In this video, we're going to briefly compare the functions of epithelial and connective tissues. We already know from our previous lesson videos that epithelial and connective tissues are both pretty diverse in terms of their functions. Because of this, some of their functions may seem to overlap a little bit. Therefore, we're going to compare their functions to clear up any potential confusion. Notice down below we have a three-column table with blanks, and we're going to fill out the blanks as we go through the video.
The middle column lists the functions of the tissues. Please remember that this is not an exhaustive list of all the different functions of these tissues; these are really just broader groupings of the functions of these tissues. In the column on the far left, we have examples of epithelial tissue functions, and in the column on the far right, we have examples of connective tissue functions.
The very first function listed here is protection. Recall from our previous lesson videos that epithelial tissue functions in protection. A classic example is the outermost layers of our skin, which protect us from the outside world, including physical trauma and chemicals.
Recall that the outermost layers of our skin are made of keratinized stratified squamous epithelia, which consists of multiple layers of cells where the cells on the apical surface are flat or squished in shape. The keratinized part of that means it's going to have the protein keratin, making the tissue tougher and aiding in protection. Connective tissue also functions in protection, as the rock-hard bones, such as the skull, help protect the delicate softer tissues underneath, like the brain.
In terms of transport, epithelial tissue can regulate transport. We're talking about epithelial tissue serving as the boundary adjacent to open space and can regulate the transport of molecules across the tissue for absorption, excretion, or filtration. A classic example of where regulating transport can occur is in the digestive lining, which contains simple columnar epithelia, or one layer of tall and narrow, column-shaped cells.
Connective tissue also functions in transport. Blood, for example, is an example of connective tissue, and we know that blood can physically transport things such as oxygen gas, nutrients like glucose, and waste products like carbon dioxide gas. The transport function here is different, with epithelial tissue more so regulating the transport of substances across the tissue, not physically transporting things.
In terms of sensations, epithelial tissue can work closely with nervous tissue to allow for sensation. Epithelial tissue connects us to the outside world since it covers and lines things such as our skin. Sensations such as touch can be detected by the epithelial tissue, which then activates the nervous tissue, and the nervous tissue transmits an electrical signal for processing, allowing for the full sensation. Connective tissue, although it can be innervated and contain nerves and nerve endings, is not usually associated with sensation functions due to its diverse functions and lack of connection to the outside world like epithelial tissue.
In terms of secretions, glandular epithelial tissue forms glands and these glands specialize in secreting products such as sweat, mucus, enzymes, and more. Connective tissue cells can secrete components of their own extracellular matrix, but do not specialize or form specialized secretions like glands do.
Support, insulation, and storage are not functions of epithelial tissues but are notable functions of connective tissue. The underlying connective tissue can be vascular, having blood vessels that provide nutrients and support the epithelial tissue. Connective tissue includes adipocytes (fat cells) which store fat that helps to insulate the body. Moreover, bones can store components like calcium, and adipocytes provide long-term energy storage.
This concludes our brief comparison of the functions of epithelial and connective tissue. Hopefully, this was helpful for you to understand the differences and similarities in their functions. That concludes this video, and I'll see you all in our next video.