Histology - Connective Tissue - Tissues, Science Video Lecture - Class 9

earlier we learned about respiratory
mucosa we learned about pseudo
stratified ciliated columnar epithelium
we learned about copper cells we learned
about basement membrane and today we
will enhance our knowledge about
connective tissue connective tissue of
mucosa respiratory Mikko as known as
lamina propria and it is a loose
connective tissue one of the main
functions is to provide support to
epithelium it is rich in blood supply as
you can see several blood vessels with
erythrocytes or red blood cells within
it contains numerous cells most
importantly fibroblasts that make that
primarily make extracellular fibers
let's try to have a better understanding
of connective tissue connective tissue
as we know is one of the four types of
tissues found in a human body the term
is a very broad term and refers to a
variety of tissues all with some common
features it is also the most abundant
tissue in the body
although this slide under review belongs
right here and we are dealing with lower
respiratory tract but we will have to
discuss connect it which in general
rather than just focusing on loose
connective tissue of lamina propria for
better understanding we will use a few
slides that do not belong to the spirit
system we have a slide in front of us
that shows dense connective tissue
rather than loose connective tissue we
have a number of cells and everything
between cells is known as extra cellular
matrix please note that the tissue does
not belong to respiratory system it just
shows better details and will help us
understand the concepts the term
connective tissue represents two
different components namely cells these
are the nuclei of cells
in the connective tissue and the
extracellular matrix the most important
cells of lose or dense connective tissue
are number one fibroblasts these cells
make most of the extracellular matrix
most importantly fibers that bind these
cells together these cells are
recognizable by their lung elongated
nuclei so we can confidently say that
these nuclei belong to fibroblasts and
these fibroblasts are mobile cells that
make this extracellular matrix most
importantly fibers the tissue also has
cells that migrate from blood for
defense or immunity these cells are
plasma cells lymphocytes neutrophils
using offense basophils and mast cells
macrophages fat cells are also found
unlike epithelia most cells of the loose
and dense connective tissue are very
mobile and move from one place to
another place easily extra cellular
matrix fills the gaps between the cells
so these bluish looking structures are
nuclei of cells and everything between
cells is known as extra cellular matrix
these cells have much wider gaps in
contrast to tightly packed cells of the
epithelium extracellular matrix plays an
important role in functioning of the
tissue and it is composed of two major
components fibers and ground substance
fibers are thread-like structures and
all are made up of proteins
unfortunately these are not visible
easily under hematoxylin and using a
stain so we have a slide with the
special stain that shows some of these
fibers clearly fibers of loose and dense
connective tissue are mostly made by
fibroblasts
however these fibers can also be made by
other cells
groovy smooth muscle cells fibroblasts
are mobile cells and can be seen under
the special microscopes moving around
the tissue and knitting webs just like
spiders there are three different types
of fibers collagen fibers elastic fibers
and reticular fibers so the pinkish or
reddish thread looking structures are
collagen fibers and these purple looking
threads which are smaller in diameter as
compared to collagen fibers are elastic
fibers reticular fibers are not visible
in this slide collagen fibers are made
up of protein called collagen the most
abundant protein in the body these are
quite as strong and provide firmness and
structure to the tissue collagen fibers
are found in almost all types of
connective tissues including bones
tendons and cartilages construction of
collagen fiber occurs within an outside
of fibroblast Assembly of subunits of
collagen molecules happens outside of
fibroblast at the plasma membrane of the
cells and need presence of special
enzymes in extra cellular matrix elastic
fibers are also made up of a protein
which is called elastin the elastic
fibers are much smaller in diameter as
compared to collagen fibrils as we can
see here they appear to have a branching
pattern in contrast to collagen fibers
they have an enormous ability to stretch
and then recoil back to their original
size they have an ability to stretch up
to hundred and fifty percent of their
original size without being damaged this
gives a number of organs elasticity such
as skin and lungs it is this fiber that
prevents arteries from over distension
body stops making this fiber at the age
of around thirteen wrinkles appear as a
result of loss of these fibers
similarly loss of these threads in
as a result of old age or smoking
decreases the elastic capability of
lungs which decreases lung function this
fiber is also known as fiber of beauty
scientists are trying to find ways to
reactivate genes that enable fibroblast
to make this fiber we have a chest x-ray
in front of us which shows a pair of
lungs that hardly have any elasticity so
the lungs are a bit bigger in volume and
they're just hanging down because of the
gravity notice the volume of lung is
visible beyond ninth posterior a bottle
the posterior ribs are not visible
clearly here but the other signs of
emphysema are also visible the
diaphragms are somewhat flat these
should be domed shape naturally and the
lungs should not be visible beyond ninth
posterior rib so such conditions are
thought to be a result of loss of
elastic fibers there is another type of
fiber which is emits a reticular fiber
and and these are also made up of type 3
collagen unfortunately we don't have a
good example here but in some tissues
this fiber is made by special cells
known as reticular cells very similar in
function to that of collagen fibers but
are more abundant in some tissues versus
others
so we'll do a bit of revision here the
connective tissue is made up of cells
and extracellular matrix which is
visible in front of you who has pink
pinkish material extracellular matrix is
composed of fibers that are made up of
proteins and the fibers are not visible
under this is chain the second component
of extracellular matrix is known as
ground substance so technically anything
between fibers and cells is known as
ground substance while fibers are
unneeded together as nets or web-like
formations to provide structural support
ground substance contains water complex
proteins and carbohydrates
to provide functional support ground
substance can be liquid and gelatinous
take fluid or calcified as in case of
bones ground substance also has a
regulated quantity of water and the
amount of water moving in and out of the
tissues in equilibrium excess
accumulation of water is known as edema
which causes swelling of the tissue one
of the important functions of ground
substances to provide a medium with a
very sensitive and controlled
environment for it cells to operate and
function all nutrients from blood
vessels diffuse through extracellular
matrix to reach cells and similarly all
and metabolic waste diffuses through
extracellular matrix before reaching the
blood vessels extracellular matrix is
usually synthesized within cells and is
secreted outside as and when necessary
and these are the references