Anatomy and Physiology. This video covers the regulation of blood calcium especially when blood calcium decreases. Including Parathyroid Hormone PTH signaling and its target organs like bones, kidneys and intestines.
Welcome this video is gonna cover calcium homeostasis so calcium levels in the body especially in the blood and in the extracellular spaces around ourselves is critically important so it needs to be maintained for our body to function somewhere between eight and ten milligrams per deciliter is considered normal blood calcium so if the calcium levels in your blood
Ever dropped to a critically low level the body’s gonna need to respond now you might think of calcium as needed for your bones but actually calcium is critically important for a function of the brain and the heart little cardiac myocytes and neurons need calcium in order to have action potentials to contract and in order to release neurotransmitter even your
Skeletal myocytes and your muscles need calcium in order to function so whenever calcium gets too low how does the body regulate it and increase it back towards normal it’s actually the cells of the parathyroid glands located in the neck that are responsible for calcium regulation they’re actually found embedded in four little clumps on the thyroid gland and these
Parathyroid gland cells have a special little calcium sensitive receptor which can sense the levels of calcium in the extracellular fluid as blood calcium levels get low these cells release more pth through exocytosis the parathyroid hormone then travels throughout the body targeting various tissues one of the primary targets of pth will be the bones so the little
Cells in bone are either building bone or chewing up the bone you might remember osteoclasts and osteoblasts osteoblasts will build bone and osteoclasts chew up the bone in the case of pth signaling the osteoblasts will become less active the osteo class will become more active this will release stored up calcium from the bone into the bloodstream which will help
Increase blood calcium again pth changes the activity of these bone chewing and bone building cells so that more calcium is released from the bone matrix into the bloodstream helping raise blood calcium levels another important target of pth will be the kidneys the kidneys are responsible for filtering things in blood and then it can remove those from the body in
Urine so since calcium is in your blood and calcium is very small it easily filters into the kidneys the kidney cells then must reabsorb the calcium and keep the calcium in the body pth is critically important to tell those cells to keep the calcium that is filtered so as pth levels go up the little kidney cells know to keep more calcium in essence reabsorbing it
Adding it back to the blood stream and helping raise and keep our blood calcium levels high enough so whenever pth levels are high the kidneys are reabsorbing more calcium and less calcium ever makes it into the urine and so the urine would have low calcium levels another important target for pth is going to be the intestines since we get a little bit of calcium
Usually from our digested food the intestines become an important source for blood calcium so as food is digested inside the intestines the calcium is released then the calcium has to be absorbed by the little intestinal cells otherwise it ends up going out of the body in the feces so pth signals to those little intestinal cells to get the calcium from the digested
Food and absorb it into the body this then adds the calcium to the bloodstream and helps raise calcium levels in the body an important thing to know about pth signaling and the intestines is it requires the help of vitamin d you might think of vitamin d is something that comes from sunlight and your skin and you’d be right but vitamin d actually is activated in
The kidneys too a hormone called calcitriol and as pth levels go up the kidneys make more calcitriol from vitamin d and this means that as pth goes up calcitriol goes up and it’s actually kalsa trial acting on the intestines to tell the intestinal cells to get that calcium so just remember vitamin d and pth are important for the intestines so remember whenever
Calcium levels get low the parathyroid glands are going to broadcast pth signal which will help our bones know to release calcium our kidneys to reabsorb calcium and our intestines to absorb calcium from our diet this helps bring our blood calcium levels back up to normal maintaining homeostasis
Transcribed from video
Calcium Homeostasis and Parathyroid Hormone – PTH By Physiology \u0026 Anatomy Videos
