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Tissue
is a collection of similarcells that performs a general function
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4 Primary types of Tissues
Epithelial: cover and line body organs and form the glands.
Connective: connect between other tissues, support the shape and integrity of organs, transport substances, and protect soft structures.
Muscle: provide movement.
Nervous: manage homeostasis by rapid communication
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Epitheluim
Composed of close-fitting cells often bridged together, allowing little or no blood vessels through (= avascular). Includes two main types: covering and lining epithelium and glandular epithelium.
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2 major functions of epithelium tissue
Protection: epithelium forms a sheet-like barrier.
Control of permeability: forms a filter, allowing selective movement of substances.
Secretion: some cells secrete products.
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Desmosomes
lock cells together byprotein and intercellular “glue”
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Tight junctions
fuse the cell membranes of two adjacentcells together
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Gap Junction
connect two cells by channel proteins, establishing a tube-like bridge
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Covering and Lining Epithelium
- Forms a sheet-like covering orlining.
- It is categorized based on
- 1) shape of its cellsand
- 2) number of cell layers.
- The sheet of cells lieupon a layer of protein, called the basement membrane.
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Simple squamous epithelium
- Flattened cells arranged in a single layer.
- All cells contact the basement membrane.
- Often located where diffusion must occur.
Examples: lining of blood vessels and lymphatic vessels,walls of capillaries, walls of alveoli, lining of body cavities.
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Simple cuboidal epithelium
- Single layer of cube-shaped cells
- All cells contact the basement membrane
- Often forms a small tube, or duct, carrying fluids.
- Cells may contain cilia or microvilli on their apical surface.
Examples: forms ducts in the kidneys, liver, andassociated with glands.
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Simple columnar epithelium
- Single layer of elongated column-shaped cells.
- Each cell contains a nucleus located near the basement membrane.
- Cells may include microvilli along their apical surface.
Example: lines digestive tract.
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Stratified squamous epithelium
- Multiple layers of cells that become flattened as they approach the apical surface.
- Basal layer of cells are columnar or cuboidal in shape.
- Serves as a protective, almost impermeable barrier.
Examples: forms the outer layer of the skin, lines penetrations through the body surface such as the digestive tract and upper respiratory tract.
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Pseudostratified columnar epithelium
- Appears to be multiple layered but is not.
- All cells contact the basement membrane; therefore it is a simple epithelium.
- Cells often include cilia along the apical surface.
- The cilia beat rhythmically to form a conveyor belt of mucus. Abbreviated PSCC epithelium.
- Forms an importantprotective barrier.
Example: lines thetrachea and bronchi
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Transitional epithelium
- Multiple-layered arrangement of cube-shaped cells
- Cells have capacity to expand and shrink in size, similar to crepe paper.
- This gives the tissue the ability to stretch and contract back.
Example: lines the urinary bladder and ureter, enabling these organs to expand and contract with changing fluid volumes.
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Glandular Epithelium
Consists of closely packed cells that are specialized tosecrete a product to form glands.
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2 groups of glandular epithelium
- Exocrine glands: secrete products into ducts that open
- onto body surface or within body cavities
- Endocrine glands: secrete products, called hormones, into the
- extracellular space, where it diffuses into bloodstream.
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Connective Tissue
- Composed of relatively few cells suspended in an intercellular soup of cell products.
- Most abundant tissue in the body; includes tendons, ligaments, bone, cartilage, and blood.
- Functions in:
- -Support
- -Protection
- -Communication
- -Storage
- -Blood cell production
- -Repair
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Connective tissue cells produce and secrete the intercellular material, composed of
Ground substance = sugar-protein molecules in a watery medium
Matrix of protein fibers = collagen, elastin, and reticulin.
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Connective Tissue Proper
- Present throughout the body, between and within most organs.
- Intercellular material is produced by cells called fibroblasts.
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Loose connective tissue (areolar tissue)
- Intercellular material is a thickened fluid, made thick by a loosely arranged matrix of all 3 types of protein fibers.
- Cells include:
- -Fibroblasts
- -White blood cells, including macrophages
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Adipose Tissue
Specialized for energy storage in the form of fat.
Dominated by cells = adipocytes, which contain a large droplet of lipid in the cytoplasm.
Functions in energy storage, insulation, and padding.
Example: most abundant in the superficial fascia, where it is called subcutaneous fat.
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Dense Connective Tissue
Consists of a dense intercellular substance, composed of a matting of protein fibers packed tightly together; mostly collagen fibers.
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Dense Irregular connective tissue
- Fibers are not parallel, but branch to form a dense matting.
- Little ground substance.
- Fibroblasts are squeezed between bundles of collagen.
Example: main component of the skin’s dermis; forms scar tissue
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Dense Regular Connective tissue
Fibers are in parallel arrangement.
Collagen is so dense it allows almost no ground substance.
Fibroblasts are squeezed between collagen bundles.
Example: forms tendons (attach bone to muscle) and ligaments (attach bone to bone)
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Cartilage
- A hard connective tissue with flexibility. The hard quality is provided by a dense matrix of protein fibers within a thickened ground substance. Its density prevents intrusion of blood vessels.
- Its cells, called chondrocytes, lie embedded in chambers called lacunae.
- Nourishment is possible by way of an outer layer of dense connective tissue called the perichondrium and the diffusion of substances through the ground substance.
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Hyaline Cartilage
○Most abundant cartilage; firm and supportive.
○Blueish-white, almost opaque
- ○Collagen fibers not visible due to dense ground
- substance.
- ○Ground substance composed of large carbohydrate
- molecules called chondroitin sulfate, and glycoproteins.
- ○Examples: forms the template of bones, covers bone
- surfaces where they form joints, in respiratory tract (larynx, trachea,
- bronchi), in ribcage, in the nose.
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Elastic Cartilage
- ○Elastic fibers
- visible as dark lines branching throughout the matrix, giving it elastic
- qualities.
- ○Ground substance not
- as dense as in hyaline cartilage.
- ○Example: ears,
- epiglottis.
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Fibrocartilage
- ○Matrix contains
- visible bundles of collagen.
- ○Chondrocytes within lacunae in
- clusters between collagen bundles.
- ○Example:
- shock-absorbing, slightly flexible cushion within some joints, including intervertebral discs and pubic symphysis
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Bone
- Known for its hard, durable features, it provides a structural frame for the body and a muscle attachment site.
- It is also called osseous tissue, and functions in protection, support, and blood cell formation.
- Bone matrix is composed of collagen fibers and a mineralized ground substance.
- The bone cells, called osteocytes, are mainly isolated within chambers called lacunae, and obtain nutrients through tiny fissures through the ground substance from an outer membrane called the periosteum.
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Compact Bone
Densely packed matrix laid down in concentric layers called lamellae.
Osteocytes in lacunae are sandwiched between lamellae and communicate with each other and a central osteonic canal by way of fissures called canaliculi.
The cylindrical arrangement is called an osteon (haversian system).
Forms the outer layer of all bones.
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Spongy Bone
- ○Matrix is arranged to
- form small thin plates that form an interbranching network called trabeculae.
- ○Osteocytes within lacunae may
- be found in each plate, surrounded by solid matrix.
- ○Between the plates is
- a soft, blood-forming tissue called red marrow.
- ○Found along the
- inside surface and fills the ends of most bones.
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Fluid Connective tissue
Some connective tissues include a matrix with a ground substance that is in the liquid state with dissolved proteins. It also includes living cells. It functions in transportation of substances.
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Blood
- ○The liquid ground substance is plasma,
- and the cells include red blood cells, white blood cells, and platelets.
○Found within blood vessels and the heart.
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Lymph
- ○The liquid ground substance is lymph, and the cells
- include white blood cells (only).
- ○Found within lymphatic vessels and other lymphatic
- organs (spleen, thymus, lymph nodes, tonsils, etc.).
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Muscle Tissue
- Composed of cells
- specialized to contract, or shorten in length.
- The result of
- contraction is the production of movement and heat.
- The cells are tightly
- packed; there is little or no intercellular material between cells.
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3 types of muscle tissue
Skeletal muscle tissue: attached to bones and produces body movement. Cells have striations, and can respond to conscious control. Cells are very long, forming muscle fibers.
- Smooth muscle tissue: in the walls of hollow visceral organs, such as digestive tract organs, bronchioles, blood
- vessels. Cells are not striated, and do not respond to conscious control. Cells are short and spindle-shaped.
- Cardiac muscle tissue: in the walls of the heart. Cells are striated, but do not respond to conscious control.
- Cells are short and block-shaped.
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Nervous Tissue
- Composed of cells
- specialized to either conduct an electrochemical signal or support cells that
- conduct.
- Cells are capable of
- excitability and conductivity.
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2 cell types of nervous tissue
- Neurons - excitable and conduct impulses. Each includes a central cell body, and
- extensions known as dendrites and axon.
- Neuroglia – supportive cells; 90% of nervous
- tissue.
- Form the brain,
- spinal cord, and peripheral nerves; also contribute to sensory organs.
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Membrane
- The simplest combination of 2 or more types of tissues. Membranes structurally divide body compartments, line
- cavities, and cover visceral organs.
- They provide protection and convey blood vessels, lymphatics, and nerves. Usually consist of a superficial layer
- of epithelium and a deep layer of connective tissue proper.
(4 types)
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Cutaneous Membrane
- Also known as the skin, it consists of an outer layer of
- epithelium (simple squamous ep.) and an inner layer
- of connective tissue (dense irregular c.t.).
- Covers the body to form the surface, providing an
- important protective barrier.
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Serous Membrane
- Line the internal surfaces of the thoracic and abdominopelvic cavities and form
- the outer layer of many visceral organs.
- A thin layer of simple squamous ep.
- with a basement membrane of loose c.t.
- Cells secrete a watery lubricating fluid known as serous
- fluid.
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Mucus Membrane
- Line the internal surfaces of body openings and internal
- channels (digestive tract, respiratory tract, reproductive tract). Lubricate and protect.
- A layer of epithelium, often simple columnar or
- stratified squamous ep., with a basement
- membrane of loose c.t.
- Mucus cells within the epithelium secrete mucus, which
- lubricates and protects.
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Synovial Membrane
- Line the inside wall of cavities surrounding certain
- joints, such as the elbow, knee, and shoulder.
- Lack epithelium; contains cells that secrete synovial
- fluid to provide lubrication of the joint.
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