PP 02Gross anatomy, terms of
direction, and sections/planes
Two Major
Divisions
of Nervous
System
(NS)
• CNS: Brain & Spinal Cord
– Protection by bony shell,
•
meninges, & CSF
PNS: Sensorimotor (Spinal/Cranial)
Nerves: Innervation of organs,
muscles, joints, & skin
– Somatic nervous system
– Autonomic nervous system (ANS)
• Sympathetic and
parasympathetic systems
CNS levels
• Cerebrum
– incl. basal
ganglia, limbic
system
• Diencephalon
(thalamus and
hypothalamus)
• Brainstem
– Midbrain, pons,
medulla
• Cerebellum
• Spinal cord
Terms of Direction: Overview
Terms of direction denote relative position of one
neurological structure to another
• Two systems of “higher, lower, more forward, more
backward”:
– System referenced to person standing in 3-D space
• Superior / inferior ; anterior / posterior
– System referenced to anatomical neuraxis, which is
straight in many animals, and curved in humans.
• Rostral / caudal; ventral / dorsal
• A system of “closer to the midline, farther from the
midline”
• Medial / lateral
• A system of “how close to the point of connection
with the body”
• Proximal / distal
First system of “higher, lower, more
forward, more backward”
– System
referenced
to human in
anatomical
position in
3D space
•Superior /
inferior ;
anterior /
posterior Human anatomical position =
Posterior
Superior
Anterior
Inferior
Body erect, hands at side,
palms facing outward
6- Superior
2- Inferior
1- Anterior
5- Posterior
When referring to
structures of the head as
superior to other
structures, the terms
cranial or cephalic are
sometimes used as terms
of direction
First system of “higher, lower, more
forward, more backward”
Examples:
• The brain is superior to the spinal
cord
• The brain is cephalic to the
spinal cord
• The brain is cranial to the
spinal cord
• The spinal cord is inferior to the
brain
• The brain stem is anterior to the
cerebellum
• The cerebellum is posterior to the
brain stem
Second system of “higher, lower, more
forward,
more
backward”
System
The human anatomical neuraxis starts as a
referenced to
straight tube (called the neural tube).
During development it bends/curves almost
anatomical
90 degrees at the juncture of the brainstem
neuraxis, which and diencephalon
is straight in
many animals,
and curved in
humans.
rostral/
caudal;
ventral /
dorsal
Human
anatomical neuraxis = brain
and spinal cord
1- early human embryo neurological
system, straight like the salamander’s
2- human embryo neurological
system- 3 weeks; curved neuraxis!
3-mature human;
major curve remains
near juncture of
brainstem and
diencephalon; neuraxis
“mushrooms out”
around curve
Second system of “higher, lower, more
forward, more backward”
Examples:
• The front part of the cerebrum is
rostral to the spinal cord
• The spinal cord is caudal to the
front part of the cerebrum
• The brain stem is ventral to the
cerebellum; the lower part of the
cerebrum is ventral to the upper
part of the cerebrum
• The cerebellum is dorsal to the
brainstem; the upper part of the
cerebral is dorsal to the lower part
of the cerebrum
Compare the two systems of “higher, lower,
more forward, more backward”
The neuraxis bends around
the junction between the
midbrain and diencephalon,
so….
– At the level of the spinal
cord and brainstem
• Anterior=ventral
• Posterior=dorsal
• Superior=rostral
• Inferior=caudal
– At the level of the
diencephalon and the
telencephalon
• Inferior=ventral
• Superior=dorsal
Posterior
Anterior
Rostral
Superior
Inferior
System of “closer to the midline,
farther from the midline”
Anterior view of brain
Medial/ lateral
Lateral view of brain
lateral
medial
Medial view of brain
lateral
System of “how close to the point
of connection with the body”
Proximal= nearer to the
point where the structure
connects to the body
vs.
Distal = farther from the
point where the structure
connects to the body
Posterior
Superior
Anterior
Inferior
Example: The shoulder is more proximal to the body than the
fingers. The fingers are more distal from the body than the
shoulder. Shoulders more proximal, fingers more distal……
Limb Movement Terms
• Flexion
• Extension
• Abduction
• Adduction
• Pronation
• Supination
Sections/Planes:
A cut through the body, or a part of it,
is called a section;
the resulting cut surface is called a
plane
Sections/Planes
• First system based on slices
through 3-D space
– Horizontal section/plane (A)
– Coronal section/plane (B)
– Sagittal section/plane (C)
Posterior
Superior
Anterior
A
C
B
Inferior
Sections/Planes:
First System (Continued)
A. Horizontal
B. Coronal (when anterior,
also called frontal)
C. Midsagittal (also called medial)
C. Parasagittal
Sections/Planes: Second system
• Second system based
on slices at right
angles to longitudinal
axis of the structure
– Transverse or cross
section/plane
Remember that the
longitudinal neuraxis
is curved
Compare the two systems of sections/planes
The neuraxis bends around
the junction between the
midbrain and diencephalon,
so….
– At the level of the spinal
cord and lower brainstem
• Horizontal=transverse
– Near the bend (upper
brainstem and
diencephalon)
• Transverse has no
analog in the 3-D system
of sections/planes
– Rostral to the diencephalon
• Coronal = transverse
and is also called a
frontal section/plane
Anatomic vs. clinical orientation
(from readings)
• Compare the two. See especially pp. 24
and 25 (Figure 1-9)