By: Abby Reed
Tissues are a collection of specialized cells and cell products that perform a relatively limited number of functions.
There are four types of tissues:
- The Epithelial tissue
- The Connective tissue
- The Muscle tissue
- The Neural tissue.
The first tissue is the Epithelial tissue. It includes the surface of your skin. It provides protection for internal surfaces from abrasion, dehydration, and destruction by chemical or biological agents. It also controls permeability by controlling what enters and leaves your body. Its third function of Epithelial tissue is providing sensation because they have a large sensory nerve supply. These sensory nerves provide information continually about the external and internal environments. It also produces specialized secretions called gland cells. These cells are either discharged onto the surface of the epithelium or released into the surrounding interstitial fluid and blood to act as chemical messengers.It is found throughout the body, covers all body surfaces both inside and out.
The second type of tissue is the Connective tissue. It has six main functions in the body. Such as, establishing a structural framework for the body. As well as transporting fluids and dissolved materials and protecting delicate organs. It also Supports surrounding and interconnecting other types of tissues together. The Connective tissue also stores energy reserves, especially in the form of lipids. Its last function is defending the body from invading microorganisms that would otherwise kill us.It is the most abundant tissue in your body, found throughout
The third type of tissue is the Muscle tissue. Epithelia cover surfaces and line passageways; connective tissues support weight and interconnect the parts of the body. Its first function is the movement of materials along the digestive tract. The second is movement of blood around the cardiovascular system. The last function is the movement of the body from one place to another.They are found in skeletal muscles, in hollow organs, stomach and the wall of the heart.
The fourth and final type of tissue is the nerve tissue. The nervous system has many functions such as, sensory output, integration and of muscles and glands. It also controls homeostasis and mental activity. It is found in the brain and spinal cord.
In the Epithelial tissue there are only two classifications of cells: simple and stratified. Simple epithelium is one cell thick, that is, every cell is in direct contact with the underlying basement membrane. It is generally found where absorption and filtration occur. The thinness of the epithelial barrier facilitates these processes.Simple epithelial tissues are generally classified by the shape of their cells. The four major classes of simple epithelium are: (1) simple squamous; (2) simple cuboidal; (3) simple columnar; (4) pseudo-stratified. The second classification is stratified epithelium, it has several layers of cells that cover the basement membrane. They are generally located in the areas that need protection from mechanical or chemical stresses, such as the surface of the skin and the lining of the mouth.
In the Connective tissue there are three classifications of cells: connective tissue proper, fluid and supporting. Connective tissue proper includes those connective tissues with many types of cells and extra-cellular fibers in a syrupy substance. This category is divided into two classes, (a) loose connective tissue and (b) dense connective tissue. The second classification is Fluid connective tissue. It has a very distinctive population of cells suspended in a watery matrix that contains dissolved proteins There are two types: blood and lymph. The third classification is Supporting connective tissue. It protects soft tissues and support weight of part or all the body. There are two types: cartilage and bone.
In Muscle tissue there is no classification of cells but rather three types of muscle tissue. It includes the skeletal, cardiac, and smooth muscle. Skeletal muscle forms the large muscles responsible for gross body movements and locomotion. Cardiac muscle is only found in the heart, and is responsible for the circulation of blood. Smooth muscle is found in he walls of visceral organs and a variety of other locations. It provides elasticity, contractility, and support.
The Nerve tissue there are two types of cells: neurons and neuroglia. The classification of neurons are grouped structurally according to the number of processes extending from their cell body. Three major neuron groups make up this classification: multipolar, bipolar and unipolar neurons.
Specializations of Epithelia:
There are six types of Epithelial tissue: SIMPLE SQUAMOUS are single layer of very thin, flattened cells. Function: diffusion and filtration. Found in air sacs of lungs, walls of capillaries. SIMPLE CUBOIDAL are single layer, cube-shaped cells. Function: Secretion and absorption. Found: Lining of kidney tubules, ducts of glands, covering surface of ovaries. SIMPLE COLUMNAR are single layer, elongated cells with their nuclei in about the same position in each cell. Its in charge of protection, secretion, absorption. It is found in the lining of digestive tract and uterus It contains scatter goblet cells functioning in the secretion of mucus and some columnar cells have tiny finger-like processes from their free surface called micro-villi. STRATIFIED SQUAMOUS are multi-layered, squamous cells. Thicker tissue. Functions in protection. Found lining body cavities like the mouth and outer layer of skin. PSEUDO-STRATIFIED COLUMNAR appear "stratified" but really a single layer with nuclei at various levels giving the appearance of layered cells. Usually ciliated and contains goblet cells. Function: secretion and cilia-aided movement. Location: lining air passages like the trachea and tubes of the reproductive system.TRANSITIONAL EPITHELIUM are thick, layered cuboidal cells. "Stretchable" tissue, also forms barrier to block diffusion. It is found lining of urinary bladder.