Blood

Collection of specialized cells that perform a particular set of tasks Collection of specialized cells that perform a particular set of tasks. It is considered a tissue even though it appears liquid. Average person has 5L of blood.

Functions: Links together all the body’s cells and organs. As it circulates around the body, it distributing materials. Blood absorbs nutrients synthesized by the cells in parts of the body other than the digestive tract, carries them to the liver where they are converted into storage products or prepared for transport to other body parts. Blood removes wastes products of cellular processes. Ex: uric acid, end product of protein metabolism is carried to the kidneys for processing and excretion.

Blood conveys chemical messages by transporting hormones from this various glands to the organs on which they act. Blood is key in disease-fighting. (see white blood cells) Blood transports oxygen needing for cellular respiration. (see red blood cells)

2 Distinct Elements in Blood 1. Plasma 2. Cellular Components - Liquid portion - Formed or solid portion made of water, gases, proteins sugar, vitamins, minerals and waste products. 1.Red Blood Cells 2.White Blood Cells 3.Platelets Leucocytes Lymphocytes

Cellular Components of Blood Red Blood Cells a.k.a Erythrocytes Make up 44% of total volume of blood. Red, Disc-shaped. No nucleus, instead it is packed with 280 000 million molecules of hemoglobin* Small size (8 μm) Specialized for oxygen transport. Originates from red bone marrow. Rarely lives more than three or four months.

* Hemoglobin molecules- allows for the transport of oxygen and carbon dioxide. Each contains four atoms of iron that contains a binding site (heme group). When the concentration of oxygen is high (ex: in the capillaries of the lungs) the heme group may form a loose bond with a molecule of oxygen.

When the concentration of oxygen is low (ex: in muscles during exercise), the acidity of the blood increases due to an increase in carbon dioxide. This weakens the bond between the heme group and oxygen and leads to the release of oxygen.

Carbon Dioxide Transport: Carbon dioxide is released by the cells in the body as a waste product of cellular respiration. About 40-45% of carbon dioxide enters the blood stream by binding to the hemoglobin. The remainder combines with water in the blood plasma forming carbonic acid (H2CO3).