so welcome to our discussion of tissues glands membranes and skin so we're moving away from review of chemistry and then also cell biology but you may be very familiar with from your undergraduate you know or your introductory bio class or even your high school biology and here we really want to get started with simple structure simple membranes which are really simple organs in glands and eventually we're going to move up to the first real organ that we're going to talk about which will be the skin I won't be providing a detailed discussion of tissues here because I know that you are doing a very intense study of tissues in the lab but you should be able to have an understanding of tissues the different tissue types and their functions as we go forward so I won't necessarily officially be reviewing that here all right so looking at the learning objectives then we're gonna start with glands in this short video we're going to be describing glands based on their structure and we're going to be identifying glands also based on their function in saladin the important section is section five point five and that's pages 160 to 166 and I also want to point out that chapter 5 and salad and a histology chapter has got a lot of excellent photomicrographs and diagrams that are very helpful and very clear and Saladin's text as he describes this is really very good so I'm gonna encourage you to use the textbook as a resource you know for lab 2 alright so the first thing is that when we talk about glands glands are derived from epithelial tissue and you probably remember the epithelial tissue is found as a covering or as a lining glands can be single cellular or they can be multicellular and glands are structures that make a product and the product is secreted into a duct and onto a surface or a product that's secreted like a hormone into the blood now what we see here this is actually a photo micrograph from lumen histology which is the site that I like a lot the lumen of this organ is right here if we weren't sure that this was the lumen these goblet cells here that are secreting they're making and secreting mucus which you can clearly see here it's stained this pretty blue color you can clearly see that this is going from the body of the goblet cell here into this lumen so we would describe a goblet cell then is essentially being a unicellular gland because it has a product that's going to a surface here additionally you can see here here's our epithelial tissue here they are describing this as being simple columnar you can see the nuclei are kind of elongated here and we often see this epithelial is as I said lining lining a hollow organ so we can clearly see that all right so let's look at another example here glands are derived from epithelium one way that we can describe glands is either being endocrine or exocrine endocrine glands have a product that they create and it's secreted into the bloodstream and so we also call and different endocrine glands duct less ductless because the product goes into the circulatory system most hormones that we will talk about will be secretions from endocrine glands or they'll be endocrine secretions all right this is a photo micrograph of the thyroid gland the thyroid hormones are actually going to be secreted in these follicles here and so this right now is called colloid and from here the thyroid hormones and will be secreted into the blood additionally in the thyroid gland we've got some cells that are kind of in between the follicle glands and they secrete a hormone called calcitonin both of these go to the bloodstream so the thyroid gland would be an endocrine gland now in contrast an exocrine gland is a gland that secretes its product into a duct or onto a surface and so we call these we call endocrine glands ducted ducted glands here this is a photo micrograph of the scalp looks like and we see we've got hair follicles here this is the dermis of the skin of the scalp and then the epidermis you can see right here so notice that the majority of the hair follicle is actually found in the dermis and the deeper tissue of the skin what I want to show you here these are sebaceous glands right here right here there's one right here and you can clearly see the sebaceous gland is ducting to the surface of this hair right here so the product of the sebaceous gland which is called sebum it's kind of an oily product it's being ducted here to the shaft of the hair where it can moisturize and lubricate and keep the hair kind of bendable and flexible and soft and shiny here so a sebaceous gland would be an example of an exocrine gland because it is a ducted gland all right now we can describe exocrine Grint glands a couple of different ways structurally if we just look at the structure of the exocrine gland we can sort of divide it into a couple of major categories based on the number of ducts that we have do we have one doctor do we have multiple ducts and on the shape of the acini I here are they round are they sort of tubular and from this we can get one two three four five six seven different ways to classify this it's not so important to me that you understand the finer points of this kind of organization but I do want you to know that as you were reading about this or as we read about more organs and more glands you may see them described using this kind of terminology so just to put that bug kind of in your ear it is actually more common to describe exocrine glands according to the mechanism of secretion that they are using and here what we're looking at is a very cartoony depiction from lumen learning at SUNY for three different mechanisms of secretion so let me orient you to this you know very cartoony drawing the lumen of our gland is going to be here and then this is the epithelial layer of our gland and this is what's making our secretory product the vast majority of glands will secrete their product by an exocytosis mechanism glands that secrete product by exocytosis are called merocrine glands and we call this merocrine secretion the next most likely way that we will see glands to create a product is what we call hole occurrence secretion and in hole occurrence secretion here what happens is that the cells epithelial cells synthesize a product and store it for secretion but at some point the cell dies and so the secretory product then the substance is being released through the duct and onto the surface or into the lumen of an organ is actually a combination of the secretory product that was made and the cell fragments from the dying and disintegrating cell hyrum whole Dacron secretion an example of a gland that secretes its product by holocrine secretion are those sebaceous glands in the skin that we just saw on the previous slide now this is important because if we should have a disruption in the rate of the product formation and the death of these cells you could be able to see that we will have a lot of cell fragments it will kind of you know clog up the lumen of this gland here and that in turn can cause inflammation when this happens in a sebaceous gland when you've got a buildup of stuff and you've got inflammation we call that a pimple the third mechanism of secretion is something called apocrine secretion and apocrine secretion is similar to holocrine secretion in that the epithelial cells create the secretory product and then cell fragments kind of blab off or pinch off from sell itself the difference between apron secretion and holocrine secretion is that the cell the epithelial cell does not actually die and disintegrate a portion of it just sort of blebs off and becomes part of the secretory product we don't have very many examples of glands that secrete their product using this mechanism saladin discusses one in mammary glands and only the secretion of lipids but I will tell you that we use this word apocrine to describe the sweat glands the seminiferous glands that are found in the armpit and the groin and on the bearded areas of the face so we call those apocrine sweat glands because we used to believe that they secreted their sweat product by this mechanism we have since discovered that this is not true that these glands the glands and the armpit the glands in the groin and the in the bearded areas of the face are actually secreting their sweat by exocytosis so technically they're merocrine glands but the name has persisted so we still describe these as being apocrine sweat glands we've talked about what they're what they do how we can classify them from here we actually want to talk about membranes very briefly so stay tuned for that