Connective Tissue - Most abundant in the human body.
- Embryonic is mesenchyme, not yet specialized
-Four general types of tissue: Connective tissue proper,
cartilage, osseous, vascular
1. Connective tissue proper – fluid intercellular material
and fibroblasts as the most abundant cell type (fibers,
syrupy ground substance and cells. (Four types)
a. Loose areolar tissue – indicates many air spaces,
widespread (mucous membranes, around blood vessels
and nerves: subcutaneous)
Composed of a variety of
fibers, cells, and hyaluronic
acid as intercellular material.
i. Fibers
Collagenous (white) - Tough, resistant to
pulling, made of
collagen
Elastic (yellow) - Smaller, provides
strength (skin, blood
vessels, lungs)
Reticular - Thin, immature collagen fibers,
coated with glycoprotein,
supports the walls of blood
vessels, nerve cells, smooth,
framework of spleen and lymph
nodes – prevents collapse, yet
flexible
ii. Cells
*Fibroblasts – repair cells,
responsible for constantly
replacing damaged cells. AGING
– when repair cannot keep up
with damage
*Macrophages – large,
function to engulf bacteria and
cellular debris by
phagocytosis. (Security guards
– survey and destroy, cannot
take care of all invaders)
*Plasma Cells – blood,
lymphatic system, provide
immunity by secreting
antibodies
*Melanocytes – pigmented cells below the deepest layer
of skin, produce melanin (pigment that protects against
sun damage)
We all have about the same #, but some are large and
produce more melanin, freckles, moles
*Mast Cells – produce heparin (anticoagulant) and
histamine (dilates small blood vessels during
inflammation/allergic reaction – give antihistamines so
vessels do not dilate)
b. Adipose Tissue - Composed of adipocytes (look like
cobblestones or signet ring in shape)
- Subcutaneous in location
– fat storage which is necessary for hormone
production, energy reserve, insulation, protects
internal organs
c. Dense (collagenous) tissue – more numerous
cells and thicker fibers, closely packed, decreased
intercellular substance
*Located in muscle (stretch), ligaments (stability),
tendons (somewhere between – Achilles’ )
d. Elastic tissue – little different from above,
freely branching fibers, stretch and snap back
like a rubber band, allows for elasticity
*Located in muscles, ligaments and tendons
2. Cartilage “soft bone”
-No blood vessels or nerves except in the
perichondrium (tissue around the cartilage) if
damaged, doctors will go in and fix because it doesn’t
repair well on its own.
OSTEOARTHRITIS – excessive damage to the cartilage,
calcifies
a. Characteristics:
Dense network of
collagen and
chondroitin sulfate,
resilient and strong
b. Three types
*hyaline – (gristle) bluish-white in color, shiny, most
abundant type, embryonic skeleton is exclusively
composed of , clavicle is the only completely formed
bone at birth –WHY?
*fibrocartilage – found in the matirx of bone to give
strength and stability, bundle of collagen fibers,
between vertebrae
*elastic – threadlike network for flexibility
3. Osseous tissue (bone) – skeletal system
Basic unit is the OSTEON, composed of:
a. Lamellae – concentric rings of hard matrix (calcium)
b. Lacunae – spaces between lamellae, have Haversian
canals which contain nerves and blood vessels
4. Vascular tissue (blood)
a. Plasma – mostly water with dissolved substances
such as nutrients, wastes, enzymes, hormones,
respiratory gases ( O2, CO2)
b. Cells, etc.
*Erythrocytes - RBCs
*Leucocytes – WBCs – phagocytosis, immunity, allergic
reactions. High leucocyte # = infection, leukemia
(radiate to destroy bone marrow, replace)
*Platelets - clotting
Other Tissues
1. Muscle – highly specialized for contraction
a. Smooth
*walls of internal organs (hollow), blood vessels,
stomach, intestine, gall bladder, urinary bladder
*non-striated, involuntary (some controlswallowing, etc)
b. Cardiac
*bulk of heart
*involuntary, one nucleus per cell, striated,
intercalated disks, not as dense
c. Skeletal
*striated, voluntary, fibers are cylindrical (fiber =
cell), multiple nuclei
2. Neural tissue – one of the most specialized, largest
cell in the body (1 m)
a. Neurons – action cells, no
mitotic devices, pick up
stimulus and converts to
impulse (to other nerves,
glands, muscles)
*Dendrites – branches,
stimulus gatherer, takes
impulse to cell body,
increase connections
through stimuli
*Axons – long, single, conduct
impulses away from cell body
b. Neuroglia – cells that protect and support neurons
* Do not conduct
*Common sites of tumors (gliomas)
3. Membranes
a. Mucous – line cavities
that open to the outside
b. Serous – line cavities that do
not open to the outside, cover
organs, produce serous fluid
c. Synovial – line freely
moving joints, not open
to the outside