Blood

* Introduction

* Blood - connective tissue and a complex mixture of cells, chemicals, and fluids

* Blood transports substances (oxygen and nutrients) and helps to maintain a stable internal environment (homeostasis)

* Blood and Blood Cells

* Blood includes red blood cells, white blood cells, platelets, and plasma

* Blood volume and composition:

* A blood hematocrit is normally 45% cells and 55% plasma

* Plasma - mixture of water, amino acids, proteins, carbohydrates, lipids, vitamins, hormones, electrolytes, and cellular wastes

* Red Blood Cells

* Erythrocytes - biconcave disks that contain 1/3 oxygen - carrying hemoglobin by volume

* When oxygen combines with hemoglobin, bright red oxyhemoglobin occurs

* Deoxygenated blood (deoxyhemoglobin) is darker (ex: venous blood)

* Red blood cells discard their nuclei during development and so cannot reproduce or produce protein

* Reversible Deformity - allows red blood cells to squeeze through capillaries

* Structure - donut-like without the hole; 7.5x2 micrometers

* Gives maximum surface area to carry hemoglobin and oxygen

* Red Blood Cell Counts

* Typical red blood cell count 5,000,000 cells per mm^3

* 4,600,000-6,200,000 cells per mm^3 for males and 4,500,000-5,100,00 cells per mm^3 for females

* Males have more because of testosterone

* The number of red blood cells is a measure of the blood's oxygen-carrying capacity

* Red Blood Cell Production and Its Control

* In the embryo and fetus, red blood cell production occurs in the yolk sac, liver and spleen

* After birth - it occurs in the red bone marrow

* Average life span of a RBC - 120 days

* The total number of red blood cells remains relatively constant due to a negative feedback mechanism utilizing the hormone...