Specialized Connective Tissue Overview

Specialized Connective Tissue

• Specialized connective tissues include adipose tissue, hematopoietic tissue, bone, cartilage, and blood.

Adipose Tissue

• Components: Adipocytes (fat cells), areolar matrix
• Function: Stores energy in triglycerides, mobilized by lipase; insulates against heat loss, supports and protects organs.
• Types: White adipose tissue and brown adipose tissue.

White Adipose Tissue

• Location: Found in many organs
• Composition: 20% of body weight, very large cells (50-150 μm), single large lipid droplet. Nucleus pushed to the side of the cell.
• Function: Stores energy in triglycerides and fatty acids. Fatty acids released by lipase activity, carried by plasma proteins. Leptin regulates eating behavior.

Brown Adipose Tissue

• Location: 5% of newborn body weight, smaller amounts in adults.
• Composition: Smaller than white adipose tissue, many small lipid droplets (multilocular), numerous mitochondria, central nucleus.
• Function: Thermogenesis through metabolic processes.

Blood Tissue

• Components: Erythrocytes (red blood cells), Leukocytes (white blood cells [WBCs]), and Platelets; suspended in a fluid matrix (plasma)
• Function: Transports respiratory gases, nutrients, wastes, and other substances.
• Location: Contained within blood vessels.

Hematopoiesis

• Definition: The generation of all blood cells.
• Origin: All blood cells arise from a single type of Hematopoietic stem cell (HSCs)
• Characteristics: Hematopoietic stem cells (HSCs) are self-renewing; at least one daughter cell is a stem cell; some cells differentiate into other types of blood cells.
• Lineages: Lymphoid and myeloid

Composition of Whole Blood

• Components: Cells (erythrocytes, leukocytes, platelets) and plasma
• Plasma: 55% of whole blood, composed of water (92%), proteins (7%), and other solutes (1%).
• Buffy coat: Contains platelets and leukocytes (<1%)
• Erythrocytes: 44% of whole blood.
• Values: Erythrocyte count (adult male: 4.5-6 x 10^12/L, female: 4-5 x 10^12/L); Platelet count (150-450 x 10^9/L); Leukocyte count (4,500-11,000/µL), etc.

Plasma vs. Serum

• Plasma: Blood in its liquid state, clots.
• Serum: Plasma minus clotting factors; does not clot.

Preparing a Blood Smear

• Steps: Withdraw blood, place on a slide, use a second slide to spread blood thinly, stain, and cover with a coverslip.
• Purpose: Enables viewing of blood cell components.

Erythrocytes (Red Blood Cells)

• Life span: 120 days
• Origin: Derived from myeloid precursors in bone marrow. Normal counts are Male: 4.5-6 x 10^12/L, Female: 4-5 x 10^12/L.
• Shape: Nicely designed biconcave disk, about 7 µm wide and 2 µm thick.
• Structure: No nucleus, no mitochondria, spectrin, actin, ankyrin cytoskeleton. Cytoplasm: 65% water; 1% organelles; 3% hemoglobin.
• Flexibility: Flexible to move through capillaries.

Platelets

• Life span: 8-10 days
• Origin: Derived from megakaryocytes.
• Size: Normal number = 150-450 x 10^9/L; About 2 µm in diameter.
• Structure: Granulomere and hyalomere regions; no nucleus.
• Function: Help blood clot.

White Blood Cells (Leukocytes)

• Count: 4,500-11,000/µL.
• Differential: Reveals the proportion of different types of white blood cells (e.g., neutrophils, lymphocytes).
• Function: Leave circulatory blood and enter tissues (diapedes); various functions related to immune system.
• Types: Neutrophils, eosinophils, basophils, lymphocytes, and monocytes.

Neutrophils (PolyMorphoNuclear Leukocytes)

• Percentage: 45-75%.
• Structure: Multi-lobed nucleus, 15 μm in diameter; have specific granules (e.g., lysozyme, elastase, collagenase, cathelicidine, defensin) in cytoplasm; Azurophilic granules can be more prominent with bacterial infections.
• Function: First cells to enter infection sites, kill pathogens.

Eosinophils

• Percentage: 1-4%.
• Structure: Bi-lobed nucleus, 15 μm in diameter, large, bright pink (eosinophilic) granules. Cytoplasm - Major cell involved in allergic reactions, responsible for parasite infection.
• Function: Involved in allergic reactions and parasitic infections.

Basophils

• Percentage: Less than 1%.
• Structure: About 10 μm in diameter, tons of large, deep blue (basophilic) granules, irregularly shaped nucleus. Granules contain histamine, heparin.
• Function: Important in allergic and inflammatory responses.

Mast Cells

• Location: Tissues (connective, mucosal), not blood; neighbor to blood vessels.
• Function: release cytokines and histamine to induce inflammation. Have IgE receptor. Important in defense against parasites and allergic diseases.

Monocytes

• Percentage: 1-8%.
• Structure: Larger (12-20 µm), indented, oval, kidney or horseshoe-shaped nucleus ( "Raked" chromatin), gray-blue cytoplasm, sometimes with little vacuoles or granules.
• Function: Develop into macrophages, phagocytize dead cells and microbes, secrete cytokines, promote tissue repair.

Macrophages (Mononuclear Phagocytes)

• Types: Tissue resident macrophages (histiocytes), foreign body giant cells, Kupffer cells (liver), microglial cells (brain), alveolar macrophages (lung).
• Functions: Differentiate into various types in different organs; phagocytosis, antigen presentation, and repair processes.

Lymphocytes

• Percentage: 20-50% in blood.
• Types: B-lymphocytes and T -lymphocytes - Large granular lymphocytes (LGL). B-cells develop in the bursa of Fabricius (birds) and bone marrow (humans) and mature in lymph nodes and spleen. Produce antibodies in humoral immunity (extracellular pathogens).

T-Lymphocytes

• Percentage: About 85%.
• Development: Develop in bone marrow, mature in thymus.
• Functions: Cytotoxic T-cells kill infected cells, tumor cells; Helper T-cells help other immune cells to perform their jobs, function in cell-mediated immunity.

Natural Killer (NK) Cells

• Description: Large granular lymphocytes (LGL), larger than B and T cells (15µm in diameter).
• Function: Indiscriminately kill virus-infected cells and cancer cells.

Next Week: Muscle Tissues

Explore the fascinating world of specialized connective tissues, including adipose tissue and its two main types: white and brown adipose tissue. Understand their components, locations, and vital functions in energy storage and thermoregulation. Delve into how these tissues contribute to overall health and body weight management.