Chapter 14 Blood

Structure & Function Blood is a type of connective tissue (consists of cells in a matrix) Function – transports O2 & nutrients, maintains homeostasis, protection from blood loss & infection pH – 7.35-7.45 Volume – 5L (in avg. adult male) Temp. – 100.4 º F. Accounts for 8% of body weight Color varies from scarlet (O2 rich) to dark red (O2 poor)

Structure Composition – composed of 3 types of cells (called solid portion): 1. RBCs – erythrocytes 2. WBCs – leukocytes 3. platelets - thrombocytes

Structure The solid portion makes up 45% of a blood sample Called the hematocrit (HCT) or packed cell volume (PCV) Matrix (liquid portion) – plasma; clear, straw-colored Makes up remaining 55% of sample; mostly H2O, nutrients, etc.

Hematopoiesis – Production of blood cells (RBCs, WBCs & platelets)

Erythrocytes (RBCs) Structure: 1. biconcave disks three advantages: A. increase SA B. no point within the cytoplasm is far from the surface; ideal for gas exchange C. flexible; can squeeze thru tiny b.v.

Erythrocytes Structure: 2. Contain hemoglobin (Hb); allows them to carry resp. gases more efficiently 3. Mature RBCs lack nuclei; allows more room for Hb (each RBC is 1/3 Hb by volume) Normal RBC count: 4-6 million/mm³ of blood (in avg. adult) (slight incr. after meals or exercise; decr. from anemia, leukemia, or hemorrhage)

Hemoglobin Hb consists of the protein globin→ Each has 4 polypeptide chains & 4 heme groups (pigment) where O2 binds Hb combines easily w/O2 – called affinity ( or attraction) for O2 Produces oxyhemoglobin; makes blood bright red When O2 is released from the RBC, deoxyhemoglobin is produced; makes blood dark bluish-red

Hemoglobin Normal Hb levels – 14-18 gm/100 ml of blood (in avg. adult male) Cyanosis – occurs when O2 is deficient (hypoxia) & levels of deoxyhemoglobin incr. Symptoms – bluish lips & nail beds, dizziness, fainting, fatigue, muscle weakness

Leukocytes- WCBs 2 main classes: Granulocytes – have a grainy cytoplasm Agranulocytes – have a clear cytoplasm

Types There are 5 types of white blood cells: Granulocytes Neutrophils 40-75% Eosinophils 5% Basophils 0.5% Agranulocytes Lymphocytes 20-50% Monocytes 1-5% The range is because the requirement for different types of WBCs vary from time to time.

Neutrophils Structure: Multilobed nucleus Inconspicuous granules Amount: 3-7,000/mm³ Functions: Engulfing bacteria & viruses (phagocytosis) Life Span: hours → days

Eosinophils Structure: Bilobed nucleus Large, red granules Amount: 100-400/mm³ Functions: phagocytosis Protects against parasitic infections Neutralize histamines (their amts. incr. during hay fever & allergy attacks) Life Span – hours → days

Basophils Structure: Lobed nucleus Large granules, but fewer Amount: 20-50/mm³ Functions: Become mast cells when they leave b.v. & produce histamines Respond to allergens rapidly (anaphylactic shock) Produce heparin (anticoagulant) Life Span – hours → days

Monocytes Structure: Largest WBC U-shaped nucleus Grayish blue cytoplasm Amount: 100-700/mm³ Functions: Phagocytosis Become macrophages & remove dead cells Life Span – weeks → months

Lymphocytes Structure: Most numerous in children; 2nd most in adults Spherical nucleus Small “ring”of cytoplasm; pale blue Amount: 1500-3000/mm³ Functions: T cells – attack foreign antigens directly B cells – produce antibodies for immunity Life Span – months → lifetime

White Blood Cell Count Normal adult has 5,000-10,000 cells/mm3 Leukocytosis- WBC count above 10,000 cells/mm3 Can be a sign of acute infection Occurs during times of stress and vigorous exercise. Leukopenia- WBC below above 10,000 cells/mm3 Can be a sign of virus such as influenza, measles, mumps and HIV

Thrombocytes- Platelets Fragments of giant cells (megakaryocytes) (each produces b/t 5-10,000 platelets) Pieces break off these cells in bone marrow Enter circulation – live for approx. 1 wk.; destroyed by spleen & liver Disk-shaped, w/o nucleus ½ the size of an RBC Release serotonin to contract blood vessel walls.

Function Normal platelet count – 130,000-360,000/mm³ Stem blood flow (hemo- stasis) 2 ways: 1. Form a platelet plug 2. Initiate the clotting process

Platelet Plug Formation 1. B.V.damaged 2. Some blood escapes 3. Platelets adhere to each other & rough surfaces 4. When platelets come in contact w/collagen from connective tissue, they develop spiny projections; helps them adhere 5. Eventually platelet plug is formed & bleeding stops

Blood Clots Thrombus – blood clot that forms in a b.v. abnormally Embolus – blood clot or fragment of one that dislodges & travels to major organ

Plasma Clear, straw-colored fluid; matrix of blood 92% water Functions: 1. transport 2. maintain fluid balance 3. maintain pH

Contents of Plasma Contains 3 plasma proteins (all produced in the liver): Albumin – accounts for 60% of all plasma proteins - maintains osmotic pressure (keeps concentration of H2O & solutes in plasma stable - example – a decrease in albumin causes cells to lose H2O; it collects in interstitial spaces (b/t cells) & causes edema

Plasma Proteins Globulins – Accounts for 36% of all plasma proteins - transports lipids & vitamins Fibrinogen – Accounts for 4% of all plasma proteins - responsible for blood clotting

Other Substances Plasma also contains: nonprotein nitrogenous substances – amino acids, urea, uric acid electrolytes – release ions when dissolved in H2O; maintain osmotic pressure & pH; include Na, K, Cl, Ca Mg, bicarbonate, PO4 & SO4 ions