"NeuroVerse: Unraveling the Mysteries of Nervous Tissue",NEUROSCIENCES anatomy,2nd year,DUHS,class notes
Hemopoiesis
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Histology (HISTOLOGY)
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Connective Tissue HISTOLOGY
OUTLINE ○ Useful in regenerative medicine after grafting to replace
l. Connective Tissue damaged tissue in certain patients
II. Cells of Connective Tissue ● Mesenchyme-like cells remain present in some adult
Fibroblasts connective tissue
Adipocytes ○ Tooth pulp and some adipose tissue
Macrophages & MPS
Mast cells
Plasma cells CELLS OF CONNECTIVE TISSUE
Leukocytes
III. Fibers ● Fibroblasts
Collagen ○ Key cells in connective tissue proper
Reticular Fibers ○ Permanent residents of connective tissue
Elastic fibers ● Other cells found here, such as macrophages, plasma cells,
IV. Ground Substance and mast cells, originate from hematopoietic stem cells in bone
V. Types of Connective Tissue marrow, circulate in the blood, move into connective tissue where
Connective tissue proper they function.
Reticular fibers
Mucoid tissue
CONNECTIVE TISSUE
● Provides the matrix that supports and physically connects other
tissues and cells together to form the organs of the body
● The interstitial fluid of connective tissues gives metabolic support
to cells as the medium for diffusion of materials and waste
products.
● Major constituent: EXTRACELLULAR MATRIX
● Extracellular matrix consist of:
○ Protein fibers (collagen and elastic fibers)
○ Ground substance
■ a complex of anionic hydrophilic proteoglycans
■ glycosaminoglycans (GAGs)
■ multiadhesive glycoproteins (laminin, fibronectin, and
others)
● Embryology
○ Connective tissues originate from embryonic mesenchyme Fibroblasts
■ A tissue developing mainly from the middle layer of the
embryo - the mesoderm
■ Consist largely of viscous ground substance with few
collagen fibers
■ Undifferentiated and have large nuclei, with prominent
nucleoli and fine chromatin
■ “Spindle-shaped”, scant cytoplasm extended as two or
more thin cytoplasmic processes.
● Most common cells in CT proper
● Produce and maintain most of the tissue’s extracellular
components.
● Synthesize and secrete collagen (most abundant protein of the
body) and elastin - both form large fibers
● Synthesize and secrete GAGs, proteoglycans, and
multiadhesive glycoproteins - comprise the ground substance
● Fibroblast - active cell
○ More abundant and irregularly branched cytoplasm
○ Containing much RER and a well-developed Golgi apparatus
MEDICAL APPLICATION ○ Large, ovoid, euchromatic nucleus and prominent nucleolus
● Some cells in mesenchyme are multipotent stem cells ● Fibrocyte - quiescent cell
○ Smaller than active fibroblast
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, Connective Tissues
○ Spindle-shaped with fewer processes ● Function in the localized release of many bioactive substances
○ Much less RER important in the local inflammatory response, innate immunity,
○ Darker, more heterochromatic nucleus and tissue repair.
● Fibroblasts are targets of many families of proteins called growth ○ Heparin - a sulfated GAG that act locally as an anticoagulant
factors that influence cell growth and differentiation ○ Histamine - promotes increased vascular permeability and
● Myofibroblasts smooth muscle contraction
○ Involved in wound healing ○ Serine proteases - activate various mediators of
○ Have a well-developed contractile function and are enriched inflammation
with a form of actin also found in smooth muscle cells. ○ Eosinophil and neutrophil chemotactic factors - attract
those leukocytes
MEDICAL APPLICATION ○ Cytokines - polypeptides directing activities of leukocytes and
● Scar tissue other cells of the immune system
○ Dense irregular connective tissue that filled the spaces left ○ Phospholipid precursors - converted to prostaglandins,
after injuries (ischemia, inflammation, traumatic injury) of leukotrienes, and other important lipid mediators of the
tissues whose cells divide poorly or not at all inflammatory response
● Wound contraction ● Perivascular mast cells - small blood vessels in skin and
○ Activity of myofibroblasts is important in this phase of tissue mesenteries
repair ● Mucosal mast cells - tissue that lines digestive and respiratory
tracts
Adipocytes ● Promotes allergic reactions known as immediate
● Fat cells hypersensitivity reactions
● Specialized for cytoplasmic storage of lipid as neutral fats, or less ○ Anaphylactic shock - a potentially fatal condition
commonly for the production of heat ○ First exposure (to an antigen) : antibody producing cells
● Serves to cushion and insulate the skin and other organs produce IgE - binds to receptors on surface of mast cells
○ Second exposure (to same antigen) : IgE reacts on mast cells
Macrophages & the Mononuclear Phagocyte System - rapid release of Histamine, Leukotrienes, Chemokines and
● Macrophages Heparin - onset of allergic reactions
○ Have highly developed phagocytic ability and specialize in ○ Degranulation of mast cells als occurs as a result of the action
turnover of protein fibers and removal of dead cells, tissue of the complement molecules that participate in the
debris, or other particulate material immunologic reaction
○ abundant at sites of inflammation
○ “Histiocytes” Plasma Cells
○ Derived from bone marrow precursor cells called monocytes ● Lymphocyte-derived, antibody-producing cells
that circulate in the blood ● Relatively large, ovoid cells have basophilic cytoplasm rich in
■ Cross the epithelial wall of small venules to enter RER and a large Golgi apparatus near the nucleus that may
connective tissue, where they differentiate, mature, and appear pale in histologic preparations
acquire the morphologic features of phagocytic cells ● Eccentrically located nucleus
○ Play a very important role in the early stages of repair and ● Average lifespan = 10 - 20 days
inflammation after tissue damage
○ Normally present in the stroma of most organs
● Mononuclear phagocyte system
○ A family of monocyte-derived cells
○ Have different names in various organs
■ Kupffer cells - liver
■ Microglial cells - CNS
■ Langerhans cells - skin
■ Osteoclasts - bone
○ Highly important for the uptake, processing, and presentation
of antigens for lymphocyte activation
Mast Cells
MEDICAL APPLICATION
● Plasma cells
○ Derived from B lymphocytes
○ Responsible for the synthesis of immunoglobulin antibodies
● Each antibody is specific for the one antigen that stimulated the
clone of B cells and reacts only with tjat antigen or molecules
resembling it.
● An antigen that is a toxin may lose its capacity to do harm when
it is bound by a specific antibody
● Bound antigen-antibody complexes are quickly removed from
tissues by phagocytosis
● Oval or irregularly shaped cells of CT filled with basophilic Leukocytes
secretory granules that obscure the nucleus ● Comprise a population of wandering cells in CT
● Display metachromasia (can change the color of some basic ● Derived from circulating blood cells
dyes) due to the high content of acidic radicals in their sulfated ● They leave blood by migrating between the endothelial cells of
GAGs venules to enter CT - increases greatly during inflammation
● Function only for a few hours or days and then undergo apoptosis
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