cannot be wholly separated?
Why not?
Structure usually determines function and, in turn, the function of a body part usually influences its size, shape, and overall health.
B.LEVELS OF STRUCTURAL ORGANIZATION
What are the six levels of structural organization of the human body? What comprises each level?
1.chemical level – lowest level; includes all atoms and molecules essential for maintaining life
2.cellular level – cells are the basic structural and functional units of life; formed from molecules and atoms
3.tissue level – tissues are groups of similar cell types and the extracellular matrix around them; cells work for a common function
4.organ level – organs are comprised of two or more different tissues; each organ has a specific function and shape
5.system level – consists of an association of related organs that have a common function
6.organismic level – highest level; all body parts are functioning together to comprise the individual
C.LIFE PROCESSES
All living forms carry on certain processes that distinguish them from nonliving things.
Can you list the six important life processes of humans?
metabolism
responsiveness (excitability, irritability)
movement
growth
differentiation
reproduction
What is metabolism?
Metabolism is the sum of all chemical processes in the body.
Metabolism can be broken down into two processes that contribute to the whole. Name them.
Catabolism – breaking-down processes that provide energy by breaking large molecules into their components parts
Anabolism – building up processes that use energy and raw materials to build and maintain the body’s structural and functional components
What is responsiveness (excitability, irritability)
Responsiveness is the ability to detect and respond to changes in the external and internal environments.
What roles do the nervous and endocrine systems have in this process?
The nervous and endocrine systems detect changes in the environment, then integrate and interpret those changes.
What roles do the muscles and glands have in this process?
Muscular and glandular tissues respond to input from the nervous and endocrine systems to elicit changes in the body to counteract changes in the environment.
What is movement and what does it include?
Movement includes motion of the whole body, individual organs, tissues, cells, or even organelles within cells.
What is growth and in what two ways can it occur?
Growth refers to an increase in size and complexity of an individual. It can occur as:
(1)an increase in the number and size of cells and as
(2)an increase in the amount of extracellular matrix between
cells, pushing the cells farther apart.
What is differentiation?
Differentiation is the process a cell undergoes as it moves developmentally from an unspecialized stage to a more specialized one.
What is reproduction?
Reproduction refers either to the formation of new cells for growth, repair, or replacement (mitosis), or to the production of a new individual (sexual).
D.ANATOMICAL POSITION
What is the anatomical position?
The subject stands upright facing the observer, with feet flat on the floor, arms at the sides, palms and eyes facing forward.
E.DIRECTIONAL TERMS
Why do we use directional terms?
Directional terms are used to discuss body parts in relation to one another.
What are the five most commonly used directional term pairs?
superior versus inferior
anterior (ventral) versus posterior (dorsal)
medial versus lateral
proximal versus distal
superficial versus deep
F.PLANES AND SECTIONS
What is a plane and how does it compare to a section?
A plane is an imaginary flat surface that passes through the body. A section is a two-dimensional surface resulting from a cut made through the three-dimensional structure along one of planes described below.
Can you list the four major planes of the body?
A sagittal plane is a vertical plane that divides a structure into right and left sides.
A frontal (coronal) plane divides the body or part into anterior (front) and posterior (back).
A transverse (horizontal or cross) plane divides the body or part into superior (top) and inferior (bottom) parts.
An oblique plane passes through the body or part at an angle between the transverse plane and the others.
What are the five sections you can make through the body or a body part?
midsagittal, parasagittal, transverse, frontal, oblique
G.BODY CAVITIES
What is a body cavity?
Body cavities are confined spaces within the body that separate internal organs and serve to protect, separate, and support the organs. There are two, dorsal and ventral.
Name the subdivisions of the dorsal cavity?
cranial cavity contains the brain
vertebral (spinal) cavity contains the spinal cord
Name the subdivisions of the ventral body cavity?
thoracic cavity contains the pleural cavities (lungs)
mediastinum
anterior
middle (pericardial cavity)
posterior
abdominopelvic
How is the ventral body cavity divided?
The abdominopelvic cavity is separated from the thoracic cavity by the muscular diaphragm.
An imaginary plane lying across the bony pelvis separates the abdomen and pelvis.
H.HOMEOSTASIS
Homeostasis: maintaining physiological limits
(Greek “homoi-“ = same, “stasis” = standing still
Define the term homeostasis.
A condition in which the body’s internal environment remains within certain physiological limits
What three conditions must be maintained at all times to ensure that a cell remains in homeostasis?
1.optimum levels of gases, ions, nutrients, water
2.optimum temperature
3.optimum pressure
Why must the fluid bathing body cells by precisely maintained?
For the cells of the body to live, the composition of their surrounding fluids must be precisely maintained at all times, since this is the fluid with which they exchange materials.
Define extracellular fluid and its two major components?
Extracellular fluid (ECF) is that fluid outside of cells:
1.Interstitial fluid (intercellular or tissue fluid) is that fluid filling the
narrow spaces between the cells.
2.Plasma is the fluid components of the blood
What is intracellular fluid?
Intracellular fluid is the fluid within cells.
Describe, then, why interstitial fluid is considered to be the internal environment.
There is constant movement of water and solutes between these three compartments. Because the interstitial fluid services the intracellular fluid, the interstitial fluid is said to be the internal environment.
1.REGULATION BY NERVOUS AND ENDOCRINE MECHANISMS
The combined effects of the nervous system and the endocrine system regulate the homeostatic responses of the body.
How does the nervous system operate to return the body to within normal limits?
The nervous system is the body’s rapid-response system, using electrical messages to counteract stress and return the body to within normal ranges.
How does the endocrine system operate to return the body to within normal limits?
The endocrine system is the body’s long-term regulator, using chemical messengers called hormones to maintain the body within normal ranges.
2.FEEDBACK SYSTEMS
Define the concept of a feedback system.
A feedback system (loop) is a cycle of events in which status of a condition is continuously monitored and information regarding the condition is fed back (reported) to a central control region. There are three basic components.
Name and describe the three components necessary for successful operation of a feedback system.
The control center determines the point at which some aspect of the body, called the controlled condition, should be maintained.
The receptor monitors changes in the controlled condition and then sends information, called the input, to the control center. Any stress that changes the controlled condition is called the stimulus.
The effector receives information, called the output, from the control center and produces a response. The response is continually monitored by the receptor and information is fed back to the control center.
Distinguish between negative and positive feedback.
In negative feedback, the response of the body reverses the original stimulus. These systems maintain conditions that require frequent monitoring and fine adjustment.
In positive feedback, the response of the body enhances the original stimulus. This type of control system is used much less frequently than negative feedback (blood clotting, childbirth, etc.)
Consider this example of negative feedback system for blood pressure control. Do not worry about the details of how blood pressure is controlled. We will cover this in great detail later. Think about the process.
Some stimulus, in this case one which causes an increase in blood pressure, disrupts the normal homeostatic range for blood pressure.
The controlled condition (blood pressure) is normally maintained at 120/70 in the adult. The stimulus has pushed the controlled condition out of the normal range.
In response to the increased blood pressure, pressure-sensitive receptors in certain arteries become stimulated and generate an electrical message that is transmitted to the control center. This information is input.
The control receives the input, integrates it with other inputs, and interprets its meaning. In response, it then generates a message, the output, to the effectors.
The effectors respond to the output by changing their physiological activities. In this case, the heart decreases its rate and the arterioles of the body vasodilate. As a result, blood pressure drops back into normal range.
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