Chapter 14 Blood

Structure & Function Blood is a type of connective tissue (consists of cells in a matrix) Function – transports O 2 & nutrients, maintains homeostasis, protection from blood loss & infection pH – Volume – 5L (in avg. adult male) Temp. – º F. Accounts for 8% of body weight Color varies from scarlet (O 2 rich) to dark red (O 2 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 H 2 O, 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 O 2 binds Hb combines easily w/O 2 – called affinity ( or attraction) for O 2 Produces oxyhemoglobin; makes blood bright red When O 2 is released from the RBC, deoxyhemoglobin is produced; makes blood dark bluish-red

Hemoglobin Normal Hb levels – gm/100 ml of blood (in avg. adult male) Cyanosis – occurs when O 2 is deficient (hypoxia) & levels of deoxyhemoglobin incr. Symptoms – bluish lips & nail beds, dizziness, fainting, fatigue, muscle weakness

Dietary Factors for RBC Production Two B-complex vitamins (B 12 & Folic acid) are imp. for normal RBC production Both are needed for DNA synthesis Lack of B 12 – usually caused by a disorder of the stomach lining not producing sufficient intrinsic factor (substance needed for B 12 absorption) Iron (Fe) – needed for production of Hb (Vit C increases absorption of Fe in the digestive tract) Anemia – deficiency or destruction of RBCs (see Table 14.4 – Types of Anemia in text)

Control of RBC Production

Life Cycle of an RBC

Destruction RBC RBC break down from wear and become ruptured when travelling through the kidney and spleen. Macrophages break down RBC and their contents. Hemoglobin breaks down into 4 globin groups and heme groups Heme breaks down into biliverdin (green pigment)

Destruction of RBC cont. Biliverdin breaks down into bilirubin (orange) The iron gets reused to make more hemoglobin or is stored in the liver as ferritin.