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TYPES OF TISSUE
There Are 4 Different Tissue Types:
Epithelial tissue are sheets of cells that cover a body surface or lines a body cavity. There are 8 different types of epithelial tissue defined by their shape ("squamous" or "cuboidal") and arrangement ("simple" or "stratified"); their functions vary.
- Simple squamous epithelium: e.g., lining of lung alveoli, blood vessels, and lymphatic vessels.
- Stratified squamous epithelium: e.g., lines esophagus, mouth, vagina.
- Transitional epithelium: lines the bladder, urethra, and ureters. It is a type of stratified epithelium which can distend, and the word "transitional" refers to its degree of distention.
- Simple cuboidal epithelium: in ducts, secretory parts of small glands, and kidney tubules.
- Stratified cuboidal epithelium: sweat glands, salivary glands, mammary glands.
- Simple columnar epithelium: ciliated tissues like the bronchi, fallopian tubes, and smooth tissue in the digestive tract or bladder. Secretes mucous and enzymes.
- Pseudostratified columnar epithelium: ciliated tissues lining the trachea and upper respiratory tract. Secretes mucus; cilia move mucus up for removal.
- Stratified columnar epithelium: male urethra, ducts of some glands.
Connective Tissue (CT)
Connective tissue is the most abundant and widely distributed of the primary tissues. It is tissue that binds and supports, protects, insulates, stores reserve fuel, and transports substances within the body. It is made up of cells and extracellular substances ("ground substance" and fibers that make up the extracellular matrix).
Connective tissue includes:
- Bone--richly supplied vascular.
- Dense and loose connective tissue, including fat, tendons, ligaments, CT in the dermis, etc.
Muscle tissue is soft tissue that contracts. Three types:
- Striated muscle--voluntary skeletal muscles, anchored by tendons to bone, for locomotion and other actions. It has functional units called sarcomeres as series of bands ("striations"). Contracts/relaxes in short, intense bursts.
- Smooth muscle--non-striated and not under voluntary control; found in esophagus, stomach, intestines, bronchi, uterus, urethra, bladder, blood vessels, and erector pili (muscles that stand hair up). Contractions are sustained and nearly continuous. Example: peristalsis.
- Cardiac muscle, striated, but not under voluntary control as it is self-regulated. The striated nature is of a different structure from skeletal muscles, which includes branching at irregular angles, called intercalated discs.
Nervous tissue is the main tissue component of the two parts of the nervous system:
- Central Nervous System (CNS): the brain and spinal cord.
- Peripheral Nervous System (PNS): the branching peripheral nerves originating as they exit the spinal cord, which regulate and control voluntary activity, transport information on sensation, and allow autonomic bodily functions.
- NEURONS: the "gray matter," cells that propagate electrical signals along bundles called nerves.
Dendrites are the neuron branches that receive signals from a previous neuron; the axon is what sends the signal on to the next neuron.
Nerve fibers are either myelinated (fast--for information important to survival) or un-myelinated (slow) tracts of serially connected neurons. Bundles of myelinated axons make up the "white matter."
- GLIA: non-neuronal cells originating from the immune system, which modulate synapses between/among neurons, coat nerve fibers with insulation (myelin) to speed them up, and help eliminate invaders or the wastes from metabolism.
Somatic nerves: sensory, somatic, and somatosensory nerves.
Somatosensory nerves have dual functioning--voluntary signals and sensation info transport. Somatic nerves include the spinal nerves. --
Autonomic nerves: sympathetic and parasympathetic nerves.