Transcript Chapter 4 Tissues

The Tissue Level of
Organization
Tissues
A group of
similar cells
that function
together to
perform a
specific
function
Cell Junctions
Cellular Junctions
connect adjacent
cells
mechanically at
the cell
membranes or
through
cytoskeletal
elements within
and between
cells.
Tight Junctions
• Web-like strands of
transmembrane proteins
– Fuse cells together
– Seal off passageways
between adjacent cells
• Common in epithelial
tissues of the stomach,
intestines, and urinary
bladder
• Help to retard the passage
of substances between
cells and leaking into the
blood or surrounding
tissues
Adherens Junctions
• Resist separation of cells
during contractile
activities
• Structural components
– Transmembrane
glycoproteins called
cadherins insert into the
plaque and join cells
– Located inside of the plasma
membrane attached to both
membrane proteins and
microfilaments of the
cytoskeleton
– In epithelial cells, adhesion
belts encircle the cell
Desmosomes
• Contain plaque and
cadherins that extends
into the intercellular
space to attach
adjacent cells together
– Desmosome plaque
attaches to intermediate
filaments that contain
protein keratin
– Prevent epidermal cells
from separating under
tension and cardiac
muscles cells from
pulling apart during
contraction
Hemidesmosomes
• Resemble half of a
desmosome
– Do not link adjacent
cells but anchor cells to
the basement membrane
– Contains
transmembrane
glycoprotein integrin
– Integrins attach to
intermediate filaments
and the protein laminin
present in the basement
membrane
Gap Junctions
• Connect neighboring cells
via tiny fluid-filled tunnels
called connexons
– Plasma membranes of gap
junctions are separated by a
very narrow intercellular gap
(space)
• Communication of cells within a
tissue
• Ions, nutrients, waste, chemical
and electrical signals travel
through the connexons from one
cell to another
4 Basic Tissues
• Epithelial Tissue
– covers surfaces because cells
are in contact
– lines hollow organs, cavities
and ducts
– forms glands when cells sink
under the surface
• Connective Tissue
– material found between cells
– supports and binds structures
together
– stores energy as fat
– provides immunity to disease
• Muscle Tissue
– cells shorten in length
producing movement
• Nerve Tissue
– cells that conduct
electrical signals
– detects changes inside
and outside the body
– responds with nerve
impulses
Epithelial Tissue
General Features:
• Closely packed cells forming continuous sheets
• Cells sit on basement membrane
• Apical (upper) free surface
•
•
•
•
Avascular - nutrients diffuse in from underlying connective tissue
Good nerve supply
Rapid cell division
Covering / lining versus glandular types
Basic Functions:
- protection
- secretion
- absorption
- filtration
Types of Epithelium
• Covering and lining epithelium
– epidermis of skin
– lining of blood vessels and ducts
– lining respiratory, reproductive, urinary & GI tract
• Glandular epithelium
– secreting portion of glands
– thyroid, adrenal, and sweat glands
Basement Membrane
• Two Layers
– Basal lamina
– Reticular lamina
• Holds cells to
connective tissue
• Guide for cell
migration during
development
Classification of Epithelium
• Classified by arrangement of cells into layers
– simple
– stratified
– pseudostratified
• Classified by shape of surface cells
–
–
–
–
squamous
cuboidal
columnar
transitional
•
Epithelium
Naming epithelia according to shape
Flat, wide “paving
stone” cells
Cells as tall as they are
wide
Cells taller than they are
wide
•
Epithelium
Naming epithelia according to arrangement
One layer. All cells in
contact with basement
membrane
Appears to have layers, but
in reality all cells go from
the apex to the base
Two or more layers. Only
basal layer in contact with
basement membrane
Epithelial Tissues
1. Simple Epithelium
a. Squamous
b. Cuboidal
c. Columnar
2. Stratified Epithelium
a. Squamous
b. Cuboidal
c. Columnar
3. Pseudostratified columnar
4. Transitional
5. Glandular
Simple Squamous Epithelium
• composed of a single
layer of flat cells
found:
– In the air sacs of lungs
– In the lining of blood
vessels, the heart, and
lymphatic vessels
– In all capillaries,
including those of the
kidney
– As the major part of a
serous membrane
Simple Squamous Epithelium
Simple squamous
Side view
Glomerular capsules of the kidney
Simple Cuboidal Epithelium
• composed of a
single layer of
cube shaped cells.
– It is often found
lining
the tubules of the
kidneys and many
other glands.
Simple Cuboidal Epithelium
Simple Columnar Epithelium
• forms a single layer
of column-like
cells, ± cilia, ±
microvilli, ±
mucous (goblet
cells).
– Goblet cells are
simple
columnar cells that
have differentiated to
acquire the ability to
secrete mucous.
Simple Columnar Epithelium
Simple columnar
Digestive tract
Simple Columnar Epithelium
Simple columnar
Digestive tract
Pseudostratified Columnar
Epithelium
• appears to have layers,
due to nuclei which are
at various depths. All
cells are attached to the
basement membrane in
a single layer, but some
do not extend to the
apical surface.
– Ciliated tissue has goblet
cells that secrete mucous.
Pseudostratified Columnar
Epithelium
Pseudostratified ciliated columnar
Trachea
Pseudostratified Columnar
Epithelium
Pseudostratified columnar
Stratified Squamous Epithelium
• has an apical surface
that is made up of
squamous (flat) cells.
– The other layers have
different shapes, but
the name is based on
the apical layer.
– The many layers are
ideal for protection
against strong friction
forces.
Stratified Squamous Epithelium
Stratified squamous
Epidermis of the skin
Stratified Cuboidal Epithelium
Stratified Columnar Epithelium
Transitional Epithelium
• The cells change
shape depending on
the state of stretch in
the tissue.
– The apical “dome cells”
of the top layer (seen
here in relaxation) are
an identifiable feature
and signify an empty
bladder .
– In a full bladder, the
cells are flattened.
Transitional Epithelium
Transitional
Urinary bladder
Epithelium
 Stratified squamous epithelium is a prominent feature of the outer layers of
the skin.
 Simple squamous makes up epithelial membranes and lines the blood
vessels.
 Columnar is common in the
digestive tract.
 Pseudostratified ciliated
columnar is characteristic
of the upper respiratory tract.
 Transitional is found in the bladder.
 Cuboidal lines ducts and sweat glands.
Copyright © John Wiley & Sons, Inc. All rights reserved.
Glandular Epithelium
• Derived from epithelial cells that sank below the
surface during development
• Exocrine glands
– cells that secrete---sweat, ear wax, saliva, digestive
enzymes onto free surface of epithelial layer
– connected to the surface by tubes (ducts)
– unicellular glands or multicellular glands
• Endocrine glands
– secrete hormones into the bloodstream
– hormones help maintain homeostasis
Methods of
Glandular
Secretion
cells release their
products by
exocytosis:
- saliva
- digestive
- enzymes
- sweat
upper part of cell
pinches off
- sweat
- milk
whole cells die &
rupture to release their
products
- oil gland
Connective Tissue
General Features:
•
•
•
•
•
Cells rarely touch due to extracellular matrix
Matrix(fibers & ground substance secreted by cells
Consistency varies from liquid, gel to solid
Does not occur on free surface
Good nerve & blood supply except cartilage & tendons
Basic Functions:
- support to body organs
- storage
- protection
- binds body parts together
Connective Tissue
1. Ground substance: interstitial fluid, cell adhesion proteins,
proteoglycans
2. Fibers: Collagen, Elastin, Reticular
3. Cells: - blast
mast cells
- cyte
macrophages
- clast
blood cells
Connective Tissue
1. Loose connective tissue
3. Cartilage
a. Areolar connective tissue
a. Hyaline cartilage
b. Adipose tissue
b. Fibrocartilage
c. Reticular connective tissue
c. Elastic cartilage
4. Bone Tissue
2. Dense connective tissue
5. Blood tissue
a. Dense regular connective tissue (ligaments + tendons)
b. Dense irregular connective tissue (dermis of skin)
c. Elastic connective tissue (arteries, bronchial tubes)
Loose Connective Tissue
– Areolar Connective Tissue is the most widely
distributed in the body. It contains several types of cells
and all three fiber types.
• It is used to attach skin and underlying tissues, and as a packing
between glands, muscles, and nerves.
Areolar Connective Tissue
Areolar (4x)
fibroblasts;
macrophages; mast
cells
stretchable; loosely
arranged fibroelastic
tissue
packages organs
supports capillaries
Loose Connective Tissue
– Adipose tissue is located in the subcutaneous layer
deep to the skin and around organs and joints.
• It reduces heat loss and serves as padding and as an energy
source.
Adipose Tissue
Adipose (10x)
fat containing cells; act
as packing around and
between organs
Loose Connective Tissue
– Reticular connective tissue is a network of
interlacing reticular fibers and cells.
• It forms a scaffolding used by cells of lymphoid tissues
such as the spleen and lymph nodes.
Reticular Connective Tissue
Reticular
framework; spleen
Dense Connective Tissue
– Dense regular Connective Tissue comprise tendons,
ligaments, and other strong attachments where the
need for strength along one axis is mandatory (a
muscle pulling on a bone).
Dense Regular Connective Tissue
Dense regular
tendons
Dense Connective Tissue
– Dense Irregular Connective Tissue consists
predominantly of fibroblasts and collagen fibers
randomly arranged.
• It provides strength when forces are pulling from many
different directions.
Dense Irregular Connective Tissue
Dense irregular
dermis of the skin
Dense Connective Tissue
– Elastic Connective Tissue consists predominantly of
fibroblasts and freely branching elastic fibers.
• It allows stretching of certain tissues like the elastic arteries
(the aorta).
Elastic Connective Tissue
Elastic
Cartilage
• Cartilage is a tissue with poor blood supply
that grows slowly. When injured or inflamed,
repair is slow.
– Hyaline cartilage is the most abundant type of
cartilage; it covers the ends of long bones and parts
of the ribs, nose, trachea, bronchi, and larynx.
• It provides a smooth surface for joint movement.
Hyaline Cartilage
Hyaline cartilage (10x)
precursor of skeleton;
articular surface;
trachea; tip of nose
perichondrium
chondrocytes
chondroblasts
Cartilage
– Fibrocartilage, with its thick bundles of collagen
fibers, is a very strong, tough cartilage.
• Fibrocartilage discs in the intervertebral spaces and the
knee joints support the huge loads up and down the long
axis of the body.
Fibrocartilage
Fibrocartilage (40x)
dense and resistant to
stretching; vertebral
discs; pubic
symphysis
Cartilage
– Elastic cartilage consists of chondrocytes located in
a threadlike network of elastic fibers.
• It makes up the malleable part of the external ear and the
epiglottis.
Elastic Cartilage
Elastic cartilage (4x)
flexible;
predominance of
elastic fibers;
external ear;
epiglottis; larynx
Bone Tissue
• a connective tissue with a calcified intracellular
matrix. In the right circumstances, the
chondrocytes of cartilage are capable of turning
into the osteocytes that make up bone tissue.
Bone Tissue
Compact Bone (10x)
matrix- inorganic salts (calcium
phosphate and calcium
carbonate)
Blood
Blood
red blood cells
eosinophil (red arrow)
neutrophil (yellow arrow)
Blood
Blood
Muscle Tissue
• Cells that shorten
• Provide us with motion, posture and heat
• Types of muscle
– skeletal muscle
– cardiac muscle
– smooth muscle
Skeletal Muscle
• Cells are long cylinders with many peripheral nuclei
• Visible light and dark banding (looks striated)
• Voluntary or conscious control
Skeletal Muscle
Skeletal (40x)
Cardiac Muscle
• Cells are branched cylinders with one central nuclei
• Involuntary and striated
• Attached to and communicate with each other by intercalated discs
and desmosomes
Cardiac Muscle
Smooth Muscle
• Spindle shaped cells with a single central nuclei
• Walls of hollow organs (blood vessels, GI tract, bladder)
• Involuntary and nonstriated
Smooth Muscle
Smooth (10x)
Nervous Tissue
•
•
Cell types -- nerve cells and neuroglial (supporting) cells
Nerve cell structure
– nucleus & long cell processes conduct nerve signals
• dendrite --- signal travels towards the cell body
• axon ---- signal travels away from cell body
Tissue Repair
• Inflammation: protect damaged area and bring in
supplies for repair
• Fibrosis: replacement with stromal connective tissue
cells, scar formation (fibroblasts)
• Regeneration: replacement with original cell types
(parenchymal cells)
– some cell types can divide (liver & endothelium)
– some tissues contain stem cells that can divide
• bone marrow, epithelium of gut & skin
– some cell types can not divide & are not replaced
• muscle and nervous tissue