Introduction to Anatomy & Physiology
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Anatomy looks at structure while physiology looks at function.
Since structure reflects function, and vice versa, anatomy and physiology
are intricately linked.
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To look at anatomy & physiology, it’s helpful to review some basic
biological ideas :
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Characteristics of life
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Metabolism
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Needs of life
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Homeostasis
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Levels of organization
Organization of the Human Body
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Body cavities : the body can be divided into axial (trunk)
and appendicular (appendages) portions. The axial portion can be
further divided into a dorsal (back) and ventral (belly)
cavity. The dorsal cavity includes two smaller cavities, the cranial
(brain)
and spinal cavities. The ventral cavity is further divided into
the thoracic (chest) and abdominopelvic (lower gut) cavities.
The abdominopelvic is divided into the pelvic cavity and the abdominal
cavity. The thoracic cavity has three divisions, two
pleural
(lung) cavities and the mediastinum (heart).
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Smaller body cavities include the oral (mouth), nasal (nose),
orbital
(eye), and the middle ear.
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Membranes : in the abdominopelvic and thoracic cavities, there are
two types of membrane (also called serosa):
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Parietal membranes attach to a cavity wall and line the cavity
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Visceral membranes surround the organs within a cavity.
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Parietal and visceral pleura are associated with the lungs
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Parietal and visceral perioteum are associated with
the intestines.
Assuming the Position
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The anatomical position is the position a body is in for dissection
– standing erect, face is forward, arms at the sides, palms forward.
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When using anatomical terminology, the body is assumed to be in the anatomical
position
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Relative terms :
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Superior/inferior : above/below. The heart is superior to
the diaphragm. The mouth is inferior to the nose.
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Anterior/posterior : front/back. The sternum is anterior
to the vertebrae. The gluteus maximus is posterior to the pubic symphysis.
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Dorsal/ventral : back/front. In humans, dorsal and posterior are
synonomous, as are ventral and anterior; this is because we stand upright.
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Medial/lateral : middle/sides. The nose is medial to the
eyes. The lungs are lateral to the trachea.
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Proximal/distal : close to the trunk/far away from the trunk. The
elbow is proximal to the wrist. The metatarsals are distal
to the patella.
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Superficial/deep : surface/deep inside. The epidermis is superficial
to the dermis. The pelvic cavity lymph nodes are deep to the inguineal
lymph nodes.
Maintaining Life : the characteristics of a living organism
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Maintain boundaries (separate internal and external environments)
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Movement (any function of the muscular system, or contractility of a cell)
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Responsiveness, or irritability (respond to environmental stimuli)
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Metabolism (all chemical reactions of an organism)
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Excretion (removal of wastes produced in digestion and metabolism)
Survival : maintaining that fragile state called life…
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Nutrients (containing the chemical substances used for energy and cell
building)
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Oxygen (for respiration)
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Water (the necessary environment for most bodily reactions)
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Stable body temperature (optimal enzyme temperature)
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Stable atmospheric pressure (for breathing and oxygen exchange)
Homeostasis : the stable internal environment inside us all
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It is a dynamic state of equilibrium
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Control mechanisms are constantly at work to keep the internal state stable
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Control mechanisms have three interdependent components :
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A receptor (sensor)
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A control center, or integration center
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An effector
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There are two types of control mechanisms :
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Negative feedback, which decreases or shuts off the original stimulus.
For example, if you are cold, you shiver in order to decrease the cold
stimulus.
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Positive feedback, which maintains or increases the original stimulus.
For example, once blood starts to clot in an area, the clotting mechanism
continues until the clot has formed; it will not stop halfway through the
process.
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Diseases are typically the results of a homeostatic imbalance.