MT 30 (LEC): the largest cell in the human body

Summary of the Article

  • Cells in the Human Body

    • The body contains over 100 trillion cells.

    • Cells form tissues, tissues form organs, and organs make up organ systems.

    • Different functions lead to variations in cell shape and size.

  • Largest Cell: Female Ovum (Egg Cell)

    • Largest human cell, about 120 micrometers in diameter.

    • 20 times the size of a sperm cell and visible to the naked eye.

    • Reproductive cell in females; provides nutrients for embryo development.

    • Women are born with ~1 million eggs, but only 300,000 remain at puberty.

    • Typically, one egg is released per month during ovulation.

  • Smallest Cell: Male Sperm

    • Smallest human cell by volume.

    • Sperm head: ~4 micrometers long; tail: ~50 micrometers long.

    • A fertile man produces between 40 million and 1800 million sperm cells.

    • Survives only in warm environments and dies outside the body.

  • Smallest Blood Cell: Platelets (Thrombocytes)

    • Tiny disc-shaped fragments, 1-4 micrometers in diameter.

    • Only 20% the diameter of a red blood cell.

    • Play a crucial role in blood clotting and tissue repair.

  • Platelet Production & Function

    • Produced in the bone marrow from megakaryocytes.

    • Regulated by thrombopoietin (TPO) hormone.

    • Lifespan: 5-9 days.

    • Change shape when activated—extend filaments to form a clot at injury sites.

    • Contain proteins that help them stick to vessel walls and each other.

  • Platelet Disorders

    • Thrombocytopenia: Low platelet count, leading to excessive bleeding.

    • Thrombocythemia: Overproduction of platelets, causing blood clot risks.

  • Scavenger Blood Cell: Macrophages

    • A type of white blood cell (leukocyte).

    • Found in tissues like the liver, brain, intestines, and skin.

    • Engulf bacteria, remove dead cells, and stimulate the immune system.

  • Types of Macrophages (Granulocytes)

    • Neutrophils (50-70% of WBCs): First responders to infections.

    • Eosinophils (<5% of WBCs): Attack parasites and cancer cells.

    • Basophils (<1% of WBCs): Release histamine for allergic reactions.

  • Largest Blood Cell: Monocytes

    • Largest white blood cell (15-18 micrometers in diameter).

    • Engulf pathogens but are less effective at bacterial removal than neutrophils.

    • Produced in bone marrow, then mature into macrophages in tissues.

    • Lifespan: ~3 days.

  • Oxygen-Carrying Blood Cells: Red Blood Cells (Erythrocytes)

    • Most abundant blood cell (~5 million per microliter).

    • Contain hemoglobin, which binds and transports oxygen.

    • Biconcave shape increases surface area for gas exchange.

    • Lifespan: ~120 days.

  • Red Blood Cell Disorders

    • Anemia: Low RBC count leading to oxygen deficiency.

    • Symptoms: Pale skin, fatigue, rapid heart rate.

    • Iron Deficiency Anemia: Caused by inadequate iron intake or absorption.

  • Vitamin for Red Blood Cell Production: Vitamin B12

    • Essential for RBC formation.

    • Found in meat, dairy, eggs, and fortified cereals.

    • Deficiency can result from poor diet, alcohol use, or digestive issues.