Blood Part 1 Chapter 10 Blood Blood Is

Blood – Part 1 Chapter 10

Blood �Blood • Is the “river of life” that surges within us. • It transports everything that must be carried from one place to another within the body – nutrients, wastes, and body heat – through blood vessels. • Is the only fluid tissue.

Composition of Blood �Blood contains both solid and liquid components. 1. Formed Elements – Cellular portion of blood. �Contains living blood cells. 2. Plasma – The fluid portion of the blood. �Nonliving fluid matrix.

Composition of Blood � If blood is spun in a centrifuge, 3 layers are formed: 1. Bottom Layer - The heavier formed elements are packed down by centrifugal force. �Most of the reddish mass at the bottom is erythrocytes (RBC that function in O 2 transport). 2. Top Layer - The lighter plasma rises to the top. 3. Buffy Coat - Thin, whitish layer between the formed elements layer and the plasma layer. �Contains leukocytes (WBC that act in various ways to protect the body) and platelets (cell fragments that function in blood clotting).

Percent Composition of Blood �Percent of the total volume of blood: • Erythrocytes: 45% �Percentage known as hematocrit • WBC and Platelets: <1% • Plasma: 55%

Physical Characteristics of Blood �Texture: Sticky opaque fluid; Heavier than water and about 5 times thicker (more viscous) than water �Taste: Metallic and salty �Color: Varies from scarlet (oxygen-rich) to dull red (oxygen-poor)

Physical Characteristics of Blood �p. H: Slightly alkaline (p. H between 7. 35 and 7. 45) �Temperature – Always slightly higher than body temperature (100. 4°F) �Body Weight and Volume: Accounts for approximately 8% of body weight; Volume in healthy males is about 5 -6 L

Plasma �Plasma – The liquid part of the blood. • Is ~90% water. • Over 100 different substances are dissolved in this straw-colored fluid. �Examples include: nutrients, salts, respiratory gases, hormones, plasma proteins, and various wastes • Functions: 1. Transports various substances around the body. 2. Helps to distribute body heat evenly throughout the body.

Plasma Proteins �Plasma Proteins – The most abundant solutes in plasma. • Serve a variety of functions: 1. Albumin – Contributes to the osmotic pressure of blood, which acts to keep water in the bloodstream. 2. Clotting Proteins help stop blood loss when a blood vessel is injured. 3. Antibodies help protect the body from pathogens. 4. Plasma proteins are NOT taken up by the cells to be used as food fuels or metabolic nutrients.

Composition of Plasma � The composition of blood plasma varies continuously as cells remove or add substances to the blood. • The composition of plasma is kept relatively constant by various homeostatic mechanisms. �When blood proteins drop to undesirable levels: Liver is stimulated to make more proteins. �When the blood starts to become too acidic or too basis: The respiratory system and the kidneys are called into action to restore it

Formed Elements � Make up about 45% of whole blood. � Contains erythrocytes or red blood cells (RBCs). • Function: To ferry O 2 to all of the cells of the body. • Contain no organelles. �Lacks both a nucleus and a mitochondria �Make ATP by anaerobic mechanisms, they do not use up any of the O 2 they are transporting. • Are literally sacs of hemoglobin (Hb). �Hemoglobin - An iron-containing protein that transports the bulk of the oxygen that is carried by the blood.

Shape of Erythrocytes � Are small cells shaped like biconcave disks. • Flattened discs with depressed centers. • They look like doughnuts when viewed through a microscope. • Their small size and peculiar shape provide a large surface area relative to their volume, making them ideally suited for gas exchange.

Number of Erythrocytes (RBCs) � RBCs outnumber WBCs by about 1000 to 1. � Are the major factor contributing to blood viscosity. • When the number of RBCs increase, blood viscosity increases. • As the number of RBCs decrease, the blood thins and flows more rapidly.

Hemoglobin �The more hemoglobin molecules the RBCs contain, the more O 2 they will be able to carry. • Each hemoglobin molecule can bind 4 molecules of O 2

Hemoglobin (Hb) � The most accurate way of measuring the oxygen-carrying capacity of the blood is to determine how much Hb it contains. • A single RBC contains ~250 million Hb molecules. �Each Hb molecule can bind 4 molecules of O 2. Therefore, each of these tiny RBCs can carry about 1 billion O 2 molecules! � The Hb content is slightly higher in men than women.

Anemia �Anemia – A decrease in the oxygen-carrying ability of the blood. • May be the result of: 1. Lower-than-normal number of RBCs 2. Abnormal or deficient hemoglobin content in the RBCs

Sickle Cell Anemia � Sickle-Cell Anemia – Genetic defect that leads to abnormal Hb, which becomes sharp and sickle-shaped under conditions of increased O 2 use by the body. • The deformed (crescent-shaped) RBCs rupture easily and dam up in small blood vessels. �These events interfere with oxygen delivery and cause severe pain.

Sickle Cell Anemia � Occurs chiefly in black people, who live in the malaria belt of Africa and among their decendants. • Individuals with the sickle-cell gene have a better chance of surviving where malaria is prevalent. �The same gene that causes sickle cell anemia, also makes RBCs infected by the malaria-causing parasite stick to the capillary walls and then lose potassium (an essential nutrient for the survival of the parasite). �The malaria causing parasite is prevented from multiplying.

Polycythemia` �Polycythemia – An excessive or abnormal increase in the number of erythrocytes. • May result from: 1. Bone marrow cancer 2. Normal physiological response to living at high altitudes, where the air is thinner and less oxygen is available. • Major problem that results from high numbers of RBCs is increased blood viscosity. �Increased blood viscosity causes RBCs to flow sluggishly in the body and impairs circulation.

Leukocytes �Leukocytes – White blood cells (WBCs); crucial to the bodies defense against disease. • Far less numerous than RBCs; Account for >1% of total blood volume. • Form a protective, moveable army that helps defend the body against damage by bacteria, viruses, parasites, and tumor cells.

WBCs: Special Characteristics 1. Are able to slip into and out of the blood vessels – a process called diapedesis. • The circulatory system is simply their means of transportation to areas of the body where their services are needed for inflammatory or immune responses.

WBCs: Special Characteristics �Can locate areas of tissue damage and infection in the body by responding to certain chemicals that diffuse from the damaged cells. • Called positive chemotaxis.

Positive Chemotaxis � Once they have “caught the scent, ” the WBCs move through the tissue spaces by ameboid movement. • Ameboid Movement - Flowing cytoplasmic extensions that help them move. � By following the diffusion gradient, they pinpoint the areas of damage and rally round in large numbers to destroy foreign substances or dead cells.

Number of WBCs �Whenever WBCs mobilize for action, the body speeds up their production. • As many as twice the normal number may appear in the blood within a few hours.

Number of WBC’s � Leukocytosis – A total WBC count above 11, 000 cells/mm 3 • Generally indicates that a bacterial or viral infection is stewing in the body. � Leukopenia – Abnormally low WBC count. • Commonly caused by certain drugs, such as corticosteroids and anticancer agents.

Leukemia �Leukemia – “White blood”; Bone marrow becomes cancerous; Excessive production of abnormal WBCs. • The “newborn” WBCs are immature and incapable of carrying out their normal protective functions. • Consequently, the body becomes easy prey of disease-causing bacteria and viruses.