Introduction to the Hematologic System (Nursing)

00:01 Now let's take a look at the anatomy of the Hematologic System.

00:06 When we think about the hematologic system, we typically think about blood and where it's made or hematopoiesis.

00:13 And a lot of that is going to be carried out in the bone marrow.

00:17 But there are other important structures related to the hematologic system, such as the thymus, and the spleen, as well as various lymphatic vessels and lymph nodes scattered throughout the body, other sorts of lymphoid tissue associated with mucosa called MALT.

00:36 Now, hematopoiesis itself is a pretty complicated topic, but basically it starts from a multipotent cell that can go down one of various lines.

00:46 It can go down a myeloid progenitor line where it will eventually make megakaryocytes.

00:52 Mega means big and basically, we'll branch off little pieces of it into platelets to help clot.

01:00 We could also have erythrocytes or red blood cells, erythro just means red.

01:06 We could have mast cells.

01:08 We could have myeloblasts that will then go into further structures such as basophils, neutrophils, eosinophils, and monocytes, which all have various different functions throughout the body.

01:23 But then, in addition to the myeloid line, we also can have lymphoid line.

01:28 And so the lymphoid line can form something called Natural Killer or NK cells, or basic lymphocytes which themselves can form various B cells or T cells, which even they can be subclassified further.

01:43 Now, the basic cell of the blood and by far the most numerous cell of the blood are the erythrocytes or red blood cells.

01:51 Again, whenever you see erythro, it just means red.

01:54 And they're by far the most numerous because they're the ones related to oxygen transport all throughout the body.

02:02 And we looked at this in the respiratory system, where it gets the oxygenation from small air sacs in the lung called alveoli.

02:13 So red blood cells reach very, very small capillaries that surround these air sacs to become oxygenated and go back to the heart and spread out throughout the systemic circulation.

02:27 If we go back to the megakaryocytes, these are some very large cells hence the name megakaryocytes that live in the bone marrow.

02:38 And instead of going out into circulation themselves, they pinch off little bits of their selves as platelets, those go out into circulation.

02:49 And out into the bloodstream, the platelets act to serve as cloters.

02:54 So if there's any sort of damage to a blood vessel, for example, in order to prevent too much blood loss, the platelets will form a blood clot in that wall.

03:06 We also have collectively what we call white blood cells that have various different forms such as basophils or eosinophils.

03:15 Those just have to do with basically the color of the granules that exist within the cells.

03:21 But they're both pretty much involved in allergic responses.

03:25 And eosinophils can also be related to the fight for parasite damage when we have some sort of worm infection.

03:34 We also have monocytes which are very complicated in the sense that they circulate a something called a monocyte.

03:41 But when they exit circulation and reach a tissue can become a macrophage.

03:46 And macrophage means big eater.

03:49 And so they can eat up debris and you know, bacteria and other things.

03:55 They can also form some other specialized types of cells as well.

03:59 We have neutrophils which are sort of like the basic cell of the innate immune system.

04:05 They're usually the first cell to respond to any sort of damage.

04:09 And they're really good at fighting off bacteria and fungal organisms.

04:13 And then lymphocytes, which are a little more slower reacting the neutrophils, but more longer lasting.

04:20 And they're really good at fighting viruses.

04:22 And certain types are the ones that actually make antibodies.

04:27 So in a typical blood smear, you'll see mostly red blood cells.

04:33 And those are the ones that are gonna be most numerous here.

04:36 And they look like little round red dots, because they don't have any nucleus in them.

04:41 And that distinguishes them from the white blood cells, such as lymphocytes, which have a really big dark nuclear center.

04:49 Then there's the neutrophils which have this kind of wavy kind of squiggly nucleus.

04:55 And the little tiny things that you might almost miss, are not just little bits of schmutz on the slide, they're actually the platelets.

05:02 And they're very, very small because they're not entire cells like these other ones are, they're just little bits of a megakaryocyte that broke off to enter the circulation.