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is a collection of similarcells that performs a general function
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
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.
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.
lock cells together byprotein and intercellular “glue”
fuse the cell membranes of two adjacentcells together
connect two cells by channel proteins, establishing a tube-like bridge
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.
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.
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.
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.
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.
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
- 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.
Consists of closely packed cells that are specialized tosecrete a product to form glands.
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.
- 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:
- -Blood cell production
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.
Connective Tissue Proper
- Present throughout the body, between and within most organs.
- Intercellular material is produced by cells called fibroblasts.
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:
- -White blood cells, including macrophages
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.
Dense Connective Tissue
Consists of a dense intercellular substance, composed of a matting of protein fibers packed tightly together; mostly collagen fibers.
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
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)
- 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.
○Most abundant cartilage; firm and supportive.
○Blueish-white, almost opaque
- ○Collagen fibers not visible due to dense ground
- ○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.
- ○Elastic fibers
- visible as dark lines branching throughout the matrix, giving it elastic
- ○Ground substance not
- as dense as in hyaline cartilage.
- ○Example: ears,
- ○Matrix contains
- visible bundles of collagen.
- ○Chondrocytes within lacunae in
- clusters between collagen bundles.
- shock-absorbing, slightly flexible cushion within some joints, including intervertebral discs and pubic symphysis
- 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.
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.
- ○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.
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.
- ○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.
- ○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.).
- 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.
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.
- Composed of cells
- specialized to either conduct an electrochemical signal or support cells that
- Cells are capable of
- excitability and conductivity.
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
- Form the brain,
- spinal cord, and peripheral nerves; also contribute to sensory organs.
- 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.
- 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.
- 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
- 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.
- 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.