Lecture Notes: Connective Tissue in Histology

Introduction

• Platform: Da Vinci Academy Histology Video Course available on YouTube.
• Resources:
  • Histology playlist link in the description.
  • Practice questions & histology lab videos on the website.
• Lecture Focus: Connective tissue cells and types.

Key Cells in Connective Tissue

Fibroblasts

• Roles: Synthesize fibers (collagen, elastin) and ground substance.
• Forms:
  • Fibrocyte: Inactive form.
  • Fibroblast: Active form; synthesizes and secretes fibers.
• Microscopy:
  • Light Microscopy: Spindle/oval-shaped cells, pale eosinophilic cytoplasm.
  • Electron Microscopy: Prominent rough endoplasmic reticulum and Golgi apparatus.

Lymphocytes

• Types: T cells, B cells, Natural Killer cells.
• Histology: Dark round nucleus, thin cytoplasm.

Plasma Cells

• Role: Activated B lymphocyte, produces antibodies.
• Appearance: Eccentric nucleus, clock face nucleus, ghost-like appearance.

Eosinophils

• Function: Fight parasitic infections, mediate allergic reactions.
• Appearance: Eccentric bilobe nucleus, red eosinophilic cytoplasm.

Neutrophils

• Role: Markers of acute inflammation, phagocytosis.
• Histology: Multi-segmented nucleus, pale/pink cytoplasm.

Mast Cells

• Role: Mediate inflammatory reactions to allergens.
• Appearance: Round nucleus, numerous red granules.

Ground Substance in Connective Tissue

• Composition: Amorphous gelatinous material containing glycosaminoglycans and glycoproteins.
• Functions: Support, enable diffusion of nutrients and gases.

Key Molecules

• Glycosaminoglycans (GAGs): Polysaccharide polymers, attract water, form gel.
• Glycoproteins: Facilitate cell binding to extracellular matrix.

Types of Connective Tissue

Embryonic Connective Tissue

• Mesenchyme: Derived from mesoderm and neuroectodermal neural crest.
• Wharton's Jelly: Found in the umbilical cord, subdermal connective tissue.

Adult Connective Tissue

• Connective Tissue Proper:
  • Loose Connective Tissue: Loosely arranged collagen, abundant ground substance.
  • Dense Irregular Connective Tissue: Densely packed collagen, oriented in multiple directions.
  • Dense Regular Connective Tissue: Densely packed collagen, oriented in uniform direction; found in tendons, ligaments.

Special Connective Tissue

• Types: Elastic tissue, reticular tissue, adipose, cartilage, bone, hematopoietic tissue, lymphatic tissue.

Conclusion

• Resources: Practice questions and videos available on the Da Vinci Academy website.