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Tissues

Tissues. 2 / 9. Tissue and organ. 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

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Tissues

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  1. Tissues

  2. 2/9 Tissue and organ • 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 

  3. 3/9 Epithelial tissues • 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

  4. 4/9 Connective tissue • 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

  5. 5/9 Nervous tissue • 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

  6. 6/9 Nervous system I. • 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, ,  Blumenfeld, Sineauer Assoc. Inc., 2002, Fig. 4-15 Blumenfeld, Sineauer Assoc. Inc., 2002, Fig. 2-25 Blumenfeld, Sineauer Assoc. Inc., 2002, Fig. 2-2 Blumenfeld, Sineauer Assoc. Inc., 2002, Fig. 4-13

  7. 7/9 Nervous system II. • 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 – blood-brain 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

  8. 8/9 Nervous system III. • 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  Vander et al.: Human Physiology, McGraw-Hill, 1975, Fig.64-40.

  9. 9/9 Nervous system IV. • 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 Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 11-15.

  10. End of text

  11. Tissue types

  12. Peripheral efferents Vander et al.: Human Physiology, McGraw-Hill, 1975, Fig.64-40.

  13. Parts of the forebrain Blumenfeld, Sineauer Assoc. Inc., 2002, Fig. 2-2

  14. Cortical areas Blumenfeld, Sineauer Assoc. Inc., 2002, Fig. 2-25

  15. Sagittal section in MRI Blumenfeld, Sineauer Assoc. Inc., 2002, Fig. 4-15

  16. Horizontal section Blumenfeld, Sineauer Assoc. Inc., 2002, Fig. 4-13

  17. Autonomic nervous system Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 11-15.

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