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

Dietary Factors for RBC Production

• Two B-complex vitamins (B12 & Folic acid) are imp. for normal RBC production

• Both are needed for DNA synthesis• Lack of B12 – usually caused by a disorder of the

stomach lining not producing sufficient intrinsic factor (substance needed for B12 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.