Unit 10: Blood

Composition of blood Only fluid connective tissue It has both solid and liquid components

Living components of blood Living blood cells are called formed elements 45% of blood

Non-living components of blood Nonliving fluid matrix is called plasma 55% of blood

Physical characteristics of blood Sticky opaque fluid Metallic taste due to the salts The brighter the color the more oxygen-rich pH of 7.35 to % of human body weight

Plasma The non-living aspect of blood 90% water 10% salts and proteins

Function of plasma Transport various substances around the body Helps distribute body heat evenly throughout the body

Plasma continued DO NOT WRITE: There are various constituents of plasma (things that make plasma up) The following section is the list of key constituents within plasma, and their specific role in the body

Water Solvent for carrying other substances

Salts (electrolytes) Osmotic balance pH buffering Regulation of membrane permeability

Plasma Proteins Osmotic balance pH buffering Blood clotting Defense Lipid transport

Substances transported by blood Nutrients Waste products from metabolism Respiratory gases

Formed Elements

What are formed elements? Blood cells and platelets LIVING constituents of blood

Erythrocytes Aka: Red Blood Cells ~ 4-6 million per mm 3 Function: carry oxygen to all cells in the body

Anatomy of Erythrocytes Lack a nucleus and contains very few organelles sacs of hemoglobin, an iron containing protein More hemoglobin = better oxygen transport

Shape of erythrocytes Bulky outer ring with a depressed center biconcave This depression helps carry oxygen

Leukocytes Aka: White Blood Cells ~4,000 to 11,000 per mm 3 Critical to body defenses against disease caused by bacteria, viruses, parasites, and tumors

Anatomy of Leukocytes Only blood cell to contain nuclei and organelles Because there are various types of WBC, there is no general shape

How do they function in the blood? WBC’s can jump from the blood stream to the other organs in order to carry out their function They use this method for inflammatory and immune responses

How do WBC’s know where to go? By a process is called positive chemotaxis When cells are damaged or destroyed, they release the chemicals within them The WBC’s are able to locate this chemical and seek it out

Neutrophils: 40-70% of WBC Active phagocytes # increases rapidly during acute infections

Eosinophils: 1-4% of WBC Kill parasitic worms, increase during allergy attacks

Basophils: 0-1% of WBC Contains histamine, discharged at sites of inflammation

Lymphocytes: 20-40% of WBC B-lymphocytes – produce antibodies T-lymphocytes- graft rejection, fighting tumors & viruses

Monocytes 4-8% of WBC Become macrophages Long term “clean-up team”

Platelets ~300,000 per mm 3 They are actually incomplete pieces of cells They function in blood clotting

What are platelets made out of? A complex, multinucleate cell ruptures and releases thousands of fragments of itself Once they explode, they attempt to reattach to each other Forms a net that blood may clot onto

Hematopoiesis blood cell formation Occurs in bone marrow of long bones Once finished, the new blood cells are released into the surrounding blood vessels

What causes hematopoiesis? Each blood type is produced in response to changing stimuli Effects for each blood cell type and platelets will be looked at

Before hematopoiesis: Stem cells* called hemocytoblasts are found in the bone marrow of bones These cells are activated by specific hormones which determine what type of cell it will become *A stem cell is a cell that can become any type of cell initially. Once its path is set, however, it MUST become what has been determined. For example, a hemocytoblast is activated to become a RBC, once this happens, it can never be a WBC or platelet

Hematopoiesis of Erythrocytes

Why cant RBC’s just split to make new cells? RBC’s are anucleate, so they cannot repair, grow, or divide As they age, they become rigid and fall apart Life expectancy of RBC: days

What happens to old RBC’s? Remains of old and broken RBC’s are eliminated by phagocytes in the body

How does the body replace the old RBC’s? Hematopoiesis This replaces the RBC’s continuously throughout life This occurs over a 4-step process

Step 1: stimulus Decreased RBC count Decreased availability of O 2 to blood Increased tissue demands for O 2 all these lead to decreased O 2 levels in blood

Step 2: Kidneys release the hormone erythropoietin

Step 3 Increased levels of erythropoietin stimulates the bone marrow to increase production of RBC’s

Step 4 The increased RBC count raises the amount of O 2 distributed to the blood and tissues Homeostasis is restored

Hematopoiesis of Leukocytes

How does hematopoiesis of WBC’s occur? The exact same way as for RBC’s, with only 2 changes:

WBC hematopoiesis 1. The new stimuli are chemicals released when cells are inflamed or destroyed, as well as exposure to bacteria and toxins

WBC hematopoiesis continued 2. The hormones that stimulate the bone marrow to produce WBC’s are called interleukins

What is hemostasis? stoppage of blood flow It occurs after a blood vessel is broken

Phases of Hemostasis 3 phase process that completely stops blood loss and fills the hole in the blood vessel

phase 1: Vascular Spasms Damage occurs which spreads platelets out. Once platelets spread, they become sticky and attach to the damage site The platelets then release chemicals to attract other platelets, and to induce spasms of the blood vessel Constricts the blood vessels and reduces blood loss

phase 2: Platelet Plug Formation Once the platelets have attracted enough of each other onto the damaged tissue, a plug of platelets is formed This prevents blood loss, but is very weak and easily broken

phase 3: Coagulation Threadlike proteins called fibrin then connect the edges of the ruptured blood vessel to begin the healing process. This occurs OVER the platelet plug

How long does this process take? Blood clotting usually takes only 3-6 minutes

What happens after the clot is formed? Immediately after the clot forms, the healing factors are disabled This prevents too much blood from clotting, which can lead to strokes The extra clot is then broken down

Blood Types

Why do we have different blood types? Our RBCs have different molecules attached to them Each person’s molecules are unique These molecules are called antigens

Antigens o Molecules that, when introduced into the body, triggers the immune system to kill the new antigen Our bodies naturally produce some antigens, they are found on our RBCs

Since we all have different antigens on our RBCs, our bodies can tolerate our own blood, but certain blood types are lethal to other people.

Are all foreign antigens lethal to us then? There are only 3 main RBC antigens that are lethal to us: Antigen A Antigen B Rh antigen The occurrence of these antigens in our blood determine what blood type we are

How does our body fight the antigens? Anti-A and Anti-B antibodies are located in the plasma Anti-A antibodies will destroy RBCs with A antigens Anti-B antibodies will destroy RBCs with B antigens

Blood group types 4 types based off the A and B antigens located on the RBCs

Type 1: AB This blood type has both A and B antigens Therefore, there are NO antibodies in the plasma This blood type may receive A, B, AB, and O type blood Universal reciever

Type 2: B This blood type has only B antigens Therefore, there are anti-A antibodies in the plasma This blood type may receive B and O type blood

Type 3: A This blood type has only A antigens Therefore, there are anti-B antibodies in the plasma This blood type may receive A and O type blood

Type 4: O This blood type has NO antigens Therefore, there are anti-A and anti-B antibodies in the plasma This blood type may receive only O blood type Universal donor

Rh factor Rh is a different type of antigen that is NOT produced naturally by the blood of Rh negative people The immune system produces Rh antibodies only when exposed to the Rh antigen

How do we receive the Rh antigen? The Rh antigens are passed down genetically Rh antibodies are made by our immune system when exposed to the Rh antigen This is the + or – sign you see in your blood type