Biology 211
Anatomy & Physiology I
Dr. Thompson
Orientation to the Human Body
Throughout this course, we will focus on three "major
concepts" which are central to the understanding of
anatomy and physiology:
a) Adaptation of anatomical structures to carry out specific
physiological functions
b) A "structural heirarchy" in both anatomy and
physiology, from atoms to the entire organism.
c) Homeostasis maintained by feedback mechanisms
First major concept: All complex animals share a
number of basic physiological functions for which
anatomical structures are specifically adapted, including:
- Protection of internal body environment from external
environment
- Maintenance of stable internal environment
- Responsiveness
- Ingestion, digestion, elimination
- Metabolism
- Excretion
- Reproduction
Each function is divided among many systems
and
Each system has multiple functions
Second major concept: The structures and functions of
all complex animals are based on a “structural heirarchy”
These are interdependent.
Abnormalilties at one level
will affect all higher levels
Example #1:
Your body consists of trillions of cells of at least 400
different types
About a dozen types: Lymphocytes
One type of lymphocyte: CD4 cell
Suppose a virus attacks and destroys your CD4 cells,
while all other cells (including all other lymphocytes)
remain healthy.
Example #2:
Your body consists of trillions of cells of at least 400
different types
Four types found in pancreatic islets
One type of islet cell: beta cell, which
produces insulin
Suppose your body attacks and destroys the beta cells,
while all other cells (including other islet cells) remain
healthy.
Example #3:
Your body consists of trillions of cells of at least 400
different types
One type of cell in nervous
system: oligodendrocyte
Oligodendrocytes: dozens of organelles
One organelle: plasma membrane
Plasma membrane: hundreds of types of
molecules. One type of molecule: myelin
Suppose your body attacks and damages the plasma
membranes of oligodendrocytes so they can’t properly
produce myelin, while all other organelles of these cells
and all other cells remain healthy.
Third major concept: Homeostasis:
A state of "dynamic (changing) equilibrium (balance)" in
which the body's internal environment is maintained within
narrow limits even when the external environment changes
significantly.
For example: You must maintain a steady internal body
temperature of approximately 37oC even if the external
temperature changes from -20oC to over 100oC.
Homeostasis requires communication among many
different organelles, cells, tissues, and organs
Homeostasis involves feedback mechanisms:
Positive Feedback: When a small change occurs, the
body responds by producing a greater change
in the same direction.
Allows rapid response and magnification
Examples: Blood clotting
Immunity
Negative Feedback: When a small change occurs, the
body responds by producing change in the
opposite direction.
Causes return to the original condition
Examples: Body temperature
Blood glucose concentration
Positive Feedback
Blood Clotting
The body responds to a
small clot by forming
an even larger clot
Negative Feedback: Temperature Regulation
The body responds to an increase in temperature by
decreasing the temperature, or
The body responds to a decrease in temperature by
increasing the temperature
Negative Feedback:
Eating increases blood glucose.
Concentration of glucose
in blood
Blood glucose stimulates
pancreatic islets to secrete insulin.
The body responds to
an increase in blood
glucose by lowering
its concentration, or
Insulin stimulates muscle cells and liver
cells to absorb glucose from blood.
Absorption of glucose by liver & muscle
lowers its concentration in blood.
This returns blood glucose to original
level
Fasting lowers blood glucose.
Negative Feedback:
Concentration of glucose
in blood
The body responds to
an increase in blood
glucose by lowering
its concentration, or
The body responds to a
decrease in blood
glucose by increasing
its concentration
Blood glucose stimulates
pancreatic islets to secrete glucagon.
Glucagon stimulates muscle cells
and liver cells to release glucose
back into blood.
Release of glucose by liver & muscle
increases its concentration in blood.
This returns blood glucose to original
level
Negative feedback is the mechanism your body uses to
keep literally thousands of things within “normal” limits
(homeostasis).
For example, in the blood:
Arterial pH
Bicarbonate
Sodium
Calcium
Oxygen
Urea
Amino acids
Protein
Total lipids
Glucose
7.35 - 7.43
21.3 - 28.5 mEq/L
136-151 mEq/L
4.6 - 5.2 mEq/L
17.2 - 22 ml / 100 ml
12 - 35 mg / 100 ml
3.3 - 5.1 mg / 100 ml
6.5 - 8 g / 100 ml
350 - 850 mg / 100 ml
75 - 110 mg / 100 ml
Next: A few basic concepts of anatomy
which we will use throughout this course
1) Planes or sections
2) Terms indicating relative positions
3) Regions of the body
4) Primary and secondary body cavities
5) Three-dimensional relationships
1) In discussing the organization of the human body and
its parts, we often establish our "point of view" according
to three planes or sections:
Horizontal
or Transverse
Plane
Coronal
or Frontal
Plane
Sagittal
Plane
How a structure appears depends on the plane in
which you view it:
2) In discussing parts of the human body, we also use a
number of terms of relative position:
Superior (cranial): Toward head or upper part of structure
Inferior (caudal): Toward sacrum or lower part of structure
Anterior (ventral): Toward the front
Posterior (dorsal): Toward the back
Medial: Toward the midline of the body or of a structure
Lateral: To side of midline of the body or of a structure
Proximal: Closer to center or origin
Distal:
Away from center or origin
Superficial: Toward the surface of the body or of a structure
Deep:
Toward the center of the body or of a structure
3) Various regions of body have specific names:
Anterior
Various parts of body have specific names:
Posterior
You should be able to identify the regions shown on these
diagrams.
For example: The region of the upper
limb between the
brachial region
shoulder and elbow is the_________
carpal region is immediately distal
For example: The _________
to the antebracheal region
4) Primary Body Cavities
(Formed by folding of the embryo)
Secondary Body Cavities
(Formed in place as organs develop)
Examples:
- Pericardial cavity around heart
- Pleural cavities around lungs
- Synovial cavities between bones
- Nasal cavity
- Oral cavity
- Orbital cavities
- External, Middle, and Inner ear cavities
5) Finally: As we discuss the human body, get your
brain to think three-dimensionally and focus on
relationships . . .