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tissue
group of similar cells with a common embryological origin that do specialized tasks
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four types of tissue
- Epithelial
- Connective
- Muscle
- Nervous
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Epithelial
- Covers body surfaces
- lines hollow organs, body cavities, & ducts; forms glands
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cell junctions
points of contact between adjacent plasma membranes
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tight
Form fluid tight seals between cells
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anchoring
Fasten cells to one another or to the extracellular material
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gap
Permit electrical or chemical signals to pass from cell to cell
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three types of cell junctions
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epithelial tissue characteristics
- 1. Apical surface is the exposed surface
- 2. Basal surface is attached to the basement membrane, which is composed of a: Basal lamina which is formed from secretions from the epithelium & the reticular lamina which is formed from connective tissue secretions
- 3. avascular (no blood vessels)
- 4. innervated (has nervous tissue)
- 5. high mitotic rate
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types of epithelial
- simple
- stratisfied
- pseudostratisfied
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simple epithelial
single layer of cells
- squamous
- cuboidal
- columnar
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stratisfied
multiple layers of cells, but classified by the top layer
- squamous
- cuboidal
- columnar
- transitional
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pseudostratisfied
single layer of cells, but due to the placement of the nuclei, it looks like its stratisfied
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glandular epithelium
- exocrine glands
- endocrine glands
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exocrine glands
ducted glands leading to an epithelial surface
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types of exocrine glands
- holocrine gland
- merocrine gland
- apocrine gland
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holocrine gland
Epithelial cells lining the gland accumulate the secretory product inside, die, & are secreted as a whole unit - sebaceous(oil) gland of the skin
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merocrine gland
Exocytotic release of secretory product- salivary & most sweat
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apocrine gland
Release via the pinching off(budding) of the apical surface of the epithelial cell
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endocrine glands
ductless glands; the secretory products are secreted into the extracellular matrix & diffuse into the blood stream
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connective tissue
characteristics
- 1. Made up of cells, ground substance, & fibers
- 2. innervated
- 3. vascularized
- 4. The matrix is composed of the ground substance (glue) + fibers; matrix can vary in its consistency - fluid, gelatinous, calcified
- 5. The matrix is derived from secretions from both the CT cells & adjacent cells
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connective tissue
composition-cells
- 1. Fibroblasts- matrix secreting cells for loose & dense CT
- 2. Osteoblasts- matrix secreting cells in bone
- 3. Chondroblasts- matrix secreting cells in cartilage
- 4. Adipocytes- fat cells for insulation & energy
- 5. Macrophages- phagocytes
- 6. Plasma cells - antibody production
- 7. Blood cells- red & white
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connective tissue
composition-ground substance
- 1. Hyaluronic acid - binds cells together, joint lubrication
- 2. Chondroitin sulfate & keratan sulfate - support & adhesiveness in cartilage, bone, blood vessels
- 3. Dermatan sulfate - support & adhesiveness in skin
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connective tissue
composition-fibers (matrix)
- 1. Collagen fibers - collagen protein; typically occur in bundles; bone, cartilage, tendons, & ligaments
- 2. Elastic fibers - elastin protein; freely branching; skin, blood vessels
- 3. Reticular fibers - collagen + glycoproteins; branching, supporting network of many organs
EMBRYONIC CT
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Mesenchyme
composed of mesenchymal cells & reticular fibers; forms all other kinds of CT
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Embryonic connective tissue
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Mucous CT
fibroblasts & collagen fibers; found in the fetus
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Mature CT
Loose CT
- Areolar CT
- Adipose
- Reticular CT
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Areolar CT
composed of a variety of cell types along with all types of fibers; it provides strength, elasticity, & support
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adipose tissue
composed of adipocytes; it provides insulation, energy, support, & protection; subcutaneous layer of the skin, yellow marrow of long bones
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reticular CT
composed of reticular cells & reticular fibers; forms the stroma(framework) of organs, binds smooth muscle cells
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Mature CT
Dense CT
- Dense regular CT
- dense irregular CT
- elastic CT
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dense regular CT
- composed of fibroblasts & bundles of collagen fibers;
- provides strong attachments between various structures;
- tendons (muscle to bone), ligaments (bone to bone)
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dense irregular CT
composed of fibroblasts & randomly arranged collagen fibers; it provides strength; found in membrane capsules around organs
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elastic CT
composed of fibroblasts & elastic fibers; allows stretching of organs
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mature CT- Cartilage
Characteristics
- 1. Composed of a dense network of collagen & elastic fibers embedded in chondroitin sulfate
- 2. Collagen gives cartilage its strength
- 3. Chondroitin sulfate gives cartilage its resilience
- 4. Cells of mature cartilage are called chondrocytes & they are located in spaces called lacunae
- 5. Surface of most cartilage is surrounded by the perichondrium, a layer of dense, irregular CT
- 6. Cartilage has no blood vessels or nerves except for those in the perichondrium
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three types of cartilage
- hyaline cartilage
- fibrocartilage
- elastic cartilage
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Hyaline Cartilage
composed of thin collagen fibers that are not visible and the standard chondrocytes in lacunae
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fibriocartilage
composed of bundles collagen fibers that are visible and the standard chondrocytes in lacunae
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elastic cartilage
composed of elastic fibers that are visible and the standard chondrocytes in lacunae
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Mature CT-Bone
Characteristics
- 1. Bone tissue is classified as either compact or spongy
- 2. The basic unit of compact bone is the osteon or Haversian system
- 3. It is comprised of a central (Haversian) canal that contains blood vessels & nerves
- 4. Surrounding the canal are lamellae, which are concentric rings of calcified matrix which are secreted by osteoblasts which form the bone.
- 5. The osteoblasts mature into osteocytes which are now embedded between the lamellae in spaces called lacunae, which are analogous to cartilage lacunae
- 6. The lacunae are connected by channels called canaliculi, which allow nutrients & wastes to be transported into & out of the bone.
- 7. Spongy bone do not possess osteons, but trabeculae, which are columns of bone containing lamellae, ostecocytes, lacunae, & canaliculi - no central canal
- 8. Bone provides support, protection, movement, & houses blood forming tissue
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Mature CT-Blood
Characteristics
- 1. Blood is a CT with a liquid matrix called plasma, which is
- composed of water & dissolved solutes
- 2. Erythrocytes are red blood cells necessary for the transport of oxygen & carbon dioxide
- 3. Leukocytes are white blood cells which provide immunity
- 4. Platelets function in blood clotting
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epithelial membranes
characteristics
- 1. Epithelial membranes are composed of an epithelial layer & an underlying layer of CT
- 2. The principal epithelial membranes are mucous & serous
- 3. Mucous membranes (mucosa) line body cavities that are exposed to the exterior (examples are digestive and respiratory tracts), providing a barrier to infection, lubrication, and even enzymes for chemical reactions
- 4. Serous membranes (serosa) line body cavities that are not exposed to the exterior & cover the organs within the cavities
- 5. The mesothelium of the serosa secretes serous fluid, providing lubrication so that the organs can easily glide against one another.
- 6. The serosa can be divided into the parietal layer which lines the cavity, the visceral layer which covers the organs
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Skeletal Muscle
- 1. Attached to bones by tendons
- 2. They are striated- alternating light & dark bands of structures within the cells
- 3. It is voluntary, since its contractions are under conscious control
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Cardiac Muscle
- 1. Forms the bulk of the heart wall
- 2. They are striated - alternating light & dark bands of structures within the cells
- 3. It is involuntary, since its contractions are not under conscious control
- 4. Cardiac muscle fibers are connected to one another at their ends by thickenings of the plasma membrane, called intercalated discs
- 5. The intercalated discs contain both adhering & gap junctions
- 6. The gap junctions allow electrical impulses to move rapidly through the heart, providing a smooth continuous contraction that is necessary for pumping blood
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Smooth Muscle
- 1. It is located in the walls of hollow organs (blood vessels, digestive tract)
- 2. They are not striated, involuntary, & some possess gap junctions
- 3. They provide for involuntary movement of material & mixing
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Nervous Tissue
- 1. Nervous tissue is composed of two cell types: neurons & neuroglia
- 2. Neurons are the structural & functional units of the nervous system. They respond to stimuli & control the body to react to that stimuli.
- 3. Structurally the neuron is composed of a cell body, dendrites (specialized structures that receive & conduct nerve impulses (information) to the cell body, & an axon (which conveys the information to the next cell)
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- Neuroglia are support cells that maintain proper neuron functions
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