Blood

What do erythrocytes have biconcave shape?

*Erythrocytes* have biconcave shape (concave on both sides). While they have a plasma membrane, they don't have a nucleus and don't have most of the parts that other cells do. Biconcave shape gives them a large surface area that is ideal for gas exchange. It also makes them flexible, able to change shape as they squeeze through tiny capillaries with diameters smaller than the cell itself. These cells live an average for only 120 days.

Types of transfusible products that can be derived from blood

1. red cells 2. platelets 3. plasma 4. cryoprecipitate (protein needed for blood clotting)

Universal recipients and universal donors

AB - universal recipients, because they have both antigens, and therefore no antibodies for either. They can accept A, or B, or AB, or O blood. O-type doesn't have A or B antigens, so those people have antibodies for both. They can only accept other O blood. Lack of antigens means that type O blood can mix with other types of blood without getting attacked which is why it is known as the universal donor.

Antigens in blood and antibodies

All the cells in your body have a plasma membrane with specialized *glycoprotein* markers on them. These markers are your *antigens*. If your body detects antigens from someone else's cells, it will send out antibodies to bind, to those markers, often to tag them for destruction by the immune system. Your red blood cells have specialized antigens on them, called *agglutinogens* that activate antibodies that work by binding, invading cells to each other, which causes *coagulation*, or the clumping of blood.

What happens when you accidentaly cut yourself?

At the very first sign of a rupture, the blood vessel actually constricts itself to slow the flow of blood through it. Then little fragments called platelets gather at the size of the injury, creating a plug that keeps the blood from leaking further. But it is not as strong and and needs reinforcement to complete the clotting process. It comes in a form of fibril threads, protein strands that join together to make a sort of mesh that traps the platelets and blood cells. Eventually, the threads pull the opposite sides of the wound together to close the vessel wall so the endothelial cells can be replaced. Over a few days, the blood vessel heals, and the clot dissolves.

How many types of blood are there and whow much does it weight?

Blood comes in 8 different types and it accounts for about 8% of your body's weight. Blood is a type of connective tissue.

Why is blood so unique

Blood is the one component of your body that scientists haven't figured out how to reproduce, synthesize, or imitate. It is irreplaceable.

The function of erythrocytes

Blood's power rests largely in your *erythrocytes* (red blood cells). They are the most abundant cell type in your blood, accounting for nearly 45% of its volume. Every time you take a breath, they pick up oxygen in your lungs and distribute it through your body, and then grab carbon dioxide, and bring it back to the lungs, where it can be exhaled. The main mission of erythrocytes is to keep the body fed with oxygen, so your muscles can do their thing, and your brain can continue to think and feel and boss around your various parts. Because of crushing demands of their job, they don't live long.

How is the process of maintaining the right levels of red blood cells regulated?

It is regulated by a special hormone called *erythropoietin*, or EPO. It is produced mostly in the kidneys, but also in the liver, and is constantly circulating in the blood. If your level of oxygen in the blood drops, certain cell in your kidneys will take notice and take action.

Does everyone have red blood?

Not all animals have red blood because no every one of them use hemoglobin to move oxygen. For example, most mollusks like squids and snails have blue blood, because it contains *hemocyanin*, a copper-rich protein-pigment that turns blue when exposed to oxygen.

Red blood cells and hemoglobin

Red blood cells are 97% *hemoglobin*, a molecule that easily binds to, and releases oxygen. Every hemoglobin molucule is made of 8 different component molecules - 4 are a red pigment called *heme*, and 4 are a protein called *globin*. Each globin has its own heme molecule, and in the center of that heme is an *iron atom*, which makes our blood red.

Electrolytes

They are positively-charged cations like calcium, sodium and potassium, and negatively-charged anions like phosphate, sulfate, and biocarbonate. Together these ions help regulate your blood's chemistry, maintaining its pH levels and proper osmotic pressure, and allowing other tissues to do their jobs (making muscles contract and sending action potentials).

Blood's functions

To transport and distribute oxygen, nutrients, waste products and hormones around the body. It also helps regulate and maintain body temperature, pH levels, and the volume of fluids in your body. Plus it protects you from infection and from the loss of blood itself.

What happens to old erythrocytes?

When *erythrocytes* get old, they turn rigid, and their hemoglobins start to fall apart. As they get stiffer, they can end up getting stuck in capillaries in your brain or heart. These old cells get trapped and ambushed by big *macrophage white blood cells* in the spleen, liver, and bone marrow, which break them down and recycle their various components. The *globin* proteins are broken down into their basic components - amino-acids - which go back into the blood to be used by other cells for making more proteins. *Iron* from the heme group is separated and either bounds to proteins and stored in the liver, or put right back into a new hemoglobin molecule. The *heme* gets turned into *bilirubin*, a yellowish pigment that goes to the liver where it is added to the bile that is secreted into the intestine and eventually leaves the body in your poop.

Centrifuge and blood layers

When blood is put into the *centrifuge*, which spins it around fast enough to send the heavier components to the bottom of the tube, and bring the less dense elements to the top, 3 blood layers emerge. Down at the bottom you've got a heavy red layer of *erythrocytes* (red blood cells) that carry oxygen and carbon dioxide. They make up about 45% of your total blood volume. A thin white layer in the middle - *leukocytes* (white blood cells). They defend your body from toxins and foreign microbes. They are also the cell fragments called *platelets*, which help with blood clotting and make up less than 1% of your blood. At the top you see the yellowish *plasma*, which accounts for about 55% of your blood volume. Plasma is actually 90% water, but the other 10% is full of 100 different solutes, including proteins, electrolytes, gases, hormones, and waste products.

Proteins in the blood and what makes them

When measured by weight, the bulk of the solutes in your blood are the *plasma proteins*. 60% of these proteins is *albumin*, 36% are *globulins* and 4% is *fibrinogen*. Most of these proteins (like albumin, and alpha and beta globulins) are made by the liver and do things like balance the osmotic pressure between the blood and surrounding tissues, and transport lipids and ions. Others run defense for you (like the gamma globulin antibodies that are released by plasma cells during an immune response, or fibrinogen proteins which are vital to forming blood clots and stoppinf bleeding).

Blood classification

Which agglutinogens you have on your erythrocytes defines your blood type. But they are classified in 2 different ways. In the most important blood classification there are only 2 kind of agglutinogens, simply A and B. And your blood can either have one, or both, or neither. So the name of your blood type refers to what kind you have and don't have.

Rhesus antigens

You either have the Rh antigens, in which case you are Rh+ or you don't - Rh-. Most of the polulation is Rh+, so they don't have anti-Rh antibodies, and can accept either positive or negative blood, Rh- must stick to only Rh- blood.

Hemophilia

a group of hereditary bleeding disorders in which a blood-clotting factor is missing.

Whole blood

a mixture of cells and cell fragments called formed elements, along with water, and lots of dissolved molecules. A patient who needs a transfusion may only need some of those things and not others, so the parts are separated.

Hypoxia-inducible factor (HIF)

a molecule that monitors your blood's levels of oxygen.

Hypoxia

oxygen deprivation.

Hemostasis

process that your body uses to prevent you from losing too much blood.

Hematopoiesis

the process of forming blood cells (hemato - blood, poiesis - to make), happens in your red bone marrow.