Mitosis

The human body develops, replaces old cells with new cells, and repairs itself, with the help of cells that constantly multiply by dividing. The process begins in the cell nucleus. Identical copies of DNA molecules organize into chromatid pairs within the chromosome structure. These pairs are connected to each other at the chromosome’s centromere. In […]

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platelets

Platelets

Cell fragments called platelets, or thrombocytes, make up about 2 percent of blood. Platelets stop blood loss from damaged vessels. When a blood vessel tears, platelets at the site adhere to the wall of the vessel to close the tear. The shape of the platelets changes as they liberate the contents of their vesicles. This […]

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fagocites

Phagocytes

When bacteria or other pathogens are present in the body, certain white blood cells categorized as phagocytes consume the microorganisms to protect the body from infection. The process of consuming the pathogen begins when the phagocyte is attracted to chemicals from the pathogen, and through receptors, binds to it. The phagocyte ingests the microbe, encasing […]

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red blood cells

Red blood cells

The bloodstream delivers oxygen to cells and removes carbon dioxide waste through a process called internal respiration. In the lungs, oxygen is absorbed into the erythrocytes in the blood stream. These cells, commonly called red blood cells, contain gas-transporting molecules called hemoglobin. Oxygen binds to these molecules. The oxygenated blood then moves through the vasculature. […]

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Bone Repair

Bone repair

A fractured bone bleeds. Bone repair begins, as over a period of hours blood at the fracture site clots and forms a hematoma. The healing begins as osteoclasts in the area remove dead bone tissue, while fibroblasts penetrate the area and build a fibrocartilaginous callus that bridges the broken bone. Over many weeks osteoblasts transform […]

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sound production

Sound production

Phonation is the production of sound by structures in the upper respiratory tract. During exhalation, air passes from the lungs through the larynx. Muscles in the larynx can act to move the arytenoid cartilages that then move the cords. The cords are pushed together and air passes between them in such a way as to […]

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nurients absortion

Nutrient absorption

Mechanical and chemical digestion in the stomach results in chyme. Peristaltic waves propel chyme through the pyloric sphincter into the duodenum of the small intestine. Finger-like projections called villi line the interior wall of the small intestine. Most absorption of nutrients from ingested food occurs through these. In the small intestine, nutrients in the chyme […]

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