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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
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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
Stratified Squamous Connective Tissue
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
Hyaline Cartilage Stratified Squamous Epithelia
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: • 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
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
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
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