BLOOD TISSUE

PHYSIOLOGY


BLOOD TISSUE


Circulating connective tissue.

Composition of blood can be easily discerned in a

tube of centrifuged blood .......................................this is a centrifuge in which the test tube is spun apprx 1000 rpm
bloodsample.jpgcentrifuge.jpg


Plasma ~ 55% and erythrocytes ~ 45% of blood. The %volume of erythrocytes is referred to as the haematocrit. A low haematocrit can be an indication of anaemia. While a high haematocrit may be good for the oxygen carrying capacity of the blood, it may cause the blood to be too viscous, making circulation more difficult.

FORMATION OF BLOOD COMPONENTS
Haemopoiesis.jpg
Haemobone.jpg


Erythrocytes : Describe structure and functions-------------------------------------------------------------------------------------White blood cells (leukocytes) structure and functions of each type

erythrocytes.jpgleukocytes.jpg


Erythrocytes:
life span 120 days

Worn rbc’s broken down in liver and spleen by fixed phagocytic macrophages:

  • Globin broken down into amino acids that can be reused for protein synthesis
  • Heme separated and iron removed
— serum ferritin

  • Fe (3+) can be reused for Hb production

  • Heme broken down:

- biliverdin (green)

- bilirubin (yellow-orange) to liver - bile

- urobilinogen - in colon by bacteria

- urobilin - yellow - kidneys - urine

- stercobilin - excreted in faeces

Leukocytes

Granulocytes:

Neutrophils, Basophils, Eosinophils
Agranulocytes:

Lymphocytes & Monocytes
Life span

depends on immune system

ranges from few days to few years
Lymphocytes

T and B cells and Natural Killer (NK) cells

Soldiers patrolling the body - all over the show
T cells : attack viruses, fungi, transplanted cells, cancer cells, some bacteria,

transfusion reactions, rejection of transplanted organs
B cells : destruction of bacteria and inactivating their toxins also immune responses
NK cells: attack a wide variety of infectious microbes and certain tumour cells
Monocytes

Macrophages (large eaters)

= fixed remains in a specific organ/tissue eg. alveolar macrophages , macrophages in spleen ,

stellate reticuloendothelial (Kupffer) cells in liver.

= wandering macrophages - roam tissue and rush to places of trauma, infection or inflammation

Mop up function at sites of injury cf. Osteoclasts

Abundant during viral and fungal infections, TB and other chronic diseases
Neutrophils

chemotaxic, contain human defensins- antibiotic properties

Bacterial attack on tissues attracts neutrophils that rapidly responds and destroy bacteria by chemicals such as the enzyme lysozyme
Basophils

Release granules containing heparin, histamines and serotonin = enhance the inflammatory reaction

– allergic reactions/hypersensitivity

Increased levels also with cancers and hypothyroidism
Eosinophils

combats allergic reactions with histaminase

phagocytic: antigen-antibody complexes, auto-immune diseases

ALL Leukocytes, like all nucleated cells, possess Major Histocompatibility Complex (MHC) proteins on their cell surfaces to ‘recognize’ the other cells - cf. auto-immune diseases and

matching for transplants and grafting.
Movement of cells

diapedesis = emigration = amoeboid movement of leukocytes through endothelial tissue
Macrophages and Neutrophils = phagocytosis - attracted by chemicals secreted by foreign

substances = chemotaxis

Platelets/ Thrombocytes
Plays a role in hemostasis- prevents excessive loss of blood.

Cf. Thrombosis - stagnation, inactivity.

Blood Grouping
AA ; AO = blood group A ................................ NB* O indicates the absence of A or B

BB ; BO = blood group B

AB = AB

OO = O ................. does not contain the antigens A or G

In addition - presence of the rhesus factor would be indicated as follows: (Rh) + (positive)
.................absence - Rh - (negative)

Groups are indicated as
A+ or Apos; B - or B neg etc.
Remember: It is not A+ thing to B - about Blood Groupings

Task
Determine universal donor and explain your answer.

Determine universal acceptor/recipient and explain your answer.


HEMOSTASIS
Prevents haemorrhage , process of blood clotting
1. Vascular spasm - localised, focussed vasoconstriction - few minutes to hours

2. Platelet plug formation : Clotting Factors , Ca++ , serotonin released from vesicles platelet adhesion, ADP makes platelets in immediate area sticky = platelet aggregation

3. Coagulation: Exposed prothrombin converted to thrombin
fibrinogen in presence of thrombin — fibrin strands that traps other formed elements.

Serum changed by presence of clotting factors, that includes Ca++

Extrinsic Pathway - factors from surrounding cells help to form clot - rapid response
Intrinsic Pathway - only factors (I - XIII) and others within are of clot
Common Pathway - where the two mechanisms link and follow one path

Vit K is required for the formation of some clotting factors

4. Clot retraction: Once area is safe, fibrin threads shrink and pull on platelets and pull the ends of the severed vessel together. As the clot shrinks the vessel closes up. The PDGF (Platelet derived growth factor) a hormone released by the platelets, cause proliferation of endothelial cells, vascular smooth muscle fibres, and fibroblasts to help repair the damaged blood vessel.

HEMOSTATIC CONTROL MECHANISMS
Fibrolytic system - fibrinolysis by plasmin (fibrinolysin)
many substances manufactured by endothelial cells play a role in preventing clotting and/or breaking down small clots when they are formed.

Heparin, produced by mast cells and basophils, combines with antithrombin and increases effectiveness of blocking the action of thrombin.

INTRAVASCULAR CLOTTING


Thrombosis - READ UP AND PROVIDE EXAMPLES OF CASES eg. suits against airlines for deaths or diseases due to thrombosis.

DVT = Deep Vein Thrombosis

May-Thurner syndrome is a rare condition in which blood clots, called deep venous thrombosis (DVT), occur in the iliofemoral vein due to compression of the blood vessels in the leg. The specific problem is compression of the left common iliac vein by the overlying right common iliac artery. This leads to pooling or stasis of blood, predisposing the individual to the formation of blood clots.


Diseases of the blood

Provide a short description of each of the following conditions.:

leukaemia
sickle cell anaemia ; iron-deficiency anaemia ; megaloblastic anaemia ; pernicious anaemia ; haemorrhagic anaemia ; haemolytic anaemia ; thalassaemia ; aplastic anaemia
polycythaemia
erythroblastosis fetalis
leukocytosis
leukopenia
haemophilia
haemolysis following blood transfusion : Consider what will happen if a person with blood type A receives blood type B.
thrombocytopaenia
septicaemia ; viraemia

What is / a(n)
phlebotomist ; haematologist ; virologist
cupping











THE CARDIOVASCULAR SYSTEM refer to next file for this section

ANATOMY OF THE SYSTEM