Blood and Lymph: Liquid Connective Tissues

• Liquid connective tissues include blood and lymph.
• Lecture summary includes blood components, blood function, the immune system and the lymphatic system.

Classification of Adult Connective Tissue

• Connective tissues can be divided into connective tissue proper and fluid connective tissues.
• Connective tissue proper: Loose connective tissues have fibers creating a loose, open framework, including areolar, adipose, and reticular tissue where dense connective tissues have densely packed fibers including dense regular, dense irregular and elastic tissues
• Fluid connective tissues: Blood is contained in the cardiovascular system where Lymph is contained in the lymphatic system

Components of Blood

• Erythrocytes (red blood cells)
• Leukocytes (white blood cells), including: Monocytes, Lymphocytes, Eosinophil, Basophil, and Neutrophil
• Platelets

Blood Facts

• Temperature of blood is 38 degrees Celcius.
• Blood is 5 times more viscous than water, with dissolved proteins and formed elements.
• Average blood pH is 7.4, slightly alkaline.
• Blood volume is aproximately 4-5 liters.

Formed Elements

• Blood cells and cell fragments suspended in plasma are formed elements.
• Red blood cells (RBCs), white blood cells (WBCs), and platelets are formed elements.
• Formed elements are produced through hematopoiesis.
• Hemocytoblasts (PSCs) differentiate into myeloid stem cells or lymphoid stem cells.

Blood Transportation in the Cardiovascular System

• Blood flows from arteries to arterioles and then to capillaries where diffusion between capillaries and interstitial fluid occurs.
• Blood flows from capillaries to venules to veins.
• Oxygenated blood flows through arteries and deoxygenated blood flows through veins.

Capillaries

• If all capillaries were aligned end to end, they would circle the earth.

Blood Function

• Blood is responsible for the transport of dissolved gases, nutrients, hormones, and metabolic waste.
• Participates in the regulation of pH and ion composition of interstitial fluid, by regulating ion levels and eliminating acid buildup
• Restricts fluid loss with enzymes that respond to breaks in vessels allowing for clotting
• Defends against pathogens and toxins with WBCs, antibodies, and specialized proteins, creating stable body temperatures by absorbing generated heat from skeletal muscles

Plasma Proteins

• Proteins in solution.
• Similar to interstitial fluid.
• Plasma contains 7.6g per 100ml of plasma.
• Interstitial fluid has five times less proteins.
• Three protein classes are Albumins, Globulins, and Fibrinogen.
• Albumins make up 60%, contribute to osmotic pressure and act as transporters.
• Globulins make up 35%, are antibodies/immuno and transport globulins.
• Fibrinogen assists in clotting and molecules interact making insoluble fibrin strands, which are a framework for a blood clot.
• 1% are other proteins with specialized functions.

Blood Hematocrit

• Blood haematocrit is the % of whole blood occupied by red blood cells.
• Females average 42%.
• Males average 46%.
• Male sex hormones (androgens) stimulate red blood cell production.
• Blood can be separated out by centrifugation.

Centrifuged Blood

• Centrifuged blood separates into Plasma (55% of total blood), Buffy Coat (leukocytes & platelets, <1% of total blood), and Erythrocytes (45% of total blood).

Clinical Relevance regarding Blood Hematocrit

• Anemia: Decreased hematocrit.
• Polycythemia: Increased hematocrit (>65%).

Red Blood Cells (RBC)

• 99% of formed element
• Contain red pigment – haemoglobin – binds O2/CO2
• 4-6 million RBC/ul
• Biconcave disc
• Large SA:volume - efficient gas exchange (total 3800 sqm)
• Very flexible
• Stack and flow

Haemoglobin

• Hemoglobin is 95% of RBC protein.
• Grams of Hb per 100ml of whole blood.
• Composed of two alpha and two beta polypeptides.
• Each Hb chain has a haem (pigment) and binds O2 - shade difference.

Blood Histology Wright's Stain or Giemsa

• Includes Erythrocytes, Neutrophils, Platelets, Basophilic myelocyte, Medium lymphocyte, Basophilic Erythroblast, Plasma cell, Small lymphocyte, Neutrophilic myelocytes and Eosinophil.

Erythropoiesis

• Erythropoiesis refers to the formation of RBCs.
• Occurs in red bone marrow.
• In extreme situations, yellow marrow converts to red marrow.

Blood Production - Haematopoiesis

• Early differentiation separates myeloid stem cells from the lymphoid stem cells.
• Multipotent stem cells in red bone marrow divide to produce specific stem cells.
• Myeloblasts, Monoblasts, and Lymphoblasts produce the White blood cells.

Clinical Relevance in Blood Production

• Sickle cell anemia: An autosomal recessive disorder.
• A mutant Hb gene leads to mutant Hb protein Hb-S.
• When Hb-S gives up O2, it forms rodlike structures.
• Results in 'Crisis'- pain and damage due to blocked capillaries.

White Blood Cells (Leukocytes)

• Role in immune system and removal of foreign and defective cells.
• Contains a nucleus.
• 6-9000/ul.
• Larger than RBC.
• Located in connective tissue proper or lymph organs.

Leukocytes

• Granulocytes include Neutrophils, Eosinophils, and basophils that contain granules that are vesicles and lysosomes
• Agranulocytes = are Monocytes and Lymphocytes that are non-granular

Ranking white blood cells

• Ranking in order = Never Let Monkeys Eat Bananas
• Neutrophils (60-70%) ; Lymphocytes (20-40%); Monocytes (3-10%); Eosinophils (1-4%); Basophils (~1%)

Granulocytes- Neutrophils

• Most common- (50-70% of WBC)
• 10-12µm diameter
• 2-5 lobed nucleus
• Lysosomal and bactericidal granules
• First to injury site AND are Cell scavengers/Phagocytes

Granulocytes- Eosinophils

• Eosin +ve granules
• Rare (2-4% of WBC)
• 10-12µM
• Exocytosis of toxic compounds AND attack antibody coated objects
• Increased in allergic conditions and internal parasitic infections

Granulocytes- Basophils

• 0-5-1% (most rare!)
• 8-10µm diameter
• migrate to injury site
• Release histamine which dilates blood vessels and heparin which prevents blood clotting

Agranulocytes- Monocytes

• 12-2µm diameter and the largest WBC
• 3-8% of WBC with a Kidney shaped nucleus
• Circulate in Blood for 2 days, then mature in tissues with a Cell-mediated immunity
• Mature into macrophages

Agranulocytes- Lymphocytes

• Smallest WBC diameter 8-10μm
• 20-30% of WBC aith a large nucleus
• B-cells - that differentiate into plasma cells (antibody production)
• T-cells - CD4 and CD8
• NK (natural killer) – immune surveillance and destruction of abnormal tissue (cancer)

Clinical Significance of WBC abnormality

• Abnormal WBC multiply uncontrollably
• Decreased normal blood cell production

Platelets

• Can look spindle shaped in smear
• Are Fragments shed from cytoplasm of megakaryocytes
• In BM, slowly sheds cytoplasm in membrane enclosed packages
• Around !4000!
• 2-4µm diameter
• Role in blood clotting – they make clotting factors which include (III, IV, V, VIII and XIII)
• Lifespan of 9-12 days
• Removed in spleen by phagocytes

Clinical Significance of Clotting

• Hereditary disorder mostly affects males
• Clotting factor formation is inadequate (factor VIII)
• Delayed clot formation can lead to hemorrhage

The Lymphatic System

• Lymphatic capillaries and vessels
• Lymphocyte producers like Lymphoid tissue and Lymphoid organs produce and distribute lymphocytes

Comparison of a small Vein and Lymphatic vessel

• Valveless Vein is filled with Erythrocytes
• Lymphatic vessel that has a Valve-like structure is filled with Lymphatic

Characteristics of Lymph

• Blood plasma components pass through capillary walls into interstitial fluid
• Concentration gradient prevents flow from interstitial fluid to blood
• Passes into permeable lymph capillaries

Collecting drainage - Lymphatic capillaries

• Capillaries deliver more liquid to tissues than they carry away and residual liquid 15% is returned via lymphatic system which Helps distribute lymphocytes, hormones, nutrients from Interstitial fluid

Characteristics of Lymphatic capillaries

• Branch through peripheral tissues but are Not present in CNS, BM or cornea
• Originate in blind pockets cul-de-sac with a Large diameter and thin endothelial walls
• Absent/incomplete basement membrane with a un-tight valve structure creating a one directional flow of Iymph

Lymphatic Vessels

• Vessels always have valves ensuring flow from trunk to thoracic cavity
• Present in almost tissue and Plasma fills interstitial fluid which flows through the lymphatic system

Lymphoid Tissue - The Tonsils

• Connective tissue that is dominated by lymphocytes that is located are large nodules in pharynx wall
• Germinal centers in area contain dividing lymphocytes.

Lymphoid Organs

• A fibrous connective tissue capsule separates these organs which include Lymph nodes, the thymus and the spleen.

Lymph Nodes

• Are shaped like Kidney beans and are Small, oval, 1-2mm
• Collagen fibers extend in the organ
• Helium is where blood attachment
• Afferent lymphatics - carry in
• Efferent lymphatics - carry lymph away

Lymph Node function

• Acts like Kitchen water filter Purifying lymph before it is sent to the venous system Removing 99% antigens
• Macrophages phagocytose AND Antigen is presented to lymphocytes which Strategically positioned to avoid infection

Thymus

• The organ is divided into Right and left lobes
• Septa separate out the lobes into lobules
• Contains many lymphocytes
• ProducesThymosin

Spleen

• Largest collection of tissue acting like lymph nodes but also performing certain function for blood.

Spleen Function

• Recycles red blood cells and Initiates of immune responses

Spleen Function Continued

• 12cm
• Contains a Capsule made of collagen and elastin and the organ is filled with Trabecula of blood vessels
• Consists of Red pulp which is blood+ fixed macrophages in network of reticular fibers
• White pulp has rich variety of immune cells

Lymph Flow

• What aids lymph flow?

1. Smooth muscle contraction
2. Skeletal muscle contraction
3. Inhalation

Clinical significance

• Blockage of lymph vessels that causes fluid to accumulates interstitially and retain proteins leading
• Filarisis from Nematodes infecting lymph nodes which can ultimately turn into Elephantiatis

Concise lecture notes about liquid connective tissues, namely blood and lymph. Key topics covered are blood components, blood function, the immune system and the lymphatic system. Also covers classification of adult connective tissue and blood facts.