HMB302H1 Study Guide - Midterm Guide: Osmoregulation, Disaccharide, German Type Vii Submarine
Coective Tissue
- Diverse group of tissues that form a continuum with nervous, muscle
epithelial tissue
- helps things connect together
- mainly for support and binding
- originates from the mesoderm→ mesenchymal ceolls → gives rise to the
connective tissues and their cells
- most common is loose connective tissue
- *** Everywhere you have epithelium, you will always have CT
Composition of CT
- CT is made of cells and extracellular matrix which makes the ground
substance and fibers, used to support
- mature connective tissue is referred to as connective tissue proper or
specialized connective tissue (cartilage and bone) → once you are
specialized you better be mature
- ** our emphasis is on CT proper, not embryonic cells
Function of CT:
Including:
- Structural support ** )t’s got a steel beams in the form of COLLAGEN
- As a medium of exchange (e.g. nutrients, metabolic waster, oxygen etc.)
- Defense and protection (phagocytic cells; immunocompetent cells,
inflammation).
- ** The main point of Ct is for support of epithelium and other tissues, but it
also acts as a medium for exchange, and defense because it has all those
white blood cells that help you fight shit off.
Cellular Component:
Grouped into two components:
Fixed cells: ** stable
- Resident population of cells that remain in place in the CT where they
perform their function.
- Stable and long-lived population that include fibroblasts, adipose cells, mast
cells etc.
Transient cells: ** Float around
- Free wandering cells
- Derived from the bone marrow and circulate in the bloodstream → into CT
where they perform their function.
- usually short lived cells that need cell renewal (stem cells)
- include plasma cells, lymphocytes, neutrophils, macrophages and many
others
- Transient cells are free wandering that usually come from the bone marrow
and flow through the vascular system to the connective tissue to perform a
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specific function, this is usually the inflammatory cells (wbc) like plasma cells
that differentiate into antibodies, also tf short lived.
Fixed cells
Transient Cells
stable
Float around
Resident pop
Derived in bone marrow,
Come from vasucular sys
Long lived
Short lived
Fibroblasts, adipose cells, mast
cells etc.
Usually inflammatory cells (wbc)-
plasma cells, lymphocytes,
neutrophils, macrophages, etc
Fixed connective tissue cells
Mesenchyme Cells: long oval nucleus
- most abundant in embryonic developing tissue
- Multipotential cells → differentiate into a variety of distinct cells types (e.g.
fibroblasts, osteoblast etc) → mesenchyme is a precursor for fibroblasts
- pleomorphic shape, with a long oval nucleus → hard to find in adult tissue
Fibroblasts:
- Main cell type in CT.
- Produces collagen, reticular and elastic fibres → fills in the spaces in the Ct
and help to form organ capsules, tendons and ligaments.
- Two forms of fibroblasts exist: active and inactive
- It is in very high number and carries the bulk of function. fills in spaces for
support.
- if in doubt of something you are looking at, you are most likely fibroblast!
Always guess fibroblast
- Active Fibroblasts:
• found in close association with collagen bundles (parallel to these
bundles) ** very close to the collagen it secretes
• elongated cells with a pale staining cytoplasm.
• Ket feature → dark stained, large, granular, oval shaped nucleus with
well defined nucleolus.
• Extensive RER system and golgi apparatus
• very common cell type.
• *** Key feature: dark neucleus with a very dark nucleolus
• so whenever you see a collagen, there is probably an active fibroblast
near (parallel)
- Inactive Fibroblasts:
• smaller, oval shaped cell body with an acidophilic cytoplasm
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• nucleus is smaller and elongated compared to the active form
• Contains RER (not as extensive as the active form) and many
ribosomes.
- Myofibrobalst:
• modified fibroblast – shares characteristic of both fibroblasts and
smooth muscle cells.
• Abundant in areas of wound repair, periodontal ligaments (tooth
eruption.)
• hard to distingus from normal fibroblasts, EM level- bundles of actin
filaments and dense bodies similar to smooth muscle cells.
• ** squeezes tissues together and to push your teeth out.
• ** in wound repair, you use this specialized fibroblast, helps contract
the blood vessels to move the fluid along.
Adipose Cells:
- fat cells or adipocytes.
- Function in the synthesis and storage of triglycerides
- Two major types:
• Single large lipid droplet- unilocular fat cells → forming WHITE
adipose tissue
• Multiple, small lipid droplets – multilocular fat cells → BROWN adipose
tissue ( not discus much, have lots of mitochondria within it, animals
that go thru hibernation have a lot of this)
- White Adipose Cells:
• large speherical cells (120 μm), shape changes when crowded-
polyhedral shape.
• Store fat in the form of single large droplet. Usually displaces the
cytoplasm and nucleus to the periphery, near the cell membrane.
• Septa may divide groups of adipose cells into lobes. Septa is CT.
• ** Looks like a really large droplet, the organelles, the nucleus will be
flattened along the side.
• key for adipose tissue→ signet
ring
• good way of storing energy
and filling in gaps in the
cytoplasm
•
- Brown Adipose Cells
• smaller and more polygonal than WAC
• store fat in many small droplets.
• Spherical nucleus, not pushed to the periphery of the cell →
multilocular when it stores the lipids so it wont be pushed out
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