BIO 1140 Chapter Notes - Chapter 39: Nervous Tissue, Proteoglycan, Muscle Tissue

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1. 39.2(a) Epithelial Tissue Forms Protective, Secretory, and Absorptive
Coverings and Linings of Body Structures
Epithelial tissue: tissue formed of sheet-like layers of cells that are usually joined tightly together, with
little extracellular matrix material between them.
Protect body surfaces from invasion by bacteria and viruses
Secrete or absorb substances
Cover body surfaces and the surfaces of internal organs
Epithelium of the external surface of arthropods secretes their tough cuticle
Scales, nails, claws, hooves, horns, hair and feathers
Epithelia that line the capillaries…
Act as filters
Allow ions and small molecules to leak from the blood into surrounding tissues; allow passage
of blood cells and proteins
Apical surface: the outer surface of epithelial cells.
May be exposed to water, air, or fluids within the body
Move fluids through the cavity/duct
Covered with cilia that move eggs from the ovaries to the uterus
Basal surface: the inner surface of epithelial cells.
Adhered to a layer of ECM secreted by the epithelial cells called the basal lamina: a membrane
secreted at the inner surface of epithelial cells
The entire assemblage is the basement membrane: membrane at the inner surface of epithelia
in vertebrates; consists of the basal lamina and a layer of connective tissus
Types of Epithelia
Simple – formed by a single layer of cells
Stratified – formed by multiple cell layers
Shapes of cells within the epithelium…
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Squamous – mosaic, flattened, spread out
Cuboidal – shaped roughly like dice or cubes
Columnar – elongated, with the long axis perpendicular to the epithelial layer
Some types of epithelia divide constantly to replace worn and dying cells …
Those forming the skin and lining of the intestine (need to constantly be replaced)
New cells are produced through division of stem cells (undifferentiated cells)
oAdult stem cells found in tissues of the brain, bone marrow, blood vessels, skeletal
muscle, and liver
oTotipotent cells have the capacity to form an entire organism
Glands formed by epithelia…
Epithelia typically contain or give rise to cells specialized for secretion
Epithelial cells form glands
Gland: a cell or group of cells that produces and releases substances nearby, in another part of
the body, or to the outside
Exocrine gland: a gland that is connected to the epithelium by a duct and that empties its
secretion at the epithelial surface – mucus, saliva, digestive enzymes, sweat, earwax, oils, milk,
venom…
Endocrine glands: any of several ductless secretory organs that secrete hormones into the
blood or extracellular fluid; may not be composed of epithelial cells – products are hormones
Some glands contain both exocrine and endocrine elements (e.g. pancreas secretes pancreatic
juice and also releases hormones insulin and glucagon)
Some epithelial cells contain a network of fibers of keratin, a family of tough proteins
(fingernails, scales of fish and reptiles, shells of turtles)
2. 39.2(b) Connective Tissue Supports Other Body Tissues
Connective tissue: tissue with cells scattered through an extracellular matrix; forms layers in and
around body structures.
Support other body tissues
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