As we saw above, every organ is made up of two or more tissues, groups of similar cells that
work together to perform a specific task. Humans—and other large multicellular animals—are
made up of four basic tissue types: epithelial tissue, connective tissue, muscle tissue, and
nervous tissue.
앞글에서 보았듯이, 모든 기관은 같이 특정 기능을 수행하는 유사한 세포의 그룹인 2개 이상의 조직으로 이루어져
있다. 인간과 기타 거대한 다세포 동물은 4가지 기초조직형으로 이루어져 있다; 상피세포조직,연결세포, 근육세포
신경세포,
Epithelial tissue 상피조직
Epithelial tissue consists of tightly packed sheets of cells that cover surfaces—including the
outside of the body—and line body cavities. For instance, the outer layer of your skin is an
epithelial tissue, and so is the lining of your small intestine. * 빡빡하게 압축된
Epithelial cells are polarized, meaning that they have a top and a bottom side. The apical, top,
side of an epithelial cell faces the inside of a cavity or the outside of a structure and is usually
exposed to fluid or air. The basal, bottom, side faces the underlying cells. For instance, the
apical sides of intestinal cells have finger-like structures that increase surface area for absorbing nutrients.
Epithelial cells are tightly packed, and this lets them act as barriers to the movement of fluids and potentially harmful microbes. Often, the cells are joined by specialized junctions that hold them
tightly together to reduce leaks.
Connective tissue 결합조직
Connective tissue consists of cells suspended in an extracellular matrix. In most cases, the
matrix is made up of protein fibers like collagen and fibrin in a solid, liquid, or jellylike ground
substance. Connective tissue supports and, as the name suggests, connects other tissues.
Loose connective tissue, show below, is the most common type of connective tissue. It's found throughout your body, and it supports organs and blood vessels and links epithelial tissues to
the muscles underneath. Dense, or fibrous, connective tissue is found intendons and ligaments, which connect muscles to bones and bones to each other, respectively. * 힘줄. 인대
Specialized forms of connective tissue include adipose tissue—body fat—bone, cartilage, and
blood, in which the extracellular matrix is a liquid called plasma.