Which Answer Choice Correctly Lists Components Found In The Extracellular Matrix Of Animals?

The Tissue Level of Organisation

Connective Tissue Supports and Protects

Learning Objectives

By the end of this section, you will exist able to:

• Identify and distinguish between the types of connective tissue: proper, supportive, and fluid
• Explain the functions of connective tissues

Equally may exist obvious from its proper noun, i of the major functions of connective tissue is to connect tissues and organs. Different epithelial tissue, which is equanimous of cells closely packed with picayune or no extracellular space in between, connective tissue cells are dispersed in a matrix. The matrix usually includes a large amount of extracellular textile produced by the connective tissue cells that are embedded inside it. The matrix plays a major role in the functioning of this tissue. The major component of the matrix is a basis substance oftentimes crisscrossed by protein fibers. This basis substance is usually a fluid, but information technology can also exist mineralized and solid, equally in bones. Connective tissues come in a vast variety of forms, yet they typically have in common iii characteristic components: cells, large amounts of amorphous basis substance, and protein fibers. The amount and construction of each component correlates with the office of the tissue, from the rigid ground substance in bones supporting the trunk to the inclusion of specialized cells; for example, a phagocytic cell that engulfs pathogens and also rids tissue of cellular droppings.

Functions of Connective Tissues

Connective tissues perform many functions in the body, just most chiefly, they support and connect other tissues; from the connective tissue sheath that surrounds musculus cells, to the tendons that attach muscles to basic, and to the skeleton that supports the positions of the body. Protection is some other major function of connective tissue, in the form of fibrous capsules and bones that protect frail organs and, of course, the skeletal system. Specialized cells in connective tissue defend the torso from microorganisms that enter the body. Ship of fluid, nutrients, waste, and chemical messengers is ensured by specialized fluid connective tissues, such as blood and lymph. Adipose cells store surplus energy in the form of fat and contribute to the thermal insulation of the body.

Embryonic Connective Tissue

All connective tissues derive from the mesodermal layer of the embryo (see (Figure)). The first connective tissue to develop in the embryo is mesenchyme, the stem cell line from which all connective tissues are later derived. Clusters of mesenchymal cells are scattered throughout adult tissue and supply the cells needed for replacement and repair after a connective tissue injury. A 2nd type of embryonic connective tissue forms in the umbilical cord, called mucous connective tissue or Wharton'due south jelly. This tissue is no longer present after birth, leaving just scattered mesenchymal cells throughout the body.

Classification of Connective Tissues

The three broad categories of connective tissue are classified according to the characteristics of their ground substance and the types of fibers found inside the matrix ((Figure)). Connective tissue proper includes loose connective tissue and dense connective tissue. Both tissues have a multifariousness of prison cell types and protein fibers suspended in a viscous ground substance. Dense connective tissue is reinforced by bundles of fibers that provide tensile strength, elasticity, and protection. In loose connective tissue, the fibers are loosely organized, leaving large spaces in between. Supportive connective tissue—os and cartilage—provide structure and strength to the trunk and protect soft tissues. A few distinct cell types and densely packed fibers in a matrix narrate these tissues. In bone, the matrix is rigid and described as calcified because of the deposited calcium salts. In fluid connective tissue, in other words, lymph and blood, diverse specialized cells broadcast in a watery fluid containing salts, nutrients, and dissolved proteins.

Connective Tissue Examples
Connective tissue proper	Supportive connective tissue	Fluid connective tissue
Loose connective tissue Areolar Adipose Reticular	Cartilage Hyaline Fibrocartilage Elastic	Blood
Dense connective tissue Regular elastic Irregular rubberband	Basic Compact os Cancellous bone	Lymph

Connective Tissue Proper

Fibroblasts are present in all connective tissue proper ((Figure)). Fibrocytes, adipocytes, and mesenchymal cells are stock-still cells, which ways they remain within the connective tissue. Other cells move in and out of the connective tissue in response to chemical signals. Macrophages, mast cells, lymphocytes, plasma cells, and phagocytic cells are found in connective tissue proper simply are actually function of the immune organisation protecting the body.

Connective Tissue Proper

Fibroblasts produce this fibrous tissue. Connective tissue proper includes the fixed cells fibrocytes, adipocytes, and mesenchymal cells. LM × 400. (Micrograph provided by the Regents of University of Michigan Medical Schoolhouse © 2012)

Jail cell Types

The about abundant cell in connective tissue proper is the fibroblast. Polysaccharides and proteins secreted by fibroblasts combine with actress-cellular fluids to produce a viscous footing substance that, with embedded fibrous proteins, forms the actress-cellular matrix. Every bit you might wait, a fibrocyte, a less active grade of fibroblast, is the 2d most common cell blazon in connective tissue proper.

Adipocytes are cells that store lipids as droplets that fill nigh of the cytoplasm. There are ii bones types of adipocytes: white and chocolate-brown. The dark-brown adipocytes store lipids as many droplets, and have high metabolic activeness. In contrast, white fat adipocytes store lipids as a single large driblet and are metabolically less active. Their effectiveness at storing big amounts of fatty is witnessed in obese individuals. The number and type of adipocytes depends on the tissue and location, and vary among individuals in the population.

The mesenchymal prison cell is a multipotent adult stalk cell. These cells tin can differentiate into any type of connective tissue cells needed for repair and healing of damaged tissue.

The macrophage cell is a large prison cell derived from a monocyte, a type of blood cell, which enters the connective tissue matrix from the blood vessels. The macrophage cells are an essential component of the immune system, which is the trunk's defence against potential pathogens and degraded host cells. When stimulated, macrophages release cytokines, small proteins that act equally chemical messengers. Cytokines recruit other cells of the immune arrangement to infected sites and stimulate their activities. Roaming, or gratis, macrophages motion rapidly past amoeboid movement, engulfing infectious agents and cellular droppings. In contrast, stock-still macrophages are permanent residents of their tissues.

The mast jail cell, establish in connective tissue proper, has many cytoplasmic granules. These granules contain the chemical signals histamine and heparin. When irritated or damaged, mast cells release histamine, an inflammatory mediator, which causes vasodilation and increased blood flow at a site of injury or infection, along with itching, swelling, and redness you recognize as an allergic response. Like blood cells, mast cells are derived from hematopoietic stem cells and are office of the immune organization.

Connective Tissue Fibers and Basis Substance

Three main types of fibers are secreted by fibroblasts: collagen fibers, elastic fibers, and reticular fibers. Collagen cobweb is made from fibrous protein subunits linked together to form a long and directly cobweb. Collagen fibers, while flexible, have great tensile strength, resist stretching, and give ligaments and tendons their characteristic resilience and force. These fibers concord connective tissues together, even during the movement of the body.

Elastic cobweb contains the protein elastin along with bottom amounts of other proteins and glycoproteins. The main property of elastin is that later on being stretched or compressed, it will return to its original shape. Rubberband fibers are prominent in rubberband tissues establish in pare and the elastic ligaments of the vertebral cavalcade.

Reticular fiber is also formed from the same poly peptide subunits equally collagen fibers; however, these fibers remain narrow and are arrayed in a branching network. They are found throughout the trunk, but are almost abundant in the reticular tissue of soft organs, such as liver and spleen, where they anchor and provide structural support to the parenchyma (the functional cells, blood vessels, and nerves of the organ).

All of these fiber types are embedded in ground substance. Secreted past fibroblasts, ground substance is made of polysaccharides, specifically hyaluronic acid, and proteins. These combine to form a proteoglycan with a protein cadre and polysaccharide branches. The proteoglycan attracts and traps bachelor moisture forming the articulate, pasty, colorless matrix you now know as ground substance.

Loose Connective Tissue

Loose connective tissue is found between many organs where it acts both to blot stupor and bind tissues together. It allows water, salts, and various nutrients to diffuse through to adjacent or imbedded cells and tissues.

Adipose tissue consists mostly of fat storage cells, with little extracellular matrix ((Effigy)). A big number of capillaries allow rapid storage and mobilization of lipid molecules. White adipose tissue is most abundant. It can announced yellow and owes its colour to carotene and related pigments from institute food. White fat contributes mostly to lipid storage and can serve as insulation from cold temperatures and mechanical injuries. White adipose tissue can be found protecting the kidneys and cushioning the dorsum of the heart. Brown adipose tissue is more common in infants, hence the term "baby fat." In adults, there is a reduced amount of brown fat and it is found mainly in the neck and clavicular regions of the trunk. The many mitochondria in the cytoplasm of brown adipose tissue help explain its efficiency at metabolizing stored fat. Brown adipose tissue is thermogenic, meaning that as information technology breaks down fats, it releases metabolic heat, rather than producing adenosine triphosphate (ATP), a primal molecule used in metabolism.

Adipose Tissue

This is a loose connective tissue that consists of fatty cells with little extracellular matrix. Information technology stores fat for free energy and provides insulation. LM × 800. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)

Areolar tissue shows little specialization. It contains all the cell types and fibers previously described and is distributed in a random, spider web-like fashion. Information technology fills the spaces betwixt muscle fibers, surrounds blood and lymph vessels, and supports organs in the abdominal crenel. Areolar tissue underlies about epithelia and represents the connective tissue component of epithelial membranes, which are described further in a later section.

Reticular tissue is a mesh-similar, supportive framework for soft organs such every bit lymphatic tissue, the spleen, and the liver ((Figure)). Reticular cells produce the reticular fibers that form the network onto which other cells attach. It derives its name from the Latin reticulus, which means "picayune net."

Reticular Tissue

This is a loose connective tissue fabricated up of a network of reticular fibers that provides a supportive framework for soft organs. LM × 1600. (Micrograph provided past the Regents of University of Michigan Medical School © 2012)

Dense Connective Tissue

Dense connective tissue contains more collagen fibers than does loose connective tissue. As a upshot, information technology displays greater resistance to stretching. There are two major categories of dense connective tissue: regular and irregular. Dense regular connective tissue fibers are parallel to each other, enhancing tensile forcefulness and resistance to stretching in the direction of the fiber orientations. Ligaments and tendons are made of dense regular connective tissue, but in ligaments not all fibers are parallel. Dense regular elastic tissue contains elastin fibers in add-on to collagen fibers, which allows the ligament to return to its original length after stretching. The ligaments in the vocal folds and betwixt the vertebrae in the vertebral column are rubberband.

In dense irregular connective tissue, the management of fibers is random. This system gives the tissue greater strength in all directions and less force in i item management. In some tissues, fibers crisscross and form a mesh. In other tissues, stretching in several directions is achieved by alternating layers where fibers run in the same orientation in each layer, and it is the layers themselves that are stacked at an angle. The dermis of the pare is an example of dense irregular connective tissue rich in collagen fibers. Dense irregular elastic tissues give arterial walls the strength and the ability to regain original shape afterwards stretching ((Effigy)).

Dense Connective Tissue

(a) Dense regular connective tissue consists of collagenous fibers packed into parallel bundles. (b) Dense irregular connective tissue consists of collagenous fibers interwoven into a mesh-like network. From top, LM × 1000, LM × 200. (Micrographs provided by the Regents of Academy of Michigan Medical School © 2012)

Disorders of the…

Connective Tissue: Tendinitis Your opponent stands fix equally you prepare to hit the serve, merely you lot are confident that you will boom the ball past your opponent. Equally you lot toss the ball high in the air, a burning hurting shoots beyond your wrist and you drop the tennis racket. That dull ache in the wrist that you ignored through the summer is now an unbearable pain. The game is over for now.

Later on examining your swollen wrist, the doctor in the emergency room announces that you have developed wrist tendinitis. She recommends icing the tender area, taking non-steroidal anti-inflammatory medication to ease the pain and to reduce swelling, and complete balance for a few weeks. She interrupts your protests that you cannot end playing. She issues a stern warning virtually the hazard of aggravating the status and the possibility of surgery. She consoles you past mentioning that well known tennis players such as Venus and Serena Williams and Rafael Nadal accept as well suffered from tendinitis related injuries.

What is tendinitis and how did it happen? Tendinitis is the inflammation of a tendon, the thick ring of fibrous connective tissue that attaches a muscle to a bone. The condition causes hurting and tenderness in the surface area around a joint. On rare occasions, a sudden serious injury will crusade tendinitis. Nearly often, the condition results from repetitive motions over time that strain the tendons needed to perform the tasks.

Persons whose jobs and hobbies involve performing the aforementioned movements over and again are often at the greatest risk of tendinitis. You hear of tennis and golfer'south elbow, jumper's knee, and swimmer'south shoulder. In all cases, overuse of the joint causes a microtrauma that initiates the inflammatory response. Tendinitis is routinely diagnosed through a clinical test. In case of astringent pain, 10-rays tin exist examined to rule out the possibility of a bone injury. Severe cases of tendinitis can even tear loose a tendon. Surgical repair of a tendon is painful. Connective tissue in the tendon does not take abundant blood supply and heals slowly.

While older adults are at hazard for tendinitis considering the elasticity of tendon tissue decreases with historic period, agile people of all ages can develop tendinitis. Young athletes, dancers, and figurer operators; anyone who performs the aforementioned movements constantly is at run a risk for tendinitis. Although repetitive motions are unavoidable in many activities and may lead to tendinitis, precautions can be taken that can lessen the probability of developing tendinitis. For active individuals, stretches earlier exercising and cross grooming or irresolute exercises are recommended. For the passionate athlete, information technology may be time to take some lessons to improve technique. All of the preventive measures aim to increase the forcefulness of the tendon and subtract the stress put on information technology. With proper rest and managed care, you will be back on the courtroom to hit that slice-spin serve over the net.

Watch this animation to larn more nearly tendonitis, a painful status caused by swollen or injured tendons.

Supportive Connective Tissues

Two major forms of supportive connective tissue, cartilage and os, allow the body to maintain its posture and protect internal organs.

Cartilage

The distinctive appearance of cartilage is due to polysaccharides chosen chondroitin sulfates, which bind with footing substance proteins to class proteoglycans. Embedded within the cartilage matrix are chondrocytes, or cartilage cells, and the space they occupy are called lacunae (singular = lacuna). A layer of dense irregular connective tissue, the perichondrium, encapsulates the cartilage. Cartilaginous tissue is avascular, thus all nutrients need to diffuse through the matrix to reach the chondrocytes. This is a gene contributing to the very slow healing of cartilaginous tissues.

The three principal types of cartilage tissue are hyaline cartilage, fibrocartilage, and elastic cartilage ((Figure)). Hyaline cartilage, the about mutual type of cartilage in the body, consists of short and dispersed collagen fibers and contains large amounts of proteoglycans. Nether the microscope, tissue samples appear articulate. The surface of hyaline cartilage is smoothen. Both strong and flexible, it is institute in the rib cage and olfactory organ and covers basic where they see to form moveable joints. It makes upwardly a template of the embryonic skeleton before bone formation. A plate of hyaline cartilage at the ends of bone allows connected growth until adulthood. Fibrocartilage is tough because it has thick bundles of collagen fibers dispersed through its matrix. Menisci in the knee articulation and the intervertebral discs are examples of fibrocartilage. Elastic cartilage contains rubberband fibers also equally collagen and proteoglycans. This tissue gives rigid support besides as elasticity. Tug gently at your ear lobes, and notice that the lobes return to their initial shape. The external ear contains elastic cartilage.

Types of Cartilage

Cartilage is a connective tissue consisting of collagenous fibers embedded in a firm matrix of chondroitin sulfates. (a) Hyaline cartilage provides support with some flexibility. The example is from dog tissue. (b) Fibrocartilage provides some compressibility and can absorb pressure. (c) Rubberband cartilage provides firm but elastic support. From top, LM × 300, LM × 1200, LM × 1016. (Micrographs provided past the Regents of University of Michigan Medical School © 2012)

Bone

Bone is the hardest connective tissue. It provides protection to internal organs and supports the torso. Bone'due south rigid extracellular matrix contains more often than not collagen fibers embedded in a mineralized ground substance containing hydroxyapatite, a form of calcium phosphate. Both components of the matrix, organic and inorganic, contribute to the unusual properties of bone. Without collagen, bones would be brittle and shatter easily. Without mineral crystals, bones would flex and provide little back up. Osteocytes, os cells like chondrocytes, are located within lacunae. The histology of transverse tissue from long bone shows a typical organization of osteocytes in concentric circles around a central canal. Os is a highly vascularized tissue. Unlike cartilage, bone tissue can recover from injuries in a relatively short time.

Cancellous bone looks like a sponge under the microscope and contains empty spaces between trabeculae, or arches of bone proper. Information technology is lighter than meaty os and found in the interior of some bones and at the terminate of long basic. Meaty os is solid and has greater structural strength.

Fluid Connective Tissue

Blood and lymph are fluid connective tissues. Cells circulate in a liquid extracellular matrix. The formed elements circulating in blood are all derived from hematopoietic stem cells located in bone marrow ((Figure)). Erythrocytes, ruby blood cells, send oxygen and some carbon dioxide. Leukocytes, white blood cells, are responsible for defending confronting potentially harmful microorganisms or molecules. Platelets are cell fragments involved in blood clotting. Some white blood cells take the power to cross the endothelial layer that lines blood vessels and enter adjacent tissues. Nutrients, salts, and wastes are dissolved in the liquid matrix and transported through the body.

Lymph contains a liquid matrix and white blood cells. Lymphatic capillaries are extremely permeable, assuasive larger molecules and excess fluid from interstitial spaces to enter the lymphatic vessels. Lymph drains into claret vessels, delivering molecules to the blood that could non otherwise direct enter the bloodstream. In this way, specialized lymphatic capillaries transport captivated fats abroad from the intestine and evangelize these molecules to the claret.

Blood: A Fluid Connective Tissue

Blood is a fluid connective tissue containing erythrocytes and various types of leukocytes that broadcast in a liquid extracellular matrix. LM × 1600. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)

Visit this link to exam your connective tissue knowledge with this 10-question quiz. Can you name the 10 tissue types shown in the histology slides?

Chapter Review

Connective tissue is a heterogeneous tissue with many cell shapes and tissue architecture. Structurally, all connective tissues contain cells that are embedded in an extracellular matrix stabilized past proteins. The chemical nature and physical layout of the extracellular matrix and proteins vary enormously amongst tissues, reflecting the multifariousness of functions that connective tissue fulfills in the torso. Connective tissues carve up and cushion organs, protecting them from shifting or traumatic injury. Connect tissues provide support and aid movement, shop and ship energy molecules, protect against infections, and contribute to temperature homeostasis.

Many different cells contribute to the formation of connective tissues. They originate in the mesodermal germ layer and differentiate from mesenchyme and hematopoietic tissue in the bone marrow. Fibroblasts are the almost abundant and secrete many protein fibers, adipocytes specialize in fat storage, hematopoietic cells from the bone marrow requite rise to all the claret cells, chondrocytes class cartilage, and osteocytes class bone. The extracellular matrix contains fluid, proteins, polysaccharide derivatives, and, in the case of os, mineral crystals. Poly peptide fibers fall into iii major groups: collagen fibers that are thick, strong, flexible, and resist stretch; reticular fibers that are sparse and form a supportive mesh; and elastin fibers that are thin and elastic.

The major types of connective tissue are connective tissue proper, supportive tissue, and fluid tissue. Loose connective tissue proper includes adipose tissue, areolar tissue, and reticular tissue. These serve to hold organs and other tissues in identify and, in the example of adipose tissue, isolate and store energy reserves. The matrix is the almost abundant feature for loose tissue although adipose tissue does non have much extracellular matrix. Dense connective tissue proper is richer in fibers and may be regular, with fibers oriented in parallel as in ligaments and tendons, or irregular, with fibers oriented in several directions. Organ capsules (collagenous blazon) and walls of arteries (elastic type) contain dense irregular connective tissue. Cartilage and bone are supportive tissue. Cartilage contains chondrocytes and is somewhat flexible. Hyaline cartilage is smooth and clear, covers joints, and is plant in the growing portion of bones. Fibrocartilage is tough because of extra collagen fibers and forms, among other things, the intervertebral discs. Rubberband cartilage can stretch and recoil to its original shape because of its high content of rubberband fibers. The matrix contains very few blood vessels. Bones are made of a rigid, mineralized matrix containing calcium salts, crystals, and osteocytes lodged in lacunae. Bone tissue is highly vascularized. Cancellous bone is spongy and less solid than compact bone. Fluid tissue, for instance blood and lymph, is characterized past a liquid matrix and no supporting fibers.

Interactive Link Questions

Visit this link to test your connective tissue knowledge with this ten-question quiz. Can you name the 10 tissue types shown in the histology slides?

Click at the bottom of the quiz for the answers.

Review Questions

Connective tissue is made of which three essential components?

1. cells, ground substance, and saccharide fibers
2. cells, footing substance, and protein fibers
3. collagen, ground substance, and protein fibers
4. matrix, ground substance, and fluid

Under the microscope, a tissue specimen shows cells located in spaces scattered in a transparent background. This is probably ________.

1. loose connective tissue
2. a tendon
3. bone
4. hyaline cartilage

Which connective tissue specializes in storage of fat?

1. tendon
2. adipose tissue
3. reticular tissue
4. dense connective tissue

Ligaments connect bones together and withstand a lot of stress. What blazon of connective tissue should you await ligaments to comprise?

1. areolar tissue
2. adipose tissue
3. dense regular connective tissue
4. dense irregular connective tissue

In adults, new connective tissue cells originate from the ________.

1. mesoderm
2. mesenchyme
3. ectoderm
4. endoderm

In bone, the main cells are ________.

1. fibroblasts
2. chondrocytes
3. lymphocytes
4. osteocytes

Critical Thinking Questions

One of the main functions of connective tissue is to integrate organs and organ systems in the body. Hash out how blood fulfills this role.

Claret is a fluid connective tissue, a variety of specialized cells that circulate in a watery fluid containing salts, nutrients, and dissolved proteins in a liquid extracellular matrix. Blood contains formed elements derived from bone marrow. Erythrocytes, or red blood cells, ship the gases oxygen and carbon dioxide. Leukocytes, or white blood cells, are responsible for the defense of the organism against potentially harmful microorganisms or molecules. Platelets are cell fragments involved in blood clotting. Some cells have the power to cross the endothelial layer that lines vessels and enter adjacent tissues. Nutrients, salts, and waste matter are dissolved in the liquid matrix and transported through the body.

Why does an injury to cartilage, especially hyaline cartilage, heal much more slowly than a bone fracture?

A layer of dense irregular connective tissue covers cartilage. No blood vessels supply cartilage tissue. Injuries to cartilage heal very slowly because cells and nutrients needed for repair diffuse slowly to the injury site.

Glossary

adipocytes

lipid storage cells

adipose tissue

specialized areolar tissue rich in stored fat

areolar tissue

(also, loose connective tissue) a type of connective tissue proper that shows fiddling specialization with cells dispersed in the matrix

chondrocytes

cells of the cartilage

collagen fiber

flexible fibrous proteins that give connective tissue tensile strength

connective tissue proper

connective tissue containing a viscous matrix, fibers, and cells.

dumbo connective tissue

connective tissue proper that contains many fibers that provide both elasticity and protection

elastic cartilage

type of cartilage, with elastin as the major poly peptide, characterized by rigid support as well as elasticity

rubberband fiber

fibrous protein within connective tissue that contains a loftier percentage of the poly peptide elastin that allows the fibers to stretch and return to original size

fibroblast

most abundant cell type in connective tissue, secretes protein fibers and matrix into the extracellular space

fibrocartilage

tough form of cartilage, fabricated of thick bundles of collagen fibers embedded in chondroitin sulfate basis substance

fibrocyte

less agile grade of fibroblast

fluid connective tissue

specialized cells that circulate in a watery fluid containing salts, nutrients, and dissolved proteins

ground substance

fluid or semi-fluid portion of the matrix

hyaline cartilage

well-nigh common type of cartilage, smooth and made of brusk collagen fibers embedded in a chondroitin sulfate ground substance

lacunae

(atypical = lacuna) minor spaces in os or cartilage tissue that cells occupy

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 past the cells embedded in it, containing ground substance and fibers

mesenchymal cell

developed stem cell from which most connective tissue cells are derived

mesenchyme

embryonic tissue from which connective tissue cells derive

mucous connective tissue

specialized loose connective tissue present in the umbilical cord

parenchyma

functional cells of a gland or organ, in contrast with the supportive or connective tissue of a gland or organ

reticular cobweb

fine fibrous protein, made of collagen subunits, which cross-link to form supporting "nets" inside connective tissue

reticular tissue

blazon of loose connective tissue that provides a supportive framework to soft organs, such as lymphatic tissue, spleen, and the liver

supportive connective tissue

type of connective tissue that provides strength to the torso and protects soft tissue

Source: https://opentextbc.ca/anatomyandphysiologyopenstax/chapter/connective-tissue-supports-and-protects/

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