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Part 1 of 1
Multicellular animals organize differentiated cells into four fundamental primary tissue types: 1. Epithelial Tissue: Closely packed sheets of cells covering external body surfaces, internal organ cavities, and glandular structures. Epithelial cells rest on a basement membrane with minimal intercellular space, providing protective barriers, selective absorption, and secretion. 2. Connective Tissue: Characterized by an abundant extracellular matrix (ECM) consisting of protein fibers (collagen, elastin) embedded in an amorphous ground substance, with relatively sparse living cells dispersed within it. Connective tissues provide structural support, physical protection, and metabolic integration (e.g. loose and dense fibrous connective tissue, cartilage, bone, adipose tissue, and blood). 3. Muscle Tissue: Excitable contractile tissue containing actin and myosin filaments responsible for mechanical force and motion: skeletal muscle (striated, voluntary, multinucleated), cardiac muscle (striated, involuntary, intercalated discs), and smooth muscle (non-striated, involuntary, spindle-shaped cells lining blood vessels and viscera). 4. Nervous Tissue: Composed of neurons specialized for electrical impulse transmission (action potentials) and neuroglia (glial cells) providing metabolic support and electrical insulation.
Blood is a specialized fluid connective tissue consisting of formed cellular elements suspended in liquid plasma: - Erythrocytes (Red Blood Cells): Biconcave discs that lack a nucleus and mitochondria in mature mammalian blood. They are densely packed with hemoglobin, an iron-containing quaternary protein whose primary physiological role is transporting molecular oxygen (O2) from the lungs to peripheral body tissues. - Leukocytes (White Blood Cells): Immune defense cells classified into granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (monocytes/macrophages and lymphocytes for antibody production and cell-mediated immunity). - Thrombocytes (Platelets): Anucleated cytoplasmic fragments derived from bone marrow megakaryocytes, essential for blood clotting and hemostasis.
Worked example
Step 1: Identify the tissue classification and functional adaptations of bone, cartilage, and circulating blood. Step 2: All three are classified as connective tissues because their functional properties are determined by their abundant extracellular matrix rather than tightly packed cells. Step 3: Bone has a mineralized, rigid matrix containing calcium hydroxyapatite and collagen; cartilage has a flexible, gel-like matrix rich in chondroitin sulfate; blood has a fluid matrix called plasma. Step 4: Specialized cell function: In blood, erythrocytes specialize in O2 gas transport via hemoglobin, while the plasma matrix carries dissolved nutrients, wastes, hormones, and clotting factors.
For the exam
1.Connective tissue is characterized by an abundant extracellular matrix separating sparse cells.
2.Erythrocytes (red blood cells) are primarily responsible for transporting oxygen throughout the human body.
3.Mature human red blood cells contain multiple diploid nuclei for active protein synthesis.
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