Module 4: The Tissue Level of Organization

Lesson 6: Tissue Injury and Aging

Tổn Thương Mô Và Lão Hóa

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Mỗi bài học (lesson) bao gồm 4 phần chính: Thuật ngữ, Luyện Đọc, Luyện Nghe, và Bàn Luận.
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Dưới đây là danh sách những thuật ngữ Y khoa của module The Tissue Level of Organization.
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Medical Terminology: The Tissue Level of Organization

adipocytes
lipid storage cells
adipose tissue
specialized areolar tissue rich in stored fat
anchoring junction
mechanically attaches adjacent cells to each other or to the basement membrane
apical
that part of a cell or tissue which, in general, faces an open space
apocrine secretion
release of a substance along with the apical portion of the cell
apoptosis
programmed cell death
areolar tissue
(also, loose connective tissue) a type of connective tissue proper that shows little specialization with cells dispersed in the matrix
astrocyte
star-shaped cell in the central nervous system that regulates ions and uptake and/or breakdown of some neurotransmitters and contributes to the formation of the blood-brain barrier
atrophy
loss of mass and function
basal lamina
thin extracellular layer that lies underneath epithelial cells and separates them from other tissues
basement membrane
in epithelial tissue, a thin layer of fibrous material that anchors the epithelial tissue to the underlying connective tissue; made up of the basal lamina and reticular lamina
cardiac muscle
heart muscle, under involuntary control, composed of striated cells that attach to form fibers, each cell contains a single nucleus, contracts autonomously
cell junction
point of cell-to-cell contact that connects one cell to another in a tissue
chondrocytes
cells of the cartilage
clotting
also called coagulation; complex process by which blood components form a plug to stop bleeding
collagen fiber
flexible fibrous proteins that give connective tissue tensile strength
connective tissue
type of tissue that serves to hold in place, connect, and integrate the body’s organs and systems
connective tissue membrane
connective tissue that encapsulates organs and lines movable joints
connective tissue proper
connective tissue containing a viscous matrix, fibers, and cells.
cutaneous membrane
skin; epithelial tissue made up of a stratified squamous epithelial cells that cover the outside of the body
dense connective tissue
connective tissue proper that contains many fibers that provide both elasticity and protection
ectoderm
outermost embryonic germ layer from which the epidermis and the nervous tissue derive
elastic cartilage
type of cartilage, with elastin as the major protein, characterized by rigid support as well as elasticity
elastic fiber
fibrous protein within connective tissue that contains a high percentage of the protein elastin that allows the fibers to stretch and return to original size
endocrine gland
groups of cells that release chemical signals into the intercellular fluid to be picked up and transported to their target organs by blood
endoderm
innermost embryonic germ layer from which most of the digestive system and lower respiratory system derive
endothelium
tissue that lines vessels of the lymphatic and cardiovascular system, made up of a simple squamous epithelium
epithelial membrane
epithelium attached to a layer of connective tissue
epithelial tissue
type of tissue that serves primarily as a covering or lining of body parts, protecting the body; it also functions in absorption, transport, and secretion
exocrine gland
group of epithelial cells that secrete substances through ducts that open to the skin or to internal body surfaces that lead to the exterior of the body
fibroblast
most abundant cell type in connective tissue, secretes protein fibers and matrix into the extracellular space
fibrocartilage
tough form of cartilage, made of thick bundles of collagen fibers embedded in chondroitin sulfate ground substance
fibrocyte
less active form of fibroblast
fluid connective tissue
specialized cells that circulate in a watery fluid containing salts, nutrients, and dissolved proteins
gap junction
allows cytoplasmic communications to occur between cells
goblet cell
unicellular gland found in columnar epithelium that secretes mucous
ground substance
fluid or semi-fluid portion of the matrix
histamine
chemical compound released by mast cells in response to injury that causes vasodilation and endothelium permeability
histology
microscopic study of tissue architecture, organization, and function
holocrine secretion
release of a substance caused by the rupture of a gland cell, which becomes part of the secretion
hyaline cartilage
most common type of cartilage, smooth and made of short collagen fibers embedded in a chondroitin sulfate ground substance
inflammation
response of tissue to injury
lacunae
(singular = lacuna) small spaces in bone or cartilage tissue that cells occupy
lamina propria
areolar connective tissue underlying a mucous membrane
loose connective tissue
(also, areolar tissue) type of connective tissue proper that shows little specialization with cells dispersed in the matrix
matrix
extracellular material which is produced by the cells embedded in it, containing ground substance and fibers
merocrine secretion
release of a substance from a gland via exocytosis
mesenchymal cell
adult stem cell from which most connective tissue cells are derived
mesenchyme
embryonic tissue from which connective tissue cells derive
mesoderm
middle embryonic germ layer from which connective tissue, muscle tissue, and some epithelial tissue derive
mesothelium
simple squamous epithelial tissue which covers the major body cavities and is the epithelial portion of serous membranes
mucous connective tissue
specialized loose connective tissue present in the umbilical cord
mucous gland
group of cells that secrete mucous, a thick, slippery substance that keeps tissues moist and acts as a lubricant
mucous membrane
tissue membrane that is covered by protective mucous and lines tissue exposed to the outside environment
muscle tissue
type of tissue that is capable of contracting and generating tension in response to stimulation; produces movement.
myelin
layer of lipid inside some neuroglial cells that wraps around the axons of some neurons
myocyte
muscle cells
necrosis
accidental death of cells and tissues
nervous tissue
type of tissue that is capable of sending and receiving impulses through electrochemical signals.
neuroglia
supportive neural cells
neuron
excitable neural cell that transfer nerve impulses
oligodendrocyte
neuroglial cell that produces myelin in the brain
parenchyma
functional cells of a gland or organ, in contrast with the supportive or connective tissue of a gland or organ
primary union
condition of a wound where the wound edges are close enough to be brought together and fastened if necessary, allowing quicker and more thorough healing
pseudostratified columnar epithelium
tissue that consists of a single layer of irregularly shaped and sized cells that give the appearance of multiple layers; found in ducts of certain glands and the upper respiratory tract
reticular fiber
fine fibrous protein, made of collagen subunits, which cross-link to form supporting “nets” within connective tissue
reticular lamina
matrix containing collagen and elastin secreted by connective tissue; a component of the basement membrane
reticular tissue
type of loose connective tissue that provides a supportive framework to soft organs, such as lymphatic tissue, spleen, and the liver
Schwann cell
neuroglial cell that produces myelin in the peripheral nervous system
secondary union
wound healing facilitated by wound contraction
serous gland
group of cells within the serous membrane that secrete a lubricating substance onto the surface
serous membrane
type of tissue membrane that lines body cavities and lubricates them with serous fluid
simple columnar epithelium
tissue that consists of a single layer of column-like cells; promotes secretion and absorption in tissues and organs
simple cuboidal epithelium
tissue that consists of a single layer of cube-shaped cells; promotes secretion and absorption in ducts and tubules
simple squamous epithelium
tissue that consists of a single layer of flat scale-like cells; promotes diffusion and filtration across surface
skeletal muscle
usually attached to bone, under voluntary control, each cell is a fiber that is multinucleated and striated
smooth muscle
under involuntary control, moves internal organs, cells contain a single nucleus, are spindle-shaped, and do not appear striated; each cell is a fiber
stratified columnar epithelium
tissue that consists of two or more layers of column-like cells, contains glands and is found in some ducts
stratified cuboidal epithelium
tissue that consists of two or more layers of cube-shaped cells, found in some ducts
stratified squamous epithelium
tissue that consists of multiple layers of cells with the most apical being flat scale-like cells; protects surfaces from abrasion
striation
alignment of parallel actin and myosin filaments which form a banded pattern
supportive connective tissue
type of connective tissue that provides strength to the body and protects soft tissue
synovial membrane
connective tissue membrane that lines the cavities of freely movable joints, producing synovial fluid for lubrication
tight junction
forms an impermeable barrier between cells
tissue
group of cells that are similar in form and perform related functions
tissue membrane
thin layer or sheet of cells that covers the outside of the body, organs, and internal cavities
totipotent
embryonic cells that have the ability to differentiate into any type of cell and organ in the body
transitional epithelium
form of stratified epithelium found in the urinary tract, characterized by an apical layer of cells that change shape in response to the presence of urine
vasodilation
widening of blood vessels
wound contraction
process whereby the borders of a wound are physically drawn together
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Tissues of all types are vulnerable to injury and, inevitably, aging. In the former case, understanding how tissues respond to damage can guide strategies to aid repair. In the latter case, understanding the impact of aging can help in the search for ways to diminish its effects.
Inflammation is the standard, initial response of the body to injury. Whether biological, chemical, physical, or radiation burns, all injuries lead to the same sequence of physiological events. Inflammation limits the extent of injury, partially or fully eliminates the cause of injury, and initiates repair and regeneration of damaged tissue. Necrosis, or accidental cell death, causes inflammation. Apoptosis is programmed cell death, a normal step-by-step process that destroys cells no longer needed by the body. By mechanisms still under investigation, apoptosis does not initiate the inflammatory response. Acute inflammation resolves over time by the healing of tissue. If inflammation persists, it becomes chronic and leads to diseased conditions. Arthritis and tuberculosis are examples of chronic inflammation. The suffix “-itis” denotes inflammation of a specific organ or type, for example, peritonitis is the inflammation of the peritoneum, and meningitis refers to the inflammation of the meninges, the tough membranes that surround the central nervous system The four cardinal signs of inflammation—redness, swelling, pain, and local heat—were first recorded in antiquity. Cornelius Celsus is credited with documenting these signs during the days of the Roman Empire, as early as the first century AD. A fifth sign, loss of function, may also accompany inflammation.

Upon tissue injury, damaged cells release inflammatory chemical signals that evoke local vasodilation, the widening of the blood vessels. Increased blood flow results in apparent redness and heat. In response to injury, mast cells present in tissue degranulate, releasing the potent vasodilator histamine. Increased blood flow and inflammatory mediators recruit white blood cells to the site of inflammation. The endothelium lining the local blood vessel becomes “leaky” under the influence of histamine and other inflammatory mediators allowing neutrophils, macrophages, and fluid to move from the blood into the interstitial tissue spaces. The excess liquid in tissue causes swelling, more properly called edema. The swollen tissues squeezing pain receptors cause the sensation of pain. Prostaglandins released from injured cells also activate pain neurons. Non-steroidal anti-inflammatory drugs (NSAIDs) reduce pain because they inhibit the synthesis of prostaglandins. High levels of NSAIDs reduce inflammation. Antihistamines decrease allergies by blocking histamine receptors and as a result the histamine response.

After containment of an injury, the tissue repair phase starts with removal of toxins and waste products. Clotting (coagulation) reduces blood loss from damaged blood vessels and forms a network of fibrin proteins that trap blood cells and bind the edges of the wound together. A scab forms when the clot dries, reducing the risk of infection. Sometimes a mixture of dead leukocytes and fluid called pus accumulates in the wound. As healing progresses, fibroblasts from the surrounding connective tissues replace the collagen and extracellular material lost by the injury. Angiogenesis, the growth of new blood vessels, results in vascularization of the new tissue known as granulation tissue. The clot retracts pulling the edges of the wound together, and it slowly dissolves as the tissue is repaired. When a large amount of granulation tissue forms and capillaries disappear, a pale scar is often visible in the healed area. A primary union describes the healing of a wound where the edges are close together. When there is a gaping wound, it takes longer to refill the area with cells and collagen. The process called secondary union occurs as the edges of the wound are pulled together by what is called wound contraction. When a wound is more than one quarter of an inch deep, sutures (stitches) are recommended to promote a primary union and avoid the formation of a disfiguring scar. Regeneration is the addition of new cells of the same type as the ones that were injured (Figure 1).
According to poet Ralph Waldo Emerson, “The surest poison is time.” In fact, biology confirms that many functions of the body decline with age. All the cells, tissues, and organs are affected by senescence, with noticeable variability between individuals owing to different genetic makeup and lifestyles. The outward signs of aging are easily recognizable. The skin and other tissues become thinner and drier, reducing their elasticity, contributing to wrinkles and high blood pressure. Hair turns gray because follicles produce less melanin, the brown pigment of hair and the iris of the eye. The face looks flabby because elastic and collagen fibers decrease in connective tissue and muscle tone is lost. Glasses and hearing aids may become parts of life as the senses slowly deteriorate, all due to reduced elasticity. Overall height decreases as the bones lose calcium and other minerals. With age, fluid decreases in the fibrous cartilage disks intercalated between the vertebrae in the spine. Joints lose cartilage and stiffen. Many tissues, including those in muscles, lose mass through a process called atrophy. Lumps and rigidity become more widespread. As a consequence, the passageways, blood vessels, and airways become more rigid. The brain and spinal cord lose mass. Nerves do not transmit impulses with the same speed and frequency as in the past. Some loss of thought clarity and memory can accompany aging. More severe problems are not necessarily associated with the aging process and may be symptoms of underlying illness.

As exterior signs of aging increase, so do the interior signs, which are not as noticeable. The incidence of heart diseases, respiratory syndromes, and type 2 diabetes increases with age, though these are not necessarily age-dependent effects. Wound healing is slower in the elderly, accompanied by a higher frequency of infection as the capacity of the immune system to fend off pathogen declines.

Aging is also apparent at the cellular level because all cells experience changes with aging. Telomeres, regions of the chromosomes necessary for cell division, shorten each time cells divide. As they do, cells are less able to divide and regenerate. Because of alterations in cell membranes, transport of oxygen and nutrients into the cell and removal of carbon dioxide and waste products from the cell are not as efficient in the elderly. Cells may begin to function abnormally, which may lead to diseases associated with aging, including arthritis, memory issues, and some cancers.

The progressive impact of aging on the body varies considerably among individuals, but studies indicate, however, that exercise and healthy lifestyle choices can slow down the deterioration of the body that comes with old age.

Cancer treatments vary depending on the disease’s type and stage. Traditional approaches, including surgery, radiation, chemotherapy, and hormonal therapy, aim to remove or kill rapidly dividing cancer cells, but these strategies have their limitations. Depending on a tumor’s location, for example, cancer surgeons may be unable to remove it. Radiation and chemotherapy are difficult, and it is often impossible to target only the cancer cells. The treatments inevitably destroy healthy tissue as well. To address this, researchers are working on pharmaceuticals that can target specific proteins implicated in cancer-associated molecular pathways.

OpenStax. (2022). Anatomy and Physiology 2e. Rice University. Retrieved June 15, 2023. ISBN-13: 978-1-711494-06-7 (Hardcover) ISBN-13: 978-1-711494-05-0 (Paperback) ISBN-13: 978-1-951693-42-8 (Digital). License: Attribution 4.0 International (CC BY 4.0). Access for free at openstax.org.

During wound repair, collagen fibers are laid down randomly by fibroblasts that move into repair the area.

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Script:
  1. Inflammation is the classic response of the body to injury and follows a common sequence of events.
  2. The area is red, feels warm to the touch, swells, and is painful.
  3. Injured cells, mast cells, and resident macrophages release chemical signals that cause vasodilation and fluid leakage in the surrounding tissue.
  4. The repair phase includes blood clotting, followed by regeneration of tissue as fibroblasts deposit collagen.
  5. Some tissues regenerate more readily than others.
  6. Epithelial and connective tissues replace damaged or dead cells from a supply of adult stem cells.
  7. Muscle and nervous tissues undergo either slow regeneration or do not repair at all.
  8. Age affects all the tissues and organs of the body.
  9. Damaged cells do not regenerate as rapidly as in younger people.
  10. Perception of sensation and effectiveness of response are lost in the nervous system.
  11. Muscles atrophy, and bones lose mass and become brittle.
  12. Collagen decreases in some connective tissue, and joints stiffen.
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