Answer:
B
Explanation:
I'm pretty sure it's B, because I've had this same exact question yesterday. If it's not right, please don't be mad at me!
Natural emergency: something that occurs naturally
manmade: something caused by a person (ex.shooting)
Answer: Yes the ozone layer sits at the top to protect us from harmful UV rays from the sun.
Explanation:
According to World Health Organisation, approximately 500,000 preschool age children go blind each year due to vitamin A deficiency. Vitamin A is need for proper functioning of the immune system and for the proper functioning of the eyes. Sources of vitamin A include: egg, liver, vegetable with high carotene contents, fortified milk, fruits, etc.
<h3><u>Answers;</u></h3>
-less than 1%
-Thrombopoiesis
-Megakaryoblast
-Thrombopoietin
-Megakaryocyte
-Proplatelets
-Platelets (thrombocytes)
<h3><u>Explanation</u>;</h3>
- Platelets (or thrombocytes) make up less than 1% of formed elements with a concentration between 150,000 and 400,000 per cubic millimeter. The production of platelets is called thrombopoiesis.
- From the myeloid stem cell, a committed cell called a megakaryoblast is produced. It matures under the influence of thrombopoietin to form a megakaryocyte.
- Megakaryocytes are easily distinguished both by their large size (about 100 micrometers [μm] in diameter) and their dense, multilobed nucleus. Each megakaryocyte then produces thousands of platelets.
- The process of how megakaryoctes produce thrombocytes was in question until 2007. Researchers reported that megakaryoctes produce long extension from themselves called proplatelets.
- While still attached to the megakaryoctye, these proplatelets extreough the blood vessel wall in the red bone marrow. The force from the blood flow "slices" these proplatelets into the fragments we know as platelets (thrombocytes).
