Chapter 5 - Tissues Flashcards
what creates tissue
cells. The combination of different cell types, with similar structures and functions, creates tissue.
The four basic tissue types
epithelial
connective
nervous
muscle
describe: Epithelial tissue
epithelia and glands: covers the surface of the skin and organs forms the inner lining of body cavities lines hollow organs makes up glands
anchored to connective tissue by a ‘basement membrane’
classified according to shape of their cells and number of cell layers
describe: Connective tissue
widely distributed throughout the body, filling internal spaces. Binds, Supports and protects body structures.
describe: Nervous tissue
carry information from one part of the body to another via electrical impulses. found in:
the brain and spinal cord (CNS)
the nerves (PNS)
describe: Muscle tissue
specialised for contraction and include
skeletal muscles(attached to bones, used for movement of the body)
the heart
muscular walls of hollow organs
cardiac (involuntary)
smooth ( involuntary)
Striated (voluntary)
describe: Epithelium
an avascular layer of cells that forms a barrier, providing protection and regulating permeability.
describe: Glands
are secretory structures derived from epithelia
functions of Epithelia - physical protection
abrasion, dehydration, destruction from biologic or chemical agents.
Tightly interlocked epithelial cells of the circulatory system reduce friction between the blood and the walls of the blood vessels.
functions of Epithelia - Absorption
examples of epithelia that absorb or secrete substances are those that line the kidney tubules and intestine. In the intestine certain epithelia absorb nutrients from the digestion of food.
functions of Epithelia - Filtration
Some epithelia have tiny motile cilia that propel substance along free surfaces, as part of filtration. These include epithelia lining the trachea and other air passages.
A thin supporting sheet adjacent to the basal surface of an epithelium is called the ‘basal lamina’, which acts as a selective filter. It determines which molecules can diffuse from underlying connective tissue can enter the epithelium.
functions of Epithelia - Excretion
In the kidneys epithelia excrete waste products and also reabsorb needed material form the urine.
In the skin, the epithelia of sweat glands excrete sweat.
functions of Epithelia - Sensation
Most epithelia are very sensitive to stimulation because they have a large sensory nerve supply. Sensory stimuli penetrate specialised epithelia. Such tissue is found in the eyes, ears, skin, nose and on the tongue.
functions of Epithelia - Specialised secretions
Epithelial cells that produce secretions are called gland cells. Cells of this type are scattered among other cells in an epithelium. Most or all of the epithelial cells in a glandular epithelium produce secretions, which are either discharged onto the surface of the epithelium or released into the surrounding interstitial fluid and blood. These secretions include enzymes, hormones and lubricating fluids.
functions of Epithelia - Permeability
Any substance entering or leaving the body must cross and epithelium, so the epithelia control permeability. Some epithelia are relatively impermeable, whereas others are crossed easily by compounds of various sizes. In response to stimuli, the epithelial barrier may be modified and regulated. Hormones can effect ion and nutrient transport through epithelial cells. Physical stress can also alter the structure and properties of epithelia. An example is the formation of calluses on the hands after repeated manual labour.
