Tissue

If you were a single-celled organism and you lived in a nutrient-rich place, staying alive would be pretty straightforward. For instance, if you were an amoeba living in a pond, you could absorb nutrients straight from your environment. The oxygen you would need for metabolism could diffuse in across your cell membrane, and carbon dioxide and other wastes could diffuse out. When the time came to reproduce, you could just divide yourself in two! However, odds are you are not an amoeba—given that you're using Khan Academy right now—and things aren’t quite so simple for big, many-celled organisms like human beings. Your complex body has over 30 trillion cells, and most of those cells aren’t in direct contact with the external environment. 1 ^1 1 start superscript, 1, end superscript A cell deep inside your body—in one of your bones, say, or in your liver—can’t get the nutrients or oxygen it needs directly from the environment. Most cells in large multicellular organisms don't directly exchange substances like nutrients and wastes with the external environment, instead, they are surrounded by an internal environment of extracellular fluid—literally, fluid outside of cells. The cells get oxygen and nutrients from this extracellular fluid and release waste products into it. Humans and other complex organisms have specialized systems that maintain the internal environment, keeping it steady and able to provide for the needs of the cells. Different systems of the body carry out di...

Learning Objectives Identify the main tissue types and discuss their roles in the human body. By the end of this section, you will be able to: • Identify the four primary tissue types and discuss the structure and function of each • Describe the embryonic origin of tissue • Identify the various types of tissue membranes and the unique qualities of each The term tissue is used to describe a group of cells that are similar in structure and perform a specific function. Histology is the the field of study that involves the microscopic examination of tissue appearance, organization, and function. Tissues are organized into four broad categories based on structural and functional similarities. These categories are epithelial, connective, muscle, and nervous. The primary tissue types work together to contribute to the overall health and maintenance of the human body. Thus, any disruption in the structure of a tissue can lead to injury or disease. The Four Primary Tissue Types Epithelial tissue refers to groups of cells that cover the exterior surfaces of the body, line internal cavities and passageways, and form certain glands. Connective tissue, as its name implies, binds the cells and organs of the body together. Muscle tissue contracts forcefully when excited, providing movement. Nervous tissue is also excitable, allowing for the generation and propagation of electrochemical signals in the form of nerve impulses that communicate between different regions of the body ( An under...

tissue culture, a method of biological research in which fragments of Historical developments An early attempt at tissue culture was made in 1885 by German zoologist tissue culture and defined the concept. Thereafter, a number of experimenters succeeded in Culture environments Cells may be grown in a To initiate a culture, a tiny sample of the tissue is dispersed on or in the medium, and the flask, tube, or plate containing the culture is then incubated, usually at a temperature close to that of the tissue’s normal environment. Sterile conditions are maintained to prevent contamination with microorganisms. Cultures are sometimes started from single cells, resulting in the production of uniform biological populations called

[ "article:topic", "mucus", "cartilage", "connective tissue", "epithelial tissue", "osteon", "bone", "cardiac muscle", "smooth muscle", "white matter", "gray matter", "authorname:mgrewal", "showtoc:yes", "non-cellular matrix", "fibroblast cells", "collagen fibers", "elastic fiber", "reticular fibers", "loose connective tissue proper", "areoler connective tissue", "reticular connective tissue", "dense connective tissue proper", "dense regular connective tissue", "dense irregular connective tissue", "elastic connective tissue", "hyaline cartilage", "elastic cartilage", "fibrocartilage", "osteoblasts", "blood", "mucous membrane", "muscle tissue", "skeletal muscles", "nervous tissue", "nerves", "Ganglia", "cssprint:dense", "program:oeri", "licenseversion:30", "license:ck12", "source@https://www.ck12.org/book/ck-12-human-biology/" ] \( \newcommand\) • • • • • • • • • • • • • • • • • • • • • • • • • Dust Mop This photo in Figure \(\PageIndex\): Scanning electron microscope image of lung trachea epithelium. There are both ciliated and on-ciliated cells in this epithelium. Note the difference in size between the cilia and the microvilli (on the non-ciliated cell surface) Variation in Human Cells Some cells act as individual cells and are not attached to one another. Red blood cells are a good example. Their main function is to transport oxygen to other cells throughout the body, so they must be able to move freely through the circulatory system. Many other cells, in contrast, act ...