12.1 Introduction

Blood transports substances and maintains homeostasis in the body

Hematophobia = fear of blood

12.2 Blood and Blood Cells

What's in Blood? - blood is a type of connective tissue, composed of scattered cells within a noncellular matrix (fluid). Composed of 2 basic components

1. Cells (rbc, wbc, platelets) - 45%
2. Plasma (water, amino acids, proteins, carbohydrates, lipids, vitamins, hormones, electrolytes, cellular waste) - 55%

Hematocrit - volume of blood in a sample, should be 45%. The remaining fluid is plasma (55%). To determine the percentages, blood is placed in a centriguge

Types of Blood Cells

red blood cells (erythrocytes)
white blood cells (leukocytes)
platelets (thrombocytes)

RED BLOOD CELLS (erythrocytes)

- Shape is biconcave discs
- 5 million per cubic millimter (RBCC = red blood cell count, amount of blood cells in a cubic millimeter)
- lacking nuclei, they will not divide. Blood cells are formed in the bone marro = Hematopoeisis.
- blood cells live for about 120 days, then are phagocytized by the liver and spleen

Main Functions

- transports O2 throughout body, and picks up CO2
- Hemoglobin = molecule which combines with O2 to transport it

Oxyhemoglobin - plenty of oxygen, bright red
Deoxyhemoglobin - not carrying much O2, "bluish red"

Iron is a critical element needed to synthesize hemoglobin and normal RBC. Anemia = too few RBC

A hormone secreted by the kidneys called Erythropoietin stimulates the formation of RBC. Process requires Vitamin B12 and Folic Acid

WHITE BLOOD CELLS (Leukocytes)

General function - defend the body against disease-causing agents (microorganisms)

Granulocytes (granular cytoplasm)	1. Neutrophils	very active in phagocyting bacteria and are present in large amount in the pus of wounds, most common, 60% WBC
	2. Eosinophils	attack parasites, control allergic reaction; 2% WBC
	3. Basophils	produces Heparin (prevents blood clots) and Histamines (causes inflammatory reaction); less then 1% WBC Inflammatory Reaction = blood vessels dilate, fluid accumulation and swelling, attraction of WBCs. At the site of an infection, dead and damage leukocytes, bacteria and body cells accumulate = pus
Agranulocytes (lacking granular cytoplasm)	4. Monocytes	precursors of macrophages, phagocytes; 6%
	5. Lymphocytes	main constituents of the immune system which is a defense against the attack of pathogenic micro-organisms such as viruses, bacteria, fungi and protista. Lymphocytes yield antibodies and arrange them on their membrane; 30%

PLATELETS (thrombocytes)

- help initiate formation of blood clots, close breaks in damaged blood vessels

12.3 Blood Plasma

- the liquid portion of the blood, 92% water
- transport nutrients, gases, vitamins, maintain fluid and electrolyte balance, and pH

Plasma Proteins

1. Albumins - made in liver, maintain osmotic pressure and blood volume (blood pressure)

2. Globulins - 3 groups: alpha, beta, gamma

a. alpha & beta globulins - from liver, transport lippids and fat-soluble vitamins
b. gamma globulins - from lymphatic tussies, antibodies for immunity

3. Fibrinogen - from liver, largest molecules of plasma proteins - important for blood clotting. Major event in blood clotting is the changie of fibrogen into fibrin

12.4 Hemostasis

- the process of stopping bleeding. 3 Key Events
- Coagulation causes the formation of a blood clot.

1. Blood vessel spasm - damaged or broken vessels stimule muscle tissue in the walls of the blood vessels to contract. This slows or stops blood flow, lasts for several minutes. Also, platelets release serotonin, a vasoconstrictor which maintains the muscle spasm even longer.

2. Platelet plug formation - platelets stick to surfaces of damaged blood vessels and to each other to form a "plug"

3. Blood coagulation - most effective, forms a blood clot (hematoma). Injury causes an increase in the release of coagulants. Main event - conversion of fibrinogen into long protein threads called fibrin.

Tissue damage = prodction of prothrombin activator (calcium ions must be present)
Prothrombin - converted to thrombin
Thrombin acts as a enzyme to cause change of fibrinogen to fibrin, which trap platelets and blood cells to form a hematoma

Thrombus = a blood clot abnormally forming in a vessel
Embolus = when the clot moves and becomes lodged in another place