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Tissues
Tissue and organ
2/9
• tissue: assembly of specially differentiated
cells
• organ: assembly of cells specialized for a given
function – in most cases it is built up of
several types of tissues
• character might be determined by one of the
tissues (e.g. bone, muscle) – see brick house
• the character of the tissue is determined by
the cells and by the components of the
interstitial space
• tissue types:
– epithelial
– nervous
– connective
– muscle
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Epithelial tissues
3/9
• main function: to cover surfaces
• tightly fitted cells, no interstitial space
• it is one layered if there is no mechanical or
osmotic stress (blood vessels, body cavities)
• it is multilayered (stratified) if it has to resist
mechanical or osmotic stress (mouth, anal and
vaginal orifices)
• specific epithelium is found in the skin (organ!):
dead cells in the uppermost layer filled with
keratin – defense against evaporation and
injuries
• columnar, cuboidal and flat epithelium –
stratified named after the uppermost layer
• specific structures might be present on the
surface:
– microvilli (kidney, gut): length 0.5 µ, width 0.1 µ –
200 million/mm2 – surface
– cillia (respiratory tract): length 10 µ, width 0.25 µ –
10 million/mm2 - moving mucus
Connective tissue
4/9
• function: mechanical, but blood
• many different types, very heterogeneous
• interstitial space is large, it contains fibers
(collagen, elastic and reticular fibers) and
amorphous material (polysaccharides,
anorganic minerals)
• classic experiment with chicken bone – acid
and heating – see also young and old bones
• most important forms:
–
–
–
–
–
blood
bone
cartilage
tendon
adipose tissue
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Nervous tissue
5/9
• neuronal and glia cells
• neuronal – excitability, glia – supportive (now
many other functions as well)
• neurons:
–
–
–
–
–
–
perikaryon, soma, cell body, Nissl-bodies
dendrit (spines), neurit or axon (processes)
axon hillock, initial segment, collateral
neurit+myelin sheath = neuronal fiber
telodendrion
unipolar, bipolar, pseudounipolar, multipolar,
characteristic dendrit arborization
• axons are insulated, except at the very
beginning and at the very end
• myelin sheath: Schwann cell (periphery),
oligodendroglia (centrally) – color is white
• non-myelinated thin fibers (C): Schwann cell,
but one cell for many axons – color gray
Nervous system I.
6/9
• central nervous system (CNS) = brain and
spinal cord
• peripheral nervous system (PNS) = cranial and
spinal nerves, ganglia, enteric nervous system
• central nervous system
– spinal cord is segmented: 8 cervical, 12 dorsal, 5
lumbar, 5 sacral, 1 caudal segments
– brainstem: medulla, pons (rhombencephalon),
midbrain (mesencephalon)
– cerebellum
– cerebrum (forebrain): diencephalon (thalamus and
hypothalamus), telencephalon (basal ganglia and
cortex), other areas
– cortex is divided into lobes mainly by the bones of
the skull: frontal, parietal, temporal, occipital,
limbic (e.g. hippocampus), insula, olfactory cortex,
,
,
corpus callosum
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Nervous system II.
7/9
• central nervous system continued
– two main components: white and gray matters –
position different in brain and spinal chord
– cortex is convoluted in humans, but not in rats –
surface
– gyrus (gyri), sulcus (sulci)
– CNS is covered by three membranes: dura mater,
arachnoid, pia mater
– inside the CNS: cavities filled with cerebrospinal
fluid (CSF) or liquor – lateral ventricles, third and
fourth ventricles, central canal
– the same fluid within the arachnoid – produced by
the chorioid plexes- strictly controlled – bloodbrain barrier (medicines not always penetrate)
– one of its functions: mechanical protection by
decreasing the weight of the brain (Archimedes) –
if removed or lost – headache
– disturbances in production and reabsorbtion:
hydrocephalus
Nervous system III.
8/9
• peripheral nervous system
– interface between the environment, the effectors
and the central nervous system - sensory and
motor parts
– sensory part: primary sensory neuron always
outside the CNS in a ganglion (e.g. dorsal root
ganglion), bipolar or pseudounipolar
– motor part is more complicated
– somatic and autonomic or vegetative system
– the two can be differentiated best at the efferent
part of the PNS – afferents are similar, centers
are ambiguous
– somatic efferents: neuron in brainstem or spinal
cord, long dendrites, many inputs, ending on
striated muscle fibers directly
– leave the CNS in cranial (12 pairs) and spinal (31
pairs) nerves
– vegetative efferents: reach smooth muscle, heart
or gland cells after a synapse in a ganglion
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Nervous system IV.
9/9
• peripheral nervous system continued
– vegetative nervous system has two parts
– sympathetic:
• leaves the CNS with thoracic and lumbar spinal nerves
• synapses far from target – paravertebral or prevertebral
ganglia
• preganglionic fiber – nACh, postganglionic fiber mainly –
NA, rarely mACh (sweat glands)
• alpha1 – IP3, contraction
• alpha2 – cAMP inhibition (autoreceptor mainly)
• beta1, 2, 3 – cAMP increase – relaxation and other
effects
– parasympathetic:
•
•
•
•
•
leaves the CNS through cranial and sacral spinal nerves
synapses near to the target
preganglionic fiber – nACh, postganglionic fiber mACh
M1 – cAMP, K-channel inhibition – hypopolarization
M2 – K-channel opening – hyperpolarization
– not every organ receives both types of fibers body wall (blood vessels) sympathetic only
– not always antagonistic, parasympathetic – local
reflexes, regulation, sympathetic – general effects
Tissue types
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Peripheral efferents
Vander et al.: Human Physiology, McGraw-Hill, 1975, Fig.64-40.
Parts of the forebrain
Blumenfeld, Sineauer Assoc. Inc., 2002, Fig. 2-2
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Cortical areas
Blumenfeld, Sineauer Assoc. Inc., 2002, Fig. 2-25
Sagittal section in MRI
Blumenfeld, Sineauer Assoc. Inc., 2002, Fig. 4-15
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Horizontal section
Blumenfeld, Sineauer Assoc. Inc., 2002, Fig. 4-13
Autonomic nervous system
Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 11-15.
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