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Current time:0:00Total duration:7:20

Epithelial and connective tissue

Video transcript

there are four different types of animal tissue that are all made up of eukaryotic cells epithelial tissue connective tissue muscle tissue in nervous tissue in this video we're going to talk about epithelial tissue and connective tissue so when you think about epithelial tissue you can think about it as a lining both an inner lining and an outer lining so for example epithelial tissue makes up the outer layer of our skin it makes up the outer layer of organs it lines oregon's so the lumen of organs will be lined with epithelial tissue and it also lines the inside of cavities inside of the cavities of the organism epithelial tissue also makeup glands so that would include both exocrine glands and endocrine glands and just to remind you exocrine glands will release their substances directly to the target organ whereas endocrine glands usually release hormones but into the bloodstream not to the target organ directly and epithelial tissue comes in two forms it can be simple and that means it's one layer thick or it can be stratified which means they can have two or more layers and where would you expect to find simple epithelium versus stratified epithelium well you'll find simple epithelium in places where substances need to diffuse from two different places so for example the alveoli of the lungs are lined with simple epithelium because carbon dioxide and oxygen need to diffuse from the alveoli into the bloodstream and vice versa and of course that would be pretty difficult if you had a thick layer of cells and you'd expect to find stratified epithelium in places that need to resist chemical or mechanical stress so for example the esophagus is lined with stratified epithelium that's because the esophagus will have food coming through it the food might be sharp it might be hot and we want a thick layer of cells to protect the underlying tissue of the esophagus so a stratified Lehrer epithelium acts as that protective layer let's take a look at a section of simple epithelium and epithelial cells are attached to something known as the basement membrane the basement membrane is not made up of cells but rather it's made up of different types of fibers for example one fiber that can be found in the basement membrane is collagen and the basement membrane is semi permeable to certain substances and that's pretty important because epithelial tissue is a vascular that means that epithelial cells have no blood vessels which then makes us ask the question of how do they get nutrients so they get nutrients from the underlying tissue so what happens is that nutrients will diffuse from the underlying tissue through the basement membrane to the epithelial cells and that's how apathy lleol cells get their nutrients let's just recap some of the places that you'd expect to find epithelial cells so we already mention the outer layer of the skin the tissue lining the mouth esophagus and GI tract and of course this is not an exhaustive list in the tissue lining the kidney tubules and the tissue lining blood and lymphatic vessels and in fact the tissue that lines blood vessels and lymphatic vessels has a special name it's known as endothelium let's talk about connective tissue so connective tissue supports tissues connects tissues and separates different types of tissues from each other and then there are different types of connective tissue that don't necessarily fall into these neat categories so what are some examples of connective tissue bones cartilage blood lymph host tissue which is that the membranes covering the brain and a spinal cord and other types of tissues so what does connective tissue look like what are some characteristics of connective tissue so basically it has three components it has cells it has what's known as a ground substance and then it has fibers and the ground substance and the fibers together make up a matrix so let's see what this looks like here we have the ground substance which is usually a viscous type of fluid then interspersed in the ground substance are fibers and then we have cells and these cells are usually what's producing the matrix let's look at some connective tissue in more detail so the first we'll talk about is areolar tissue which is this tissue right over here so areolar tissue is a very common type of connective tissue it binds together different types of tissue and it provides flexibility and cushioning and we can actually see the structure pretty clearly in this picture you can see the cells over there those little dots there's another cell over here you can see the five resorting through it over here and over here and then the ground substance is the kind of background yellow viscous liquid that you're seeing then we have adipose tissue adipose tissue is basically fat tissues of fat it provides cushioning for the body it's stored energy and it actually is an exception to the rule it does not have fibres like most other connective tissue then we have what's called fibrous connective tissue fibers connective tissue is pretty strong it provides support and shock absorption for bones and organs and you find it in the dermis which is the middle layer of the skin tendons and ligaments here are some more types of connective tissue we have blood so blood is also an exception like adipose tissue in that it does not contain fibers and the matrix of blood is the plasma you can see the matrix this yellowish liquid in which the blood cells are suspended then we have osseous tissue or bone tissue these cells in the osseous tissue are known as osteocytes those are those brown cells that are kind of forming a pattern and the matrix in osseous tissue is what's known as bone mineral oil or hydroxyapatite which is basically collagen fibres with different minerals like phosphates magnesium calcium etc and then we have hyaline cartilage the cells in highland cartilage are chondrocytes you can see them over here they're a bunch of these cells and they're found in surfaces of joints so these are all examples of different types of connective tissue in many of them provide some form or another of support for tissues and organs