Anatomy of the pituitary gland

[Music] okay so back to the head and neck this week I've been talking about what I've talked about endocrine organs in in general I was mostly doing the embryology but we've been doing a bit of endocrinology this week so we talked about the anatomy of the endocrine organs the gonads we've already looked at what we do the others anyway starting at the top have you guys heard of the hpo axis or the you know the hypothalamic pituitary ovarian axis or girdle axis or things like that what I want to talk about today is the pituitary gland [Music] it is in the head which is a key endocrine organ and a key organizer of other endocrine organs but I'm obviously not going to talk about the endocrinology because I'm an anatomist so what we'll look at is where is the pituitary gland what bones does it live in what other structures are nearby how is it linked to the hypothalamus with which it shares a an interesting relationship what's the blood supply what's the venous drainage and that's all thing all right so as with any head and neck anatomy the biggest issue I find is particularly stuff inside the head is trying to get a three-dimensional understanding of where a structure is particularly if there's a squeegee bit of brain and we're about it you know whereabouts it is within the three-dimensional space of the cranial cavity what are the things in nearby pituitary gland isn't too bad that's the pituitary gland now so classically described is about the size of a pea fair enough and it's sat within a little little curve of bones with sass surrounded by bone here but this is obviously a midsagittal section through the head and neck right down the midline so the pituitary gland is is in the midline there's only one of them many organs have a left and right versions don't they but the pituitary gland there's just a central one you see the level we're out here so here's the nose here are the eyes look so we're about here here's the nasal cavity now the bone now the pituitary gland lies within is the sphenoid bone so if we look inside the skull girl we see quite a prominent thing the sphenoid bone is here this here and if you can actually see when you look at a skull if you can see the suture of the sphenoid bone economy see it's nice butterfly straight shape right - big triangles so right in the middle here there's this obvious depression and in there that is where the pituitary gland lives in life the depression is called the sella turcica literally turkish saddle it's a type of horse riding saddle that you know kind of goes up quite high at the front which is what this bit of bone does curves around the pituitary gland do you remember that the the internal carotid artery is right next to the sella turcica on either side right so these little little holes there so the pituitary gland lives within the sella turcica it's mostly surrounded by bone it has the cavernous sinuses the dural venous sinuses knit either side of it and linking to each other in that area and then we have the internal carotid arteries either side so it's in the central location with an awesome blood supply two major arteries and a major venous thingy now the pituitary gland lying within that bony cavity is covered over by Giro mater so when we take off the bone we find the dura mater the thick connective tissue covering the brain there are three layers of meninges dura mater arachnoid mater and Pia mater right and the the dura mater is the tough cut of covering there when we're dissecting cadavers to study this and we take the brain out when we take the brain out although the pituitary gland is attached to the brain and to the hypothalamus more on than a bit and then we take the brain out the pituitary gland remains within the skull so the pituitary gland is connected to the hypothalamus I've done a whole video on the thalamus the hypothalamus is hypo below the thalamus in the midline and the hypothalamus connects to the pituitary gland with a stalk pituitary stalk or infundibulum it gets called now the reason the pituitary gland gets left behind is because it's also covered by some dura mater so it's mostly covered over by dura mater and held down into the sella turcica with just the infundibulum the stalk poking through so when we pull the brain out of the stalk hairs and the children gland gets held down so that connected tissue that dura mater covering the the pituitary gland gets called the diaphragmatic like a diaphragm seller seller to this occur yeah how many models try to show this with so there's the pituitary gland there's the sphenoid bone and here's the thalamus here and this is the hypothalamus there so this then is the pituitary store called the infundibulum linking the hypothalamus to the pituitary gland right I'm trying to do the anatomy but without talking about what the clan does what do you guys know about the pituitary gland so I said that it's an overall organizer right i mean the reason i want to talk more about hormones now is because i'm bringing in the hypothalamus but the pituitary gland makes adrenocorticotropic hormone ACTH makes growth hormone GH r HGH it makes TSH thyroid stimulating hormone it makes luteinizing hormone it makes follicle stimulating hormone and that's the anterior pituitary so the pituitary gland itself has three parts it has an anterior pituitary like an intermediate pituitary bit in the middle and a posterior lobe and the pituitary gland also has another name also gets called the hypothesis hypo below fizzy's growth suggesting that is a Down growth from the brain now in fact the posterior lobe which also gets called the neuro hypothesis or neuro hypothesis hypothesis is indeed a drain growth from the brain the man bit is still directly connected to the hypothesis the hypothalamus up here but the anterior lobe also gets called the adeno hypothesis is actually an up growth from the roof of the mouth so the anterior lobe is derive from or elected erm and the posterior lobe is derived from Nurik to them and then there's an intermediate part in between the two and then we have the infundibulum or the infundibular stalk of the pituitary stalk linking the posterior lobe to the hypothalamus now the anterior lobe of the pituitary gland is very gland it's filled with cells which are making all of those hormones I just listed and prolactin might be the full list anyway so there's there are several different types of cells in the anterior lobe of the pituitary gland each one is responsible for making you know a hormone or two and each of those hormones have downstream effects on other organs so the adrenocorticotropic hormone ACTH Adreno has an effect on the adrenal glands thyroid stimulating hormone has an effect on the thyroid glands luteinizing hormone and follicle stimulating hormone may have effects on the the ovaries and so on and so on right so those cells are very glandular but in the posterior pituitary gland if we look at those cells they look more like nerves because they are and there we find vasopressin also known as ADH or antidiuretic hormone and oxytocin being released so ADH or vasopressin has an effect on the kidney doesn't it and kidney function has an effect on regulating blood pressure results of Tosun is important in lactation and preparing for labor and labor and that sort of thing right now what's happening there is is that the the cells of the hypothalamus the neurons there they're actually making the vasopressin but they're passing it down their neurons down the infundibular stalk into the posterior lobe of the pituitary gland where it is stored and released when appropriate cool her intermediate lobe makes or the intermediate part makes melanocytes stimulating hormone stimulating the melanocytes and there's pretty rudimentary and in us humans I think it's probably more important in some other animals but those are the three parts there so they they're quite different but they all live together in this same organ do you see how it's very difficult to stay on track and talk about the anatomy when you're talking about an organ like the pituitary gland whereas it's so busy endocrine EE sorry the point I'm trying to make is that the hypothalamus and the pituitary gland are linked partly because of that vasopressin an ADH link in the post depart but also in the blood supply so the the arterial supply to this region so the pituitary gland comes from small arteries from the internal carotid artery which makes sense right because it's right next to it but there is a hypophyseal portal system and what that means is you have a capillary bed around the hypothalamus and you have a capillary bed around the pituitary gland and those two capillary beds are linked by by blood vessels so there's a portal system linking the two capillaries which means that in those physiological feedback loops that no doubt you've seen and read about hopefully with the pituitary gland I playlists and other organs this the hormones produced by the pituitary gland get passed into that the capillary bed and then passed they can pass directly because you've got to go a little way then up to the hypothalamus and have an effect on the cells with the hypothalamus so there's this little cool portal system there which you should be aware of linking the two most of the blood vessels around the brain are have tight junctions linking the endothelial cells together giving that blood-brain barrier right whereas around here those capillaries are actually leaky they're fenestrated so the hormones can leak out and affect these structures now the venous drainage is from the pituitary gland into the into the cavernous sinus which is around here and then from the cavernous sinus the Bloods going to pass to the internal jugular vein and then drop down into the systemic circuitry system so blood from the pituitary gland when hormones are released into again the circulatory system very easily which is quite nice now what I was looking for was so you've got me brain models here all these brain laws they've lost their pituitary glands as well because they didn't have pituitary glands hanging from pituitary stalks but they've all broken off and no doubt would probably got a couple of plastic pituitary glands rattling labs somewhere because he got dropped broken off not notice - not picked up but we can see on this model when you see how the pituitary gland is is very much here we see the fantabulous dog sticking up you can see that - internal carotid arteries and as this model shows the dura mater and the dural venous sinuses you get an idea of where the cavernous sinus is so we've talked about a pituitary gland where it is the bone or another bony bit right this is the sphenoid bone here and there's a pituitary gland this space here is this phenol little sinus right now we've talked about the bone where the pituitary gland is there blood supply functional now sort of thing there are a couple of interesting clinical things one tumors of the pituitary gland occur an adenoma now if I said there are several different cell types within the anterior pituitary gland and each of those cells will produce say mostly produce one hormone if a tumor forms from one of those types of cells right so you have one cell type say for example is producing growth hormone and then that cell enters uncontrolled proliferation and starts to form a tumor and gets bigger not only will it form a tumor and get bigger and compress some surrounding structures but also that ball of cells will then be probably producing more growth hormone than the pituitary gland should so you'll see effects of too much growth hormone which might be actually growth of bones in the extremities and for example you might see complaints about carpal tunnel syndrome because everything's growing the carpal tunnel is getting smaller maybe shoes not fitting feet seeming to get bigger and that sort of thing signs of tumors growth form and and likewise you could have too much of a difference under cell producing a different hormone and producing other physiological changes so watch out for those and think back to the pituitary gland now the other thing anatomic is if the pituitary gland enlarges because it's surrounded by bone it can only go up really and it's covered over as I said by dura mater but there's another structure up here as well which we can just about see what's that well if we look here we can see the two internal carotid arteries we also see these two nerves going anteriorly so these are the two optic nerves cranial nerve - going to the retinal eye on the side now what we don't see here is that these two optic nerves crossover superior to the pituitary gland that the optic chiasm and that is that is what we're seeing here we're seeing the optic chiasm in section so is it's an X it's crossing in an actor of the plane of section here so that means that as a pituitary gland if it starts to enlarge it's gonna it's gonna push on the optic chiasm it's going to push on the optic nerves which is then gonna give some changes to the vision we haven't done eyes yeah everyone who has a big one so maybe I'll talk about what those changes might be but suffice to say that if you start on the eye you go down a rabbit hole but the retina there they've taken images upside down you have let them they cross over at some some crossover some don't anyway so the effect might be not so much a loss of vision but loss of visual fields I'm going to stop there if you want to know more about how the pituitary gland may affect vision go and have a look online because honestly is it is a nice interesting complicated thing but I'm not gonna get it across now so there you go the pituitary gland so hopefully you could find that on transverse section mr or CT or you know coronal section or sagittal section it is in the midline it's surrounded by the sphenoid bone it has the two sorry internal carotid arteries on either side and the cavernous sinus and it's linked to the hyper know that if you've ever had a lecture or somebody's spoken to you about the pituitary gland the first thing they'll do is is tell you where it is but there's a bit more information to to lay on top of that hopefully that was useful since I've been talking about it this week I thought I might share it right see boys and girls next week same time same place same same anatomy lab right where did this brain come from is this one is it [Music] you [Music]

Channel: Sam Webster

Views: 138,757

Keywords: pituitary, anatomy, sphenoid, pars nervosa, pars intermedia, hypophysis, neurohypophysis, adenohypophysis, pituitary adenoma, histology, Sam Webster, dontbeasalmon, Swansea University

Id: zs1dE_sOjIg

Length: 17min 30sec (1050 seconds)

Published: Thu Mar 29 2018