Epithelial, Connective, Muscular, and Nervous
Epithelial tissue is found inside and outside of the body as well as in organs and the lining of certain ducts, tubes, cavities, blood vessels, and glands. Epithelial cells can be classified by both shape, squamous, cuboidal, and columnar, and arrangement, simple and stratified. Simple epithelial tissues are described as being only one cell thick, while stratified epithelial tissues are made of layered stacks of cells. Squamous epithelial cells are flat and resemble scales. Simple squamous tissue lines the blood vessels and the organs and helps with diffusion. Stratified squamous tissue is used for protection and makes up the epidermis. Cuboidal epithelial tissue is cube-shaped. Simple cuboidal tissue is found in the ducts of the kidneys and glands and functions for reabsorption and secretion. Stratified cuboidal tissue aids with protection and secretion and is found in sweat glands. Simple columnar tissue lines the digestive tract and helps with absorption. Stratified columnar tissue is found in the larynx and helps with secretion. There is also pseudostratified columnar tissue which looks like it is layered, but is actually only one cell thick. This type of tissue is usually connected to cilia and helps with movement and secretion. There is also a type of epithelial tissue called transitional epithelium, which has adapted to stretching and changing. This allows transitional tissue to appear simple and stratified depending on the situation.
Epithelial Tissue Form
Epithelial Tissue Function
Connective tissue can also be broken down into categories. The most rigid category is bone, then cartilage, then dense connective tissue, then loose connective tissue, and finally blood. Connective tissue has an extracellular matrix, a non-living ground substance that has living cells in it. Bone functions for protection, support, mineral storage, and blood cell production. There are three different type of cartilage. Hyaline cartilage works to hold respiratory passages open. Elastic cartilage functions for protection. Fibrocartilage prevents bone to bone contact within the body. Dense connective tissue can be broken down into dense regular or dense irregular. Dense regular tissue makes up tendons and ligaments and their fiber bundles all run the same direction. Dense irregular tissue makes up the skin and their fiber bundles run in different directions. Loose connective tissue can be categorized into three different groups. Areolar loose tissue is a loose arrangement of cells and fibers and can be described as mostly an empty space. Areolar tissue cushions organs. Adipose tissue is our body's fat and the cells are oil-filled. They provide protection and energy. Reticular loose connective tissue is a network of fibers and cells that make up lymph nodes, spleen, and internal support systems. Blood is made up of a matrix called blood plasma.
(Source: Module 2 Lesson 1 Guided Notes)
Connective Tissue Form
Connective Tissue Function
There are three different types of muscle, skeletal, smooth, and cardiac. Skeletal muscle is found on the large body bones and is a voluntary muscle, meaning you have to consciously move it. Skeletal muscle is responsible for body movement. Smooth muscle is found in the organ walls and blood vessels and is an involuntary muscle. Smooth muscle is responsible for the movement of blood, food, and waste through the organs and body. Cardiac muscle is found in the walls of the heart and is an involuntary muscle. Cardiac muscle is responsible for the contractions of the heart and, therefore, the heart beat.
(Source: Module 2 Lesson 1 Guided Notes)
Muscular Tissue Form
Muscular Tissue Function
Nervous tissue is found in the brain, spinal cord, and nerves. Nervous tissue generates and transmits nerve impulses to and from body organs via neurons, the largest cells in our body (pictured below). Once a nerve cell, or neuron, is damaged it cannot heal. The nervous system, made up of nervous tissue can transmit impulses 100 meters per second.