lab finals

• Blood


  Specialized type of loose connective tissue located within blood vessels

  
• Components of blood


  • Plasma (extracellular material; fluid matrix)
  • Formed elements (Erythrocytes, Leukocytes, Platelets)

  
• Erythrocytes


  Red blood cells

  
• Leukocytes


  White blood cells
• Types of leukocytes


  • Granulocytes (Neutrophil, Eosinophil, Basophil)
  • Agranulocytes (Lymphocytes, Monocytes)

  
• Platelets


  Cell fragments
• Hemopoiesis


  Production of the formed elements of blood

  
• Hemopoiesis


  • Derived from progenitor cells called stem cells (hematopoietic stem cells)
  • Occurs in the bone marrow
• Types of hemopoiesis


  • Erythropoiesis (erythrocytes)
  • Thrombopoiesis (platelets)
  • Granulopoiesis (granulocytes)
  • Monopoiesis/monocytopoiesis (monocytes)
  • Lymphopoiesis/lymphocytopoiesis (lymphocytes)

  
• Hemopoietic tissues


  • Embryonic (Yolk sac, Liver, Spleen, Bone marrow)
  • Adult (Myeloid tissue - Bone marrow, Lymphoid tissue - Bone marrow, Thymus, Lymph nodes, Spleen)

  
• Erythrocytes


  • Biconcave discs
  • Anucleate; no organelles
  • Most numerous cells in the blood
  • Size (Diameter 7.5 μm, Thickness at rim 2.6 μm, Thickness at center 0.75 μm)
• Platelets


  • Membrane-bound cell fragments; size: 2-4 μm
  • Produced by fragmentation of Megakaryocytes
  • Anucleate; but with mitochondria, ribosomes, Golgi complex, smooth and rough ER
• Platelet functions


  Hemostasis - arrest of bleeding after injury to blood vessel (platelet plug and clot formation)
• Components of the circulatory system

  • Cardiovascular system (Heart, Blood vessels)
  • Lymph vascular system (Lymph vessels)

  
• Histologic layers of the heart

  • Endocardium
  • Myocardium
  • Epicardium

  
• Endocardium


  • Thinnest histologic layer of the heart
  • Lines all internal surfaces of the heart and of the great vessels
  • 4 histologic layers (Endothelium, Subendothelium, Dense irregular connective tissue layer, Subendocardium)

  
• Myocardium


  • Thickest histologic layer of the heart
  • Thickest in the left ventricle, thinnest in the atria
  • Component: cardiac muscle fibers

  
• Epicardium


  • Synonymous with the visceral pericardium
  • Outermost histologic layer of the heart
  • Components: loose connective tissue covered lined externally by mesothelium, contains blood vessels, nerves, fat

  
• Classification of arteries based on diameter

  • Small (Arterioles)
  • Medium (Muscular arteries; Distributing arteries)
  • Large (Elastic arteries; Conducting arteries)

  
• Classification of veins based on diameter

  • Venules
  • Medium veins
  • Large veins
• Types of capillaries


  • Continuous (Type I)
  • Fenestrated (Type II)
  • Sinusoidal

  
• Continuous capillaries (Type I)


  • Continuous endothelium, no pores
• Fenestrated capillaries (Type II)


  • With pores ('fenestra' - window, hole)
  • Continuous basement membrane selective barrier
• Sinusoidal capillaries


  • Discontinuous endothelium (Large fenestrations)
  • Discontinuous basement membrane
• Lymph


  Water and plasma proteins plus lymphocytes and fat droplets (chylomicra)

  
• Lymphatic capillaries

  • Dead-end tubules, gradually join or anastomose in vessels of increasing size and terminate in the blood vascular system
  • Carries the fluid of the tissue spaces (interstitial fluid) that contributes to the liquid part of the lymph

  
• Lymphatic vessels

  Contains valves
• Lymphatic ducts

  Large lymphatic trunks where thin lymphatic vessels gradually converge and ultimately end up as the thoracic duct and the right lymphatic duct

  
• Components of the lymphoid system

  • Diffuse lymphoid tissue (Loose, Dense)
  • Nodular lymphoid tissue

  
• Diffuse lymphoid tissue


  • Cells: primarily T-lymphocytes
  • Arrangement: dispersed immune cells
  • Locations: entrances to the GIT, respiratory tract, GUT (genitourinary), MALT (GALT, BALT, NALT), Tonsils
• Nodular lymphoid tissue


  • Cells: primarily B-lymphocytes
  • Arrangement: Forms lumps called nodules
  • 2 Types of Lymphoid Nodules (Primary nodule, Secondary nodule)

  
• Lymphoid organs


  • Primary lymphoid organs (Bone marrow, Thymus)
  • Secondary lymphoid tissues/organs (Lymph nodes, Spleen, MALT)

  
• Thymus

  • Location: superior mediastinum
  • 2 pyramidal lobes fused together
  • Function: area for T-lymphocyte maturation
  • Parts (Capsule, Trabeculae, Cortex, Medulla)
• Thymus - Cortex


  • Cells are closely packed, numerous
• Thymus - Medulla


  • Thymic interdigitating dendritic cells present 'self' antigens to the T-cells
  • T-cells that reacts to the 'self' antigens are induced to undergo apoptosis
• Thymus - Hassall's bodies


  • Most distinctive feature of Thymic medulla
  • Core: hyaline material
  • Covering: flattened epithelioid cells
• Blood-thymus barrier

  • Found in the cortex
  • Prevents antigens from getting into contact with the developing T-cells
  • Components: Endothelial cells and basal lamina, Epithelioid cells and basal lamina, Perivascular space
• Lymph nodes


  • Bean-shaped organ
  • Encapsulated lymphoid tissue
  • Interposed along lymph vessels
  • Filtration site of lymph fluid
  • Activated T-cells and B-cells proliferate here and differentiate into different functional types

  
• Lymph node - Parenchyma


  • Has two regions: Cortex (Outer cortex - lymphoid nodules, Inner cortex - dense lymphoid tissue), Medulla (Dense lymphoid tissue arranged to form strands called medullary cords, Medullary sinuses)

  
• Spleen

  • Largest lymphoid organ in the body
  • Location: left upper quadrant of the abdominal cavity posterior to the upper part of the stomach
  • Histology: Capsule - dense irregular connective tissue, White pulp - lymphoid nodules, Red pulp - Splenic sinusoids, Splenic cords