Tag: normal haemoglobin

The internal environment of the human organism is made up of blood within the blood vessels, interstitial fluid surrounding the body cells, and lymph inside the lymph vessels.

The blood is able to pick up:

• nutrients (from the digestive tract)
• oxygen (from the lungs)
• hormones (from the endocrine glands)
• enzymes (from multiple body sites)

The blood can also act as a transportation means for disease-causing organisms. For this reason, the lymphatic system helps in picking up wastes from the interstitial fluid, cleansing them of bacteria, and returning them bacteria-free into the blood.

Physical Characteristics of the Blood

Blood Functions

1. Transportation

Blood helps in the transportation of:

• Oxygen (from the lungs to the body’s cells)
• Carbon Dioxide (from the cells to the lungs)
• Nutrients (from the digestive organs to the cells)
• Waste Products (from the cells to the kidneys, lungs, and sweat glands)
• Hormones (from the endocrine glands to the cells)
• Enzymes (to various cells)

2. Regulation

Blood helps in the regulation of:

• pH (through buffers)
• Body Temperature (through heat-absorbing and coolant properties of its water content)
• Water within the Cells (mainly through dissolved sodium ions)

3. Protection

Blood helps in protecting the body against:

• Blood Loss (through the blood clotting mechanism)
• Toxins and Foreign Microbes (through special combat-unit cells such as white blood cells)

Blood Composition

Blood is made up of 2 portions:

1. Formed Elements

• make up 45% of the total blood volume
• include Red Blood Cells, White Blood Cells (Granular – neutrophils, eosinophils & basinophils; and Agranular – lymphocytes & monocytes), and Platelets.

2. Plasma

• makes up 55% of the total blood volume
• water (91.5% of total plasma)
• proteins (7% of total plasma)
• other solutes (1.5% of total plasma)

Haematopoiesis – Blood Cell Formation

Haematopoiesis a.k.a. blood cell formation takes place within the Red Bone Marrow (myeloid tissue in the humerus, femur, sternum, ribs, vertebrae & pelvis) and Lymphoid Tissue (in the spleen, tonsils & lymph nodes).

• Red Blood Cells, Leucocytes & Platelets are produced within the Bone Marrow.
• Agranular Leucocytes (lymphocytes & monocytes) are produced by the Bone Marrow and the Lymphoid Tissue.

Red Blood Cells a.k.a. Erythrocytes

Normal Haemoglobin Values

Infants	14-20gm/dl
Adult Females	12-15gm/dl
Adult Males	14-16.5gm/dl

Erythropoiesis – Erythrocyte Production

• erythropoiesis and erythrocyte destruction usually proceed at the same pace
• if the balance between erythropoiesis and erythrocyte destruction is disrupted, a homeostatic mechanism is initiated to promote erythrocyte production
• in oxygen deficiency, particular kidney cells release the enzyme Renal Erythropoietic Factor which converts plasma protein into the hormone erythropoietin, which, when reaching the red bone marrow, stimulates haemocytoblasts to develop into red cells

NOTE: Blast is a short name for an immature WBC, such as a lymphoblast or myeloblast. In normal circumstances, less than 5% of the cells in healthy bone marrow at any one time are blasts. Within the bone marrow, normal blasts develop into mature, functioning blood cells and are then released into the bloodstream.

Haemoglobin in Erythrocytes

• erythrocyte life span is around 120 days long
• the plasma membrane of depleted cells are removed from the circulation by macrophages in the spleen, liver, and bone marrow
• haemoglobin is broken down into Haemosiderin (iron-containing pigment which is stored or used in the bone marrow for the production of new haemoglobin for new RBCs), Bilirubin (pigment secreted by the liver into bile) and Globin (protein metabolised in the liver).

White Blood Cells a.k.a. Leucocytes

There are 2 types of WBCs:

GRANULAR LEUCOCYTES:

• NEUTROPHILS (POLYMORPHS) – make up the biggest amount of total leucocytes; involved in phagocytosis of bacterial pathogens and the release of antimicrobial chemicals
• EOSINOPHILS – involved in phagocytosis of antigen-antibody complexes, allergens and inflammatory chemicals, and the release of enzymes which help weaken or destroy parasites
• BASOPHILS – involved in the secretion of histamine which promotes blood flow to a particular tissue, and the secretion of heparin which promotes mobility of other WBCs by clotting prevention
• develop from red bone marrow
• have granules in the cytoplasm
• have a lobed nuclei

AGRANULAR LEUCOCYTES:

• MONOCYTES – turn into macrophages; phagocytise pathogens, dead neutrophils, and dead cells debris; and present antigens that activate other cells within the immune system
• LYMPHOCYTES – assist with immune memory, secrete antibodies, present antigens for the activation of other cells within the immune system, and help in destroying cancer cells, virus-infected cells, and foreign cells
• develop from lymphoid and myeloid tissue
• do not have granules in the cytoplasm

Differential Blood Count

Type of White Blood Cell	Normal Differential Count	High WBC Count Implication
Neutrophils	60% – 70%	damage caused by invading bacteria
Eosinophils	2% – 4%	allergic reaction
Basophils	0.5% – 1%	allergic reaction
Lymphocytes	20% – 25%	antigen-antibody reaction
Monocytes	3% – 8%	chronic infection

Life Span of Leucocytes

• leucocytes can live from just a few days to a few months, depending on what type of leucocytes they are
• during infection, white blood cells become very active, usually living for only a few hours

Platelets

Plasma

Plasma is made up of:

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