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Hey team! Quick tour of how tissues repair and remodel. Two mini-cases, zero stress. Ready? Case one: a small epithelial wound, like a scraped cheek lining. – First, cells at the edge loosen their junctions on purpose. Tight junctions and adherens junctions relax a bit so cells can wiggle. You’ll see widened spaces and less crisp junction staining in early histology. – Then they migrate. Picture a crawling front: actin pushes out little lamellipodia, and integrins grab onto a provisional ECM—think fibronectin—like suction cups. In slides, look for a flat, squamous “migrating sheet,” fewer microvilli, and a fibronectin-rich base. – After coverage, they rebuild. Junctions re-tighten, polarity snaps back—apical up, basal down—and barrier proteins like claudins reappear. TEER, or electrical resistance, goes up; permeability goes down. In other words: leakiness drops, protection returns. Histology tip: junctions look sharper, nuclei line up, and cilia or microvilli re-emerge. Local rules to tissue metrics: junction reorg + cytoskeletal crawl + integrin–ECM grips → temporary high permeability, then restored low permeability and proper excitability/resistance at the surface. Case two: a strained tendon on rehab. – Early on, fibroblasts (tenocytes) wake up. They lay down lots of type III collagen, kind of a quick patch. It’s messy and more elastic. In slides, expect edema, many spindle-shaped cells, new little vessels, and wavy, disorganized fibers. – With loading over weeks, cells sense tension through integrins, reorganize their cytoskeleton, and swap in type I collagen. Fibers realign parallel to pull, cross-links increase. Histology shifts to fewer cells, fewer vessels, thicker, straighter bundles with clearer crimp. – Tissue metrics: strength climbs; failure risk drops. Compliance decreases—the tendon gets stiffer in the good way for force transfer. Not instant: weeks to months. Early tissue is weaker and more compliant; later tissue is stronger and less compliant. Local rules to tissue metrics: ECM deposition + fiber alignment + cytoskeletal tension sensing → rising tensile strength and tuned stiffness. Big picture: cells tweak junctions, the cytoskeleton, and the matrix. That micro-logic drives macro-behavior—permeability in epithelia, and strength/compliance in tendon. On your next slide review, spot the loosen–move–lock sequence in epithelia, and the disorganized-to-aligned collagen story in tendon. You’ve got this—tiny cell choices, big tissue wins!

Course

Foundations of Human Biology

8 units36 lessons

Topics

BiologyHuman AnatomyHuman PhysiologyCell BiologyMolecular BiologyGenetics

About this course

This course builds a coherent framework for understanding human biology from molecules to organ systems. It develops scientific thinking and data literacy while covering cell structure and function, biomolecules, membranes and transport, enzymes and metabolism, and energy flow with ATP. It links tissues to organ-level physiology, emphasizing homeostasis, feedback, and core mechanisms in circulatory, respiratory, digestive, renal, nervous, endocrine, immune, musculoskeletal, integumentary, and reproductive systems, including gas exchange and circulation fundamentals. Foundations in Mendelian and molecular genetics, gene regulation and variation, and evolutionary principles are integrated with quantitative skills for rates, proportions, and graph interpretation.