What is a 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...

Maskot / Getty Images Cells Cells are the smallest unit of life. To understand what a cell looks like, picture a chicken egg. It has an outer membrane (in the case of an egg, it's a hard shell, but most cells aren't like that); it's filled with nutrient-rich fluid (whites of the egg versus cytoplasm in a cell) and has a nucleus (egg yolk). Not all cells look alike. Nerve cells are long, thin and covered in myelin, natural insulation. Nerve cells conduct impulses, which are used to communicate. They're basically the telephone wires of the body, and they look the part. Muscle cells are thick and elongated, like live rubber bands. Red blood cells are flat and discoid-shaped. The shapes of the cells help them with their individual functions. Tissues When cells of a certain type are grouped together, the resulting structure is called tissue. There is muscle tissue, which is made of strands of muscle cells. Adipose tissue is a tissue comprised of fat cells (adipocytes). Connective tissue is a term used for various types of tough, fibrous matter like tendons or ligaments.

Synonyms: Epithelium A tissue is a group of There are four basic tissue types defined by their morphology and function: epithelial tissue, connective tissue, muscle tissue, and nervous tissue. • Epithelial tissue creates protective boundaries and is involved in the diffusion of ions and molecules. • Connective tissue underlies and supports other tissue types. • Muscle tissue contracts to initiate movement in the body. • Nervous tissue transmits and integrates information through the Key facts about the tissue types Epithelial Tissue Features - high cellularity, special sensory receptors, forms a barrier, avascular, innervated Surfaces - basal (hemidesmosomes, basement membrane), apical (lumen, microvilli, cilia, stereocilia), lateral (adhering junctions, tight junctions, desmosomes, gap junctions) Types - squamous, cuboidal, columnar, simple, stratified, pseudostratified, specialized Connective Tissue Structure - cells (structural, immunological, defense, energy reservoirs), extracellular matrix (ground substance, protein fibers) Types of fibers - collagen, reticular, elastic Classification - proper (dense, loose), embryonic (mesenchyme, mucous), specialized (cartilage, adipose, bone, blood) Muscle Tissue Features - elastic, extensible, contractile Types - skeletal, cardiac (gap junctions, intercalated discs), smooth, striated, nonstriated Nervous Tissue Neurons - soma, dendrites, axons, ganglia (PNS), nuclei (CNS) Glia - astrocytes, oligodendrocytes, Schwann cells, micr...

/ˈtɪʃu/ Other forms: tissues; tissued Tissue is part of the body of a living thing that is made of similar cells, like the cardiac tissue of your heart. A tissue is also a soft, thin piece of paper used for wiping noses and tear drops. The noun tissue comes from the Old French word tissu, meaning “a ribbon, or belt of woven material.” In fact, as a verb, tissue means "weave fabric strands." Today, we think of tissues as the disposable paper for blowing our noses or packing presents. A different kind of tissue is found in the body — the groups of cells that have the same job, like scar tissue that protects a wound as it heals.

Amanda Robb Amanda has taught high school science for over 10 years. She has a Master's Degree in Cellular and Molecular Physiology from Tufts Medical School and a Master's of Teaching from Simmons College. She is also certified in secondary special education, biology, and physics in Massachusetts. • Instructor Human Body Tissue True or False Activity This activity will help you assess your knowledge of the definition, types, and examples of human body tissue. Directions Determine whether the following statements are true or false. To do this, print or copy this page on a blank paper and underline or circle the answer. 1. The four types of tissue in the body are epithelial, connective, muscle, and nervous. True | False 2. Muscle tissues are bundles of muscle fibers that are arranged in perpendicular lines. True | False 3. Epithelial tissues act as a supporting framework for most organs of the body. True | False 4. The nervous tissue is composed of three main parts: nerves, the spinal cord, and the brain True | False 5. Epithelial tissues are found in body surfaces, line body cavities, and hollow organs. True | False 6. Cardiac muscle tissue is a specialized, organized type of tissue that only exists in the heart and the lungs. True | False 7. The epidermis, or the outermost layer of the skin, is an example of epithelial tissue. True | False 8. Neutrons are cells of the nervous system that conducts nerve impulses. True | False 9. Connective tissues are found in between othe...

Synonyms: Epithelium A tissue is a group of There are four basic tissue types defined by their morphology and function: epithelial tissue, connective tissue, muscle tissue, and nervous tissue. • Epithelial tissue creates protective boundaries and is involved in the diffusion of ions and molecules. • Connective tissue underlies and supports other tissue types. • Muscle tissue contracts to initiate movement in the body. • Nervous tissue transmits and integrates information through the Key facts about the tissue types Epithelial Tissue Features - high cellularity, special sensory receptors, forms a barrier, avascular, innervated Surfaces - basal (hemidesmosomes, basement membrane), apical (lumen, microvilli, cilia, stereocilia), lateral (adhering junctions, tight junctions, desmosomes, gap junctions) Types - squamous, cuboidal, columnar, simple, stratified, pseudostratified, specialized Connective Tissue Structure - cells (structural, immunological, defense, energy reservoirs), extracellular matrix (ground substance, protein fibers) Types of fibers - collagen, reticular, elastic Classification - proper (dense, loose), embryonic (mesenchyme, mucous), specialized (cartilage, adipose, bone, blood) Muscle Tissue Features - elastic, extensible, contractile Types - skeletal, cardiac (gap junctions, intercalated discs), smooth, striated, nonstriated Nervous Tissue Neurons - soma, dendrites, axons, ganglia (PNS), nuclei (CNS) Glia - astrocytes, oligodendrocytes, Schwann cells, micr...

Amanda Robb Amanda has taught high school science for over 10 years. She has a Master's Degree in Cellular and Molecular Physiology from Tufts Medical School and a Master's of Teaching from Simmons College. She is also certified in secondary special education, biology, and physics in Massachusetts. • Instructor Human Body Tissue True or False Activity This activity will help you assess your knowledge of the definition, types, and examples of human body tissue. Directions Determine whether the following statements are true or false. To do this, print or copy this page on a blank paper and underline or circle the answer. 1. The four types of tissue in the body are epithelial, connective, muscle, and nervous. True | False 2. Muscle tissues are bundles of muscle fibers that are arranged in perpendicular lines. True | False 3. Epithelial tissues act as a supporting framework for most organs of the body. True | False 4. The nervous tissue is composed of three main parts: nerves, the spinal cord, and the brain True | False 5. Epithelial tissues are found in body surfaces, line body cavities, and hollow organs. True | False 6. Cardiac muscle tissue is a specialized, organized type of tissue that only exists in the heart and the lungs. True | False 7. The epidermis, or the outermost layer of the skin, is an example of epithelial tissue. True | False 8. Neutrons are cells of the nervous system that conducts nerve impulses. True | False 9. Connective tissues are found in between othe...

Get a Britannica Premium subscription and gain access to exclusive content. The most useful of all systems, however, breaks down The second class of tissues consists of those used in coordination. There are basically two types: physical ( The basic unit of all nervous tissue is the The third class of tissues includes those contributing to the body’s support and A fourth class of tissues includes reproductive tissues, hemopoietic tissues, and tissue fluids. The most important reproductive tissues are the gonads (ovaries and testes), which produce the gametes (eggs and sperm, respectively). Hemopoietic tissues produce the cellular components of the blood. Among the important tissue fluids are lymph, This article was most recently revised and updated by

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...