Cell Types & Tissues Chapter 3. What are Tissues? Tissues are groups of cells that have similar function There are 4 main tissue types: Epithelial.
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What are Tissues? Tissues are groups of cells that
have similar function There are 4 main tissue types:
Epithelial TissueConnective TissueMuscle TissueNervous Tissue
Epithelial Tissue Fit Closely together to form continuous
sheets Cells are bound together via tight junctions
and proteins called desmosomes Always have 1 free surface: the apical
surface, exposed to the body exterior or cavity of an organ
Lower surface rests on the basement membrane – structureless material secreted by the cells
Epithelial Tissue Avascular – having no blood
supply These tissues rely on diffusion of
materials through the capillaries that lie in the connective tissue
Easily regenerated
Epithelial Tissue Organized by shape and the number of layers Shape
Squamous – Flat, Tile-like Cuboidal – Cube Shape Columnar – Column Shape
Layers Simple – one layer Stratified – multiple layers Pseudostratified – columnar only, one layer of
cells with variable heights Transitional – vary due to stretching – cuboidal
to columnar basal membrane
Glandular Tissue Secrete various products 2 different types of glands
Endocrine – ductless, have lost their connection to the surface
Secretions diffuse into nearby capillariesExample: Thyroid
Exocrine – Retain their ducts and empty secretion on epithelial surface
Examples: Sweat and Oil glands, Liver, and Pancreas
Connective Tissue Most are highly vascularized
Tendons & Ligaments = Poor Blood Supply Cartilage = Avascular
These 3 take a LONG time to heal because of little/no blood
Made of living cells surrounded by a non-living Extracellular Matrix (ECM)
ECM Gives the ability to bear weight to form a soft tissue around organs to withstand stretching and other abuses
Connective Tissue Types:
Bone – Osseous Tissue – Protects body organs
Cartilage – flexible - 3 types Hyaline – lots of collagen, ribs, larynx, joints, &
fetal skeleton Fibrocartilage – highly compressible,
intervertebral disks Elastic – flexible, outer ear & nose
Connective Tissue Loose – Fewer fibers, softer
Areolar – widely distributed, protective wrapping of organs
Adipose – lots of fat cells, insulation and cushioning
Reticular – LOTS of fibers, forms the stroma of lymph organs to support free blood cells – need special stain to see!
Dense – Lots of Fibers, very organized
Connective Tissue BLOOD – made of cells surrounded
by a nonliving ECM Contains fibers that remain invisible
until a vessel is broken Then these fibers come together to
form a clot
Muscle Tissue Specialized to contract, or shorten Cells are elongated to provide better
contraction Individual Cells are called fibers There are 3 types:
SkeletalCardiacSmooth
Skeletal Muscle Tissue
Fibers are organized into sheets that form the organs, Skeletal Muscles
Attached to the Skeleton Voluntary Muscles – can be consciously
controlled Cells are
Long CylindricalMultinucleateStriated – Striped
Cardiac Muscle Tissue
Found only in the heart Cells are
UninucleateBranchingStriated
Branches meet at junctions called intercalated disksAllow ions to move freely from cell to
cell – creates electrical impulse Involuntary – not under conscious control
Smooth Muscle Tissue
Found in the walls of hollow organs and vessels
Contraction causes the cavity of an organ to either constrict or dilate
Contracts more slowly than the other 2 types of muscle Ex: Peristalsis – wavelike motion that keeps
food moving through the digestive system Cells are
Uninucleate Spindle-shaped Not Striated
Nervous Tissue Receive and conduct electrochemical
impulses Cells have long extensions which allow
a single neuron to reach multiple sites Along with numerous supporting
cells, they make up the nervous system organs – spinal cord, brain, and nerves
Tissue Repair 2 major processes Regeneration
Replacement of cells with the same kind of cells
Fibrosis Replacement of cells with Dense
Connective Tissue, or scar tissue Depends on type of cells damaged and
what type of injury took place
Tissue Repair Damaged tissue brings a series of events
into motion:Capillaries become permeable
Allows clotting proteins to enter damaged area to stop blood loss and ‘wall off’ the damaged area
This prevents bacteria or other harmful materials from entering
Tissue RepairGranulation tissue forms
Delicate pink tissue, full of tiny capillaries that bleed freely when damaged (picking a scab)
Contains phagocytes to dispose of the clot and collagen making fibroblasts that synthesize scar tissue to permanently fix the gap
Tissue Repair Surface epithelium regenerates
Newly made epithelial cells grow just under the scab, which will fall off
Leaves new surface over scar tissue. Scar may be visible, as a white line, or
invisible depending on the wound severity
Which Tissues Repair Themselves? Regenerate Well
EpithelialFibrous Connective & BoneSmooth Muscle
Regenerate Poorly (surgical)Skeletal MuscleCartilage
No Regeneration (all scar)Nervous TissueCardiac Muscle
Cancer 50% of Americans will have cancer at one point
in their life 20% of Americans will die from cancer A group of >100 diseases All involve uncontrolled proliferation of cells The process begins with one cell that is mutated
and begins to grow uncontrollably Each daughter cell produced will carry the same
trait for uncontrolled cell division
Cancer These cells will form a tumor:
in situ – within the original tissue invasive – within nearby tissue
Many in situ tumors are benign, not harmful, and can be surgically removed.
All invasive tumors and some in situ tumors are considered malignant, dangerous.Malignant tumors are likely to metastasize,
spread to other parts of the body and establish new tumors
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