Name: tissue injury and wound healing
Uploaded: 2023-06-23T15:38:47.000Z
Duration: 1 min 28 s
Channel: JoVE

Wound repair occurs in four phases in animal tissue.
The first phase, hemostasis, starts immediately after an injury. Damaged blood vessels constrict, leading to reduced blood flow and hypoxia at the injury site. This attracts platelets and activates the clotting mechanism to help seal the wound. A blood clot further helps control bleeding and prevent infection.
The damaged cells at the wound site then signal immune cells to initiate the second phase, inflammation. Neutrophils and macrophages are recruited through the bloodstream to kill bacteria and remove debris. These cells release growth factors to begin the third phase, proliferation, and facilitate fibroblast migration from the surrounding tissue.
Fibroblasts divide, secrete collagen-rich extracellular matrix, and promote the reestablishment of the blood vessel network, leading to the formation of granulation tissue.
In the final phase of repair, remodeling, the wound contracts and most fibroblasts die. Then, the collagen fibers are rearranged into an organized and rigid structure, providing strength to the newly formed tissues.
The granulation tissue is gradually transformed into scar tissue that mimics normal tissue structure.

tissue injury: inflammation and repair

Tissue Injury: Inflammation and Repair

Following injury, the integrity of the injured tissues must be reestablished. For example, in skin tissue, wound repair involves coordination among resident skin cells, blood mononuclear cells, extracellular matrix, growth factors, and cytokines to complete the healing cascade.
Formation of Blood Clot 
In case of deep injuries, trauma to blood vessels results in blood loss. In the meantime, phospholipids released from the ruptured endothelial cellular membrane are converted into arachidonic acid and metabolites like thromboxane A2 and prostaglandin 2&#945;. These factors promote vasoconstriction at the site of injury, generally lasting up to 5-10 minutes and resulting in brief hypoxia. Due to a lack of oxygen, cells and tissues surrounding the injury site shift ATP production via the anaerobic glycolysis pathway. The lactic acid produced at the end of anaerobic glycolysis reduces the pH in the adjoining tissues and cells. Blood vessel trauma and reduced pH significantly induce platelet activation, adhesion, and aggregation. Next, the blood clot is formed, sealing the injury site from external infection and establishing the temporary matrix composed of thrombin, collagen, fibronectin, and platelets. This matrix induces several cytokines and growth factors that are needed during the repair process.
Chemotaxis and Activation
Once the clot is formed, damaged cells at the injury site send a distress signal to immune cells in the body. This is followed by the recruitment of the neutrophils at the injury site. Prostaglandins E2 have a central role in the inflammatory response. They promote vasodilation and increase the blood flow to allow the movement of neutrophils. The neutrophils inhibit the growth of bacteria by releasing proteolytic enzymes. Even macrophages play a critical role in all the phases of wound repair, such as secretion of cytokines and growth factors like interleukin and tumor necrosis growth factor. They also promote fibroblast proliferation and angiogenesis at the wound site.
Extracellular Matrix Reorganization
Collagen is the major fibrous protein in the extracellular matrix (ECM) that imparts tensile strength and regulates cell adhesion to the tissues. The damage caused to ECM is restored in the remodeling phase of the wound repair. In the granulation tissue, ECM produced by fibroblasts is composed of type III collagen &#8212; a weaker structural protein. To cope with higher collagen demand, fibroblasts prefer to secrete type III collagen, and the rate of collagen production is highest. It is in the remodeling phase of the healing cascade that the matrix metalloproteinases (released by fibroblasts) remodel type III collagen into type I collagen that is stronger and has higher tensile strength. The arrangement of type I collagen into parallel bundles helps wound contraction and provides rigidity to newly formed tissues.

Following injury, the integrity of the injured tissues must be reestablished. For example, in skin tissue, wound repair involves coordination among ...

Education

JoVE Core

Anatomy and Physiology

Unit 1

Tissues of the Human Body

KEY TERMS AND CONCEPTS

tissue injury and wound healing

Tissue injury triggers inflammation and repair. After tissue is damaged, the body begins a wound healing response that helps protect the area and restore function.

Inflammation is the first stage. It helps limit further damage and prepares the tissue for repair. During this time, the body clears injured material and starts the healing process.

Repair follows as new tissue forms. In some cases, the damaged area can be replaced by tissue that restores normal structure and function. In other cases, repair leads to scar tissue when full replacement is not possible.

Tissue Injury and Wound Healing

tissues

Four Tissue Types in the Human Body

Tissues are groups of cells with a common embryonic origin. Under a microscope, the cells in a tissue often look similar and are arranged in an orderly pattern. This structure helps the tissue carry out a specific function. In the human body, many different cells are organized into four broad tissue categories: epithelial, connective, muscle, and nervous. These tissue types each have a distinct role in keeping the body working properly. They also show how cells can be specialized for different...

epithelial tissues and their functions

Epithelial Barriers, Secretion, and Senses

Epithelial tissue forms the body’s protective barrier and covers both internal and external surfaces. It is found on the skin, in the airways, the digestive tract, the urinary system, and the reproductive system. In hollow organs and body cavities that do not open to the outside, such as blood vessels and serous membranes, the lining is called endothelium. This tissue acts as the body’s first line of defense against physical, chemical, and biological wear and tear. It also works as a...

cell adhesion molecules - types and functions

cell-adhesion-molecules-types-and-functions

Cell Adhesion Molecules in Cell Interactions

Cell adhesion molecules help cells attach to one another and to the surrounding environment. These proteins are an important part of cell-cell interactions and cell behavior. Several major types of cell adhesion molecules are involved in these connections. They differ in structure and in the way they help cells bind, but they all support adhesion between cells or between cells and other surfaces. Cell adhesion molecules also play a key role in how tissues stay organized. By helping cells stay...

overview of cell-cell junctions

Cell-Cell Junctions in Animal Cells

Cell-cell junctions help animal cells connect, communicate, and stay organized in tissues. These junctions are specialized structures that hold cells together and support tissue function. Some junctions provide strong attachment between neighboring cells. Others create channels that let cells share small molecules and signals. These links help tissues act as coordinated units instead of separate cells. Cell-cell junctions are important in many body tissues. They help maintain structure,...

classification of epithelial tissues: overview

classification-of-epithelial-tissues-overview

Epithelial Tissue Shapes and Layers

Epithelial tissue is identified by cell shape and by the number of cell layers. The main cell shapes are squamous, cuboidal, and columnar. Squamous cells are flattened and thin. Cuboidal cells are square-like, and columnar cells are rectangular and taller than they are wide. The nucleus shape also helps with identification. Squamous cells have flattened, disc-shaped nuclei. Cuboidal cells have spherical nuclei. Columnar cells have elongated nuclei. Epithelial tissue is also grouped as simple...

classification of epithelial tissues: simple epithelium

classification-of-epithelial-tissues-simple-epithelium

Simple Epithelium: Types and Cell Shapes

Simple epithelium is a single layer of cells that lines body cavities and blood vessels. The shape of each cell matches the job of the tissue. In the body, this means flat, box-like, and tall cells each help in different ways. Simple squamous epithelium is made of thin, scale-like cells with flat, elliptical nuclei. Because these cells are so thin, they are found where chemicals must pass quickly. This tissue lines capillaries and blood and lymph vessels as endothelium, where nutrients are...

classification of epithelial tissues: stratified epithelium

classification-of-epithelial-tissues-stratified-epithelium

Stratified Epithelium Types and Locations

Stratified epithelium is made of several stacked layers of cells. These layers add durability and help the tissue handle constant physical and chemical stress. The tissue is named by the shape of the most apical, or top, cell layer. Stratified squamous epithelium is the most common type in the human body. Its apical cells are squamous, while the basal layer contains cuboidal or columnar cells. Basal cells divide to make new daughter cells. As these new cells move upward, they become flatter...

classification of epithelial tissues: glandular epithelium

classification-of-epithelial-tissues-glandular-epithelium

Glandular Epithelium: Secretory Cell Types

Glandular epithelium is epithelial tissue made of cells that are modified to make and release chemical substances. In high school biology, it is often studied by how many secretory cells it contains and how it sends out its products. Unicellular glands contain single secretory cells scattered within an epithelial layer. Multicellular glands have a hollow tubular duct connected to a group of secretory cells that sit in deeper pockets. These multicellular glands begin during early development...

exocrine glands: unicellular and multicellular glands

exocrine-glands-unicellular-and-multicellular-glands

Exocrine Gland Types and Duct Patterns

Exocrine glands are classified by the number of cells and by duct structure. Unicellular glands are single scattered cells, such as goblet cells in the mucous membranes of the small and large intestines. Multicellular exocrine glands form as secretory sheets, like the internal lining of the abdomen or chest, and they release their secretions directly into the lumen of these organs. Some multicellular glands also have deep secretory units and a hollow duct. The secretory units make the product,...

exocrine glands: methods of secretion

Exocrine Glands and Their Secretion Types

Exocrine glands release their products through ducts. Their secretion pattern helps group them into three types: merocrine, apocrine, and holocrine. These types differ in how the gland cell releases its material. Merocrine secretion is the most common type. In this process, the secretory product is packed into vesicles and moved to the apical surface of the cell. The contents are then released by exocytosis. Mucous, a watery secretion rich in the glycoprotein mucin, is one example. The eccrine...

exocrine glands: types of secretions

Exocrine Gland Secretions and Examples

Exocrine glands produce glandular products and release them outside the body or into a duct. These glands are grouped as serous, mucous, or mixed based on the kind of secretion they make. The three categories help show how gland structure relates to function. Serous glands make watery secretions that are rich in digestive enzymes and proteins. Their cells usually have centrally located nuclei and eosinophilic secretory granules in the cytoplasm, which means the granules stain strongly with...

introduction to connective tissues

Connective Tissue Structure and Disorders

Connective tissue is one of the four main tissue types in the human body. It is found throughout the body and helps connect and support different tissues. Its cells sit inside an extracellular matrix, or ECM, which includes a ground substance and protein fibers. The ECM gives connective tissue its different forms and strengths. The ground substance can be watery, jelly-like, or even mineralized and hard. The main protein fibers are collagen fibers, elastic fibers, and reticular fibers.

functions of connective tissues

How Connective Tissues Support the Body

Connective tissues support, connect, and protect the body. They also act as packing material between tissues in many organs. Different connective tissues do these jobs in different ways. Areolar tissue is a connective tissue prototype. It commonly cements different tissue types together in diverse body organs. Adipose tissue cushions internal organs and helps insulate the body from heat loss. Hard connective tissues include bones and cartilage. These tissues provide structure and support.

classification of connective tissues

Connective Tissue Types and Functions

Connective tissues support, connect, and protect body structures. They are grouped into proper, supporting, and fluid connective tissues. Each group has its own cell types, fibers, and matrix features that help it do a specific job. Connective tissue proper is the most abundant type. It mainly joins different tissues in the body. This group is further divided into loose and dense connective tissue based on the cell types, ground substance, viscosity, and fiber types in the extracellular...

embryonic connective tissues

Embryonic Support Tissues in Development

Embryonic connective tissues help shape the body during early development. The main types are mesenchyme and mucoid connective tissue. Both are temporary tissues that appear before birth and help build later structures. Mesenchyme is the first connective tissue to appear in the developing embryo. It is made of loosely arranged multipotent mesenchymal cells and reticular fibers in the extracellular matrix. This loose structure lets cells move easily, which is important for germ layer...

overview of connective tissues proper

Loose and Dense Connective Tissue Types

Connective tissue proper includes the mature connective tissues in the body, except bone, cartilage, blood, and lymph. It is divided into two main subclasses: loose connective tissue and dense connective tissue. These groups are classified by how their protein fibers are arranged and by the amount of ground substance, which is the material that fills the space between cells. Loose connective tissues contain a meshwork of thin collagen and elastin fibers. This arrangement gives support, tensile...

extracellular matrix

Extracellular Matrix in Connective Tissue

The extracellular matrix (ECM) gives connective tissue its support, shape, and signals. Unlike epithelial tissue, where cells are tightly packed with little or no space between them, connective tissue cells are spread out in a matrix. That matrix fills the space around the cells and helps the tissue work as a unit. The ECM contains fibrous proteins such as collagen, elastin, and fibronectin. It also includes a ground substance made of interstitial fluid, cell adhesion proteins, and...

connective tissue fibers and ground substance

connective-tissue-fibers-and-ground-substance

How Connective Tissue Gets Its Strength

Connective tissue gets its strength and support from cells, ground substance, and protein fibers. Unlike epithelial tissue, which has tightly packed cells, connective tissue cells are spread out in a matrix. The matrix is the extra material outside the cells, and it is made by the connective tissue cells themselves. It is a major part of how this tissue works. The main part of the matrix is ground substance, which is often a fluid but can also be hard and mineralized, as in bone. Connective...

loose connective tissue

Loose Connective Tissue Types and Functions

Loose connective tissue is found between many organs. It helps bind tissues together and absorb shock. It also lets water, salts, and nutrients diffuse into cells that are embedded in it or in nearby tissues. Adipose tissue is a type of loose connective tissue made mainly of fat storage cells called adipocytes. It has very little extracellular matrix, and its many capillaries help move lipid molecules quickly. White adipose tissue is the most common type in adults. It can look yellow because...

dense connective tissue

Dense Connective Tissue Fibers and Support

Dense connective tissue has more collagen fibers than loose connective tissue. That extra collagen makes it more resistant to stretching. It is usually grouped into two main types: dense regular connective tissue and dense irregular connective tissue. Dense regular connective tissue has fibers arranged in parallel. This pattern gives the tissue high tensile strength, or resistance to pulling, in the direction of the fibers. Ligaments and tendons are made of dense regular connective tissue, and...

layers of connective tissue proper

Fascia and Body Movement Support

Fascia is a thin, fibrous connective tissue that supports many parts of the body. It surrounds skeletal muscles, bones, blood vessels, and organs. Because it forms a continuous layer, it helps define and protect these structures. There are three main types of fascia: superficial fascia, deep fascia, and subserous fascia. Each type lies at a different depth in the body. Together, they make up a fascial system that links tissues across the body. Fascia reduces friction so muscles, joints, and...

bone as supporting connective tissue

Bone Matrix and Cell Structure

Bone tissue is the hard connective tissue that forms the internal skeleton of vertebrate animals. It gives the body support and shape. Bone, also called osseous tissue, contains a matrix made of both organic and inorganic material. The organic matrix includes collagen and elastic fibers. These materials help give bone strength and flexibility. The inorganic matrix is made mostly of mineral salts, especially calcium salts. These salts make bone hard. If the organic material is too low, bones...

tissue membranes

Tissue Membranes and Their Functions

Tissue membranes are thin layers that cover the body, protect organs, line passageways that open to the outside, and line movable joint cavities. They fall into two broad groups: connective tissue membranes and epithelial membranes. Connective tissue membranes are made only of connective tissue. They wrap around organs such as the kidneys and also line movable joints. A synovial membrane is a connective tissue membrane found in freely movable joints like the shoulder, elbow, and knee. Inside...

fluid connective tissues: blood and lymph

Blood and Lymph: Transport and Defense

Blood and lymph are fluid connective tissues that help the body transport materials and defend against infection. They contain formed elements, which are cells suspended in a liquid extracellular matrix called plasma. These formed elements come from hematopoietic stem cells in the bone marrow. Blood moves through arteries, capillaries, and veins. Its plasma is made mainly of proteins, solutes, and water. The rest of the blood includes erythrocytes, or red blood cells, leukocytes, or white...

Tissue injury triggers inflammation and repair. After tissue is damaged, the body begins a wound healing response that helps protect the area and restore function. Inflammation is the first stage. It helps limit further damage and prepares the tissue for repair. During this time, the body clears injured material and starts the healing process. Repair follows as new tissue forms. In some cases, the damaged area can be replaced by tissue that restores normal structure and function. In other...

the effect of aging on tissues

How Aging Changes Body Tissues

Aging changes body tissues and lowers how well many body systems work. Some of the clearest changes are visible on the outside. Skin can become dry, thinner, and less elastic, which leads to wrinkles. The skin on the face may also look looser because connective tissue has less elastic and collagen fibers. Aging also affects hair, senses, bones, and joints. Melanin production in hair follicles decreases with age, so hair can turn gray. Sight and hearing may decline, and glasses or hearing aids...

key terms and concepts

Learn how tissue injury leads to inflammation and repair, including the wound healing response, tissue replacement, and scar formation.

Tissue Injury and Wound Healing | JoVE K12

anatomy and physiology

JoVE Core Anatomy and Physiology showcases the anatomical and physiological details of the human body in comprehensive, clear, and engaging video animations. This collection of lessons focuses on the structures, components, functions, and requirements of the human body. It is complemented by scientist-in-action videos that demonstrate the application of this knowledge in real-world medical and research settings.

Tissue Injury and Wound Healing

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