A&P 11 Chapter 14

What might cause abnormal hematocrit values?

Low hematocrit may be caused by anemia, poor nutrition or chemotherapy (in people undergoing cancer treatment). High hematocrit might be caused by dehydration or excess production of red blood cells.

How does the biconcave shape of a red blood cell make possible its function?

The biconcave shape increases the surface area through which gases can diffuse and places the cell membrane closer to the hemoglobin. It also prolongs the lifespan of a RBC, by providing flexibility, so that when it hits blood vessel walls, it bends instead of rupturing. The flexibility also helps a RBC squeeze through narrow capillaries, where it can drop off oxygen and pick up carbon dioxide.

Describe a red blood cell.

A red blood cell (RBC) is a biconcave disc (thinner in the center than at the rim). A mature red blood cell has no nucleus and very few organelles. About one-third of a RBC consists of hemoglobin.

How do blood cells form?

Blood cells form from the division and differentiation of hematopoietic stem cells in the red bone marrow. The process of blood cell formation is called hematopoiesis

What is the typical red blood cell count for an adult male? for an adult female?

An adult male has 4,700,000-6,100,000 red blood cells per microliter of blood. An adult female has 4,200,000-5,400,000 red blood cells per microliter of blood.

What is anemia?

Anemia is a disorder in which there is an abnormal reduction in the number of red blood cells or in the amount of hemoglobin in each RBC.

What factors affect blood volume?

Blood volume is affected by gender, body size, amount of adipose tissue that a person has, and variations in fluid and electrolyte balance.

How might chronic lung disease result in polycythemia?

Chronic lung disease (like emphysema) decreases the surface area in the lungs for gas exchange. The kidneys and liver sense the low oxygen level in the blood, and interpret it as a need to produce more red blood cells (RBCs). They secrete erythropoietin (EPO), which increases the rate of RBC production. But since this is not actually the problem, the oxygen level continues to be low, and the liver and kidney continue to secrete more EPO. This cycle can result in polycythemia, an abnormal increase in the number of RBCs in the body.

What happens to damaged red blood cells?

Damaged red blood cells rupture as they pass through the liver and the spleen, where macrophages phagocytize them. Hemoglobin molecules are decomposed; some portions are recycled and some are excreted.

What metabolic pathway do erythrocytes use to produce ATP?

Erythrocytes (RBCs) use glycolysis to produce ATP, since they lack mitochondria.

How is hematocrit determined?

Hematocrit is determined by centrifuging a blood sample in a capillary tube, and measuring the percent of packed red blood cells in the total volume of blood.

How does a red blood cell change as it matures?

Hematopoietic stem cells reproduce and give rise to erythroblasts, which then reproduce. As an erythroblast matures, it produces hemoglobin, the nucleus shrinks, and then the nucleus is extruded from the cell. The remaining cell becomes a reticulocyte. The reticulocyte leaves the red bone marrow and enters the blood, where it loses its remaining organelles, and matures into an erythrocyte.

What are the products of hemoglobin breakdown?

Hemoglobin breakdown produces amino acids, iron, biliverdin, and bilirubin

What is the function of hemoglobin?

Hemoglobin transports oxygen and some carbon dioxide through the blood.

Where are red blood cells produced?

In the fetus, red blood cells are produced in the yolk sac, liver and spleen. After birth, they are produced only in the red bone marrow.

Why is iron required for the formation of red blood cells?

Iron is required for hemoglobin synthesis, and hemoglobin is a major part of the red blood cell.

What is positive chemotaxis?

Positive chemotaxis is the attraction of leukocytes to an infection site by chemicals released from damaged cells.

How is red blood cell production controlled?

Red blood cell (RBC) formation is regulated by the hormone erythropoietin, via a negative feedback mechanism. Oxygen deficiency leads to the secretion of erythropoietin from the kidneys, with a smaller amount from the liver When the number of RBCs became adequate to transport oxygen to the body cells, negative feedback decreases the secretion of erythropoietin, and RBC production decreases.

What are the major components of blood?

The major components of blood are the plasma, which is the liquid portion, and the formed elements, which consist of red blood cells, white blood cells, and platelets.

Which vitamins are necessary for red blood cell production?

Vitamin B12 and folic acid, another B vitamin, are necessary for DNA synthesis and cell division of the hematopoietic stem cells that produce red blood cells

How do white blood cells reach microorganisms outside blood vessels?

White blood cells leave small blood vessels by diapedesis, in which they squeeze between adjacent cells of the blood vessel walls. After leaving the blood vessels, they propel themselves by amoeboid motion.