BLOOD l Physiology MCQs for dental students

 

BLOOD l Physiology MCQs (multiple choice question) for dental students

 

INTRODUCTION IN BLOOD

Composition of blood:

•  Blood is composed of:

1.  Clear yellowish fluid called plasma (55% of blood volume).
2.  Cellular elements (45% of blood volume): RBCs & WBCs & Platelets.

•  Hematocrit value (packed cell volume):

1. It is the Percentage ratio of RBCs volume to total blood volume. or: Volume of RBCs in 100 ml of blood = 45%.

Physical properties of blood

   Color

•  Red due to presence of hemoglobin in RBCs. (Venous blood is bluish).

   pH

•  7.4 (7.35 - 7.45). (Venous blood is slightly acidic).

   Specific gravity (S.g)

•  blood = 1.060 (plasma = 1.030 & of RBCs = 1.090).

   Viscosity

•  Viscosity of blood is 5 times as water.
•  Caused by attraction between cells & plasma protein.

   Osmotic pressure

•  Due to presence of crystalloids: (electrolyte & plasma protein & sugar & waste product as urea).

Functions of blood:

1) Transport medium for:

• O2 & CO2 & absorbed food & waste product (urea & creatinine).

2) Defensive function:

• WBCs attack the organism by Phagocytosis or antibodies formation.
• Prevention of blood loss from injured vessels by clotting (Hemostasis).

3) Keep constant internal environment of the body (Homeostasis):

• Regulation of water content: by exchange of fluid between plasma and interstitial fluids also removal of excess fluids via kidneys.
• Regulation of pH: by plasma and RBCs buffer systems.
• Regulation of metabolism: by transport of hormones and vitamins.
• Regulation of body temperature: by transport of heat to skin.
• Regulation of arterial blood pressure: by its viscosity.

 

PLASMA

Volume: 

• 3 – 3.5 liter = (55% of blood volume & 5% of body weight).

Composition:

Water 90%.
Organic component

1.    Plasma proteins = 7.1 – 7.4 gm%.
2.    Other = 2% (nutrient & hormone & waste product).

Inorganic 0.9%.

PLASMA PROTEIN : 

• Total amount of plasma proteins = 7.1 – 7.4 gm%.

1. Albumin
2. Globulin
3. Fibrinogen
4. Pro thrombin

Functions of plasma proteins: 

Transport function (carrier):

• For minerals & hormones: to act as a store & prevent its loss in urine. .

Blood clotting (Hemostasis):

• Fibrinogen clotting factor (I), Prothrombin clotting factor (II)

Regulation of body fluids (regulation of osmotic pressure of blood):

• Plasma proteins have colloid osmotic pressure = 28 mmHg.
• This osmotic pressure lead to shift of fluids from tissue space to plasma  regulation of blood volume and prevent edema.
• Also, control urine volume by limitation of filtration by renal glomeruli in kidney.
• Although they represents only 28 mmHg, but they are more important because they do not cross the capillary.
• Albumin is responsible for this function mainly because it has highest concentration and lowest molecular weight. 

Defense (Immunity):

• By gamma globulin , which are secreted by Reticulo Endothelial System (RES).
• Globulin = antibodies = Immunoglobulin (Ig M & Ig A & Ig G & Ig E & Ig D). Water 90%. Organic component a) Plasma proteins = 7.1 – 7.4 gm%. b) Other = 2% (nutrient & hormone & waste product). Inorganic 0.9%.

Regulation of plasma viscosity:

• Which regulates peripheral resistance & blood flow & diastolic blood pressure.

Control of capillary permeability:

• Plasma proteins block the pores of capillary wall and prevent the removal of the cement substance of the capillary membrane.
• So, prevent loss of fluids from plasma to tissue space prevent edema.

Nutritional function:

• Plasma proteins can be used by the tissue in prolonged starvation.

Buffer function:

• Plasma proteins are amphoteric substances. Present as:

1.      Proteinic acid to buffer alkali. 
2.      Na proteinate to buffer acids.

CO2 carriage:

• Plasma proteins transport the CO2 as carbamine compounds. 

Specific functions:

• Some hormones & some enzymes are plasma proteins in nature.
• e.g. cholinesterase enzyme & Angiotensinogen.

 

Lymph Definition

• Lymph is a clear to pale-white fluid which circulates throughout the lymphatic system.
• The lymphatic system’s main role is to act as a filter against microbes, organic wastes and other debris.

Composition:

• The lymphatic system consists of numerous lymph nodes.
• These lymph nodes are connected to lymphatic vessels which circulate the lymph throughout the body.
• The lymph gets filtered at the lymph nodes. The spleen, tonsils, adenoids and the thymus all forms a part of the lymphatic system.
• The spleen is considered as the largest lymphatic organ in the system.
• Lymph consists of the following components:

1.      Carbohydrates
2.      Lymphocytes
3.      Creatinine
4.      Water – 94%
5.      Urea
6.      Chlorides
7.      Enzymes
8.      Very low amount of fat
9.      Proteins – Albumin, globulin, and fibrinogen
10.      Non protein nitrogenous substances as creatine ammonia ,uric acid and amino acids.

Function:

1. Body cells are kept moist by the lymph.
2. Lymph transports oxygen, food materials, hormones, etc., to the body cells and brings carbon dioxide and other metabolic wastes
3. It transport plasma protein macromolecules synthesized in the liver cells and hormones produced in the endocrine glands to the blood. These molecules cannot pass into the narrow blood capillaries but can diffuse into the lymphatic capillaries.
4. It absorbs and transports fat and fat soluble vitamins from the intestine. Lymphatic capillaries present in the intestinal villi are called lacteals which are associated with absorption and transportation of fat and fat soluble vitamins.
5. Lymph nodes produce lymphocytes. Lymph takes lymphocytes and antibodies from the lymph nodes to the blood.
6. It destroys the invading microorganisms and foreign particles in the lymph nodes.
7. Lymph maintains blood volume . As soon as the volume of the blood reduces in the blood vascular system, the lymph rushes from the lymphatic system to the blood vascular system

PLATELETS (THROMBOCYTES)

Shape & number & life span of platelet:

Platelets count : 

• 150,000 – 400,000/mm3. 

Life span :

• 8-12 days.

Count : 

• Decrease during menstruation
• Increase During pregnancy & exercise & high altitude & surgery & after splenectomy.
• Platelets are formed in bone marrow from megakaryocytes by thrombopoietin

RED BLOOD CELLS (ERYTHROCYTES)

Sites of formation of RBCs (Erythro-poiesis):

1. In infant & child: 

• Red bone marrow of all bones (all over the body).

2. In adult:

• Red bone marrow is restricted to the central skeleton (flat bones as skull, vertebrae, ribs, sternum, pelvis) also proximal ends of long bones.
• The remaining change into yellow marrow.
• Yellow bone marrow can be reactivated to red marrow to produce RBCs as in case of severe hypoxia (extra-medullary hemo-poiesis).