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Related Concept Videos

The Effect of Aging on Tissues01:19

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Several body functions deteriorate with age. The external signs of aging are easily identifiable. For example, the skin becomes dry, less elastic, and thins out, forming wrinkles. The skin of the face begins to appear looser due to a decrease in the levels of elastic and collagen fibers in the connective tissue. Additionally, melanin production in the hair follicle decreases with age, resulting in gray hair. Moreover, the senses of sight and hearing decline, so glasses and hearing aids may...
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Layers of the Epidermis01:21

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The epidermis, the outermost layer of the skin, is composed of several distinct layers. From deep to superficial, the layers of the epidermis are as follows:
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Stratum basale, also known as the stratum germinativum, is the deepest layer of the epidermis. It is composed of a single layer of actively dividing cells called basal cells or basal keratinocytes. These cells constantly undergo cell division to replenish the upper layers of the epidermis. Additionally, melanocytes, which...
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Aging01:26

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Aging is a complex biological phenomenon influenced by various processes that affect cellular and systemic functions. Several prominent theories attempt to explain its mechanisms, highlighting cellular limitations, oxidative damage, and hormonal changes as central factors in aging.
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Cells of the Epidermis01:24

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The epidermis is made of four or five layers of epithelial cells, depending on its location in the body. From deep to superficial, these layers are the stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.
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The papillary and reticular dermis are the two layers of the dermis. They are made of connective tissue with fibers of collagen extending from one to the other, making the border between the two somewhat indistinct. The dermal papillae extending into the epidermis belong to the papillary layer, whereas the dense collagen fiber bundles below belong to the reticular layer.
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The skin is divided into epidermis, dermis, and hypodermis, the skin's outermost, middle, and inner layers. The human epidermal layer regularly undergoes renewal, where old, dead cells are replaced by new cells. Epidermal stem cells or EpiSCs divide and differentiate to restore the lost cells. For the renewal process, some EpiSCs continuously self-renew. In contrast, few others differentiate into transit-amplifying cells, which later form prickle or spinous cells, followed by granular...
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The Four Layers of Aging.

Ran Zhang1, Hou-Zao Chen1, De-Pei Liu1

  • 1State Key Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100005, P.R. China.

Cell Systems
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Summary

Aging is a multi-layered process, not just isolated hallmarks. Understanding these four biological layers and their interactions reveals how aging phenotypes and disease susceptibility develop.

Keywords:
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Area of Science:

  • Gerontology
  • Molecular Biology
  • Systems Biology

Background:

  • Aging is traditionally viewed through discrete hallmarks.
  • A comprehensive understanding of aging mechanisms remains incomplete.
  • The interplay between different biological scales in aging is not fully elucidated.

Purpose of the Study:

  • To propose a novel, multi-layered framework for understanding aging.
  • To reframe aging research beyond discrete hallmarks.
  • To elucidate the biological scales and interconnections that define the aging process.

Main Methods:

  • Conceptual framework development.
  • Integration of existing aging research findings.
  • Analysis of biological scales from molecular to organismal levels.

Main Results:

  • Aging operates across four distinct, interconnected biological layers.
  • Malfunctions within and between these layers contribute to aging.
  • This layered model explains the aged phenotype and disease susceptibility.

Conclusions:

  • A multi-layered perspective offers a more holistic understanding of aging.
  • Interactions between biological scales are critical drivers of aging.
  • This framework can guide future research into aging and age-related diseases.