Transcript Dense Connective Tissue

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Tissues are groups of cells that are similar in
structure and function.
Tissues are organized into organs (heart,
lungs, liver, kidneys…etc.) and can be a
combination of different kinds of cells.
Histology is the study of tissues.
A pathologist is a scientist who specializes
in cells and tissues in order to help physicians
make a diagnosis.
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Epithelial – COVER the body
Connective – PROTECT and SUPPORT the
body
Muscle – MOVEMENT of the body
Nervous – CONTROL of the body
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Covers body surfaces and lines cavities,
hollow organs and tubes. It also forms
glands.
Cells are closely packed and arranged in
sheets of either single or multiple layers.
Bottom surface of epithelium is attached to
the basement membrane- fibers that are
located between the epithelium and the
connective tissue below it.
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Avascular- without blood vessels. Epithelium
gets nutrients from the adjacent connective
tissue.
Has a nerve supply.
Is constantly being regenerated because it
suffers so much wear and tear.
Epithelium is classified by the cell shape, the
number of cell layers, and other modifications.
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Squamous
Thin and flat and attach
to each other like tiles.
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Cuboidal
Shaped like cubes and produce
important secretions (fluids) like
sweat and mucus. Also absorb
fluids like digested nutrients.
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Columnar
taller than wide and functions to
protect underlying tissues and
secrete and absorb fluids.
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Transitional
Range from flat to columnar and often change
shape due to stretching or movement of body
parts.
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Simple-
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one layer
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usually involved in
absorption and/or diffusion
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Stratified-
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many layers
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Protects underlying tissues
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Pseudostratified
- Looks like many
layers because not all
cells reach the surface
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Cilia- Tiny hairs that move
substances around outside the
cell
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Microvilli- Folds that increase
surface area for absorption
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Goblet cells- embedded in
between epithelium and secrete
mucus for lubrication or to trap
particles
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Contains cells that secrete substances into
ducts, onto a surface or in the blood.
 Exocrine Glands-Secrete substances via
a duct. Examples include mucus, oil,
earwax, saliva, and milk.
 Endocrine Glands- Are ductless and
secrete hormones which diffuse into the
bloodstream.
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Simple squamous
epithelium
•Squamous cells have the appearance of thin, flat
plates
•They form the lining of cavities such as the mouth,
blood vessels, heart and lungs and make up the
outer layers of the skin.
Simple Squamous – Top View – found in the
walls of capillaries and alveoli of lungs
Simple cuboidal epithelium
• Cuboidal cells are roughly square or cuboidal in shape.
• Each cell has a spherical nucleus in the centre.
• Cuboidal epithelium is found in glands and in the lining of
the kidney tubules as well as in the ducts of the glands. It
functions in secretion and absorption.
Simple Cuboidal Epithelial Tissue – this is of
the collecting duct of the kidney
Simple columnar epithelium
• The cells are elongated and column-shaped. The nuclei are
elongated and are usually located near the base of the cells.
• Columnar epithelium forms the lining of the stomach and
intestines and protects as well as secretes/absorbs.
• Goblet cells (unicellular glands) are found between the
columnar epithelial cells. They secrete mucus.
Simple Columnar Epithelial Tissue - This is a
cross section through the small intestine – for
absorption – microvilli on surface of cells
Stratified Squamous Epithelium
•The superficial layers are squamous while the layers below
may be cuboidal or columnar. This tissue makes up the top
layer of skin and contains keratin- a waterproof protein. Nonkeratinized forms of this tissue are found in wet areas- inside
the mouth, esophagus and vagina.
Stratified Cuboidal Epithelium
• Found in the ducts of adult sweat glands and part of the
male urethra. This functions in limited secretion and
absorption.
Stratified Columnar Epithelium
• The superficial cells only are columnar. The cells below
are irregularly shaped. This tissue lines part of the urethra,
the eye and the ducts of glands like the salivary. This tissue
functions in protection and secretion.
Pseudostratified Columnar
• Not a true stratified tissue. The nuclei of the cells are at
different levels. This functions in secretion and movement of
mucus. It can be found in the upper respiratory tract where
the tissue cells have cilia. It can also be found in the path
that sperm take. Here the cells are not ciliated.
Transitional Tissue
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Most abundant and widely distributed
tissue type
Function in binding other tissues
together and providing support
Cells of connective tissue are embedded
in a matrix , which is composed of a
ground substance and fibers.
Highly vascular
Has a nerve supply (except cartilage)
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Matrix is either solid, semi-solid or liquid type.
The ground substance is the part of the matrix
that takes up the space between cells and
binds them together.
 Contains large molecules like hyaluronic acid,
which is a slippery substance that lubricates joints
and helps white blood cells move through
connective tissue.
 Contains adhesion proteins which link parts of the
ground substance together.
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Fibers are another part of the matrix.
 Include collagen, elastic and reticular fibers.
▪ Collagen fibers give connective tissue flexibility and occur in
parallel bundles. They are found in bone, cartilage, tendons
and ligaments.
▪ Elastic fibers branch to form a network. They can be stretched
up to 1 ½ times their relaxed state. They are found in skin,
blood vessel walls and lung tissue.
▪ Reticular fibers are also branching. They help to form the
basement membrane and are found surrounding fat cells,
nerve fibers and some muscle tissue.
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Fibroblasts- Most numerous connective tissue cells.
Produce the fibers and ground substance of matrix.
Macrophage- Type of white blood cell that engulfs
bacteria.
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Plasma cells- Produce antibodies which fight foreign
invaders.
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Mast cells- Produce histamine which dilates blood
vessels during the body’s response to injury or infection.
 Adipocytes- Store fat
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There are 6 types of mature connective
tissue. They include: loose connective
tissue, dense connective tissue,
cartilage, bone tissue, blood tissue and
lymph.
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Areolar Connective Tissue Makes up the subcutaneous layer just below the
skin.
 Includes all 3 fiber types: collagen, elastic and
reticular.
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Adipose Connective Tissue Contains adipocytes
 This is also found in the subcutaneous layer below
the skin as well as around organs.
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Dense Connective Tissue contains more fibers
and fewer cells.
There are 3 types of DCT:
 Dense regular- Forms tendons and ligaments
 Dense irregular- Forms outer covering of bone,
pericardium around the heart, and heart valves.
 Elastic connective- Lung tissue, walls of elastic
arteries, trachea, and vocal cords.
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Cartilage can endure more stress than loose
and dense connective tissues. It’s resilience is
due to the compound chondroitin sulfate.
Cells of mature cartilage are called
chrondrocytes.
Avascular and lacks nerves
Three types of cartilage: hyaline,
fibrocartilage and elastic
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Appears in the body as a bluish-white, shiny
substance.
Chondrocytes are prominent when tissue is
stained but fibers are not.
Most abundant cartilage in the body.
Weakest of the 3 types of cartilage.
Found at the ends of ribs, the nose, and the
trachea.
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Consists of chondrocytes scattered among
bundles of collagen fibers.
Located between vertebrae, where hip bones
join on the anterior side and the cartilage
pads of the knee.
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Chondrocytes are embedded in a threadlike
network of fibers
Located in the external ear and the epiglottis
(flap of tissue that covers the trachea so food
does not get in).
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Includes bone, the periosteum (outer
covering), and bone marrow.
Compact bone includes:
• Lamellae- rings of mineral deposits (gives
compact bone its strength
• Lacunnae- spaces between lamellae
• Haversian canals- In the middle of lamellae where
blood vessels and nerves run.
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Has a liquid matrix called plasma.
Plasma carries red blood cells- which
transport oxygen and carbon dioxide. It also
carries white blood cells that fight infection
and platelets that participate in blood
clotting.
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Connective
Tissues….
LOOSE CONNECTIVE TISSUE (Areolar)
ADIPOSE TISSUE
FIBROUS (DENSE) CONNECTIVE TISSUE
HYALINE CARTILAGE
FIBROCARTILAGE
ELASTIC CARTILAGE
BONE
BLOOD
Tissue Quiz…
See how many
You can correctly
identify
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#2
#3
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Muscle tissue consists of cells that are highly
specialized to generate force. This force,
produces motion, maintains posture, and
generates heat.
Muscle tissue cells have lots of mitochondria.
Why?
There are 3 types of muscle tissue. They are
skeletal muscle, smooth muscle and cardiac
muscle.
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Skeletal muscle is named for its location. It is
attached to bones of the skeleton.
 Made of long cells called muscle fibers that
attach to bones by connective tissue (tendon).
Do you remember what kind of connective
tissue? These cells are multinucleated.
 Proteins within skeletal muscle cells are very
organized creating striations (alternating light
and dark bands).
 In most cases, this type of muscle tissue is
voluntary (consciously controlled). Can you
think of a case when it is involuntary?
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Smooth muscle is located in the walls of
hollow internal structures such as blood
vessels, airways to the lungs, the stomach,
intestines, gall bladder and bladder.
 It constricts blood vessels, physically breaks down
and moves food through the digestive tract and
moves fluid through the body.
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Smooth muscle tissue is not striated and
involuntary
The cells of smooth muscle have 1 nucleus.
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Cardiac muscle forms the bulk of the
wall of the heart.
Cardiac tissue is striated and
involuntary.
Cardiac muscle fibers are y-branched
and have 1 nucleus.
Cardiac muscle fibers are attached end
to end by thickened membranes called
intercalated disks. These hold the fibers
together during contractions.
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intercalated disk
nucleus
striations
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Nervous tissue functions to convert stimuli
into nerve impusles (electricity) and conduct
these impulses to other nerve cells, muscle
fibers or glands.
The 2 types of nerve cells are neurons and
neuroglia.
Neurons conduct nerve impulses and
neuroglia do not.
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The neuron has 3 basic parts:
 Cell body- contains the nucleus and other
organelles.
 Dendrites- many short branches off of the cell
body that receive input.
 Axon- Single, long and thin extension off of the
cell body that sends information to another
neuron or other tissue.
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