Cell Types & Tissues Chapter 3

What are Tissues?  Tissues are groups of cells that have similar function  There are 4 main tissue types: Epithelial Tissue Connective Tissue Muscle Tissue Nervous 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 Tissue

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 capillaries  Example: 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

Muscle Tissue  Specialized to contract, or shorten  Cells are elongated to provide better contraction  Individual Cells are called fibers  There are 3 types: Skeletal Cardiac Smooth

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 Cylindrical Multinucleate Striated – Striped

Skeletal Muscle

Cardiac Muscle Tissue  Found only in the heart  Cells are Uninucleate Branching Striated  Branches meet at junctions called intercalated disks Allow 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

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 Repair Granulation 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 Epithelial Fibrous Connective & Bone Smooth Muscle  Regenerate Poorly (surgical) Skeletal Muscle Cartilage  No Regeneration (all scar) Nervous Tissue Cardiac 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