Introduction to endocrine system anatomy

just come from a first-year Anatomy revision session because they've got exams coming up next week I know I know it doesn't sound like a good time of year but it is it's a good time of year it's so good to see them they're all talking they're discussing things with each other they're teaching each other they're answering questions they know stuff and they've worked really hard to get there really really nice to see as a teacher I'll be really nice to mark your exam papers as well in a couple of weeks time anyway we are here to talk about the anatomy of the endocrine system it's another one of those systems um that's absolutely vital for life it's really really important you know because it's involved in controlling basic functions of the body but anatomically what are your points to [Music] so if we're going to talk about the anatomy of the endocrine system and I think I'm going to start at the top on my missing out here pineal gland hypothalamus pituitary thyroid parathyroid pancreas gastrointestinal tract as a whole adrenal glands kidneys gonads that's a lot so I'm gonna have to be brief and this is an anatomical look at things not a physiological look at things but I'll mention the hormones and where they are as we go right and then I probably got other videos in more detail about each organ if you want to know more right so what are we talking about with the endocrine system the endocrine system is a method of signaling from one group of cells to another group of cells across the body the signals are hormones the hormones travel in the blood and this is you know relatively speaking a slow thing why don't you just use nerves I hear you say nerves are a really quick way of controlling things well hormones were a different way of regulating other cells the cells that respond to the hormone have gotta have a receptor for that hormone and this is kind of like a slower longer lasting signaling thing communication thing then maybe what nerves do and anyway it's Evolution so it's messy what are you going to do these endocrine organs seem to have a risen you know individually separately producing various hormones that do various jobs and we find that there are some endocrine organs up here that control other endocrine organs so you might hear of axes like the HP something axis like the hpo axis the hypothalamus pituitary ovarian axis and things like that well let me clear up the anatomy for you so you know what those words mean all right let's get some organs I just thought we'd start at the top because that keeps us organized but also if we start at the top we get some of those controller endocrine organs hey to come brain and within the brain we see a couple of things well kind of so back here we find an organ we could find the pineal gland pineal it's like pine cone shaped so the pineal gland is within the brain the pineal gland is involved in recognizing the change in the length of day certainly in the furry mammals so and in a lot of vertebrates generally um and it adapts the weak sleep cycle and probably other things to the changing seasons of the year it also is involved in the circadian rhythms of our wake sleep cycle it makes melatonin this is why this is the organ that you're tweaking when you take melatonin when you fly across time zones to try to trick your body into sleeping when you want it to sleep so the pineal glands up here it's kind of interesting for that but the lump next to it is the thalamus and this part of the brain down here is called the hypothalamus because it's below the thalamus now the hypothalamus is a really interesting part of the endocrine system this part of the brain controls other endocrine organs often via the pituitary gland which is nearby we'll have a look at in a moment um the the neurons in here the cells in here make these are pressing which is also known as anti-diuretic hormone or ADH and they make oxytocin but we'll see that those are actually released in the pituitary gland but they also make a lot of um hormones that control other hormones so we've got like growth hormone releasing hormone and growth hormone inhibiting hormone we've got corticotropine releasing hormone thyrotropin releasing hormone gonadotropine releasing hormone and we'll see what those mean as we go down right so this region of the brain is regulating appetite it's regulating body temperature is regulating like sleep cycles it's involved in memory the hypothalamus is a part of the brain and it is an endocrine organ an endocrine structure there now because I've taken this out of the cranial cavity the pituitary gland would be hanging down from here but it's gone it's still the cranial cavity so let me get a different model to show you the pituitary gland half head so mid-sagittal section there's the hypothalamus there that I was talking about this here is the pituitary gland there's the sphenoid sinus there's the pituitary gland there sat in the bone there and the pituitary gland is directly connected to the hypothalamus there's a little stalk it's directly connected by blood vessels and it's directly connected by the axons of neurons so as I said the hypothalamus releases oxytocin and vasopressin into the pituitary gland now the pituitary gland has got this lovely um little capillary Network and I said that hormones are passed into the blood pass around the body in the blood and then act on other cells at a distance so the hormones are released into the blood off they go hit their other targets so these are very much controller or regulator organs red endocrine organs of other tissues around the body so these are pressing will act on the kidneys to regulate uh water loss and blood pressure and you know that sort of thing oxytocin is involved in childbirth lactation social bonding think it gets called the cuddle hormone it's oxytocin is coming from that hypothalamus pituitary link now the anterior cells of the pituitary gland also make hormones they will make growth hormone guess what that does they will make adrenocorticotropine hormone which will act on the cortex of the adrenal glands we'll come back to that later they release follicle stimulating hormone that's acting on the follicles in the ovary it releases luteinizing hormone which will act on the female reproductive system it'll act on the male and the female gonads it releases thyroid stimulating hormone guess what that stimulates uh and it'll release prolactin which is going to initiate milk production by the mammary glands right so I've listed a number of hormones there that are going to act on other endocrine organs anatomically look where it is nasal cavity oral cavity if there's a lot of brain up here if somebody had a tumor here how might you choose to access that surgically would you go that away or would you go that away so hypothalamus pituitary and within the pineal let's work our way down to the thyroid gland the thyroid gland is here so here's the the laryngeal prominence and we're going down a little way and then we're at the trachea down here the thyroid gland is wrapping around the trachea on the left and right sides there's the central Isthmus here the thyroid gland is involved in regulating metabolic rate regulating protein synthesis in cells throughout the body which means it also has effects on growth and temperature and energy use and things like that it also those hormones are thyroxine and tri-iodothyronine T4 and T3 it also produces calcitonin another hormone that decreases blood calcium the amount of calcium in the blood this is interesting because if I was able to peel back the thyroid gland I'd find four little brown kind of p-shaped organs posterior to the thyroid gland called the parathyroid glands the parathyroid glands make parathyroid hormone which increases blood calcium so those two work together to keep just the right amount of calcium in our blood you need to have the right amounts of you know glucose and minerals and salts in your blood so the cells throughout your body work as they're supposed to work all these things work together they're all crucial so thyroid and parathyroid okay I'm gonna have to take some organs out here's the liver take that out take this stomach out and there we can see the pancreas if I take that the great momentum off just so you can see there's the small bowel there's the transverse colon but this here there's the spleen this is the the pancreas if I take off the transverse column we can see it a little bit better the pancreas is an exocrine and endocrine organ so it's an exocrine secretion means you're secreting onto an external surface and the gut tube is an external surface inside us it has external things going through it right so the exocrine secretions are helping with digestion now the there are patches of cells in the pancreas called the islets of langerhans kind of one of those things you you learn early on and sticks with you anyway eyelets have laying hands and those groups of cells are producing hormones those are Endocrine cells so the endocrine secretions of the pancreas are quite well known insulin and glucagon regulate blood glucose levels by affecting the other cells in the body like glucose uptake by those cells and release from stores and that sort of thing somatostatin is also made by cells here so somatostatin will kind of switch off the pancreas it'll dial down those endocrine and exocrine secretions somatostatin is quite interesting because it's actually produced by other endocrine organs in the body as well including the hypothalamus and then it also makes pancreatic polypeptide which again has a role in regulating the pancreas itself so insulin and glucagon are the most interesting hormones here so the pancreas is important as you know you probably knew right now the rest of the gastrointestinal tract but it's also regulated by hormones that was the point I was trying to make um uh there's an what we call an enteric nervous system so the gastrointestinal tract kind of has its own little mini brain regulates itself nervously and it also has its own little endocrine system which sometimes gets called the enteric endocrine system so it is also regulating the activity of cells in the gastrointestinal tract using hormones you might have heard of some of those hormones like ghrelin and cholecystokinin and gastrin and things like that so again the gastric the cells within the gastrointestinal tract also have some endocrine function some signaling to one another using hormones which is really important in things like appetite regulation right you're switching on and off the GI tract uh hmm ah right you can just see the next candidates peeking out from behind if I take off the gastrointestinal tract and we look at the posterior abdominal wall we've got these little little organs here which are absolutely crucial to life these organs sit upon the kidneys stuff associated with the kidneys gets called renal so these organs are known as the suprarenal glands because they are superior to the kidneys or the adrenal glands because they sit on top of the kidneys they have a medulla in the middle and they have a cortex around the outside which do quite different jobs the cells in the medulla make adrenaline and noradrenaline that is the site of your fight or flight response that is where that adrenaline dump comes from that adrenaline and noradrenaline can be released into the blood swells around the body switches on loads of things gets you ready to survive some difficult or dangerous encounter um whereas the cells in the cortex around the outside make steroid hormones cortisol the stress hormone um aldosterone they're involved in synthesis of estrogens and testosterone in both men and women right so these little organs are producing hormones that make glucose available from stores to make sure your cells of your body have got energy they they're involved in making sure the the salt concentrations in the blood are as they should be they're regulated because all the cells in the body need a certain salt concentration right they're involved in regulating blood pressure all these little tasks that are crucial for all of the cells in your body to function and these cells are involved with that so do you remember that the hypothalamus was going to trigger the pituitary to release adrenocorticotropin hormone which sounds like a very long word but adreno cortex tropin so switching on production of hormones from the adrenal cortex to switch on other things so the hypothalamus is regulating the pituitary is regulating the adrenal glands is regulating other things we have various positive and negative feedback loops so that's the sort of thing we see with the adrenal with the um endocrine systems now the kidneys as well they make hormones so they they get involved they make erythropoietin a little bit of a dirty wood in professional cycling EPO erythropoietin signals the cells in the bone marrow to make more red blood cells when your blood needs to carry more oxygen they make a calcitriol which is like the end of the vitamin D synthesis pathway which then triggers your gut to absorb more calcium these are very long Pathways sometimes um and they make renin so there's the renin aldosterone Angiotensin so again renin is made by the um the kidneys and it's involved in regulating blood pressure there are hormones that affect cells that make other signals that affect cells that make other signals gets very complicated but it's working all the time and when it stops working there's a problem all right so we're down to the level of the kidneys if we get down any further we get down to the gonads which this person doesn't have okay different model then here we go this one's a bit easier to remember uh the testes are endocrine organs they make testosterone which is important in developing male secondary sexual characteristics and continuing male secondary sexual characteristics and functions through life so testosterone the testes also make estrogen did you know that and there are different forms of estrogen so men have estrogen and women also have testosterone just different levels right and there are other hormones made in here inhibins and active ins and the hormones that tend to be involved in locally managing spermatogenesis the production of new spermatozoa what about the ovaries okay uh uh there's the ovary in there and you see where we are there so um pelvis kind of lateral wall there the ovary the cells in the ovary make estrogens and progesterone which are important in developing female secondary sexual characteristics and volatility and maintenance of fat fertility in the menstrual cycle maintaining the endometrium in case a fertilized blastocyst is there and can implant and fertility really a really important fertility stuff so very very important endocrine organs down here and you remember how I said that the pituitary gland releases luteinizing hormone and follicle stimulating hormone well those are having effects on the cells in the ovary to trigger ovulation and are involved in regulating the menstrual cycle so the hypothalamic pituitary ovarian axis that's the control sequence what do you reckon how was that so that's the endocrine system the organs of the endocrine system they are spread about the body from top to bottom we saw the pineal gland hypothalamus pituitary we talked about how those organize the actions of the other organs we saw the thyroid parathyroid pancreas talks about the gastrointestinal tract adrenal glands kidneys gonads there are cells spread around the body and they can signal to one another using hormones that they pass into the blood which will then bind to other cells if they have a receptor for that hormone and Trigger response in some way that's the endocrine system so like the immune system it's kind of difficult to point at the anatomy of the endocrine system but hopefully you've got an idea now when you're learning about the endocrine system the physiology you've got physical structures to Anchor those ideas and that knowledge too and of course there's more Anatomy if you want more um there is more to a search you'll find it see you next week [Music] thank you

Channel: Sam Webster

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Id: PEs0Xf3DvRk

Length: 19min 41sec (1181 seconds)

Published: Thu Mar 16 2023