Cell Types &

Tissues

Chapter 3

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

Simple Squamous Epithelia

Stratified Squamous

Connective TissueConnective Tissue

Stratified Squamous Epithelia

Stratified Squamous Epithelia

Simple Cuboidal Epithelia

Simple Columnar Epithelia

Pseudostratified Columnar

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

Bone

Hyaline Cartilage

Stratified Squamous Epithelia

Hyaline Cartilage

Fibrocartilage

Elastic Cartilage

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

Areolar

Adipose

Reticular Connective Tissue

Dense Regular Connective

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

Blood

Blood

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

Skeletal Muscle

Skeletal Muscle

Skeletal Muscle

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

Cardiac Muscle

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

Smooth Muscle

Connective Tissue

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

Nervous Tissue

Nervous Tissue

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

Cancer Growth Model