Groups of specialized cells that are similar in structure and that perform common functions.
Four major types of Tissues:
epithelial, connective, muscle and nervous
consist of sheets of cells that line r cover various surfaces and body cavities. often they are smooth to reduce friction; the smooth tissue lining your blood vessels helps blood flow more easily through your body, highly specialized for transporting materials. absorb water and nutrients across your intestines into your blood also secret waste products across the tubules of your kidneys so that you can eliminate them in urine.
are epithelial tissues that specialized to synthesize and secrete a product.
secrete their products into a hollow organ or duct. (ex. are the glands in your mouth that secrete saliva, sweat glands in your skin, and glands in your stomach that produce digestive acid.
secrete substances called hormones into the bloodstream. one gland is the thyroid gland, which secretes several hormones that help regulate your body's growth and metabolism.
consists of one or more layer of flatted cells, forms the outer surface of the skin and lines the inner surfaces of the blood vessels, lungs, mouth, throat and vagina.
is composed of the cube-shaped cells. forms the kidney tubules and also covers the surfaces of the ovaries.
is composed of tall, rectangular (column-shaped) cells. lines parts of the digestive tract , certain reproductive organs, and the larynx. Certain cells within this epithelium , called goblet cells, secret mucus, a thick fluid that lubricates the tissues and traps bacteria, viruses and irritating particles.
is a single layer of cells. So thin that molecules can pass through it easily
consists of multiple layers (or strata), thicker and provides protection for underlying cells.
directly beneath the cells of an epithelium tissue is a supporting noncellular layer, and beneath that is generally a layer of connective tissue. composed primarily of protein secreted by the epithelium cells, and although noncelluar, it is a cellular membrane that is a part of every living cell.
epithelium cells may be connected to each other may several different types of these, made up of various proteins. these may hold the cells together, depending of the type of epithelium tissue.
seal the plasma membranes of adjacent cells so tightly together that nothing can pass between the cells. these are particularly important in epithelium layers that must control the movement of substances into or out of the body.(ex. the cells that line the digestive tract, and the bladder, and the cells that form the tubules of the kidneys.
sometimes called "spot desmosomes" are looser in structure. The protein filaments of these structures allow for some movement between cells so that the tissues can stretch and bend. these in the epithelium in your skin allow you to move freely.
represent connecting channels made of proteins that permit the movement of ions or water between two adjacent cells. they are commonly found in the epithelium cells in the liver, heart, and some muscle tissues.
supports the softer organs of the body against gravity and connects the parts of the body together. it also stores fat and produces the cells of blood.
is synthesized by connective tissue cells and released into the space between them. the strength of connective tissue comes from this, not from living cells themselves.
Fibrous connective tissues
connect the various body parts, providing strength, support and flexibility.
made of protein, confer strength and are slightly flexible.
made primarily of the protein elastin, which can stretch without breaking.
connective tissue also contains thinner fibers of collagen that interconnect with each other. often serve as an internal structural framework for some of the "soft" organs such as liver, spleen, and lymph nodes.
consisting of water, polysaccharides,and proteins that ranges in consistency from gel-like to almost rubbery. contains several types of cells, among them fat cells, mast cells, various white blood cells (macrophages, neutrophils, lymphocytes, and plasma cells).
are the cells responsible for producing and secreting the proteins that compose the collagen, elastic, and reticular fibers.
Loose connective tissue
also called areolar connective tissue, is the most common type. it surrounds many internal organs, muscles and blood vessels. this contains a few collagen fibers and elastic fibers in no particular pattern, giving it a great deal of flexibility but only a modest amount of strength.
Dense connective tissue
found in tendons, ligaments, and lower layers of skin, has collagen fibers. the fibers are oriented primarily in one direction, especially in the tendons and ligaments in and around our joints. is the strongest connective tissue when pulled in same direction as the orientation of the fibers, but it can tear if the tear if the stress comes from the side. There are very few good blood vessels in dense connective tissue to supply the few living cells. this is why, if you strain a tendon or ligament, it can take a long time to deal.
Elastic connective tissue
surrounds organs that have to change shape or size regularly. Examples include the stomach, which must stretch to accommodate food; the bladder, which stretches to store urine; and the vocal cords, which vibrate to produce sounds. Elastic connective tissue contains a high proportion of elastic fibers, which stretch and recoil easily.
Reticular connective tissue
(also called lymphoid tissue) serves as the internal framework of soft organs such as the liver and the tissues of the lymphatic system (spleen, tonsils, and lymph nodes) it consists of thin, branched reticular fibers (composed of collagen) that form an interconnected network.
is the transition tissue from which bone develops. it also maintains the shape of certain body parts (such as the tip of your nose) and protects and cushions joints.
is a specialized connective tissue that contains only a few living cells. Most of the matrix of bone consists of hard mineral deposits of calcium and phosphate. however, contains blood vessels, and for this reason it can heal within four to six weeks after being injured.
consists of cells suspended in fluid matrix called plasma. it considered a connective tissue because all b
is highly specialized for fat storage. it has few connective tissue fibers and almost no ground substance. Most of its volume is occupied by adipocytes (fat cells). located primarily under the skin, where it serves as a layer of insulation. it also forms a protective layer around internal organs such as the kidneys.
consists of cells that are specialized to shorten, or contract, resulting in movement of some kind. is composed of tightly packed cells called muscle fibers.
fibers are generally long and thin and aligned parallel to each other. The cytoplasm of this contains proteins, which interact to make the cell contract. Three types of these fibers.
Skeletal muscle tissue
connects to tendons, which attach to bones. when these muscles contract, they cause body parts to move. The individual fibers are thin cylinders too small to be seen with the naked eye, but they may be as long as the entire muscle.
Cardiac muscle tissue
is found only in the heart. the individual cells are much shorter than skeletal muscle fibers, and they have only one nucleus .
Smooth muscle tissue
surrounds hollow organs and tubes, including blood vessels, digestive tract, uterus, and bladder. these slim cells are much smaller then skeletal muscle cells and have only one nucleus like cardiac muscle.
consists primarily of cells that are specialized for generating and transmitting electrical impulses throughout the body. it forms a rapid communication network for the body. this is located in the brain, the spinal cord, and the nerves that transmit information to and from various organs.
Nervous tissue cells that generate and transmit electrical impulses. these can be as long as the distance from your spinal cord to the tip of your toe.
Three parts of neurons: 1. the cell body
where the nucleus is located in a neuron.
Three parts of neurons: 2. dendrites
numerous cytoplasmic extensions that extend from the cell body and receive signals from other neurons
Three parts of neurons: 3. axon
a long extension that transmits electrical impulses over long distances. `
nervous tissue also includes another type of cell that does not maintain electrical impulses, plays a supporting role by surrounding and protecting neurons and supplying them with nutrients.
are structures composed of two or more tissue types joined together that perform a specific function or functions.
are groups of organs that together serve a broad function that is important to survival either of the individual organism (such as respiration, movement, or excretion of wastes) or of the species (reproduction).
consisting of a layer of epithelial tissue and a layer of connective tissue line each body cavity and form our skin. There are four major types of these.
line and lubricate body cavities to reduce friction between internal organs.
line the airways, digestive tract, and the reproductive passages. Goblet cells within the epithelial layer secrete mucus, which lubricates the membrane's surface and entraps foreign particles.
Line the very thin cavities between bones in movable joints. these membranes secrete a watery fluid that lubricates the joint.
our outer covering, the skin. and it serves several functions.
less numerous cells located near the base of the epidermis produce dark-brown pigment called melanin.
accumulates inside keratinocytes and protects us against the sun's ultraviolet radiation. exposure to sunlight increases the activity of melanocytes, accounting for the ability of some people to develop suntan. because all humans have about the same number of melanocytes, racial differences in skin color reflect either differences in melanocyte activity or differences in the rate of breakdown of melanin once it is produced.
protection from dehydration (helps prevent our bodies from drying out), protection from injury (such as abrasion), defense against invasion by bacteria and viruses, regulation of body temperature, synthesis of an inactive form of vitamin D, sensation: provides information about the external world via receptors for touch, vibration, pain, and temperature.
the outer layer of the skin's epithelial tissue
inner layer of connective tissue in the skin
consisting of loose connective tissue containing fat cells, it is flexible enough to allow the skin to move and bend, the fat cells insulate against excessive heat loss and cushion against injury.
which produce a tough, waterproof protein called keratin.
actively dividing keratinocytes located near the base of the epidermis.
Each hair has a shaft above the skin's surface and a root below the surface. Hair is actually composed of several layers of cells enclosed in an outer layer of overlapping, dead, flattened keratinocytes. The root hair is surrounded by a sheath of several layers of cells called the follicle. The cells at the very base of the follicle are constantly dividing to form the hair root. As new hair cells are formed at the base, the hair root is pushed upward toward the skin's surface.
attached at the base of the hair follicle, it contracts when you are frighted or cold, causing your hair to become more erect.
Also known as oil glands, these secrete an oily fluid that moistens and softens hair and skin.
these produce sweat, a watery fluid containing dissolved ions, small amounts of metabolic wastes, and an antibiotic peptide called dermicdin. Sweat helps regulate body temperature and protects against bacteria.
These supply the cells of the dermis and epidermis with nutrients and remove their wastes. These also help regulate body temperature, they dilate to facilitate heat loss when we are too hot and constrict when we are too cool. The dermis also contains lymph vessels, which drain fluids and play a role in the immune systems.
Sensory nerve endings
These provide information about the outside environment. Separate receptors exist to detect heat, cold, light touch, deep pressure, and vibration.