Question

MCAT Mini-Tutorial: Composition of Blood

Answer 1

\({\bf{Three~Layers:}}\) plasma, buffy coat, erythrocytes. when blood is centrifuged it will show the layers in this order from the top to the bottom of the container.

\({\bf{Plasma:}}\) the matrix of the blood. called serum if the fibrinogen is removed.
- water (relative volume of water is altered to determine total blood volume)
- ions
- urea
- ammonia
- proteins (generally synthesized in liver except for gamma globulins which are synthesized in lymph)
> albumins: transport fa's and steroids, regulate osmotic pressure
> antibodies: see immunology tutorial

\({\bf{Buffy~Coat:}}\) thin layer of leukocytes
> granular leukocytes: neutrophils, eosinophils, basophils. short-lived. enter tissues. involved in non-specific immunity.
> agranular leukocytes: monocytes, lymphocytes, megakaryocytes. long-lived. involved in specific immunity.
> mnemonic device: (g)ranular for general immunity

\({\bf{Erythrocytes:}}\) red blood cells. don't have organelles or undergo mitosis.
- main function is gas transport
- hematocrit: relative % by volume of red blood cells. ~ 30-50 percent

Answer 2

\({\bf{Platelets:}}\)
- interact with injured epithelium and stick to other platelets
- forms platelet plug --> blood clot
- coagulation also requires the protein fibrinogen to attach to platelets

\({\bf{Leukocyte~Composition:}}\) mostly neutrophils (~60%), leukocytes (~30%) with monocytes, eosinphils, and basophils making up the last ~10% ish

Answer 3

Anyway, that's the end of my tutorial, I hope it was a helpful resource. Source material is the 9th Edition ExamKracker's Biology 2 Prep book for the new MCAT